# You should not have to change anything below this line
###############################################################################

# Object files for the SQLite library (non-amalgamation).
#
OBJS0 = alter.lo analyze.lo attach.lo auth.lo bitvec.lo btmutex.lo \
        btree.lo build.lo callback.lo complete.lo date.lo \
        delete.lo expr.lo fault.lo func.lo global.lo \
        hash.lo journal.lo insert.lo loadext.lo \
        main.lo malloc.lo mem1.lo mem2.lo mem3.lo mem4.lo mem5.lo mem6.lo \
        mutex.lo mutex_os2.lo mutex_unix.lo mutex_w32.lo \
        opcodes.lo os.lo os_unix.lo os_win.lo os_os2.lo \
        pager.lo parse.lo pragma.lo prepare.lo printf.lo random.lo \
        select.lo status.lo table.lo tokenize.lo trigger.lo update.lo \
        util.lo vacuum.lo \
        vdbe.lo vdbeapi.lo vdbeaux.lo vdbeblob.lo vdbefifo.lo vdbemem.lo \
        where.lo utf.lo legacy.lo vtab.lo

# Object files for the amalgamation.
#
................................................................................
  $(TOP)/src/build.c \
  $(TOP)/src/callback.c \
  $(TOP)/src/complete.c \
  $(TOP)/src/date.c \
  $(TOP)/src/delete.c \
  $(TOP)/src/expr.c \
  $(TOP)/src/fault.c \
  $(TOP)/src/func.c \
  $(TOP)/src/global.c \
  $(TOP)/src/hash.c \
  $(TOP)/src/hash.h \
  $(TOP)/src/hwtime.h \
  $(TOP)/src/insert.c \
  $(TOP)/src/journal.c \
  $(TOP)/src/legacy.c \
................................................................................
  $(TOP)/src/os_common.h \
  $(TOP)/src/os_unix.c \
  $(TOP)/src/os_win.c \
  $(TOP)/src/os_os2.c \
  $(TOP)/src/pager.c \
  $(TOP)/src/pager.h \
  $(TOP)/src/parse.y \


  $(TOP)/src/pragma.c \
  $(TOP)/src/prepare.c \
  $(TOP)/src/printf.c \
  $(TOP)/src/random.c \
  $(TOP)/src/select.c \
  $(TOP)/src/status.c \
  $(TOP)/src/shell.c \
................................................................................
  $(TOP)/src/vdbeInt.h \
  $(TOP)/src/vtab.c \
  $(TOP)/src/where.c

# Generated source code files
#
SRC += \

  keywordhash.h \
  opcodes.c \
  opcodes.h \
  parse.c \
  parse.h \
  config.h \
  sqlite3.h
................................................................................
  $(TOP)/src/insert.c \
  $(TOP)/src/malloc.c \
  $(TOP)/src/os.c \
  $(TOP)/src/os_os2.c \
  $(TOP)/src/os_unix.c \
  $(TOP)/src/os_win.c \
  $(TOP)/src/pager.c \

  $(TOP)/src/pragma.c \
  $(TOP)/src/prepare.c \
  $(TOP)/src/printf.c \
  $(TOP)/src/random.c \
  $(TOP)/src/select.c \
  $(TOP)/src/tokenize.c \
  $(TOP)/src/utf.c \
................................................................................

expr.lo:	$(TOP)/src/expr.c $(HDR)
	$(LTCOMPILE) -c $(TOP)/src/expr.c

fault.lo:	$(TOP)/src/fault.c $(HDR)
	$(LTCOMPILE) -c $(TOP)/src/fault.c

func.lo:	$(TOP)/src/func.c $(HDR)
	$(LTCOMPILE) -c $(TOP)/src/func.c

global.lo:	$(TOP)/src/global.c $(HDR)
	$(LTCOMPILE) -c $(TOP)/src/global.c

hash.lo:	$(TOP)/src/hash.c $(HDR)
	$(LTCOMPILE) -c $(TOP)/src/hash.c

................................................................................

mutex_w32.lo:	$(TOP)/src/mutex_w32.c $(HDR)
	$(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/mutex_w32.c

pager.lo:	$(TOP)/src/pager.c $(HDR) $(TOP)/src/pager.h
	$(LTCOMPILE) -c $(TOP)/src/pager.c




opcodes.lo:	opcodes.c
	$(LTCOMPILE) -c opcodes.c

opcodes.c:	opcodes.h $(TOP)/mkopcodec.awk
	sort -n -b -k 3 opcodes.h | $(NAWK) -f $(TOP)/mkopcodec.awk >opcodes.c

opcodes.h:	parse.h $(TOP)/src/vdbe.c $(TOP)/mkopcodeh.awk
................................................................................
parse.h:	parse.c

parse.c:	$(TOP)/src/parse.y lemon$(BEXE) $(TOP)/addopcodes.awk
	cp $(TOP)/src/parse.y .
	./lemon$(BEXE) $(OPTS) $(OPT_FEATURE_FLAGS) parse.y
	mv parse.h parse.h.temp
	$(NAWK) -f $(TOP)/addopcodes.awk parse.h.temp >parse.h






pragma.lo:	$(TOP)/src/pragma.c $(HDR)
	$(LTCOMPILE) -c $(TOP)/src/pragma.c

prepare.lo:	$(TOP)/src/prepare.c $(HDR)
	$(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/prepare.c

# You should not have to change anything below this line
###############################################################################

# Object files for the SQLite library (non-amalgamation).
#
OBJS0 = alter.lo analyze.lo attach.lo auth.lo bitvec.lo btmutex.lo \
        btree.lo build.lo callback.lo complete.lo date.lo \
        delete.lo expr.lo fault.lo func2.lo global.lo \
        hash.lo journal.lo insert.lo loadext.lo \
        main.lo malloc.lo mem1.lo mem2.lo mem3.lo mem4.lo mem5.lo mem6.lo \
        mutex.lo mutex_os2.lo mutex_unix.lo mutex_w32.lo \
        opcodes.lo os.lo os_unix.lo os_win.lo os_os2.lo \
        pager.lo parse.lo pcache.lo pragma.lo prepare.lo printf.lo random.lo \
        select.lo status.lo table.lo tokenize.lo trigger.lo update.lo \
        util.lo vacuum.lo \
        vdbe.lo vdbeapi.lo vdbeaux.lo vdbeblob.lo vdbefifo.lo vdbemem.lo \
        where.lo utf.lo legacy.lo vtab.lo

# Object files for the amalgamation.
#
................................................................................
  $(TOP)/src/build.c \
  $(TOP)/src/callback.c \
  $(TOP)/src/complete.c \
  $(TOP)/src/date.c \
  $(TOP)/src/delete.c \
  $(TOP)/src/expr.c \
  $(TOP)/src/fault.c \

  $(TOP)/src/global.c \
  $(TOP)/src/hash.c \
  $(TOP)/src/hash.h \
  $(TOP)/src/hwtime.h \
  $(TOP)/src/insert.c \
  $(TOP)/src/journal.c \
  $(TOP)/src/legacy.c \
................................................................................
  $(TOP)/src/os_common.h \
  $(TOP)/src/os_unix.c \
  $(TOP)/src/os_win.c \
  $(TOP)/src/os_os2.c \
  $(TOP)/src/pager.c \
  $(TOP)/src/pager.h \
  $(TOP)/src/parse.y \
  $(TOP)/src/pcache.c \
  $(TOP)/src/pcache.h \
  $(TOP)/src/pragma.c \
  $(TOP)/src/prepare.c \
  $(TOP)/src/printf.c \
  $(TOP)/src/random.c \
  $(TOP)/src/select.c \
  $(TOP)/src/status.c \
  $(TOP)/src/shell.c \
................................................................................
  $(TOP)/src/vdbeInt.h \
  $(TOP)/src/vtab.c \
  $(TOP)/src/where.c

# Generated source code files
#
SRC += \
  func2.c \
  keywordhash.h \
  opcodes.c \
  opcodes.h \
  parse.c \
  parse.h \
  config.h \
  sqlite3.h
................................................................................
  $(TOP)/src/insert.c \
  $(TOP)/src/malloc.c \
  $(TOP)/src/os.c \
  $(TOP)/src/os_os2.c \
  $(TOP)/src/os_unix.c \
  $(TOP)/src/os_win.c \
  $(TOP)/src/pager.c \
  $(TOP)/src/pcache.c \
  $(TOP)/src/pragma.c \
  $(TOP)/src/prepare.c \
  $(TOP)/src/printf.c \
  $(TOP)/src/random.c \
  $(TOP)/src/select.c \
  $(TOP)/src/tokenize.c \
  $(TOP)/src/utf.c \
................................................................................

expr.lo:	$(TOP)/src/expr.c $(HDR)
	$(LTCOMPILE) -c $(TOP)/src/expr.c

fault.lo:	$(TOP)/src/fault.c $(HDR)
	$(LTCOMPILE) -c $(TOP)/src/fault.c

func2.lo:	func2.c $(HDR)
	$(LTCOMPILE) -c func2.c

global.lo:	$(TOP)/src/global.c $(HDR)
	$(LTCOMPILE) -c $(TOP)/src/global.c

hash.lo:	$(TOP)/src/hash.c $(HDR)
	$(LTCOMPILE) -c $(TOP)/src/hash.c

................................................................................

mutex_w32.lo:	$(TOP)/src/mutex_w32.c $(HDR)
	$(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/mutex_w32.c

pager.lo:	$(TOP)/src/pager.c $(HDR) $(TOP)/src/pager.h
	$(LTCOMPILE) -c $(TOP)/src/pager.c

pcache.lo:	$(TOP)/src/pcache.c $(HDR) $(TOP)/src/pcache.h
	$(LTCOMPILE) -c $(TOP)/src/pcache.c

opcodes.lo:	opcodes.c
	$(LTCOMPILE) -c opcodes.c

opcodes.c:	opcodes.h $(TOP)/mkopcodec.awk
	sort -n -b -k 3 opcodes.h | $(NAWK) -f $(TOP)/mkopcodec.awk >opcodes.c

opcodes.h:	parse.h $(TOP)/src/vdbe.c $(TOP)/mkopcodeh.awk
................................................................................
parse.h:	parse.c

parse.c:	$(TOP)/src/parse.y lemon$(BEXE) $(TOP)/addopcodes.awk
	cp $(TOP)/src/parse.y .
	./lemon$(BEXE) $(OPTS) $(OPT_FEATURE_FLAGS) parse.y
	mv parse.h parse.h.temp
	$(NAWK) -f $(TOP)/addopcodes.awk parse.h.temp >parse.h

func2.c: $(TOP)/src/func.c $(HDR)
	$(BCC) -o mkfunction$(BEXE) $(OPTS) $(TOP)/tool/mkfunction.c -I$(TOP)/src -I.
	cat $(TOP)/src/func.c > func2.c
	./mkfunction$(BEXE) >> func2.c

pragma.lo:	$(TOP)/src/pragma.c $(HDR)
	$(LTCOMPILE) -c $(TOP)/src/pragma.c

prepare.lo:	$(TOP)/src/prepare.c $(HDR)
	$(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/prepare.c

#
TCCX = $(TCC) $(OPTS) -I. -I$(TOP)/src -I$(TOP) -I$(TOP)/ext/rtree

# Object files for the SQLite library.
#
LIBOBJ+= alter.o analyze.o attach.o auth.o bitvec.o btmutex.o btree.o build.o \
         callback.o complete.o date.o delete.o \
         expr.o fault.o func.o global.o hash.o insert.o journal.o loadext.o \
         main.o malloc.o mem1.o mem2.o mem3.o mem4.o mem5.o mem6.o \
         mutex.o mutex_os2.o mutex_unix.o mutex_w32.o \
         opcodes.o os.o os_os2.o os_unix.o os_win.o \
         pager.o parse.o pragma.o prepare.o printf.o random.o \
         select.o status.o table.o $(TCLOBJ) tokenize.o trigger.o \
         update.o util.o vacuum.o \
         vdbe.o vdbeapi.o vdbeaux.o vdbeblob.o vdbefifo.o vdbemem.o \
         where.o utf.o legacy.o vtab.o rtree.o icu.o

EXTOBJ = icu.o
EXTOBJ += fts1.o \
	  fts1_hash.o \
	  fts1_tokenizer1.o \
	  fts1_porter.o
EXTOBJ += fts2.o \
................................................................................
  $(TOP)/src/build.c \
  $(TOP)/src/callback.c \
  $(TOP)/src/complete.c \
  $(TOP)/src/date.c \
  $(TOP)/src/delete.c \
  $(TOP)/src/expr.c \
  $(TOP)/src/fault.c \
  $(TOP)/src/func.c \
  $(TOP)/src/global.c \
  $(TOP)/src/hash.c \
  $(TOP)/src/hash.h \
  $(TOP)/src/hwtime.h \
  $(TOP)/src/insert.c \
  $(TOP)/src/journal.c \
  $(TOP)/src/legacy.c \
................................................................................
  $(TOP)/src/vdbe.c \
  $(TOP)/src/vdbe.h \
  $(TOP)/src/vdbeapi.c \
  $(TOP)/src/vdbeaux.c \
  $(TOP)/src/vdbeblob.c \
  $(TOP)/src/vdbefifo.c \
  $(TOP)/src/vdbemem.c \

  $(TOP)/src/vdbeInt.h \
  $(TOP)/src/vtab.c \
  $(TOP)/src/where.c

# Source code for extensions
#
SRC += \
................................................................................
#
SRC += \
  keywordhash.h \
  opcodes.c \
  opcodes.h \
  parse.c \
  parse.h \

  sqlite3.h


# Source code to the test files.
#
TESTSRC = \
  $(TOP)/src/test1.c \
................................................................................
  $(TOP)/src/test_thread.c \

#TESTSRC += $(TOP)/ext/fts2/fts2_tokenizer.c
#TESTSRC += $(TOP)/ext/fts3/fts3_tokenizer.c

TESTSRC2 = \
  $(TOP)/src/attach.c $(TOP)/src/btree.c $(TOP)/src/build.c $(TOP)/src/date.c  \
  $(TOP)/src/expr.c $(TOP)/src/func.c $(TOP)/src/insert.c $(TOP)/src/os.c      \
  $(TOP)/src/os_os2.c $(TOP)/src/os_unix.c $(TOP)/src/os_win.c                 \
  $(TOP)/src/pager.c $(TOP)/src/pragma.c $(TOP)/src/prepare.c                  \
  $(TOP)/src/printf.c $(TOP)/src/random.c                                      \
  $(TOP)/src/select.c $(TOP)/src/tokenize.c                                    \
  $(TOP)/src/utf.c $(TOP)/src/util.c $(TOP)/src/vdbeapi.c $(TOP)/src/vdbeaux.c \
  $(TOP)/src/vdbe.c $(TOP)/src/vdbemem.c $(TOP)/src/where.c parse.c

# Header files used by all library source files.
#
HDR = \
................................................................................
   $(TOP)/src/hwtime.h \
   keywordhash.h \
   $(TOP)/src/mutex.h \
   opcodes.h \
   $(TOP)/src/os.h \
   $(TOP)/src/os_common.h \
   $(TOP)/src/pager.h \

   parse.h  \
   sqlite3.h  \
   $(TOP)/src/sqlite3ext.h \
   $(TOP)/src/sqliteInt.h  \
   $(TOP)/src/sqliteLimit.h \
   $(TOP)/src/vdbe.h \
   $(TOP)/src/vdbeInt.h
................................................................................
#
opcodes.c:	opcodes.h $(TOP)/mkopcodec.awk
	sort -n -b -k 3 opcodes.h | $(NAWK) -f $(TOP)/mkopcodec.awk >opcodes.c

opcodes.h:	parse.h $(TOP)/src/vdbe.c $(TOP)/mkopcodeh.awk
	cat parse.h $(TOP)/src/vdbe.c |$(NAWK) -f $(TOP)/mkopcodeh.awk >opcodes.h






# Rules to build parse.c and parse.h - the outputs of lemon.
#
parse.h:	parse.c

parse.c:	$(TOP)/src/parse.y lemon $(TOP)/addopcodes.awk
	cp $(TOP)/src/parse.y .
................................................................................
clean:	
	rm -f *.o sqlite3 libsqlite3.a sqlite3.h opcodes.*
	rm -f lemon lempar.c parse.* sqlite*.tar.gz mkkeywordhash keywordhash.h
	rm -f $(PUBLISH)
	rm -f *.da *.bb *.bbg gmon.out
	rm -rf tsrc target_source
	rm -f testloadext.dll libtestloadext.so
	rm -f sqlite3.c fts?amal.c

#
TCCX = $(TCC) $(OPTS) -I. -I$(TOP)/src -I$(TOP) -I$(TOP)/ext/rtree

# Object files for the SQLite library.
#
LIBOBJ+= alter.o analyze.o attach.o auth.o bitvec.o btmutex.o btree.o build.o \
         callback.o complete.o date.o delete.o \
         expr.o fault.o func2.o global.o hash.o insert.o journal.o loadext.o \
         main.o malloc.o mem1.o mem2.o mem3.o mem4.o mem5.o mem6.o \
         mutex.o mutex_os2.o mutex_unix.o mutex_w32.o \
         opcodes.o os.o os_os2.o os_unix.o os_win.o \
         pager.o parse.o pragma.o prepare.o printf.o random.o \
         select.o status.o table.o $(TCLOBJ) tokenize.o trigger.o \
         update.o util.o vacuum.o \
         vdbe.o vdbeapi.o vdbeaux.o vdbeblob.o vdbefifo.o vdbemem.o \
         where.o utf.o legacy.o vtab.o rtree.o icu.o pcache.o

EXTOBJ = icu.o
EXTOBJ += fts1.o \
	  fts1_hash.o \
	  fts1_tokenizer1.o \
	  fts1_porter.o
EXTOBJ += fts2.o \
................................................................................
  $(TOP)/src/build.c \
  $(TOP)/src/callback.c \
  $(TOP)/src/complete.c \
  $(TOP)/src/date.c \
  $(TOP)/src/delete.c \
  $(TOP)/src/expr.c \
  $(TOP)/src/fault.c \

  $(TOP)/src/global.c \
  $(TOP)/src/hash.c \
  $(TOP)/src/hash.h \
  $(TOP)/src/hwtime.h \
  $(TOP)/src/insert.c \
  $(TOP)/src/journal.c \
  $(TOP)/src/legacy.c \
................................................................................
  $(TOP)/src/vdbe.c \
  $(TOP)/src/vdbe.h \
  $(TOP)/src/vdbeapi.c \
  $(TOP)/src/vdbeaux.c \
  $(TOP)/src/vdbeblob.c \
  $(TOP)/src/vdbefifo.c \
  $(TOP)/src/vdbemem.c \
  $(TOP)/src/pcache.c \
  $(TOP)/src/vdbeInt.h \
  $(TOP)/src/vtab.c \
  $(TOP)/src/where.c

# Source code for extensions
#
SRC += \
................................................................................
#
SRC += \
  keywordhash.h \
  opcodes.c \
  opcodes.h \
  parse.c \
  parse.h \
  func2.c \
  sqlite3.h


# Source code to the test files.
#
TESTSRC = \
  $(TOP)/src/test1.c \
................................................................................
  $(TOP)/src/test_thread.c \

#TESTSRC += $(TOP)/ext/fts2/fts2_tokenizer.c
#TESTSRC += $(TOP)/ext/fts3/fts3_tokenizer.c

TESTSRC2 = \
  $(TOP)/src/attach.c $(TOP)/src/btree.c $(TOP)/src/build.c $(TOP)/src/date.c  \
  $(TOP)/src/expr.c func2.c $(TOP)/src/insert.c $(TOP)/src/os.c      \
  $(TOP)/src/os_os2.c $(TOP)/src/os_unix.c $(TOP)/src/os_win.c                 \
  $(TOP)/src/pager.c $(TOP)/src/pragma.c $(TOP)/src/prepare.c                  \
  $(TOP)/src/printf.c $(TOP)/src/random.c $(TOP)/src/pcache.c                  \
  $(TOP)/src/select.c $(TOP)/src/tokenize.c                                    \
  $(TOP)/src/utf.c $(TOP)/src/util.c $(TOP)/src/vdbeapi.c $(TOP)/src/vdbeaux.c \
  $(TOP)/src/vdbe.c $(TOP)/src/vdbemem.c $(TOP)/src/where.c parse.c

# Header files used by all library source files.
#
HDR = \
................................................................................
   $(TOP)/src/hwtime.h \
   keywordhash.h \
   $(TOP)/src/mutex.h \
   opcodes.h \
   $(TOP)/src/os.h \
   $(TOP)/src/os_common.h \
   $(TOP)/src/pager.h \
   $(TOP)/src/pcache.h \
   parse.h  \
   sqlite3.h  \
   $(TOP)/src/sqlite3ext.h \
   $(TOP)/src/sqliteInt.h  \
   $(TOP)/src/sqliteLimit.h \
   $(TOP)/src/vdbe.h \
   $(TOP)/src/vdbeInt.h
................................................................................
#
opcodes.c:	opcodes.h $(TOP)/mkopcodec.awk
	sort -n -b -k 3 opcodes.h | $(NAWK) -f $(TOP)/mkopcodec.awk >opcodes.c

opcodes.h:	parse.h $(TOP)/src/vdbe.c $(TOP)/mkopcodeh.awk
	cat parse.h $(TOP)/src/vdbe.c |$(NAWK) -f $(TOP)/mkopcodeh.awk >opcodes.h

func2.c: $(TOP)/src/func.c $(HDR)
	$(BCC) -o mkfunction $(OPTS) $(TOP)/tool/mkfunction.c -I$(TOP)/src -I.
	cat $(TOP)/src/func.c > func2.c
	./mkfunction >> func2.c

# Rules to build parse.c and parse.h - the outputs of lemon.
#
parse.h:	parse.c

parse.c:	$(TOP)/src/parse.y lemon $(TOP)/addopcodes.awk
	cp $(TOP)/src/parse.y .
................................................................................
clean:	
	rm -f *.o sqlite3 libsqlite3.a sqlite3.h opcodes.*
	rm -f lemon lempar.c parse.* sqlite*.tar.gz mkkeywordhash keywordhash.h
	rm -f $(PUBLISH)
	rm -f *.da *.bb *.bbg gmon.out
	rm -rf tsrc target_source
	rm -f testloadext.dll libtestloadext.so
	rm -f sqlite3.c fts?amal.c tclsqlite3.c func2.c

** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.497 2008/08/13 19:11:48 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"

................................................................................
}

/*
** This routine is called when the reference count for a page
** reaches zero.  We need to unref the pParent pointer when that
** happens.
*/
static void pageDestructor(DbPage *pData, int pageSize){
  MemPage *pPage;
  assert( (pageSize & 7)==0 );
  pPage = (MemPage *)sqlite3PagerGetExtra(pData);

  assert( pPage->isInit==0 || sqlite3_mutex_held(pPage->pBt->mutex) );
  if( pPage->pParent ){
    MemPage *pParent = pPage->pParent;
    assert( pParent->pBt==pPage->pBt );
    pPage->pParent = 0;
    releasePage(pParent);
  }
  pPage->isInit = 0;

}

/*
** During a rollback, when the pager reloads information into the cache
** so that the cache is restored to its original state at the start of
** the transaction, for each page restored this routine is called.
**
................................................................................
    pBt = sqlite3MallocZero( sizeof(*pBt) );
    if( pBt==0 ){
      rc = SQLITE_NOMEM;
      goto btree_open_out;
    }
    pBt->busyHdr.xFunc = sqlite3BtreeInvokeBusyHandler;
    pBt->busyHdr.pArg = pBt;
    rc = sqlite3PagerOpen(pVfs, &pBt->pPager, zFilename,
                          EXTRA_SIZE, flags, vfsFlags);
    if( rc==SQLITE_OK ){
      rc = sqlite3PagerReadFileheader(pBt->pPager,sizeof(zDbHeader),zDbHeader);
    }
    if( rc!=SQLITE_OK ){
      goto btree_open_out;
    }
    sqlite3PagerSetBusyhandler(pBt->pPager, &pBt->busyHdr);
    p->pBt = pBt;
  
    sqlite3PagerSetDestructor(pBt->pPager, pageDestructor);
    sqlite3PagerSetReiniter(pBt->pPager, pageReinit);
    pBt->pCursor = 0;
    pBt->pPage1 = 0;
    pBt->readOnly = sqlite3PagerIsreadonly(pBt->pPager);
    pBt->pageSize = get2byte(&zDbHeader[16]);
    if( pBt->pageSize<512 || pBt->pageSize>SQLITE_MAX_PAGE_SIZE
         || ((pBt->pageSize-1)&pBt->pageSize)!=0 ){
................................................................................
  assert( cursorHoldsMutex(pCur) );
  assert( pCur->eState==CURSOR_VALID );
  pPage = pCur->pPage;
  assert( pPage!=0 );
  assert( !sqlite3BtreeIsRootPage(pPage) );
  pParent = pPage->pParent;
  assert( pParent!=0 );

  idxParent = pPage->idxParent;
  sqlite3PagerRef(pParent->pDbPage);
  releasePage(pPage);
  pCur->pPage = pParent;
  pCur->info.nSize = 0;
  pCur->validNKey = 0;
  assert( pParent->idxShift==0 );

** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.498 2008/08/20 14:49:24 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"

................................................................................
}

/*
** This routine is called when the reference count for a page
** reaches zero.  We need to unref the pParent pointer when that
** happens.
*/
static void pageDestructor(DbPage *pData){
  MemPage *pPage;

  pPage = (MemPage *)sqlite3PagerGetExtra(pData);
  if( pPage ){
    assert( pPage->isInit==0 || sqlite3_mutex_held(pPage->pBt->mutex) );
    if( pPage->pParent ){
      MemPage *pParent = pPage->pParent;
      assert( pParent->pBt==pPage->pBt );
      pPage->pParent = 0;
      releasePage(pParent);
    }
    pPage->isInit = 0;
  }
}

/*
** During a rollback, when the pager reloads information into the cache
** so that the cache is restored to its original state at the start of
** the transaction, for each page restored this routine is called.
**
................................................................................
    pBt = sqlite3MallocZero( sizeof(*pBt) );
    if( pBt==0 ){
      rc = SQLITE_NOMEM;
      goto btree_open_out;
    }
    pBt->busyHdr.xFunc = sqlite3BtreeInvokeBusyHandler;
    pBt->busyHdr.pArg = pBt;
    rc = sqlite3PagerOpen(pVfs, &pBt->pPager, zFilename, pageDestructor,
                          EXTRA_SIZE, flags, vfsFlags);
    if( rc==SQLITE_OK ){
      rc = sqlite3PagerReadFileheader(pBt->pPager,sizeof(zDbHeader),zDbHeader);
    }
    if( rc!=SQLITE_OK ){
      goto btree_open_out;
    }
    sqlite3PagerSetBusyhandler(pBt->pPager, &pBt->busyHdr);
    p->pBt = pBt;
  
    /* sqlite3PagerSetDestructor(pBt->pPager, pageDestructor); */
    sqlite3PagerSetReiniter(pBt->pPager, pageReinit);
    pBt->pCursor = 0;
    pBt->pPage1 = 0;
    pBt->readOnly = sqlite3PagerIsreadonly(pBt->pPager);
    pBt->pageSize = get2byte(&zDbHeader[16]);
    if( pBt->pageSize<512 || pBt->pageSize>SQLITE_MAX_PAGE_SIZE
         || ((pBt->pageSize-1)&pBt->pageSize)!=0 ){
................................................................................
  assert( cursorHoldsMutex(pCur) );
  assert( pCur->eState==CURSOR_VALID );
  pPage = pCur->pPage;
  assert( pPage!=0 );
  assert( !sqlite3BtreeIsRootPage(pPage) );
  pParent = pPage->pParent;
  assert( pParent!=0 );
  assert( pPage->pDbPage->nRef>0 );
  idxParent = pPage->idxParent;
  sqlite3PagerRef(pParent->pDbPage);
  releasePage(pPage);
  pCur->pPage = pParent;
  pCur->info.nSize = 0;
  pCur->validNKey = 0;
  assert( pParent->idxShift==0 );

**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file contains functions used to access the internal hash tables
** of user defined functions and collation sequences.
**
** $Id: callback.c,v 1.26 2008/07/28 19:34:53 drh Exp $
*/

#include "sqliteInt.h"

/*
** Invoke the 'collation needed' callback to request a collation sequence
** in the database text encoding of name zName, length nName.
................................................................................
    pColl = db->pDfltColl;
  }
  assert( SQLITE_UTF8==1 && SQLITE_UTF16LE==2 && SQLITE_UTF16BE==3 );
  assert( enc>=SQLITE_UTF8 && enc<=SQLITE_UTF16BE );
  if( pColl ) pColl += enc-1;
  return pColl;
}







































/*
** Locate a user function given a name, a number of arguments and a flag
** indicating whether the function prefers UTF-16 over UTF-8.  Return a
** pointer to the FuncDef structure that defines that function, or return
** NULL if the function does not exist.
**
................................................................................


  assert( enc==SQLITE_UTF8 || enc==SQLITE_UTF16LE || enc==SQLITE_UTF16BE );
  if( nArg<-1 ) nArg = -1;

  pFirst = (FuncDef*)sqlite3HashFind(&db->aFunc, zName, nName);
  for(p=pFirst; p; p=p->pNext){
    /* During the search for the best function definition, bestmatch is set
    ** as follows to indicate the quality of the match with the definition
    ** pointed to by pBest:
    **
    ** 0: pBest is NULL. No match has been found.
    ** 1: A variable arguments function that prefers UTF-8 when a UTF-16
    **    encoding is requested, or vice versa.
    ** 2: A variable arguments function that uses UTF-16BE when UTF-16LE is
    **    requested, or vice versa.
    ** 3: A variable arguments function using the same text encoding.
    ** 4: A function with the exact number of arguments requested that
    **    prefers UTF-8 when a UTF-16 encoding is requested, or vice versa.
    ** 5: A function with the exact number of arguments requested that
    **    prefers UTF-16LE when UTF-16BE is requested, or vice versa.
    ** 6: An exact match.
    **
    ** A larger value of 'matchqual' indicates a more desirable match.
    */
    if( p->nArg==-1 || p->nArg==nArg || nArg==-1 ){
      int match = 1;          /* Quality of this match */
      if( p->nArg==nArg || nArg==-1 ){
        match = 4;
      }
      if( enc==p->iPrefEnc ){
        match += 2;
      }
      else if( (enc==SQLITE_UTF16LE && p->iPrefEnc==SQLITE_UTF16BE) ||
               (enc==SQLITE_UTF16BE && p->iPrefEnc==SQLITE_UTF16LE) ){
        match += 1;
      }












      if( match>bestmatch ){
        pBest = p;
        bestmatch = match;
      }
    }
  }

  /* If the createFlag parameter is true, and the seach did not reveal an
  ** exact match for the name, number of arguments and encoding, then add a
  ** new entry to the hash table and return it.
  */
  if( createFlag && bestmatch<6 && 
      (pBest = sqlite3DbMallocZero(db, sizeof(*pBest)+nName))!=0 ){

    pBest->nArg = nArg;
    pBest->pNext = pFirst;
    pBest->iPrefEnc = enc;
    memcpy(pBest->zName, zName, nName);
    pBest->zName[nName] = 0;
    if( pBest==sqlite3HashInsert(&db->aFunc,pBest->zName,nName,(void*)pBest) ){
      db->mallocFailed = 1;

**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file contains functions used to access the internal hash tables
** of user defined functions and collation sequences.
**
** $Id: callback.c,v 1.27 2008/08/20 14:49:24 danielk1977 Exp $
*/

#include "sqliteInt.h"

/*
** Invoke the 'collation needed' callback to request a collation sequence
** in the database text encoding of name zName, length nName.
................................................................................
    pColl = db->pDfltColl;
  }
  assert( SQLITE_UTF8==1 && SQLITE_UTF16LE==2 && SQLITE_UTF16BE==3 );
  assert( enc>=SQLITE_UTF8 && enc<=SQLITE_UTF16BE );
  if( pColl ) pColl += enc-1;
  return pColl;
}

/* During the search for the best function definition, this procedure
** is called to test how well the function passed as the first argument
** matches the request for a function with nArg arguments in a system
** that uses encoding enc. The value returned indicates how well the
** request is matched. A higher value indicates a better match.
**
** The returned value is always between 1 and 6, as follows:
**
** 1: A variable arguments function that prefers UTF-8 when a UTF-16
**    encoding is requested, or vice versa.
** 2: A variable arguments function that uses UTF-16BE when UTF-16LE is
**    requested, or vice versa.
** 3: A variable arguments function using the same text encoding.
** 4: A function with the exact number of arguments requested that
**    prefers UTF-8 when a UTF-16 encoding is requested, or vice versa.
** 5: A function with the exact number of arguments requested that
**    prefers UTF-16LE when UTF-16BE is requested, or vice versa.
** 6: An exact match.
**
*/
static int matchQuality(FuncDef *p, int nArg, u8 enc){
  int match = 0;
  if( p->nArg==-1 || p->nArg==nArg || nArg==-1 ){
    match = 1;
    if( p->nArg==nArg || nArg==-1 ){
      match = 4;
    }
    if( enc==p->iPrefEnc ){
      match += 2;
    }
    else if( (enc==SQLITE_UTF16LE && p->iPrefEnc==SQLITE_UTF16BE) ||
             (enc==SQLITE_UTF16BE && p->iPrefEnc==SQLITE_UTF16LE) ){
      match += 1;
    }
  }
  return match;
}

/*
** Locate a user function given a name, a number of arguments and a flag
** indicating whether the function prefers UTF-16 over UTF-8.  Return a
** pointer to the FuncDef structure that defines that function, or return
** NULL if the function does not exist.
**
................................................................................


  assert( enc==SQLITE_UTF8 || enc==SQLITE_UTF16LE || enc==SQLITE_UTF16BE );
  if( nArg<-1 ) nArg = -1;

  pFirst = (FuncDef*)sqlite3HashFind(&db->aFunc, zName, nName);
  for(p=pFirst; p; p=p->pNext){
    int match = matchQuality(p, nArg, enc);
    if( match>bestmatch ){
      pBest = p;


















      bestmatch = match;
    }


  }





  /* If the createFlag parameter is false and no match was found amongst
  ** the custom functions stored in sqlite3.aFunc, try to find a built-in
  ** function to use.
  */ 
  if( !createFlag && !pBest ){
    FuncDef *aFunc;
    int nFunc;
    int i;
    nFunc = sqlite3GetBuiltinFunction(zName, nName, &aFunc);
    for(i=0; i<nFunc; i++){
      int match = matchQuality(&aFunc[i], nArg, enc);
      if( match>bestmatch ){
        pBest = &aFunc[i];
        bestmatch = match;
      }
    }
  }

  /* If the createFlag parameter is true, and the seach did not reveal an
  ** exact match for the name, number of arguments and encoding, then add a
  ** new entry to the hash table and return it.
  */
  if( createFlag && bestmatch<6 && 
      (pBest = sqlite3DbMallocZero(db, sizeof(*pBest)+nName+1))!=0 ){
    pBest->zName = (char *)&pBest[1];
    pBest->nArg = nArg;
    pBest->pNext = pFirst;
    pBest->iPrefEnc = enc;
    memcpy(pBest->zName, zName, nName);
    pBest->zName[nName] = 0;
    if( pBest==sqlite3HashInsert(&db->aFunc,pBest->zName,nName,(void*)pBest) ){
      db->mallocFailed = 1;

** This file contains the C functions that implement various SQL
** functions of SQLite.  
**
** There is only one exported symbol in this file - the function
** sqliteRegisterBuildinFunctions() found at the bottom of the file.
** All other code has file scope.
**
** $Id: func.c,v 1.196 2008/07/28 19:34:53 drh Exp $
*/



#include "sqliteInt.h"
#include <ctype.h>
#include <stdlib.h>
#include <assert.h>
#include "vdbeInt.h"


/*
** Return the collating function associated with a function.
*/
static CollSeq *sqlite3GetFuncCollSeq(sqlite3_context *context){
  return context->pColl;
}
................................................................................

/*
** This function registered all of the above C functions as SQL
** functions.  This should be the only routine in this file with
** external linkage.
*/
void sqlite3RegisterBuiltinFunctions(sqlite3 *db){
  static const struct {
     char *zName;
     signed char nArg;
     u8 argType;           /* 1: 0, 2: 1, 3: 2,...  N:  N-1. */
     u8 eTextRep;          /* 1: UTF-16.  0: UTF-8 */
     u8 needCollSeq;
     void (*xFunc)(sqlite3_context*,int,sqlite3_value **);
  } aFuncs[] = {
    { "min",               -1, 0, SQLITE_UTF8,    1, minmaxFunc },
    { "min",                0, 0, SQLITE_UTF8,    1, 0          },
    { "max",               -1, 1, SQLITE_UTF8,    1, minmaxFunc },
    { "max",                0, 1, SQLITE_UTF8,    1, 0          },
    { "typeof",             1, 0, SQLITE_UTF8,    0, typeofFunc },
    { "length",             1, 0, SQLITE_UTF8,    0, lengthFunc },
    { "substr",             2, 0, SQLITE_UTF8,    0, substrFunc },
    { "substr",             3, 0, SQLITE_UTF8,    0, substrFunc },
    { "abs",                1, 0, SQLITE_UTF8,    0, absFunc    },
    { "round",              1, 0, SQLITE_UTF8,    0, roundFunc  },
    { "round",              2, 0, SQLITE_UTF8,    0, roundFunc  },
    { "upper",              1, 0, SQLITE_UTF8,    0, upperFunc  },
    { "lower",              1, 0, SQLITE_UTF8,    0, lowerFunc  },
    { "coalesce",          -1, 0, SQLITE_UTF8,    0, ifnullFunc },
    { "coalesce",           0, 0, SQLITE_UTF8,    0, 0          },
    { "coalesce",           1, 0, SQLITE_UTF8,    0, 0          },
    { "hex",                1, 0, SQLITE_UTF8,    0, hexFunc    },
    { "ifnull",             2, 0, SQLITE_UTF8,    1, ifnullFunc },
    { "random",            -1, 0, SQLITE_UTF8,    0, randomFunc },
    { "randomblob",         1, 0, SQLITE_UTF8,    0, randomBlob },
    { "nullif",             2, 0, SQLITE_UTF8,    1, nullifFunc },
    { "sqlite_version",     0, 0, SQLITE_UTF8,    0, versionFunc},
    { "quote",              1, 0, SQLITE_UTF8,    0, quoteFunc  },
    { "last_insert_rowid",  0, 0, SQLITE_UTF8, 0, last_insert_rowid },
    { "changes",            0, 0, SQLITE_UTF8, 0, changes           },
    { "total_changes",      0, 0, SQLITE_UTF8, 0, total_changes     },
    { "replace",            3, 0, SQLITE_UTF8,    0, replaceFunc       },
    { "ltrim",              1, 1, SQLITE_UTF8,    0, trimFunc          },
    { "ltrim",              2, 1, SQLITE_UTF8,    0, trimFunc          },
    { "rtrim",              1, 2, SQLITE_UTF8,    0, trimFunc          },
    { "rtrim",              2, 2, SQLITE_UTF8,    0, trimFunc          },
    { "trim",               1, 3, SQLITE_UTF8,    0, trimFunc          },
    { "trim",               2, 3, SQLITE_UTF8,    0, trimFunc          },
    { "zeroblob",           1, 0, SQLITE_UTF8,    0, zeroblobFunc      },
#ifdef SQLITE_SOUNDEX
    { "soundex",            1, 0, SQLITE_UTF8,    0, soundexFunc},
#endif
#ifndef SQLITE_OMIT_LOAD_EXTENSION
    { "load_extension",     1, 0, SQLITE_UTF8, 0, loadExt },
    { "load_extension",     2, 0, SQLITE_UTF8, 0, loadExt },
#endif
  };
  static const struct {
    char *zName;
    signed char nArg;
    u8 argType;
    u8 needCollSeq;
    void (*xStep)(sqlite3_context*,int,sqlite3_value**);
    void (*xFinalize)(sqlite3_context*);
  } aAggs[] = {
    { "min",    1, 0, 1, minmaxStep,   minMaxFinalize },
    { "max",    1, 1, 1, minmaxStep,   minMaxFinalize },
    { "sum",    1, 0, 0, sumStep,      sumFinalize    },
    { "total",  1, 0, 0, sumStep,      totalFinalize    },
    { "avg",    1, 0, 0, sumStep,      avgFinalize    },
    { "count",  0, 0, 0, countStep,    countFinalize  },
    { "count",  1, 0, 0, countStep,    countFinalize  },
    { "group_concat", -1, 0, 0, groupConcatStep, groupConcatFinalize },
  };
  int i;

  for(i=0; i<sizeof(aFuncs)/sizeof(aFuncs[0]); i++){
    void *pArg;
    u8 argType = aFuncs[i].argType;
    pArg = SQLITE_INT_TO_PTR(argType);
    sqlite3CreateFunc(db, aFuncs[i].zName, aFuncs[i].nArg,
        aFuncs[i].eTextRep, pArg, aFuncs[i].xFunc, 0, 0);
    if( aFuncs[i].needCollSeq ){
      FuncDef *pFunc = sqlite3FindFunction(db, aFuncs[i].zName, 
          strlen(aFuncs[i].zName), aFuncs[i].nArg, aFuncs[i].eTextRep, 0);
      if( pFunc && aFuncs[i].needCollSeq ){
        pFunc->needCollSeq = 1;
      }
    }
  }
#ifndef SQLITE_OMIT_ALTERTABLE
  sqlite3AlterFunctions(db);
#endif
#ifndef SQLITE_OMIT_PARSER
  sqlite3AttachFunctions(db);
#endif
  for(i=0; i<sizeof(aAggs)/sizeof(aAggs[0]); i++){
    void *pArg = SQLITE_INT_TO_PTR(aAggs[i].argType);
    sqlite3CreateFunc(db, aAggs[i].zName, aAggs[i].nArg, SQLITE_UTF8, 
        pArg, 0, aAggs[i].xStep, aAggs[i].xFinalize);
    if( aAggs[i].needCollSeq ){
      FuncDef *pFunc = sqlite3FindFunction( db, aAggs[i].zName,
          strlen(aAggs[i].zName), aAggs[i].nArg, SQLITE_UTF8, 0);
      if( pFunc && aAggs[i].needCollSeq ){
        pFunc->needCollSeq = 1;
      }
    }
  }
  sqlite3RegisterDateTimeFunctions(db);
  if( !db->mallocFailed ){
    int rc = sqlite3_overload_function(db, "MATCH", 2);
    assert( rc==SQLITE_NOMEM || rc==SQLITE_OK );
    if( rc==SQLITE_NOMEM ){
      db->mallocFailed = 1;
    }
  }
#ifdef SQLITE_SSE
  (void)sqlite3SseFunctions(db);
#endif
#ifdef SQLITE_CASE_SENSITIVE_LIKE
  sqlite3RegisterLikeFunctions(db, 1);
#else
  sqlite3RegisterLikeFunctions(db, 0);
#endif
}

/*
** Set the LIKEOPT flag on the 2-argument function with the given name.
*/
static void setLikeOptFlag(sqlite3 *db, const char *zName, int flagVal){
  FuncDef *pDef;
................................................................................
  memcpy(aWc, pDef->pUserData, 3);
  assert( (char*)&likeInfoAlt == (char*)&likeInfoAlt.matchAll );
  assert( &((char*)&likeInfoAlt)[1] == (char*)&likeInfoAlt.matchOne );
  assert( &((char*)&likeInfoAlt)[2] == (char*)&likeInfoAlt.matchSet );
  *pIsNocase = (pDef->flags & SQLITE_FUNC_CASE)==0;
  return 1;
}

** This file contains the C functions that implement various SQL
** functions of SQLite.  
**
** There is only one exported symbol in this file - the function
** sqliteRegisterBuildinFunctions() found at the bottom of the file.
** All other code has file scope.
**
** $Id: func.c,v 1.197 2008/08/20 14:49:24 danielk1977 Exp $
*/

#ifndef CREATE_BUILTIN_HASHTABLE

#include "sqliteInt.h"
#include <ctype.h>
#include <stdlib.h>
#include <assert.h>
#include "vdbeInt.h"


/*
** Return the collating function associated with a function.
*/
static CollSeq *sqlite3GetFuncCollSeq(sqlite3_context *context){
  return context->pColl;
}
................................................................................

/*
** This function registered all of the above C functions as SQL
** functions.  This should be the only routine in this file with
** external linkage.
*/
void sqlite3RegisterBuiltinFunctions(sqlite3 *db){



















































































#ifndef SQLITE_OMIT_ALTERTABLE
  sqlite3AlterFunctions(db);
#endif
#ifndef SQLITE_OMIT_PARSER
  sqlite3AttachFunctions(db);
#endif












  sqlite3RegisterDateTimeFunctions(db);
  if( !db->mallocFailed ){
    int rc = sqlite3_overload_function(db, "MATCH", 2);
    assert( rc==SQLITE_NOMEM || rc==SQLITE_OK );
    if( rc==SQLITE_NOMEM ){
      db->mallocFailed = 1;
    }
  }
#ifdef SQLITE_SSE
  (void)sqlite3SseFunctions(db);
#endif





}

/*
** Set the LIKEOPT flag on the 2-argument function with the given name.
*/
static void setLikeOptFlag(sqlite3 *db, const char *zName, int flagVal){
  FuncDef *pDef;
................................................................................
  memcpy(aWc, pDef->pUserData, 3);
  assert( (char*)&likeInfoAlt == (char*)&likeInfoAlt.matchAll );
  assert( &((char*)&likeInfoAlt)[1] == (char*)&likeInfoAlt.matchOne );
  assert( &((char*)&likeInfoAlt)[2] == (char*)&likeInfoAlt.matchSet );
  *pIsNocase = (pDef->flags & SQLITE_FUNC_CASE)==0;
  return 1;
}

/*
** The following three macros, FUNCTION(), LIKEFUNC() and AGGREGATE() are
** used to create the literal values used for the FuncDef structures in
** the global aBuiltinFunc[] array (see below).
**
**   FUNCTION(zName, nArg, iArg, bNC, xFunc)
**     Used to create a scalar function definition of a function zName 
**     implemented by C function xFunc that accepts nArg arguments. The
**     value passed as iArg is cast to a (void*) and made available
**     as the user-data (sqlite3_user_data()) for the function. If 
**     argument bNC is true, then the FuncDef.needCollate flag is set.
**
**   AGGREGATE(zName, nArg, iArg, bNC, xStep, xFinal)
**     Used to create an aggregate function definition implemented by
**     the C functions xStep and xFinal. The first four parameters
**     are interpreted in the same way as the first 4 parameters to
**     FUNCTION().
**
**   LIKEFUNC(zName, nArg, pArg, flags)
**     Used to create a scalar function definition of a function zName 
**     that accepts nArg arguments and is implemented by a call to C 
**     function likeFunc. Argument pArg is cast to a (void *) and made
**     available as the function user-data (sqlite3_user_data()). The
**     FuncDef.flags variable is set to the value passed as the flags
**     parameter.
**
** See below for examples.
*/
#define FUNCTION(zName, nArg, iArg, bNC, xFunc) \
  {nArg, SQLITE_UTF8, bNC, 0, SQLITE_INT_TO_PTR(iArg), 0, xFunc, 0, 0, #zName}

#define LIKEFUNC(zName, nArg, arg, flags) \
  {nArg, SQLITE_UTF8, 0, flags, (void *)arg, 0, likeFunc, 0, 0, #zName}

#define AGGREGATE(zName, nArg, arg, nc, xStep, xFinal) \
  {nArg, SQLITE_UTF8, nc, 0, SQLITE_INT_TO_PTR(arg), 0, 0, xStep,xFinal, #zName}

#endif

/*
** This array of FuncDef structures contains most of the "built-in" functions
** and aggregates. Function users (the other routines in the SQL compiler)
** call the following function to access the FuncDef structures stored in 
** this array:
** 
**     int sqlite3GetBuiltinFunction(const char *z, int n, FuncDef **paFunc);
**
** The caller passes the name of the required function and its length
** in parameters z and n, respectively. The value returned is the number
** of FuncDef structures found in the aBuiltinFunc[] array that match
** the requested name. If no match is found, 0 is returned. *paFunc is 
** set to point at a static array containing that subset of aBuiltinFunc[] 
** before returning.
**
** The implementation of sqlite3GetBuiltinFunction() is generated by
** the program found in tool/mkfunction.c, which is compiled and executed
** as part of the build process. The routine generated by this program 
** assumes that if there are two or more entries in the aBuiltinFunc[] 
** array with the same name (i.e. two versions of the "max" function), 
** then they must be stored in adjacent slots. 
*/
static FuncDef aBuiltinFunc[] = {
  FUNCTION(ltrim,              1, 1, 0, trimFunc         ),
  FUNCTION(ltrim,              2, 1, 0, trimFunc         ),
  FUNCTION(rtrim,              1, 2, 0, trimFunc         ),
  FUNCTION(rtrim,              2, 2, 0, trimFunc         ),
  FUNCTION(trim,               1, 3, 0, trimFunc         ),
  FUNCTION(trim,               2, 3, 0, trimFunc         ),
  FUNCTION(min,               -1, 0, 1, minmaxFunc       ),
  FUNCTION(min,                0, 0, 1, 0                ),
  AGGREGATE(min,               1, 0, 1, minmaxStep,      minMaxFinalize ),
  FUNCTION(max,               -1, 1, 1, minmaxFunc       ),
  FUNCTION(max,                0, 1, 1, 0                ),
  AGGREGATE(max,               1, 1, 1, minmaxStep,      minMaxFinalize ),
  FUNCTION(typeof,             1, 0, 0, typeofFunc       ),
  FUNCTION(length,             1, 0, 0, lengthFunc       ),
  FUNCTION(substr,             2, 0, 0, substrFunc       ),
  FUNCTION(substr,             3, 0, 0, substrFunc       ),
  FUNCTION(abs,                1, 0, 0, absFunc          ),
  FUNCTION(round,              1, 0, 0, roundFunc        ),
  FUNCTION(round,              2, 0, 0, roundFunc        ),
  FUNCTION(upper,              1, 0, 0, upperFunc        ),
  FUNCTION(lower,              1, 0, 0, lowerFunc        ),
  FUNCTION(coalesce,           1, 0, 0, 0                ),
  FUNCTION(coalesce,          -1, 0, 0, ifnullFunc       ),
  FUNCTION(coalesce,           0, 0, 0, 0                ),
  FUNCTION(hex,                1, 0, 0, hexFunc          ),
  FUNCTION(ifnull,             2, 0, 1, ifnullFunc       ),
  FUNCTION(random,            -1, 0, 0, randomFunc       ),
  FUNCTION(randomblob,         1, 0, 0, randomBlob       ),
  FUNCTION(nullif,             2, 0, 1, nullifFunc       ),
  FUNCTION(sqlite_version,     0, 0, 0, versionFunc      ),
  FUNCTION(quote,              1, 0, 0, quoteFunc        ),
  FUNCTION(last_insert_rowid,  0, 0, 0, last_insert_rowid),
  FUNCTION(changes,            0, 0, 0, changes          ),
  FUNCTION(total_changes,      0, 0, 0, total_changes    ),
  FUNCTION(replace,            3, 0, 0, replaceFunc      ),
  FUNCTION(zeroblob,           1, 0, 0, zeroblobFunc     ),
#ifdef SQLITE_SOUNDEX
  FUNCTION(soundex,            1, 0, 0, soundexFunc      ),
#endif
#ifndef SQLITE_OMIT_LOAD_EXTENSION
  FUNCTION(load_extension,     1, 0, 0, loadExt          ),
  FUNCTION(load_extension,     2, 0, 0, loadExt          ),
#endif
  AGGREGATE(sum,               1, 0, 0, sumStep,         sumFinalize    ),
  AGGREGATE(total,             1, 0, 0, sumStep,         totalFinalize    ),
  AGGREGATE(avg,               1, 0, 0, sumStep,         avgFinalize    ),
  AGGREGATE(count,             0, 0, 0, countStep,       countFinalize  ),
  AGGREGATE(count,             1, 0, 0, countStep,       countFinalize  ),
  AGGREGATE(group_concat,     -1, 0, 0, groupConcatStep, groupConcatFinalize),

  LIKEFUNC(glob, 2, &globInfo, SQLITE_FUNC_LIKE|SQLITE_FUNC_CASE),
#ifdef SQLITE_CASE_SENSITIVE_LIKE
  LIKEFUNC(like, 2, &likeInfoAlt, SQLITE_FUNC_LIKE|SQLITE_FUNC_CASE),
  LIKEFUNC(like, 3, &likeInfoAlt, SQLITE_FUNC_LIKE|SQLITE_FUNC_CASE),
#else
  LIKEFUNC(like, 2, &likeInfoNorm, SQLITE_FUNC_LIKE),
  LIKEFUNC(like, 3, &likeInfoNorm, SQLITE_FUNC_LIKE),
#endif
};

**
*************************************************************************
** Main file for the SQLite library.  The routines in this file
** implement the programmer interface to the library.  Routines in
** other files are for internal use by SQLite and should not be
** accessed by users of the library.
**
** $Id: main.c,v 1.488 2008/08/12 15:21:12 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

#ifdef SQLITE_ENABLE_FTS3
# include "fts3.h"
#endif
................................................................................
  ** sqlite3_os_init() when it invokes sqlite3_vfs_register(), but other
  ** recursive calls might also be possible.
  */
  sqlite3_mutex_enter(sqlite3Config.pInitMutex);
  if( sqlite3Config.isInit==0 && inProgress==0 ){
    inProgress = 1;
    rc = sqlite3_os_init();





    inProgress = 0;
    sqlite3Config.isInit = (rc==SQLITE_OK ? 1 : 0);
  }
  sqlite3_mutex_leave(sqlite3Config.pInitMutex);

  /* Go back under the static mutex and clean up the recursive
  ** mutex to prevent a resource leak.
................................................................................
** Undo the effects of sqlite3_initialize().  Must not be called while
** there are outstanding database connections or memory allocations or
** while any part of SQLite is otherwise in use in any thread.  This
** routine is not threadsafe.  Not by a long shot.
*/
int sqlite3_shutdown(void){
  sqlite3Config.isMallocInit = 0;

  if( sqlite3Config.isInit ){
    sqlite3_os_end();
  }
  if( sqlite3Config.m.xShutdown ){
    sqlite3MallocEnd();
  }
  if( sqlite3Config.mutex.xMutexEnd ){

**
*************************************************************************
** Main file for the SQLite library.  The routines in this file
** implement the programmer interface to the library.  Routines in
** other files are for internal use by SQLite and should not be
** accessed by users of the library.
**
** $Id: main.c,v 1.489 2008/08/20 14:49:24 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

#ifdef SQLITE_ENABLE_FTS3
# include "fts3.h"
#endif
................................................................................
  ** sqlite3_os_init() when it invokes sqlite3_vfs_register(), but other
  ** recursive calls might also be possible.
  */
  sqlite3_mutex_enter(sqlite3Config.pInitMutex);
  if( sqlite3Config.isInit==0 && inProgress==0 ){
    inProgress = 1;
    rc = sqlite3_os_init();
    if( rc==SQLITE_OK ){
      rc = sqlite3PcacheInitialize();
      sqlite3PCacheBufferSetup(sqlite3Config.pPage, sqlite3Config.szPage, 
          sqlite3Config.nPage);
    }
    inProgress = 0;
    sqlite3Config.isInit = (rc==SQLITE_OK ? 1 : 0);
  }
  sqlite3_mutex_leave(sqlite3Config.pInitMutex);

  /* Go back under the static mutex and clean up the recursive
  ** mutex to prevent a resource leak.
................................................................................
** Undo the effects of sqlite3_initialize().  Must not be called while
** there are outstanding database connections or memory allocations or
** while any part of SQLite is otherwise in use in any thread.  This
** routine is not threadsafe.  Not by a long shot.
*/
int sqlite3_shutdown(void){
  sqlite3Config.isMallocInit = 0;
  sqlite3PcacheShutdown();
  if( sqlite3Config.isInit ){
    sqlite3_os_end();
  }
  if( sqlite3Config.m.xShutdown ){
    sqlite3MallocEnd();
  }
  if( sqlite3Config.mutex.xMutexEnd ){

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** Memory allocation functions used throughout sqlite.
**
** $Id: malloc.c,v 1.34 2008/08/05 17:53:23 drh Exp $
*/
#include "sqliteInt.h"
#include <stdarg.h>
#include <ctype.h>

/*
** This routine runs when the memory allocator sees that the
................................................................................

/*
** Allocate memory to be used by the page cache.  Make use of the
** memory buffer provided by SQLITE_CONFIG_PAGECACHE if there is one
** and that memory is of the right size and is not completely
** consumed.  Otherwise, failover to sqlite3Malloc().
*/

void *sqlite3PageMalloc(int n){
  void *p;
  assert( n>0 );
  assert( (n & (n-1))==0 );
  assert( n>=512 && n<=32768 );

  if( sqlite3Config.szPage<n ){
................................................................................
      for(i=0; i<mem0.nPageFree-1; i++){
        assert( mem0.aPageFree[i]!=mem0.aPageFree[mem0.nPageFree-1] );
      }
#endif
    }
  }
}


/*
** TRUE if p is a lookaside memory allocation from db
*/
static int isLookaside(sqlite3 *db, void *p){
  return db && p && p>=db->lookaside.pStart && p<db->lookaside.pEnd;
}

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** Memory allocation functions used throughout sqlite.
**
** $Id: malloc.c,v 1.35 2008/08/20 14:49:24 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include <stdarg.h>
#include <ctype.h>

/*
** This routine runs when the memory allocator sees that the
................................................................................

/*
** Allocate memory to be used by the page cache.  Make use of the
** memory buffer provided by SQLITE_CONFIG_PAGECACHE if there is one
** and that memory is of the right size and is not completely
** consumed.  Otherwise, failover to sqlite3Malloc().
*/
#if 0
void *sqlite3PageMalloc(int n){
  void *p;
  assert( n>0 );
  assert( (n & (n-1))==0 );
  assert( n>=512 && n<=32768 );

  if( sqlite3Config.szPage<n ){
................................................................................
      for(i=0; i<mem0.nPageFree-1; i++){
        assert( mem0.aPageFree[i]!=mem0.aPageFree[mem0.nPageFree-1] );
      }
#endif
    }
  }
}
#endif

/*
** TRUE if p is a lookaside memory allocation from db
*/
static int isLookaside(sqlite3 *db, void *p){
  return db && p && p>=db->lookaside.pStart && p<db->lookaside.pEnd;
}

** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.469 2008/08/02 03:50:39 drh Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include <assert.h>
#include <string.h>

/*
** Macros for troubleshooting.  Normally turned off
*/
#if 0
#define sqlite3DebugPrintf printf
#define PAGERTRACE1(X)       sqlite3DebugPrintf(X)
................................................................................

/*
** This macro rounds values up so that if the value is an address it
** is guaranteed to be an address that is aligned to an 8-byte boundary.
*/
#define FORCE_ALIGNMENT(X)   (((X)+7)&~7)

typedef struct PgHdr PgHdr;

/*
** Each pager stores all currently unreferenced pages in a list sorted
** in least-recently-used (LRU) order (i.e. the first item on the list has 
** not been referenced in a long time, the last item has been recently
** used). An instance of this structure is included as part of each
** pager structure for this purpose (variable Pager.lru).
**
** Additionally, if memory-management is enabled, all unreferenced pages 
** are stored in a global LRU list (global variable sqlite3LruPageList).
**
** In both cases, the PagerLruList.pFirstSynced variable points to
** the first page in the corresponding list that does not require an
** fsync() operation before its memory can be reclaimed. If no such
** page exists, PagerLruList.pFirstSynced is set to NULL.
*/
typedef struct PagerLruList PagerLruList;
struct PagerLruList {
  PgHdr *pFirst;         /* First page in LRU list */
  PgHdr *pLast;          /* Last page in LRU list (the most recently used) */
  PgHdr *pFirstSynced;   /* First page in list with PgHdr.needSync==0 */
};

/*
** The following structure contains the next and previous pointers used
** to link a PgHdr structure into a PagerLruList linked list. 
*/
typedef struct PagerLruLink PagerLruLink;
struct PagerLruLink {
  PgHdr *pNext;
  PgHdr *pPrev;
};

/*
** Each in-memory image of a page begins with the following header.
** This header is only visible to this pager module.  The client
** code that calls pager sees only the data that follows the header.
**
** Client code should call sqlite3PagerWrite() on a page prior to making
** any modifications to that page.  The first time sqlite3PagerWrite()
** is called, the original page contents are written into the rollback
** journal and PgHdr.inJournal and PgHdr.needSync are set.  Later, once
** the journal page has made it onto the disk surface, PgHdr.needSync
** is cleared.  The modified page cannot be written back into the original
** database file until the journal pages has been synced to disk and the
** PgHdr.needSync has been cleared.
**
** The PgHdr.dirty flag is set when sqlite3PagerWrite() is called and
** is cleared again when the page content is written back to the original
** database file.
**
** Details of important structure elements:
**
** needSync
**
**     If this is true, this means that it is not safe to write the page
**     content to the database because the original content needed
**     for rollback has not by synced to the main rollback journal.
**     The original content may have been written to the rollback journal
**     but it has not yet been synced.  So we cannot write to the database
**     file because power failure might cause the page in the journal file
**     to never reach the disk.  It is as if the write to the journal file
**     does not occur until the journal file is synced.
**     
**     This flag is false if the page content exactly matches what
**     currently exists in the database file.  The needSync flag is also
**     false if the original content has been written to the main rollback
**     journal and synced.  If the page represents a new page that has
**     been added onto the end of the database during the current
**     transaction, the needSync flag is true until the original database
**     size in the journal header has been synced to disk.
**
** inJournal
**
**     This is true if the original page has been written into the main
**     rollback journal.  This is always false for new pages added to
**     the end of the database file during the current transaction.
**     And this flag says nothing about whether or not the journal
**     has been synced to disk.  For pages that are in the original
**     database file, the following expression should always be true:
**
**       inJournal = sqlite3BitvecTest(pPager->pInJournal, pgno)
**
**     The pPager->pInJournal object is only valid for the original
**     pages of the database, not new pages that are added to the end
**     of the database, so obviously the above expression cannot be
**     valid for new pages.  For new pages inJournal is always 0.
**
** dirty
**
**     When true, this means that the content of the page has been
**     modified and needs to be written back to the database file.
**     If false, it means that either the content of the page is
**     unchanged or else the content is unimportant and we do not
**     care whether or not it is preserved.
**
** alwaysRollback
**
**     This means that the sqlite3PagerDontRollback() API should be
**     ignored for this page.  The DontRollback() API attempts to say
**     that the content of the page on disk is unimportant (it is an
**     unused page on the freelist) so that it is unnecessary to 
**     rollback changes to this page because the content of the page
**     can change without changing the meaning of the database.  This
**     flag overrides any DontRollback() attempt.  This flag is set
**     when a page that originally contained valid data is added to
**     the freelist.  Later in the same transaction, this page might
**     be pulled from the freelist and reused for something different
**     and at that point the DontRollback() API will be called because
**     pages taken from the freelist do not need to be protected by
**     the rollback journal.  But this flag says that the page was
**     not originally part of the freelist so that it still needs to
**     be rolled back in spite of any subsequent DontRollback() calls.
**
** needRead 
**
**     This flag means (when true) that the content of the page has
**     not yet been loaded from disk.  The in-memory content is just
**     garbage.  (Actually, we zero the content, but you should not
**     make any assumptions about the content nevertheless.)  If the
**     content is needed in the future, it should be read from the
**     original database file.
*/
struct PgHdr {
  Pager *pPager;                 /* The pager to which this page belongs */
  Pgno pgno;                     /* The page number for this page */
  PgHdr *pNextHash, *pPrevHash;  /* Hash collision chain for PgHdr.pgno */
  PagerLruLink free;             /* Next and previous free pages */
  PgHdr *pNextAll;               /* A list of all pages */
  u8 inJournal;                  /* TRUE if has been written to journal */
  u8 dirty;                      /* TRUE if we need to write back changes */
  u8 needSync;                   /* Sync journal before writing this page */
  u8 alwaysRollback;             /* Disable DontRollback() for this page */
  u8 needRead;                   /* Read content if PagerWrite() is called */
  short int nRef;                /* Number of users of this page */
  PgHdr *pDirty, *pPrevDirty;    /* Dirty pages */
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
  PgHdr *pPrevAll;               /* A list of all pages */
  PagerLruLink gfree;            /* Global list of nRef==0 pages */
#endif
#ifdef SQLITE_CHECK_PAGES
  u32 pageHash;
#endif
  void *pData;                   /* Page data */
  /* Pager.nExtra bytes of local data appended to this header */
};

/*
** For an in-memory only database, some extra information is recorded about
** each page so that changes can be rolled back.  (Journal files are not
** used for in-memory databases.)  The following information is added to
** the end of every EXTRA block for in-memory databases.
**
** This information could have been added directly to the PgHdr structure.
** But then it would take up an extra 8 bytes of storage on every PgHdr
** even for disk-based databases.  Splitting it out saves 8 bytes.  This
** is only a savings of 0.8% but those percentages add up.
*/
typedef struct PgHistory PgHistory;
struct PgHistory {
  u8 *pOrig;     /* Original page text.  Restore to this on a full rollback */
  u8 *pStmt;     /* Text as it was at the beginning of the current statement */
  PgHdr *pNextStmt, *pPrevStmt;  /* List of pages in the statement journal */
  u8 inStmt;                     /* TRUE if in the statement subjournal */
};

/*
** A macro used for invoking the codec if there is one
*/
#ifdef SQLITE_HAS_CODEC
# define CODEC1(P,D,N,X) if( P->xCodec!=0 ){ P->xCodec(P->pCodecArg,D,N,X); }
# define CODEC2(P,D,N,X) ((char*)(P->xCodec!=0?P->xCodec(P->pCodecArg,D,N,X):D))
#else
# define CODEC1(P,D,N,X) /* NO-OP */
# define CODEC2(P,D,N,X) ((char*)D)
#endif

/*
** Convert a pointer to a PgHdr into a pointer to its data
** and back again.
*/
#define PGHDR_TO_DATA(P)    ((P)->pData)
#define PGHDR_TO_EXTRA(G,P) ((void*)&((G)[1]))
#define PGHDR_TO_HIST(P,PGR)  \
            ((PgHistory*)&((char*)(&(P)[1]))[(PGR)->nExtra])

/*
** A open page cache is an instance of the following structure.
**
** Pager.errCode may be set to SQLITE_IOERR, SQLITE_CORRUPT, or
** or SQLITE_FULL. Once one of the first three errors occurs, it persists
** and is returned as the result of every major pager API call.  The
** SQLITE_FULL return code is slightly different. It persists only until the
................................................................................
  int stmtSize;               /* Size of database (in pages) at stmt_begin() */
  int nRec;                   /* Number of pages written to the journal */
  u32 cksumInit;              /* Quasi-random value added to every checksum */
  int stmtNRec;               /* Number of records in stmt subjournal */
  int nExtra;                 /* Add this many bytes to each in-memory page */
  int pageSize;               /* Number of bytes in a page */
  int nPage;                  /* Total number of in-memory pages */
  int nRef;                   /* Number of in-memory pages with PgHdr.nRef>0 */
  int mxPage;                 /* Maximum number of pages to hold in cache */
  Pgno mxPgno;                /* Maximum allowed size of the database */
  Bitvec *pInJournal;         /* One bit for each page in the database file */
  Bitvec *pInStmt;            /* One bit for each page in the database */
  char *zFilename;            /* Name of the database file */
  char *zJournal;             /* Name of the journal file */
  char *zDirectory;           /* Directory hold database and journal files */
  sqlite3_file *fd, *jfd;     /* File descriptors for database and journal */
  sqlite3_file *stfd;         /* File descriptor for the statement subjournal*/
  BusyHandler *pBusyHandler;  /* Pointer to sqlite.busyHandler */
  PagerLruList lru;           /* LRU list of free pages */
  PgHdr *pAll;                /* List of all pages */
  PgHdr *pStmt;               /* List of pages in the statement subjournal */
  PgHdr *pDirty;              /* List of all dirty pages */
  i64 journalOff;             /* Current byte offset in the journal file */
  i64 journalHdr;             /* Byte offset to previous journal header */
  i64 stmtHdrOff;             /* First journal header written this statement */
  i64 stmtCksum;              /* cksumInit when statement was started */
  i64 stmtJSize;              /* Size of journal at stmt_begin() */
  int sectorSize;             /* Assumed sector size during rollback */
#ifdef SQLITE_TEST
................................................................................
#endif
  void (*xDestructor)(DbPage*,int); /* Call this routine when freeing pages */
  void (*xReiniter)(DbPage*,int);   /* Call this routine when reloading pages */
#ifdef SQLITE_HAS_CODEC
  void *(*xCodec)(void*,void*,Pgno,int); /* Routine for en/decoding data */
  void *pCodecArg;            /* First argument to xCodec() */
#endif
  int nHash;                  /* Size of the pager hash table */
  PgHdr **aHash;              /* Hash table to map page number to PgHdr */
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
  Pager *pNext;               /* Doubly linked list of pagers on which */
  Pager *pPrev;               /* sqlite3_release_memory() will work */
  volatile int iInUseMM;      /* Non-zero if unavailable to MM */
  volatile int iInUseDB;      /* Non-zero if in sqlite3_release_memory() */
#endif
  char *pTmpSpace;            /* Pager.pageSize bytes of space for tmp use */
  char dbFileVers[16];        /* Changes whenever database file changes */
  i64 journalSizeLimit;       /* Size limit for persistent journal files */

};

/*
** The following global variables hold counters used for
** testing purposes only.  These variables do not exist in
** a non-testing build.  These variables are not thread-safe.
*/
#ifdef SQLITE_TEST
int sqlite3_pager_readdb_count = 0;    /* Number of full pages read from DB */
int sqlite3_pager_writedb_count = 0;   /* Number of full pages written to DB */
int sqlite3_pager_writej_count = 0;    /* Number of pages written to journal */
int sqlite3_pager_pgfree_count = 0;    /* Number of cache pages freed */
# define PAGER_INCR(v)  v++
#else
# define PAGER_INCR(v)
#endif

/*
** The following variable points to the head of a double-linked list
** of all pagers that are eligible for page stealing by the
** sqlite3_release_memory() interface.  Access to this list is
** protected by the SQLITE_MUTEX_STATIC_MEM2 mutex.
*/
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
static Pager *sqlite3PagerList = 0;
static PagerLruList sqlite3LruPageList = {0, 0, 0};
#endif


/*
** Journal files begin with the following magic string.  The data
** was obtained from /dev/random.  It is used only as a sanity check.
**
** Since version 2.8.0, the journal format contains additional sanity
................................................................................

/*
** The maximum legal page number is (2^31 - 1).
*/
#define PAGER_MAX_PGNO 2147483647

/*
** The pagerEnter() and pagerLeave() routines acquire and release
** a mutex on each pager.  The mutex is recursive.
**
** This is a special-purpose mutex.  It only provides mutual exclusion
** between the Btree and the Memory Management sqlite3_release_memory()
** function.  It does not prevent, for example, two Btrees from accessing
** the same pager at the same time.  Other general-purpose mutexes in
** the btree layer handle that chore.
*/
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
  static void pagerEnter(Pager *p){
    p->iInUseDB++;
    if( p->iInUseMM && p->iInUseDB==1 ){
#ifndef SQLITE_MUTEX_NOOP
      sqlite3_mutex *mutex;
      mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM2);
#endif
      p->iInUseDB = 0;
      sqlite3_mutex_enter(mutex);
      p->iInUseDB = 1;
      sqlite3_mutex_leave(mutex);
    }
    assert( p->iInUseMM==0 );
  }
  static void pagerLeave(Pager *p){
    p->iInUseDB--;
    assert( p->iInUseDB>=0 );
  }
#else
# define pagerEnter(X)
# define pagerLeave(X)
#endif

/*
** Add page pPg to the end of the linked list managed by structure
** pList (pPg becomes the last entry in the list - the most recently 
** used). Argument pLink should point to either pPg->free or pPg->gfree,
** depending on whether pPg is being added to the pager-specific or
** global LRU list.
*/
static void listAdd(PagerLruList *pList, PagerLruLink *pLink, PgHdr *pPg){
  pLink->pNext = 0;
  pLink->pPrev = pList->pLast;

#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
  assert(pLink==&pPg->free || pLink==&pPg->gfree);
  assert(pLink==&pPg->gfree || pList!=&sqlite3LruPageList);
#endif

  if( pList->pLast ){
    int iOff = (char *)pLink - (char *)pPg;
    PagerLruLink *pLastLink = (PagerLruLink *)(&((u8 *)pList->pLast)[iOff]);
    pLastLink->pNext = pPg;
  }else{
    assert(!pList->pFirst);
    pList->pFirst = pPg;
  }

  pList->pLast = pPg;
  if( !pList->pFirstSynced && pPg->needSync==0 ){
    pList->pFirstSynced = pPg;
  }
}

/*
** Remove pPg from the list managed by the structure pointed to by pList.
**
** Argument pLink should point to either pPg->free or pPg->gfree, depending 
** on whether pPg is being added to the pager-specific or global LRU list.
*/
static void listRemove(PagerLruList *pList, PagerLruLink *pLink, PgHdr *pPg){
  int iOff = (char *)pLink - (char *)pPg;

#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
  assert(pLink==&pPg->free || pLink==&pPg->gfree);
  assert(pLink==&pPg->gfree || pList!=&sqlite3LruPageList);
#endif

  if( pPg==pList->pFirst ){
    pList->pFirst = pLink->pNext;
  }
  if( pPg==pList->pLast ){
    pList->pLast = pLink->pPrev;
  }
  if( pLink->pPrev ){
    PagerLruLink *pPrevLink = (PagerLruLink *)(&((u8 *)pLink->pPrev)[iOff]);
    pPrevLink->pNext = pLink->pNext;
  }
  if( pLink->pNext ){
    PagerLruLink *pNextLink = (PagerLruLink *)(&((u8 *)pLink->pNext)[iOff]);
    pNextLink->pPrev = pLink->pPrev;
  }
  if( pPg==pList->pFirstSynced ){
    PgHdr *p = pLink->pNext;
    while( p && p->needSync ){
      PagerLruLink *pL = (PagerLruLink *)(&((u8 *)p)[iOff]);
      p = pL->pNext;
    }
    pList->pFirstSynced = p;
  }

  pLink->pNext = pLink->pPrev = 0;
}

/* 
** Add page pPg to the list of free pages for the pager. If 
** memory-management is enabled, also add the page to the global 
** list of free pages.
*/
static void lruListAdd(PgHdr *pPg){
  listAdd(&pPg->pPager->lru, &pPg->free, pPg);
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
  if( !pPg->pPager->memDb ){
    sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_LRU));
    listAdd(&sqlite3LruPageList, &pPg->gfree, pPg);
    sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_LRU));
  }
#endif
}

/* 
** Remove page pPg from the list of free pages for the associated pager.
** If memory-management is enabled, also remove pPg from the global list
** of free pages.
*/
static void lruListRemove(PgHdr *pPg){
  listRemove(&pPg->pPager->lru, &pPg->free, pPg);
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
  if( !pPg->pPager->memDb ){
    sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_LRU));
    listRemove(&sqlite3LruPageList, &pPg->gfree, pPg);
    sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_LRU));
  }
#endif
}

/* 
** This function is called just after the needSync flag has been cleared
** from all pages managed by pPager (usually because the journal file
** has just been synced). It updates the pPager->lru.pFirstSynced variable
** and, if memory-management is enabled, the sqlite3LruPageList.pFirstSynced
** variable also.
*/
static void lruListSetFirstSynced(Pager *pPager){
  pPager->lru.pFirstSynced = pPager->lru.pFirst;
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
  if( !pPager->memDb ){
    PgHdr *p;
    sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_LRU));
    for(p=sqlite3LruPageList.pFirst; p && p->needSync; p=p->gfree.pNext);
    assert(p==pPager->lru.pFirstSynced || p==sqlite3LruPageList.pFirstSynced);
    sqlite3LruPageList.pFirstSynced = p;
    sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_LRU));
  }
#endif
}

/*
** Return true if page *pPg has already been written to the statement
** journal (or statement snapshot has been created, if *pPg is part
** of an in-memory database).
*/
static int pageInStatement(PgHdr *pPg){
  Pager *pPager = pPg->pPager;
  if( MEMDB ){
    return PGHDR_TO_HIST(pPg, pPager)->inStmt;

  }else{
    return sqlite3BitvecTest(pPager->pInStmt, pPg->pgno);
  }
}

/*
** Change the size of the pager hash table to N.  N must be a power
** of two.
*/
static void pager_resize_hash_table(Pager *pPager, int N){
  PgHdr **aHash, *pPg;
  assert( N>0 && (N&(N-1))==0 );
#ifdef SQLITE_MALLOC_SOFT_LIMIT
  if( N*sizeof(aHash[0])>SQLITE_MALLOC_SOFT_LIMIT ){
    N = SQLITE_MALLOC_SOFT_LIMIT/sizeof(aHash[0]);
  }
  if( N==pPager->nHash ) return;
#endif
  pagerLeave(pPager);
  if( pPager->aHash!=0 ) sqlite3BeginBenignMalloc();
  aHash = sqlite3MallocZero( sizeof(aHash[0])*N );
  if( pPager->aHash!=0 ) sqlite3EndBenignMalloc();
  pagerEnter(pPager);
  if( aHash==0 ){
    /* Failure to rehash is not an error.  It is only a performance hit. */
    return;
  }
  sqlite3_free(pPager->aHash);
  pPager->nHash = N;
  pPager->aHash = aHash;
  for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
    int h;
    if( pPg->pgno==0 ){
      assert( pPg->pNextHash==0 && pPg->pPrevHash==0 );
      continue;
    }
    h = pPg->pgno & (N-1);
    pPg->pNextHash = aHash[h];
    if( aHash[h] ){
      aHash[h]->pPrevHash = pPg;
    }
    aHash[h] = pPg;
    pPg->pPrevHash = 0;
  }
}

/*
** Read a 32-bit integer from the given file descriptor.  Store the integer
** that is read in *pRes.  Return SQLITE_OK if everything worked, or an
** error code is something goes wrong.
**
** All values are stored on disk as big-endian.
*/
................................................................................
  );
  if(
    rc2==SQLITE_FULL ||
    rc2==SQLITE_IOERR ||
    rc2==SQLITE_CORRUPT
  ){
    pPager->errCode = rc;
    if( pPager->state==PAGER_UNLOCK && pPager->nRef==0 ){


      /* If the pager is already unlocked, call pager_unlock() now to
      ** clear the error state and ensure that the pager-cache is 
      ** completely empty.
      */
      pager_unlock(pPager);
    }
  }
................................................................................
  int i;
  for(i=0; i<nByte; i++){
    hash = (hash*1039) + pData[i];
  }
  return hash;
}
static u32 pager_pagehash(PgHdr *pPage){
  return pager_datahash(pPage->pPager->pageSize, 
                        (unsigned char *)PGHDR_TO_DATA(pPage));



}

/*
** The CHECK_PAGE macro takes a PgHdr* as an argument. If SQLITE_CHECK_PAGES
** is defined, and NDEBUG is not defined, an assert() statement checks
** that the page is either dirty or still matches the calculated page-hash.
*/
#define CHECK_PAGE(x) checkPage(x)
static void checkPage(PgHdr *pPg){
  Pager *pPager = pPg->pPager;
  assert( !pPg->pageHash || pPager->errCode || MEMDB || pPg->dirty || 
      pPg->pageHash==pager_pagehash(pPg) );
}

#else
#define pager_datahash(X,Y)  0
#define pager_pagehash(X)  0
#define CHECK_PAGE(x)
#endif
................................................................................
   && jrnlSize>jrnlOff
  ){
    rc = sqlite3OsTruncate(pPager->jfd, jrnlOff);
  }
  return rc;
}

/*
** Add or remove a page from the list of all pages that are in the
** statement journal.
**
** The Pager keeps a separate list of pages that are currently in
** the statement journal.  This helps the sqlite3PagerStmtCommit()
** routine run MUCH faster for the common case where there are many
** pages in memory but only a few are in the statement journal.
*/
static void page_add_to_stmt_list(PgHdr *pPg){
  Pager *pPager = pPg->pPager;
  PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager);
  assert( MEMDB );
  if( !pHist->inStmt ){
    assert( pHist->pPrevStmt==0 && pHist->pNextStmt==0 );
    if( pPager->pStmt ){
      PGHDR_TO_HIST(pPager->pStmt, pPager)->pPrevStmt = pPg;
    }
    pHist->pNextStmt = pPager->pStmt;
    pPager->pStmt = pPg;
    pHist->inStmt = 1;
  }
}

/*
** Find a page in the hash table given its page number.  Return
** a pointer to the page or NULL if not found.
*/
static PgHdr *pager_lookup(Pager *pPager, Pgno pgno){
  PgHdr *p;
  if( pPager->aHash==0 ) return 0;
  p = pPager->aHash[pgno & (pPager->nHash-1)];
  while( p && p->pgno!=pgno ){
    p = p->pNextHash;
  }
  return p;
}

/*
** Clear the in-memory cache.  This routine
** sets the state of the pager back to what it was when it was first
** opened.  Any outstanding pages are invalidated and subsequent attempts
** to access those pages will likely result in a coredump.
*/
static void pager_reset(Pager *pPager){
  PgHdr *pPg, *pNext;
  if( pPager->errCode ) return;
  for(pPg=pPager->pAll; pPg; pPg=pNext){
    IOTRACE(("PGFREE %p %d\n", pPager, pPg->pgno));
    PAGER_INCR(sqlite3_pager_pgfree_count);
    pNext = pPg->pNextAll;
    lruListRemove(pPg);
    sqlite3PageFree(pPg->pData);
    sqlite3_free(pPg);
  }
  assert(pPager->lru.pFirst==0);
  assert(pPager->lru.pFirstSynced==0);
  assert(pPager->lru.pLast==0);
  pPager->pStmt = 0;
  pPager->pAll = 0;
  pPager->pDirty = 0;
  pPager->nHash = 0;
  sqlite3_free(pPager->aHash);
  pPager->nPage = 0;
  pPager->aHash = 0;
  pPager->nRef = 0;

}

/*
** Unlock the database file. 
**
** If the pager is currently in error state, discard the contents of 
** the cache and reset the Pager structure internal state. If there is
................................................................................

/*
** Execute a rollback if a transaction is active and unlock the 
** database file. If the pager has already entered the error state, 
** do not attempt the rollback.
*/
static void pagerUnlockAndRollback(Pager *p){
  /* assert( p->state>=PAGER_RESERVED || p->journalOpen==0 ); */
  if( p->errCode==SQLITE_OK && p->state>=PAGER_RESERVED ){
    sqlite3BeginBenignMalloc();
    sqlite3PagerRollback(p);
    sqlite3EndBenignMalloc();
  }
  pager_unlock(p);
#if 0
  assert( p->errCode || !p->journalOpen || (p->exclusiveMode&&!p->journalOff) );
  assert( p->errCode || !p->stmtOpen || p->exclusiveMode );
#endif
}

/*
** This routine ends a transaction.  A transaction is ended by either
** a COMMIT or a ROLLBACK.
**
** When this routine is called, the pager has the journal file open and
................................................................................
** The journal file is either deleted or truncated.
**
** TODO: Consider keeping the journal file open for temporary databases.
** This might give a performance improvement on windows where opening
** a file is an expensive operation.
*/
static int pager_end_transaction(Pager *pPager, int hasMaster){
  PgHdr *pPg;
  int rc = SQLITE_OK;
  int rc2 = SQLITE_OK;
  assert( !MEMDB );
  if( pPager->state<PAGER_RESERVED ){
    return SQLITE_OK;
  }
  sqlite3PagerStmtCommit(pPager);
................................................................................
      pPager->journalOpen = 0;
      if( rc==SQLITE_OK && !pPager->tempFile ){
        rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
      }
    }
    sqlite3BitvecDestroy(pPager->pInJournal);
    pPager->pInJournal = 0;
    for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
      pPg->inJournal = 0;
      pPg->dirty = 0;
      pPg->needSync = 0;
      pPg->alwaysRollback = 0;
#ifdef SQLITE_CHECK_PAGES
      pPg->pageHash = pager_pagehash(pPg);

#endif
    }
    pPager->pDirty = 0;



    pPager->dirtyCache = 0;
    pPager->nRec = 0;
  }else{
    assert( pPager->pInJournal==0 );
  }

  if( !pPager->exclusiveMode ){
................................................................................
    pPager->state = PAGER_SHARED;
  }else if( pPager->state==PAGER_SYNCED ){
    pPager->state = PAGER_EXCLUSIVE;
  }
  pPager->origDbSize = 0;
  pPager->setMaster = 0;
  pPager->needSync = 0;
  lruListSetFirstSynced(pPager);
  pPager->dbSize = -1;
  pPager->dbModified = 0;

  return (rc==SQLITE_OK?rc2:rc);
}

/*
................................................................................
  ** 2008-04-14:  When attempting to vacuum a corrupt database file, it
  ** is possible to fail a statement on a database that does not yet exist.
  ** Do not attempt to write if database file has never been opened.
  */
  pPg = pager_lookup(pPager, pgno);
  PAGERTRACE4("PLAYBACK %d page %d hash(%08x)\n",
               PAGERID(pPager), pgno, pager_datahash(pPager->pageSize, aData));
  if( pPager->state>=PAGER_EXCLUSIVE && (pPg==0 || pPg->needSync==0)

        && pPager->fd->pMethods ){

    i64 offset = (pgno-1)*(i64)pPager->pageSize;
    rc = sqlite3OsWrite(pPager->fd, aData, pPager->pageSize, offset);
    if( pPg ){
      makeClean(pPg);
    }
  }
  if( pPg ){
    /* No page should ever be explicitly rolled back that is in use, except
    ** for page 1 which is held in use in order to keep the lock on the
    ** database active. However such a page may be rolled back as a result
    ** of an internal error resulting in an automatic call to
    ** sqlite3PagerRollback().
    */
    void *pData;
    /* assert( pPg->nRef==0 || pPg->pgno==1 ); */
    pData = PGHDR_TO_DATA(pPg);
    memcpy(pData, aData, pPager->pageSize);
    if( pPager->xReiniter ){
      pPager->xReiniter(pPg, pPager->pageSize);
    }

#ifdef SQLITE_CHECK_PAGES
    pPg->pageHash = pager_pagehash(pPg);
#endif
    /* If this was page 1, then restore the value of Pager.dbFileVers.
    ** Do this before any decoding. */
    if( pgno==1 ){
      memcpy(&pPager->dbFileVers, &((u8*)pData)[24],sizeof(pPager->dbFileVers));
    }

    /* Decode the page just read from disk */
    CODEC1(pPager, pData, pPg->pgno, 3);

  }
  return rc;
}

/*
** Parameter zMaster is the name of a master journal file. A single journal
** file that referred to the master journal file has just been rolled back.
................................................................................
  return rc;
}

/*
** Change the maximum number of in-memory pages that are allowed.
*/
void sqlite3PagerSetCachesize(Pager *pPager, int mxPage){
  if( mxPage>10 ){
    pPager->mxPage = mxPage;
  }else{
    pPager->mxPage = 10;
  }
}

/*
** Adjust the robustness of the database to damage due to OS crashes
** or power failures by changing the number of syncs()s when writing
** the rollback journal.  There are three levels:
**
................................................................................
  vfsFlags |=  SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE |
            SQLITE_OPEN_EXCLUSIVE | SQLITE_OPEN_DELETEONCLOSE;
  rc = sqlite3OsOpen(pPager->pVfs, 0, pFile, vfsFlags, 0);
  assert( rc!=SQLITE_OK || pFile->pMethods );
  return rc;
}



/*
** Create a new page cache and put a pointer to the page cache in *ppPager.
** The file to be cached need not exist.  The file is not locked until
** the first call to sqlite3PagerGet() and is only held open until the
** last page is released using sqlite3PagerUnref().
**
** If zFilename is NULL then a randomly-named temporary file is created
................................................................................
** It is never written to disk.  This can be used to implement an
** in-memory database.
*/
int sqlite3PagerOpen(
  sqlite3_vfs *pVfs,       /* The virtual file system to use */
  Pager **ppPager,         /* Return the Pager structure here */
  const char *zFilename,   /* Name of the database file to open */

  int nExtra,              /* Extra bytes append to each in-memory page */
  int flags,               /* flags controlling this file */
  int vfsFlags             /* flags passed through to sqlite3_vfs.xOpen() */
){
  u8 *pPtr;
  Pager *pPager = 0;
  int rc = SQLITE_OK;
................................................................................
  int i;
  int tempFile = 0;
  int memDb = 0;
  int readOnly = 0;
  int useJournal = (flags & PAGER_OMIT_JOURNAL)==0;
  int noReadlock = (flags & PAGER_NO_READLOCK)!=0;
  int journalFileSize = sqlite3JournalSize(pVfs);

  int szPageDflt = SQLITE_DEFAULT_PAGE_SIZE;
  char *zPathname = 0;
  int nPathname = 0;

  /* The default return is a NULL pointer */
  *ppPager = 0;

................................................................................
    }
    nPathname = strlen(zPathname);
  }

  /* Allocate memory for the pager structure */
  pPager = sqlite3MallocZero(
    sizeof(*pPager) +           /* Pager structure */

    journalFileSize +           /* The journal file structure */ 
    pVfs->szOsFile * 3 +        /* The main db and two journal files */ 
    3*nPathname + 40            /* zFilename, zDirectory, zJournal */
  );
  if( !pPager ){
    sqlite3_free(zPathname);
    return SQLITE_NOMEM;
  }

  pPtr = (u8 *)&pPager[1];
  pPager->vfsFlags = vfsFlags;
  pPager->fd = (sqlite3_file*)&pPtr[pVfs->szOsFile*0];
  pPager->stfd = (sqlite3_file*)&pPtr[pVfs->szOsFile*1];
  pPager->jfd = (sqlite3_file*)&pPtr[pVfs->szOsFile*2];
  pPager->zFilename = (char*)&pPtr[pVfs->szOsFile*2+journalFileSize];
  pPager->zDirectory = &pPager->zFilename[nPathname+1];
  pPager->zJournal = &pPager->zDirectory[nPathname+1];
................................................................................
  ** any Pager.errMask variables.
  */
  if( !pPager || !pPager->pTmpSpace ){
    sqlite3OsClose(pPager->fd);
    sqlite3_free(pPager);
    return ((rc==SQLITE_OK)?SQLITE_NOMEM:rc);
  }



  PAGERTRACE3("OPEN %d %s\n", FILEHANDLEID(pPager->fd), pPager->zFilename);
  IOTRACE(("OPEN %p %s\n", pPager, pPager->zFilename))

  /* Fill in Pager.zDirectory[] */
  memcpy(pPager->zDirectory, pPager->zFilename, nPathname+1);
  for(i=strlen(pPager->zDirectory); i>0 && pPager->zDirectory[i-1]!='/'; i--){}
................................................................................
  /* pPager->needSync = 0; */
  pPager->noSync = pPager->tempFile || !useJournal;
  pPager->fullSync = (pPager->noSync?0:1);
  pPager->sync_flags = SQLITE_SYNC_NORMAL;
  /* pPager->pFirst = 0; */
  /* pPager->pFirstSynced = 0; */
  /* pPager->pLast = 0; */
  pPager->nExtra = FORCE_ALIGNMENT(nExtra);
  pPager->journalSizeLimit = SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT;
  assert(pPager->fd->pMethods||memDb||tempFile);
  if( !memDb ){
    setSectorSize(pPager);
  }
  /* pPager->pBusyHandler = 0; */
  /* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */
  *ppPager = pPager;
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
  pPager->iInUseMM = 0;
  pPager->iInUseDB = 0;
  if( !memDb ){
#ifndef SQLITE_MUTEX_NOOP
    sqlite3_mutex *mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM2);
#endif
    sqlite3_mutex_enter(mutex);
    pPager->pNext = sqlite3PagerList;
    if( sqlite3PagerList ){
      assert( sqlite3PagerList->pPrev==0 );
      sqlite3PagerList->pPrev = pPager;
    }
    pPager->pPrev = 0;
    sqlite3PagerList = pPager;
    sqlite3_mutex_leave(mutex);
  }
#endif
  return SQLITE_OK;
}

/*
** Set the busy handler function.
*/
void sqlite3PagerSetBusyhandler(Pager *pPager, BusyHandler *pBusyHandler){
................................................................................
** inappropriate, then an alternative page size is set to that
** value before returning.
*/
int sqlite3PagerSetPagesize(Pager *pPager, u16 *pPageSize){
  int rc = SQLITE_OK;
  u16 pageSize = *pPageSize;
  assert( pageSize==0 || (pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE) );

  if( pageSize && pageSize!=pPager->pageSize 
   && !pPager->memDb && pPager->nRef==0 
  ){
    char *pNew = (char *)sqlite3PageMalloc(pageSize);
    if( !pNew ){
      rc = SQLITE_NOMEM;
    }else{
      pagerEnter(pPager);
      pager_reset(pPager);
      pPager->pageSize = pageSize;
      setSectorSize(pPager);
      sqlite3PageFree(pPager->pTmpSpace);
      pPager->pTmpSpace = pNew;
      pagerLeave(pPager);
    }
  }
  *pPageSize = pPager->pageSize;

  return rc;
}

/*
** Return a pointer to the "temporary page" buffer held internally
** by the pager.  This is a buffer that is big enough to hold the
** entire content of a database page.  This buffer is used internally
................................................................................
** response is to zero the memory at pDest and continue.  A real IO error 
** will presumably recur and be picked up later (Todo: Think about this).
*/
int sqlite3PagerReadFileheader(Pager *pPager, int N, unsigned char *pDest){
  int rc = SQLITE_OK;
  memset(pDest, 0, N);
  assert(MEMDB||pPager->fd->pMethods||pPager->tempFile);

  if( pPager->fd->pMethods ){
    IOTRACE(("DBHDR %p 0 %d\n", pPager, N))
    rc = sqlite3OsRead(pPager->fd, pDest, N, 0);
    if( rc==SQLITE_IOERR_SHORT_READ ){
      rc = SQLITE_OK;
    }
  }

  return rc;
}

/*
** Return the total number of pages in the disk file associated with
** pPager. 
**
................................................................................
** PENDING_BYTE is byte 4096 (the first byte of page 5) and the size of the
** file is 4096 bytes, 5 is returned instead of 4.
*/
int sqlite3PagerPagecount(Pager *pPager, int *pnPage){
  i64 n = 0;
  int rc;
  assert( pPager!=0 );

  if( pPager->errCode ){
    return pPager->errCode;


  }
  if( pPager->dbSize>=0 ){
    n = pPager->dbSize;
  } else {
    assert(pPager->fd->pMethods||pPager->tempFile);
    if( (pPager->fd->pMethods)
     && (rc = sqlite3OsFileSize(pPager->fd, &n))!=SQLITE_OK ){
      pPager->nRef++;
      pager_error(pPager, rc);
      pPager->nRef--;

      return rc;
    }
    if( n>0 && n<pPager->pageSize ){
      n = 1;
    }else{
      n /= pPager->pageSize;
    }
................................................................................
  }
  if( n>pPager->mxPgno ){
    pPager->mxPgno = n;
  }
  if( pnPage ){
    *pnPage = n;
  }

  return SQLITE_OK;
}


#ifndef SQLITE_OMIT_MEMORYDB
/*
** Clear a PgHistory block
*/
static void clearHistory(PgHistory *pHist){
  sqlite3PageFree(pHist->pOrig);
  sqlite3PageFree(pHist->pStmt);
  pHist->pOrig = 0;
  pHist->pStmt = 0;
}
#else
#define clearHistory(x)
#endif

/*
** Forward declaration
*/
static int syncJournal(Pager*);

/*
** Unlink pPg from its hash chain. Also set the page number to 0 to indicate
** that the page is not part of any hash chain. This is required because the
** sqlite3PagerMovepage() routine can leave a page in the 
** pNextFree/pPrevFree list that is not a part of any hash-chain.
*/
static void unlinkHashChain(Pager *pPager, PgHdr *pPg){
  if( pPg->pgno==0 ){
    assert( pPg->pNextHash==0 && pPg->pPrevHash==0 );
    return;
  }
  if( pPg->pNextHash ){
    pPg->pNextHash->pPrevHash = pPg->pPrevHash;
  }
  if( pPg->pPrevHash ){
    assert( pPager->aHash[pPg->pgno & (pPager->nHash-1)]!=pPg );
    pPg->pPrevHash->pNextHash = pPg->pNextHash;
  }else{
    int h = pPg->pgno & (pPager->nHash-1);
    pPager->aHash[h] = pPg->pNextHash;
  }
  if( MEMDB ){
    clearHistory(PGHDR_TO_HIST(pPg, pPager));
  }
  pPg->pgno = 0;
  pPg->pNextHash = pPg->pPrevHash = 0;
}

/*
** Unlink a page from the free list (the list of all pages where nRef==0)
** and from its hash collision chain.
*/
static void unlinkPage(PgHdr *pPg){
  Pager *pPager = pPg->pPager;

  /* Unlink from free page list */
  lruListRemove(pPg);

  /* Unlink from the pgno hash table */
  unlinkHashChain(pPager, pPg);
}

/*
** This routine is used to truncate the cache when a database
** is truncated.  Drop from the cache all pages whose pgno is
** larger than pPager->dbSize and is unreferenced.
**
** Referenced pages larger than pPager->dbSize are zeroed.
**
** Actually, at the point this routine is called, it would be
** an error to have a referenced page.  But rather than delete
** that page and guarantee a subsequent segfault, it seems better
** to zero it and hope that we error out sanely.
*/
static void pager_truncate_cache(Pager *pPager){
  PgHdr *pPg;
  PgHdr **ppPg;
  int dbSize = pPager->dbSize;

  ppPg = &pPager->pAll;
  while( (pPg = *ppPg)!=0 ){
    if( pPg->pgno<=dbSize ){
      ppPg = &pPg->pNextAll;
    }else if( pPg->nRef>0 ){
      memset(PGHDR_TO_DATA(pPg), 0, pPager->pageSize);
      ppPg = &pPg->pNextAll;
    }else{
      *ppPg = pPg->pNextAll;
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
      if( *ppPg ){
        (*ppPg)->pPrevAll = pPg->pPrevAll;
      }
#endif
      IOTRACE(("PGFREE %p %d\n", pPager, pPg->pgno));
      PAGER_INCR(sqlite3_pager_pgfree_count);
      unlinkPage(pPg);
      makeClean(pPg);
      sqlite3PageFree(pPg->pData);
      sqlite3_free(pPg);
      pPager->nPage--;
    }
  }
}

/*
** Try to obtain a lock on a file.  Invoke the busy callback if the lock
** is currently not available.  Repeat until the busy callback returns
** false or until the lock succeeds.
**
................................................................................
  return rc;
}

/*
** Truncate the file to the number of pages specified.
*/
int sqlite3PagerTruncate(Pager *pPager, Pgno nPage){
  int rc;
  assert( pPager->state>=PAGER_SHARED || MEMDB );



  sqlite3PagerPagecount(pPager, 0);
  if( pPager->errCode ){
    rc = pPager->errCode;
    return rc;
  }
  if( nPage>=(unsigned)pPager->dbSize ){
    return SQLITE_OK;
  }
  if( MEMDB ){
    pPager->dbSize = nPage;
    pager_truncate_cache(pPager);
    return SQLITE_OK;
  }
  pagerEnter(pPager);

  rc = syncJournal(pPager);
  pagerLeave(pPager);
  if( rc!=SQLITE_OK ){
    return rc;
  }

  /* Get an exclusive lock on the database before truncating. */
  pagerEnter(pPager);
  rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
  pagerLeave(pPager);

  if( rc!=SQLITE_OK ){
    return rc;

  }

  rc = pager_truncate(pPager, nPage);



  return rc;
}

/*
** Shutdown the page cache.  Free all memory and close all files.
**
** If a transaction was in progress when this routine is called, that
................................................................................
**
** This function always succeeds. If a transaction is active an attempt
** is made to roll it back. If an error occurs during the rollback 
** a hot journal may be left in the filesystem but no error is returned
** to the caller.
*/
int sqlite3PagerClose(Pager *pPager){
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
  if( !MEMDB ){
#ifndef SQLITE_MUTEX_NOOP
    sqlite3_mutex *mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM2);
#endif
    sqlite3_mutex_enter(mutex);
    if( pPager->pPrev ){
      pPager->pPrev->pNext = pPager->pNext;
    }else{
      sqlite3PagerList = pPager->pNext;
    }
    if( pPager->pNext ){
      pPager->pNext->pPrev = pPager->pPrev;
    }
    sqlite3_mutex_leave(mutex);
  }
#endif

  disable_simulated_io_errors();
  sqlite3BeginBenignMalloc();
  pPager->errCode = 0;
  pPager->exclusiveMode = 0;
  pager_reset(pPager);
  pagerUnlockAndRollback(pPager);
................................................................................
  sqlite3OsClose(pPager->fd);
  /* Temp files are automatically deleted by the OS
  ** if( pPager->tempFile ){
  **   sqlite3OsDelete(pPager->zFilename);
  ** }
  */

  sqlite3_free(pPager->aHash);
  sqlite3PageFree(pPager->pTmpSpace);

  sqlite3_free(pPager);
  return SQLITE_OK;
}

#if !defined(NDEBUG) || defined(SQLITE_TEST)
/*
** Return the page number for the given page data.
*/
Pgno sqlite3PagerPagenumber(DbPage *p){
  return p->pgno;
}
#endif

/*
** The page_ref() function increments the reference count for a page.
** If the page is currently on the freelist (the reference count is zero) then
** remove it from the freelist.
**
** For non-test systems, page_ref() is a macro that calls _page_ref()
** online of the reference count is zero.  For test systems, page_ref()
** is a real function so that we can set breakpoints and trace it.
*/
static void _page_ref(PgHdr *pPg){
  if( pPg->nRef==0 ){
    /* The page is currently on the freelist.  Remove it. */
    lruListRemove(pPg);
    pPg->pPager->nRef++;
  }
  pPg->nRef++;
}
#ifdef SQLITE_DEBUG
  static void page_ref(PgHdr *pPg){
    if( pPg->nRef==0 ){
      _page_ref(pPg);
    }else{
      pPg->nRef++;
    }
  }
#else
# define page_ref(P)   ((P)->nRef==0?_page_ref(P):(void)(P)->nRef++)
#endif

/*
** Increment the reference count for a page.  The input pointer is
** a reference to the page data.
*/
int sqlite3PagerRef(DbPage *pPg){
  pagerEnter(pPg->pPager);
  page_ref(pPg);
  pagerLeave(pPg->pPager);
  return SQLITE_OK;
}

/*
** Sync the journal.  In other words, make sure all the pages that have
** been written to the journal have actually reached the surface of the
................................................................................
** file. In this case all that is required is to update the nRec field in
** the journal header.
**
** This routine clears the needSync field of every page current held in
** memory.
*/
static int syncJournal(Pager *pPager){
  PgHdr *pPg;
  int rc = SQLITE_OK;

  /* Sync the journal before modifying the main database
  ** (assuming there is a journal and it needs to be synced.)
  */
  if( pPager->needSync ){
    if( !pPager->tempFile ){
................................................................................
      }
      pPager->journalStarted = 1;
    }
    pPager->needSync = 0;

    /* Erase the needSync flag from every page.
    */
    for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
      pPg->needSync = 0;
    }
    lruListSetFirstSynced(pPager);
  }

#ifndef NDEBUG
  /* If the Pager.needSync flag is clear then the PgHdr.needSync
  ** flag must also be clear for all pages.  Verify that this
  ** invariant is true.
  */
  else{
    for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
      assert( pPg->needSync==0 );
    }

    assert( pPager->lru.pFirstSynced==pPager->lru.pFirst );
  }
#endif

  return rc;
}

/*
** Merge two lists of pages connected by pDirty and in pgno order.
** Do not both fixing the pPrevDirty pointers.
*/
static PgHdr *merge_pagelist(PgHdr *pA, PgHdr *pB){
  PgHdr result, *pTail;
  pTail = &result;
  while( pA && pB ){
    if( pA->pgno<pB->pgno ){
      pTail->pDirty = pA;
      pTail = pA;
      pA = pA->pDirty;
    }else{
      pTail->pDirty = pB;
      pTail = pB;
      pB = pB->pDirty;
    }
  }
  if( pA ){
    pTail->pDirty = pA;
  }else if( pB ){
    pTail->pDirty = pB;
  }else{
    pTail->pDirty = 0;
  }
  return result.pDirty;
}

/*
** Sort the list of pages in accending order by pgno.  Pages are
** connected by pDirty pointers.  The pPrevDirty pointers are
** corrupted by this sort.
*/
#define N_SORT_BUCKET_ALLOC 25
#define N_SORT_BUCKET       25
#ifdef SQLITE_TEST
  int sqlite3_pager_n_sort_bucket = 0;
  #undef N_SORT_BUCKET
  #define N_SORT_BUCKET \
   (sqlite3_pager_n_sort_bucket?sqlite3_pager_n_sort_bucket:N_SORT_BUCKET_ALLOC)
#endif
static PgHdr *sort_pagelist(PgHdr *pIn){
  PgHdr *a[N_SORT_BUCKET_ALLOC], *p;
  int i;
  memset(a, 0, sizeof(a));
  while( pIn ){
    p = pIn;
    pIn = p->pDirty;
    p->pDirty = 0;
    for(i=0; i<N_SORT_BUCKET-1; i++){
      if( a[i]==0 ){
        a[i] = p;
        break;
      }else{
        p = merge_pagelist(a[i], p);
        a[i] = 0;
      }
    }
    if( i==N_SORT_BUCKET-1 ){
      /* Coverage: To get here, there need to be 2^(N_SORT_BUCKET) 
      ** elements in the input list. This is possible, but impractical.
      ** Testing this line is the point of global variable
      ** sqlite3_pager_n_sort_bucket.
      */
      a[i] = merge_pagelist(a[i], p);
    }
  }
  p = a[0];
  for(i=1; i<N_SORT_BUCKET; i++){
    p = merge_pagelist(p, a[i]);
  }
  return p;
}

/*
** Given a list of pages (connected by the PgHdr.pDirty pointer) write
** every one of those pages out to the database file and mark them all
** as clean.
*/
static int pager_write_pagelist(PgHdr *pList){
  Pager *pPager;
  PgHdr *p;
  int rc;

  if( pList==0 ) return SQLITE_OK;
  pPager = pList->pPager;

  /* At this point there may be either a RESERVED or EXCLUSIVE lock on the
  ** database file. If there is already an EXCLUSIVE lock, the following
................................................................................
  ** will require a journal playback.
  */
  rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
  if( rc!=SQLITE_OK ){
    return rc;
  }

  pList = sort_pagelist(pList);
  for(p=pList; p; p=p->pDirty){
    assert( p->dirty );
    p->dirty = 0;
  }
  while( pList ){

    /* If the file has not yet been opened, open it now. */
    if( !pPager->fd->pMethods ){
      assert(pPager->tempFile);
      rc = sqlite3PagerOpentemp(pPager, pPager->fd, pPager->vfsFlags);
      if( rc ) return rc;
................................................................................
    /* If there are dirty pages in the page cache with page numbers greater
    ** than Pager.dbSize, this means sqlite3PagerTruncate() was called to
    ** make the file smaller (presumably by auto-vacuum code). Do not write
    ** any such pages to the file.
    */
    if( pList->pgno<=pPager->dbSize ){
      i64 offset = (pList->pgno-1)*(i64)pPager->pageSize;
      char *pData = CODEC2(pPager, PGHDR_TO_DATA(pList), pList->pgno, 6);
      PAGERTRACE4("STORE %d page %d hash(%08x)\n",
                   PAGERID(pPager), pList->pgno, pager_pagehash(pList));
      IOTRACE(("PGOUT %p %d\n", pPager, pList->pgno));
      rc = sqlite3OsWrite(pPager->fd, pData, pPager->pageSize, offset);
      PAGER_INCR(sqlite3_pager_writedb_count);
      PAGER_INCR(pPager->nWrite);
      if( pList->pgno==1 ){
................................................................................
      PAGERTRACE3("NOSTORE %d page %d\n", PAGERID(pPager), pList->pgno);
    }
#endif
    if( rc ) return rc;
#ifdef SQLITE_CHECK_PAGES
    pList->pageHash = pager_pagehash(pList);
#endif

    pList = pList->pDirty;
  }


  return SQLITE_OK;
}

/*
** Collect every dirty page into a dirty list and
** return a pointer to the head of that list.  All pages are
** collected even if they are still in use.





*/
static PgHdr *pager_get_all_dirty_pages(Pager *pPager){





#ifndef NDEBUG
  /* Verify the sanity of the dirty list when we are running
  ** in debugging mode.  This is expensive, so do not
  ** do this on a normal build. */
  int n1 = 0;
  int n2 = 0;
  PgHdr *p;
  for(p=pPager->pAll; p; p=p->pNextAll){ if( p->dirty ) n1++; }
  for(p=pPager->pDirty; p; p=p->pDirty){ n2++; }
  assert( n1==n2 );
#endif















  return pPager->pDirty;
}


/*
** Return 1 if there is a hot journal on the given pager.
** A hot journal is one that needs to be played back.
**
** If the current size of the database file is 0 but a journal file
** exists, that is probably an old journal left over from a prior
................................................................................
      }
    }
  }

  return rc;
}

/*
** Try to find a page in the cache that can be recycled. 
**
** This routine may return SQLITE_IOERR, SQLITE_FULL or SQLITE_OK. It 
** does not set the pPager->errCode variable.
*/
static int pager_recycle(Pager *pPager, PgHdr **ppPg){
  PgHdr *pPg;
  *ppPg = 0;

  /* It is illegal to call this function unless the pager object
  ** pointed to by pPager has at least one free page (page with nRef==0).
  */ 
  assert(!MEMDB);
  assert(pPager->lru.pFirst);

  /* Find a page to recycle.  Try to locate a page that does not
  ** require us to do an fsync() on the journal.
  */
  pPg = pPager->lru.pFirstSynced;

  /* If we could not find a page that does not require an fsync()
  ** on the journal file then fsync the journal file.  This is a
  ** very slow operation, so we work hard to avoid it.  But sometimes
  ** it can't be helped.
  */
  if( pPg==0 && pPager->lru.pFirst ){
    if( !pPager->errCode ){
      int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
      int rc = syncJournal(pPager);
      if( rc!=0 ){
        return rc;
      }
      if( pPager->fullSync && 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){
        /* If in full-sync mode, write a new journal header into the
        ** journal file. This is done to avoid ever modifying a journal
        ** header that is involved in the rollback of pages that have
        ** already been written to the database (in case the header is
        ** trashed when the nRec field is updated).
        */
        pPager->nRec = 0;
        assert( pPager->journalOff > 0 );
        assert( pPager->doNotSync==0 );
        rc = writeJournalHdr(pPager);
        if( rc!=0 ){
          return rc;
        }
      }
    }
    pPg = pPager->lru.pFirst;
  }

  assert( pPg->nRef==0 );

  /* Write the page to the database file if it is dirty.
  */
  if( pPg->dirty && !pPager->errCode ){
    int rc;
    assert( pPg->needSync==0 );
    makeClean(pPg);
    pPg->dirty = 1;
    pPg->pDirty = 0;
    rc = pager_write_pagelist( pPg );
    pPg->dirty = 0;
    if( rc!=SQLITE_OK ){
      return rc;
    }
  }
  assert( pPg->dirty==0 || pPager->errCode );

  /* If the page we are recycling is marked as alwaysRollback, then
  ** set the global alwaysRollback flag, thus disabling the
  ** sqlite3PagerDontRollback() optimization for the rest of this transaction.
  ** It is necessary to do this because the page marked alwaysRollback
  ** might be reloaded at a later time but at that point we won't remember
  ** that is was marked alwaysRollback.  This means that all pages must
  ** be marked as alwaysRollback from here on out.
  */
  if( pPg->alwaysRollback ){
    IOTRACE(("ALWAYS_ROLLBACK %p\n", pPager))
    pPager->alwaysRollback = 1;
  }

  /* Unlink the old page from the free list and the hash table
  */
  unlinkPage(pPg);
  assert( pPg->pgno==0 );

  *ppPg = pPg;
  return SQLITE_OK;
}

#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
/*
** This function is called to free superfluous dynamically allocated memory
** held by the pager system. Memory in use by any SQLite pager allocated
** by the current thread may be sqlite3_free()ed.
**
** nReq is the number of bytes of memory required. Once this much has
** been released, the function returns. The return value is the total number 
** of bytes of memory released.
*/
int sqlite3PagerReleaseMemory(int nReq){
  int nReleased = 0;          /* Bytes of memory released so far */
  Pager *pPager;              /* For looping over pagers */
  BusyHandler *savedBusy;     /* Saved copy of the busy handler */
  int rc = SQLITE_OK;

  /* Acquire the memory-management mutex
  */
#ifndef SQLITE_MUTEX_NOOP
  sqlite3_mutex *mutex;       /* The MEM2 mutex */
  mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM2);
#endif
  sqlite3_mutex_enter(mutex);

  /* Signal all database connections that memory management wants
  ** to have access to the pagers.
  */
  for(pPager=sqlite3PagerList; pPager; pPager=pPager->pNext){
     pPager->iInUseMM = 1;
  }

  while( rc==SQLITE_OK && (nReq<0 || nReleased<nReq) ){
    PgHdr *pPg;
    PgHdr *pRecycled;
 
    /* Try to find a page to recycle that does not require a sync(). If
    ** this is not possible, find one that does require a sync().
    */
    sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_LRU));
    pPg = sqlite3LruPageList.pFirstSynced;
    while( pPg && (pPg->needSync || pPg->pPager->iInUseDB) ){
      pPg = pPg->gfree.pNext;
    }
    if( !pPg ){
      pPg = sqlite3LruPageList.pFirst;
      while( pPg && pPg->pPager->iInUseDB ){
        pPg = pPg->gfree.pNext;
      }
    }
    sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_LRU));

    /* If pPg==0, then the block above has failed to find a page to
    ** recycle. In this case return early - no further memory will
    ** be released.
    */
    if( !pPg ) break;

    pPager = pPg->pPager;
    assert(!pPg->needSync || pPg==pPager->lru.pFirst);
    assert(pPg->needSync || pPg==pPager->lru.pFirstSynced);
  
    savedBusy = pPager->pBusyHandler;
    pPager->pBusyHandler = 0;
    rc = pager_recycle(pPager, &pRecycled);
    pPager->pBusyHandler = savedBusy;
    assert(pRecycled==pPg || rc!=SQLITE_OK);
    if( rc==SQLITE_OK ){
      /* We've found a page to free. At this point the page has been 
      ** removed from the page hash-table, free-list and synced-list 
      ** (pFirstSynced). It is still in the all pages (pAll) list. 
      ** Remove it from this list before freeing.
      **
      ** Todo: Check the Pager.pStmt list to make sure this is Ok. It 
      ** probably is though.
      */
      PgHdr *pTmp;
      assert( pPg );
      if( pPg==pPager->pAll ){
         assert(pPg->pPrevAll==0);
         assert(pPg->pNextAll==0 || pPg->pNextAll->pPrevAll==pPg);
         pPager->pAll = pPg->pNextAll;
         if( pPager->pAll ){
           pPager->pAll->pPrevAll = 0;
         }
      }else{
         assert(pPg->pPrevAll);
         assert(pPg->pPrevAll->pNextAll==pPg);
         pTmp = pPg->pPrevAll;
         pTmp->pNextAll = pPg->pNextAll;
         if( pTmp->pNextAll ){
           pTmp->pNextAll->pPrevAll = pTmp;
         }
      }
      nReleased += (
          sizeof(*pPg) + pPager->pageSize
          + sizeof(u32) + pPager->nExtra
          + MEMDB*sizeof(PgHistory) 
      );
      IOTRACE(("PGFREE %p %d *\n", pPager, pPg->pgno));
      PAGER_INCR(sqlite3_pager_pgfree_count);
      sqlite3PageFree(pPg->pData);
      sqlite3_free(pPg);
      pPager->nPage--;
    }else{
      /* An error occured whilst writing to the database file or 
      ** journal in pager_recycle(). The error is not returned to the 
      ** caller of this function. Instead, set the Pager.errCode variable.
      ** The error will be returned to the user (or users, in the case 
      ** of a shared pager cache) of the pager for which the error occured.
      */
      assert(
          (rc&0xff)==SQLITE_IOERR ||
          rc==SQLITE_FULL ||
          rc==SQLITE_BUSY
      );
      assert( pPager->state>=PAGER_RESERVED );
      pager_error(pPager, rc);
    }
  }

  /* Clear the memory management flags and release the mutex
  */
  for(pPager=sqlite3PagerList; pPager; pPager=pPager->pNext){
     pPager->iInUseMM = 0;
  }
  sqlite3_mutex_leave(mutex);

  /* Return the number of bytes released
  */
  return nReleased;
}
#endif /* SQLITE_ENABLE_MEMORY_MANAGEMENT */

/*
** Read the content of page pPg out of the database file.
*/
static int readDbPage(Pager *pPager, PgHdr *pPg, Pgno pgno){
................................................................................
  i64 offset;
  assert( MEMDB==0 );
  assert(pPager->fd->pMethods||pPager->tempFile);
  if( !pPager->fd->pMethods ){
    return SQLITE_IOERR_SHORT_READ;
  }
  offset = (pgno-1)*(i64)pPager->pageSize;
  rc = sqlite3OsRead(pPager->fd, PGHDR_TO_DATA(pPg), pPager->pageSize, offset);
  PAGER_INCR(sqlite3_pager_readdb_count);
  PAGER_INCR(pPager->nRead);
  IOTRACE(("PGIN %p %d\n", pPager, pgno));
  if( pgno==1 ){
    memcpy(&pPager->dbFileVers, &((u8*)PGHDR_TO_DATA(pPg))[24],
                                              sizeof(pPager->dbFileVers));
  }
  CODEC1(pPager, PGHDR_TO_DATA(pPg), pPg->pgno, 3);
  PAGERTRACE4("FETCH %d page %d hash(%08x)\n",
               PAGERID(pPager), pPg->pgno, pager_pagehash(pPg));
  return rc;
}
................................................................................
  int isErrorReset = 0;

  /* If this database is opened for exclusive access, has no outstanding 
  ** page references and is in an error-state, now is the chance to clear
  ** the error. Discard the contents of the pager-cache and treat any
  ** open journal file as a hot-journal.
  */
  if( !MEMDB && pPager->exclusiveMode && pPager->nRef==0 && pPager->errCode ){


    if( pPager->journalOpen ){
      isErrorReset = 1;
    }
    pPager->errCode = SQLITE_OK;
    pager_reset(pPager);
  }

................................................................................
    return pPager->errCode;
  }

  if( pPager->state==PAGER_UNLOCK || isErrorReset ){
    sqlite3_vfs *pVfs = pPager->pVfs;
    if( !MEMDB ){
      int isHotJournal;
      assert( pPager->nRef==0 );
      if( !pPager->noReadlock ){
        rc = pager_wait_on_lock(pPager, SHARED_LOCK);
        if( rc!=SQLITE_OK ){
          assert( pPager->state==PAGER_UNLOCK );
          return pager_error(pPager, rc);
        }
        assert( pPager->state>=SHARED_LOCK );
................................................................................
          goto failed;
        }
        assert(pPager->state==PAGER_SHARED || 
            (pPager->exclusiveMode && pPager->state>PAGER_SHARED)
        );
      }

      if( pPager->pAll ){
        /* The shared-lock has just been acquired on the database file
        ** and there are already pages in the cache (from a previous
        ** read or write transaction).  Check to see if the database
        ** has been modified.  If the database has changed, flush the
        ** cache.
        **
        ** Database changes is detected by looking at 15 bytes beginning
................................................................................
  if( rc!=SQLITE_OK ){
    /* pager_unlock() is a no-op for exclusive mode and in-memory databases. */
    pager_unlock(pPager);
  }
  return rc;
}

/*
** Allocate a PgHdr object.   Either create a new one or reuse
** an existing one that is not otherwise in use.
**
** A new PgHdr structure is created if any of the following are
** true:
**
**     (1)  We have not exceeded our maximum allocated cache size
**          as set by the "PRAGMA cache_size" command.
**
**     (2)  There are no unused PgHdr objects available at this time.
**
**     (3)  This is an in-memory database.
**
**     (4)  There are no PgHdr objects that do not require a journal
**          file sync and a sync of the journal file is currently
**          prohibited.
**
** Otherwise, reuse an existing PgHdr.  In other words, reuse an
** existing PgHdr if all of the following are true:
**
**     (1)  We have reached or exceeded the maximum cache size
**          allowed by "PRAGMA cache_size".
**
**     (2)  There is a PgHdr available with PgHdr->nRef==0
**
**     (3)  We are not in an in-memory database
**
**     (4)  Either there is an available PgHdr that does not need
**          to be synced to disk or else disk syncing is currently
**          allowed.
*/
static int pagerAllocatePage(Pager *pPager, PgHdr **ppPg){
  int rc = SQLITE_OK;
  PgHdr *pPg;
  int nByteHdr;

  /* Create a new PgHdr if any of the four conditions defined 
  ** above are met: */
  if( pPager->nPage<pPager->mxPage
   || pPager->lru.pFirst==0 
   || MEMDB
   || (pPager->lru.pFirstSynced==0 && pPager->doNotSync)
  ){
    void *pData;
    if( pPager->nPage>=pPager->nHash ){
      pager_resize_hash_table(pPager,
         pPager->nHash<256 ? 256 : pPager->nHash*2);
      if( pPager->nHash==0 ){
        rc = SQLITE_NOMEM;
        goto pager_allocate_out;
      }
    }
    pagerLeave(pPager);
    nByteHdr = sizeof(*pPg) + sizeof(u32) + pPager->nExtra
              + MEMDB*sizeof(PgHistory);
    pPg = sqlite3Malloc( nByteHdr );
    if( pPg ){
      pData = sqlite3PageMalloc( pPager->pageSize );
      if( pData==0 ){
        sqlite3_free(pPg);
        pPg = 0;
      }
    }
    pagerEnter(pPager);
    if( pPg==0 ){
      rc = SQLITE_NOMEM;
      goto pager_allocate_out;
    }
    memset(pPg, 0, nByteHdr);
    pPg->pData = pData;
    pPg->pPager = pPager;
    pPg->pNextAll = pPager->pAll;
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
    if( pPg->pNextAll ){
      pPg->pNextAll->pPrevAll = pPg;
    }
#endif
    pPager->pAll = pPg;
    pPager->nPage++;
  }else{
    /* Recycle an existing page with a zero ref-count. */
    rc = pager_recycle(pPager, &pPg);
    if( rc==SQLITE_BUSY ){
      rc = SQLITE_IOERR_BLOCKED;
    }
    if( rc!=SQLITE_OK ){
      goto pager_allocate_out;
    }
    assert( pPager->state>=SHARED_LOCK );
    assert(pPg);
  }
  *ppPg = pPg;

pager_allocate_out:
  return rc;
}

/*
** Make sure we have the content for a page.  If the page was
** previously acquired with noContent==1, then the content was
** just initialized to zeros instead of being read from disk.
** But now we need the real data off of disk.  So make sure we
** have it.  Read it in if we do not have it already.
*/
static int pager_get_content(PgHdr *pPg){
  if( pPg->needRead ){

    int rc = readDbPage(pPg->pPager, pPg, pPg->pgno);
    if( rc==SQLITE_OK ){
      pPg->needRead = 0;

    }else{
      return rc;
    }
  }
  return SQLITE_OK;
}

























/*
** Acquire a page.
**
** A read lock on the disk file is obtained when the first page is acquired. 
** This read lock is dropped when the last page is released.
**
................................................................................
*/
static int pagerAcquire(
  Pager *pPager,      /* The pager open on the database file */
  Pgno pgno,          /* Page number to fetch */
  DbPage **ppPage,    /* Write a pointer to the page here */
  int noContent       /* Do not bother reading content from disk if true */
){
  PgHdr *pPg;
  int rc;

  assert( pPager->state==PAGER_UNLOCK || pPager->nRef>0 || pgno==1 );




  /* The maximum page number is 2^31. Return SQLITE_CORRUPT if a page
  ** number greater than this, or zero, is requested.
  */
  if( pgno>PAGER_MAX_PGNO || pgno==0 || pgno==PAGER_MJ_PGNO(pPager) ){
    return SQLITE_CORRUPT_BKPT;
  }
................................................................................
  */
  rc = pagerSharedLock(pPager);
  if( rc!=SQLITE_OK ){
    return rc;
  }
  assert( pPager->state!=PAGER_UNLOCK );

  pPg = pager_lookup(pPager, pgno);
  if( pPg==0 ){
    /* The requested page is not in the page cache. */
    int nMax;
    int h;
    PAGER_INCR(pPager->nMiss);
    rc = pagerAllocatePage(pPager, &pPg);
    if( rc!=SQLITE_OK ){
      return rc;
    }




    pPg->pgno = pgno;




    assert( !MEMDB || pgno>pPager->stmtSize );



    pPg->inJournal = sqlite3BitvecTest(pPager->pInJournal, pgno);
    pPg->needSync = 0;

    makeClean(pPg);
    pPg->nRef = 1;

    pPager->nRef++;
    if( pPager->nExtra>0 ){
      memset(PGHDR_TO_EXTRA(pPg, pPager), 0, pPager->nExtra);
    }
    rc = sqlite3PagerPagecount(pPager, &nMax);
    if( rc!=SQLITE_OK ){
      sqlite3PagerUnref(pPg);
      return rc;
    }

    /* Populate the page with data, either by reading from the database
    ** file, or by setting the entire page to zero.
    */
    if( nMax<(int)pgno || MEMDB || (noContent && !pPager->alwaysRollback) ){
      if( pgno>pPager->mxPgno ){
        sqlite3PagerUnref(pPg);
        return SQLITE_FULL;
      }
      memset(PGHDR_TO_DATA(pPg), 0, pPager->pageSize);
      pPg->needRead = noContent && !pPager->alwaysRollback;


      IOTRACE(("ZERO %p %d\n", pPager, pgno));
    }else{
      rc = readDbPage(pPager, pPg, pgno);
      if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){
        pPg->pgno = 0;
        sqlite3PagerUnref(pPg);

        return rc;
      }
      pPg->needRead = 0;
    }

    /* Link the page into the page hash table */
    h = pgno & (pPager->nHash-1);
    assert( pgno!=0 );
    pPg->pNextHash = pPager->aHash[h];
    pPager->aHash[h] = pPg;
    if( pPg->pNextHash ){
      assert( pPg->pNextHash->pPrevHash==0 );
      pPg->pNextHash->pPrevHash = pPg;
    }

#ifdef SQLITE_CHECK_PAGES
    pPg->pageHash = pager_pagehash(pPg);
#endif
  }else{
    /* The requested page is in the page cache. */
    assert(pPager->nRef>0 || pgno==1);
    PAGER_INCR(pPager->nHit);
    if( !noContent ){
      rc = pager_get_content(pPg);
      if( rc ){

        return rc;
      }
    }
    page_ref(pPg);
  }

  *ppPage = pPg;
  return SQLITE_OK;
}

int sqlite3PagerAcquire(
  Pager *pPager,      /* The pager open on the database file */
  Pgno pgno,          /* Page number to fetch */
  DbPage **ppPage,    /* Write a pointer to the page here */
  int noContent       /* Do not bother reading content from disk if true */
){
  int rc;
................................................................................
** and sqlite3PagerGet() is that _get() will go to the disk and read
** in the page if the page is not already in cache.  This routine
** returns NULL if the page is not in cache or if a disk I/O error 
** has ever happened.
*/
DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){
  PgHdr *pPg = 0;

  assert( pPager!=0 );
  assert( pgno!=0 );

  pagerEnter(pPager);
  if( pPager->state==PAGER_UNLOCK ){
    assert( !pPager->pAll || pPager->exclusiveMode );
  }else if( pPager->errCode && pPager->errCode!=SQLITE_FULL ){
    /* Do nothing */
  }else if( (pPg = pager_lookup(pPager, pgno))!=0 ){
    page_ref(pPg);
  }
  pagerLeave(pPager);

  return pPg;
}

/*
** Release a page.
**
** If the number of references to the page drop to zero, then the
** page is added to the LRU list.  When all references to all pages
** are released, a rollback occurs and the lock on the database is
** removed.
*/
int sqlite3PagerUnref(DbPage *pPg){
  Pager *pPager;

  if( pPg==0 ) return SQLITE_OK;
  pPager = pPg->pPager;

  /* Decrement the reference count for this page
  */
  assert( pPg->nRef>0 );
  pagerEnter(pPg->pPager);
  pPg->nRef--;

  CHECK_PAGE(pPg);

  /* When the number of references to a page reach 0, call the
  ** destructor and add the page to the freelist.
  */
  if( pPg->nRef==0 ){

    lruListAdd(pPg);
    if( pPager->xDestructor ){
      pPager->xDestructor(pPg, pPager->pageSize);
    }
  
    /* When all pages reach the freelist, drop the read lock from
    ** the database file.
    */
    pPager->nRef--;
    assert( pPager->nRef>=0 );
    if( pPager->nRef==0 && (!pPager->exclusiveMode || pPager->journalOff>0) ){

      pagerUnlockAndRollback(pPager);
    }
  }
  pagerLeave(pPager);

  return SQLITE_OK;
}

/*
** Create a journal file for pPager.  There should already be a RESERVED
** or EXCLUSIVE lock on the database file when this routine is called.
**
................................................................................
  Pager *pPager = pPg->pPager;
  int rc = SQLITE_OK;
  pagerEnter(pPager);
  assert( pPg->nRef>0 );
  assert( pPager->state!=PAGER_UNLOCK );
  if( pPager->state==PAGER_SHARED ){
    assert( pPager->pInJournal==0 );

    if( MEMDB ){
      pPager->state = PAGER_EXCLUSIVE;
      pPager->origDbSize = pPager->dbSize;
    }else{
      rc = sqlite3OsLock(pPager->fd, RESERVED_LOCK);
      if( rc==SQLITE_OK ){
        pPager->state = PAGER_RESERVED;
................................................................................
    ** kept open and either was truncated to 0 bytes or its header was
    ** overwritten with zeros.
    */
    assert( pPager->nRec==0 );
    assert( pPager->origDbSize==0 );
    assert( pPager->pInJournal==0 );
    sqlite3PagerPagecount(pPager, 0);
    pagerLeave(pPager);
    pPager->pInJournal = sqlite3BitvecCreate( pPager->dbSize );
    pagerEnter(pPager);
    if( !pPager->pInJournal ){
      rc = SQLITE_NOMEM;
    }else{
      pPager->origDbSize = pPager->dbSize;
      rc = writeJournalHdr(pPager);
    }
  }
................................................................................
}

/*
** Make a page dirty.  Set its dirty flag and add it to the dirty
** page list.
*/
static void makeDirty(PgHdr *pPg){
  if( pPg->dirty==0 ){
    Pager *pPager = pPg->pPager;
    pPg->dirty = 1;
    pPg->pDirty = pPager->pDirty;
    if( pPager->pDirty ){
      pPager->pDirty->pPrevDirty = pPg;
    }
    pPg->pPrevDirty = 0;
    pPager->pDirty = pPg;
  }
}

/*
** Make a page clean.  Clear its dirty bit and remove it from the
** dirty page list.
*/
static void makeClean(PgHdr *pPg){
  if( pPg->dirty ){
    pPg->dirty = 0;
    if( pPg->pDirty ){
      assert( pPg->pDirty->pPrevDirty==pPg );
      pPg->pDirty->pPrevDirty = pPg->pPrevDirty;
    }
    if( pPg->pPrevDirty ){
      assert( pPg->pPrevDirty->pDirty==pPg );
      pPg->pPrevDirty->pDirty = pPg->pDirty;
    }else{
      assert( pPg->pPager->pDirty==pPg );
      pPg->pPager->pDirty = pPg->pDirty;
    }
  }
}


/*
** Mark a data page as writeable.  The page is written into the journal 
** if it is not there already.  This routine must be called before making
** changes to a page.
................................................................................
** If the journal file could not be written because the disk is full,
** then this routine returns SQLITE_FULL and does an immediate rollback.
** All subsequent write attempts also return SQLITE_FULL until there
** is a call to sqlite3PagerCommit() or sqlite3PagerRollback() to
** reset.
*/
static int pager_write(PgHdr *pPg){
  void *pData = PGHDR_TO_DATA(pPg);
  Pager *pPager = pPg->pPager;
  int rc = SQLITE_OK;

  /* Check for errors
  */
  if( pPager->errCode ){ 
    return pPager->errCode;
................................................................................
    return rc;
  }

  /* Mark the page as dirty.  If the page has already been written
  ** to the journal then we can return right away.
  */
  makeDirty(pPg);

  if( pPg->inJournal && (pageInStatement(pPg) || pPager->stmtInUse==0) ){

    pPager->dirtyCache = 1;
    pPager->dbModified = 1;
  }else{

    /* If we get this far, it means that the page needs to be
    ** written to the transaction journal or the ckeckpoint journal
    ** or both.
................................................................................
    pPager->dirtyCache = 1;
    pPager->dbModified = 1;
  
    /* The transaction journal now exists and we have a RESERVED or an
    ** EXCLUSIVE lock on the main database file.  Write the current page to
    ** the transaction journal if it is not there already.
    */
    if( !pPg->inJournal && (pPager->journalOpen || MEMDB) ){
      if( (int)pPg->pgno <= pPager->origDbSize ){
        if( MEMDB ){
          PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager);
          PAGERTRACE3("JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno);

          assert( pHist->pOrig==0 );
          pHist->pOrig = sqlite3PageMalloc( pPager->pageSize );
          if( !pHist->pOrig ){
            return SQLITE_NOMEM;
          }
          memcpy(pHist->pOrig, PGHDR_TO_DATA(pPg), pPager->pageSize);
        }else{
          u32 cksum;
          char *pData2;

          /* We should never write to the journal file the page that
          ** contains the database locks.  The following assert verifies
          ** that we do not. */
................................................................................
            rc = write32bits(pPager->jfd, pPager->journalOff, cksum);
            pPager->journalOff += 4;
          }
          IOTRACE(("JOUT %p %d %lld %d\n", pPager, pPg->pgno, 
                   pPager->journalOff, pPager->pageSize));
          PAGER_INCR(sqlite3_pager_writej_count);
          PAGERTRACE5("JOURNAL %d page %d needSync=%d hash(%08x)\n",
               PAGERID(pPager), pPg->pgno, pPg->needSync, pager_pagehash(pPg));


          /* An error has occured writing to the journal file. The 
          ** transaction will be rolled back by the layer above.
          */
          if( rc!=SQLITE_OK ){
            return rc;
          }

          pPager->nRec++;
          assert( pPager->pInJournal!=0 );
          sqlite3BitvecSet(pPager->pInJournal, pPg->pgno);
          pPg->needSync = !pPager->noSync;


          if( pPager->stmtInUse ){
            sqlite3BitvecSet(pPager->pInStmt, pPg->pgno);
          }
        }
      }else{
        pPg->needSync = !pPager->journalStarted && !pPager->noSync;


        PAGERTRACE4("APPEND %d page %d needSync=%d\n",
                PAGERID(pPager), pPg->pgno, pPg->needSync);

      }
      if( pPg->needSync ){

        pPager->needSync = 1;
      }
      pPg->inJournal = 1;

    }
  
    /* If the statement journal is open and the page is not in it,
    ** then write the current page to the statement journal.  Note that
    ** the statement journal format differs from the standard journal format
    ** in that it omits the checksums and the header.
    */
    if( pPager->stmtInUse 
     && !pageInStatement(pPg) 
     && (int)pPg->pgno<=pPager->stmtSize 
    ){

      assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize );
      if( MEMDB ){
        PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager);
        assert( pHist->pStmt==0 );
        pHist->pStmt = sqlite3PageMalloc( pPager->pageSize );
        if( pHist->pStmt ){
          memcpy(pHist->pStmt, PGHDR_TO_DATA(pPg), pPager->pageSize);
        }
        PAGERTRACE3("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno);
        page_add_to_stmt_list(pPg);
      }else{
        i64 offset = pPager->stmtNRec*(4+pPager->pageSize);
        char *pData2 = CODEC2(pPager, pData, pPg->pgno, 7);
        rc = write32bits(pPager->stfd, offset, pPg->pgno);
        if( rc==SQLITE_OK ){
          rc = sqlite3OsWrite(pPager->stfd, pData2, pPager->pageSize, offset+4);
        }
................................................................................
      Pgno pg = pg1+ii;
      PgHdr *pPage;
      if( pg==pPg->pgno || !sqlite3BitvecTest(pPager->pInJournal, pg) ){
        if( pg!=PAGER_MJ_PGNO(pPager) ){
          rc = sqlite3PagerGet(pPager, pg, &pPage);
          if( rc==SQLITE_OK ){
            rc = pager_write(pPage);
            if( pPage->needSync ){
              needSync = 1;
            }
            sqlite3PagerUnref(pPage);
          }
        }
      }else if( (pPage = pager_lookup(pPager, pg))!=0 ){
        if( pPage->needSync ){
          needSync = 1;
        }

      }
    }

    /* If the PgHdr.needSync flag is set for any of the nPage pages 
    ** starting at pg1, then it needs to be set for all of them. Because
    ** writing to any of these nPage pages may damage the others, the
    ** journal file must contain sync()ed copies of all of them
    ** before any of them can be written out to the database file.
    */
    if( needSync ){
      for(ii=0; ii<nPage && needSync; ii++){
        PgHdr *pPage = pager_lookup(pPager, pg1+ii);
        if( pPage ) pPage->needSync = 1;

      }
      assert(pPager->needSync);
    }

    assert( pPager->doNotSync==1 );
    pPager->doNotSync = 0;
  }else{
................................................................................
/*
** Return TRUE if the page given in the argument was previously passed
** to sqlite3PagerWrite().  In other words, return TRUE if it is ok
** to change the content of the page.
*/
#ifndef NDEBUG
int sqlite3PagerIswriteable(DbPage *pPg){
  return pPg->dirty;
}
#endif

/*
** A call to this routine tells the pager that it is not necessary to
** write the information on page pPg back to the disk, even though
** that page might be marked as dirty.
................................................................................
*/
void sqlite3PagerDontWrite(DbPage *pDbPage){
  PgHdr *pPg = pDbPage;
  Pager *pPager = pPg->pPager;

  if( MEMDB ) return;
  pagerEnter(pPager);
  pPg->alwaysRollback = 1;
  if( pPg->dirty && !pPager->stmtInUse ){
    assert( pPager->state>=PAGER_SHARED );
    if( pPager->dbSize==(int)pPg->pgno && pPager->origDbSize<pPager->dbSize ){
      /* If this pages is the last page in the file and the file has grown
      ** during the current transaction, then do NOT mark the page as clean.
      ** When the database file grows, we must make sure that the last page
      ** gets written at least once so that the disk file will be the correct
      ** size. If you do not write this page and the size of the file
................................................................................
  pagerEnter(pPager);
  assert( pPager->state>=PAGER_RESERVED );

  /* If the journal file is not open, or DontWrite() has been called on
  ** this page (DontWrite() sets the alwaysRollback flag), then this
  ** function is a no-op.
  */

  if( pPager->journalOpen==0 || pPg->alwaysRollback || pPager->alwaysRollback ){

    pagerLeave(pPager);
    return;
  }
  assert( !MEMDB );    /* For a memdb, pPager->journalOpen is always 0 */

#ifdef SQLITE_SECURE_DELETE
  if( pPg->inJournal || (int)pPg->pgno > pPager->origDbSize ){

    return;
  }
#endif

  /* If SECURE_DELETE is disabled, then there is no way that this
  ** routine can be called on a page for which sqlite3PagerDontWrite()
  ** has not been previously called during the same transaction.
................................................................................
  ** pages on the freelist (ex: corrupt9.test) then the following is not
  ** necessarily true:
  */
  /* assert( !pPg->inJournal && (int)pPg->pgno <= pPager->origDbSize ); */

  assert( pPager->pInJournal!=0 );
  sqlite3BitvecSet(pPager->pInJournal, pPg->pgno);
  pPg->inJournal = 1;
  pPg->needRead = 0;
  if( pPager->stmtInUse ){
    assert( pPager->stmtSize >= pPager->origDbSize );
    sqlite3BitvecSet(pPager->pInStmt, pPg->pgno);
  }
  PAGERTRACE3("DONT_ROLLBACK page %d of %d\n", pPg->pgno, PAGERID(pPager));
  IOTRACE(("GARBAGE %p %d\n", pPager, pPg->pgno))
  pagerLeave(pPager);
................................................................................
        return rc;
      }
    }

    /* Increment the value just read and write it back to byte 24. */
    change_counter = sqlite3Get4byte((u8*)pPager->dbFileVers);
    change_counter++;
    put32bits(((char*)PGHDR_TO_DATA(pPgHdr))+24, change_counter);

#ifdef SQLITE_ENABLE_ATOMIC_WRITE
    if( isDirect && pPager->fd->pMethods ){
      const void *zBuf = PGHDR_TO_DATA(pPgHdr);
      rc = sqlite3OsWrite(pPager->fd, zBuf, pPager->pageSize, 0);
    }
#endif

    /* Release the page reference. */
    sqlite3PagerUnref(pPgHdr);
    pPager->changeCountDone = 1;
................................................................................
    **      blocks of size page-size, and
    **    + This commit is not part of a multi-file transaction, and
    **    + Exactly one page has been modified and store in the journal file.
    **
    ** If the optimization can be used, then the journal file will never
    ** be created for this transaction.
    */

    int useAtomicWrite = (
        !zMaster && 
        pPager->journalOpen &&
        pPager->journalOff==jrnlBufferSize(pPager) && 
        nTrunc==0 && 
        (0==pPager->pDirty || 0==pPager->pDirty->pDirty)
    );
    assert( pPager->journalOpen || pPager->journalMode==PAGER_JOURNALMODE_OFF );
    if( useAtomicWrite ){
      /* Update the nRec field in the journal file. */
      int offset = pPager->journalHdr + sizeof(aJournalMagic);
      assert(pPager->nRec==1);
      rc = write32bits(pPager->jfd, offset, pPager->nRec);
................................................................................
    if( nTrunc!=0 ){
      rc = sqlite3PagerTruncate(pPager, nTrunc);
      if( rc!=SQLITE_OK ) goto sync_exit;
    }
#endif

    /* Write all dirty pages to the database file */
    pPg = pager_get_all_dirty_pages(pPager);
    rc = pager_write_pagelist(pPg);
    if( rc!=SQLITE_OK ){
      assert( rc!=SQLITE_IOERR_BLOCKED );
      /* The error might have left the dirty list all fouled up here,
      ** but that does not matter because if the if the dirty list did
      ** get corrupted, then the transaction will roll back and
      ** discard the dirty list.  There is an assert in
      ** pager_get_all_dirty_pages() that verifies that no attempt
      ** is made to use an invalid dirty list.
      */
      goto sync_exit;
    }
    pPager->pDirty = 0;

    /* Sync the database file. */
    if( !pPager->noSync && !noSync ){
      rc = sqlite3OsSync(pPager->fd, pPager->sync_flags);
    }
    IOTRACE(("DBSYNC %p\n", pPager))

................................................................................
** Commit all changes to the database and release the write lock.
**
** If the commit fails for any reason, a rollback attempt is made
** and an error code is returned.  If the commit worked, SQLITE_OK
** is returned.
*/
int sqlite3PagerCommitPhaseTwo(Pager *pPager){
  int rc;
  PgHdr *pPg;

  if( pPager->errCode ){
    return pPager->errCode;
  }
  if( pPager->state<PAGER_RESERVED ){
    return SQLITE_ERROR;
  }
................................................................................
          pPager->exclusiveMode!=0) ){
    assert( pPager->dirtyCache==0 || pPager->journalOpen==0 );
    return SQLITE_OK;
  }
  pagerEnter(pPager);
  PAGERTRACE2("COMMIT %d\n", PAGERID(pPager));
  if( MEMDB ){
    pPg = pager_get_all_dirty_pages(pPager);
    while( pPg ){
      PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager);
      clearHistory(pHist);
      pPg->dirty = 0;
      pPg->inJournal = 0;
      pHist->inStmt = 0;
      pPg->needSync = 0;
      pHist->pPrevStmt = pHist->pNextStmt = 0;
      pPg = pPg->pDirty;
    }
    pPager->pDirty = 0;
#ifndef NDEBUG
    for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
      PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager);
      assert( !pPg->alwaysRollback );
      assert( !pHist->pOrig );
      assert( !pHist->pStmt );
    }
#endif
    pPager->pStmt = 0;

    pPager->state = PAGER_SHARED;
    pagerLeave(pPager);
    return SQLITE_OK;
  }

  assert( pPager->state==PAGER_SYNCED || !pPager->dirtyCache );
  rc = pager_end_transaction(pPager, pPager->setMaster);
  rc = pager_error(pPager, rc);

  pagerLeave(pPager);
  return rc;
}

/*
** Rollback all changes.  The database falls back to PAGER_SHARED mode.
** All in-memory cache pages revert to their original data contents.
................................................................................
** the correct locking protocol or unless some other
** process is writing trash into the journal file (SQLITE_CORRUPT) or
** unless a prior malloc() failed (SQLITE_NOMEM).  Appropriate error
** codes are returned for all these occasions.  Otherwise,
** SQLITE_OK is returned.
*/
int sqlite3PagerRollback(Pager *pPager){
  int rc;
  PAGERTRACE2("ROLLBACK %d\n", PAGERID(pPager));

  if( MEMDB ){
    PgHdr *p;
    for(p=pPager->pAll; p; p=p->pNextAll){
      PgHistory *pHist;
      assert( !p->alwaysRollback );
      if( !p->dirty ){
        assert( !((PgHistory *)PGHDR_TO_HIST(p, pPager))->pOrig );
        assert( !((PgHistory *)PGHDR_TO_HIST(p, pPager))->pStmt );
        continue;
      }

      pHist = PGHDR_TO_HIST(p, pPager);
      if( pHist->pOrig ){
        memcpy(PGHDR_TO_DATA(p), pHist->pOrig, pPager->pageSize);
        PAGERTRACE3("ROLLBACK-PAGE %d of %d\n", p->pgno, PAGERID(pPager));
      }else{
        PAGERTRACE3("PAGE %d is clean on %d\n", p->pgno, PAGERID(pPager));
      }
      clearHistory(pHist);
      p->dirty = 0;
      p->inJournal = 0;
      pHist->inStmt = 0;
      pHist->pPrevStmt = pHist->pNextStmt = 0;
      if( pPager->xReiniter ){
        pPager->xReiniter(p, pPager->pageSize);
      }
    }
    pPager->pDirty = 0;
    pPager->pStmt = 0;
    pPager->dbSize = pPager->origDbSize;
    pager_truncate_cache(pPager);
    pPager->stmtInUse = 0;
    pPager->state = PAGER_SHARED;
    return SQLITE_OK;
  }

  pagerEnter(pPager);
  if( !pPager->dirtyCache || !pPager->journalOpen ){
    rc = pager_end_transaction(pPager, pPager->setMaster);
    pagerLeave(pPager);
    return rc;
  }

  if( pPager->errCode && pPager->errCode!=SQLITE_FULL ){
    if( pPager->state>=PAGER_EXCLUSIVE ){
      pager_playback(pPager, 0);
    }
    pagerLeave(pPager);
    return pPager->errCode;
  }

  if( pPager->state==PAGER_RESERVED ){
    int rc2;
    rc = pager_playback(pPager, 0);
    rc2 = pager_end_transaction(pPager, pPager->setMaster);
    if( rc==SQLITE_OK ){
      rc = rc2;
    }
  }else{
    rc = pager_playback(pPager, 0);
  }
  /* pager_reset(pPager); */

  pPager->dbSize = -1;

  /* If an error occurs during a ROLLBACK, we can no longer trust the pager
  ** cache. So call pager_error() on the way out to make any error 
  ** persistent.
  */
  rc = pager_error(pPager, rc);

  pagerLeave(pPager);
  return rc;
}

/*
** Return TRUE if the database file is opened read-only.  Return FALSE
** if the database is (in theory) writable.
................................................................................
  return pPager->readOnly;
}

/*
** Return the number of references to the pager.
*/
int sqlite3PagerRefcount(Pager *pPager){
  return pPager->nRef;
}

#ifdef SQLITE_TEST
/*
** This routine is used for testing and analysis only.
*/
int *sqlite3PagerStats(Pager *pPager){
  static int a[11];
  a[0] = pPager->nRef;
  a[1] = pPager->nPage;
  a[2] = pPager->mxPage;

  a[3] = pPager->dbSize;
  a[4] = pPager->state;
  a[5] = pPager->errCode;
  a[6] = pPager->nHit;
  a[7] = pPager->nMiss;
  a[8] = 0;  /* Used to be pPager->nOvfl */
  a[9] = pPager->nRead;
  a[10] = pPager->nWrite;

  return a;
}
int sqlite3PagerIsMemdb(Pager *pPager){
  return MEMDB;
}
#endif

................................................................................
    return SQLITE_OK;
  }
  if( !pPager->journalOpen ){
    pPager->stmtAutoopen = 1;
    return SQLITE_OK;
  }
  assert( pPager->journalOpen );
  pagerLeave(pPager);
  assert( pPager->pInStmt==0 );
  pPager->pInStmt = sqlite3BitvecCreate(pPager->dbSize);
  pagerEnter(pPager);
  if( pPager->pInStmt==0 ){
    /* sqlite3OsLock(pPager->fd, SHARED_LOCK); */
    return SQLITE_NOMEM;
  }
  pPager->stmtJSize = pPager->journalOff;
  pPager->stmtSize = pPager->dbSize;
  pPager->stmtHdrOff = 0;
................................................................................

/*
** Commit a statement.
*/
int sqlite3PagerStmtCommit(Pager *pPager){
  pagerEnter(pPager);
  if( pPager->stmtInUse ){
    PgHdr *pPg, *pNext;
    PAGERTRACE2("STMT-COMMIT %d\n", PAGERID(pPager));
    if( !MEMDB ){
      /* sqlite3OsTruncate(pPager->stfd, 0); */
      sqlite3BitvecDestroy(pPager->pInStmt);
      pPager->pInStmt = 0;
    }else{
      for(pPg=pPager->pStmt; pPg; pPg=pNext){
        PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager);
        pNext = pHist->pNextStmt;
        assert( pHist->inStmt );
        pHist->inStmt = 0;
        pHist->pPrevStmt = pHist->pNextStmt = 0;
        sqlite3PageFree(pHist->pStmt);
        pHist->pStmt = 0;
      }
    }
    pPager->stmtNRec = 0;
    pPager->stmtInUse = 0;
    pPager->pStmt = 0;
  }
  pPager->stmtAutoopen = 0;
  pagerLeave(pPager);
  return SQLITE_OK;
}

/*
................................................................................
*/
int sqlite3PagerStmtRollback(Pager *pPager){
  int rc;
  pagerEnter(pPager);
  if( pPager->stmtInUse ){
    PAGERTRACE2("STMT-ROLLBACK %d\n", PAGERID(pPager));
    if( MEMDB ){
      PgHdr *pPg;
      PgHistory *pHist;
      for(pPg=pPager->pStmt; pPg; pPg=pHist->pNextStmt){
        pHist = PGHDR_TO_HIST(pPg, pPager);
        if( pHist->pStmt ){
          memcpy(PGHDR_TO_DATA(pPg), pHist->pStmt, pPager->pageSize);
          sqlite3PageFree(pHist->pStmt);
          pHist->pStmt = 0;
        }
      }
      pPager->dbSize = pPager->stmtSize;
      pager_truncate_cache(pPager);
      rc = SQLITE_OK;
    }else{
      rc = pager_stmt_playback(pPager);
    }
    sqlite3PagerStmtCommit(pPager);
................................................................................
** If the fourth argument, isCommit, is non-zero, then this page is being
** moved as part of a database reorganization just before the transaction 
** is being committed. In this case, it is guaranteed that the database page 
** pPg refers to will not be written to again within this transaction.
*/
int sqlite3PagerMovepage(Pager *pPager, DbPage *pPg, Pgno pgno, int isCommit){
  PgHdr *pPgOld;  /* The page being overwritten. */
  int h;
  Pgno needSyncPgno = 0;

  pagerEnter(pPager);
  assert( pPg->nRef>0 );

  PAGERTRACE5("MOVE %d page %d (needSync=%d) moves to %d\n", 
      PAGERID(pPager), pPg->pgno, pPg->needSync, pgno);
  IOTRACE(("MOVE %p %d %d\n", pPager, pPg->pgno, pgno))



  pager_get_content(pPg);

  /* If the journal needs to be sync()ed before page pPg->pgno can
  ** be written to, store pPg->pgno in local variable needSyncPgno.
  **
  ** If the isCommit flag is set, there is no need to remember that
  ** the journal needs to be sync()ed before database page pPg->pgno 
  ** can be written to. The caller has already promised not to write to it.
  */
  if( pPg->needSync && !isCommit ){
    needSyncPgno = pPg->pgno;
    assert( pPg->inJournal || (int)pgno>pPager->origDbSize );
    assert( pPg->dirty );
    assert( pPager->needSync );
  }

  /* Unlink pPg from its hash-chain */
  unlinkHashChain(pPager, pPg);

  /* If the cache contains a page with page-number pgno, remove it
  ** from its hash chain. Also, if the PgHdr.needSync was set for 
  ** page pgno before the 'move' operation, it needs to be retained 
  ** for the page moved there.
  */
  pPg->needSync = 0;
  pPgOld = pager_lookup(pPager, pgno);

  if( pPgOld ){
    assert( pPgOld->nRef==0 );
    unlinkHashChain(pPager, pPgOld);
    makeClean(pPgOld);
    pPg->needSync = pPgOld->needSync;
  }else{
    pPg->needSync = 0;
  }
  pPg->inJournal = sqlite3BitvecTest(pPager->pInJournal, pgno);





  /* Change the page number for pPg and insert it into the new hash-chain. */
  assert( pgno!=0 );
  pPg->pgno = pgno;
  h = pgno & (pPager->nHash-1);
  if( pPager->aHash[h] ){
    assert( pPager->aHash[h]->pPrevHash==0 );
    pPager->aHash[h]->pPrevHash = pPg;
  }
  pPg->pNextHash = pPager->aHash[h];
  pPager->aHash[h] = pPg;
  pPg->pPrevHash = 0;

  makeDirty(pPg);
  pPager->dirtyCache = 1;
  pPager->dbModified = 1;

  if( needSyncPgno ){
    /* If needSyncPgno is non-zero, then the journal file needs to be 
................................................................................
      if( pPager->pInJournal && (int)needSyncPgno<=pPager->origDbSize ){
        sqlite3BitvecClear(pPager->pInJournal, needSyncPgno);
      }
      pagerLeave(pPager);
      return rc;
    }
    pPager->needSync = 1;
    pPgHdr->needSync = 1;
    pPgHdr->inJournal = 1;
    makeDirty(pPgHdr);
    sqlite3PagerUnref(pPgHdr);
  }

  pagerLeave(pPager);
  return SQLITE_OK;
}
#endif

/*
** Return a pointer to the data for the specified page.
*/
void *sqlite3PagerGetData(DbPage *pPg){
  return PGHDR_TO_DATA(pPg);

}

/*
** Return a pointer to the Pager.nExtra bytes of "extra" space 
** allocated along with the specified page.
*/
void *sqlite3PagerGetExtra(DbPage *pPg){
  Pager *pPager = pPg->pPager;
  return (pPager?PGHDR_TO_EXTRA(pPg, pPager):0);
}

/*
** Get/set the locking-mode for this pager. Parameter eMode must be one
** of PAGER_LOCKINGMODE_QUERY, PAGER_LOCKINGMODE_NORMAL or 
** PAGER_LOCKINGMODE_EXCLUSIVE. If the parameter is not _QUERY, then
** the locking-mode is set to the value specified.
................................................................................
*/
i64 sqlite3PagerJournalSizeLimit(Pager *pPager, i64 iLimit){
  if( iLimit>=-1 ){
    pPager->journalSizeLimit = iLimit;
  }
  return pPager->journalSizeLimit;
}





#endif /* SQLITE_OMIT_DISKIO */

** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.470 2008/08/20 14:49:24 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"



/*
** Macros for troubleshooting.  Normally turned off
*/
#if 0
#define sqlite3DebugPrintf printf
#define PAGERTRACE1(X)       sqlite3DebugPrintf(X)
................................................................................

/*
** This macro rounds values up so that if the value is an address it
** is guaranteed to be an address that is aligned to an 8-byte boundary.
*/
#define FORCE_ALIGNMENT(X)   (((X)+7)&~7)



/*





































































































































































** A macro used for invoking the codec if there is one
*/
#ifdef SQLITE_HAS_CODEC
# define CODEC1(P,D,N,X) if( P->xCodec!=0 ){ P->xCodec(P->pCodecArg,D,N,X); }
# define CODEC2(P,D,N,X) ((char*)(P->xCodec!=0?P->xCodec(P->pCodecArg,D,N,X):D))
#else
# define CODEC1(P,D,N,X) /* NO-OP */
# define CODEC2(P,D,N,X) ((char*)D)
#endif










/*
** A open page cache is an instance of the following structure.
**
** Pager.errCode may be set to SQLITE_IOERR, SQLITE_CORRUPT, or
** or SQLITE_FULL. Once one of the first three errors occurs, it persists
** and is returned as the result of every major pager API call.  The
** SQLITE_FULL return code is slightly different. It persists only until the
................................................................................
  int stmtSize;               /* Size of database (in pages) at stmt_begin() */
  int nRec;                   /* Number of pages written to the journal */
  u32 cksumInit;              /* Quasi-random value added to every checksum */
  int stmtNRec;               /* Number of records in stmt subjournal */
  int nExtra;                 /* Add this many bytes to each in-memory page */
  int pageSize;               /* Number of bytes in a page */
  int nPage;                  /* Total number of in-memory pages */

  int mxPage;                 /* Maximum number of pages to hold in cache */
  Pgno mxPgno;                /* Maximum allowed size of the database */
  Bitvec *pInJournal;         /* One bit for each page in the database file */
  Bitvec *pInStmt;            /* One bit for each page in the database */
  char *zFilename;            /* Name of the database file */
  char *zJournal;             /* Name of the journal file */
  char *zDirectory;           /* Directory hold database and journal files */
  sqlite3_file *fd, *jfd;     /* File descriptors for database and journal */
  sqlite3_file *stfd;         /* File descriptor for the statement subjournal*/
  BusyHandler *pBusyHandler;  /* Pointer to sqlite.busyHandler */




  i64 journalOff;             /* Current byte offset in the journal file */
  i64 journalHdr;             /* Byte offset to previous journal header */
  i64 stmtHdrOff;             /* First journal header written this statement */
  i64 stmtCksum;              /* cksumInit when statement was started */
  i64 stmtJSize;              /* Size of journal at stmt_begin() */
  int sectorSize;             /* Assumed sector size during rollback */
#ifdef SQLITE_TEST
................................................................................
#endif
  void (*xDestructor)(DbPage*,int); /* Call this routine when freeing pages */
  void (*xReiniter)(DbPage*,int);   /* Call this routine when reloading pages */
#ifdef SQLITE_HAS_CODEC
  void *(*xCodec)(void*,void*,Pgno,int); /* Routine for en/decoding data */
  void *pCodecArg;            /* First argument to xCodec() */
#endif








  char *pTmpSpace;            /* Pager.pageSize bytes of space for tmp use */
  char dbFileVers[16];        /* Changes whenever database file changes */
  i64 journalSizeLimit;       /* Size limit for persistent journal files */
  PCache *pPCache;            /* Pointer to page cache object */
};

/*
** The following global variables hold counters used for
** testing purposes only.  These variables do not exist in
** a non-testing build.  These variables are not thread-safe.
*/
#ifdef SQLITE_TEST
int sqlite3_pager_readdb_count = 0;    /* Number of full pages read from DB */
int sqlite3_pager_writedb_count = 0;   /* Number of full pages written to DB */
int sqlite3_pager_writej_count = 0;    /* Number of pages written to journal */

# define PAGER_INCR(v)  v++
#else
# define PAGER_INCR(v)
#endif













/*
** Journal files begin with the following magic string.  The data
** was obtained from /dev/random.  It is used only as a sanity check.
**
** Since version 2.8.0, the journal format contains additional sanity
................................................................................

/*
** The maximum legal page number is (2^31 - 1).
*/
#define PAGER_MAX_PGNO 2147483647

/*
** The following two macros act as a type of recursive mutex. Their
** only purpose is to provide mutual exclusion between the "normal"
** users of a pager object (the btree.c module) and the user of the
** pagerStress() function (the pcache.c module). While the mutex 
** obtained using pagerEnter() is held, the pcache module guarantees 
** that the pagerStress() callback will not be invoked from a thread
** other than the holder of the mutex.

*/




















#define pagerEnter(p) (sqlite3PcacheLock(p->pPCache))
#define pagerLeave(p) (sqlite3PcacheUnlock(p->pPCache))


/*




























































































































** Return true if page *pPg has already been written to the statement
** journal (or statement snapshot has been created, if *pPg is part
** of an in-memory database).
*/
static int pageInStatement(PgHdr *pPg){
  Pager *pPager = pPg->pPager;
  if( MEMDB ){

    return pPg->apSave[1]!=0;
  }else{
    return sqlite3BitvecTest(pPager->pInStmt, pPg->pgno);
  }
}










































/*
** Read a 32-bit integer from the given file descriptor.  Store the integer
** that is read in *pRes.  Return SQLITE_OK if everything worked, or an
** error code is something goes wrong.
**
** All values are stored on disk as big-endian.
*/
................................................................................
  );
  if(
    rc2==SQLITE_FULL ||
    rc2==SQLITE_IOERR ||
    rc2==SQLITE_CORRUPT
  ){
    pPager->errCode = rc;
    if( pPager->state==PAGER_UNLOCK 
     && sqlite3PcacheRefCount(pPager->pPCache)==0 
    ){
      /* If the pager is already unlocked, call pager_unlock() now to
      ** clear the error state and ensure that the pager-cache is 
      ** completely empty.
      */
      pager_unlock(pPager);
    }
  }
................................................................................
  int i;
  for(i=0; i<nByte; i++){
    hash = (hash*1039) + pData[i];
  }
  return hash;
}
static u32 pager_pagehash(PgHdr *pPage){
  return pager_datahash(pPage->pPager->pageSize, (unsigned char *)pPage->pData);

}
static u32 pager_set_pagehash(PgHdr *pPage){
  pPage->pageHash = pager_pagehash(pPage);
}

/*
** The CHECK_PAGE macro takes a PgHdr* as an argument. If SQLITE_CHECK_PAGES
** is defined, and NDEBUG is not defined, an assert() statement checks
** that the page is either dirty or still matches the calculated page-hash.
*/
#define CHECK_PAGE(x) checkPage(x)
static void checkPage(PgHdr *pPg){
  Pager *pPager = pPg->pPager;
  assert( !pPg->pageHash || pPager->errCode || MEMDB 
      || (pPg->flags&PGHDR_DIRTY) || pPg->pageHash==pager_pagehash(pPg) );
}

#else
#define pager_datahash(X,Y)  0
#define pager_pagehash(X)  0
#define CHECK_PAGE(x)
#endif
................................................................................
   && jrnlSize>jrnlOff
  ){
    rc = sqlite3OsTruncate(pPager->jfd, jrnlOff);
  }
  return rc;
}

























/*
** Find a page in the hash table given its page number.  Return
** a pointer to the page or NULL if not found.
*/
static PgHdr *pager_lookup(Pager *pPager, Pgno pgno){
  PgHdr *p;
  sqlite3PcacheFetch(pPager->pPCache, pgno, 0, &p);




  return p;
}

/*
** Clear the in-memory cache.  This routine
** sets the state of the pager back to what it was when it was first
** opened.  Any outstanding pages are invalidated and subsequent attempts
** to access those pages will likely result in a coredump.
*/
static void pager_reset(Pager *pPager){

  if( pPager->errCode ) return;



















  sqlite3PcacheClear(pPager->pPCache);
}

/*
** Unlock the database file. 
**
** If the pager is currently in error state, discard the contents of 
** the cache and reset the Pager structure internal state. If there is
................................................................................

/*
** Execute a rollback if a transaction is active and unlock the 
** database file. If the pager has already entered the error state, 
** do not attempt the rollback.
*/
static void pagerUnlockAndRollback(Pager *p){

  if( p->errCode==SQLITE_OK && p->state>=PAGER_RESERVED ){
    sqlite3BeginBenignMalloc();
    sqlite3PagerRollback(p);
    sqlite3EndBenignMalloc();
  }
  pager_unlock(p);




}

/*
** This routine ends a transaction.  A transaction is ended by either
** a COMMIT or a ROLLBACK.
**
** When this routine is called, the pager has the journal file open and
................................................................................
** The journal file is either deleted or truncated.
**
** TODO: Consider keeping the journal file open for temporary databases.
** This might give a performance improvement on windows where opening
** a file is an expensive operation.
*/
static int pager_end_transaction(Pager *pPager, int hasMaster){

  int rc = SQLITE_OK;
  int rc2 = SQLITE_OK;
  assert( !MEMDB );
  if( pPager->state<PAGER_RESERVED ){
    return SQLITE_OK;
  }
  sqlite3PagerStmtCommit(pPager);
................................................................................
      pPager->journalOpen = 0;
      if( rc==SQLITE_OK && !pPager->tempFile ){
        rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
      }
    }
    sqlite3BitvecDestroy(pPager->pInJournal);
    pPager->pInJournal = 0;
    sqlite3PcacheCleanAll(pPager->pPCache);




#ifdef SQLITE_CHECK_PAGES

    sqlite3PcacheIterate(pPager->pPCache, pager_set_pagehash);
#endif


    sqlite3PcacheSetFlags(pPager->pPCache, 
       ~(PGHDR_IN_JOURNAL | PGHDR_NEED_SYNC | PGHDR_ALWAYS_ROLLBACK), 0
    );
    pPager->dirtyCache = 0;
    pPager->nRec = 0;
  }else{
    assert( pPager->pInJournal==0 );
  }

  if( !pPager->exclusiveMode ){
................................................................................
    pPager->state = PAGER_SHARED;
  }else if( pPager->state==PAGER_SYNCED ){
    pPager->state = PAGER_EXCLUSIVE;
  }
  pPager->origDbSize = 0;
  pPager->setMaster = 0;
  pPager->needSync = 0;
  /* lruListSetFirstSynced(pPager); */
  pPager->dbSize = -1;
  pPager->dbModified = 0;

  return (rc==SQLITE_OK?rc2:rc);
}

/*
................................................................................
  ** 2008-04-14:  When attempting to vacuum a corrupt database file, it
  ** is possible to fail a statement on a database that does not yet exist.
  ** Do not attempt to write if database file has never been opened.
  */
  pPg = pager_lookup(pPager, pgno);
  PAGERTRACE4("PLAYBACK %d page %d hash(%08x)\n",
               PAGERID(pPager), pgno, pager_datahash(pPager->pageSize, aData));
  if( (pPager->state>=PAGER_EXCLUSIVE)
   && (pPg==0 || 0==(pPg->flags&PGHDR_NEED_SYNC))
   && (pPager->fd->pMethods)
  ){
    i64 offset = (pgno-1)*(i64)pPager->pageSize;
    rc = sqlite3OsWrite(pPager->fd, aData, pPager->pageSize, offset);



  }
  if( pPg ){
    /* No page should ever be explicitly rolled back that is in use, except
    ** for page 1 which is held in use in order to keep the lock on the
    ** database active. However such a page may be rolled back as a result
    ** of an internal error resulting in an automatic call to
    ** sqlite3PagerRollback().
    */
    void *pData;
    /* assert( pPg->nRef==0 || pPg->pgno==1 ); */
    pData = pPg->pData;
    memcpy(pData, aData, pPager->pageSize);
    if( pPager->xReiniter ){
      pPager->xReiniter(pPg, pPager->pageSize);
    }
    makeClean(pPg);
#ifdef SQLITE_CHECK_PAGES
    pPg->pageHash = pager_pagehash(pPg);
#endif
    /* If this was page 1, then restore the value of Pager.dbFileVers.
    ** Do this before any decoding. */
    if( pgno==1 ){
      memcpy(&pPager->dbFileVers, &((u8*)pData)[24],sizeof(pPager->dbFileVers));
    }

    /* Decode the page just read from disk */
    CODEC1(pPager, pData, pPg->pgno, 3);
    sqlite3PcacheRelease(pPg);
  }
  return rc;
}

/*
** Parameter zMaster is the name of a master journal file. A single journal
** file that referred to the master journal file has just been rolled back.
................................................................................
  return rc;
}

/*
** Change the maximum number of in-memory pages that are allowed.
*/
void sqlite3PagerSetCachesize(Pager *pPager, int mxPage){
  sqlite3PcacheSetCachesize(pPager->pPCache, mxPage);




}

/*
** Adjust the robustness of the database to damage due to OS crashes
** or power failures by changing the number of syncs()s when writing
** the rollback journal.  There are three levels:
**
................................................................................
  vfsFlags |=  SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE |
            SQLITE_OPEN_EXCLUSIVE | SQLITE_OPEN_DELETEONCLOSE;
  rc = sqlite3OsOpen(pPager->pVfs, 0, pFile, vfsFlags, 0);
  assert( rc!=SQLITE_OK || pFile->pMethods );
  return rc;
}

static int pagerStress(void *);

/*
** Create a new page cache and put a pointer to the page cache in *ppPager.
** The file to be cached need not exist.  The file is not locked until
** the first call to sqlite3PagerGet() and is only held open until the
** last page is released using sqlite3PagerUnref().
**
** If zFilename is NULL then a randomly-named temporary file is created
................................................................................
** It is never written to disk.  This can be used to implement an
** in-memory database.
*/
int sqlite3PagerOpen(
  sqlite3_vfs *pVfs,       /* The virtual file system to use */
  Pager **ppPager,         /* Return the Pager structure here */
  const char *zFilename,   /* Name of the database file to open */
  void (*xDesc)(DbPage*),  /* Page destructor function */
  int nExtra,              /* Extra bytes append to each in-memory page */
  int flags,               /* flags controlling this file */
  int vfsFlags             /* flags passed through to sqlite3_vfs.xOpen() */
){
  u8 *pPtr;
  Pager *pPager = 0;
  int rc = SQLITE_OK;
................................................................................
  int i;
  int tempFile = 0;
  int memDb = 0;
  int readOnly = 0;
  int useJournal = (flags & PAGER_OMIT_JOURNAL)==0;
  int noReadlock = (flags & PAGER_NO_READLOCK)!=0;
  int journalFileSize = sqlite3JournalSize(pVfs);
  int pcacheSize = sqlite3PcacheSize();
  int szPageDflt = SQLITE_DEFAULT_PAGE_SIZE;
  char *zPathname = 0;
  int nPathname = 0;

  /* The default return is a NULL pointer */
  *ppPager = 0;

................................................................................
    }
    nPathname = strlen(zPathname);
  }

  /* Allocate memory for the pager structure */
  pPager = sqlite3MallocZero(
    sizeof(*pPager) +           /* Pager structure */
    pcacheSize      +           /* PCache object */
    journalFileSize +           /* The journal file structure */ 
    pVfs->szOsFile * 3 +        /* The main db and two journal files */ 
    3*nPathname + 40            /* zFilename, zDirectory, zJournal */
  );
  if( !pPager ){
    sqlite3_free(zPathname);
    return SQLITE_NOMEM;
  }
  pPager->pPCache = (PCache *)&pPager[1];
  pPtr = ((u8 *)&pPager[1]) + pcacheSize;
  pPager->vfsFlags = vfsFlags;
  pPager->fd = (sqlite3_file*)&pPtr[pVfs->szOsFile*0];
  pPager->stfd = (sqlite3_file*)&pPtr[pVfs->szOsFile*1];
  pPager->jfd = (sqlite3_file*)&pPtr[pVfs->szOsFile*2];
  pPager->zFilename = (char*)&pPtr[pVfs->szOsFile*2+journalFileSize];
  pPager->zDirectory = &pPager->zFilename[nPathname+1];
  pPager->zJournal = &pPager->zDirectory[nPathname+1];
................................................................................
  ** any Pager.errMask variables.
  */
  if( !pPager || !pPager->pTmpSpace ){
    sqlite3OsClose(pPager->fd);
    sqlite3_free(pPager);
    return ((rc==SQLITE_OK)?SQLITE_NOMEM:rc);
  }
  nExtra = FORCE_ALIGNMENT(nExtra);
  sqlite3PcacheOpen(szPageDflt, nExtra, !memDb, xDesc, !memDb?pagerStress:0, (void *)pPager, pPager->pPCache);

  PAGERTRACE3("OPEN %d %s\n", FILEHANDLEID(pPager->fd), pPager->zFilename);
  IOTRACE(("OPEN %p %s\n", pPager, pPager->zFilename))

  /* Fill in Pager.zDirectory[] */
  memcpy(pPager->zDirectory, pPager->zFilename, nPathname+1);
  for(i=strlen(pPager->zDirectory); i>0 && pPager->zDirectory[i-1]!='/'; i--){}
................................................................................
  /* pPager->needSync = 0; */
  pPager->noSync = pPager->tempFile || !useJournal;
  pPager->fullSync = (pPager->noSync?0:1);
  pPager->sync_flags = SQLITE_SYNC_NORMAL;
  /* pPager->pFirst = 0; */
  /* pPager->pFirstSynced = 0; */
  /* pPager->pLast = 0; */
  pPager->nExtra = nExtra;
  pPager->journalSizeLimit = SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT;
  assert(pPager->fd->pMethods||memDb||tempFile);
  if( !memDb ){
    setSectorSize(pPager);
  }
  /* pPager->pBusyHandler = 0; */
  /* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */
  *ppPager = pPager;


















  return SQLITE_OK;
}

/*
** Set the busy handler function.
*/
void sqlite3PagerSetBusyhandler(Pager *pPager, BusyHandler *pBusyHandler){
................................................................................
** inappropriate, then an alternative page size is set to that
** value before returning.
*/
int sqlite3PagerSetPagesize(Pager *pPager, u16 *pPageSize){
  int rc = SQLITE_OK;
  u16 pageSize = *pPageSize;
  assert( pageSize==0 || (pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE) );
  pagerEnter(pPager);
  if( pageSize && pageSize!=pPager->pageSize 
   && !pPager->memDb && sqlite3PcacheRefCount(pPager->pPCache)==0 
  ){
    char *pNew = (char *)sqlite3PageMalloc(pageSize);
    if( !pNew ){
      rc = SQLITE_NOMEM;
    }else{

      pager_reset(pPager);
      pPager->pageSize = pageSize;
      setSectorSize(pPager);
      sqlite3PageFree(pPager->pTmpSpace);
      pPager->pTmpSpace = pNew;
      sqlite3PcacheSetPageSize(pPager->pPCache, pageSize);
    }
  }
  *pPageSize = pPager->pageSize;
  pagerLeave(pPager);
  return rc;
}

/*
** Return a pointer to the "temporary page" buffer held internally
** by the pager.  This is a buffer that is big enough to hold the
** entire content of a database page.  This buffer is used internally
................................................................................
** response is to zero the memory at pDest and continue.  A real IO error 
** will presumably recur and be picked up later (Todo: Think about this).
*/
int sqlite3PagerReadFileheader(Pager *pPager, int N, unsigned char *pDest){
  int rc = SQLITE_OK;
  memset(pDest, 0, N);
  assert(MEMDB||pPager->fd->pMethods||pPager->tempFile);
  pagerEnter(pPager);
  if( pPager->fd->pMethods ){
    IOTRACE(("DBHDR %p 0 %d\n", pPager, N))
    rc = sqlite3OsRead(pPager->fd, pDest, N, 0);
    if( rc==SQLITE_IOERR_SHORT_READ ){
      rc = SQLITE_OK;
    }
  }
  pagerLeave(pPager);
  return rc;
}

/*
** Return the total number of pages in the disk file associated with
** pPager. 
**
................................................................................
** PENDING_BYTE is byte 4096 (the first byte of page 5) and the size of the
** file is 4096 bytes, 5 is returned instead of 4.
*/
int sqlite3PagerPagecount(Pager *pPager, int *pnPage){
  i64 n = 0;
  int rc;
  assert( pPager!=0 );
  pagerEnter(pPager);
  if( pPager->errCode ){
    rc = pPager->errCode;
    pagerLeave(pPager);
    return rc;
  }
  if( pPager->dbSize>=0 ){
    n = pPager->dbSize;
  } else {
    assert(pPager->fd->pMethods||pPager->tempFile);
    if( (pPager->fd->pMethods)
     && (rc = sqlite3OsFileSize(pPager->fd, &n))!=SQLITE_OK ){

      pager_error(pPager, rc);

      pagerLeave(pPager);
      return rc;
    }
    if( n>0 && n<pPager->pageSize ){
      n = 1;
    }else{
      n /= pPager->pageSize;
    }
................................................................................
  }
  if( n>pPager->mxPgno ){
    pPager->mxPgno = n;
  }
  if( pnPage ){
    *pnPage = n;
  }
  pagerLeave(pPager);
  return SQLITE_OK;
}



/*













** Forward declaration
*/
static int syncJournal(Pager*);











































/*
** This routine is used to truncate the cache when a database
** is truncated.  Drop from the cache all pages whose pgno is
** larger than pPager->dbSize and is unreferenced.
**
** Referenced pages larger than pPager->dbSize are zeroed.
**
** Actually, at the point this routine is called, it would be
** an error to have a referenced page.  But rather than delete
** that page and guarantee a subsequent segfault, it seems better
** to zero it and hope that we error out sanely.
*/
static void pager_truncate_cache(Pager *pPager){


  sqlite3PcacheTruncate(pPager->pPCache, pPager->dbSize);
























}

/*
** Try to obtain a lock on a file.  Invoke the busy callback if the lock
** is currently not available.  Repeat until the busy callback returns
** false or until the lock succeeds.
**
................................................................................
  return rc;
}

/*
** Truncate the file to the number of pages specified.
*/
int sqlite3PagerTruncate(Pager *pPager, Pgno nPage){
  int rc = SQLITE_OK;
  assert( pPager->state>=PAGER_SHARED || MEMDB );

  pagerEnter(pPager);

  sqlite3PagerPagecount(pPager, 0);
  if( pPager->errCode ){
    rc = pPager->errCode;


  }else if( nPage<(unsigned)pPager->dbSize ){


    if( MEMDB ){
      pPager->dbSize = nPage;
      pager_truncate_cache(pPager);



    }else{
      rc = syncJournal(pPager);

      if( rc==SQLITE_OK ){



        /* Get an exclusive lock on the database before truncating. */

        rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);

      }
      if( rc==SQLITE_OK ){

        rc = pager_truncate(pPager, nPage);
      }
    }

  }

  pagerLeave(pPager);
  return rc;
}

/*
** Shutdown the page cache.  Free all memory and close all files.
**
** If a transaction was in progress when this routine is called, that
................................................................................
**
** This function always succeeds. If a transaction is active an attempt
** is made to roll it back. If an error occurs during the rollback 
** a hot journal may be left in the filesystem but no error is returned
** to the caller.
*/
int sqlite3PagerClose(Pager *pPager){
  pagerEnter(pPager);

















  disable_simulated_io_errors();
  sqlite3BeginBenignMalloc();
  pPager->errCode = 0;
  pPager->exclusiveMode = 0;
  pager_reset(pPager);
  pagerUnlockAndRollback(pPager);
................................................................................
  sqlite3OsClose(pPager->fd);
  /* Temp files are automatically deleted by the OS
  ** if( pPager->tempFile ){
  **   sqlite3OsDelete(pPager->zFilename);
  ** }
  */


  sqlite3PageFree(pPager->pTmpSpace);
  sqlite3PcacheClose(pPager->pPCache);
  sqlite3_free(pPager);
  return SQLITE_OK;
}

#if !defined(NDEBUG) || defined(SQLITE_TEST)
/*
** Return the page number for the given page data.
*/
Pgno sqlite3PagerPagenumber(DbPage *p){
  return p->pgno;
}
#endif






























/*
** Increment the reference count for a page.  The input pointer is
** a reference to the page data.
*/
int sqlite3PagerRef(DbPage *pPg){
  pagerEnter(pPg->pPager);
  sqlite3PcacheRef(pPg);
  pagerLeave(pPg->pPager);
  return SQLITE_OK;
}

/*
** Sync the journal.  In other words, make sure all the pages that have
** been written to the journal have actually reached the surface of the
................................................................................
** file. In this case all that is required is to update the nRec field in
** the journal header.
**
** This routine clears the needSync field of every page current held in
** memory.
*/
static int syncJournal(Pager *pPager){

  int rc = SQLITE_OK;

  /* Sync the journal before modifying the main database
  ** (assuming there is a journal and it needs to be synced.)
  */
  if( pPager->needSync ){
    if( !pPager->tempFile ){
................................................................................
      }
      pPager->journalStarted = 1;
    }
    pPager->needSync = 0;

    /* Erase the needSync flag from every page.
    */
    sqlite3PcacheSetFlags(pPager->pPCache, ~PGHDR_NEED_SYNC, 0);


    /* lruListSetFirstSynced(pPager); */
  }

#ifndef NDEBUG
  /* If the Pager.needSync flag is clear then the PgHdr.needSync
  ** flag must also be clear for all pages.  Verify that this
  ** invariant is true.
  */
  else{



    sqlite3PcacheAssertFlags(pPager->pPCache, 0, PGHDR_NEED_SYNC);
    /* assert( pPager->lru.pFirstSynced==pPager->lru.pFirst ); */
  }
#endif

  return rc;
}

/*










































































** Given a list of pages (connected by the PgHdr.pDirty pointer) write
** every one of those pages out to the database file and mark them all
** as clean.
*/
static int pager_write_pagelist(PgHdr *pList){
  Pager *pPager;

  int rc;

  if( pList==0 ) return SQLITE_OK;
  pPager = pList->pPager;

  /* At this point there may be either a RESERVED or EXCLUSIVE lock on the
  ** database file. If there is already an EXCLUSIVE lock, the following
................................................................................
  ** will require a journal playback.
  */
  rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
  if( rc!=SQLITE_OK ){
    return rc;
  }






  while( pList ){

    /* If the file has not yet been opened, open it now. */
    if( !pPager->fd->pMethods ){
      assert(pPager->tempFile);
      rc = sqlite3PagerOpentemp(pPager, pPager->fd, pPager->vfsFlags);
      if( rc ) return rc;
................................................................................
    /* If there are dirty pages in the page cache with page numbers greater
    ** than Pager.dbSize, this means sqlite3PagerTruncate() was called to
    ** make the file smaller (presumably by auto-vacuum code). Do not write
    ** any such pages to the file.
    */
    if( pList->pgno<=pPager->dbSize ){
      i64 offset = (pList->pgno-1)*(i64)pPager->pageSize;
      char *pData = CODEC2(pPager, pList->pData, pList->pgno, 6);
      PAGERTRACE4("STORE %d page %d hash(%08x)\n",
                   PAGERID(pPager), pList->pgno, pager_pagehash(pList));
      IOTRACE(("PGOUT %p %d\n", pPager, pList->pgno));
      rc = sqlite3OsWrite(pPager->fd, pData, pPager->pageSize, offset);
      PAGER_INCR(sqlite3_pager_writedb_count);
      PAGER_INCR(pPager->nWrite);
      if( pList->pgno==1 ){
................................................................................
      PAGERTRACE3("NOSTORE %d page %d\n", PAGERID(pPager), pList->pgno);
    }
#endif
    if( rc ) return rc;
#ifdef SQLITE_CHECK_PAGES
    pList->pageHash = pager_pagehash(pList);
#endif
    makeClean(pList);
    pList = pList->pDirty;
  }

  /* sqlite3PcacheCleanAll(pPager->pPCache); */
  return SQLITE_OK;
}

/*



** This function is called by the pcache layer when it has reached some
** soft memory limit. The argument is a pointer to a purgeable Pager 
** object. This function attempts to make a single dirty page that has no
** outstanding references (if one exists) clean so that it can be recycled 
** by the pcache layer.
*/

static int pagerStress(void *p){
  Pager *pPager = (Pager *)p;
  PgHdr *pPg = sqlite3PcacheDirtyPage(pPager->pPCache);
  int rc = SQLITE_OK;









  if( pPg && pPager->errCode==SQLITE_OK ){
    assert( pPg->flags&PGHDR_DIRTY );
    if( pPg->flags&PGHDR_NEED_SYNC ){
      rc = syncJournal(pPager);
      if( rc==SQLITE_OK && pPager->fullSync 
       && !(sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND)
      ){
        pPager->nRec = 0;
        rc = writeJournalHdr(pPager);
      }
    }
    if( rc==SQLITE_OK ){
      rc = pager_write_pagelist(pPg);
    }
    if( rc!=SQLITE_OK ){
      pager_error(pPager, rc);
    }
  }
  return rc;
}


/*
** Return 1 if there is a hot journal on the given pager.
** A hot journal is one that needs to be played back.
**
** If the current size of the database file is 0 but a journal file
** exists, that is probably an old journal left over from a prior
................................................................................
      }
    }
  }

  return rc;
}





























































































#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
/*
** This function is called to free superfluous dynamically allocated memory
** held by the pager system. Memory in use by any SQLite pager allocated
** by the current thread may be sqlite3_free()ed.
**
** nReq is the number of bytes of memory required. Once this much has
** been released, the function returns. The return value is the total number 
** of bytes of memory released.
*/
int sqlite3PagerReleaseMemory(int nReq){






















































































































  return 0;
}
#endif /* SQLITE_ENABLE_MEMORY_MANAGEMENT */

/*
** Read the content of page pPg out of the database file.
*/
static int readDbPage(Pager *pPager, PgHdr *pPg, Pgno pgno){
................................................................................
  i64 offset;
  assert( MEMDB==0 );
  assert(pPager->fd->pMethods||pPager->tempFile);
  if( !pPager->fd->pMethods ){
    return SQLITE_IOERR_SHORT_READ;
  }
  offset = (pgno-1)*(i64)pPager->pageSize;
  rc = sqlite3OsRead(pPager->fd, pPg->pData, pPager->pageSize, offset);
  PAGER_INCR(sqlite3_pager_readdb_count);
  PAGER_INCR(pPager->nRead);
  IOTRACE(("PGIN %p %d\n", pPager, pgno));
  if( pgno==1 ){
    memcpy(&pPager->dbFileVers, &((u8*)pPg->pData)[24],
                                              sizeof(pPager->dbFileVers));
  }
  CODEC1(pPager, PGHDR_TO_DATA(pPg), pPg->pgno, 3);
  PAGERTRACE4("FETCH %d page %d hash(%08x)\n",
               PAGERID(pPager), pPg->pgno, pager_pagehash(pPg));
  return rc;
}
................................................................................
  int isErrorReset = 0;

  /* If this database is opened for exclusive access, has no outstanding 
  ** page references and is in an error-state, now is the chance to clear
  ** the error. Discard the contents of the pager-cache and treat any
  ** open journal file as a hot-journal.
  */
  if( !MEMDB && pPager->exclusiveMode 
   && sqlite3PcacheRefCount(pPager->pPCache)==0 && pPager->errCode 
  ){
    if( pPager->journalOpen ){
      isErrorReset = 1;
    }
    pPager->errCode = SQLITE_OK;
    pager_reset(pPager);
  }

................................................................................
    return pPager->errCode;
  }

  if( pPager->state==PAGER_UNLOCK || isErrorReset ){
    sqlite3_vfs *pVfs = pPager->pVfs;
    if( !MEMDB ){
      int isHotJournal;
      assert( sqlite3PcacheRefCount(pPager->pPCache)==0 );
      if( !pPager->noReadlock ){
        rc = pager_wait_on_lock(pPager, SHARED_LOCK);
        if( rc!=SQLITE_OK ){
          assert( pPager->state==PAGER_UNLOCK );
          return pager_error(pPager, rc);
        }
        assert( pPager->state>=SHARED_LOCK );
................................................................................
          goto failed;
        }
        assert(pPager->state==PAGER_SHARED || 
            (pPager->exclusiveMode && pPager->state>PAGER_SHARED)
        );
      }

      if( sqlite3PcachePagecount(pPager->pPCache)>0 ){
        /* The shared-lock has just been acquired on the database file
        ** and there are already pages in the cache (from a previous
        ** read or write transaction).  Check to see if the database
        ** has been modified.  If the database has changed, flush the
        ** cache.
        **
        ** Database changes is detected by looking at 15 bytes beginning
................................................................................
  if( rc!=SQLITE_OK ){
    /* pager_unlock() is a no-op for exclusive mode and in-memory databases. */
    pager_unlock(pPager);
  }
  return rc;
}

/*


































































































** Make sure we have the content for a page.  If the page was
** previously acquired with noContent==1, then the content was
** just initialized to zeros instead of being read from disk.
** But now we need the real data off of disk.  So make sure we
** have it.  Read it in if we do not have it already.
*/
static int pager_get_content(PgHdr *pPg){

  if( pPg->flags&PGHDR_NEED_READ ){
    int rc = readDbPage(pPg->pPager, pPg, pPg->pgno);
    if( rc==SQLITE_OK ){

      pPg->flags &= ~PGHDR_NEED_READ;
    }else{
      return rc;
    }
  }
  return SQLITE_OK;
}

/*
** If the reference count has reached zero, and the pager is not in the
** middle of a write transaction or opened in exclusive mode, unlock it.
*/ 
static void pagerUnlockIfUnused(Pager *pPager){
  if( (sqlite3PcacheRefCount(pPager->pPCache)==0)
    && (!pPager->exclusiveMode || pPager->journalOff>0) 
  ){
    pagerUnlockAndRollback(pPager);
  }
}

/*
** Drop a page from the cache using sqlite3PcacheDrop().
**
** If this means there are now no pages with references to them, a rollback
** occurs and the lock on the database is removed.
*/
static void pagerDropPage(DbPage *pPg){
  Pager *pPager = pPg->pPager;
  sqlite3PcacheDrop(pPg);
  pagerUnlockIfUnused(pPager);
}

/*
** Acquire a page.
**
** A read lock on the disk file is obtained when the first page is acquired. 
** This read lock is dropped when the last page is released.
**
................................................................................
*/
static int pagerAcquire(
  Pager *pPager,      /* The pager open on the database file */
  Pgno pgno,          /* Page number to fetch */
  DbPage **ppPage,    /* Write a pointer to the page here */
  int noContent       /* Do not bother reading content from disk if true */
){
  PgHdr *pPg = 0;
  int rc;

  assert( pPager->state==PAGER_UNLOCK 
       || sqlite3PcacheRefCount(pPager->pPCache)>0 
       || pgno==1 
  );

  /* The maximum page number is 2^31. Return SQLITE_CORRUPT if a page
  ** number greater than this, or zero, is requested.
  */
  if( pgno>PAGER_MAX_PGNO || pgno==0 || pgno==PAGER_MJ_PGNO(pPager) ){
    return SQLITE_CORRUPT_BKPT;
  }
................................................................................
  */
  rc = pagerSharedLock(pPager);
  if( rc!=SQLITE_OK ){
    return rc;
  }
  assert( pPager->state!=PAGER_UNLOCK );

  rc = sqlite3PcacheFetch(pPager->pPCache, pgno, 1, &pPg);






  if( rc!=SQLITE_OK ){
    return rc;
  }
  if( pPager->errCode && pPg->nRef==1 ){
    sqlite3PcacheDrop(pPg);
    return pPager->errCode;
  }

  if( pPg->pPager==0 ){
    /* The pager cache has created a new page. Its content needs to 
    ** be initialized.
    */
    int nMax;
    PAGER_INCR(pPager->nMiss);
    /* pPager->nRef++; */
    pPg->pPager = pPager;
    if( sqlite3BitvecTest(pPager->pInJournal, pgno) ){



      pPg->flags |= PGHDR_IN_JOURNAL;
    }

    memset(pPg->pExtra, 0, pPager->nExtra);


    rc = sqlite3PagerPagecount(pPager, &nMax);
    if( rc!=SQLITE_OK ){
      sqlite3PagerUnref(pPg);
      return rc;
    }




    if( nMax<(int)pgno || MEMDB || (noContent && !pPager->alwaysRollback) ){
      if( pgno>pPager->mxPgno ){
        sqlite3PagerUnref(pPg);
        return SQLITE_FULL;
      }
      memset(pPg->pData, 0, pPager->pageSize);
      if( noContent && !pPager->alwaysRollback ){
        pPg->flags |= PGHDR_NEED_READ;
      }
      IOTRACE(("ZERO %p %d\n", pPager, pgno));
    }else{
      rc = readDbPage(pPager, pPg, pgno);
      if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){

        /* sqlite3PagerUnref(pPg); */
        pagerDropPage(pPg);
        return rc;
      }

    }











#ifdef SQLITE_CHECK_PAGES
    pPg->pageHash = pager_pagehash(pPg);
#endif
  }else{
    /* The requested page is in the page cache. */
    assert(sqlite3PcacheRefCount(pPager->pPCache)>0 || pgno==1);
    PAGER_INCR(pPager->nHit);
    if( !noContent ){
      rc = pager_get_content(pPg);
      if( rc ){
        sqlite3PagerUnref(pPg);
        return rc;
      }
    }

  }

  *ppPage = pPg;
  return SQLITE_OK;
}

int sqlite3PagerAcquire(
  Pager *pPager,      /* The pager open on the database file */
  Pgno pgno,          /* Page number to fetch */
  DbPage **ppPage,    /* Write a pointer to the page here */
  int noContent       /* Do not bother reading content from disk if true */
){
  int rc;
................................................................................
** and sqlite3PagerGet() is that _get() will go to the disk and read
** in the page if the page is not already in cache.  This routine
** returns NULL if the page is not in cache or if a disk I/O error 
** has ever happened.
*/
DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){
  PgHdr *pPg = 0;

  assert( pPager!=0 );
  assert( pgno!=0 );

  pagerEnter(pPager);
  if( (pPager->state!=PAGER_UNLOCK)
   && (pPager->errCode==SQLITE_OK || pPager->errCode==SQLITE_FULL)
  ){
    sqlite3PcacheFetch(pPager->pPCache, pgno, 0, &pPg);


  }
  pagerLeave(pPager);

  return pPg;
}

/*
** Release a page.
**
** If the number of references to the page drop to zero, then the
** page is added to the LRU list.  When all references to all pages
** are released, a rollback occurs and the lock on the database is
** removed.
*/
int sqlite3PagerUnref(DbPage *pPg){
  if( pPg ){


    Pager *pPager = pPg->pPager;




    pagerEnter(pPager);




















    sqlite3PcacheRelease(pPg);
    pagerUnlockIfUnused(pPager);


    pagerLeave(pPager);
  }
  return SQLITE_OK;
}

/*
** Create a journal file for pPager.  There should already be a RESERVED
** or EXCLUSIVE lock on the database file when this routine is called.
**
................................................................................
  Pager *pPager = pPg->pPager;
  int rc = SQLITE_OK;
  pagerEnter(pPager);
  assert( pPg->nRef>0 );
  assert( pPager->state!=PAGER_UNLOCK );
  if( pPager->state==PAGER_SHARED ){
    assert( pPager->pInJournal==0 );
    sqlite3PcacheAssertFlags(pPager->pPCache, 0, PGHDR_IN_JOURNAL);
    if( MEMDB ){
      pPager->state = PAGER_EXCLUSIVE;
      pPager->origDbSize = pPager->dbSize;
    }else{
      rc = sqlite3OsLock(pPager->fd, RESERVED_LOCK);
      if( rc==SQLITE_OK ){
        pPager->state = PAGER_RESERVED;
................................................................................
    ** kept open and either was truncated to 0 bytes or its header was
    ** overwritten with zeros.
    */
    assert( pPager->nRec==0 );
    assert( pPager->origDbSize==0 );
    assert( pPager->pInJournal==0 );
    sqlite3PagerPagecount(pPager, 0);

    pPager->pInJournal = sqlite3BitvecCreate( pPager->dbSize );

    if( !pPager->pInJournal ){
      rc = SQLITE_NOMEM;
    }else{
      pPager->origDbSize = pPager->dbSize;
      rc = writeJournalHdr(pPager);
    }
  }
................................................................................
}

/*
** Make a page dirty.  Set its dirty flag and add it to the dirty
** page list.
*/
static void makeDirty(PgHdr *pPg){
  sqlite3PcacheMakeDirty(pPg);









}

/*
** Make a page clean.  Clear its dirty bit and remove it from the
** dirty page list.
*/
static void makeClean(PgHdr *pPg){
  sqlite3PcacheMakeClean(pPg);













}


/*
** Mark a data page as writeable.  The page is written into the journal 
** if it is not there already.  This routine must be called before making
** changes to a page.
................................................................................
** If the journal file could not be written because the disk is full,
** then this routine returns SQLITE_FULL and does an immediate rollback.
** All subsequent write attempts also return SQLITE_FULL until there
** is a call to sqlite3PagerCommit() or sqlite3PagerRollback() to
** reset.
*/
static int pager_write(PgHdr *pPg){
  void *pData = pPg->pData;
  Pager *pPager = pPg->pPager;
  int rc = SQLITE_OK;

  /* Check for errors
  */
  if( pPager->errCode ){ 
    return pPager->errCode;
................................................................................
    return rc;
  }

  /* Mark the page as dirty.  If the page has already been written
  ** to the journal then we can return right away.
  */
  makeDirty(pPg);
  if( (pPg->flags&PGHDR_IN_JOURNAL)
   && (pageInStatement(pPg) || pPager->stmtInUse==0) 
  ){
    pPager->dirtyCache = 1;
    pPager->dbModified = 1;
  }else{

    /* If we get this far, it means that the page needs to be
    ** written to the transaction journal or the ckeckpoint journal
    ** or both.
................................................................................
    pPager->dirtyCache = 1;
    pPager->dbModified = 1;
  
    /* The transaction journal now exists and we have a RESERVED or an
    ** EXCLUSIVE lock on the main database file.  Write the current page to
    ** the transaction journal if it is not there already.
    */
    if( !(pPg->flags&PGHDR_IN_JOURNAL) && (pPager->journalOpen || MEMDB) ){
      if( (int)pPg->pgno <= pPager->origDbSize ){
        if( MEMDB ){

          PAGERTRACE3("JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno);
          rc = sqlite3PcachePreserve(pPg, 0);
          if( rc!=SQLITE_OK ){


            return rc;
          }

        }else{
          u32 cksum;
          char *pData2;

          /* We should never write to the journal file the page that
          ** contains the database locks.  The following assert verifies
          ** that we do not. */
................................................................................
            rc = write32bits(pPager->jfd, pPager->journalOff, cksum);
            pPager->journalOff += 4;
          }
          IOTRACE(("JOUT %p %d %lld %d\n", pPager, pPg->pgno, 
                   pPager->journalOff, pPager->pageSize));
          PAGER_INCR(sqlite3_pager_writej_count);
          PAGERTRACE5("JOURNAL %d page %d needSync=%d hash(%08x)\n",
               PAGERID(pPager), pPg->pgno, 
               ((pPg->flags&PGHDR_NEED_SYNC)?1:0), pager_pagehash(pPg));

          /* An error has occured writing to the journal file. The 
          ** transaction will be rolled back by the layer above.
          */
          if( rc!=SQLITE_OK ){
            return rc;
          }

          pPager->nRec++;
          assert( pPager->pInJournal!=0 );
          sqlite3BitvecSet(pPager->pInJournal, pPg->pgno);
          if( !pPager->noSync ){
            pPg->flags |= PGHDR_NEED_SYNC;
          }
          if( pPager->stmtInUse ){
            sqlite3BitvecSet(pPager->pInStmt, pPg->pgno);
          }
        }
      }else{
        if( !pPager->journalStarted && !pPager->noSync ){
          pPg->flags |= PGHDR_NEED_SYNC;
        }
        PAGERTRACE4("APPEND %d page %d needSync=%d\n",
                PAGERID(pPager), pPg->pgno,
               ((pPg->flags&PGHDR_NEED_SYNC)?1:0));
      }

      if( pPg->flags&PGHDR_NEED_SYNC ){
        pPager->needSync = 1;
      }

      pPg->flags |= PGHDR_IN_JOURNAL;
    }
  
    /* If the statement journal is open and the page is not in it,
    ** then write the current page to the statement journal.  Note that
    ** the statement journal format differs from the standard journal format
    ** in that it omits the checksums and the header.
    */
    if( pPager->stmtInUse 
     && !pageInStatement(pPg) 
     && (int)pPg->pgno<=pPager->stmtSize 
    ){
      assert( 
        (pPg->flags&PGHDR_IN_JOURNAL) || (int)pPg->pgno>pPager->origDbSize );
      if( MEMDB ){

        rc = sqlite3PcachePreserve(pPg, 1);
        if( rc!=SQLITE_OK ){
          return rc;

        }
        PAGERTRACE3("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno);
        /* page_add_to_stmt_list(pPg); */
      }else{
        i64 offset = pPager->stmtNRec*(4+pPager->pageSize);
        char *pData2 = CODEC2(pPager, pData, pPg->pgno, 7);
        rc = write32bits(pPager->stfd, offset, pPg->pgno);
        if( rc==SQLITE_OK ){
          rc = sqlite3OsWrite(pPager->stfd, pData2, pPager->pageSize, offset+4);
        }
................................................................................
      Pgno pg = pg1+ii;
      PgHdr *pPage;
      if( pg==pPg->pgno || !sqlite3BitvecTest(pPager->pInJournal, pg) ){
        if( pg!=PAGER_MJ_PGNO(pPager) ){
          rc = sqlite3PagerGet(pPager, pg, &pPage);
          if( rc==SQLITE_OK ){
            rc = pager_write(pPage);
            if( pPage->flags&PGHDR_NEED_SYNC ){
              needSync = 1;
            }
            sqlite3PagerUnref(pPage);
          }
        }
      }else if( (pPage = pager_lookup(pPager, pg))!=0 ){
        if( pPage->flags&PGHDR_NEED_SYNC ){
          needSync = 1;
        }
        sqlite3PagerUnref(pPage);
      }
    }

    /* If the PgHdr.needSync flag is set for any of the nPage pages 
    ** starting at pg1, then it needs to be set for all of them. Because
    ** writing to any of these nPage pages may damage the others, the
    ** journal file must contain sync()ed copies of all of them
    ** before any of them can be written out to the database file.
    */
    if( needSync ){
      for(ii=0; ii<nPage && needSync; ii++){
        PgHdr *pPage = pager_lookup(pPager, pg1+ii);
        if( pPage ) pPage->flags |= PGHDR_NEED_SYNC;
        sqlite3PagerUnref(pPage);
      }
      assert(pPager->needSync);
    }

    assert( pPager->doNotSync==1 );
    pPager->doNotSync = 0;
  }else{
................................................................................
/*
** Return TRUE if the page given in the argument was previously passed
** to sqlite3PagerWrite().  In other words, return TRUE if it is ok
** to change the content of the page.
*/
#ifndef NDEBUG
int sqlite3PagerIswriteable(DbPage *pPg){
  return pPg->flags&PGHDR_DIRTY;
}
#endif

/*
** A call to this routine tells the pager that it is not necessary to
** write the information on page pPg back to the disk, even though
** that page might be marked as dirty.
................................................................................
*/
void sqlite3PagerDontWrite(DbPage *pDbPage){
  PgHdr *pPg = pDbPage;
  Pager *pPager = pPg->pPager;

  if( MEMDB ) return;
  pagerEnter(pPager);
  pPg->flags |= PGHDR_ALWAYS_ROLLBACK;
  if( (pPg->flags&PGHDR_DIRTY) && !pPager->stmtInUse ){
    assert( pPager->state>=PAGER_SHARED );
    if( pPager->dbSize==(int)pPg->pgno && pPager->origDbSize<pPager->dbSize ){
      /* If this pages is the last page in the file and the file has grown
      ** during the current transaction, then do NOT mark the page as clean.
      ** When the database file grows, we must make sure that the last page
      ** gets written at least once so that the disk file will be the correct
      ** size. If you do not write this page and the size of the file
................................................................................
  pagerEnter(pPager);
  assert( pPager->state>=PAGER_RESERVED );

  /* If the journal file is not open, or DontWrite() has been called on
  ** this page (DontWrite() sets the alwaysRollback flag), then this
  ** function is a no-op.
  */
  if( pPager->journalOpen==0 || (pPg->flags&PGHDR_ALWAYS_ROLLBACK) 
   || pPager->alwaysRollback 
  ){
    pagerLeave(pPager);
    return;
  }
  assert( !MEMDB );    /* For a memdb, pPager->journalOpen is always 0 */

#ifdef SQLITE_SECURE_DELETE
  if( pPg->inJournal || (int)pPg->pgno > pPager->origDbSize ){
    pagerLeave(pPager);
    return;
  }
#endif

  /* If SECURE_DELETE is disabled, then there is no way that this
  ** routine can be called on a page for which sqlite3PagerDontWrite()
  ** has not been previously called during the same transaction.
................................................................................
  ** pages on the freelist (ex: corrupt9.test) then the following is not
  ** necessarily true:
  */
  /* assert( !pPg->inJournal && (int)pPg->pgno <= pPager->origDbSize ); */

  assert( pPager->pInJournal!=0 );
  sqlite3BitvecSet(pPager->pInJournal, pPg->pgno);
  pPg->flags |= PGHDR_IN_JOURNAL;
  pPg->flags &= ~PGHDR_NEED_READ;
  if( pPager->stmtInUse ){
    assert( pPager->stmtSize >= pPager->origDbSize );
    sqlite3BitvecSet(pPager->pInStmt, pPg->pgno);
  }
  PAGERTRACE3("DONT_ROLLBACK page %d of %d\n", pPg->pgno, PAGERID(pPager));
  IOTRACE(("GARBAGE %p %d\n", pPager, pPg->pgno))
  pagerLeave(pPager);
................................................................................
        return rc;
      }
    }

    /* Increment the value just read and write it back to byte 24. */
    change_counter = sqlite3Get4byte((u8*)pPager->dbFileVers);
    change_counter++;
    put32bits(((char*)pPgHdr->pData)+24, change_counter);

#ifdef SQLITE_ENABLE_ATOMIC_WRITE
    if( isDirect && pPager->fd->pMethods ){
      const void *zBuf = pPgHdr->pData;
      rc = sqlite3OsWrite(pPager->fd, zBuf, pPager->pageSize, 0);
    }
#endif

    /* Release the page reference. */
    sqlite3PagerUnref(pPgHdr);
    pPager->changeCountDone = 1;
................................................................................
    **      blocks of size page-size, and
    **    + This commit is not part of a multi-file transaction, and
    **    + Exactly one page has been modified and store in the journal file.
    **
    ** If the optimization can be used, then the journal file will never
    ** be created for this transaction.
    */
    pPg = sqlite3PcacheDirtyList(pPager->pPCache);
    int useAtomicWrite = (
        !zMaster && 
        pPager->journalOpen &&
        pPager->journalOff==jrnlBufferSize(pPager) && 
        nTrunc==0 && 
        (pPg==0 || pPg->pDirty==0)
    );
    assert( pPager->journalOpen || pPager->journalMode==PAGER_JOURNALMODE_OFF );
    if( useAtomicWrite ){
      /* Update the nRec field in the journal file. */
      int offset = pPager->journalHdr + sizeof(aJournalMagic);
      assert(pPager->nRec==1);
      rc = write32bits(pPager->jfd, offset, pPager->nRec);
................................................................................
    if( nTrunc!=0 ){
      rc = sqlite3PagerTruncate(pPager, nTrunc);
      if( rc!=SQLITE_OK ) goto sync_exit;
    }
#endif

    /* Write all dirty pages to the database file */
    pPg = sqlite3PcacheDirtyList(pPager->pPCache);
    rc = pager_write_pagelist(pPg);
    if( rc!=SQLITE_OK ){
      assert( rc!=SQLITE_IOERR_BLOCKED );
      /* The error might have left the dirty list all fouled up here,
      ** but that does not matter because if the if the dirty list did
      ** get corrupted, then the transaction will roll back and
      ** discard the dirty list.  There is an assert in
      ** pager_get_all_dirty_pages() that verifies that no attempt
      ** is made to use an invalid dirty list.
      */
      goto sync_exit;
    }
    sqlite3PcacheCleanAll(pPager->pPCache);

    /* Sync the database file. */
    if( !pPager->noSync && !noSync ){
      rc = sqlite3OsSync(pPager->fd, pPager->sync_flags);
    }
    IOTRACE(("DBSYNC %p\n", pPager))

................................................................................
** Commit all changes to the database and release the write lock.
**
** If the commit fails for any reason, a rollback attempt is made
** and an error code is returned.  If the commit worked, SQLITE_OK
** is returned.
*/
int sqlite3PagerCommitPhaseTwo(Pager *pPager){
  int rc = SQLITE_OK;


  if( pPager->errCode ){
    return pPager->errCode;
  }
  if( pPager->state<PAGER_RESERVED ){
    return SQLITE_ERROR;
  }
................................................................................
          pPager->exclusiveMode!=0) ){
    assert( pPager->dirtyCache==0 || pPager->journalOpen==0 );
    return SQLITE_OK;
  }
  pagerEnter(pPager);
  PAGERTRACE2("COMMIT %d\n", PAGERID(pPager));
  if( MEMDB ){
    sqlite3PcacheCommit(pPager->pPCache, 0);
    sqlite3PcacheCleanAll(pPager->pPCache);
    sqlite3PcacheSetFlags(pPager->pPCache, 
       ~(PGHDR_IN_JOURNAL | PGHDR_NEED_SYNC | PGHDR_ALWAYS_ROLLBACK), 0

















    );
    pPager->state = PAGER_SHARED;



  }else{
    assert( pPager->state==PAGER_SYNCED || !pPager->dirtyCache );
    rc = pager_end_transaction(pPager, pPager->setMaster);
    rc = pager_error(pPager, rc);
  }
  pagerLeave(pPager);
  return rc;
}

/*
** Rollback all changes.  The database falls back to PAGER_SHARED mode.
** All in-memory cache pages revert to their original data contents.
................................................................................
** the correct locking protocol or unless some other
** process is writing trash into the journal file (SQLITE_CORRUPT) or
** unless a prior malloc() failed (SQLITE_NOMEM).  Appropriate error
** codes are returned for all these occasions.  Otherwise,
** SQLITE_OK is returned.
*/
int sqlite3PagerRollback(Pager *pPager){
  int rc = SQLITE_OK;
  PAGERTRACE2("ROLLBACK %d\n", PAGERID(pPager));
  pagerEnter(pPager);
  if( MEMDB ){

    sqlite3PcacheRollback(pPager->pPCache, 1);
    sqlite3PcacheRollback(pPager->pPCache, 0);
    sqlite3PcacheCleanAll(pPager->pPCache);
    sqlite3PcacheSetFlags(pPager->pPCache, 
       ~(PGHDR_IN_JOURNAL | PGHDR_NEED_SYNC | PGHDR_ALWAYS_ROLLBACK), 0
    );





















    pPager->dbSize = pPager->origDbSize;
    pager_truncate_cache(pPager);
    pPager->stmtInUse = 0;
    pPager->state = PAGER_SHARED;




  }else if( !pPager->dirtyCache || !pPager->journalOpen ){
    rc = pager_end_transaction(pPager, pPager->setMaster);




  }else if( pPager->errCode && pPager->errCode!=SQLITE_FULL ){
    if( pPager->state>=PAGER_EXCLUSIVE ){
      pager_playback(pPager, 0);
    }

    rc = pPager->errCode;

  }else{
    if( pPager->state==PAGER_RESERVED ){
      int rc2;
      rc = pager_playback(pPager, 0);
      rc2 = pager_end_transaction(pPager, pPager->setMaster);
      if( rc==SQLITE_OK ){
        rc = rc2;
      }
    }else{
      rc = pager_playback(pPager, 0);
    }


    pPager->dbSize = -1;

    /* If an error occurs during a ROLLBACK, we can no longer trust the pager
    ** cache. So call pager_error() on the way out to make any error 
    ** persistent.
    */
    rc = pager_error(pPager, rc);
  }
  pagerLeave(pPager);
  return rc;
}

/*
** Return TRUE if the database file is opened read-only.  Return FALSE
** if the database is (in theory) writable.
................................................................................
  return pPager->readOnly;
}

/*
** Return the number of references to the pager.
*/
int sqlite3PagerRefcount(Pager *pPager){
  return sqlite3PcacheRefCount(pPager->pPCache);
}

#ifdef SQLITE_TEST
/*
** This routine is used for testing and analysis only.
*/
int *sqlite3PagerStats(Pager *pPager){
  static int a[11];
  pagerEnter(pPager);
  a[0] = sqlite3PcacheRefCount(pPager->pPCache);
  a[1] = sqlite3PcachePagecount(pPager->pPCache);
  a[2] = sqlite3PcacheGetCachesize(pPager->pPCache);
  a[3] = pPager->dbSize;
  a[4] = pPager->state;
  a[5] = pPager->errCode;
  a[6] = pPager->nHit;
  a[7] = pPager->nMiss;
  a[8] = 0;  /* Used to be pPager->nOvfl */
  a[9] = pPager->nRead;
  a[10] = pPager->nWrite;
  pagerLeave(pPager);
  return a;
}
int sqlite3PagerIsMemdb(Pager *pPager){
  return MEMDB;
}
#endif

................................................................................
    return SQLITE_OK;
  }
  if( !pPager->journalOpen ){
    pPager->stmtAutoopen = 1;
    return SQLITE_OK;
  }
  assert( pPager->journalOpen );

  assert( pPager->pInStmt==0 );
  pPager->pInStmt = sqlite3BitvecCreate(pPager->dbSize);

  if( pPager->pInStmt==0 ){
    /* sqlite3OsLock(pPager->fd, SHARED_LOCK); */
    return SQLITE_NOMEM;
  }
  pPager->stmtJSize = pPager->journalOff;
  pPager->stmtSize = pPager->dbSize;
  pPager->stmtHdrOff = 0;
................................................................................

/*
** Commit a statement.
*/
int sqlite3PagerStmtCommit(Pager *pPager){
  pagerEnter(pPager);
  if( pPager->stmtInUse ){

    PAGERTRACE2("STMT-COMMIT %d\n", PAGERID(pPager));
    if( !MEMDB ){
      /* sqlite3OsTruncate(pPager->stfd, 0); */
      sqlite3BitvecDestroy(pPager->pInStmt);
      pPager->pInStmt = 0;
    }else{
      sqlite3PcacheCommit(pPager->pPCache, 1);








    }
    pPager->stmtNRec = 0;
    pPager->stmtInUse = 0;

  }
  pPager->stmtAutoopen = 0;
  pagerLeave(pPager);
  return SQLITE_OK;
}

/*
................................................................................
*/
int sqlite3PagerStmtRollback(Pager *pPager){
  int rc;
  pagerEnter(pPager);
  if( pPager->stmtInUse ){
    PAGERTRACE2("STMT-ROLLBACK %d\n", PAGERID(pPager));
    if( MEMDB ){
      sqlite3PcacheRollback(pPager->pPCache, 1);









      pPager->dbSize = pPager->stmtSize;
      pager_truncate_cache(pPager);
      rc = SQLITE_OK;
    }else{
      rc = pager_stmt_playback(pPager);
    }
    sqlite3PagerStmtCommit(pPager);
................................................................................
** If the fourth argument, isCommit, is non-zero, then this page is being
** moved as part of a database reorganization just before the transaction 
** is being committed. In this case, it is guaranteed that the database page 
** pPg refers to will not be written to again within this transaction.
*/
int sqlite3PagerMovepage(Pager *pPager, DbPage *pPg, Pgno pgno, int isCommit){
  PgHdr *pPgOld;  /* The page being overwritten. */

  Pgno needSyncPgno = 0;


  assert( pPg->nRef>0 );

  PAGERTRACE5("MOVE %d page %d (needSync=%d) moves to %d\n", 
      PAGERID(pPager), pPg->pgno, (pPg->flags&PGHDR_NEED_SYNC)?1:0, pgno);
  IOTRACE(("MOVE %p %d %d\n", pPager, pPg->pgno, pgno))

  pagerEnter(pPager);

  pager_get_content(pPg);

  /* If the journal needs to be sync()ed before page pPg->pgno can
  ** be written to, store pPg->pgno in local variable needSyncPgno.
  **
  ** If the isCommit flag is set, there is no need to remember that
  ** the journal needs to be sync()ed before database page pPg->pgno 
  ** can be written to. The caller has already promised not to write to it.
  */
  if( (pPg->flags&PGHDR_NEED_SYNC) && !isCommit ){
    needSyncPgno = pPg->pgno;
    assert( (pPg->flags&PGHDR_IN_JOURNAL) || (int)pgno>pPager->origDbSize );
    assert( pPg->flags&PGHDR_DIRTY );
    assert( pPager->needSync );
  }




  /* If the cache contains a page with page-number pgno, remove it
  ** from its hash chain. Also, if the PgHdr.needSync was set for 
  ** page pgno before the 'move' operation, it needs to be retained 
  ** for the page moved there.
  */
  pPg->flags &= ~(PGHDR_NEED_SYNC|PGHDR_IN_JOURNAL);
  pPgOld = pager_lookup(pPager, pgno);
  assert( !pPgOld || pPgOld->nRef==1 );
  if( pPgOld ){

    pPg->flags |= (pPgOld->flags&PGHDR_NEED_SYNC);




  }
  if( sqlite3BitvecTest(pPager->pInJournal, pgno) ){
    pPg->flags |= PGHDR_IN_JOURNAL;
  }

  sqlite3PcacheMove(pPg, pgno);
  if( pPgOld ){
    sqlite3PcacheMove(pPgOld, 0);
    sqlite3PcacheRelease(pPgOld);





  }




  makeDirty(pPg);
  pPager->dirtyCache = 1;
  pPager->dbModified = 1;

  if( needSyncPgno ){
    /* If needSyncPgno is non-zero, then the journal file needs to be 
................................................................................
      if( pPager->pInJournal && (int)needSyncPgno<=pPager->origDbSize ){
        sqlite3BitvecClear(pPager->pInJournal, needSyncPgno);
      }
      pagerLeave(pPager);
      return rc;
    }
    pPager->needSync = 1;
    pPgHdr->flags |= PGHDR_NEED_SYNC;
    pPgHdr->flags |= PGHDR_IN_JOURNAL;
    makeDirty(pPgHdr);
    sqlite3PagerUnref(pPgHdr);
  }

  pagerLeave(pPager);
  return SQLITE_OK;
}
#endif

/*
** Return a pointer to the data for the specified page.
*/
void *sqlite3PagerGetData(DbPage *pPg){
  assert( pPg->nRef>0 );
  return pPg->pData;
}

/*
** Return a pointer to the Pager.nExtra bytes of "extra" space 
** allocated along with the specified page.
*/
void *sqlite3PagerGetExtra(DbPage *pPg){
  Pager *pPager = pPg->pPager;
  return (pPager?pPg->pExtra:0);
}

/*
** Get/set the locking-mode for this pager. Parameter eMode must be one
** of PAGER_LOCKINGMODE_QUERY, PAGER_LOCKINGMODE_NORMAL or 
** PAGER_LOCKINGMODE_EXCLUSIVE. If the parameter is not _QUERY, then
** the locking-mode is set to the value specified.
................................................................................
*/
i64 sqlite3PagerJournalSizeLimit(Pager *pPager, i64 iLimit){
  if( iLimit>=-1 ){
    pPager->journalSizeLimit = iLimit;
  }
  return pPager->journalSizeLimit;
}

void sqlite3PagerAlwaysRollback(Pager *pPager){
  pPager->alwaysRollback = 1;
}

#endif /* SQLITE_OMIT_DISKIO */

**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite page cache
** subsystem.  The page cache subsystem reads and writes a file a page
** at a time and provides a journal for rollback.
**
** @(#) $Id: pager.h,v 1.77 2008/07/16 18:17:56 danielk1977 Exp $
*/

#ifndef _PAGER_H_
#define _PAGER_H_

/*
** If defined as non-zero, auto-vacuum is enabled by default. Otherwise
................................................................................
#define PAGER_JOURNALMODE_PERSIST     1   /* Commit by zeroing journal header */
#define PAGER_JOURNALMODE_OFF         2   /* Journal omitted.  */

/*
** See source code comments for a detailed description of the following
** routines:
*/
int sqlite3PagerOpen(sqlite3_vfs *, Pager **ppPager, const char*, int,int,int);
void sqlite3PagerSetBusyhandler(Pager*, BusyHandler *pBusyHandler);
void sqlite3PagerSetDestructor(Pager*, void(*)(DbPage*,int));
void sqlite3PagerSetReiniter(Pager*, void(*)(DbPage*,int));
int sqlite3PagerSetPagesize(Pager*, u16*);
int sqlite3PagerMaxPageCount(Pager*, int);
int sqlite3PagerReadFileheader(Pager*, int, unsigned char*);
void sqlite3PagerSetCachesize(Pager*, int);
................................................................................
void *sqlite3PagerGetData(DbPage *); 
void *sqlite3PagerGetExtra(DbPage *); 
int sqlite3PagerLockingMode(Pager *, int);
int sqlite3PagerJournalMode(Pager *, int);
i64 sqlite3PagerJournalSizeLimit(Pager *, i64);
void *sqlite3PagerTempSpace(Pager*);
int sqlite3PagerSync(Pager *pPager);


#if defined(SQLITE_ENABLE_MEMORY_MANAGEMENT) && !defined(SQLITE_OMIT_DISKIO)
  int sqlite3PagerReleaseMemory(int);
#endif

#ifdef SQLITE_HAS_CODEC
  void sqlite3PagerSetCodec(Pager*,void*(*)(void*,void*,Pgno,int),void*);

**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite page cache
** subsystem.  The page cache subsystem reads and writes a file a page
** at a time and provides a journal for rollback.
**
** @(#) $Id: pager.h,v 1.78 2008/08/20 14:49:25 danielk1977 Exp $
*/

#ifndef _PAGER_H_
#define _PAGER_H_

/*
** If defined as non-zero, auto-vacuum is enabled by default. Otherwise
................................................................................
#define PAGER_JOURNALMODE_PERSIST     1   /* Commit by zeroing journal header */
#define PAGER_JOURNALMODE_OFF         2   /* Journal omitted.  */

/*
** See source code comments for a detailed description of the following
** routines:
*/
int sqlite3PagerOpen(sqlite3_vfs *, Pager **ppPager, const char*, void(*)(DbPage*), int,int,int);
void sqlite3PagerSetBusyhandler(Pager*, BusyHandler *pBusyHandler);
void sqlite3PagerSetDestructor(Pager*, void(*)(DbPage*,int));
void sqlite3PagerSetReiniter(Pager*, void(*)(DbPage*,int));
int sqlite3PagerSetPagesize(Pager*, u16*);
int sqlite3PagerMaxPageCount(Pager*, int);
int sqlite3PagerReadFileheader(Pager*, int, unsigned char*);
void sqlite3PagerSetCachesize(Pager*, int);
................................................................................
void *sqlite3PagerGetData(DbPage *); 
void *sqlite3PagerGetExtra(DbPage *); 
int sqlite3PagerLockingMode(Pager *, int);
int sqlite3PagerJournalMode(Pager *, int);
i64 sqlite3PagerJournalSizeLimit(Pager *, i64);
void *sqlite3PagerTempSpace(Pager*);
int sqlite3PagerSync(Pager *pPager);
void sqlite3PagerAlwaysRollback(Pager *pPager);

#if defined(SQLITE_ENABLE_MEMORY_MANAGEMENT) && !defined(SQLITE_OMIT_DISKIO)
  int sqlite3PagerReleaseMemory(int);
#endif

#ifdef SQLITE_HAS_CODEC
  void sqlite3PagerSetCodec(Pager*,void*(*)(void*,void*,Pgno,int),void*);

/*
** 2008 August 05
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file implements that page cache.
**
** @(#) $Id: pcache.c,v 1.1 2008/08/20 14:49:25 danielk1977 Exp $
*/
#include "sqliteInt.h"

/*
** A complete page cache is an instance of this structure.
*/
struct PCache {
  PCache *pNextAll, *pPrevAll;        /* List of all page caches */
  int szPage;                         /* Size of every page in this cache */
  int szExtra;                        /* Size of extra space for each page */
  int nHash;                          /* Number of slots in apHash[] */
  int nPage;                          /* Total number of pages in apHash */
  int nMax;                           /* Configured cache size */
  PgHdr **apHash;                     /* Hash table for fast lookup by pgno */
  int bPurgeable;                     /* True if pages are on backing store */
  void (*xDestroy)(PgHdr*);           /* Called when refcnt goes 1->0 */
  int (*xStress)(void*);              /* Call to try to make pages clean */
  void *pStress;                      /* Argument to xStress */
  PgHdr *pClean;                      /* List of clean pages in use */
  PgHdr *pDirty;                      /* List of dirty pages */
  int nRef;                           /* Number of outstanding page refs */

  int iInUseMM;
  int iInUseDB;
};

/*
** Free slots in the page block allocator
*/
typedef struct PgFreeslot PgFreeslot;
struct PgFreeslot {
  PgFreeslot *pNext;  /* Next free slot */
};

/*
** Global data for the page cache.
**
** The maximum number of cached pages stored by the system is determined
** by the pcache.mxPage and pcache.mxPagePurgeable variables. If
** mxPage is non-zero, then the system tries to limit the number of
** cached pages stored to mxPage. In this case mxPagePurgeable is not 
** used.
**
** If mxPage is zero, then the system tries to limit the number of
** pages held by purgable caches to mxPagePurgeable.
*/
static struct PCacheGlobal {
  int isInit;                         /* True when initialized */
  sqlite3_mutex *mutex_mem2;          /* static mutex MUTEX_STATIC_MEM2 */
  sqlite3_mutex *mutex_lru;           /* static mutex MUTEX_STATIC_LRU */
  PCache *pAll;                       /* list of all page caches */
  int nPage;                          /* Number of pages */
  int nPurgeable;                     /* Number of pages in purgable caches */
  int mxPage;                   /* Globally configured page maximum */
  int mxPagePurgeable;                /* Purgeable page maximum */
  PgHdr *pLruHead, *pLruTail;         /* Global LRU list of unused pages */
  int szSlot;                         /* Size of each free slot */
  void *pStart, *pEnd;                /* Bounds of pagecache malloc range */
  PgFreeslot *pFree;                  /* Free page blocks */
} pcache = {0};

/*
** All global variables used by this module (most of which are grouped 
** together in global structure "pcache" above) except the list of all
** pager-caches starting with pcache.pAll, are protected by the static 
** SQLITE_MUTEX_STATIC_LRU mutex. A pointer to this mutex is stored in
** variable "pcache.mutex_lru".
**
** The list of all pager-caches (PCache structures) headed by pcache.pAll 
** is protected by SQLITE_MUTEX_STATIC_MEM2.
**
** Access to the contents of the individual PCache structures is not 
** protected. It is the job of the caller to ensure that these structures
** are accessed in a thread-safe manner. However, this module provides the
** functions sqlite3PcacheLock() and sqlite3PcacheUnlock() that may be used
** by the caller to increment/decrement a lock-count on an individual 
** pager-cache object. This module guarantees that the xStress() callback
** will not be invoked on a pager-cache with a non-zero lock-count except
** from within a call to sqlite3PcacheFetch() on the same pager. A call
** to sqlite3PcacheLock() may block if such an xStress() call is currently 
** underway.
**
** Before the xStress callback of a pager-cache (PCache) is invoked, the
** SQLITE_MUTEX_STATIC_MEM2 mutex is obtained and the SQLITE_MUTEX_STATIC_LRU 
** mutex released (in that order) before making the call.
*/

#define enterPcacheGlobal() sqlite3_mutex_enter(pcache.mutex_lru)
#define exitPcacheGlobal()  sqlite3_mutex_leave(pcache.mutex_lru)

/*
** Increment the reference count on both page p and its cache by n.
*/
static void page_ref(PgHdr *p, int n){
  /* This next block assert()s that the number of references to the 
  ** PCache is the sum of the number of references to all pages in
  ** the PCache. This is a bit expensive to leave turned on all the 
  ** time, even in debugging builds.
  */
#if 0
  PgHdr *pHdr;
  int nRef = 0;
  for(pHdr=p->pCache->pClean; pHdr; pHdr=pHdr->pNext) nRef += pHdr->nRef;
  for(pHdr=p->pCache->pDirty; pHdr; pHdr=pHdr->pNext) nRef += pHdr->nRef;
  assert( p->pCache->nRef==nRef );
#endif
  p->nRef += n;
  p->pCache->nRef += n;
}

/********************************** Linked List Management ********************/

static int check_hash_count(PCache *pCache){
  int i;
  int nPage = 0;
  for(i=0; i<pCache->nHash; i++){
    PgHdr *p;
    for(p=pCache->apHash[i]; p; p=p->pNextHash){
      nPage++;
    }
  }
  assert( nPage==pCache->nPage );
  return 1;
}

/*
** Remove a page from its hash table (PCache.apHash[]).
*/
static void pcacheRemoveFromHash(PgHdr *pPage){
  if( pPage->pPrevHash ){
    pPage->pPrevHash->pNextHash = pPage->pNextHash;
  }else{
    PCache *pCache = pPage->pCache;
    u32 h = pPage->pgno % pCache->nHash;
    assert( pCache->apHash[h]==pPage );
    pCache->apHash[h] = pPage->pNextHash;
  }
  if( pPage->pNextHash ){
    pPage->pNextHash->pPrevHash = pPage->pPrevHash;
  }
  pPage->pCache->nPage--;
  assert( check_hash_count(pPage->pCache) );
}

/*
** Insert a page into the hash table
*/
static void pcacheAddToHash(PgHdr *pPage){
  PCache *pCache = pPage->pCache;
  u32 h = pPage->pgno % pCache->nHash;
  pPage->pNextHash = pCache->apHash[h];
  pPage->pPrevHash = 0;
  if( pCache->apHash[h] ){
    pCache->apHash[h]->pPrevHash = pPage;
  }
  pCache->apHash[h] = pPage;
  pCache->nPage++;
  assert( check_hash_count(pCache) );
}

/*
** Resize the hash table to nHash buckets.
*/
static int pcacheResizeHash(PCache *pCache, int nHash){
#ifdef SQLITE_MALLOC_SOFT_LIMIT
  if( nHash*sizeof(PgHdr *)>SQLITE_MALLOC_SOFT_LIMIT ){
    nHash = SQLITE_MALLOC_SOFT_LIMIT/sizeof(PgHdr *);
  }
#endif
  if( nHash>pCache->nHash ){
    PgHdr *p;
    PgHdr **pNew = (PgHdr **)sqlite3_malloc(sizeof(PgHdr *)*nHash);
    if( !pNew ){
      return SQLITE_NOMEM;
    }
    memset(pNew, 0, sizeof(PgHdr *)*nHash);
    sqlite3_free(pCache->apHash);
    pCache->apHash = pNew;
    pCache->nHash = nHash;
    pCache->nPage = 0;
   
    for(p=pCache->pClean; p; p=p->pNext){
      pcacheAddToHash(p);
    }
    for(p=pCache->pDirty; p; p=p->pNext){
      pcacheAddToHash(p);
    }
  }
  return SQLITE_OK;
}

/*
** Remove a page from a linked list that is headed by *ppHead.
** *ppHead is either PCache.pClean or PCache.pDirty.
*/
static void pcacheRemoveFromList(PgHdr **ppHead, PgHdr *pPage){
  if( pPage->pPrev ){
    pPage->pPrev->pNext = pPage->pNext;
  }else{
    assert( *ppHead==pPage );
    *ppHead = pPage->pNext;
  }
  if( pPage->pNext ){
    pPage->pNext->pPrev = pPage->pPrev;
  }
}

/*
** Add a page from a linked list that is headed by *ppHead.
** *ppHead is either PCache.pClean or PCache.pDirty.
*/
static void pcacheAddToList(PgHdr **ppHead, PgHdr *pPage){
  if( (*ppHead) ){
    (*ppHead)->pPrev = pPage;
  }
  pPage->pNext = *ppHead;
  pPage->pPrev = 0;
  *ppHead = pPage;
}

/*
** Remove a page from the global LRU list
*/
static void pcacheRemoveFromLruList(PgHdr *pPage){
  assert( sqlite3_mutex_held(pcache.mutex_lru) );
  if( pPage->pCache->bPurgeable==0 ) return;
  if( pPage->pNextLru ){
    pPage->pNextLru->pPrevLru = pPage->pPrevLru;
  }else{
    assert( pcache.pLruTail==pPage );
    pcache.pLruTail = pPage->pPrevLru;
  }
  if( pPage->pPrevLru ){
    pPage->pPrevLru->pNextLru = pPage->pNextLru;
  }else{
    assert( pcache.pLruHead==pPage );
    pcache.pLruHead = pPage->pNextLru;
  }
}

/*
** Add a page to the global LRU list.  The page is normally added
** to the front of the list so that it will be the last page recycled.
** However, if the PGHDR_REUSE_UNLIKELY bit is set, the page is added
** to the end of the LRU list so that it will be the next to be recycled.
*/
static void pcacheAddToLruList(PgHdr *pPage){
  assert( sqlite3_mutex_held(pcache.mutex_lru) );
  if( pPage->pCache->bPurgeable==0 ) return;
  if( pcache.pLruTail && (pPage->flags & PGHDR_REUSE_UNLIKELY)!=0 ){
    /* If reuse is unlikely.  Put the page at the end of the LRU list
    ** where it will be recycled sooner rather than later. 
    */
    assert( pcache.pLruHead );
    pPage->pNextLru = 0;
    pPage->pPrevLru = pcache.pLruTail;
    pcache.pLruTail->pNextLru = pPage;
    pcache.pLruTail = pPage;
    pPage->flags &= ~PGHDR_REUSE_UNLIKELY;
  }else{
    /* If reuse is possible. the page goes at the beginning of the LRU
    ** list so that it will be the last to be recycled.
    */
    if( pcache.pLruHead ){
      pcache.pLruHead->pPrevLru = pPage;
    }
    pPage->pNextLru = pcache.pLruHead;
    pcache.pLruHead = pPage;
    pPage->pPrevLru = 0;
    if( pcache.pLruTail==0 ){
      pcache.pLruTail = pPage;
    }
  }
}

/*********************************************** Memory Allocation ***********
**
** Initialize the page cache memory pool.
**
** This must be called at start-time when no page cache lines are
** checked out. This function is not threadsafe.
*/
void sqlite3PCacheBufferSetup(void *pBuf, int sz, int n){
  PgFreeslot *p;
  sz &= ~7;
  pcache.szSlot = sz;
  pcache.pStart = pBuf;
  pcache.pFree = 0;
  while( n-- ){
    p = (PgFreeslot*)pBuf;
    p->pNext = pcache.pFree;
    pcache.pFree = p;
    pBuf = (void*)&((char*)pBuf)[sz];
  }
  pcache.pEnd = pBuf;
}

/*
** Allocate a page cache line.  Look in the page cache memory pool first
** and use an element from it first if available.  If nothing is available
** in the page cache memory pool, go to the general purpose memory allocator.
*/
void *pcacheMalloc(int sz){
  assert( sqlite3_mutex_held(pcache.mutex_lru) );
  if( sz<=pcache.szSlot && pcache.pFree ){
    PgFreeslot *p = pcache.pFree;
    pcache.pFree = p->pNext;
    sqlite3StatusSet(SQLITE_STATUS_PAGECACHE_SIZE, sz);
    sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_USED, 1);
    return (void*)p;
  }else{
    void *p = sqlite3Malloc(sz);
    if( p ){
      sz = sqlite3MallocSize(p);
      sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_OVERFLOW, sz);
    }
    return p;
  }
}
void *sqlite3PageMalloc(sz){
  void *p;
  enterPcacheGlobal();
  p = pcacheMalloc(sz);
  exitPcacheGlobal();
  return p;
}

/*
** Release a pager memory allocation
*/
void pcacheFree(void *p){
  assert( sqlite3_mutex_held(pcache.mutex_lru) );
  if( p==0 ) return;
  if( p>=pcache.pStart && p<pcache.pEnd ){
    PgFreeslot *pSlot;
    sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_USED, -1);
    pSlot = (PgFreeslot*)p;
    pSlot->pNext = pcache.pFree;
    pcache.pFree = pSlot;
  }else{
    int iSize = sqlite3MallocSize(p);
    sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_OVERFLOW, -iSize);
    sqlite3_free(p);
  }
}
void sqlite3PageFree(void *p){
  enterPcacheGlobal();
  pcacheFree(p);
  exitPcacheGlobal();
}

/*
** Allocate a new page.
*/
static PgHdr *pcachePageAlloc(int szPage, int szExtra, int bPurgeable){
  PgHdr *p;
  int sz = sizeof(*p) + szPage + szExtra;
  assert( sqlite3_mutex_held(pcache.mutex_lru) );
  p = pcacheMalloc( sz );
  if( p==0 ) return 0;
  memset(p, 0, sizeof(PgHdr));
  p->pData = (void*)&p[1];
  p->pExtra = (void*)&((char*)p->pData)[szPage];

  pcache.nPage++;
  if( bPurgeable ){
    pcache.nPurgeable++;
  }

  return p;
}

/*
** Deallocate a page
*/
static void pcachePageFree(PgHdr *p){
  assert( sqlite3_mutex_held(pcache.mutex_lru) );
  pcache.nPage--;
  if( p->pCache->bPurgeable ){
    pcache.nPurgeable--;
  }
  pcacheFree(p->apSave[0]);
  pcacheFree(p->apSave[1]);
  pcacheFree(p);
}

/*
** Obtain space for a page. Try to recycle an old page if the limit on the 
** number of pages has been reached. If the limit has not been reached or
** there are no pages eligible for recycling, allocate a new page.
**
** Return a pointer to the new page, or NULL if an OOM condition occurs.
*/
static PgHdr *pcacheRecycleOrAlloc(PCache *pCache){
  PgHdr *p = 0;

  int szPage = pCache->szPage;
  int szExtra = pCache->szExtra;
  int bPurg = pCache->bPurgeable;

  assert( pcache.isInit );
  assert( sqlite3_mutex_notheld(pcache.mutex_lru) );

  enterPcacheGlobal();

  if( (pcache.mxPage && pcache.nPage>=pcache.mxPage) 
   || (!pcache.mxPage && bPurg && pcache.nPurgeable>=pcache.mxPagePurgeable)
  ){
    PCache *pCsr;

    /* If the above test succeeds, then a page will be obtained by recycling
    ** an existing page.
    */
    if( !pcache.pLruTail && SQLITE_OK==sqlite3_mutex_try(pcache.mutex_mem2) ){

      /* Invoke xStress() callbacks until the LRU list contains at least one
      ** page that can be reused or until the xStress() callback of all
      ** caches has been invoked.
      */
      for(pCsr=pcache.pAll; pCsr&&!pcache.pLruTail; pCsr=pCsr->pNextAll){
        assert( pCsr->iInUseMM==0 );
        pCsr->iInUseMM = 1;
        if( pCsr->xStress && (pCsr->iInUseDB==0 || pCache==pCsr) ){
          exitPcacheGlobal();
          pCsr->xStress(pCsr->pStress);
          enterPcacheGlobal();
        }
        pCsr->iInUseMM = 0;
      }

      sqlite3_mutex_leave(pcache.mutex_mem2);
    }

    p = pcache.pLruTail;
  }

  if( p ){
    pcacheRemoveFromLruList(p);
    pcacheRemoveFromHash(p);
    pcacheRemoveFromList(&p->pCache->pClean, p);

    /* If the always-rollback flag is set on the page being recycled, set 
    ** the always-rollback flag on the corresponding pager.
    */
    if( p->flags&PGHDR_ALWAYS_ROLLBACK ){
      assert(p->pPager);
      sqlite3PagerAlwaysRollback(p->pPager);
    }

    if( p->pCache->szPage!=szPage || p->pCache->szExtra!=szExtra ){
      pcachePageFree(p);
      p = 0;
    }
  }

  if( !p ){
    /* Allocate a new page object. */
    p = pcachePageAlloc(szPage, szExtra, bPurg);
  }

  exitPcacheGlobal();
  return p;
}

/*************************************************** General Interfaces ******
**
** Initialize and shutdown the page cache subsystem. Neither of these 
** functions are threadsafe.
*/
int sqlite3PcacheInitialize(void){
  assert( pcache.isInit==0 );
  memset(&pcache, 0, sizeof(pcache));
  if( sqlite3Config.bCoreMutex ){
    pcache.mutex_lru = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_LRU);
    pcache.mutex_mem2 = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MEM2);
    if( pcache.mutex_lru==0 || pcache.mutex_mem2==0 ){
      return SQLITE_NOMEM;
    }
  }
  pcache.isInit = 1;
  return SQLITE_OK;
}
void sqlite3PcacheShutdown(void){
  memset(&pcache, 0, sizeof(pcache));
}

/*
** Return the size in bytes of a PCache object.
*/
int sqlite3PcacheSize(void){ return sizeof(PCache); }

/*
** Create a new PCache object.  Storage space to hold the object
** has already been allocated and is passed in as the p pointer.
*/
void sqlite3PcacheOpen(
  int szPage,                  /* Size of every page */
  int szExtra,                 /* Extra space associated with each page */
  int bPurgeable,              /* True if pages are on backing store */
  void (*xDestroy)(PgHdr*),    /* Called to destroy a page */
  int (*xStress)(void*),       /* Call to try to make pages clean */
  void *pStress,               /* Argument to xStress */
  PCache *p                    /* Preallocated space for the PCache */
){
  assert( pcache.isInit );
  memset(p, 0, sizeof(PCache));
  p->szPage = szPage;
  p->szExtra = szExtra;
  p->bPurgeable = bPurgeable;
  p->xDestroy = xDestroy;
  p->xStress = xStress;
  p->pStress = pStress;
  p->nMax = 100;

  if( bPurgeable ){
    enterPcacheGlobal();
    pcache.mxPagePurgeable += p->nMax;
    exitPcacheGlobal();
  }

  /* Add the new pager-cache to the list of caches starting at pcache.pAll */
  sqlite3_mutex_enter(pcache.mutex_mem2);
  p->pNextAll = pcache.pAll;
  if( pcache.pAll ){
    pcache.pAll->pPrevAll = p;
  }
  p->pPrevAll = 0;
  pcache.pAll = p;
  sqlite3_mutex_leave(pcache.mutex_mem2);
}

void sqlite3PcacheSetPageSize(PCache *pCache, int szPage){
  assert(pCache->nPage==0);
  pCache->szPage = szPage;
}

/*
** Try to obtain a page from the cache.
*/
int sqlite3PcacheFetch(
  PCache *pCache,       /* Obtain the page from this cache */
  Pgno pgno,            /* Page number to obtain */
  int createFlag,       /* If true, create page if it does not exist already */
  PgHdr **ppPage        /* Write the page here */
){
  PgHdr *pPage;
  assert( pcache.isInit );
  assert( pCache!=0 );
  assert( pgno>0 );
  assert( pCache->iInUseDB || pCache->iInUseMM );

  /* Search the hash table for the requested page. Exit early if it is found. */
  if( pCache->apHash ){
    u32 h = pgno % pCache->nHash;
    for(pPage=pCache->apHash[h]; pPage; pPage=pPage->pNextHash){
      if( pPage->pgno==pgno ){
        if( pPage->nRef==0 && (pPage->flags & PGHDR_DIRTY)==0 ){
          enterPcacheGlobal();
          pcacheRemoveFromLruList(pPage);
          exitPcacheGlobal();
        }
        page_ref(pPage, 1);
        *ppPage = pPage;
        return SQLITE_OK;
      }
    }
  }

  if( createFlag ){
    if( pCache->nHash<=pCache->nPage ){
      int rc = pcacheResizeHash(pCache, pCache->nHash<256?256:pCache->nHash*2);
      if( rc!=SQLITE_OK ){
        return rc;
      }
    }

    pPage = pcacheRecycleOrAlloc(pCache);
    *ppPage = pPage;
    if( pPage==0 ){
      return SQLITE_NOMEM;
    }

    pPage->pPager = 0;
    pPage->flags = 0;
    pPage->pDirty = 0;
    pPage->nRef = 0;
    pPage->pgno = pgno;
    pPage->pCache = pCache;
    page_ref(pPage, 1);
    pcacheAddToList(&pCache->pClean, pPage);
    pcacheAddToHash(pPage);
  }else{
    *ppPage = 0;
  }

  return SQLITE_OK;
}

/*
** Dereference a page.  When the reference count reaches zero,
** move the page to the LRU list if it is clean.
*/
void sqlite3PcacheRelease(PgHdr *p){
  assert( p->nRef>0 );
  assert( p->pCache->iInUseDB || p->pCache->iInUseMM );
  page_ref(p, -1);
  if( p->nRef!=0 ) return;
  if( p->pCache->xDestroy ){
    p->pCache->xDestroy(p);
  }
  if( (p->flags & PGHDR_DIRTY)!=0 ) return;
  enterPcacheGlobal();
  pcacheAddToLruList(p);
  exitPcacheGlobal();
}

void sqlite3PcacheRef(PgHdr *p){
  assert(p->nRef>=0);
  page_ref(p, 1);
}

/*
** Drop a page from the cache.  This should be the only reference to
** the page.
*/
void sqlite3PcacheDrop(PgHdr *p){
  PCache *pCache;
  assert( p->pCache->iInUseDB );
  assert( p->nRef==1 );
  pCache = p->pCache;
  pCache->nRef--;
  if( p->flags & PGHDR_DIRTY ){
    pcacheRemoveFromList(&pCache->pDirty, p);
  }else{
    pcacheRemoveFromList(&pCache->pClean, p);
  }
  pcacheRemoveFromHash(p);
  enterPcacheGlobal();
  pcachePageFree(p);
  exitPcacheGlobal();
}

/*
** Make sure the page is marked as dirty.  If it isn't dirty already,
** make it so.
*/
void sqlite3PcacheMakeDirty(PgHdr *p){
  PCache *pCache;
  assert( p->pCache->iInUseDB );
  if( p->flags & PGHDR_DIRTY ) return;
  assert( (p->flags & PGHDR_DIRTY)==0 );
  assert( p->nRef>0 );
  pCache = p->pCache;
  pcacheRemoveFromList(&pCache->pClean, p);
  pcacheAddToList(&pCache->pDirty, p);
  p->flags |= PGHDR_DIRTY;
}

/*
** Make sure the page is marked as clean.  If it isn't clean already,
** make it so.
*/
void sqlite3PcacheMakeClean(PgHdr *p){
  PCache *pCache;
  assert( p->pCache->iInUseDB || p->pCache->iInUseMM );
  if( (p->flags & PGHDR_DIRTY)==0 ) return;
  assert( p->apSave[0]==0 && p->apSave[1]==0 );
  assert( p->flags & PGHDR_DIRTY );
  /* assert( p->nRef>0 ); */
  pCache = p->pCache;
  pcacheRemoveFromList(&pCache->pDirty, p);
  pcacheAddToList(&pCache->pClean, p);
  p->flags &= ~PGHDR_DIRTY;
  if( p->nRef==0 ){
    enterPcacheGlobal();
    pcacheAddToLruList(p);
    exitPcacheGlobal();
  }
}

/*
** Make every page in the cache clean.
*/
void sqlite3PcacheCleanAll(PCache *pCache){
  PgHdr *p;
  assert( pCache->iInUseDB );
  while( (p = pCache->pDirty)!=0 ){
    assert( p->apSave[0]==0 && p->apSave[1]==0 );
    pcacheRemoveFromList(&pCache->pDirty, p);
    pcacheAddToList(&pCache->pClean, p);
    p->flags &= ~PGHDR_DIRTY;
    if( p->nRef==0 ){
      enterPcacheGlobal();
      pcacheAddToLruList(p);
      exitPcacheGlobal();
    }
  }
}

/*
** Change the page number of page p to newPgno. If newPgno is 0, then the
** page object is added to the clean-list and the PGHDR_REUSE_UNLIKELY 
** flag set.
*/
void sqlite3PcacheMove(PgHdr *p, Pgno newPgno){
  assert( p->pCache->iInUseDB );
  pcacheRemoveFromHash(p);
  p->pgno = newPgno;
  if( newPgno==0 ){
    p->flags |= PGHDR_REUSE_UNLIKELY;
    enterPcacheGlobal();
    pcacheFree(p->apSave[0]);
    pcacheFree(p->apSave[1]);
    exitPcacheGlobal();
    p->apSave[0] = 0;
    p->apSave[1] = 0;
    sqlite3PcacheMakeClean(p);
  }
  pcacheAddToHash(p);
}

/*
** Set the global maximum number of pages. Return the previous value.
*/
void sqlite3PcacheGlobalMax(int mx){
  enterPcacheGlobal();
  pcache.mxPage = mx;
  exitPcacheGlobal();
}

/*
** Remove all content from a page cache
*/
void pcacheClear(PCache *pCache){
  PgHdr *p, *pNext;
  assert( sqlite3_mutex_held(pcache.mutex_lru) );
  for(p=pCache->pClean; p; p=pNext){
    pNext = p->pNext;
    pcacheRemoveFromLruList(p);
    pcachePageFree(p);
  }
  for(p=pCache->pDirty; p; p=pNext){
    pNext = p->pNext;
    pcachePageFree(p);
  }
  pCache->pClean = 0;
  pCache->pDirty = 0;
  pCache->nPage = 0;
  memset(pCache->apHash, 0, pCache->nHash*sizeof(pCache->apHash[0]));
}


/*
** Drop every cache entry whose page number is greater than "pgno".
*/
void sqlite3PcacheTruncate(PCache *pCache, Pgno pgno){
  PgHdr *p, *pNext;
  PgHdr *pDirty = pCache->pDirty;
  assert( pCache->iInUseDB );
  enterPcacheGlobal();
  for(p=pCache->pClean; p||pDirty; p=pNext){
    if( !p ){
      p = pDirty;
      pDirty = 0;
    }
    pNext = p->pNext;
    if( p->pgno>pgno ){
      if( p->nRef==0 ){
        pcacheRemoveFromHash(p);
        if( p->flags&PGHDR_DIRTY ){
          pcacheRemoveFromList(&pCache->pDirty, p);
        }else{
          pcacheRemoveFromLruList(p);
          pcacheRemoveFromList(&pCache->pClean, p);
        }
        pcachePageFree(p);
      }else{
        /* If there are references to the page, it cannot be freed. In this
        ** case, zero the page content instead.
        */
        memset(p->pData, 0, pCache->szPage);
      }
    }
  }
  exitPcacheGlobal();
}


/*
** Close a cache.
*/
void sqlite3PcacheClose(PCache *pCache){
  assert( pCache->iInUseDB==1 );

  /* Free all the pages used by this pager and remove them from the LRU
  ** list. This requires the protection of the MUTEX_STATIC_LRU mutex.
  */
  enterPcacheGlobal();
  pcacheClear(pCache);
  if( pCache->bPurgeable ){
    pcache.mxPagePurgeable -= pCache->nMax;
  }
  sqlite3_free(pCache->apHash);
  exitPcacheGlobal();

  /* Now remove the pager-cache structure itself from the list of
  ** all such structures headed by pcache.pAll. This required the
  ** MUTEX_STATIC_MEM2 mutex.
  */
  sqlite3_mutex_enter(pcache.mutex_mem2);
  assert(pCache==pcache.pAll || pCache->pPrevAll);
  assert(pCache->pNextAll==0 || pCache->pNextAll->pPrevAll==pCache);
  assert(pCache->pPrevAll==0 || pCache->pPrevAll->pNextAll==pCache);
  if( pCache->pPrevAll ){
    pCache->pPrevAll->pNextAll = pCache->pNextAll;
  }else{
    pcache.pAll = pCache->pNextAll;
  }
  if( pCache->pNextAll ){
    pCache->pNextAll->pPrevAll = pCache->pPrevAll;
  }
  sqlite3_mutex_leave(pcache.mutex_mem2);
}

/*
** Preserve the content of the page, if it has not been preserved
** already.  If idJournal==0 then this is for the overall transaction.
** If idJournal==1 then this is for the statement journal.
**
** This routine is used for in-memory databases only.
**
** Return SQLITE_OK or SQLITE_NOMEM if a memory allocation fails.
*/
int sqlite3PcachePreserve(PgHdr *p, int idJournal){
  void *x;
  int sz;
  assert( p->pCache->iInUseDB );
  assert( p->pCache->bPurgeable==0 );
  if( !p->apSave[idJournal] ){
    sz = p->pCache->szPage;
    p->apSave[idJournal] = x = sqlite3PageMalloc( sz );
    if( x==0 ) return SQLITE_NOMEM;
    memcpy(x, p->pData, sz);
  }
  return SQLITE_OK;
}

/*
** Commit a change previously preserved.
*/
void sqlite3PcacheCommit(PCache *pCache, int idJournal){
  PgHdr *p;
  assert( pCache->iInUseDB );
  enterPcacheGlobal();     /* Mutex is required to call pcacheFree() */
  for(p=pCache->pDirty; p; p=p->pNext){
    if( p->apSave[idJournal] ){
      pcacheFree(p->apSave[idJournal]);
      p->apSave[idJournal] = 0;
    }
  }
  exitPcacheGlobal();
}

/*
** Rollback a change previously preserved.
*/
void sqlite3PcacheRollback(PCache *pCache, int idJournal){
  PgHdr *p;
  int sz;
  assert( pCache->iInUseDB );
  enterPcacheGlobal();     /* Mutex is required to call pcacheFree() */
  sz = pCache->szPage;
  for(p=pCache->pDirty; p; p=p->pNext){
    if( p->apSave[idJournal] ){
      memcpy(p->pData, p->apSave[idJournal], sz);
      pcacheFree(p->apSave[idJournal]);
      p->apSave[idJournal] = 0;
    }
  }
  exitPcacheGlobal();
}

/* 
** Assert flags settings on all pages.  Debugging only.
*/
void sqlite3PcacheAssertFlags(PCache *pCache, int trueMask, int falseMask){
  PgHdr *p;
  assert( pCache->iInUseDB || pCache->iInUseMM );
  for(p=pCache->pDirty; p; p=p->pNext){
    assert( (p->flags&trueMask)==trueMask );
    assert( (p->flags&falseMask)==0 );
  }
  for(p=pCache->pClean; p; p=p->pNext){
    assert( (p->flags&trueMask)==trueMask );
    assert( (p->flags&falseMask)==0 );
  }
}

/* 
** Discard the contents of the cache.
*/
int sqlite3PcacheClear(PCache *pCache){
  assert( pCache->iInUseDB );
  assert(pCache->nRef==0);
  enterPcacheGlobal();
  pcacheClear(pCache);
  exitPcacheGlobal();
  return SQLITE_OK;
}

/*
** Merge two lists of pages connected by pDirty and in pgno order.
** Do not both fixing the pPrevDirty pointers.
*/
static PgHdr *pcacheMergeDirtyList(PgHdr *pA, PgHdr *pB){
  PgHdr result, *pTail;
  pTail = &result;
  while( pA && pB ){
    if( pA->pgno<pB->pgno ){
      pTail->pDirty = pA;
      pTail = pA;
      pA = pA->pDirty;
    }else{
      pTail->pDirty = pB;
      pTail = pB;
      pB = pB->pDirty;
    }
  }
  if( pA ){
    pTail->pDirty = pA;
  }else if( pB ){
    pTail->pDirty = pB;
  }else{
    pTail->pDirty = 0;
  }
  return result.pDirty;
}

/*
** Sort the list of pages in accending order by pgno.  Pages are
** connected by pDirty pointers.  The pPrevDirty pointers are
** corrupted by this sort.
*/
#define N_SORT_BUCKET_ALLOC 25
#define N_SORT_BUCKET       25
#ifdef SQLITE_TEST
  int sqlite3_pager_n_sort_bucket = 0;
  #undef N_SORT_BUCKET
  #define N_SORT_BUCKET \
   (sqlite3_pager_n_sort_bucket?sqlite3_pager_n_sort_bucket:N_SORT_BUCKET_ALLOC)
#endif
static PgHdr *pcacheSortDirtyList(PgHdr *pIn){
  PgHdr *a[N_SORT_BUCKET_ALLOC], *p;
  int i;
  memset(a, 0, sizeof(a));
  while( pIn ){
    p = pIn;
    pIn = p->pDirty;
    p->pDirty = 0;
    for(i=0; i<N_SORT_BUCKET-1; i++){
      if( a[i]==0 ){
        a[i] = p;
        break;
      }else{
        p = pcacheMergeDirtyList(a[i], p);
        a[i] = 0;
      }
    }
    if( i==N_SORT_BUCKET-1 ){
      /* Coverage: To get here, there need to be 2^(N_SORT_BUCKET) 
      ** elements in the input list. This is possible, but impractical.
      ** Testing this line is the point of global variable
      ** sqlite3_pager_n_sort_bucket.
      */
      a[i] = pcacheMergeDirtyList(a[i], p);
    }
  }
  p = a[0];
  for(i=1; i<N_SORT_BUCKET; i++){
    p = pcacheMergeDirtyList(p, a[i]);
  }
  return p;
}

/*
** Return a list of all dirty pages in the cache, sorted by page number.
*/
PgHdr *sqlite3PcacheDirtyList(PCache *pCache){
  PgHdr *p;
  assert( pCache->iInUseDB );
  for(p=pCache->pDirty; p; p=p->pNext){
    p->pDirty = p->pNext;
  }
  return pcacheSortDirtyList(pCache->pDirty);
}

/*
** This function searches cache pCache for a dirty page for which the
** reference count is zero. If such a page can be found, the PgHdr.pDirty
** pointer is set to 0 and a pointer to the page is returned. If no
** such page is found, 0 is returned.
**
** This is used by the pager module to implement the xStress callback.
*/
PgHdr *sqlite3PcacheDirtyPage(PCache *pCache){
  PgHdr *p = 0;
  assert( pCache->iInUseMM );
#if 1
  PgHdr *pIter;
  Pgno min_pgno;
  for(pIter=pCache->pDirty; pIter; pIter=pIter->pNext){
    if( pIter->nRef==0 && (p==0 || pIter->pgno<min_pgno) ){
      p = pIter;
      min_pgno = pIter->pgno;
    }
  }
#else
  for(p=pCache->pDirty; p && p->nRef; p=p->pNext);
#endif
  if( p ){
    p->pDirty = 0;
  }
  return p;
}

/* 
** Return the total number of outstanding page references.
*/
int sqlite3PcacheRefCount(PCache *pCache){
  return pCache->nRef;
}

/* 
** Return the total number of pages in the cache.
*/
int sqlite3PcachePagecount(PCache *pCache){
  assert( pCache->iInUseDB || pCache->iInUseMM );
  assert( pCache->nPage>=0 );
  return pCache->nPage;
}

#ifdef SQLITE_CHECK_PAGES
/*
** This function is used by the pager.c module to iterate through all 
** pages in the cache. At present, this is only required if the
** SQLITE_CHECK_PAGES macro (used for debugging) is specified.
*/
void sqlite3PcacheIterate(PCache *pCache, void (*xIter)(PgHdr *)){
  PgHdr *p;
  assert( pCache->iInUseDB || pCache->iInUseMM );
  for(p=pCache->pClean; p; p=p->pNext){
    xIter(p);
  }
  for(p=pCache->pDirty; p; p=p->pNext){
    xIter(p);
  }
}
#endif

/* 
** Set flags on all pages in the page cache 
*/
void sqlite3PcacheSetFlags(PCache *pCache, int andMask, int orMask){
  PgHdr *p;
  assert( pCache->iInUseDB || pCache->iInUseMM );
  for(p=pCache->pDirty; p; p=p->pNext){
    p->flags = (p->flags&andMask)|orMask;
  }
  for(p=pCache->pClean; p; p=p->pNext){
    p->flags = (p->flags&andMask)|orMask;
  }
}

/*
** Set the suggested cache-size value.
*/
int sqlite3PcacheGetCachesize(PCache *pCache){
  return pCache->nMax;
}

/*
** Set the suggested cache-size value.
*/
void sqlite3PcacheSetCachesize(PCache *pCache, int mxPage){
  if( mxPage<10 ){
    mxPage = 10;
  }
  if( pCache->bPurgeable ){
    enterPcacheGlobal();
    pcache.mxPagePurgeable -= pCache->nMax;
    pcache.mxPagePurgeable += mxPage;
    exitPcacheGlobal();
  }
  pCache->nMax = mxPage;
}

/*
** Lock a pager-cache.
*/
void sqlite3PcacheLock(PCache *pCache){
  pCache->iInUseDB++;
  if( pCache->iInUseMM && pCache->iInUseDB==1 ){
    pCache->iInUseDB = 0;
    sqlite3_mutex_enter(pcache.mutex_mem2);
    assert( pCache->iInUseMM==0 && pCache->iInUseDB==0 );
    pCache->iInUseDB = 1;
    sqlite3_mutex_leave(pcache.mutex_mem2);
  }
}

/*
** Unlock a pager-cache.
*/
void sqlite3PcacheUnlock(PCache *pCache){
  pCache->iInUseDB--;
  assert( pCache->iInUseDB>=0 );
}

/*
** 2008 August 05
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite page cache
** subsystem. 
**
** @(#) $Id: pcache.h,v 1.1 2008/08/20 14:49:25 danielk1977 Exp $
*/

#ifndef _PCACHE_H_

typedef struct PgHdr PgHdr;
typedef struct PCache PCache;

/*
** Every page in the cache is controlled by an instance of the following
** structure.
*/
struct PgHdr {
  u32 flags;                     /* PGHDR flags defined below */
  void *pData;                   /* Content of this page */
  void *pExtra;                  /* Extra content */
  PgHdr *pDirty;                 /* Transient list of dirty pages */
  Pgno pgno;                     /* Page number for this page */
  Pager *pPager;
#ifdef SQLITE_CHECK_PAGES
  u32 pageHash;
#endif
  /*** Public data is above. All that follows is private to pcache.c ***/
  PCache *pCache;                /* Cache that owns this page */
  PgHdr *pNextHash, *pPrevHash;  /* Hash collision chain for PgHdr.pgno */
  PgHdr *pNext, *pPrev;          /* List of clean or dirty pages */
  PgHdr *pNextLru, *pPrevLru;    /* Part of global LRU list */
  int nRef;                      /* Number of users of this page */
  void *apSave[2];               /* Journal entries for in-memory databases */
};

/* Bit values for PgHdr.flags */
#define PGHDR_IN_JOURNAL        0x001  /* Page is in rollback journal */
#define PGHDR_IN_STMTJRNL       0x002  /* Page is in the statement journal */
#define PGHDR_DIRTY             0x004  /* Page has changed */
#define PGHDR_NEED_SYNC         0x008  /* Peed to fsync this page */
#define PGHDR_ALWAYS_ROLLBACK   0x010  /* Force writing to journal */
#define PGHDR_NEED_READ         0x020  /* Content is unread */
#define PGHDR_IS_INIT           0x040  /* pData is initialized */
#define PGHDR_REUSE_UNLIKELY    0x080  /* Hint: Reuse is unlikely */


/* Initialize and shutdown the page cache subsystem */
int sqlite3PcacheInitialize(void);
void sqlite3PcacheShutdown(void);

/* Page cache buffer management:
** These routines implement SQLITE_CONFIG_PAGECACHE.
*/
void sqlite3PCacheBufferSetup(void *, int sz, int n);
void *sqlite3PCacheMalloc(int sz);
void sqlite3PCacheFree(void*);

/* Create a new pager cache.
** Under memory stress, invoke xStress to try to make pages clean.
** Only clean and unpinned pages can be reclaimed.
*/
void sqlite3PcacheOpen(
  int szPage,                  /* Size of every page */
  int szExtra,                 /* Extra space associated with each page */
  int bPurgeable,              /* True if pages are on backing store */
  void (*xDestroy)(PgHdr *),   /* Called to destroy a page */
  int (*xStress)(void*),       /* Call to try to make pages clean */
  void *pStress,               /* Argument to xStress */
  PCache *pToInit              /* Preallocated space for the PCache */
);

/* Modify the page-size after the cache has been created. */
void sqlite3PcacheSetPageSize(PCache *, int);

/* Return the size in bytes of a PCache object.  Used to preallocate
** storage space.
*/
int sqlite3PcacheSize(void);

/* One release per successful fetch.  Page is pinned until released.
** Reference counted. 
*/
int sqlite3PcacheFetch(PCache*, Pgno, int createFlag, PgHdr**);
void sqlite3PcacheRelease(PgHdr*);

void sqlite3PcacheDrop(PgHdr*);         /* Remove page from cache */
void sqlite3PcacheMakeDirty(PgHdr*);    /* Make sure page is marked dirty */
void sqlite3PcacheMakeClean(PgHdr*);    /* Mark a single page as clean */
void sqlite3PcacheCleanAll(PCache*);    /* Mark all dirty list pages as clean */

/* Change a page number.  Used by incr-vacuum. */
void sqlite3PcacheMove(PgHdr*, Pgno);

/* Set a global maximum page count for all page caches. 
** If the sum of individual cache maxes exceed the global max, the
** individuals are scaled down proportionally. 
*/
void sqlite3PcacheGlobalMax(int N);

/* Remove all pages with pgno>x.  Reset the cache if x==0 */
void sqlite3PcacheTruncate(PCache*, Pgno x);

/* Routines used to implement transactions on memory-only databases. */
int sqlite3PcachePreserve(PgHdr*, int);    /* Preserve current page content */
void sqlite3PcacheCommit(PCache*, int);    /* Drop preserved copy */
void sqlite3PcacheRollback(PCache*, int);  /* Rollback to preserved copy */

/* Get a list of all dirty pages in the cache, sorted by page number */
PgHdr *sqlite3PcacheDirtyList(PCache*);

/* Query the cache for a dirty page with a zero ref-count */
PgHdr *sqlite3PcacheDirtyPage(PCache *);

/* Reset and close the cache object */
void sqlite3PcacheClose(PCache*);

/* Set flags on all pages in the page cache */
void sqlite3PcacheSetFlags(PCache*, int andMask, int orMask);

/* Assert flags settings on all pages.  Debugging only */
void sqlite3PcacheAssertFlags(PCache*, int trueMask, int falseMask);

/* Return true if the number of dirty pages is 0 or 1 */
int sqlite3PcacheZeroOrOneDirtyPages(PCache*);

/* Discard the contents of the cache */
int sqlite3PcacheClear(PCache*);

/* Return the total number of outstanding page references */
int sqlite3PcacheRefCount(PCache*);

/* Increment the reference count of an existing page */
void sqlite3PcacheRef(PgHdr*);

/* Return the total number of pages stored in the cache */
int sqlite3PcachePagecount(PCache*);

/* Iterate through all pages currently stored in the cache. This interface
** is only available if SQLITE_CHECK_PAGES is defined when the library is 
** built.
*/
void sqlite3PcacheIterate(PCache *pCache, void (*xIter)(PgHdr *));

/* Set and get the suggested cache-size for the specified pager-cache. If
** a global maximum on the number of pages cached by the system is 
** configured via the sqlite3PcacheGlobalMax() API, then the suggested
** cache-sizes are not used at all.
**
** If no global maximum is configured, then the system attempts to limit
** the total number of pages cached by purgeable pager-caches to the sum
** of the suggested cache-sizes.
*/
int sqlite3PcacheGetCachesize(PCache *);
void sqlite3PcacheSetCachesize(PCache *, int);

/* Lock and unlock a pager-cache object. The PcacheLock() function may 
** block if the lock is temporarily available. While a pager-cache is locked,
** the system guarantees that any configured xStress() callback will not
** be invoked by any thread other than the one holding the lock.
*/
void sqlite3PcacheLock(PCache *);
void sqlite3PcacheUnlock(PCache *);

#endif /* _PCACHE_H_ */

**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.755 2008/08/13 19:11:48 drh Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** Include the configuration header output by 'configure' if we're using the
** autoconf-based build
................................................................................
** Defer sourcing vdbe.h and btree.h until after the "u8" and 
** "BusyHandler" typedefs. vdbe.h also requires a few of the opaque
** pointer types (i.e. FuncDef) defined above.
*/
#include "btree.h"
#include "vdbe.h"
#include "pager.h"


#include "os.h"
#include "mutex.h"


/*
** Each database file to be accessed by the system is an instance
................................................................................
  u8 needCollSeq;      /* True if sqlite3GetFuncCollSeq() might be called */
  u8 flags;            /* Some combination of SQLITE_FUNC_* */
  void *pUserData;     /* User data parameter */
  FuncDef *pNext;      /* Next function with same name */
  void (*xFunc)(sqlite3_context*,int,sqlite3_value**); /* Regular function */
  void (*xStep)(sqlite3_context*,int,sqlite3_value**); /* Aggregate step */
  void (*xFinalize)(sqlite3_context*);                /* Aggregate finializer */
  char zName[1];       /* SQL name of the function.  MUST BE LAST */
};

/*
** Each SQLite module (virtual table definition) is defined by an
** instance of the following structure, stored in the sqlite3.aModule
** hash table.
*/
................................................................................
void sqlite3StatusAdd(int, int);
void sqlite3StatusSet(int, int);

int sqlite3IsNaN(double);

void sqlite3VXPrintf(StrAccum*, int, const char*, va_list);
char *sqlite3MPrintf(sqlite3*,const char*, ...);

char *sqlite3VMPrintf(sqlite3*,const char*, va_list);
char *sqlite3MAppendf(sqlite3*,char*,const char*,...);
#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
  void sqlite3DebugPrintf(const char*, ...);
#endif
#if defined(SQLITE_TEST)
  void *sqlite3TestTextToPtr(const char*);
................................................................................
ExprList *sqlite3ExprListDup(sqlite3*,ExprList*);
SrcList *sqlite3SrcListDup(sqlite3*,SrcList*);
IdList *sqlite3IdListDup(sqlite3*,IdList*);
Select *sqlite3SelectDup(sqlite3*,Select*);
FuncDef *sqlite3FindFunction(sqlite3*,const char*,int,int,u8,int);
void sqlite3RegisterBuiltinFunctions(sqlite3*);
void sqlite3RegisterDateTimeFunctions(sqlite3*);

#ifdef SQLITE_DEBUG
  int sqlite3SafetyOn(sqlite3*);
  int sqlite3SafetyOff(sqlite3*);
#else
# define sqlite3SafetyOn(A) 0
# define sqlite3SafetyOff(A) 0
#endif

**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.756 2008/08/20 14:49:25 danielk1977 Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** Include the configuration header output by 'configure' if we're using the
** autoconf-based build
................................................................................
** Defer sourcing vdbe.h and btree.h until after the "u8" and 
** "BusyHandler" typedefs. vdbe.h also requires a few of the opaque
** pointer types (i.e. FuncDef) defined above.
*/
#include "btree.h"
#include "vdbe.h"
#include "pager.h"
#include "pcache.h"

#include "os.h"
#include "mutex.h"


/*
** Each database file to be accessed by the system is an instance
................................................................................
  u8 needCollSeq;      /* True if sqlite3GetFuncCollSeq() might be called */
  u8 flags;            /* Some combination of SQLITE_FUNC_* */
  void *pUserData;     /* User data parameter */
  FuncDef *pNext;      /* Next function with same name */
  void (*xFunc)(sqlite3_context*,int,sqlite3_value**); /* Regular function */
  void (*xStep)(sqlite3_context*,int,sqlite3_value**); /* Aggregate step */
  void (*xFinalize)(sqlite3_context*);                /* Aggregate finializer */
  char *zName;         /* SQL name of the function. */
};

/*
** Each SQLite module (virtual table definition) is defined by an
** instance of the following structure, stored in the sqlite3.aModule
** hash table.
*/
................................................................................
void sqlite3StatusAdd(int, int);
void sqlite3StatusSet(int, int);

int sqlite3IsNaN(double);

void sqlite3VXPrintf(StrAccum*, int, const char*, va_list);
char *sqlite3MPrintf(sqlite3*,const char*, ...);
char *sqlite3MAppendf(sqlite3 *, char *, const char *, ...);
char *sqlite3VMPrintf(sqlite3*,const char*, va_list);
char *sqlite3MAppendf(sqlite3*,char*,const char*,...);
#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
  void sqlite3DebugPrintf(const char*, ...);
#endif
#if defined(SQLITE_TEST)
  void *sqlite3TestTextToPtr(const char*);
................................................................................
ExprList *sqlite3ExprListDup(sqlite3*,ExprList*);
SrcList *sqlite3SrcListDup(sqlite3*,SrcList*);
IdList *sqlite3IdListDup(sqlite3*,IdList*);
Select *sqlite3SelectDup(sqlite3*,Select*);
FuncDef *sqlite3FindFunction(sqlite3*,const char*,int,int,u8,int);
void sqlite3RegisterBuiltinFunctions(sqlite3*);
void sqlite3RegisterDateTimeFunctions(sqlite3*);
int sqlite3GetBuiltinFunction(const char *, int, FuncDef **);
#ifdef SQLITE_DEBUG
  int sqlite3SafetyOn(sqlite3*);
  int sqlite3SafetyOff(sqlite3*);
#else
# define sqlite3SafetyOn(A) 0
# define sqlite3SafetyOff(A) 0
#endif

**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing all sorts of SQLite interfaces.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test1.c,v 1.318 2008/08/12 15:04:59 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>

/*
................................................................................
  extern int sqlite3_sync_count, sqlite3_fullsync_count;
  extern int sqlite3_opentemp_count;
  extern int sqlite3_like_count;
  extern int sqlite3_xferopt_count;
  extern int sqlite3_pager_readdb_count;
  extern int sqlite3_pager_writedb_count;
  extern int sqlite3_pager_writej_count;
  extern int sqlite3_pager_pgfree_count;
#if SQLITE_OS_UNIX && defined(SQLITE_TEST) && SQLITE_THREADSAFE
  extern int threadsOverrideEachOthersLocks;
#endif
#if SQLITE_OS_WIN
  extern int sqlite3_os_type;
#endif
#ifdef SQLITE_DEBUG
................................................................................
      (char*)&sqlite3_xferopt_count, TCL_LINK_INT);
  Tcl_LinkVar(interp, "sqlite3_pager_readdb_count",
      (char*)&sqlite3_pager_readdb_count, TCL_LINK_INT);
  Tcl_LinkVar(interp, "sqlite3_pager_writedb_count",
      (char*)&sqlite3_pager_writedb_count, TCL_LINK_INT);
  Tcl_LinkVar(interp, "sqlite3_pager_writej_count",
      (char*)&sqlite3_pager_writej_count, TCL_LINK_INT);
  Tcl_LinkVar(interp, "sqlite3_pager_pgfree_count",
      (char*)&sqlite3_pager_pgfree_count, TCL_LINK_INT);
#ifndef SQLITE_OMIT_UTF16
  Tcl_LinkVar(interp, "unaligned_string_counter",
      (char*)&unaligned_string_counter, TCL_LINK_INT);
#endif
#if SQLITE_OS_UNIX && defined(SQLITE_TEST) && SQLITE_THREADSAFE
  Tcl_LinkVar(interp, "threadsOverrideEachOthersLocks",
      (char*)&threadsOverrideEachOthersLocks, TCL_LINK_INT);

**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing all sorts of SQLite interfaces.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test1.c,v 1.319 2008/08/20 14:49:25 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>

/*
................................................................................
  extern int sqlite3_sync_count, sqlite3_fullsync_count;
  extern int sqlite3_opentemp_count;
  extern int sqlite3_like_count;
  extern int sqlite3_xferopt_count;
  extern int sqlite3_pager_readdb_count;
  extern int sqlite3_pager_writedb_count;
  extern int sqlite3_pager_writej_count;

#if SQLITE_OS_UNIX && defined(SQLITE_TEST) && SQLITE_THREADSAFE
  extern int threadsOverrideEachOthersLocks;
#endif
#if SQLITE_OS_WIN
  extern int sqlite3_os_type;
#endif
#ifdef SQLITE_DEBUG
................................................................................
      (char*)&sqlite3_xferopt_count, TCL_LINK_INT);
  Tcl_LinkVar(interp, "sqlite3_pager_readdb_count",
      (char*)&sqlite3_pager_readdb_count, TCL_LINK_INT);
  Tcl_LinkVar(interp, "sqlite3_pager_writedb_count",
      (char*)&sqlite3_pager_writedb_count, TCL_LINK_INT);
  Tcl_LinkVar(interp, "sqlite3_pager_writej_count",
      (char*)&sqlite3_pager_writej_count, TCL_LINK_INT);


#ifndef SQLITE_OMIT_UTF16
  Tcl_LinkVar(interp, "unaligned_string_counter",
      (char*)&unaligned_string_counter, TCL_LINK_INT);
#endif
#if SQLITE_OS_UNIX && defined(SQLITE_TEST) && SQLITE_THREADSAFE
  Tcl_LinkVar(interp, "threadsOverrideEachOthersLocks",
      (char*)&threadsOverrideEachOthersLocks, TCL_LINK_INT);

**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the pager.c module in SQLite.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test2.c,v 1.59 2008/07/12 14:52:20 drh Exp $
*/
#include "sqliteInt.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

................................................................................
  char zBuf[100];
  if( argc!=3 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " FILENAME N-PAGE\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[2], &nPage) ) return TCL_ERROR;
  rc = sqlite3PagerOpen(sqlite3_vfs_find(0), &pPager, argv[1], 0, 0,
      SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_MAIN_DB);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  sqlite3PagerSetCachesize(pPager, nPage);
  pageSize = test_pagesize;
................................................................................
  pPage = sqlite3PagerLookup(pPager, pgno);
  if( pPage ){
    sqlite3_snprintf(sizeof(zBuf),zBuf,"%p",pPage);
    Tcl_AppendResult(interp, zBuf, 0);
  }
  return TCL_OK;
}





















/*
** Usage:   pager_truncate ID PGNO
*/
static int pager_truncate(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
................................................................................
    { "page_get",                (Tcl_CmdProc*)page_get            },
    { "page_lookup",             (Tcl_CmdProc*)page_lookup         },
    { "page_unref",              (Tcl_CmdProc*)page_unref          },
    { "page_read",               (Tcl_CmdProc*)page_read           },
    { "page_write",              (Tcl_CmdProc*)page_write          },
    { "page_number",             (Tcl_CmdProc*)page_number         },
    { "pager_truncate",          (Tcl_CmdProc*)pager_truncate      },

#ifndef SQLITE_OMIT_DISKIO
    { "fake_big_file",           (Tcl_CmdProc*)fake_big_file       },
#endif
    { "sqlite3BitvecBuiltinTest",(Tcl_CmdProc*)testBitvecBuiltinTest},
  };
  int i;
  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){

**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the pager.c module in SQLite.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test2.c,v 1.60 2008/08/20 14:49:25 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

................................................................................
  char zBuf[100];
  if( argc!=3 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " FILENAME N-PAGE\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[2], &nPage) ) return TCL_ERROR;
  rc = sqlite3PagerOpen(sqlite3_vfs_find(0), &pPager, argv[1], 0, 0, 0,
      SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_MAIN_DB);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  sqlite3PagerSetCachesize(pPager, nPage);
  pageSize = test_pagesize;
................................................................................
  pPage = sqlite3PagerLookup(pPager, pgno);
  if( pPage ){
    sqlite3_snprintf(sizeof(zBuf),zBuf,"%p",pPage);
    Tcl_AppendResult(interp, zBuf, 0);
  }
  return TCL_OK;
}

/*
** Usage:   pcache_global_max NPAGE
*/
static int pcache_global_max(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  const char **argv      /* Text of each argument */
){
  int nPage;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " NPAGE\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], &nPage) ) return TCL_ERROR;
  sqlite3PcacheGlobalMax(nPage);
  return TCL_OK;
}

/*
** Usage:   pager_truncate ID PGNO
*/
static int pager_truncate(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
................................................................................
    { "page_get",                (Tcl_CmdProc*)page_get            },
    { "page_lookup",             (Tcl_CmdProc*)page_lookup         },
    { "page_unref",              (Tcl_CmdProc*)page_unref          },
    { "page_read",               (Tcl_CmdProc*)page_read           },
    { "page_write",              (Tcl_CmdProc*)page_write          },
    { "page_number",             (Tcl_CmdProc*)page_number         },
    { "pager_truncate",          (Tcl_CmdProc*)pager_truncate      },
    { "pcache_global_max",       (Tcl_CmdProc*)pcache_global_max   },
#ifndef SQLITE_OMIT_DISKIO
    { "fake_big_file",           (Tcl_CmdProc*)fake_big_file       },
#endif
    { "sqlite3BitvecBuiltinTest",(Tcl_CmdProc*)testBitvecBuiltinTest},
  };
  int i;
  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){

**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the virtual table interfaces.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test8.c,v 1.73 2008/08/12 14:48:41 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>

#ifndef SQLITE_OMIT_VIRTUALTABLE
................................................................................
  sqlite3_stmt *pStmt;
};

static int simulateVtabError(echo_vtab *p, const char *zMethod){
  const char *zErr;
  char zVarname[128];
  zVarname[127] = '\0';
  sqlite3_snprintf(127, zVarname, 
                   "echo_module_fail(%s,%s)", zMethod, p->zTableName);
  zErr = Tcl_GetVar(p->interp, zVarname, TCL_GLOBAL_ONLY);
  if( zErr ){
    p->base.zErrMsg = sqlite3_mprintf("echo-vtab-error: %s", zErr);
  }
  return (zErr!=0);
}

**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the virtual table interfaces.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test8.c,v 1.74 2008/08/20 14:49:25 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>

#ifndef SQLITE_OMIT_VIRTUALTABLE
................................................................................
  sqlite3_stmt *pStmt;
};

static int simulateVtabError(echo_vtab *p, const char *zMethod){
  const char *zErr;
  char zVarname[128];
  zVarname[127] = '\0';

  snprintf(zVarname, 127, "echo_module_fail(%s,%s)", zMethod, p->zTableName);
  zErr = Tcl_GetVar(p->interp, zVarname, TCL_GLOBAL_ONLY);
  if( zErr ){
    p->base.zErrMsg = sqlite3_mprintf("echo-vtab-error: %s", zErr);
  }
  return (zErr!=0);
}

**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains code used to help implement virtual tables.
**
** $Id: vtab.c,v 1.74 2008/08/02 03:50:39 drh Exp $
*/
#ifndef SQLITE_OMIT_VIRTUALTABLE
#include "sqliteInt.h"

static int createModule(
  sqlite3 *db,                    /* Database in which module is registered */
  const char *zName,              /* Name assigned to this module */
................................................................................
  /* Create a new ephemeral function definition for the overloaded
  ** function */
  pNew = sqlite3DbMallocZero(db, sizeof(*pNew) + strlen(pDef->zName) );
  if( pNew==0 ){
    return pDef;
  }
  *pNew = *pDef;

  memcpy(pNew->zName, pDef->zName, strlen(pDef->zName)+1);
  pNew->xFunc = xFunc;
  pNew->pUserData = pArg;
  pNew->flags |= SQLITE_FUNC_EPHEM;
  return pNew;
}

**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains code used to help implement virtual tables.
**
** $Id: vtab.c,v 1.75 2008/08/20 14:49:25 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_VIRTUALTABLE
#include "sqliteInt.h"

static int createModule(
  sqlite3 *db,                    /* Database in which module is registered */
  const char *zName,              /* Name assigned to this module */
................................................................................
  /* Create a new ephemeral function definition for the overloaded
  ** function */
  pNew = sqlite3DbMallocZero(db, sizeof(*pNew) + strlen(pDef->zName) );
  if( pNew==0 ){
    return pDef;
  }
  *pNew = *pDef;
  pNew->zName = (char *)&pNew[1];
  memcpy(pNew->zName, pDef->zName, strlen(pDef->zName)+1);
  pNew->xFunc = xFunc;
  pNew->pUserData = pArg;
  pNew->flags |= SQLITE_FUNC_EPHEM;
  return pNew;
}

#
#***********************************************************************
#
# The focus of this file is testing some specific characteristics of the 
# IO traffic generated by SQLite (making sure SQLite is not writing out
# more database pages than it has to, stuff like that).
#
# $Id: io.test,v 1.17 2008/07/30 17:28:04 drh Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

db close
sqlite3_simulate_device
sqlite3 db test.db -vfs devsym
................................................................................
    # Search for #3260 in os_unix.c for additional information.
    expr {[file size test.db]>1}
  } {0}
  do_test io-3.2 {
    execsql { CREATE TABLE abc(a, b) }
    nSync
    execsql {

      PRAGMA cache_size = 10;
      BEGIN;
      INSERT INTO abc VALUES('hello', 'world');
      INSERT INTO abc SELECT * FROM abc;
      INSERT INTO abc SELECT * FROM abc;
      INSERT INTO abc SELECT * FROM abc;
      INSERT INTO abc SELECT * FROM abc;

#
#***********************************************************************
#
# The focus of this file is testing some specific characteristics of the 
# IO traffic generated by SQLite (making sure SQLite is not writing out
# more database pages than it has to, stuff like that).
#
# $Id: io.test,v 1.18 2008/08/20 14:49:25 danielk1977 Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

db close
sqlite3_simulate_device
sqlite3 db test.db -vfs devsym
................................................................................
    # Search for #3260 in os_unix.c for additional information.
    expr {[file size test.db]>1}
  } {0}
  do_test io-3.2 {
    execsql { CREATE TABLE abc(a, b) }
    nSync
    execsql {
      PRAGMA temp_store = memory;
      PRAGMA cache_size = 10;
      BEGIN;
      INSERT INTO abc VALUES('hello', 'world');
      INSERT INTO abc SELECT * FROM abc;
      INSERT INTO abc SELECT * FROM abc;
      INSERT INTO abc SELECT * FROM abc;
      INSERT INTO abc SELECT * FROM abc;

# This file implements regression tests for SQLite library.  The
# focus of this file is testing for correct handling of I/O errors
# such as writes failing because the disk is full.
# 
# The tests in this file use special facilities that are only
# available in the SQLite test fixture.
#
# $Id: ioerr2.test,v 1.8 2008/07/08 15:59:52 danielk1977 Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

ifcapable !integrityck {
  finish_test
  return
................................................................................
    check_db ioerr2-4.[expr {$bPersist+2}].$::N
  }
}

do_test ioerr2-5 {
  execsql {
    CREATE TABLE t2 AS SELECT * FROM t1;

  }
  set ::sqlite_io_error_persist 0
  set ::go 1
  set rc [catch {
    for {set ::N 1} {$::N<200} {incr ::N} {
      db eval {SELECT * FROM t1 WHERE rowid IN (1, 5, 10, 15, 20)} {
        set ::sqlite_io_error_hit 0
        set ::sqlite_io_error_pending $::N
        set sql {UPDATE t2 SET b = randstr(400,400)}
        foreach {::go res} [catchsql $sql] {}
      }
    }
  } msg]
  list $rc $msg
} {1 {callback requested query abort}}

finish_test

# This file implements regression tests for SQLite library.  The
# focus of this file is testing for correct handling of I/O errors
# such as writes failing because the disk is full.
# 
# The tests in this file use special facilities that are only
# available in the SQLite test fixture.
#
# $Id: ioerr2.test,v 1.9 2008/08/20 14:49:25 danielk1977 Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

ifcapable !integrityck {
  finish_test
  return
................................................................................
    check_db ioerr2-4.[expr {$bPersist+2}].$::N
  }
}

do_test ioerr2-5 {
  execsql {
    CREATE TABLE t2 AS SELECT * FROM t1;
    PRAGMA temp_store = memory;
  }
  set ::sqlite_io_error_persist 0
  set ::go 1
  set rc [catch {
    for {set ::N 2} {$::N<200} {incr ::N} {
      db eval {SELECT * FROM t1 WHERE rowid IN (1, 5, 10, 15, 20)} {
        set ::sqlite_io_error_hit 0
        set ::sqlite_io_error_pending $::N
        set sql {UPDATE t2 SET b = randstr(400,400)}
        foreach {::go res} [catchsql $sql] {}
      }
    }
  } msg]
  list $rc $msg
} {1 {callback requested query abort}}

finish_test

#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
#
# This file contains tests of the memory allocation subsystem
#
# $Id: memsubsys1.test,v 1.9 2008/08/12 15:21:12 drh Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl
sqlite3_reset_auto_extension

# This procedure constructs a new database in test.db.  It fills
# this database with many small records (enough to force multiple
................................................................................
  sqlite3_status SQLITE_STATUS_PAGECACHE_OVERFLOW 1
  sqlite3_status SQLITE_STATUS_PAGECACHE_SIZE 1
  sqlite3_status SQLITE_STATUS_SCRATCH_USED 1
  sqlite3_status SQLITE_STATUS_SCRATCH_OVERFLOW 1
  sqlite3_status SQLITE_STATUS_SCRATCH_SIZE 1
  sqlite3_status SQLITE_STATUS_PARSER_STACK 1
}



# Test 1:  Both PAGECACHE and SCRATCH are shut down.
#
db close
sqlite3_shutdown
sqlite3_config_lookaside 0 0
sqlite3_initialize
................................................................................
set max_pagecache [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_OVERFLOW 0] 2]
#show_memstats

# Test 2:  Activate PAGECACHE with 20 pages
#
db close
sqlite3_shutdown
sqlite3_config_pagecache 1024 20
sqlite3_initialize
reset_highwater_marks
build_test_db memsubsys1-2 {PRAGMA page_size=1024}
#show_memstats
do_test memsubsys1-2.3 {
  set pg_ovfl [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_OVERFLOW 0] 2]
  set pg_used [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0] 2]

  expr {$pg_used*1024 + $pg_ovfl}
} $max_pagecache


do_test memsubsys1-2.4 {
  set pg_used [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0] 2]
} 19
do_test memsubsys1-2.5 {
  set s_used [lindex [sqlite3_status SQLITE_STATUS_SCRATCH_USED 0] 2]
} 0

# Test 3:  Activate PAGECACHE with 20 pages but use the wrong page size
# so that PAGECACHE is not used.
#
db close
sqlite3_shutdown
sqlite3_config_pagecache 512 20
sqlite3_initialize
reset_highwater_marks
build_test_db memsubsys1-3.1 {PRAGMA page_size=1024}
#show_memstats
do_test memsubsys1-3.1.3 {
  set pg_used [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0] 2]
} 0
................................................................................
  set overflow [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_OVERFLOW 0] 2]
} $max_pagecache
do_test memsubsys1-3.1.5 {
  set s_used [lindex [sqlite3_status SQLITE_STATUS_SCRATCH_USED 0] 2]
} 0
db close
sqlite3_shutdown
sqlite3_config_pagecache 2048 20
sqlite3_initialize
reset_highwater_marks
build_test_db memsubsys1-3.2 {PRAGMA page_size=2048}
#show_memstats
do_test memsubsys1-3.2.3 {
  db eval {PRAGMA page_size}
} 2048
................................................................................
  set s_used [lindex [sqlite3_status SQLITE_STATUS_SCRATCH_USED 0] 2]
} 0

# Test 4:  Activate both PAGECACHE and SCRATCH.
#
db close
sqlite3_shutdown
sqlite3_config_pagecache 1024 50
sqlite3_config_scratch 6000 2
sqlite3_initialize
reset_highwater_marks
build_test_db memsubsys1-4 {PRAGMA page_size=1024}
#show_memstats
do_test memsubsys1-4.3 {
  set pg_used [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0] 2]
} 49
do_test memsubsys1-4.4 {
  set pg_ovfl [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_OVERFLOW 0] 2]
  set pg_used [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0] 2]

  expr {$pg_used*1024 + $pg_ovfl}
} $max_pagecache


do_test memsubsys1-4.5 {
  set maxreq [lindex [sqlite3_status SQLITE_STATUS_MALLOC_SIZE 0] 2]
  expr {$maxreq<7000}
} 1
do_test memsubsys1-4.6 {
  set s_used [lindex [sqlite3_status SQLITE_STATUS_SCRATCH_USED 0] 2]
} 1

# Test 5:  Activate both PAGECACHE and SCRATCH.  But make the page size
# such that the SCRATCH allocations are too small.
#
db close
sqlite3_shutdown
sqlite3_config_pagecache 4096 24
sqlite3_config_scratch 6000 2
sqlite3_initialize
reset_highwater_marks
build_test_db memsubsys1-5 {PRAGMA page_size=4096}
#show_memstats
do_test memsubsys1-5.3 {
  set pg_used [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0] 2]
................................................................................
} 1

# Test 6:  Activate both PAGECACHE and SCRATCH with a 4k page size.
# Make it so that SCRATCH is large enough
#
db close
sqlite3_shutdown
sqlite3_config_pagecache 4096 24
sqlite3_config_scratch 25000 1
sqlite3_initialize
reset_highwater_marks
build_test_db memsubsys1-6 {PRAGMA page_size=4096}
#show_memstats
do_test memsubsys1-6.3 {
  set pg_used [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0] 2]
} 23
do_test memsubsys1-6.4 {
  set maxreq [lindex [sqlite3_status SQLITE_STATUS_MALLOC_SIZE 0] 2]

} 4096
do_test memsubsys1-6.5 {
  set s_used [lindex [sqlite3_status SQLITE_STATUS_SCRATCH_USED 0] 2]
} 1
do_test memsubsys1-6.6 {
  set s_ovfl [lindex [sqlite3_status SQLITE_STATUS_SCRATCH_OVERFLOW 0] 2]
} 0

# Test 7:  Activate both PAGECACHE and SCRATCH with a 4k page size.
# Set cache_size small so that no PAGECACHE overflow occurs.  Verify
# that maximum allocation size is small.
#
db close
sqlite3_shutdown
sqlite3_config_pagecache 4096 24
sqlite3_config_scratch 25000 1
sqlite3_initialize

reset_highwater_marks
build_test_db memsubsys1-7 {
  PRAGMA page_size=4096;
  PRAGMA cache_size=10;
  PRAGMA temp_cache_size=10;
}
#show_memstats
do_test memsubsys1-7.3 {
  set pg_used [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0] 2]
  expr {$pg_used<24}
} 1
do_test memsubsys1-7.4 {
................................................................................
} 1
do_test memsubsys1-7.6 {
  set s_used [lindex [sqlite3_status SQLITE_STATUS_SCRATCH_USED 0] 2]
} 1
do_test memsubsys1-7.7 {
  set s_ovfl [lindex [sqlite3_status SQLITE_STATUS_SCRATCH_OVERFLOW 0] 2]
} 0


db close
sqlite3_shutdown
sqlite3_config_pagecache 0 0
sqlite3_config_scratch 0 0
sqlite3_config_lookaside 100 500
sqlite3_initialize
autoinstall_test_functions
finish_test

#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
#
# This file contains tests of the memory allocation subsystem
#
# $Id: memsubsys1.test,v 1.10 2008/08/20 14:49:25 danielk1977 Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl
sqlite3_reset_auto_extension

# This procedure constructs a new database in test.db.  It fills
# this database with many small records (enough to force multiple
................................................................................
  sqlite3_status SQLITE_STATUS_PAGECACHE_OVERFLOW 1
  sqlite3_status SQLITE_STATUS_PAGECACHE_SIZE 1
  sqlite3_status SQLITE_STATUS_SCRATCH_USED 1
  sqlite3_status SQLITE_STATUS_SCRATCH_OVERFLOW 1
  sqlite3_status SQLITE_STATUS_SCRATCH_SIZE 1
  sqlite3_status SQLITE_STATUS_PARSER_STACK 1
}

set xtra_size 256

# Test 1:  Both PAGECACHE and SCRATCH are shut down.
#
db close
sqlite3_shutdown
sqlite3_config_lookaside 0 0
sqlite3_initialize
................................................................................
set max_pagecache [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_OVERFLOW 0] 2]
#show_memstats

# Test 2:  Activate PAGECACHE with 20 pages
#
db close
sqlite3_shutdown
sqlite3_config_pagecache [expr 1024+$xtra_size] 20
sqlite3_initialize
reset_highwater_marks
build_test_db memsubsys1-2 {PRAGMA page_size=1024}
#show_memstats
do_test memsubsys1-2.3 {
  set pg_ovfl [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_OVERFLOW 0] 2]
  set pg_used [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0] 2]
  expr {
    ($pg_used*1024 + $pg_ovfl) < $max_pagecache &&
    ($pg_used*(1024+$xtra_size) + $pg_ovfl) >= $max_pagecache
  }
} 1
do_test memsubsys1-2.4 {
  set pg_used [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0] 2]
} 19
do_test memsubsys1-2.5 {
  set s_used [lindex [sqlite3_status SQLITE_STATUS_SCRATCH_USED 0] 2]
} 0

# Test 3:  Activate PAGECACHE with 20 pages but use the wrong page size
# so that PAGECACHE is not used.
#
db close
sqlite3_shutdown
sqlite3_config_pagecache [expr 512+$xtra_size] 20
sqlite3_initialize
reset_highwater_marks
build_test_db memsubsys1-3.1 {PRAGMA page_size=1024}
#show_memstats
do_test memsubsys1-3.1.3 {
  set pg_used [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0] 2]
} 0
................................................................................
  set overflow [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_OVERFLOW 0] 2]
} $max_pagecache
do_test memsubsys1-3.1.5 {
  set s_used [lindex [sqlite3_status SQLITE_STATUS_SCRATCH_USED 0] 2]
} 0
db close
sqlite3_shutdown
sqlite3_config_pagecache [expr 2048+$xtra_size] 20
sqlite3_initialize
reset_highwater_marks
build_test_db memsubsys1-3.2 {PRAGMA page_size=2048}
#show_memstats
do_test memsubsys1-3.2.3 {
  db eval {PRAGMA page_size}
} 2048
................................................................................
  set s_used [lindex [sqlite3_status SQLITE_STATUS_SCRATCH_USED 0] 2]
} 0

# Test 4:  Activate both PAGECACHE and SCRATCH.
#
db close
sqlite3_shutdown
sqlite3_config_pagecache [expr 1024+$xtra_size] 50
sqlite3_config_scratch 6000 2
sqlite3_initialize
reset_highwater_marks
build_test_db memsubsys1-4 {PRAGMA page_size=1024}
#show_memstats
do_test memsubsys1-4.3 {
  set pg_used [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0] 2]
} 49
do_test memsubsys1-4.4 {
  set pg_ovfl [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_OVERFLOW 0] 2]
  set pg_used [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0] 2]
  expr {
    ($pg_used*1024 + $pg_ovfl) < $max_pagecache &&
    ($pg_used*(1024+$xtra_size) + $pg_ovfl) >= $max_pagecache
  }
} 1
do_test memsubsys1-4.5 {
  set maxreq [lindex [sqlite3_status SQLITE_STATUS_MALLOC_SIZE 0] 2]
  expr {$maxreq<7000}
} 1
do_test memsubsys1-4.6 {
  set s_used [lindex [sqlite3_status SQLITE_STATUS_SCRATCH_USED 0] 2]
} 1

# Test 5:  Activate both PAGECACHE and SCRATCH.  But make the page size
# such that the SCRATCH allocations are too small.
#
db close
sqlite3_shutdown
sqlite3_config_pagecache [expr 4096+$xtra_size] 24
sqlite3_config_scratch 6000 2
sqlite3_initialize
reset_highwater_marks
build_test_db memsubsys1-5 {PRAGMA page_size=4096}
#show_memstats
do_test memsubsys1-5.3 {
  set pg_used [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0] 2]
................................................................................
} 1

# Test 6:  Activate both PAGECACHE and SCRATCH with a 4k page size.
# Make it so that SCRATCH is large enough
#
db close
sqlite3_shutdown
sqlite3_config_pagecache [expr 4096+$xtra_size] 24
sqlite3_config_scratch 25000 1
sqlite3_initialize
reset_highwater_marks
build_test_db memsubsys1-6 {PRAGMA page_size=4096}
#show_memstats
do_test memsubsys1-6.3 {
  set pg_used [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0] 2]
} 23
do_test memsubsys1-6.4 {
  set maxreq [lindex [sqlite3_status SQLITE_STATUS_MALLOC_SIZE 0] 2]
  expr {$maxreq>4096 && $maxreq<(4096+$xtra_size)}
} 1
do_test memsubsys1-6.5 {
  set s_used [lindex [sqlite3_status SQLITE_STATUS_SCRATCH_USED 0] 2]
} 1
do_test memsubsys1-6.6 {
  set s_ovfl [lindex [sqlite3_status SQLITE_STATUS_SCRATCH_OVERFLOW 0] 2]
} 0

# Test 7:  Activate both PAGECACHE and SCRATCH with a 4k page size.
# Set cache_size small so that no PAGECACHE overflow occurs.  Verify
# that maximum allocation size is small.
#
db close
sqlite3_shutdown
sqlite3_config_pagecache [expr 4096+$xtra_size] 24
sqlite3_config_scratch 25000 1
sqlite3_initialize
pcache_global_max 15
reset_highwater_marks
build_test_db memsubsys1-7 {
  PRAGMA page_size=4096;


}
#show_memstats
do_test memsubsys1-7.3 {
  set pg_used [lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0] 2]
  expr {$pg_used<24}
} 1
do_test memsubsys1-7.4 {
................................................................................
} 1
do_test memsubsys1-7.6 {
  set s_used [lindex [sqlite3_status SQLITE_STATUS_SCRATCH_USED 0] 2]
} 1
do_test memsubsys1-7.7 {
  set s_ovfl [lindex [sqlite3_status SQLITE_STATUS_SCRATCH_OVERFLOW 0] 2]
} 0
pcache_global_max 0

db close
sqlite3_shutdown
sqlite3_config_pagecache 0 0
sqlite3_config_scratch 0 0
sqlite3_config_lookaside 100 500
sqlite3_initialize
autoinstall_test_functions
finish_test

#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
#
# $Id: mutex1.test,v 1.10 2008/07/15 00:27:35 drh Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

if {[info exists tester_do_binarylog]} {
  finish_test
  return
................................................................................
#   * Multi-threaded mode,
#   * Single-threaded mode.
#
set enable_shared_cache [sqlite3_enable_shared_cache 1]
ifcapable threadsafe {
  foreach {mode mutexes} {
    singlethread {}
    multithread  {fast static_master static_mem static_prng}
    serialized   {fast recursive static_master static_mem static_prng}
  } {
    ifcapable memorymanage {
      if {$mode ne "singlethread"} {
        lappend mutexes static_lru static_lru2 static_mem2
      }
    }

#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
#
# $Id: mutex1.test,v 1.11 2008/08/20 14:49:25 danielk1977 Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

if {[info exists tester_do_binarylog]} {
  finish_test
  return
................................................................................
#   * Multi-threaded mode,
#   * Single-threaded mode.
#
set enable_shared_cache [sqlite3_enable_shared_cache 1]
ifcapable threadsafe {
  foreach {mode mutexes} {
    singlethread {}
    multithread  {fast static_lru static_master static_mem static_mem2 static_prng }
    serialized   {fast recursive static_lru static_master static_mem static_mem2 static_prng }
  } {
    ifcapable memorymanage {
      if {$mode ne "singlethread"} {
        lappend mutexes static_lru static_lru2 static_mem2
      }
    }

#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is page cache subsystem.
#
# $Id: pager.test,v 1.30 2007/08/24 16:29:24 drh Exp $


set testdir [file dirname $argv0]
source $testdir/tester.tcl

if {[info commands pager_open]!=""} {
db close
................................................................................
  pager_stats $::p1
} {ref 1 page 1 max 10 size 0 state 1 err 0 hit 0 miss 1 ovfl 0}
do_test pager-2.3.4 {
  set ::gx [page_lookup $::p1 1]
  expr {$::gx!=""}
} {1}
do_test pager-2.3.5 {

  pager_stats $::p1
} {ref 1 page 1 max 10 size 0 state 1 err 0 hit 0 miss 1 ovfl 0}
do_test pager-2.3.6 {
  expr {$::g1==$::gx}
} {1}
do_test pager-2.3.7 {
  page_unref $::gx
  pager_stats $::p1
} {ref 1 page 1 max 10 size 0 state 1 err 0 hit 0 miss 1 ovfl 0}
do_test pager-2.4 {
  pager_stats $::p1
} {ref 1 page 1 max 10 size 0 state 1 err 0 hit 0 miss 1 ovfl 0}
do_test pager-2.5 {
  pager_pagecount $::p1
................................................................................
} {0 {}}
do_test pager-2.29 {
  page_unref $::g1
  set ::g1 [page_get $::p1 1]
  page_read $::g1
} {Page-One}
do_test pager-2.99 {

  pager_close $::p1
} {}

do_test pager-3.1 {
  set v [catch {
    set ::p1 [pager_open ptf1.db 15]
  } msg]
................................................................................
do_test pager-3.5 {
  for {set i 2} {$i<=20} {incr i} {
    set gx [page_get $::p1 $i]
    page_write $gx "Page-$i"
    page_unref $gx
  }
  pager_commit $::p1

} {}
for {set i 2} {$i<=20} {incr i} {
  do_test pager-3.6.[expr {$i-1}] [subst {
    set gx \[page_get $::p1 $i\]
    set v \[page_read \$gx\]
    page_unref \$gx
    set v
................................................................................
  } {}
  do_test pager-4.6.4 {
    pager_close $::p2
  } {}
}

do_test pager-4.99 {

  pager_close $::p1
} {}



  file delete -force ptf1.db

#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is page cache subsystem.
#
# $Id: pager.test,v 1.31 2008/08/20 14:49:25 danielk1977 Exp $


set testdir [file dirname $argv0]
source $testdir/tester.tcl

if {[info commands pager_open]!=""} {
db close
................................................................................
  pager_stats $::p1
} {ref 1 page 1 max 10 size 0 state 1 err 0 hit 0 miss 1 ovfl 0}
do_test pager-2.3.4 {
  set ::gx [page_lookup $::p1 1]
  expr {$::gx!=""}
} {1}
do_test pager-2.3.5 {
  page_unref $::gx
  pager_stats $::p1
} {ref 1 page 1 max 10 size 0 state 1 err 0 hit 0 miss 1 ovfl 0}
do_test pager-2.3.6 {
  expr {$::g1==$::gx}
} {1}
do_test pager-2.3.7 {

  pager_stats $::p1
} {ref 1 page 1 max 10 size 0 state 1 err 0 hit 0 miss 1 ovfl 0}
do_test pager-2.4 {
  pager_stats $::p1
} {ref 1 page 1 max 10 size 0 state 1 err 0 hit 0 miss 1 ovfl 0}
do_test pager-2.5 {
  pager_pagecount $::p1
................................................................................
} {0 {}}
do_test pager-2.29 {
  page_unref $::g1
  set ::g1 [page_get $::p1 1]
  page_read $::g1
} {Page-One}
do_test pager-2.99 {
  page_unref $::g1
  pager_close $::p1
} {}

do_test pager-3.1 {
  set v [catch {
    set ::p1 [pager_open ptf1.db 15]
  } msg]
................................................................................
do_test pager-3.5 {
  for {set i 2} {$i<=20} {incr i} {
    set gx [page_get $::p1 $i]
    page_write $gx "Page-$i"
    page_unref $gx
  }
  pager_commit $::p1
  page_unref $::g(1)
} {}
for {set i 2} {$i<=20} {incr i} {
  do_test pager-3.6.[expr {$i-1}] [subst {
    set gx \[page_get $::p1 $i\]
    set v \[page_read \$gx\]
    page_unref \$gx
    set v
................................................................................
  } {}
  do_test pager-4.6.4 {
    pager_close $::p2
  } {}
}

do_test pager-4.99 {
  page_unref $::g1
  pager_close $::p1
} {}



  file delete -force ptf1.db

#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is page cache subsystem.
#
# $Id: pager2.test,v 1.6 2007/03/23 18:12:07 danielk1977 Exp $


set testdir [file dirname $argv0]
source $testdir/tester.tcl

# Don't run this test file if the pager test interface [pager_open] is not
# available, or the library was compiled without in-memory database support.
................................................................................
  set v
} {0}
do_test pager2-2.3.3 {
  pager_stats $::p1
} {ref 1 page 1 max 10 size 0 state 1 err 0 hit 0 miss 1 ovfl 0}
do_test pager2-2.3.4 {
  set ::gx [page_lookup $::p1 1]

  expr {$::gx!=""}
} {1}
do_test pager2-2.3.5 {
  pager_stats $::p1
} {ref 1 page 1 max 10 size 0 state 1 err 0 hit 0 miss 1 ovfl 0}
do_test pager2-2.3.6 {
  expr {$::g1==$::gx}
} {1}
do_test pager2-2.3.7 {
  page_unref $::gx
  pager_stats $::p1
} {ref 1 page 1 max 10 size 0 state 1 err 0 hit 0 miss 1 ovfl 0}
do_test pager2-2.4 {
  pager_stats $::p1
} {ref 1 page 1 max 10 size 0 state 1 err 0 hit 0 miss 1 ovfl 0}
do_test pager2-2.5 {
  pager_pagecount $::p1
................................................................................
  lappend v $msg
} {0 {}}
do_test pager2-2.29 {
  page_unref $::g1
  set ::g1 [page_get $::p1 1]
  page_read $::g1
} {Page-One}
#do_test pager2-2.99 {
#  pager_close $::p1
#} {}

#do_test pager2-3.1 {
#  set v [catch {
#    set ::p1 [pager_open :memory: 15]
#  } msg]
#  if {$v} {lappend v $msg}
#  set v
................................................................................
do_test pager2-3.5 {
  for {set i 2} {$i<=20} {incr i} {
    set gx [page_get $::p1 $i]
    page_write $gx "Page-$i"
    page_unref $gx
  }
  pager_commit $::p1

} {}
for {set i 2} {$i<=20} {incr i} {
  do_test pager2-3.6.[expr {$i-1}] [subst {
    set gx \[page_get $::p1 $i\]
    set v \[page_read \$gx\]
    page_unref \$gx
    set v
................................................................................
      set shouldbe "Page-$j v[expr {$i-1}]"
      if {$value!=$shouldbe} {
        lappend res $value $shouldbe
      }
    }
    set res
  } {}

  do_test pager2-4.5.$i.5 {
    page_write $g1 "Page-1 v$i"
    lrange [pager_stats $p1] 8 9
  } {state 4}
  do_test pager2-4.5.$i.6 {
    for {set j 2} {$j<=20} {incr j} {
      set gx [page_get $p1 $j]
................................................................................
  do_test pager2-4.5.$i.10 {
    pager_commit $p1
    lrange [pager_stats $p1] 8 9
  } {state 1}
}

do_test pager2-4.99 {

  pager_close $::p1
} {}

} ;# ifcapable inmemory
} ;# end if( has pager_open command );


finish_test

#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is page cache subsystem.
#
# $Id: pager2.test,v 1.7 2008/08/20 14:49:25 danielk1977 Exp $


set testdir [file dirname $argv0]
source $testdir/tester.tcl

# Don't run this test file if the pager test interface [pager_open] is not
# available, or the library was compiled without in-memory database support.
................................................................................
  set v
} {0}
do_test pager2-2.3.3 {
  pager_stats $::p1
} {ref 1 page 1 max 10 size 0 state 1 err 0 hit 0 miss 1 ovfl 0}
do_test pager2-2.3.4 {
  set ::gx [page_lookup $::p1 1]
  page_unref $::gx
  expr {$::gx!=""}
} {1}
do_test pager2-2.3.5 {
  pager_stats $::p1
} {ref 1 page 1 max 10 size 0 state 1 err 0 hit 0 miss 1 ovfl 0}
do_test pager2-2.3.6 {
  expr {$::g1==$::gx}
} {1}
do_test pager2-2.3.7 {

  pager_stats $::p1
} {ref 1 page 1 max 10 size 0 state 1 err 0 hit 0 miss 1 ovfl 0}
do_test pager2-2.4 {
  pager_stats $::p1
} {ref 1 page 1 max 10 size 0 state 1 err 0 hit 0 miss 1 ovfl 0}
do_test pager2-2.5 {
  pager_pagecount $::p1
................................................................................
  lappend v $msg
} {0 {}}
do_test pager2-2.29 {
  page_unref $::g1
  set ::g1 [page_get $::p1 1]
  page_read $::g1
} {Page-One}
do_test pager2-2.99 {
  page_unref $::g1
} {}

#do_test pager2-3.1 {
#  set v [catch {
#    set ::p1 [pager_open :memory: 15]
#  } msg]
#  if {$v} {lappend v $msg}
#  set v
................................................................................
do_test pager2-3.5 {
  for {set i 2} {$i<=20} {incr i} {
    set gx [page_get $::p1 $i]
    page_write $gx "Page-$i"
    page_unref $gx
  }
  pager_commit $::p1
  page_unref $::g(1)
} {}
for {set i 2} {$i<=20} {incr i} {
  do_test pager2-3.6.[expr {$i-1}] [subst {
    set gx \[page_get $::p1 $i\]
    set v \[page_read \$gx\]
    page_unref \$gx
    set v
................................................................................
      set shouldbe "Page-$j v[expr {$i-1}]"
      if {$value!=$shouldbe} {
        lappend res $value $shouldbe
      }
    }
    set res
  } {}
breakpoint
  do_test pager2-4.5.$i.5 {
    page_write $g1 "Page-1 v$i"
    lrange [pager_stats $p1] 8 9
  } {state 4}
  do_test pager2-4.5.$i.6 {
    for {set j 2} {$j<=20} {incr j} {
      set gx [page_get $p1 $j]
................................................................................
  do_test pager2-4.5.$i.10 {
    pager_commit $p1
    lrange [pager_stats $p1] 8 9
  } {state 1}
}

do_test pager2-4.99 {
  page_unref $::g1
  pager_close $::p1
} {}

} ;# ifcapable inmemory
} ;# end if( has pager_open command );


finish_test

#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.
# The focus of the tests in this file are to verify that the
# pager optimizations implemented in version 3.3.14 work.
#
# $Id: pageropt.test,v 1.4 2008/04/14 01:00:58 drh Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

ifcapable {!pager_pragmas||secure_delete} {
  finish_test
  return
................................................................................
  global sqlite3_pager_readdb_count
  global sqlite3_pager_writedb_count
  global sqlite3_pager_writej_count
  global sqlite3_pager_pgfree_count
  set sqlite3_pager_readdb_count 0
  set sqlite3_pager_writedb_count 0
  set sqlite3_pager_writej_count 0
  set sqlite3_pager_pgfree_count 0
  set r [$db eval $sql]
  set cnt [list $sqlite3_pager_readdb_count \
                $sqlite3_pager_writedb_count \
                $sqlite3_pager_writej_count \
                $sqlite3_pager_pgfree_count]
  return [concat $cnt $r]
}

# Setup the test database
#
do_test pageropt-1.1 {
  sqlite3_soft_heap_limit 0
................................................................................
  execsql {
    PRAGMA auto_vacuum = OFF;
    PRAGMA page_size = 1024;
  }
  pagercount_sql {
    CREATE TABLE t1(x);
  }
} {0 2 0 0}
do_test pageropt-1.2 {
  pagercount_sql {
    INSERT INTO t1 VALUES(randomblob(5000));
  }
} {0 6 2 0}

# Verify that values remain in cache on for subsequent reads.
# We should not have to go back to disk.
#
do_test pageropt-1.3 {
  pagercount_sql {
    SELECT length(x) FROM t1
  }
} {0 0 0 0 5000}

# If another thread reads the database, the original cache
# remains valid.
#
sqlite3 db2 test.db
set blobcontent [db2 one {SELECT hex(x) FROM t1}]
do_test pageropt-1.4 {
  pagercount_sql {
    SELECT hex(x) FROM t1
  }
} [list 0 0 0 0 $blobcontent]

# But if the other thread modifies the database, then the cache
# must refill.
#
do_test pageropt-1.5 {
  db2 eval {CREATE TABLE t2(y)}
  pagercount_sql {
    SELECT hex(x) FROM t1
  }
} [list 6 0 0 6 $blobcontent]
do_test pageropt-1.6 {
  pagercount_sql {
    SELECT hex(x) FROM t1
  }
} [list 0 0 0 0 $blobcontent]

# Verify that the last page of an overflow chain is not read from
# disk when deleting a row.  The one row of t1(x) has four pages
# of overflow.  So deleting that row from t1 should involve reading
# the sqlite_master table (1 page) the main page of t1 (1 page) and
# the three overflow pages of t1 for a total of 5 pages.
#
................................................................................
#
do_test pageropt-2.1 {
  db close
  sqlite3 db test.db
  pagercount_sql {
    DELETE FROM t1 WHERE rowid=1
  }
} {5 3 3 0}

# When pulling pages off of the freelist, there is no reason
# to actually bring in the old content.
#
do_test pageropt-2.2 {
  db close
  sqlite3 db test.db
  pagercount_sql {
    INSERT INTO t1 VALUES(randomblob(1500));
  }
} {3 4 3 0}
do_test pageropt-2.3 {
  pagercount_sql {
    INSERT INTO t1 VALUES(randomblob(1500));
  }
} {0 4 3 0}

# Note the new optimization that when pulling the very last page off of the
# freelist we do not read the content of that page.
#
do_test pageropt-2.4 {
  pagercount_sql {
    INSERT INTO t1 VALUES(randomblob(1500));
  }
} {0 5 3 0}

# Appending a large quantity of data does not involve writing much
# to the journal file.
#
do_test pageropt-3.1 {
  pagercount_sql {
    INSERT INTO t2 SELECT * FROM t1;
  }
} {1 7 2 0}

# Once again, we do not need to read the last page of an overflow chain
# while deleting.
#
do_test pageropt-3.2 {
  pagercount_sql {
    DROP TABLE t2;
  }
} {0 2 3 0}
do_test pageropt-3.3 {
  pagercount_sql {
    DELETE FROM t1;
  }
} {0 3 3 0}

# There are now 11 pages on the freelist.  Move them all into an
# overflow chain by inserting a single large record.  Starting from
# a cold cache, only page 1, the root page of table t1, and the trunk
# of the freelist need to be read (3 pages).  And only those three
# pages need to be journalled.  But 13 pages need to be written:
# page1, the root page of table t1, and an 11 page overflow chain.
................................................................................
#
do_test pageropt-4.1 {
  db close
  sqlite3 db test.db
  pagercount_sql {
    INSERT INTO t1 VALUES(randomblob(11300))
  }
} {3 13 3 0}

# Now we delete that big entries starting from a cold cache and an
# empty freelist.  The first 10 of the 11 pages overflow chain have
# to be read, together with page1 and the root of the t1 table.  12
# reads total.  But only page1, the t1 root, and the trunk of the
# freelist need to be journalled and written back.
#
do_test pageropt-4.2 {
  db close
  sqlite3 db test.db
  pagercount_sql {
    DELETE FROM t1
  }
} {12 3 3 0}

sqlite3_soft_heap_limit $soft_limit
catch {db2 close}
finish_test

#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.
# The focus of the tests in this file are to verify that the
# pager optimizations implemented in version 3.3.14 work.
#
# $Id: pageropt.test,v 1.5 2008/08/20 14:49:25 danielk1977 Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

ifcapable {!pager_pragmas||secure_delete} {
  finish_test
  return
................................................................................
  global sqlite3_pager_readdb_count
  global sqlite3_pager_writedb_count
  global sqlite3_pager_writej_count
  global sqlite3_pager_pgfree_count
  set sqlite3_pager_readdb_count 0
  set sqlite3_pager_writedb_count 0
  set sqlite3_pager_writej_count 0

  set r [$db eval $sql]
  set cnt [list $sqlite3_pager_readdb_count \
                $sqlite3_pager_writedb_count \
                $sqlite3_pager_writej_count ]

  return [concat $cnt $r]
}

# Setup the test database
#
do_test pageropt-1.1 {
  sqlite3_soft_heap_limit 0
................................................................................
  execsql {
    PRAGMA auto_vacuum = OFF;
    PRAGMA page_size = 1024;
  }
  pagercount_sql {
    CREATE TABLE t1(x);
  }
} {0 2 0}
do_test pageropt-1.2 {
  pagercount_sql {
    INSERT INTO t1 VALUES(randomblob(5000));
  }
} {0 6 2}

# Verify that values remain in cache on for subsequent reads.
# We should not have to go back to disk.
#
do_test pageropt-1.3 {
  pagercount_sql {
    SELECT length(x) FROM t1
  }
} {0 0 0 5000}

# If another thread reads the database, the original cache
# remains valid.
#
sqlite3 db2 test.db
set blobcontent [db2 one {SELECT hex(x) FROM t1}]
do_test pageropt-1.4 {
  pagercount_sql {
    SELECT hex(x) FROM t1
  }
} [list 0 0 0 $blobcontent]

# But if the other thread modifies the database, then the cache
# must refill.
#
do_test pageropt-1.5 {
  db2 eval {CREATE TABLE t2(y)}
  pagercount_sql {
    SELECT hex(x) FROM t1
  }
} [list 6 0 0 $blobcontent]
do_test pageropt-1.6 {
  pagercount_sql {
    SELECT hex(x) FROM t1
  }
} [list 0 0 0 $blobcontent]

# Verify that the last page of an overflow chain is not read from
# disk when deleting a row.  The one row of t1(x) has four pages
# of overflow.  So deleting that row from t1 should involve reading
# the sqlite_master table (1 page) the main page of t1 (1 page) and
# the three overflow pages of t1 for a total of 5 pages.
#
................................................................................
#
do_test pageropt-2.1 {
  db close
  sqlite3 db test.db
  pagercount_sql {
    DELETE FROM t1 WHERE rowid=1
  }
} {5 3 3}

# When pulling pages off of the freelist, there is no reason
# to actually bring in the old content.
#
do_test pageropt-2.2 {
  db close
  sqlite3 db test.db
  pagercount_sql {
    INSERT INTO t1 VALUES(randomblob(1500));
  }
} {3 4 3}
do_test pageropt-2.3 {
  pagercount_sql {
    INSERT INTO t1 VALUES(randomblob(1500));
  }
} {0 4 3}

# Note the new optimization that when pulling the very last page off of the
# freelist we do not read the content of that page.
#
do_test pageropt-2.4 {
  pagercount_sql {
    INSERT INTO t1 VALUES(randomblob(1500));
  }
} {0 5 3}

# Appending a large quantity of data does not involve writing much
# to the journal file.
#
do_test pageropt-3.1 {
  pagercount_sql {
    INSERT INTO t2 SELECT * FROM t1;
  }
} {1 7 2}

# Once again, we do not need to read the last page of an overflow chain
# while deleting.
#
do_test pageropt-3.2 {
  pagercount_sql {
    DROP TABLE t2;
  }
} {0 2 3}
do_test pageropt-3.3 {
  pagercount_sql {
    DELETE FROM t1;
  }
} {0 3 3}

# There are now 11 pages on the freelist.  Move them all into an
# overflow chain by inserting a single large record.  Starting from
# a cold cache, only page 1, the root page of table t1, and the trunk
# of the freelist need to be read (3 pages).  And only those three
# pages need to be journalled.  But 13 pages need to be written:
# page1, the root page of table t1, and an 11 page overflow chain.
................................................................................
#
do_test pageropt-4.1 {
  db close
  sqlite3 db test.db
  pagercount_sql {
    INSERT INTO t1 VALUES(randomblob(11300))
  }
} {3 13 3}

# Now we delete that big entries starting from a cold cache and an
# empty freelist.  The first 10 of the 11 pages overflow chain have
# to be read, together with page1 and the root of the t1 table.  12
# reads total.  But only page1, the t1 root, and the trunk of the
# freelist need to be journalled and written back.
#
do_test pageropt-4.2 {
  db close
  sqlite3 db test.db
  pagercount_sql {
    DELETE FROM t1
  }
} {12 3 3}

sqlite3_soft_heap_limit $soft_limit
catch {db2 close}
finish_test

#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
#
# $Id: shared3.test,v 1.3 2008/06/23 09:50:52 danielk1977 Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl
db close

ifcapable !shared_cache {
  finish_test
................................................................................
  execsql {
    BEGIN;
    INSERT INTO t1 VALUES(10, randomblob(5000))
  } db1
  catchsql {select count(*) from sqlite_master} db3
} {0 1}
do_test shared3-2.8 {

  execsql {
    INSERT INTO t1 VALUES(10, randomblob(10000))
  } db1


  # If the pager-cache is really still limited to 10 pages, then the INSERT
  # statement above should have caused the pager to grab an exclusive lock
  # on the database file so that the cache could be spilled.
  #
  catchsql {select count(*) from sqlite_master} db3
} {1 {database is locked}}

#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
#
# $Id: shared3.test,v 1.4 2008/08/20 14:49:25 danielk1977 Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl
db close

ifcapable !shared_cache {
  finish_test
................................................................................
  execsql {
    BEGIN;
    INSERT INTO t1 VALUES(10, randomblob(5000))
  } db1
  catchsql {select count(*) from sqlite_master} db3
} {0 1}
do_test shared3-2.8 {
  db3 close
  execsql {
    INSERT INTO t1 VALUES(10, randomblob(10000))
  } db1
  sqlite3 db3 $alternative_name

  # If the pager-cache is really still limited to 10 pages, then the INSERT
  # statement above should have caused the pager to grab an exclusive lock
  # on the database file so that the cache could be spilled.
  #
  catchsql {select count(*) from sqlite_master} db3
} {1 {database is locked}}

#
# This file implements tests to verify that ticket #2409 has been
# fixed. More specifically, they verify that if SQLite cannot
# obtain an EXCLUSIVE lock while trying to spill the cache during
# any statement other than a COMMIT, an I/O error is returned instead
# of SQLITE_BUSY.
#
# $Id: tkt2409.test,v 1.3 2007/09/12 17:01:45 danielk1977 Exp $

# Test Outline:
#
#   tkt-2409-1.*: Cause a cache-spill during an INSERT that is within
#       a db transaction but does not start a statement transaction.
#       Verify that the transaction is automatically rolled back
#       and SQLITE_IOERR_BLOCKED is returned





#
#   tkt-2409-2.*: Cause a cache-spill while updating the change-counter
#       during a database COMMIT. Verify that the transaction is not
#       rolled back and SQLITE_BUSY is returned.
#
#   tkt-2409-3.*: Similar to 2409-1.*, but using many INSERT statements
#       within a transaction instead of just one.
#


#   tkt-2409-4.*: Similar to 2409-1.*, but rig it so that the
#       INSERT statement starts a statement transaction. Verify that
#       SQLOTE_BUSY is returned and the transaction is not rolled back.



#

set testdir [file dirname $argv0]
source $testdir/tester.tcl

ifcapable !pager_pragmas {
  finish_test
................................................................................
#
proc unread_lock_db {} {
  if {$::STMT ne ""} {
    sqlite3_finalize $::STMT
    set ::STMT ""
  }
}



# Open the db handle used by [read_lock_db].
#
sqlite3 db2 test.db
set ::STMT ""

do_test tkt2409-1.1 {
................................................................................
  read_lock_db
  set ::zShort [string repeat 0123456789 1]
  set ::zLong  [string repeat 0123456789 1500]
  catchsql {
    BEGIN;
    INSERT INTO t1 VALUES($::zShort, $::zLong);
  }
} {1 {disk I/O error}}

do_test tkt2409-1.2 {
  sqlite3_errcode $::DB
} {SQLITE_IOERR+11}

# Check the integrity of the cache.
#
integrity_check tkt2409-1.3

# Check that the transaction was rolled back. Because the INSERT
# statement in which the "I/O error" occured did not open a statement
# transaction, SQLite had no choice but to roll back the transaction.
#
do_test tkt2409-1.4 {
  unread_lock_db
  catchsql { ROLLBACK }
} {1 {cannot rollback - no transaction is active}}


set ::zShort [string repeat 0123456789 1]
set ::zLong  [string repeat 0123456789 1500]
set ::rc 1
for {set iCache 10} {$::rc} {incr iCache} {
  execsql "PRAGMA cache_size = $iCache"
  do_test tkt2409-2.1.$iCache {
................................................................................

do_test tkt2409-2.3 {
  unread_lock_db
  catchsql {
    COMMIT;
  }
} {0 {}}


do_test tkt2409-3.1 {
  db close
  set ::DB [sqlite3 db test.db; sqlite3_connection_pointer db]
  sqlite3_extended_result_codes $::DB 1
  execsql {
    PRAGMA cache_size=10;
................................................................................
  read_lock_db
  set ::zShort [string repeat 0123456789 1]
  set ::zLong  [string repeat 0123456789 1500]
  catchsql {
    BEGIN;
    INSERT INTO t1 SELECT $::zShort, $::zLong;
  }
} {1 {database is locked}}

do_test tkt2409-3.2 {
  sqlite3_errcode $::DB
} {SQLITE_BUSY}

# Check the integrity of the cache.
#
integrity_check tkt2409-3.3

# Check that the transaction was rolled back. Because the INSERT
# statement in which the "I/O error" occured did not open a statement
................................................................................
    set t1($r) 1
    append sql "INSERT INTO t1 VALUES('some-text-$r');"
  }

  read_lock_db
  execsql BEGIN
  catchsql $sql
} {1 {disk I/O error}}

do_test tkt2409-4.2 {
  sqlite3_errcode $::DB
} {SQLITE_IOERR+11}

# Check the integrity of the cache.
#
integrity_check tkt2409-4.3

do_test tkt2409-4.4 {
  catchsql { ROLLBACK }
} {1 {cannot rollback - no transaction is active}}



unread_lock_db
db2 close
unset -nocomplain t1
finish_test

#
# This file implements tests to verify that ticket #2409 has been
# fixed. More specifically, they verify that if SQLite cannot
# obtain an EXCLUSIVE lock while trying to spill the cache during
# any statement other than a COMMIT, an I/O error is returned instead
# of SQLITE_BUSY.
#
# $Id: tkt2409.test,v 1.4 2008/08/20 14:49:25 danielk1977 Exp $

# Test Outline:
#
#   tkt-2409-1.*: Cause a cache-spill during an INSERT that is within
#       a db transaction but does not start a statement transaction.
#       Verify that the transaction is automatically rolled back
#       and SQLITE_IOERR_BLOCKED is returned
#
#       UPDATE: As of the pcache modifications, failing to upgrade to
#       an exclusive lock when attempting a cache-spill is no longer an
#       error. The pcache module allocates more space and keeps working
#       in memory if this occurs.
#
#   tkt-2409-2.*: Cause a cache-spill while updating the change-counter
#       during a database COMMIT. Verify that the transaction is not
#       rolled back and SQLITE_BUSY is returned.
#
#   tkt-2409-3.*: Similar to 2409-1.*, but using many INSERT statements
#       within a transaction instead of just one.
#
#       UPDATE: Again, pcache now just keeps working in main memory.
#
#   tkt-2409-4.*: Similar to 2409-1.*, but rig it so that the
#       INSERT statement starts a statement transaction. Verify that
#       SQLITE_BUSY is returned and the transaction is not rolled back.
#
#       UPDATE: This time, SQLITE_BUSY is not returned. pcache just uses
#       more malloc()'d memory.
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl

ifcapable !pager_pragmas {
  finish_test
................................................................................
#
proc unread_lock_db {} {
  if {$::STMT ne ""} {
    sqlite3_finalize $::STMT
    set ::STMT ""
  }
}

pcache_global_max 10

# Open the db handle used by [read_lock_db].
#
sqlite3 db2 test.db
set ::STMT ""

do_test tkt2409-1.1 {
................................................................................
  read_lock_db
  set ::zShort [string repeat 0123456789 1]
  set ::zLong  [string repeat 0123456789 1500]
  catchsql {
    BEGIN;
    INSERT INTO t1 VALUES($::zShort, $::zLong);
  }
} {0 {}}

do_test tkt2409-1.2 {
  sqlite3_errcode $::DB
} {SQLITE_OK}

# Check the integrity of the cache.
#
integrity_check tkt2409-1.3

# Check that the transaction was rolled back. Because the INSERT
# statement in which the "I/O error" occured did not open a statement
# transaction, SQLite had no choice but to roll back the transaction.
#
do_test tkt2409-1.4 {
  unread_lock_db
  catchsql { ROLLBACK }
} {0 {}}


set ::zShort [string repeat 0123456789 1]
set ::zLong  [string repeat 0123456789 1500]
set ::rc 1
for {set iCache 10} {$::rc} {incr iCache} {
  execsql "PRAGMA cache_size = $iCache"
  do_test tkt2409-2.1.$iCache {
................................................................................

do_test tkt2409-2.3 {
  unread_lock_db
  catchsql {
    COMMIT;
  }
} {0 {}}


do_test tkt2409-3.1 {
  db close
  set ::DB [sqlite3 db test.db; sqlite3_connection_pointer db]
  sqlite3_extended_result_codes $::DB 1
  execsql {
    PRAGMA cache_size=10;
................................................................................
  read_lock_db
  set ::zShort [string repeat 0123456789 1]
  set ::zLong  [string repeat 0123456789 1500]
  catchsql {
    BEGIN;
    INSERT INTO t1 SELECT $::zShort, $::zLong;
  }
} {0 {}}

do_test tkt2409-3.2 {
  sqlite3_errcode $::DB
} {SQLITE_OK}

# Check the integrity of the cache.
#
integrity_check tkt2409-3.3

# Check that the transaction was rolled back. Because the INSERT
# statement in which the "I/O error" occured did not open a statement
................................................................................
    set t1($r) 1
    append sql "INSERT INTO t1 VALUES('some-text-$r');"
  }

  read_lock_db
  execsql BEGIN
  catchsql $sql
} {0 {}}

do_test tkt2409-4.2 {
  sqlite3_errcode $::DB
} {SQLITE_OK}

# Check the integrity of the cache.
#
integrity_check tkt2409-4.3

do_test tkt2409-4.4 {
  catchsql { ROLLBACK }
} {0 {}}

pcache_global_max 0

unread_lock_db
db2 close
unset -nocomplain t1
finish_test

/*
** This file contains a standalone program used to generate C code that
** implements a static hash table to store the definitions of built-in
** SQL functions in SQLite. 
*/

#include <stdio.h>
#include <string.h>
#include <assert.h>

/*
** The SQLite source file "func.c" is included below.
**
** By defining the 4 macros and typedef below before including "func.c",
** most of the code is excluded. What is left is an array of constant
** strings, aBuiltinFunc[], containing the names of SQLite's built-in 
** SQL functions. i.e.:
**
**   const char aBuiltinFunc[] = { "like", "glob", "min", "max" ... };
**
** The data from aBuiltinFunc[] is used by this program to create the
** static hash table.
*/
#define CREATE_BUILTIN_HASHTABLE 1
#define FUNCTION(zName,w,x,y,z)    #zName
#define AGGREGATE(zName,v,w,x,y,z) #zName
#define LIKEFUNC(zName,x,y,z)      #zName
#define FuncDef const char *

#include "func.c"

/* The number of buckets in the static hash table. */
#define HASHSIZE 127

typedef unsigned char u8;

/* An array to map all upper-case characters into their corresponding
** lower-case character. 
*/
static const u8 sqlite3UpperToLower[] = {
      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16, 17,
     18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,
     36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53,
     54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 97, 98, 99,100,101,102,103,
    104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,
    122, 91, 92, 93, 94, 95, 96, 97, 98, 99,100,101,102,103,104,105,106,107,
    108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,
    126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,
    144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,
    162,163,164,165,166,167,168,169,170,171,172,173,174,175,176,177,178,179,
    180,181,182,183,184,185,186,187,188,189,190,191,192,193,194,195,196,197,
    198,199,200,201,202,203,204,205,206,207,208,209,210,211,212,213,214,215,
    216,217,218,219,220,221,222,223,224,225,226,227,228,229,230,231,232,233,
    234,235,236,237,238,239,240,241,242,243,244,245,246,247,248,249,250,251,
    252,253,254,255
};
#define UpperToLower sqlite3UpperToLower

int sqlite3StrICmp(const char *zLeft, const char *zRight){
  register unsigned char *a, *b;
  a = (unsigned char *)zLeft;
  b = (unsigned char *)zRight;
  while( *a!=0 && UpperToLower[*a]==UpperToLower[*b]){ a++; b++; }
  return UpperToLower[*a] - UpperToLower[*b];
}

static int hashstring(const char *zName){
  int ii;
  unsigned int iKey = 0;
  for(ii=0; zName[ii]; ii++){
    iKey = (iKey<<3) + (u8)sqlite3UpperToLower[(u8)zName[ii]];
  }
  iKey = iKey%HASHSIZE;
  return iKey;
}

static void printarray(const char *zName, u8 *aArray, int nArray){
  int ii;
  printf("  static u8 %s[%d] = {", zName, nArray);
  for(ii=0; ii<nArray; ii++){
    if( (ii%16)==0 ){
      printf("\n    ");
    }
    printf("%d, ", aArray[ii]);
  }
  printf("\n  };\n");
}


int main(int argc, char **argv){
  int nFunc;              /* Number of entries in the aBuiltinFunc array */

  u8 anFunc[256];
  u8 aHash[HASHSIZE];
  u8 aNext[256];
  int ii;
  int iHead;

  nFunc = (sizeof(aBuiltinFunc)/sizeof(const char *));
  assert(nFunc<256);

  memset(aHash, (unsigned char)nFunc, sizeof(aHash));
  memset(aNext, (unsigned char)nFunc, sizeof(aNext));
  memset(anFunc, 0, sizeof(anFunc));

  iHead = -1;
  for(ii=0; ii<nFunc; ii++){
    int iHash;

    if( iHead>=0 && 0==sqlite3StrICmp(aBuiltinFunc[ii], aBuiltinFunc[iHead]) ){
      anFunc[iHead]++;
      continue;
    }else{
      /* The routine generated by this program assumes that if there are
      ** two or more entries in the aBuiltinFunc[] array with the same
      ** name (i.e. two versions of the "max" function), then they must
      ** be stored in adjacent slots. The following block detects the
      ** problem if this is not the case.
      */
      int jj;
      for(jj=0; jj<ii; jj++){
        if( 0==sqlite3StrICmp(aBuiltinFunc[ii], aBuiltinFunc[jj]) ){
          fprintf(stderr, "Error in func.c\n");
          return -1;
        }
      }

      iHead = ii;
      anFunc[iHead] = 1;
    }

    iHash = hashstring(aBuiltinFunc[ii]);
    if( aHash[iHash]!=nFunc ){
      int iNext = aHash[iHash];
      while( aNext[iNext]!=nFunc ){
        iNext = aNext[iNext];
      }
      aNext[iNext] = ii;
    }else{
      aHash[iHash] = ii;
    }
  }

  printf(
  "int sqlite3GetBuiltinFunction(\n"
  "  const char *zName,   \n"
  "  int nName, \n"
  "  FuncDef **paFunc\n"
  "){\n"
  );

  printarray("aHash", aHash, HASHSIZE);
  printarray("anFunc", anFunc, nFunc);
  printarray("aNext", aNext, nFunc);
  printf("  FuncDef *pNoFunc = &aBuiltinFunc[%d];\n", nFunc);

  printf(
  "  unsigned int iKey = 0;  /* Hash of case-insensitive string zName. */\n"
  "  int ii;\n"
  "  FuncDef *pFunc;\n"
  "\n"
  "  /* Generate the hash of zName */\n"
  "  for(ii=0; ii<nName; ii++){\n"
  "    iKey = (iKey<<3) + (u8)sqlite3UpperToLower[(u8)zName[ii]];\n"
  "  }\n"
  "  iKey = iKey%%127;\n"
  "\n"
  "  pFunc = &aBuiltinFunc[iKey = aHash[iKey]];\n"
  "  while( pFunc!=pNoFunc && sqlite3StrNICmp(pFunc->zName, zName, nName) ){\n"
  "    pFunc = &aBuiltinFunc[iKey = aNext[iKey]];\n"
  "  }\n"
  "\n"
  "  *paFunc = pFunc;\n"
  "  return anFunc[iKey];\n"
  "}\n"
  );

  return 0;
}

   mutex.h
   opcodes.h
   os_common.h
   os.h
   os_os2.h
   pager.h
   parse.h

   rtree.h
   sqlite3ext.h
   sqlite3.h
   sqliteInt.h
   sqliteLimit.h
   vdbe.h
   vdbeInt.h
................................................................................
   opcodes.c

   os_os2.c
   os_unix.c
   os_win.c

   bitvec.c

   pager.c

   btmutex.c
   btree.c

   vdbefifo.c
   vdbemem.c
................................................................................
   alter.c
   analyze.c
   attach.c
   auth.c
   build.c
   callback.c
   delete.c
   func.c
   insert.c
   legacy.c
   loadext.c
   pragma.c
   prepare.c
   select.c
   table.c

   mutex.h
   opcodes.h
   os_common.h
   os.h
   os_os2.h
   pager.h
   parse.h
   pcache.h
   rtree.h
   sqlite3ext.h
   sqlite3.h
   sqliteInt.h
   sqliteLimit.h
   vdbe.h
   vdbeInt.h
................................................................................
   opcodes.c

   os_os2.c
   os_unix.c
   os_win.c

   bitvec.c
   pcache.c
   pager.c

   btmutex.c
   btree.c

   vdbefifo.c
   vdbemem.c
................................................................................
   alter.c
   analyze.c
   attach.c
   auth.c
   build.c
   callback.c
   delete.c
   func2.c
   insert.c
   legacy.c
   loadext.c
   pragma.c
   prepare.c
   select.c
   table.c