*/
static int posixFchown(int fd, uid_t uid, gid_t gid){
  return geteuid() ? 0 : fchown(fd,uid,gid);
}

/* Forward reference */
static int openDirectory(const char*, int*);
static int unixGetpagesize(void);

/*
** Many system calls are accessed through pointer-to-functions so that
** they may be overridden at runtime to facilitate fault injection during
** testing and sandboxing.  The following array holds the names and pointers
** to all overrideable system calls.
*/

#if HAVE_MREMAP
  { "mremap",       (sqlite3_syscall_ptr)mremap,          0 },
#else
  { "mremap",       (sqlite3_syscall_ptr)0,               0 },
#endif
#define osMremap ((void*(*)(void*,size_t,size_t,int,...))aSyscall[23].pCurrent)
#endif

  { "getpagesize",  (sqlite3_syscall_ptr)unixGetpagesize, 0 },
#define osGetpagesize ((int(*)(void))aSyscall[24].pCurrent)

}; /* End of the overrideable system calls */

/*
** This is the xSetSystemCall() method of sqlite3_vfs for all of the
** "unix" VFSes.  Return SQLITE_OK opon successfully updating the
** system call pointer, or SQLITE_NOTFOUND if there is no configurable

           pShmNode->sharedMask, pShmNode->exclMask));
  }
#endif

  return rc;        
}

/*
** Return the system page size.
**
** This function should not be called directly by other code in this file. 
** Instead, it should be called via macro osGetpagesize().
*/
static int unixGetpagesize(void){
#if defined(_BSD_SOURCE)
  return getpagesize();
#else
  return (int)sysconf(_SC_PAGESIZE);
#endif
}

/*
** Return the minimum number of 32KB shm regions that should be mapped at
** a time, assuming that each mapping must be an integer multiple of the
** current system page-size.
**
** Usually, this is 1. The exception seems to be systems that are configured
** to use 64KB pages - in this case each mapping must cover at least two
** shm regions.
*/
static int unixShmRegionPerMap(void){
  int shmsz = 32*1024;            /* SHM region size */
  int pgsz = osGetpagesize();   /* System page size */
  assert( ((pgsz-1)&pgsz)==0 );   /* Page size must be a power of 2 */
  if( pgsz<shmsz ) return 1;
  return pgsz/shmsz;
}

/*
** Purge the unixShmNodeList list of all entries with unixShmNode.nRef==0.
**
** This is not a VFS shared-memory method; it is a utility function called
** by VFS shared-memory methods.
*/
static void unixShmPurge(unixFile *pFd){
  unixShmNode *p = pFd->pInode->pShmNode;
  assert( unixMutexHeld() );
  if( p && p->nRef==0 ){
    int nShmPerMap = unixShmRegionPerMap();
    int i;
    assert( p->pInode==pFd->pInode );
    sqlite3_mutex_free(p->mutex);
    for(i=0; i<p->nRegion; i+=nShmPerMap){
      if( p->h>=0 ){
        osMunmap(p->apRegion[i], p->szRegion);
      }else{
        sqlite3_free(p->apRegion[i]);
      }
    }
    sqlite3_free(p->apRegion);

  int bExtend,                    /* True to extend file if necessary */
  void volatile **pp              /* OUT: Mapped memory */
){
  unixFile *pDbFd = (unixFile*)fd;
  unixShm *p;
  unixShmNode *pShmNode;
  int rc = SQLITE_OK;
  int nShmPerMap = unixShmRegionPerMap();
  int nReqRegion;

  /* If the shared-memory file has not yet been opened, open it now. */
  if( pDbFd->pShm==0 ){
    rc = unixOpenSharedMemory(pDbFd);
    if( rc!=SQLITE_OK ) return rc;
  }

  p = pDbFd->pShm;
  pShmNode = p->pShmNode;
  sqlite3_mutex_enter(pShmNode->mutex);
  assert( szRegion==pShmNode->szRegion || pShmNode->nRegion==0 );
  assert( pShmNode->pInode==pDbFd->pInode );
  assert( pShmNode->h>=0 || pDbFd->pInode->bProcessLock==1 );
  assert( pShmNode->h<0 || pDbFd->pInode->bProcessLock==0 );

  /* Minimum number of regions required to be mapped. */
  nReqRegion = ((iRegion+nShmPerMap) / nShmPerMap) * nShmPerMap;

  if( pShmNode->nRegion<nReqRegion ){
    char **apNew;                      /* New apRegion[] array */
    int nByte = nReqRegion*szRegion;   /* Minimum required file size */
    struct stat sStat;                 /* Used by fstat() */

    pShmNode->szRegion = szRegion;

    if( pShmNode->h>=0 ){
      /* The requested region is not mapped into this processes address space.
      ** Check to see if it has been allocated (i.e. if the wal-index file is

          }
        }
      }
    }

    /* Map the requested memory region into this processes address space. */
    apNew = (char **)sqlite3_realloc(
        pShmNode->apRegion, nReqRegion*sizeof(char *)
    );
    if( !apNew ){
      rc = SQLITE_IOERR_NOMEM;
      goto shmpage_out;
    }
    pShmNode->apRegion = apNew;
    while( pShmNode->nRegion<nReqRegion ){
      int nMap = szRegion*nShmPerMap;
      int i;
      void *pMem;
      if( pShmNode->h>=0 ){
        pMem = osMmap(0, nMap,
            pShmNode->isReadonly ? PROT_READ : PROT_READ|PROT_WRITE, 
            MAP_SHARED, pShmNode->h, szRegion*(i64)pShmNode->nRegion
        );
        if( pMem==MAP_FAILED ){
          rc = unixLogError(SQLITE_IOERR_SHMMAP, "mmap", pShmNode->zFilename);
          goto shmpage_out;
        }
      }else{
        pMem = sqlite3_malloc(szRegion);
        if( pMem==0 ){
          rc = SQLITE_NOMEM;
          goto shmpage_out;
        }
        memset(pMem, 0, szRegion);
      }

      for(i=0; i<nShmPerMap; i++){
        pShmNode->apRegion[pShmNode->nRegion+i] = &((char*)pMem)[szRegion*i];
      }
      pShmNode->nRegion += nShmPerMap;
    }
  }

shmpage_out:
  if( pShmNode->nRegion>iRegion ){
    *pp = pShmNode->apRegion[iRegion];
  }else{

    osMunmap(pFd->pMapRegion, pFd->mmapSizeActual);
    pFd->pMapRegion = 0;
    pFd->mmapSize = 0;
    pFd->mmapSizeActual = 0;
  }
}














/*
** Attempt to set the size of the memory mapping maintained by file 
** descriptor pFd to nNew bytes. Any existing mapping is discarded.
**
** If successful, this function sets the following variables:
**
**       unixFile.pMapRegion

  assert( nNew>0 );
  assert( pFd->mmapSizeActual>=pFd->mmapSize );
  assert( MAP_FAILED!=0 );

  if( (pFd->ctrlFlags & UNIXFILE_RDONLY)==0 ) flags |= PROT_WRITE;

  if( pOrig ){
#if HAVE_MREMAP
    i64 nReuse = pFd->mmapSize;
#else
    const int szSyspage = osGetpagesize();
    i64 nReuse = (pFd->mmapSize & ~(szSyspage-1));
#endif
    u8 *pReq = &pOrig[nReuse];

    /* Unmap any pages of the existing mapping that cannot be reused. */
    if( nReuse!=nOrig ){
      osMunmap(pReq, nOrig-nReuse);
    }

    UNIXVFS("unix-proxy",    proxyIoFinder ),
#endif
  };
  unsigned int i;          /* Loop counter */

  /* Double-check that the aSyscall[] array has been constructed
  ** correctly.  See ticket [bb3a86e890c8e96ab] */
  assert( ArraySize(aSyscall)==25 );

  /* Register all VFSes defined in the aVfs[] array */
  for(i=0; i<(sizeof(aVfs)/sizeof(sqlite3_vfs)); i++){
    sqlite3_vfs_register(&aVfs[i], i==0);
  }
  return SQLITE_OK; 
}

**
**   test_syscall exists SYSTEM-CALL
**     Return true if the named system call exists. Or false otherwise.
**
**   test_syscall list
**     Return a list of all system calls. The list is constructed using
**     the xNextSystemCall() VFS method.
**
**   test_syscall pagesize PGSZ
**     If PGSZ is a power of two greater than 256, install a wrapper around
**     OS function getpagesize() that reports the system page size as PGSZ.
**     Or, if PGSZ is less than zero, remove any wrapper already installed.
*/

#include "sqliteInt.h"
#include "sqlite3.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>

#include <sys/types.h>
#include <errno.h>

static struct TestSyscallGlobal {
  int bPersist;                   /* 1 for persistent errors, 0 for transient */
  int nCount;                     /* Fail after this many more calls */
  int nFail;                      /* Number of failures that have occurred */
  int pgsz;
  sqlite3_syscall_ptr orig_getpagesize;
} gSyscall = { 0, 0, 0, 0, 0 };

static int ts_open(const char *, int, int);
static int ts_close(int fd);
static int ts_access(const char *zPath, int mode);
static char *ts_getcwd(char *zPath, size_t nPath);
static int ts_stat(const char *zPath, struct stat *p);
static int ts_fstat(int fd, struct stat *p);

    return TCL_ERROR;
  }

  pVfs = sqlite3_vfs_find(0);
  Tcl_SetObjResult(interp, Tcl_NewStringObj(pVfs->zName, -1));
  return TCL_OK;
}

static int ts_getpagesize(void){
  return gSyscall.pgsz;
}

static int test_syscall_pagesize(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
  sqlite3_vfs *pVfs = sqlite3_vfs_find(0);
  int pgsz;
  if( objc!=3 ){
    Tcl_WrongNumArgs(interp, 2, objv, "PGSZ");
    return TCL_ERROR;
  }
  if( Tcl_GetIntFromObj(interp, objv[2], &pgsz) ){
    return TCL_ERROR;
  }

  if( pgsz<0 ){
    if( gSyscall.orig_getpagesize ){
      pVfs->xSetSystemCall(pVfs, "getpagesize", gSyscall.orig_getpagesize);
    }
  }else{
    if( pgsz<512 || (pgsz & (pgsz-1)) ){
      Tcl_AppendResult(interp, "pgsz out of range", 0);
      return TCL_ERROR;
    }
    gSyscall.orig_getpagesize = pVfs->xGetSystemCall(pVfs, "getpagesize");
    gSyscall.pgsz = pgsz;
    pVfs->xSetSystemCall(
        pVfs, "getpagesize", (sqlite3_syscall_ptr)ts_getpagesize
    );
  }

  return TCL_OK;
}

static int test_syscall(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
  struct SyscallCmd {
    const char *zName;
    Tcl_ObjCmdProc *xCmd;
  } aCmd[] = {
    { "fault",      test_syscall_fault },
    { "install",    test_syscall_install },
    { "uninstall",  test_syscall_uninstall },
    { "reset",      test_syscall_reset },
    { "errno",      test_syscall_errno },
    { "exists",     test_syscall_exists },
    { "list",       test_syscall_list },
    { "defaultvfs", test_syscall_defaultvfs },
    { "pagesize",   test_syscall_pagesize },
    { 0, 0 }
  };
  int iCmd;
  int rc;

  if( objc<2 ){
    Tcl_WrongNumArgs(interp, 1, objv, "SUB-COMMAND ...");

# Tests for the xNextSystemCall method.
#
foreach s {
    open close access getcwd stat fstat ftruncate
    fcntl read pread write pwrite fchmod fallocate
    pread64 pwrite64 unlink openDirectory mkdir rmdir 
    statvfs fchown umask mmap munmap mremap
    getpagesize
} {
  if {[test_syscall exists $s]} {lappend syscall_list $s}
}
do_test 3.1 { lsort [test_syscall list] } [lsort $syscall_list]

#-------------------------------------------------------------------------
# This test verifies that if a call to open() fails and errno is set to

# 2010 April 13
#
# 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 regression tests for SQLite library.  The
# focus of this file is testing the operation of the library in
# "PRAGMA journal_mode=WAL" mode.
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl
set testprefix wal64k

ifcapable !wal {finish_test ; return }

db close
test_syscall pagesize 65536
sqlite3 db test.db

do_execsql_test 1.0 { 
  PRAGMA journal_mode = WAL;
  CREATE TABLE t1(x);
  CREATE INDEX i1 ON t1(x);
} {wal}
do_test 1.1 { file size test.db-shm } {65536}

do_test 1.2 {
  execsql BEGIN
  while {[file size test.db-shm]==65536} {
    execsql { INSERT INTO t1 VALUES( randstr(900,1100) ) }
  }
  execsql COMMIT
  file size test.db-shm
} {131072}

integrity_check 1.3

db close
test_syscall pagesize -1
finish_test