SQLite

*/
int deduceDatabaseType(const char *zName, int dfltZip){
  FILE *f = fopen(zName, "rb");
  size_t n;
  int rc = SHELL_OPEN_UNSPEC;
  char zBuf[100];
  if( f==0 ){
    if( dfltZip && sqlite3_strlike("%.zip",zName,0)==0 ){
       return SHELL_OPEN_ZIPFILE;
    }else{
       return SHELL_OPEN_NORMAL;
    }
  }
  fseek(f, -25, SEEK_END);
  n = fread(zBuf, 25, 1, f);
  if( n==1 && memcmp(zBuf, "Start-Of-SQLite3-", 17)==0 ){
    rc = SHELL_OPEN_APPENDVFS;
  }else{
    fseek(f, -22, SEEK_END);
    n = fread(zBuf, 22, 1, f);
    if( n==1 && zBuf[0]==0x50 && zBuf[1]==0x4b && zBuf[2]==0x05
       && zBuf[3]==0x06 ){
      rc = SHELL_OPEN_ZIPFILE;
    }else if( n==0 && dfltZip && sqlite3_strlike("%.zip",zName,0)==0 ){
      rc = SHELL_OPEN_ZIPFILE;
    }
  }
  fclose(f);
  return rc;  
}

/* Flags for open_db().
**
** The default behavior of open_db() is to exit(1) if the database fails to
** open.  The OPEN_DB_KEEPALIVE flag changes that so that it prints an error
** but still returns without calling exit.
**
** The OPEN_DB_ZIPFILE flag causes open_db() to prefer to open files as a
** ZIP archive if the file does not exist or is empty and its name matches
** the *.zip pattern.
*/
#define OPEN_DB_KEEPALIVE   0x001   /* Return after error if true */
#define OPEN_DB_ZIPFILE     0x002   /* Open as ZIP if name matches *.zip */

/*
** Make sure the database is open.  If it is not, then open it.  If
** the database fails to open, print an error message and exit.
*/
static void open_db(ShellState *p, int openFlags){
  if( p->db==0 ){
    if( p->openMode==SHELL_OPEN_UNSPEC ){
      if( p->zDbFilename==0 || p->zDbFilename[0]==0 ){
        p->openMode = SHELL_OPEN_NORMAL;
      }else{
        p->openMode = (u8)deduceDatabaseType(p->zDbFilename, 
                             (openFlags & OPEN_DB_ZIPFILE)!=0);
      }
    }
    switch( p->openMode ){
      case SHELL_OPEN_APPENDVFS: {
        sqlite3_open_v2(p->zDbFilename, &p->db, 
           SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE, "apndvfs");
        break;

        break;
      }
    }
    globalDb = p->db;
    if( p->db==0 || SQLITE_OK!=sqlite3_errcode(p->db) ){
      utf8_printf(stderr,"Error: unable to open database \"%s\": %s\n",
          p->zDbFilename, sqlite3_errmsg(p->db));
      if( openFlags & OPEN_DB_KEEPALIVE ) return;
      exit(1);
    }
#ifndef SQLITE_OMIT_LOAD_EXTENSION
    sqlite3_enable_load_extension(p->db, 1);
#endif
    sqlite3_fileio_init(p->db, 0, 0);
    sqlite3_shathree_init(p->db, 0, 0);

      }
    }
    /* If a filename is specified, try to open it first */
    zNewFilename = nArg>iName ? sqlite3_mprintf("%s", azArg[iName]) : 0;
    if( zNewFilename ){
      if( newFlag ) shellDeleteFile(zNewFilename);
      p->zDbFilename = zNewFilename;
      open_db(p, OPEN_DB_KEEPALIVE);
      if( p->db==0 ){
        utf8_printf(stderr, "Error: cannot open '%s'\n", zNewFilename);
        sqlite3_free(zNewFilename);
      }else{
        p->zFreeOnClose = zNewFilename;
      }
    }

#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_HAVE_ZLIB)
    }else if( strncmp(z, "-A", 2)==0 ){
      if( nCmd>0 ){
        utf8_printf(stderr, "Error: cannot mix regular SQL or dot-commands"
                            " with \"%s\"\n", z);
        return 1;
      }
      open_db(&data, OPEN_DB_ZIPFILE);
      if( z[2] ){
        argv[i] = &z[2];
        arDotCommand(&data, 1, argv+(i-1), argc-(i-1));
      }else{
        arDotCommand(&data, 1, argv+i, argc-i);
      }
      readStdin = 0;