SQLite

*/
static int multiplexStrlen30(const char *z){
  const char *z2 = z;
  if( z==0 ) return 0;
  while( *z2 ){ z2++; }
  return 0x3fffffff & (int)(z2 - z);
}

/*
** Generate the file-name for chunk iChunk of the group with base name
** zBase. The file-name is written to buffer zOut before returning. Buffer
** zOut must be allocated by the caller so that it is at least (nBase+4)
** bytes in size, where nBase is the length of zBase, not including the
** nul-terminator.
*/
static void multiplexFilename(
  const char *zBase,              /* Filename for chunk 0 */
  int nBase,                      /* Size of zBase in bytes (without \0) */
  int flags,                      /* Flags used to open file */
  int iChunk,                     /* Chunk to generate filename for */
  char *zOut                      /* Buffer to write generated name to */
){
  memcpy(zOut, zBase, nBase+1);
  if( iChunk!=0 && iChunk!=SQLITE_MULTIPLEX_JOURNAL_8_3_OFFSET ){
    int n = nBase;
#ifdef SQLITE_ENABLE_8_3_NAMES
    int i;
    for(i=n-1; i>0 && i>=n-4 && zOut[i]!='.'; i--){}
    if( i>=n-4 ) n = i+1;
    if( flags & SQLITE_OPEN_MAIN_JOURNAL ){
      /* The extensions on overflow files for main databases are 001, 002,
       ** 003 and so forth.  To avoid name collisions, add 400 to the 
       ** extensions of journal files so that they are 401, 402, 403, ....
       */
      iChunk += SQLITE_MULTIPLEX_JOURNAL_8_3_OFFSET;
    }
#endif
    sqlite3_snprintf(4,&zOut[n],"%03d",iChunk);
  }
}

/* Compute the filename for the iChunk-th chunk
*/
static int multiplexSubFilename(multiplexGroup *pGroup, int iChunk){
  if( iChunk>=pGroup->nReal ){
    struct multiplexReal *p;
    p = sqlite3_realloc(pGroup->aReal, (iChunk+1)*sizeof(*p));

  if( pGroup->zName && pGroup->aReal[iChunk].z==0 ){
    char *z;
    int n = pGroup->nName;
    pGroup->aReal[iChunk].z = z = sqlite3_malloc( n+4 );
    if( z==0 ){
      return SQLITE_NOMEM;
    }
    multiplexFilename(pGroup->zName, pGroup->nName, pGroup->flags, iChunk, z);















  }
  return SQLITE_OK;
}

/* Translate an sqlite3_file* that is really a multiplexGroup* into
** the sqlite3_file* for the underlying original VFS.
*/

      assert( pSubOpen || rc!=SQLITE_OK );
    }
    if( rc==SQLITE_OK ){
      sqlite3_int64 sz;

      rc = pSubOpen->pMethods->xFileSize(pSubOpen, &sz);
      if( rc==SQLITE_OK && zName ){
        int bExists;
        if( sz==0 ){
          if( flags & SQLITE_OPEN_MAIN_JOURNAL ){
            /* If opening a main journal file and the first chunk is zero
            ** bytes in size, delete any subsequent chunks from the 
            ** file-system. */
            int iChunk = 1;
            do {
              rc = pOrigVfs->xAccess(pOrigVfs, 
                  pGroup->aReal[iChunk].z, SQLITE_ACCESS_EXISTS, &bExists
              );
              if( rc==SQLITE_OK && bExists ){
                rc = pOrigVfs->xDelete(pOrigVfs, pGroup->aReal[iChunk].z, 0);
                if( rc==SQLITE_OK ){
                  rc = multiplexSubFilename(pGroup, ++iChunk);
                }
              }
            }while( rc==SQLITE_OK && bExists );
          }
        }else{
          /* If the first overflow file exists and if the size of the main file
           ** is different from the chunk size, that means the chunk size is set
           ** set incorrectly.  So fix it.
           **
           ** Or, if the first overflow file does not exist and the main file is
           ** larger than the chunk size, that means the chunk size is too small.
           ** But we have no way of determining the intended chunk size, so 
           ** just disable the multiplexor all togethre.
           */
          rc = pOrigVfs->xAccess(pOrigVfs, pGroup->aReal[1].z,
              SQLITE_ACCESS_EXISTS, &bExists);
          if( rc==SQLITE_OK && bExists && sz==(sz&0xffff0000) && sz>0
              && sz!=pGroup->szChunk ){
            pGroup->szChunk = sz;
          }else if( rc==SQLITE_OK && !bExists && sz>pGroup->szChunk ){
            pGroup->bEnabled = 0;
          }
        }
      }
    }

    if( rc==SQLITE_OK ){
      if( pSubOpen->pMethods->iVersion==1 ){
        pMultiplexOpen->base.pMethods = &gMultiplex.sIoMethodsV1;

** It attempts to delete the filename specified.
*/
static int multiplexDelete(
  sqlite3_vfs *pVfs,         /* The multiplex VFS */
  const char *zName,         /* Name of file to delete */
  int syncDir
){
  int rc;
  sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
  rc = pOrigVfs->xDelete(pOrigVfs, zName, syncDir);
  if( rc==SQLITE_OK ){
    /* If the main chunk was deleted successfully, also delete any subsequent
    ** chunks - starting with the last (highest numbered). 
    */
    int nName = strlen(zName);
    char *z;
    z = sqlite3_malloc(nName + 4);
    if( z==0 ){
      rc = SQLITE_IOERR_NOMEM;
    }else{
      int iChunk = 0;
      int bExists;
      do{
        multiplexFilename(zName, nName, SQLITE_OPEN_MAIN_JOURNAL, ++iChunk, z);
        rc = pOrigVfs->xAccess(pOrigVfs, z, SQLITE_ACCESS_EXISTS, &bExists);
      }while( rc==SQLITE_OK && bExists );
      while( rc==SQLITE_OK && iChunk>1 ){
        multiplexFilename(zName, nName, SQLITE_OPEN_MAIN_JOURNAL, --iChunk, z);
        rc = pOrigVfs->xDelete(pOrigVfs, z, syncDir);
      }
    }
    sqlite3_free(z);
  }
  return rc;
}

static int multiplexAccess(sqlite3_vfs *a, const char *b, int c, int *d){
  return gMultiplex.pOrigVfs->xAccess(gMultiplex.pOrigVfs, b, c, d);
}
static int multiplexFullPathname(sqlite3_vfs *a, const char *b, int c, char *d){
  return gMultiplex.pOrigVfs->xFullPathname(gMultiplex.pOrigVfs, b, c, d);