SQLite

** makeup a single SQLite DB file.  This allows the size of the DB
** to exceed the limits imposed by the file system.
**
** There is an instance of the following object for each defined multiplex
** group.
*/
struct multiplexGroup {



  sqlite3_file **pReal;            /* Handles to each chunk */
  char *bOpen;                     /* array of bools - 0 if chunk not opened */
  char *zName;                     /* Base filename of this group */
  int nName;                       /* Length of base filename */
  int flags;                       /* Flags used for original opening */
  int nChunkSize;                  /* Chunk size used for this group */
  int nMaxChunks;                  /* Max number of chunks for this group */
  int bEnabled;                    /* TRUE to use Multiplex VFS for this file */
  multiplexGroup *pNext, *pPrev;   /* Doubly linked list of all group objects */
};

/*
** An instance of the following object represents each open connection
** to a file that is multiplex'ed.  This object is a 

  ** shim, the following mutex must be held.
  */
  sqlite3_mutex *pMutex;

  /* List of multiplexGroup objects.
  */
  multiplexGroup *pGroups;

  /* Storage for temp file names.  Allocated during 
  ** initialization to the max pathname of the underlying VFS.
  */
  char *zName;

} gMultiplex;

/************************* Utility Routines *********************************/
/*
** Acquire and release the mutex used to serialize access to the
** list of multiplexGroups.
*/

        rc = SQLITE_ERROR;
      }
    }
  }

  return rc;
}




































/* Translate an sqlite3_file* that is really a multiplexGroup* into
** the sqlite3_file* for the underlying original VFS.
*/
static sqlite3_file *multiplexSubOpen(
  multiplexConn *pConn,
  int iChunk,
  int *rc,
  int *pOutFlags
){
  multiplexGroup *pGroup = pConn->pGroup;
  sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;        /* Real VFS */
  if( iChunk<pGroup->nMaxChunks ){
    sqlite3_file *pSubOpen = pGroup->pReal[iChunk];   /* Real file descriptor */
    if( !pGroup->bOpen[iChunk] ){
      memcpy(gMultiplex.zName, pGroup->zName, pGroup->nName+1);
      if( iChunk ){
#ifdef SQLITE_MULTIPLEX_EXT_OVWR
        sqlite3_snprintf(SQLITE_MULTIPLEX_EXT_SZ+1,
             gMultiplex.zName+pGroup->nName-SQLITE_MULTIPLEX_EXT_SZ,
             SQLITE_MULTIPLEX_EXT_FMT, iChunk);
#else
        sqlite3_snprintf(SQLITE_MULTIPLEX_EXT_SZ+1,
             gMultiplex.zName+pGroup->nName,
             SQLITE_MULTIPLEX_EXT_FMT, iChunk);
#endif
      }

      *rc = pOrigVfs->xOpen(pOrigVfs, gMultiplex.zName, pSubOpen,
                            pGroup->flags, pOutFlags);
      if( *rc==SQLITE_OK ){

        pGroup->bOpen[iChunk] = -1;
        return pSubOpen;
      }
      return NULL;
    }
    *rc = SQLITE_OK;
    return pSubOpen;
  }
  *rc = SQLITE_FULL;
  return NULL;
}

/*
** This is the implementation of the multiplex_control() SQL function.
*/
static void multiplexControlFunc(
  sqlite3_context *context,

  const sqlite3_api_routines *pApi
){
  int rc;
  rc = sqlite3_create_function(db, "multiplex_control", 2, SQLITE_ANY, 
      0, multiplexControlFunc, 0, 0);
  return rc;
}































/************************* VFS Method Wrappers *****************************/

/*
** This is the xOpen method used for the "multiplex" VFS.
**
** Most of the work is done by the underlying original VFS.  This method

){
  int rc = SQLITE_OK;                  /* Result code */
  multiplexConn *pMultiplexOpen;       /* The new multiplex file descriptor */
  multiplexGroup *pGroup;              /* Corresponding multiplexGroup object */
  sqlite3_file *pSubOpen;                        /* Real file descriptor */
  sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
  int nName;
  int i;
  int sz;


  UNUSED_PARAMETER(pVfs);


  /* We need to create a group structure and manage
  ** access to this group of files.
  */
  multiplexEnter();
  pMultiplexOpen = (multiplexConn*)pConn;

  /* If the second argument to this function is NULL, generate a 
  ** temporary file name to use.  This will be handled by the
  ** original xOpen method.  We just need to allocate space for
  ** it.
  */
  if( !zName ){




    rc = multiplexGetTempname(pOrigVfs, pOrigVfs->mxPathname, gMultiplex.zName);
    zName = gMultiplex.zName;

  }

  if( rc==SQLITE_OK ){
    /* allocate space for group */
    nName = multiplexStrlen30(zName);
    sz = sizeof(multiplexGroup)                             /* multiplexGroup */
       + (sizeof(sqlite3_file *)*SQLITE_MULTIPLEX_MAX_CHUNKS)  /* pReal[] */
       + (pOrigVfs->szOsFile*SQLITE_MULTIPLEX_MAX_CHUNKS)      /* *pReal */
       + SQLITE_MULTIPLEX_MAX_CHUNKS                           /* bOpen[] */
       + nName + 1;                                            /* zName */
#ifndef SQLITE_MULTIPLEX_EXT_OVWR
    sz += SQLITE_MULTIPLEX_EXT_SZ;
    assert(nName+SQLITE_MULTIPLEX_EXT_SZ < pOrigVfs->mxPathname);
#else
    assert(nName >= SQLITE_MULTIPLEX_EXT_SZ);
    assert(nName < pOrigVfs->mxPathname);
#endif
    pGroup = sqlite3_malloc( sz );
    if( pGroup==0 ){
      rc=SQLITE_NOMEM;
    }
  }

  if( rc==SQLITE_OK ){
    const char *zChunkSize;
    /* assign pointers to extra space allocated */
    char *p = (char *)&pGroup[1];
    pMultiplexOpen->pGroup = pGroup;
    memset(pGroup, 0, sz);
    pGroup->bEnabled = -1;
    pGroup->nChunkSize = SQLITE_MULTIPLEX_CHUNK_SIZE;

    zChunkSize = sqlite3_uri_parameter(zName, "chunksize");
    if( zChunkSize ){
      int n = atoi(zChunkSize);
      if( n>0 ) pGroup->nChunkSize = (n+0xffff)&~0xffff;
    }
    pGroup->nMaxChunks = SQLITE_MULTIPLEX_MAX_CHUNKS;
    pGroup->pReal = (sqlite3_file **)p;
    p += (sizeof(sqlite3_file *)*pGroup->nMaxChunks);
    for(i=0; i<pGroup->nMaxChunks; i++){
      pGroup->pReal[i] = (sqlite3_file *)p;
      p += pOrigVfs->szOsFile;
    }
    /* bOpen[] vals should all be zero from memset above */
    pGroup->bOpen = p;
    p += pGroup->nMaxChunks;
    pGroup->zName = p;
    /* save off base filename, name length, and original open flags  */
    memcpy(pGroup->zName, zName, nName+1);
    pGroup->nName = nName;
    pGroup->flags = flags;
    pSubOpen = multiplexSubOpen(pMultiplexOpen, 0, &rc, pOutFlags);
    if( pSubOpen ){
      /* if this file is already larger than chunk size, disable 
      ** the multiplex feature.
      */
      sqlite3_int64 sz;
      int rc2 = pSubOpen->pMethods->xFileSize(pSubOpen, &sz);
      if( (rc2==SQLITE_OK) && (sz>pGroup->nChunkSize) ){
        pGroup->bEnabled = 0;
      }
      if( pSubOpen->pMethods->iVersion==1 ){
        pMultiplexOpen->base.pMethods = &gMultiplex.sIoMethodsV1;
      }else{
        pMultiplexOpen->base.pMethods = &gMultiplex.sIoMethodsV2;
      }
      /* place this group at the head of our list */
      pGroup->pNext = gMultiplex.pGroups;
      if( gMultiplex.pGroups ) gMultiplex.pGroups->pPrev = pGroup;
      gMultiplex.pGroups = pGroup;
    }else{

      sqlite3_free(pGroup);
    }
  }
  multiplexLeave();

  return rc;
}

/*
** This is the xDelete method used for the "multiplex" VFS.
** It attempts to delete the filename specified, as well
** as additional files with the SQLITE_MULTIPLEX_EXT_FMT extension.
*/
static int multiplexDelete(
  sqlite3_vfs *pVfs,         /* The multiplex VFS */
  const char *zName,         /* Name of file to delete */
  int syncDir
){
  sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
  int rc = SQLITE_OK;
  int nName = multiplexStrlen30(zName);
  int i;

  UNUSED_PARAMETER(pVfs);

  multiplexEnter();
  memcpy(gMultiplex.zName, zName, nName+1);
  for(i=0; i<SQLITE_MULTIPLEX_MAX_CHUNKS; i++){
    int rc2;
    int exists = 0;
    if( i ){
#ifdef SQLITE_MULTIPLEX_EXT_OVWR
        sqlite3_snprintf(SQLITE_MULTIPLEX_EXT_SZ+1, 
            gMultiplex.zName+nName-SQLITE_MULTIPLEX_EXT_SZ, 
            SQLITE_MULTIPLEX_EXT_FMT, i);
#else
        sqlite3_snprintf(SQLITE_MULTIPLEX_EXT_SZ+1, 
            gMultiplex.zName+nName, 
            SQLITE_MULTIPLEX_EXT_FMT, i);
#endif
    }
    rc2 = pOrigVfs->xAccess(pOrigVfs, gMultiplex.zName, 
        SQLITE_ACCESS_EXISTS, &exists);
    if( rc2==SQLITE_OK && exists ){
      /* if it exists, delete it */
      rc2 = pOrigVfs->xDelete(pOrigVfs, gMultiplex.zName, syncDir);
      if( rc2!=SQLITE_OK ) rc = rc2;
    }else{
      /* stop at first "gap" */
      break;
    }
  }
  multiplexLeave();
  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);

** The group structure for this file is unlinked from 
** our list of groups and freed.
*/
static int multiplexClose(sqlite3_file *pConn){
  multiplexConn *p = (multiplexConn*)pConn;
  multiplexGroup *pGroup = p->pGroup;
  int rc = SQLITE_OK;
  int i;
  multiplexEnter();
  /* close any open handles */
  for(i=0; i<pGroup->nMaxChunks; i++){
    if( pGroup->bOpen[i] ){
      sqlite3_file *pSubOpen = pGroup->pReal[i];
      int rc2 = pSubOpen->pMethods->xClose(pSubOpen);
      if( rc2!=SQLITE_OK ) rc = rc2;
      pGroup->bOpen[i] = 0;
    }
  }
  /* remove from linked list */
  if( pGroup->pNext ) pGroup->pNext->pPrev = pGroup->pPrev;
  if( pGroup->pPrev ){
    pGroup->pPrev->pNext = pGroup->pNext;
  }else{
    gMultiplex.pGroups = pGroup->pNext;
  }

  sqlite3_int64 iOfst
){
  multiplexConn *p = (multiplexConn*)pConn;
  multiplexGroup *pGroup = p->pGroup;
  int rc = SQLITE_OK;
  multiplexEnter();
  if( !pGroup->bEnabled ){
    sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
    if( !pSubOpen ){
      rc = SQLITE_IOERR_READ;
    }else{
      rc = pSubOpen->pMethods->xRead(pSubOpen, pBuf, iAmt, iOfst);
    }
  }else{
    while( iAmt > 0 ){
      int i = (int)(iOfst / pGroup->nChunkSize);
      sqlite3_file *pSubOpen = multiplexSubOpen(p, i, &rc, NULL);
      if( pSubOpen ){
        int extra = ((int)(iOfst % pGroup->nChunkSize) + iAmt) -
                                                        pGroup->nChunkSize;
        if( extra<0 ) extra = 0;
        iAmt -= extra;
        rc = pSubOpen->pMethods->xRead(pSubOpen, pBuf, iAmt,
                                       iOfst % pGroup->nChunkSize);

  sqlite3_int64 iOfst
){
  multiplexConn *p = (multiplexConn*)pConn;
  multiplexGroup *pGroup = p->pGroup;
  int rc = SQLITE_OK;
  multiplexEnter();
  if( !pGroup->bEnabled ){
    sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
    if( pSubOpen==0 ){
      rc = SQLITE_IOERR_WRITE;
    }else{
      rc = pSubOpen->pMethods->xWrite(pSubOpen, pBuf, iAmt, iOfst);
    }
  }else{
    while( iAmt > 0 ){
      int i = (int)(iOfst / pGroup->nChunkSize);
      sqlite3_file *pSubOpen = multiplexSubOpen(p, i, &rc, NULL);
      if( pSubOpen ){
        int extra = ((int)(iOfst % pGroup->nChunkSize) + iAmt) -
                    pGroup->nChunkSize;
        if( extra<0 ) extra = 0;
        iAmt -= extra;
        rc = pSubOpen->pMethods->xWrite(pSubOpen, pBuf, iAmt,
                                        iOfst % pGroup->nChunkSize);

*/
static int multiplexTruncate(sqlite3_file *pConn, sqlite3_int64 size){
  multiplexConn *p = (multiplexConn*)pConn;
  multiplexGroup *pGroup = p->pGroup;
  int rc = SQLITE_OK;
  multiplexEnter();
  if( !pGroup->bEnabled ){
    sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
    if( pSubOpen==0 ){
      rc = SQLITE_IOERR_TRUNCATE;
    }else{
      rc = pSubOpen->pMethods->xTruncate(pSubOpen, size);
    }
  }else{
    int rc2;
    int i;
    sqlite3_file *pSubOpen;
    sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
    memcpy(gMultiplex.zName, pGroup->zName, pGroup->nName+1);
    /* delete the chunks above the truncate limit */
    for(i=(int)(size / pGroup->nChunkSize)+1; i<pGroup->nMaxChunks; i++){
      /* close any open chunks before deleting them */
      if( pGroup->bOpen[i] ){
        pSubOpen = pGroup->pReal[i];
        rc2 = pSubOpen->pMethods->xClose(pSubOpen);
        if( rc2!=SQLITE_OK ) rc = SQLITE_IOERR_TRUNCATE;
        pGroup->bOpen[i] = 0;
      }
#ifdef SQLITE_MULTIPLEX_EXT_OVWR
      sqlite3_snprintf(SQLITE_MULTIPLEX_EXT_SZ+1, 
          gMultiplex.zName+pGroup->nName-SQLITE_MULTIPLEX_EXT_SZ, 
          SQLITE_MULTIPLEX_EXT_FMT, i);
#else
      sqlite3_snprintf(SQLITE_MULTIPLEX_EXT_SZ+1, 
          gMultiplex.zName+pGroup->nName, 
          SQLITE_MULTIPLEX_EXT_FMT, i);
#endif
      rc2 = pOrigVfs->xDelete(pOrigVfs, gMultiplex.zName, 0);
      if( rc2!=SQLITE_OK ) rc = SQLITE_IOERR_TRUNCATE;
    }
    pSubOpen = multiplexSubOpen(p, (int)(size/pGroup->nChunkSize), &rc2, NULL);
    if( pSubOpen ){
      rc2 = pSubOpen->pMethods->xTruncate(pSubOpen, size % pGroup->nChunkSize);
      if( rc2!=SQLITE_OK ) rc = rc2;
    }else{
      rc = SQLITE_IOERR_TRUNCATE;
    }
  }
  multiplexLeave();
  return rc;
}

/* Pass xSync requests through to the original VFS without change
*/
static int multiplexSync(sqlite3_file *pConn, int flags){
  multiplexConn *p = (multiplexConn*)pConn;
  multiplexGroup *pGroup = p->pGroup;
  int rc = SQLITE_OK;
  int i;
  multiplexEnter();
  for(i=0; i<pGroup->nMaxChunks; i++){
    /* if we don't have it open, we don't need to sync it */
    if( pGroup->bOpen[i] ){
      sqlite3_file *pSubOpen = pGroup->pReal[i];

      int rc2 = pSubOpen->pMethods->xSync(pSubOpen, flags);
      if( rc2!=SQLITE_OK ) rc = rc2;
    }
  }
  multiplexLeave();
  return rc;
}

/* Pass xFileSize requests through to the original VFS.
** Aggregate the size of all the chunks before returning.
*/
static int multiplexFileSize(sqlite3_file *pConn, sqlite3_int64 *pSize){
  multiplexConn *p = (multiplexConn*)pConn;
  multiplexGroup *pGroup = p->pGroup;
  int rc = SQLITE_OK;
  int rc2;
  int i;
  multiplexEnter();
  if( !pGroup->bEnabled ){
    sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
    if( pSubOpen==0 ){
      rc = SQLITE_IOERR_FSTAT;
    }else{
      rc = pSubOpen->pMethods->xFileSize(pSubOpen, pSize);
    }
  }else{
    *pSize = 0;
    for(i=0; i<pGroup->nMaxChunks; i++){
      sqlite3_file *pSubOpen = NULL;
      /* if not opened already, check to see if the chunk exists */
      if( pGroup->bOpen[i] ){
        pSubOpen = pGroup->pReal[i];
      }else{
        sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
        int exists = 0;
        memcpy(gMultiplex.zName, pGroup->zName, pGroup->nName+1);
        if( i ){
#ifdef SQLITE_MULTIPLEX_EXT_OVWR
          sqlite3_snprintf(SQLITE_MULTIPLEX_EXT_SZ+1, 
              gMultiplex.zName+pGroup->nName-SQLITE_MULTIPLEX_EXT_SZ, 
              SQLITE_MULTIPLEX_EXT_FMT, i);
#else
          sqlite3_snprintf(SQLITE_MULTIPLEX_EXT_SZ+1, 
              gMultiplex.zName+pGroup->nName, 
              SQLITE_MULTIPLEX_EXT_FMT, i);
#endif
        }
        rc2 = pOrigVfs->xAccess(pOrigVfs, gMultiplex.zName, 
            SQLITE_ACCESS_EXISTS, &exists);
        if( rc2==SQLITE_OK && exists){
          /* if it exists, open it */
          pSubOpen = multiplexSubOpen(p, i, &rc, NULL);
        }else{
          /* stop at first "gap" */
          break;
        }
      }
      if( pSubOpen ){
        sqlite3_int64 sz;
        rc2 = pSubOpen->pMethods->xFileSize(pSubOpen, &sz);
        if( rc2!=SQLITE_OK ){
          rc = rc2;
        }else{

}

/* Pass xLock requests through to the original VFS unchanged.
*/
static int multiplexLock(sqlite3_file *pConn, int lock){
  multiplexConn *p = (multiplexConn*)pConn;
  int rc;
  sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
  if( pSubOpen ){
    return pSubOpen->pMethods->xLock(pSubOpen, lock);
  }
  return SQLITE_BUSY;
}

/* Pass xUnlock requests through to the original VFS unchanged.
*/
static int multiplexUnlock(sqlite3_file *pConn, int lock){
  multiplexConn *p = (multiplexConn*)pConn;
  int rc;
  sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
  if( pSubOpen ){
    return pSubOpen->pMethods->xUnlock(pSubOpen, lock);
  }
  return SQLITE_IOERR_UNLOCK;
}

/* Pass xCheckReservedLock requests through to the original VFS unchanged.
*/
static int multiplexCheckReservedLock(sqlite3_file *pConn, int *pResOut){
  multiplexConn *p = (multiplexConn*)pConn;
  int rc;
  sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
  if( pSubOpen ){
    return pSubOpen->pMethods->xCheckReservedLock(pSubOpen, pResOut);
  }
  return SQLITE_IOERR_CHECKRESERVEDLOCK;
}

/* Pass xFileControl requests through to the original VFS unchanged,

          nChunkSize &= ~(MAX_PAGE_SIZE-1);
          pGroup->nChunkSize = nChunkSize;
          rc = SQLITE_OK;
        }
      }
      break;
    case MULTIPLEX_CTRL_SET_MAX_CHUNKS:
      if( pArg ) {
        int nMaxChunks = *(int *)pArg;
        if(( nMaxChunks<1 ) || ( nMaxChunks>SQLITE_MULTIPLEX_MAX_CHUNKS )){
          rc = SQLITE_MISUSE;
        }else{
          pGroup->nMaxChunks = nMaxChunks;
          rc = SQLITE_OK;
        }
      }
      break;
    case SQLITE_FCNTL_SIZE_HINT:
    case SQLITE_FCNTL_CHUNK_SIZE:
      /* no-op these */
      rc = SQLITE_OK;
      break;
    default:
      pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
      if( pSubOpen ){
        rc = pSubOpen->pMethods->xFileControl(pSubOpen, op, pArg);
      }
      break;
  }
  return rc;
}

/* Pass xSectorSize requests through to the original VFS unchanged.
*/
static int multiplexSectorSize(sqlite3_file *pConn){
  multiplexConn *p = (multiplexConn*)pConn;
  int rc;
  sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
  if( pSubOpen ){
    return pSubOpen->pMethods->xSectorSize(pSubOpen);
  }
  return DEFAULT_SECTOR_SIZE;
}

/* Pass xDeviceCharacteristics requests through to the original VFS unchanged.
*/
static int multiplexDeviceCharacteristics(sqlite3_file *pConn){
  multiplexConn *p = (multiplexConn*)pConn;
  int rc;
  sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
  if( pSubOpen ){
    return pSubOpen->pMethods->xDeviceCharacteristics(pSubOpen);
  }
  return 0;
}

/* Pass xShmMap requests through to the original VFS unchanged.
*/
static int multiplexShmMap(
  sqlite3_file *pConn,            /* Handle open on database file */
  int iRegion,                    /* Region to retrieve */
  int szRegion,                   /* Size of regions */
  int bExtend,                    /* True to extend file if necessary */
  void volatile **pp              /* OUT: Mapped memory */
){
  multiplexConn *p = (multiplexConn*)pConn;
  int rc;
  sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
  if( pSubOpen ){
    return pSubOpen->pMethods->xShmMap(pSubOpen, iRegion, szRegion, bExtend,pp);
  }
  return SQLITE_IOERR;
}

/* Pass xShmLock requests through to the original VFS unchanged.
*/
static int multiplexShmLock(
  sqlite3_file *pConn,       /* Database file holding the shared memory */
  int ofst,                  /* First lock to acquire or release */
  int n,                     /* Number of locks to acquire or release */
  int flags                  /* What to do with the lock */
){
  multiplexConn *p = (multiplexConn*)pConn;
  int rc;
  sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
  if( pSubOpen ){
    return pSubOpen->pMethods->xShmLock(pSubOpen, ofst, n, flags);
  }
  return SQLITE_BUSY;
}

/* Pass xShmBarrier requests through to the original VFS unchanged.
*/
static void multiplexShmBarrier(sqlite3_file *pConn){
  multiplexConn *p = (multiplexConn*)pConn;
  int rc;
  sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
  if( pSubOpen ){
    pSubOpen->pMethods->xShmBarrier(pSubOpen);
  }
}

/* Pass xShmUnmap requests through to the original VFS unchanged.
*/
static int multiplexShmUnmap(sqlite3_file *pConn, int deleteFlag){
  multiplexConn *p = (multiplexConn*)pConn;
  int rc;
  sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
  if( pSubOpen ){
    return pSubOpen->pMethods->xShmUnmap(pSubOpen, deleteFlag);
  }
  return SQLITE_OK;
}

/************************** Public Interfaces *****************************/

  pOrigVfs = sqlite3_vfs_find(zOrigVfsName);
  if( pOrigVfs==0 ) return SQLITE_ERROR;
  assert( pOrigVfs!=&gMultiplex.sThisVfs );
  gMultiplex.pMutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
  if( !gMultiplex.pMutex ){
    return SQLITE_NOMEM;
  }
  gMultiplex.zName = sqlite3_malloc(pOrigVfs->mxPathname);
  if( !gMultiplex.zName ){
    sqlite3_mutex_free(gMultiplex.pMutex);
    return SQLITE_NOMEM;
  }
  gMultiplex.pGroups = NULL;
  gMultiplex.isInitialized = 1;
  gMultiplex.pOrigVfs = pOrigVfs;
  gMultiplex.sThisVfs = *pOrigVfs;
  gMultiplex.sThisVfs.szOsFile += sizeof(multiplexConn);
  gMultiplex.sThisVfs.zName = SQLITE_MULTIPLEX_VFS_NAME;
  gMultiplex.sThisVfs.xOpen = multiplexOpen;

** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once while
** shutting down in order to free all remaining multiplex groups.
*/
int sqlite3_multiplex_shutdown(void){
  if( gMultiplex.isInitialized==0 ) return SQLITE_MISUSE;
  if( gMultiplex.pGroups ) return SQLITE_MISUSE;
  gMultiplex.isInitialized = 0;
  sqlite3_free(gMultiplex.zName);
  sqlite3_mutex_free(gMultiplex.pMutex);
  sqlite3_vfs_unregister(&gMultiplex.sThisVfs);
  memset(&gMultiplex, 0, sizeof(gMultiplex));
  return SQLITE_OK;
}

/***************************** Test Code ***********************************/

          Tcl_NewStringObj(pGroup->zName, -1));
    Tcl_ListObjAppendElement(interp, pGroupTerm,
          Tcl_NewIntObj(pGroup->nName));
    Tcl_ListObjAppendElement(interp, pGroupTerm,
          Tcl_NewIntObj(pGroup->flags));

    /* count number of chunks with open handles */
    for(i=0; i<pGroup->nMaxChunks; i++){
      if( pGroup->bOpen[i] ) nChunks++;
    }
    Tcl_ListObjAppendElement(interp, pGroupTerm,
          Tcl_NewIntObj(nChunks));

    Tcl_ListObjAppendElement(interp, pGroupTerm,
          Tcl_NewIntObj(pGroup->nChunkSize));
    Tcl_ListObjAppendElement(interp, pGroupTerm,
          Tcl_NewIntObj(pGroup->nMaxChunks));

    Tcl_ListObjAppendElement(interp, pResult, pGroupTerm);
  }
  multiplexLeave();
  Tcl_SetObjResult(interp, pResult);
  return TCL_OK;
}

  list $msg
}

# This attempts to delete the base file and 
# and files with the chunk extension.
proc multiplex_delete {name} {
  global g_max_chunks

  for {set i 0} {$i<$g_max_chunks} {incr i} {
    forcedelete [multiplex_name $name $i]
    forcedelete [multiplex_name $name-journal $i]
    forcedelete [multiplex_name $name-wal $i]
  }
}

do_test multiplex-1.7 { sqlite3_multiplex_initialize "" 1 }        {SQLITE_OK}
do_test multiplex-1.8 { sqlite3_multiplex_shutdown }               {SQLITE_OK}


do_test multiplex-1.9.1  { sqlite3_multiplex_initialize "" 1 }     {SQLITE_OK}
do_test multiplex-1.9.2  { sqlite3 db test.db }                    {}
do_test multiplex-1.9.3  { multiplex_set db main 32768 16 }        {SQLITE_OK}
do_test multiplex-1.9.4  { multiplex_set db main 32768 -1 }        {SQLITE_MISUSE}
do_test multiplex-1.9.5  { multiplex_set db main -1 16 }           {SQLITE_MISUSE}
do_test multiplex-1.9.6  { multiplex_set db main 31 16 }           {SQLITE_OK}
do_test multiplex-1.9.7  { multiplex_set db main 32768 100 }       {SQLITE_MISUSE}
do_test multiplex-1.9.8  { multiplex_set db main 1073741824 1 }    {SQLITE_OK}
do_test multiplex-1.9.9  { db close }                              {}
do_test multiplex-1.9.10 { sqlite3_multiplex_shutdown }            {SQLITE_OK}

do_test multiplex-1.10.1  { sqlite3_multiplex_initialize "" 1 }                                  {SQLITE_OK}
do_test multiplex-1.10.2  { sqlite3 db test.db }                                                 {}
do_test multiplex-1.10.3  { lindex [ catchsql { SELECT multiplex_control(2, 32768); } ] 0 }      {0}
do_test multiplex-1.10.4  { lindex [ catchsql { SELECT multiplex_control(3, -1); } ] 0 }         {1}
do_test multiplex-1.10.5  { lindex [ catchsql { SELECT multiplex_control(2, -1); } ] 0 }         {1}
do_test multiplex-1.10.6  { lindex [ catchsql { SELECT multiplex_control(2, 31); } ] 0 }         {0}
do_test multiplex-1.10.7  { lindex [ catchsql { SELECT multiplex_control(3, 100); } ] 0 }        {1}
do_test multiplex-1.10.8  { lindex [ catchsql { SELECT multiplex_control(2, 1073741824); } ] 0 } {0}
do_test multiplex-1.10.9  { db close }                                                           {}
do_test multiplex-1.10.10 { sqlite3_multiplex_shutdown }                                         {SQLITE_OK}

do_test multiplex-1.11.1  { sqlite3_multiplex_initialize "" 1 }               {SQLITE_OK}
do_test multiplex-1.11.2  { sqlite3 db test.db }                              {}
do_test multiplex-1.11.3  { sqlite3_multiplex_control db main enable 0  }     {SQLITE_OK}

#
#   multiplex-2.7.*: Disable/enable tests.
#

sqlite3_multiplex_initialize "" 1
multiplex_set db main 32768 16


do_test multiplex-2.1.2 {
  sqlite3 db test.db
  execsql {
    PRAGMA page_size=1024;
    PRAGMA auto_vacuum=OFF;
    PRAGMA journal_mode=DELETE;
  }
  execsql {
    CREATE TABLE t1(a, b);
    INSERT INTO t1 VALUES(1, randomblob(1100));
    INSERT INTO t1 VALUES(2, randomblob(1100));
  }
} {}
do_test multiplex-2.1.3 { file size [multiplex_name test.db 0] } {4096}
do_test multiplex-2.1.4 {
  execsql { INSERT INTO t1 VALUES(3, randomblob(1100)) }
} {}

do_test multiplex-2.2.1 {
  execsql { INSERT INTO t1 VALUES(3, randomblob(1100)) }
} {}
do_test multiplex-2.2.3 { file size [multiplex_name test.db 0] } {6144}

do_test multiplex-2.3.1 {
  sqlite3 db2 test2.db
  db2 close
} {}


do_test multiplex-2.4.1 {
  sqlite3_multiplex_shutdown
} {SQLITE_MISUSE}
do_test multiplex-2.4.2 {
  execsql { INSERT INTO t1 VALUES(3, randomblob(1100)) }
} {}
do_test multiplex-2.4.4 { file size [multiplex_name test.db 0] } {7168}
do_test multiplex-2.4.99 {
  db close
  sqlite3_multiplex_shutdown
} {SQLITE_OK}


do_test multiplex-2.5.1 {
  multiplex_delete test.db
  sqlite3_multiplex_initialize "" 1
  sqlite3 db test.db
  multiplex_set db main 4096 16
} {SQLITE_OK}

do_test multiplex-2.5.2 {
  execsql {
    PRAGMA page_size = 1024;
    PRAGMA journal_mode = delete;

  db eval {SELECT a,length(b) FROM t1 WHERE a=2}
} {2 4000}

do_test multiplex-2.5.8 {
  db eval {SELECT a,length(b) FROM t1 WHERE a=4}
} {4 4000}

do_test multiplex-2.5.9 { file size [multiplex_name test.db 0] } [list $g_chunk_size]
do_test multiplex-2.5.10 { file size [multiplex_name test.db 1] } [list $g_chunk_size]

do_test multiplex-2.5.99 {
  db close
  sqlite3_multiplex_shutdown
} {SQLITE_OK}

do_faultsim_test multiplex-5.5 -prep {
  catch { sqlite3_multiplex_shutdown }
} -body {
  sqlite3_multiplex_initialize "" 1
  multiplex_set db main 32768 16
}

# test that mismatch filesize is detected
#
# Do not run this test if $::G(perm:presql) is set. If it is set, then the
# expected IO error will occur within the Tcl [sqlite3] wrapper, not within
# the first SQL statement executed below. This breaks the test case.
#
if {0==[info exists ::G(perm:presql)] || $::G(perm:presql) == ""} {
  set all_journal_modes {delete persist truncate memory off}
  foreach jmode $all_journal_modes {
    do_test multiplex-5.6.1.$jmode {
      sqlite3_multiplex_shutdown
      multiplex_delete test.db
      sqlite3 db test.db
      db eval {
        PRAGMA page_size = 1024;
        PRAGMA auto_vacuum = off;
      }
      db eval "PRAGMA journal_mode = $jmode;"
    } $jmode
    do_test multiplex-5.6.2.$jmode {
      execsql {
        CREATE TABLE t1(a, b);
        INSERT INTO t1 VALUES(1, randomblob(15000));
        INSERT INTO t1 VALUES(2, randomblob(15000));
        INSERT INTO t1 VALUES(3, randomblob(15000));
        INSERT INTO t1 VALUES(4, randomblob(15000));
        INSERT INTO t1 VALUES(5, randomblob(15000));
      }
      db close
      sqlite3_multiplex_initialize "" 1
      sqlite3 db test.db
      multiplex_set db main 4096 16
    } {SQLITE_OK}
    do_test multiplex-5.6.3.$jmode {
      catchsql {
        INSERT INTO t1 VALUES(6, randomblob(15000));
      }
    } {1 {disk I/O error}}
    do_test multiplex-5.6.4.$jmode {
      db close
    } {}
  }
}

#-------------------------------------------------------------------------
# Test that you can vacuum a multiplex'ed DB.  

ifcapable vacuum {

sqlite3_multiplex_shutdown
do_test multiplex-6.0.0 {
  multiplex_delete test.db

  sqlite3_multiplex_initialize "" 1
  sqlite3 db test.db
  multiplex_set db main 4096 16
} {SQLITE_OK}

do_test multiplex-6.1.0 {
  execsql {
    PRAGMA page_size=1024;
    PRAGMA journal_mode=DELETE;
    PRAGMA auto_vacuum=OFF;
  }
  execsql {
    CREATE TABLE t1(a, b);
    INSERT INTO t1 VALUES(1, randomblob($g_chunk_size));
    INSERT INTO t1 VALUES(2, randomblob($g_chunk_size));
  }
} {}
do_test multiplex-6.2.1 { file size [multiplex_name test.db 0] } [list $g_chunk_size]
do_test multiplex-6.2.2 { file size [multiplex_name test.db 1] } [list $g_chunk_size]

do_test multiplex-6.3.0 {
  execsql { VACUUM }
} {}

do_test multiplex-6.99 {
  db close
  multiplex_delete test.db
  sqlite3_multiplex_shutdown
} {SQLITE_OK}

}


catch { sqlite3_multiplex_shutdown }
finish_test