sqlite3_int64 *piLimit,        /* IN/OUT: The current limit */
     sqlite3_int64 iSize,           /* Total size of all files in the group */
     void *pArg                     /* Client data */
  );
  void *pArg;                    /* Third argument to the xCallback() */
  void (*xDestroy)(void*);       /* Optional destructor for pArg */
  quotaGroup *pNext, **ppPrev;   /* Doubly linked list of all quota objects */
  quotaFile *pFile;              /* Files within this group */
};

/*
** An instance of this structure represents a single file that is part
** of a quota group.  A single file can be opened multiple times.  In
** order keep multiple openings of the same file from causing the size
** of the file to count against the quota multiple times, each file
** has a unique instance of this object and multiple open connections
** to the same file each point to a single instance of this object.
*/
struct quotaFile {
  char *zFilename;                /* Name of this file */
  quotaGroup *pGroup;             /* Upper bound on file size */
  sqlite3_int64 iSize;            /* Current size of this file */
  int nRef;                       /* Number of times this file is open */
  quotaFile *pNext, **ppPrev;     /* Linked list of files in the same group */
};

/*
** An instance of the following object represents each open connection
................................................................................
static void quotaEnter(void){ sqlite3_mutex_enter(gQuota.pMutex); }
static void quotaLeave(void){ sqlite3_mutex_leave(gQuota.pMutex); }


/* If the reference count and threshold for a quotaGroup are both
** zero, then destroy the quotaGroup.
*/
static void quotaGroupDeref(quotaGroup *p){
  if( p->pFile==0 && p->iLimit==0 ){
    if( p->pNext ) p->pNext->ppPrev = p->ppPrev;
    if( p->ppPrev ) *p->ppPrev = p->pNext;
    if( p->xDestroy ) p->xDestroy(p->pArg);
    sqlite3_free(p);
  }
}

/*
** Return TRUE if string z matches glob pattern zGlob.
**
** Globbing rules:
................................................................................
  }else{
    /* If we get to this point, it means the file needs to be quota tracked.
    */
    pQuotaOpen = (quotaConn*)pConn;
    pSubOpen = quotaSubOpen(pConn);
    rc = pOrigVfs->xOpen(pOrigVfs, zName, pSubOpen, flags, pOutFlags);
    if( rc==SQLITE_OK ){
      for(pFile=pGroup->pFile; pFile && strcmp(pFile->zFilename, zName);
          pFile=pFile->pNext){}
      if( pFile==0 ){
        int nName = strlen(zName);
        pFile = sqlite3_malloc( sizeof(*pFile) + nName + 1 );
        if( pFile==0 ){
          quotaLeave();
          pSubOpen->pMethods->xClose(pSubOpen);
          return SQLITE_NOMEM;
        }
        memset(pFile, 0, sizeof(*pFile));
        pFile->zFilename = (char*)&pFile[1];
        memcpy(pFile->zFilename, zName, nName+1);
        pFile->pNext = pGroup->pFile;
        if( pGroup->pFile ) pGroup->pFile->ppPrev = &pFile->pNext;
        pFile->ppPrev = &pGroup->pFile;
        pGroup->pFile = pFile;
        pFile->pGroup = pGroup;
      }
      pFile->nRef++;
      pQuotaOpen->pFile = pFile;
      if( pSubOpen->pMethods->iVersion==1 ){
        pQuotaOpen->base.pMethods = &gQuota.sIoMethodsV1;
      }else{
................................................................................
** All SQLite database connections must be closed before calling this
** routine.
**
** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly one while
** shutting down in order to free all remaining quota groups.
*/
int sqlite3_quota_shutdown(void){
  quotaGroup *p;
  if( gQuota.isInitialized==0 ) return SQLITE_MISUSE;
  for(p=gQuota.pGroup; p; p=p->pNext){
    if( p->pFile ) return SQLITE_MISUSE;
  }
  while( gQuota.pGroup ){
    quotaGroup *p = gQuota.pGroup;
    gQuota.pGroup = p->pNext;
    sqlite3_free(p);
  }
  gQuota.isInitialized = 0;
  sqlite3_mutex_free(gQuota.pMutex);
  sqlite3_vfs_unregister(&gQuota.sThisVfs);
  memset(&gQuota, 0, sizeof(gQuota));
  return SQLITE_OK;
}
................................................................................
    pGroupTerm = Tcl_NewObj();
    Tcl_ListObjAppendElement(interp, pGroupTerm,
          Tcl_NewStringObj(pGroup->zPattern, -1));
    Tcl_ListObjAppendElement(interp, pGroupTerm,
          Tcl_NewWideIntObj(pGroup->iLimit));
    Tcl_ListObjAppendElement(interp, pGroupTerm,
          Tcl_NewWideIntObj(pGroup->iSize));
    for(pFile=pGroup->pFile; pFile; pFile=pFile->pNext){
      pFileTerm = Tcl_NewObj();
      Tcl_ListObjAppendElement(interp, pFileTerm,
            Tcl_NewStringObj(pFile->zFilename, -1));
      Tcl_ListObjAppendElement(interp, pFileTerm,
            Tcl_NewWideIntObj(pFile->iSize));
      Tcl_ListObjAppendElement(interp, pFileTerm,
            Tcl_NewWideIntObj(pFile->nRef));

     sqlite3_int64 *piLimit,        /* IN/OUT: The current limit */
     sqlite3_int64 iSize,           /* Total size of all files in the group */
     void *pArg                     /* Client data */
  );
  void *pArg;                    /* Third argument to the xCallback() */
  void (*xDestroy)(void*);       /* Optional destructor for pArg */
  quotaGroup *pNext, **ppPrev;   /* Doubly linked list of all quota objects */
  quotaFile *pFiles;             /* Files within this group */
};

/*
** An instance of this structure represents a single file that is part
** of a quota group.  A single file can be opened multiple times.  In
** order keep multiple openings of the same file from causing the size
** of the file to count against the quota multiple times, each file
** has a unique instance of this object and multiple open connections
** to the same file each point to a single instance of this object.
*/
struct quotaFile {
  char *zFilename;                /* Name of this file */
  quotaGroup *pGroup;             /* Quota group to which this file belongs */
  sqlite3_int64 iSize;            /* Current size of this file */
  int nRef;                       /* Number of times this file is open */
  quotaFile *pNext, **ppPrev;     /* Linked list of files in the same group */
};

/*
** An instance of the following object represents each open connection
................................................................................
static void quotaEnter(void){ sqlite3_mutex_enter(gQuota.pMutex); }
static void quotaLeave(void){ sqlite3_mutex_leave(gQuota.pMutex); }


/* If the reference count and threshold for a quotaGroup are both
** zero, then destroy the quotaGroup.
*/
static void quotaGroupDeref(quotaGroup *pGroup){
  if( pGroup->pFiles==0 && pGroup->iLimit==0 ){
    if( pGroup->pNext ) pGroup->pNext->ppPrev = pGroup->ppPrev;
    if( pGroup->ppPrev ) *pGroup->ppPrev = pGroup->pNext;
    if( pGroup->xDestroy ) pGroup->xDestroy(pGroup->pArg);
    sqlite3_free(pGroup);
  }
}

/*
** Return TRUE if string z matches glob pattern zGlob.
**
** Globbing rules:
................................................................................
  }else{
    /* If we get to this point, it means the file needs to be quota tracked.
    */
    pQuotaOpen = (quotaConn*)pConn;
    pSubOpen = quotaSubOpen(pConn);
    rc = pOrigVfs->xOpen(pOrigVfs, zName, pSubOpen, flags, pOutFlags);
    if( rc==SQLITE_OK ){
      for(pFile=pGroup->pFiles; pFile && strcmp(pFile->zFilename, zName);
          pFile=pFile->pNext){}
      if( pFile==0 ){
        int nName = strlen(zName);
        pFile = sqlite3_malloc( sizeof(*pFile) + nName + 1 );
        if( pFile==0 ){
          quotaLeave();
          pSubOpen->pMethods->xClose(pSubOpen);
          return SQLITE_NOMEM;
        }
        memset(pFile, 0, sizeof(*pFile));
        pFile->zFilename = (char*)&pFile[1];
        memcpy(pFile->zFilename, zName, nName+1);
        pFile->pNext = pGroup->pFiles;
        if( pGroup->pFiles ) pGroup->pFiles->ppPrev = &pFile->pNext;
        pFile->ppPrev = &pGroup->pFiles;
        pGroup->pFiles = pFile;
        pFile->pGroup = pGroup;
      }
      pFile->nRef++;
      pQuotaOpen->pFile = pFile;
      if( pSubOpen->pMethods->iVersion==1 ){
        pQuotaOpen->base.pMethods = &gQuota.sIoMethodsV1;
      }else{
................................................................................
** All SQLite database connections must be closed before calling this
** routine.
**
** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly one while
** shutting down in order to free all remaining quota groups.
*/
int sqlite3_quota_shutdown(void){
  quotaGroup *pGroup;
  if( gQuota.isInitialized==0 ) return SQLITE_MISUSE;
  for(pGroup=gQuota.pGroup; pGroup; pGroup=pGroup->pNext){
    if( pGroup->pFiles ) return SQLITE_MISUSE;
  }
  while( gQuota.pGroup ){
    pGroup = gQuota.pGroup;
    gQuota.pGroup = pGroup->pNext;
    sqlite3_free(pGroup);
  }
  gQuota.isInitialized = 0;
  sqlite3_mutex_free(gQuota.pMutex);
  sqlite3_vfs_unregister(&gQuota.sThisVfs);
  memset(&gQuota, 0, sizeof(gQuota));
  return SQLITE_OK;
}
................................................................................
    pGroupTerm = Tcl_NewObj();
    Tcl_ListObjAppendElement(interp, pGroupTerm,
          Tcl_NewStringObj(pGroup->zPattern, -1));
    Tcl_ListObjAppendElement(interp, pGroupTerm,
          Tcl_NewWideIntObj(pGroup->iLimit));
    Tcl_ListObjAppendElement(interp, pGroupTerm,
          Tcl_NewWideIntObj(pGroup->iSize));
    for(pFile=pGroup->pFiles; pFile; pFile=pFile->pNext){
      pFileTerm = Tcl_NewObj();
      Tcl_ListObjAppendElement(interp, pFileTerm,
            Tcl_NewStringObj(pFile->zFilename, -1));
      Tcl_ListObjAppendElement(interp, pFileTerm,
            Tcl_NewWideIntObj(pFile->iSize));
      Tcl_ListObjAppendElement(interp, pFileTerm,
            Tcl_NewWideIntObj(pFile->nRef));