SQLite

  if( p->zState ){
    rbuMPrintfExec(p, p->dbRbu, "ATTACH %Q AS stat", p->zState);
    memcpy(p->zStateDb, "stat", 4);
  }else{
    memcpy(p->zStateDb, "main", 4);
  }

#if 0
  if( p->rc==SQLITE_OK && rbuIsVacuum(p) ){
    p->rc = sqlite3_exec(p->dbRbu, "BEGIN", 0, 0, 0);
  }
#endif

  /* If it has not already been created, create the rbu_state table */
  rbuMPrintfExec(p, p->dbRbu, RBU_CREATE_STATE, p->zStateDb);

#if 0
  if( rbuIsVacuum(p) ){
    if( p->rc==SQLITE_OK ){
      int rc2;
      int bOk = 0;
      sqlite3_stmt *pCnt = 0;
      p->rc = prepareAndCollectError(p->dbRbu, &pCnt, &p->zErrmsg,
          "SELECT count(*) FROM stat.sqlite_master"
      );
      if( p->rc==SQLITE_OK 
       && sqlite3_step(pCnt)==SQLITE_ROW
       && 1==sqlite3_column_int(pCnt, 0)
      ){
        bOk = 1;
      }
      rc2 = sqlite3_finalize(pCnt);
      if( p->rc==SQLITE_OK ) p->rc = rc2;

      if( p->rc==SQLITE_OK && bOk==0 ){
        p->rc = SQLITE_ERROR;
        p->zErrmsg = sqlite3_mprintf("invalid state database");
      }
    
      if( p->rc==SQLITE_OK ){
        p->rc = sqlite3_exec(p->dbRbu, "COMMIT", 0, 0, 0);
      }
    }
  }
#endif

  if( p->rc==SQLITE_OK && rbuIsVacuum(p) ){
    int bOpen = 0;
    int rc;
    p->nRbu = 0;
    p->pRbuFd = 0;
    rc = sqlite3_file_control(p->dbRbu, "main", SQLITE_FCNTL_RBUCNT, (void*)p);
    if( rc!=SQLITE_NOTFOUND ) p->rc = rc;

sqlite3rbu *sqlite3rbu_open(
  const char *zTarget, 
  const char *zRbu,
  const char *zState
);

/*
** Open an RBU handle to perform an RBU vacuum on database file zTarget.
** An RBU vacuum is similar to SQLite's built-in VACUUM command, except
** that it can be suspended and resumed like an RBU update.
**
** The second argument to this function, which may not be NULL, identifies 
** a database in which to store the state of the RBU vacuum operation if
** it is suspended. The first time sqlite3rbu_vacuum() is called, to start
** an RBU vacuum operation, the state database should either not exist or
** be empty (contain no tables). If an RBU vacuum is suspended by calling
** sqlite3rbu_close() on the RBU handle before sqlite3rbu_step() has
** returned SQLITE_DONE, the vacuum state is stored in the state database. 
** The vacuum can be resumed by calling this function to open a new RBU
** handle specifying the same target and state databases.
**
** This function does not delete the state database after an RBU vacuum
** is completed, even if it created it.
**
** As with sqlite3rbu_open(), Zipvfs users should rever to the comment
** describing the sqlite3rbu_create_vfs() API function below for 
** a description of the complications associated with using RBU with 
** zipvfs databases.
*/
sqlite3rbu *sqlite3rbu_vacuum(
  const char *zTarget, 
  const char *zState
);

/*