if( pBase==0 ){
          pPg = *ppPage = 0;
          rc = SQLITE_NOMEM;
          goto pager_acquire_err;
        }
      }
      pPg = *ppPage = sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pBase);
      if( pPg==0 ) rc = SQLITE_NOMEM;
    }
  }

  if( rc!=SQLITE_OK ){
    /* Either the call to sqlite3PcacheFetch() returned an error or the
    ** pager was already in the error-state when this function was called.
    ** Set pPg to 0 and jump to the exception handler.  */
................................................................................
** to make up the difference. If the number of savepoints is already
** equal to nSavepoint, then this function is a no-op.
**
** If a memory allocation fails, SQLITE_NOMEM is returned. If an error 
** occurs while opening the sub-journal file, then an IO error code is
** returned. Otherwise, SQLITE_OK.
*/
int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){
  int rc = SQLITE_OK;                       /* Return code */
  int nCurrent = pPager->nSavepoint;        /* Current number of savepoints */



  assert( pPager->eState>=PAGER_WRITER_LOCKED );
  assert( assert_pager_state(pPager) );

  if( nSavepoint>nCurrent && pPager->useJournal ){
    int ii;                                 /* Iterator variable */
    PagerSavepoint *aNew;                   /* New Pager.aSavepoint array */

    /* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM
    ** if the allocation fails. Otherwise, zero the new portion in case a 
    ** malloc failure occurs while populating it in the for(...) loop below.
    */
    aNew = (PagerSavepoint *)sqlite3Realloc(
        pPager->aSavepoint, sizeof(PagerSavepoint)*nSavepoint
    );
    if( !aNew ){
      return SQLITE_NOMEM;
    }
    memset(&aNew[nCurrent], 0, (nSavepoint-nCurrent) * sizeof(PagerSavepoint));
    pPager->aSavepoint = aNew;

    /* Populate the PagerSavepoint structures just allocated. */
    for(ii=nCurrent; ii<nSavepoint; ii++){
      aNew[ii].nOrig = pPager->dbSize;
      if( isOpen(pPager->jfd) && pPager->journalOff>0 ){
        aNew[ii].iOffset = pPager->journalOff;
      }else{
        aNew[ii].iOffset = JOURNAL_HDR_SZ(pPager);
      }
      aNew[ii].iSubRec = pPager->nSubRec;
      aNew[ii].pInSavepoint = sqlite3BitvecCreate(pPager->dbSize);
      if( !aNew[ii].pInSavepoint ){
        return SQLITE_NOMEM;
      }
      if( pagerUseWal(pPager) ){
        sqlite3WalSavepoint(pPager->pWal, aNew[ii].aWalData);
      }
      pPager->nSavepoint = ii+1;
    }
    assert( pPager->nSavepoint==nSavepoint );
    assertTruncateConstraint(pPager);

  }







  return rc;
}



/*
** This function is called to rollback or release (commit) a savepoint.
** The savepoint to release or rollback need not be the most recently 
** created savepoint.
**
** Parameter op is always either SAVEPOINT_ROLLBACK or SAVEPOINT_RELEASE.

        if( pBase==0 ){
          pPg = *ppPage = 0;
          rc = SQLITE_NOMEM;
          goto pager_acquire_err;
        }
      }
      pPg = *ppPage = sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pBase);
      assert( pPg!=0 );
    }
  }

  if( rc!=SQLITE_OK ){
    /* Either the call to sqlite3PcacheFetch() returned an error or the
    ** pager was already in the error-state when this function was called.
    ** Set pPg to 0 and jump to the exception handler.  */
................................................................................
** to make up the difference. If the number of savepoints is already
** equal to nSavepoint, then this function is a no-op.
**
** If a memory allocation fails, SQLITE_NOMEM is returned. If an error 
** occurs while opening the sub-journal file, then an IO error code is
** returned. Otherwise, SQLITE_OK.
*/
static SQLITE_NOINLINE int pagerOpenSavepoint(Pager *pPager, int nSavepoint){
  int rc = SQLITE_OK;                       /* Return code */
  int nCurrent = pPager->nSavepoint;        /* Current number of savepoints */
  int ii;                                   /* Iterator variable */
  PagerSavepoint *aNew;                     /* New Pager.aSavepoint array */

  assert( pPager->eState>=PAGER_WRITER_LOCKED );
  assert( assert_pager_state(pPager) );

  assert( nSavepoint>nCurrent && pPager->useJournal );



  /* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM
  ** if the allocation fails. Otherwise, zero the new portion in case a 
  ** malloc failure occurs while populating it in the for(...) loop below.
  */
  aNew = (PagerSavepoint *)sqlite3Realloc(
      pPager->aSavepoint, sizeof(PagerSavepoint)*nSavepoint
  );
  if( !aNew ){
    return SQLITE_NOMEM;
  }
  memset(&aNew[nCurrent], 0, (nSavepoint-nCurrent) * sizeof(PagerSavepoint));
  pPager->aSavepoint = aNew;

  /* Populate the PagerSavepoint structures just allocated. */
  for(ii=nCurrent; ii<nSavepoint; ii++){
    aNew[ii].nOrig = pPager->dbSize;
    if( isOpen(pPager->jfd) && pPager->journalOff>0 ){
      aNew[ii].iOffset = pPager->journalOff;
    }else{
      aNew[ii].iOffset = JOURNAL_HDR_SZ(pPager);
    }
    aNew[ii].iSubRec = pPager->nSubRec;
    aNew[ii].pInSavepoint = sqlite3BitvecCreate(pPager->dbSize);
    if( !aNew[ii].pInSavepoint ){
      return SQLITE_NOMEM;
    }
    if( pagerUseWal(pPager) ){
      sqlite3WalSavepoint(pPager->pWal, aNew[ii].aWalData);
    }
    pPager->nSavepoint = ii+1;
  }
  assert( pPager->nSavepoint==nSavepoint );
  assertTruncateConstraint(pPager);
  return rc;
}
int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){
  assert( pPager->eState>=PAGER_WRITER_LOCKED );
  assert( assert_pager_state(pPager) );

  if( nSavepoint>pPager->nSavepoint && pPager->useJournal ){
    return pagerOpenSavepoint(pPager, nSavepoint);
  }else{
    return SQLITE_OK;
  }
}


/*
** This function is called to rollback or release (commit) a savepoint.
** The savepoint to release or rollback need not be the most recently 
** created savepoint.
**
** Parameter op is always either SAVEPOINT_ROLLBACK or SAVEPOINT_RELEASE.