testcase( surplus==maxLocal );
  testcase( surplus==maxLocal+1 );
  if( surplus <= maxLocal ){
    pInfo->nLocal = (u16)surplus;
  }else{
    pInfo->nLocal = (u16)minLocal;
  }
  pInfo->iOverflow = (u16)(&pInfo->pPayload[pInfo->nLocal] - pCell);
  pInfo->nSize = pInfo->iOverflow + 4;
}

/*
** The following routines are implementations of the MemPage.xParseCell()
** method.
**
** Parse a cell content block and fill in the CellInfo structure.

  assert( pPage->childPtrSize==4 );
#ifndef SQLITE_DEBUG
  UNUSED_PARAMETER(pPage);
#endif
  pInfo->nSize = 4 + getVarint(&pCell[4], (u64*)&pInfo->nKey);
  pInfo->nPayload = 0;
  pInfo->nLocal = 0;
  pInfo->iOverflow = 0;
  pInfo->pPayload = 0;
  return;
}
static void btreeParseCellPtr(
  MemPage *pPage,         /* Page containing the cell */
  u8 *pCell,              /* Pointer to the cell text. */
  CellInfo *pInfo         /* Fill in this structure */

  if( nPayload<=pPage->maxLocal ){
    /* This is the (easy) common case where the entire payload fits
    ** on the local page.  No overflow is required.
    */
    pInfo->nSize = nPayload + (u16)(pIter - pCell);
    if( pInfo->nSize<4 ) pInfo->nSize = 4;
    pInfo->nLocal = (u16)nPayload;
    pInfo->iOverflow = 0;
  }else{
    btreeParseCellAdjustSizeForOverflow(pPage, pCell, pInfo);
  }
}
static void btreeParseCellPtrIndex(
  MemPage *pPage,         /* Page containing the cell */
  u8 *pCell,              /* Pointer to the cell text. */

  if( nPayload<=pPage->maxLocal ){
    /* This is the (easy) common case where the entire payload fits
    ** on the local page.  No overflow is required.
    */
    pInfo->nSize = nPayload + (u16)(pIter - pCell);
    if( pInfo->nSize<4 ) pInfo->nSize = 4;
    pInfo->nLocal = (u16)nPayload;
    pInfo->iOverflow = 0;
  }else{
    btreeParseCellAdjustSizeForOverflow(pPage, pCell, pInfo);
  }
}
static void btreeParseCell(
  MemPage *pPage,         /* Page containing the cell */
  int iCell,              /* The cell index.  First cell is 0 */

** for the overflow page.
*/
static void ptrmapPutOvflPtr(MemPage *pPage, u8 *pCell, int *pRC){
  CellInfo info;
  if( *pRC ) return;
  assert( pCell!=0 );
  pPage->xParseCell(pPage, pCell, &info);
  if( info.iOverflow ){
    Pgno ovfl = get4byte(&pCell[info.iOverflow]);
    ptrmapPut(pPage->pBt, ovfl, PTRMAP_OVERFLOW1, pPage->pgno, pRC);
  }
}
#endif


/*

    nCell = pPage->nCell;

    for(i=0; i<nCell; i++){
      u8 *pCell = findCell(pPage, i);
      if( eType==PTRMAP_OVERFLOW1 ){
        CellInfo info;
        pPage->xParseCell(pPage, pCell, &info);
        if( info.iOverflow
         && pCell+info.iOverflow+3<=pPage->aData+pPage->maskPage
         && iFrom==get4byte(&pCell[info.iOverflow])
        ){
          put4byte(&pCell[info.iOverflow], iTo);
          break;
        }
      }else{
        if( get4byte(pCell)==iFrom ){
          put4byte(pCell, iTo);
          break;
        }

  int rc;
  int nOvfl;
  u32 ovflPageSize;

  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  pPage->xParseCell(pPage, pCell, &info);
  *pnSize = info.nSize;
  if( info.iOverflow==0 ){
    return SQLITE_OK;  /* No overflow pages. Return without doing anything */
  }
  if( pCell+info.iOverflow+3 > pPage->aData+pPage->maskPage ){
    return SQLITE_CORRUPT_BKPT;  /* Cell extends past end of page */
  }
  ovflPgno = get4byte(&pCell[info.iOverflow]);
  assert( pBt->usableSize > 4 );
  ovflPageSize = pBt->usableSize - 4;
  nOvfl = (info.nPayload - info.nLocal + ovflPageSize - 1)/ovflPageSize;
  assert( nOvfl>0 || 
    (CORRUPT_DB && (info.nPayload + ovflPageSize)<ovflPageSize)
  );
  while( nOvfl-- ){

  {
    CellInfo info;
    pPage->xParseCell(pPage, pCell, &info);
    assert( nHeader=(int)(info.pPayload - pCell) );
    assert( info.nKey==nKey );
    assert( *pnSize == info.nSize );
    assert( spaceLeft == info.nLocal );
    assert( pPrior == &pCell[info.iOverflow] );
  }
#endif

  /* Write the payload into the local Cell and any extra into overflow pages */
  while( nPayload>0 ){
    if( spaceLeft==0 ){
#ifndef SQLITE_OMIT_AUTOVACUUM

    for(j=0; j<pPage->nCell; j++){
      CellInfo info;
      u8 *z;
     
      z = findCell(pPage, j);
      pPage->xParseCell(pPage, z, &info);
      if( info.iOverflow ){
        Pgno ovfl = get4byte(&z[info.iOverflow]);
        ptrmapGet(pBt, ovfl, &e, &n);
        assert( n==pPage->pgno && e==PTRMAP_OVERFLOW1 );
      }
      if( !pPage->leaf ){
        Pgno child = get4byte(z);
        ptrmapGet(pBt, child, &e, &n);
        assert( n==pPage->pgno && e==PTRMAP_BTREE );

      maxKey = info.nKey;
    }

    /* Check the content overflow list */
    if( info.nPayload>info.nLocal ){
      int nPage;       /* Number of pages on the overflow chain */
      Pgno pgnoOvfl;   /* First page of the overflow chain */
      assert( pc + info.iOverflow <= usableSize );
      nPage = (info.nPayload - info.nLocal + usableSize - 5)/(usableSize - 4);
      pgnoOvfl = get4byte(&pCell[info.iOverflow]);
#ifndef SQLITE_OMIT_AUTOVACUUM
      if( pBt->autoVacuum ){
        checkPtrmap(pCheck, pgnoOvfl, PTRMAP_OVERFLOW1, iPage);
      }
#endif
      checkList(pCheck, 0, pgnoOvfl, nPage);
    }

** based on information extract from the raw disk page.
*/
struct CellInfo {
  i64 nKey;      /* The key for INTKEY tables, or nPayload otherwise */
  u8 *pPayload;  /* Pointer to the start of payload */
  u32 nPayload;  /* Bytes of payload */
  u16 nLocal;    /* Amount of payload held locally, not on overflow */
  u16 iOverflow; /* Offset to overflow page number.  Zero if no overflow */
  u16 nSize;     /* Size of the cell content on the main b-tree page */
};

/*
** Maximum depth of an SQLite B-Tree structure. Any B-Tree deeper than
** this will be declared corrupt. This value is calculated based on a
** maximum database size of 2^31 pages a minimum fanout of 2 for a