assert( gap<=65536 );
  /* EVIDENCE-OF: R-29356-02391 If the database uses a 65536-byte page size
  ** and the reserved space is zero (the usual value for reserved space)
  ** then the cell content offset of an empty page wants to be 65536.
  ** However, that integer is too large to be stored in a 2-byte unsigned
  ** integer, so a value of 0 is used in its place. */
  top = get2byte(&data[hdr+5]);
  assert( top<=(int)pPage->pBt->usableSize ); /* Prevent by getAndInitPage() */
  if( gap>top ){
    if( top==0 && pPage->pBt->usableSize==65536 ){
      top = 65536;
    }else{
      return SQLITE_CORRUPT_PAGE(pPage);
    }
  }

  /* If there is enough space between gap and top for one more cell pointer,
................................................................................
  /* At this point, nFree contains the sum of the offset to the start
  ** of the cell-content area plus the number of free bytes within
  ** the cell-content area. If this is greater than the usable-size
  ** of the page, then the page must be corrupted. This check also
  ** serves to verify that the offset to the start of the cell-content
  ** area, according to the page header, lies within the page.
  */
  if( nFree>usableSize ){
    return SQLITE_CORRUPT_PAGE(pPage);
  }
  pPage->nFree = (u16)(nFree - iCellFirst);
  return SQLITE_OK;
}

/*
................................................................................
        sz = pParent->xCellSize(pParent, pCell);
      }
    }
    iOvflSpace += sz;
    assert( sz<=pBt->maxLocal+23 );
    assert( iOvflSpace <= (int)pBt->pageSize );
    insertCell(pParent, nxDiv+i, pCell, sz, pTemp, pNew->pgno, &rc);
    if( rc!=SQLITE_OK ) goto balance_cleanup;
    assert( sqlite3PagerIswriteable(pParent->pDbPage) );
  }

  /* Now update the actual sibling pages. The order in which they are updated
  ** is important, as this code needs to avoid disrupting any page from which
  ** cells may still to be read. In practice, this means:
  **

  assert( gap<=65536 );
  /* EVIDENCE-OF: R-29356-02391 If the database uses a 65536-byte page size
  ** and the reserved space is zero (the usual value for reserved space)
  ** then the cell content offset of an empty page wants to be 65536.
  ** However, that integer is too large to be stored in a 2-byte unsigned
  ** integer, so a value of 0 is used in its place. */
  top = get2byte(&data[hdr+5]);
  assert( top<=(int)pPage->pBt->usableSize ); /* by btreeComputeFreeSpace() */
  if( gap>top ){
    if( top==0 && ALWAYS(pPage->pBt->usableSize==65536) ){
      top = 65536;
    }else{
      return SQLITE_CORRUPT_PAGE(pPage);
    }
  }

  /* If there is enough space between gap and top for one more cell pointer,
................................................................................
  /* At this point, nFree contains the sum of the offset to the start
  ** of the cell-content area plus the number of free bytes within
  ** the cell-content area. If this is greater than the usable-size
  ** of the page, then the page must be corrupted. This check also
  ** serves to verify that the offset to the start of the cell-content
  ** area, according to the page header, lies within the page.
  */
  if( nFree>usableSize || nFree<iCellFirst ){
    return SQLITE_CORRUPT_PAGE(pPage);
  }
  pPage->nFree = (u16)(nFree - iCellFirst);
  return SQLITE_OK;
}

/*
................................................................................
        sz = pParent->xCellSize(pParent, pCell);
      }
    }
    iOvflSpace += sz;
    assert( sz<=pBt->maxLocal+23 );
    assert( iOvflSpace <= (int)pBt->pageSize );
    insertCell(pParent, nxDiv+i, pCell, sz, pTemp, pNew->pgno, &rc);
    if( NEVER(rc!=SQLITE_OK) ) goto balance_cleanup;
    assert( sqlite3PagerIswriteable(pParent->pDbPage) );
  }

  /* Now update the actual sibling pages. The order in which they are updated
  ** is important, as this code needs to avoid disrupting any page from which
  ** cells may still to be read. In practice, this means:
  **