** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.139 2004/05/14 21:12:23 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
**     "Sorting And Searching", pages 473-480. Addison-Wesley
**     Publishing Company, Reading, Massachusetts.
................................................................................
static int initPage(
  MemPage *pPage,        /* The page to be initialized */
  MemPage *pParent       /* The parent.  Might be NULL */
){
  int c, pc, i, hdr;
  unsigned char *data;
  int usableSize;
  /* int sumCell = 0;       // Total size of all cells */



  assert( pPage->pBt!=0 );
  assert( pParent==0 || pParent->pBt==pPage->pBt );
  assert( pPage->pgno==sqlite3pager_pagenumber(pPage->aData) );
  assert( pPage->aData == &((unsigned char*)pPage)[-pPage->pBt->pageSize] );
  assert( pPage->pParent==0 || pPage->pParent==pParent );
................................................................................
  pPage->hasData = !(pPage->zeroData || (!pPage->leaf && pPage->leafData));
  pPage->isOverfull = 0;
  pPage->needRelink = 0;
  pPage->idxShift = 0;
  usableSize = pPage->pBt->usableSize;

  /* Initialize the cell count and cell pointers */

  pc = get2byte(&data[hdr+3]);

  while( pc>0 ){
    if( pc>=usableSize ) return SQLITE_CORRUPT;
    if( pPage->nCell>usableSize ) return SQLITE_CORRUPT;
    pPage->nCell++;

    pc = get2byte(&data[pc]);
  }
  if( resizeCellArray(pPage, pPage->nCell) ){
    return SQLITE_NOMEM;
  }
  pc = get2byte(&data[hdr+3]);
  for(i=0; pc>0; i++){
    pPage->aCell[i] = &data[pc];
    /* sumCell += cellSize(pPage, &data[pc]); */
    pc = get2byte(&data[pc]);
  }

  /* Compute the total free space on the page */
  pPage->nFree = data[hdr+5];
  pc = get2byte(&data[hdr+1]);


  while( pc>0 ){
    int next, size;
    if( pc>=usableSize ) return SQLITE_CORRUPT;

    next = get2byte(&data[pc]);
    size = get2byte(&data[pc+2]);
    if( next>0 && next<=pc+size+3 ) return SQLITE_CORRUPT;
    pPage->nFree += size;
    pc = next;
  }
  if( pPage->nFree>=usableSize ) return SQLITE_CORRUPT;

  /* Sanity check:  Cells and freespace and header must sum to the size
  ** a page.
  if( sumCell+pPage->nFree+hdr+10-pPage->leaf*4 != usableSize ){
    return SQLITE_CORRUPT;
  }
  */

  pPage->isInit = 1;
  pageIntegrity(pPage);
  return SQLITE_OK;
}

/*

** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.140 2004/05/15 00:29:24 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
**     "Sorting And Searching", pages 473-480. Addison-Wesley
**     Publishing Company, Reading, Massachusetts.
................................................................................
static int initPage(
  MemPage *pPage,        /* The page to be initialized */
  MemPage *pParent       /* The parent.  Might be NULL */
){
  int c, pc, i, hdr;
  unsigned char *data;
  int usableSize;
  int nCell, nFree;
  u8 *aCell[MX_PAGE_SIZE/2];


  assert( pPage->pBt!=0 );
  assert( pParent==0 || pParent->pBt==pPage->pBt );
  assert( pPage->pgno==sqlite3pager_pagenumber(pPage->aData) );
  assert( pPage->aData == &((unsigned char*)pPage)[-pPage->pBt->pageSize] );
  assert( pPage->pParent==0 || pPage->pParent==pParent );
................................................................................
  pPage->hasData = !(pPage->zeroData || (!pPage->leaf && pPage->leafData));
  pPage->isOverfull = 0;
  pPage->needRelink = 0;
  pPage->idxShift = 0;
  usableSize = pPage->pBt->usableSize;

  /* Initialize the cell count and cell pointers */
  i = 0;
  pc = get2byte(&data[hdr+3]);
  nCell = 0;
  while( pc>0 ){
    if( pc>=usableSize ) return SQLITE_CORRUPT;
    if( nCell>sizeof(aCell)/sizeof(aCell[0]) ) return SQLITE_CORRUPT;

    aCell[nCell++] = &data[pc];
    pc = get2byte(&data[pc]);
  }
  if( resizeCellArray(pPage, nCell) ){
    return SQLITE_NOMEM;
  }


  pPage->nCell = nCell;
  memcpy(pPage->aCell, aCell, nCell*sizeof(aCell[0]));



  /* Compute the total free space on the page */

  pc = get2byte(&data[hdr+1]);
  nFree = data[hdr+5];
  i = 0;
  while( pc>0 ){
    int next, size;
    if( pc>=usableSize ) return SQLITE_CORRUPT;
    if( i++>MX_PAGE_SIZE ) return SQLITE_CORRUPT;
    next = get2byte(&data[pc]);
    size = get2byte(&data[pc+2]);
    if( next>0 && next<=pc+size+3 ) return SQLITE_CORRUPT;
    nFree += size;
    pc = next;
  }
  pPage->nFree = nFree;




  if( nFree>=usableSize ) return SQLITE_CORRUPT;



  pPage->isInit = 1;
  pageIntegrity(pPage);
  return SQLITE_OK;
}

/*