** 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 1.656 2009/07/07 15:47:12 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"

................................................................................
** end of the page and all free space is collected into one
** big FreeBlk that occurs in between the header and cell
** pointer array and the cell content area.
*/
static int defragmentPage(MemPage *pPage){
  int i;                     /* Loop counter */
  int pc;                    /* Address of a i-th cell */
  int addr;                  /* Offset of first byte after cell pointer array */
  int hdr;                   /* Offset to the page header */
  int size;                  /* Size of a cell */
  int usableSize;            /* Number of usable bytes on a page */
  int cellOffset;            /* Offset to the cell pointer array */
  int cbrk;                  /* Offset to the cell content area */
  int nCell;                 /* Number of cells on the page */
  unsigned char *data;       /* The page data */
  unsigned char *temp;       /* Temp area for cell content */




  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  assert( pPage->pBt!=0 );
  assert( pPage->pBt->usableSize <= SQLITE_MAX_PAGE_SIZE );
  assert( pPage->nOverflow==0 );
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  temp = sqlite3PagerTempSpace(pPage->pBt->pPager);
................................................................................
  cellOffset = pPage->cellOffset;
  nCell = pPage->nCell;
  assert( nCell==get2byte(&data[hdr+3]) );
  usableSize = pPage->pBt->usableSize;
  cbrk = get2byte(&data[hdr+5]);
  memcpy(&temp[cbrk], &data[cbrk], usableSize - cbrk);
  cbrk = usableSize;


  for(i=0; i<nCell; i++){
    u8 *pAddr;     /* The i-th cell pointer */
    pAddr = &data[cellOffset + i*2];
    pc = get2byte(pAddr);
    if( pc>=usableSize ){




      return SQLITE_CORRUPT_BKPT;
    }


    size = cellSizePtr(pPage, &temp[pc]);
    cbrk -= size;





    if( cbrk<cellOffset+2*nCell || pc+size>usableSize ){
      return SQLITE_CORRUPT_BKPT;
    }

    assert( cbrk+size<=usableSize && cbrk>=0 );
    memcpy(&data[cbrk], &temp[pc], size);
    put2byte(pAddr, cbrk);
  }
  assert( cbrk>=cellOffset+2*nCell );
  put2byte(&data[hdr+5], cbrk);
  data[hdr+1] = 0;
  data[hdr+2] = 0;
  data[hdr+7] = 0;
  addr = cellOffset+2*nCell;
  memset(&data[addr], 0, cbrk-addr);
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  if( cbrk-addr!=pPage->nFree ){
    return SQLITE_CORRUPT_BKPT;
  }
  return SQLITE_OK;
}

/*
** Allocate nByte bytes of space from within the B-Tree page passed

** 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 1.657 2009/07/07 17:38:39 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"

................................................................................
** end of the page and all free space is collected into one
** big FreeBlk that occurs in between the header and cell
** pointer array and the cell content area.
*/
static int defragmentPage(MemPage *pPage){
  int i;                     /* Loop counter */
  int pc;                    /* Address of a i-th cell */

  int hdr;                   /* Offset to the page header */
  int size;                  /* Size of a cell */
  int usableSize;            /* Number of usable bytes on a page */
  int cellOffset;            /* Offset to the cell pointer array */
  int cbrk;                  /* Offset to the cell content area */
  int nCell;                 /* Number of cells on the page */
  unsigned char *data;       /* The page data */
  unsigned char *temp;       /* Temp area for cell content */
  int iCellFirst;            /* First allowable cell index */
  int iCellLast;             /* Last possible cell index */


  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  assert( pPage->pBt!=0 );
  assert( pPage->pBt->usableSize <= SQLITE_MAX_PAGE_SIZE );
  assert( pPage->nOverflow==0 );
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  temp = sqlite3PagerTempSpace(pPage->pBt->pPager);
................................................................................
  cellOffset = pPage->cellOffset;
  nCell = pPage->nCell;
  assert( nCell==get2byte(&data[hdr+3]) );
  usableSize = pPage->pBt->usableSize;
  cbrk = get2byte(&data[hdr+5]);
  memcpy(&temp[cbrk], &data[cbrk], usableSize - cbrk);
  cbrk = usableSize;
  iCellFirst = cellOffset + 2*nCell;
  iCellLast = usableSize - 4;
  for(i=0; i<nCell; i++){
    u8 *pAddr;     /* The i-th cell pointer */
    pAddr = &data[cellOffset + i*2];
    pc = get2byte(pAddr);
#if !defined(SQLITE_ENABLE_OVERSIZE_CELL_CHECK)
    /* These conditions have already been verified in sqlite3BtreeInitPage()
    ** if SQLITE_ENABLE_OVERSIZE_CELL_CHECK is defined 
    */
    if( pc<iCellFirst || pc>iCellLast ){
      return SQLITE_CORRUPT_BKPT;
    }
#endif
    assert( pc>=iCellFirst && pc<=iCellLast );
    size = cellSizePtr(pPage, &temp[pc]);
    cbrk -= size;
#if defined(SQLITE_ENABLE_OVERSIZE_CELL_CHECK)
    if( cbrk<iCellFirst ){
      return SQLITE_CORRUPT_BKPT;
    }
#else
    if( cbrk<iCellFirst || pc+size>usableSize ){
      return SQLITE_CORRUPT_BKPT;
    }
#endif
    assert( cbrk+size<=usableSize && cbrk>iCellFirst );
    memcpy(&data[cbrk], &temp[pc], size);
    put2byte(pAddr, cbrk);
  }
  assert( cbrk>=iCellFirst );
  put2byte(&data[hdr+5], cbrk);
  data[hdr+1] = 0;
  data[hdr+2] = 0;
  data[hdr+7] = 0;
  memset(&data[iCellFirst], 0, cbrk-iCellFirst);

  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  if( cbrk-iCellFirst!=pPage->nFree ){
    return SQLITE_CORRUPT_BKPT;
  }
  return SQLITE_OK;
}

/*
** Allocate nByte bytes of space from within the B-Tree page passed