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Overview
Comment:Improvements to comments in btree.c:freeSpace(). Added a testcase() macro to verify a boundary case is tested in sqlite3BtreeInitPage(). (CVS 6862)
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SHA1: 5ac991b3cea214095b8369e85f3e0ad8e5059ad6
User & Date: drh 2009-07-08 16:54:40.000
Context
2009-07-08
18:12
Add another boundary-condition testcase() macro to btree.c. Correct the comment on modifyPagePointer(). (CVS 6863) (check-in: fed66e8695 user: drh tags: trunk)
16:54
Improvements to comments in btree.c:freeSpace(). Added a testcase() macro to verify a boundary case is tested in sqlite3BtreeInitPage(). (CVS 6862) (check-in: 5ac991b3ce user: drh tags: trunk)
15:14
Comment out sqlite3BtreeFlags() when not in debug mode. Tweaks to database corruption detection logic in freeSpace(). (CVS 6861) (check-in: 196cbf8229 user: drh tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/btree.c. 
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/*
** 2004 April 6
**
** The author disclaims copyright to this source code.  In place of
** 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 1.661 2009/07/08 15:14:50 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"













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/*
** 2004 April 6
**
** The author disclaims copyright to this source code.  In place of
** 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 1.662 2009/07/08 16:54:40 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"
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  /* Overwrite deleted information with zeros when the SECURE_DELETE 
  ** option is enabled at compile-time */
  memset(&data[start], 0, size);
#endif

  /* Add the space back into the linked list of freeblocks.  Note that
  ** even though the freeblock list was checked by sqlite3BtreeInitPage(),
  ** sqlite3BtreeInitPage() did not detect overlapping freeblocks or
  ** freeblocks that overlapped cells.  If there was overlap then

  ** subsequent insert operations might have corrupted the freelist.
  ** So we do need to check for corruption while scanning the freelist.

  */
  hdr = pPage->hdrOffset;
  addr = hdr + 1;
  iLast = pPage->pBt->usableSize - 4;
  assert( start<=iLast );
  while( (pbegin = get2byte(&data[addr]))<start && pbegin>0 ){
    if( pbegin<addr+4 ){








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  /* Overwrite deleted information with zeros when the SECURE_DELETE 
  ** option is enabled at compile-time */
  memset(&data[start], 0, size);
#endif

  /* Add the space back into the linked list of freeblocks.  Note that
  ** even though the freeblock list was checked by sqlite3BtreeInitPage(),
  ** sqlite3BtreeInitPage() did not detect overlapping cells or
  ** freeblocks that overlapped cells.   Nor does it detect when the
  ** cell content area exceeds the value in the page header.  If these
  ** situations arise, then subsequent insert operations might corrupt
  ** the freelist.  So we do need to check for corruption while scanning
  ** the freelist.
  */
  hdr = pPage->hdrOffset;
  addr = hdr + 1;
  iLast = pPage->pBt->usableSize - 4;
  assert( start<=iLast );
  while( (pbegin = get2byte(&data[addr]))<start && pbegin>0 ){
    if( pbegin<addr+4 ){
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    pPage->cellOffset = cellOffset = hdr + 12 - 4*pPage->leaf;
    top = get2byte(&data[hdr+5]);
    pPage->nCell = get2byte(&data[hdr+3]);
    if( pPage->nCell>MX_CELL(pBt) ){
      /* To many cells for a single page.  The page must be corrupt */
      return SQLITE_CORRUPT_BKPT;
    }


    /* A malformed database page might cause use to read past the end
    ** of page when parsing a cell.  
    **
    ** The following block of code checks early to see if a cell extends
    ** past the end of a page boundary and causes SQLITE_CORRUPT to be 
    ** returned if it does.








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    pPage->cellOffset = cellOffset = hdr + 12 - 4*pPage->leaf;
    top = get2byte(&data[hdr+5]);
    pPage->nCell = get2byte(&data[hdr+3]);
    if( pPage->nCell>MX_CELL(pBt) ){
      /* To many cells for a single page.  The page must be corrupt */
      return SQLITE_CORRUPT_BKPT;
    }
    testcase( pPage->nCell==MX_CELL(pBt) );

    /* A malformed database page might cause use to read past the end
    ** of page when parsing a cell.  
    **
    ** The following block of code checks early to see if a cell extends
    ** past the end of a page boundary and causes SQLITE_CORRUPT to be 
    ** returned if it does.
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