** 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 1.200 2004/11/03 03:01:17 danielk1977 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.
................................................................................

  /* Figure out how many free-pages are in the database. If there are no
  ** free pages, then auto-vacuum is a no-op.
  */
  nFreeList = get4byte(&pBt->pPage1->aData[36]);
  if( nFreeList==0 ) return SQLITE_OK;




  origDbSize = sqlite3pager_pagecount(pPager);
  finDbSize = origDbSize - nFreeList;
  TRACE(("AUTOVACUUM: Begin (db size %d->%d)\n", origDbSize, finDbSize));

  /* Note: This is temporary code for use during development of auto-vacuum. 
  **
  ** Inspect the pointer map to make sure there are no root pages with a
................................................................................
  ** to a free page earlier in the file (somewhere before finDbSize).
  */
  for( iDbPage=finDbSize+1; iDbPage<=origDbSize; iDbPage++ ){
    rc = ptrmapGet(pBt, iDbPage, &eType, &iPtrPage);
    if( rc!=SQLITE_OK ) goto autovacuum_out;
    assert( eType!=PTRMAP_ROOTPAGE );

    /* If iDbPage is already on the free-list, do not swap it. */
    if( eType==PTRMAP_FREEPAGE ){

      continue;
    }
    rc = getPage(pBt, iDbPage, &pDbMemPage);
    if( rc!=SQLITE_OK ) goto autovacuum_out;
    pDbPage = pDbMemPage->aData;

    /* Find the next page in the free-list that is not already at the end 

** 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 1.201 2004/11/03 03:52:37 danielk1977 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.
................................................................................

  /* Figure out how many free-pages are in the database. If there are no
  ** free pages, then auto-vacuum is a no-op.
  */
  nFreeList = get4byte(&pBt->pPage1->aData[36]);
  if( nFreeList==0 ) return SQLITE_OK;

  /* TODO: This does not calculate finDbSize correctly for the case where
  ** pointer-map pages must be deallocated.
  */
  origDbSize = sqlite3pager_pagecount(pPager);
  finDbSize = origDbSize - nFreeList;
  TRACE(("AUTOVACUUM: Begin (db size %d->%d)\n", origDbSize, finDbSize));

  /* Note: This is temporary code for use during development of auto-vacuum. 
  **
  ** Inspect the pointer map to make sure there are no root pages with a
................................................................................
  ** to a free page earlier in the file (somewhere before finDbSize).
  */
  for( iDbPage=finDbSize+1; iDbPage<=origDbSize; iDbPage++ ){
    rc = ptrmapGet(pBt, iDbPage, &eType, &iPtrPage);
    if( rc!=SQLITE_OK ) goto autovacuum_out;
    assert( eType!=PTRMAP_ROOTPAGE );

    /* If iDbPage is a free or pointer map page, do not swap it. */
    if( eType==PTRMAP_FREEPAGE ||
        iDbPage==PTRMAP_PAGENO(pBt->pageSize, iDbPage) ){
      continue;
    }
    rc = getPage(pBt, iDbPage, &pDbMemPage);
    if( rc!=SQLITE_OK ) goto autovacuum_out;
    pDbPage = pDbMemPage->aData;

    /* Find the next page in the free-list that is not already at the end