SQLite

** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.171 2004/11/03 08:44:06 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include "pager.h"
#include <assert.h>
#include <string.h>

}

/*
** Forward declaration
*/
static int syncJournal(Pager*);


/*
** Unlink pPg from it's hash chain. Also set the page number to 0 to indicate
** that the page is not part of any hash chain. This is required because the
** sqlite3pager_movepage() routine can leave a page in the 
** pNextFree/pPrevFree list that is not a part of any hash-chain.
*/
static void unlinkHashChain(Pager *pPager, PgHdr *pPg){
  if( pPg->pgno==0 ){
    /* If the page number is zero, then this page is not in any hash chain. */
    return;
  }
  if( pPg->pNextHash ){
    pPg->pNextHash->pPrevHash = pPg->pPrevHash;
  }
  if( pPg->pPrevHash ){
    assert( pPager->aHash[pager_hash(pPg->pgno)]!=pPg );
    pPg->pPrevHash->pNextHash = pPg->pNextHash;
  }else{
    int h = pager_hash(pPg->pgno);
    assert( pPager->aHash[h]==pPg );
    pPager->aHash[h] = pPg->pNextHash;
  }

  pPg->pgno = 0;
  pPg->pNextHash = pPg->pPrevHash = 0;
}

/*
** Unlink a page from the free list (the list of all pages where nRef==0)
** and from its hash collision chain.
*/
static void unlinkPage(PgHdr *pPg){
  Pager *pPager = pPg->pPager;

  }else{
    assert( pPager->pLast==pPg );
    pPager->pLast = pPg->pPrevFree;
  }
  pPg->pNextFree = pPg->pPrevFree = 0;

  /* Unlink from the pgno hash table */
  unlinkHashChain(pPager, pPg);
/*
  if( pPg->pNextHash ){
    pPg->pNextHash->pPrevHash = pPg->pPrevHash;
  }
  if( pPg->pPrevHash ){
    pPg->pPrevHash->pNextHash = pPg->pNextHash;
  }else{
    int h = pager_hash(pPg->pgno);
    assert( pPager->aHash[h]==pPg );
    pPager->aHash[h] = pPg->pNextHash;
  }
  pPg->pNextHash = pPg->pPrevHash = 0;
*/
}

/*
** This routine is used to truncate an in-memory database.  Delete
** all pages whose pgno is larger than pPager->dbSize and is unreferenced.
** Referenced pages larger than pPager->dbSize are zeroed.
*/

  }

sync_exit:
  return rc;
}

#ifndef SQLITE_OMIT_AUTOVACUUM

/*
** Move the page identified by pData to location pgno in the file. 
**
** There must be no references to the current page pgno. If current page
** pgno is not already in the rollback journal, it is not written there by
** by this routine. The same applies to the page pData refers to on entry to
** this routine.
**
** References to the page refered to by pData remain valid. Updating any
** meta-data associated with page pData (i.e. data stored in the nExtra bytes
** allocated along with the page) is the responsibility of the caller.
**
** A transaction must be active when this routine is called, however it is 
** illegal to call this routine if a statment transaction is active.
*/
int sqlite3pager_movepage(Pager *pPager, void *pData, Pgno pgno){
  PgHdr *pPg = DATA_TO_PGHDR(pData);
  PgHdr *pPgOld; 
  int h;

  assert( !pPager->stmtInUse );

  assert( pPg->nRef>0 );

  /* Unlink pPg from it's hash-chain */







  unlinkHashChain(pPager, pPg);


  /* If the cache contains a page with page-number pgno exists, remove it


  ** from it's hash chain.
  */
  pPgOld = pager_lookup(pPager, pgno);
  if( pPgOld ){

    assert( pPgOld->nRef==0 );
    unlinkHashChain(pPager, pPgOld);
    pPgOld->dirty = 0;
  }









  /* Change the page number for pPg and insert it into the new hash-chain. */
  pPg->pgno = pgno;
  h = pager_hash(pgno);
  if( pPager->aHash[h] ){
    assert( pPager->aHash[h]->pPrevHash==0 );
    pPager->aHash[h]->pPrevHash = pPg;
  }
  pPg->pNextHash = pPager->aHash[h];
  pPager->aHash[h] = pPg;
  pPg->pPrevHash = 0;






  pPg->dirty = 1;
  pPager->dirtyCache = 1;

  return SQLITE_OK;
}
#endif