SQLite

  if( pCur->eState!=CURSOR_VALID || pCur->skipNext!=0 ){
    *pHasMoved = 1;
  }else{
    *pHasMoved = 0;
  }
  return SQLITE_OK;
}

/*
** Set up the correct data pointers for a MemPage
*/
static u8 *btreeGetData(MemPage *pPage){
  pPage->aData = sqlite3PagerGetData(pPage->pDbPage);
  pPage->aDataEnd = &pPage->aData[pPage->pBt->usableSize];
  pPage->aCellIdx = &pPage->aData[pPage->cellOffset];
  return pPage->aData;
}

/*
** Make a btree page is writable.
*/
static int btreeMakePageWriteable(MemPage *pPage){
  int rc;

  rc = sqlite3PagerWrite(pPage->pDbPage);
  btreeGetData(pPage);


  return rc;
}

#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Given a page number of a regular database page, return the page
** number for the pointer-map page that contains the entry for the

  }
  assert( offset <= (int)pBt->usableSize-5 );
  pPtrmap = (u8 *)sqlite3PagerGetData(pDbPage);

  if( eType!=pPtrmap[offset] || get4byte(&pPtrmap[offset+1])!=parent ){
    TRACE(("PTRMAP_UPDATE: %d->(%d,%d)\n", key, eType, parent));
    *pRC= rc = sqlite3PagerWrite(pDbPage);
    pPtrmap = sqlite3PagerGetData(pDbPage);
    if( rc==SQLITE_OK ){
      pPtrmap[offset] = eType;
      put4byte(&pPtrmap[offset+1], parent);
    }
  }

ptrmap_exit:

** call to btreeGetPage.
*/
static void releasePage(MemPage *pPage){
  if( pPage ){
    assert( pPage->aData );
    assert( pPage->pBt );
    assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
    /* assert( sqlite3PagerGetData(pPage->pDbPage)==pPage->aData ); */
    assert( sqlite3_mutex_held(pPage->pBt->mutex) );
    sqlite3PagerUnref(pPage->pDbPage);
  }
}

/*
** During a rollback, when the pager reloads information into the cache

*/
static int lockBtree(BtShared *pBt){
  int rc;              /* Result code from subfunctions */
  MemPage *pPage1;     /* Page 1 of the database file */
  int nPage;           /* Number of pages in the database */
  int nPageFile = 0;   /* Number of pages in the database file */
  int nPageHeader;     /* Number of pages in the database according to hdr */
  u8 *page1;           /* Content of page 1 */

  assert( sqlite3_mutex_held(pBt->mutex) );
  assert( pBt->pPage1==0 );
  rc = sqlite3PagerSharedLock(pBt->pPager);
  if( rc!=SQLITE_OK ) return rc;
  rc = btreeGetPage(pBt, 1, &pPage1, 0);
  if( rc!=SQLITE_OK ) return rc;

  /* Do some checking to help insure the file we opened really is
  ** a valid database file. 
  */
  page1 = btreeGetData(pPage1);
  nPage = nPageHeader = get4byte(&page1[28]);
  sqlite3PagerPagecount(pBt->pPager, &nPageFile);
  if( nPage==0 || memcmp(24+page1, 92+page1, 4)!=0 ){
    nPage = nPageFile;
  }
  if( nPage>0 ){
    u32 pageSize;
    u32 usableSize;

    rc = SQLITE_NOTADB;
    if( memcmp(page1, zMagicHeader, 16)!=0 ){
      goto page1_init_failed;
    }

#ifdef SQLITE_OMIT_WAL
    if( page1[18]>1 ){

  if( pBt->nPage>0 ){
    return SQLITE_OK;
  }
  pP1 = pBt->pPage1;
  assert( pP1!=0 );
  rc = btreeMakePageWriteable(pP1);
  if( rc ) return rc;
  data = btreeGetData(pP1);
  memcpy(data, zMagicHeader, sizeof(zMagicHeader));
  assert( sizeof(zMagicHeader)==16 );
  data[16] = (u8)((pBt->pageSize>>8)&0xff);
  data[17] = (u8)((pBt->pageSize>>16)&0xff);
  data[18] = 1;
  data[19] = 1;
  assert( pBt->usableSize<=pBt->pageSize && pBt->usableSize+255>=pBt->pageSize);

      /* If the db-size header field is incorrect (as it may be if an old
      ** client has been writing the database file), update it now. Doing
      ** this sooner rather than later means the database size can safely 
      ** re-read the database size from page 1 if a savepoint or transaction
      ** rollback occurs within the transaction.
      */
      btreeGetData(pPage1);
      if( pBt->nPage!=get4byte(&pPage1->aData[28]) ){
        rc = btreeMakePageWriteable(pPage1);
        if( rc==SQLITE_OK ){
          put4byte(&pPage1->aData[28], pBt->nPage);
        }
      }
    }

  assert( sqlite3_mutex_held(pBt->mutex) );
  assert( iLastPg>nFin );

  if( !PTRMAP_ISPAGE(pBt, iLastPg) && iLastPg!=PENDING_BYTE_PAGE(pBt) ){
    u8 eType;
    Pgno iPtrPage;

    btreeGetData(pBt->pPage1);
    nFreeList = get4byte(&pBt->pPage1->aData[36]);
    if( nFreeList==0 ){
      return SQLITE_DONE;
    }

    rc = ptrmapGet(pBt, iLastPg, &eType, &iPtrPage);
    if( rc!=SQLITE_OK ){

      /* It is not possible to create a database for which the final page
      ** is either a pointer-map page or the pending-byte page. If one
      ** is encountered, this indicates corruption.
      */
      return SQLITE_CORRUPT_BKPT;
    }

    btreeGetData(pBt->pPage1);
    nFree = get4byte(&pBt->pPage1->aData[36]);
    nEntry = pBt->usableSize/5;
    nPtrmap = (nFree-nOrig+PTRMAP_PAGENO(pBt, nOrig)+nEntry)/nEntry;
    nFin = nOrig - nFree - nPtrmap;
    if( nOrig>PENDING_BYTE_PAGE(pBt) && nFin<PENDING_BYTE_PAGE(pBt) ){
      nFin--;
    }

    assert( op==SAVEPOINT_RELEASE || op==SAVEPOINT_ROLLBACK );
    assert( iSavepoint>=0 || (iSavepoint==-1 && op==SAVEPOINT_ROLLBACK) );
    sqlite3BtreeEnter(p);
    rc = sqlite3PagerSavepoint(pBt->pPager, op, iSavepoint);
    if( rc==SQLITE_OK ){
      if( iSavepoint<0 && pBt->initiallyEmpty ) pBt->nPage = 0;
      rc = newDatabase(pBt);
      pBt->nPage = get4byte(28 + btreeGetData(pBt->pPage1));

      /* The database size was written into the offset 28 of the header
      ** when the transaction started, so we know that the value at offset
      ** 28 is nonzero. */
      assert( pBt->nPage>0 );
    }
    sqlite3BtreeLeave(p);

        ** output buffer, bypassing the page-cache altogether. This speeds
        ** up loading large records that span many overflow pages.
        */
        if( eOp==0                                             /* (1) */
         && offset==0                                          /* (2) */
         && pBt->inTransaction==TRANS_READ                     /* (4) */
         && (fd = sqlite3PagerFile(pBt->pPager))->pMethods     /* (3) */
         && btreeGetData(pBt->pPage1)[19]==0x01                /* (5) */
        ){
          u8 aSave[4];
          u8 *aWrite = &pBuf[-4];
          memcpy(aSave, aWrite, 4);
          rc = sqlite3OsRead(fd, aWrite, a+4, pBt->pageSize * (nextPage-1));
          nextPage = get4byte(aWrite);
          memcpy(aWrite, aSave, 4);

  MemPage *pTrunk = 0;
  MemPage *pPrevTrunk = 0;
  Pgno mxPage;     /* Total size of the database file */

  assert( sqlite3_mutex_held(pBt->mutex) );
  pPage1 = pBt->pPage1;
  mxPage = btreePagecount(pBt);
  n = get4byte(&btreeGetData(pPage1)[36]);
  testcase( n==mxPage-1 );
  if( n>=mxPage ){
    return SQLITE_CORRUPT_BKPT;
  }
  if( n>0 ){
    /* There are pages on the freelist.  Reuse one of those pages. */
    Pgno iTrunk;

          int noContent;
          *pPgno = iPage;
          TRACE(("ALLOCATE: %d was leaf %d of %d on trunk %d"
                 ": %d more free pages\n",
                 *pPgno, closest+1, k, pTrunk->pgno, n-1));
          rc = btreeMakePageWriteable(pTrunk);
          if( rc ) goto end_allocate_page;
          aData = pTrunk->aData;
          if( closest<k-1 ){
            memcpy(&aData[8+closest*4], &aData[4+k*4], 4);
          }
          put4byte(&aData[4], k-1);
          noContent = !btreeGetHasContent(pBt, *pPgno);
          rc = btreeGetPage(pBt, *pPgno, ppPage, noContent);
          if( rc==SQLITE_OK ){

  sqlite3BtreeEnter(p);
  assert( p->inTrans>TRANS_NONE );
  assert( SQLITE_OK==querySharedCacheTableLock(p, MASTER_ROOT, READ_LOCK) );
  assert( pBt->pPage1 );
  assert( idx>=0 && idx<=15 );

  *pMeta = get4byte(&btreeGetData(pBt->pPage1)[36 + idx*4]);

  /* If auto-vacuum is disabled in this build and this is an auto-vacuum
  ** database, mark the database as read-only.  */
#ifdef SQLITE_OMIT_AUTOVACUUM
  if( idx==BTREE_LARGEST_ROOT_PAGE && *pMeta>0 ) pBt->readOnly = 1;
#endif

    sCheck.anRef[i] = 1;
  }
  sqlite3StrAccumInit(&sCheck.errMsg, zErr, sizeof(zErr), 20000);
  sCheck.errMsg.useMalloc = 2;

  /* Check the integrity of the freelist
  */
  btreeGetData(pBt->pPage1);
  checkList(&sCheck, 1, get4byte(&pBt->pPage1->aData[32]),
            get4byte(&pBt->pPage1->aData[36]), "Main freelist: ");

  /* Check all the tables.
  */
  for(i=0; (int)i<nRoot && sCheck.mxErr; i++){
    if( aRoot[i]==0 ) continue;

  /* If setting the version fields to 1, do not automatically open the
  ** WAL connection, even if the version fields are currently set to 2.
  */
  pBt->doNotUseWAL = (u8)(iVersion==1);

  rc = sqlite3BtreeBeginTrans(pBtree, 0);
  if( rc==SQLITE_OK ){
    u8 *aData = btreeGetData(pBt->pPage1);
    if( aData[18]!=(u8)iVersion || aData[19]!=(u8)iVersion ){
      rc = sqlite3BtreeBeginTrans(pBtree, 2);
      if( rc==SQLITE_OK ){
        rc = btreeMakePageWriteable(pBt->pPage1);
        if( rc==SQLITE_OK ){
          aData = btreeGetData(pBt->pPage1);
          aData[18] = (u8)iVersion;
          aData[19] = (u8)iVersion;
        }
      }
    }
  }

  pBt->doNotUseWAL = 0;
  return rc;
}

** contents of the pager cache are discarded before switching back to 
** the OPEN state. Regardless of whether the pager is in exclusive-mode
** or not, any journal file left in the file-system will be treated
** as a hot-journal and rolled back the next time a read-transaction
** is opened (by this or by any other connection).
*/
static void pager_unlock(Pager *pPager){
  PgHdr *pPg;

  assert( pPager->eState==PAGER_READER 
       || pPager->eState==PAGER_OPEN 
       || pPager->eState==PAGER_ERROR 
  );

  sqlite3BitvecDestroy(pPager->pInJournal);

  }

  /* If Pager.errCode is set, the contents of the pager cache cannot be
  ** trusted. Now that there are no outstanding references to the pager,
  ** it can safely move back to PAGER_OPEN state. This happens in both
  ** normal and exclusive-locking mode.
  */
  if( pPager->errCode ){
    assert( !MEMDB );
    pager_reset(pPager);
    pPager->changeCountDone = pPager->tempFile;
    pPager->eState = PAGER_OPEN;
    pPager->errCode = SQLITE_OK;




  }

  pPager->journalOff = 0;
  pPager->journalHdr = 0;
  pPager->setMaster = 0;

  pPg = 0;
  sqlite3PcacheFetch(pPager->pPCache, 1, 0, &pPg);
  if( pPg ){
    /* assert( sqlite3PcachePagecount(pPager->pPCache)==1 ); */
    pPg->pData = pPg->pBuf;
    sqlite3PcacheRelease(pPg);
  }else{
    /*assert( sqlite3PcachePagecount(pPager->pPCache)==0 );*/
  }
  sqlite3OsUnmap(pPager->fd, pPager->pMapObject);
  pPager->pMapObject = 0;
  pPager->aFileContent = 0;
  pPager->nFileContent = 0;
}

/*
** This function is called whenever an IOERR or FULL error that requires
** the pager to transition into the ERROR state may ahve occurred.
** The first argument is a pointer to the pager structure, the second 
** the error-code about to be returned by a pager API function. The 

    assert( rc!=SQLITE_OK || pPager->eState==PAGER_WRITER_LOCKED );
    assert( assert_pager_state(pPager) );
  }

  PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager)));
  return rc;
}

/*
** Make a copy of page content into malloced space.
*/
void makePageWriteable(Pager *pPager, PgHdr *pPg){
  if( pPg->pData!=pPg->pBuf ){
    memcpy(pPg->pBuf, pPg->pData, pPager->pageSize);
    pPg->pData = pPg->pBuf;
  }
}

/*
** Mark a single data page as writeable. The page is written into the 
** main journal or sub-journal as required. If the page is written into
** one of the journals, the corresponding bit is set in the 
** Pager.pInJournal bitvec and the PagerSavepoint.pInSavepoint bitvecs
** of any open savepoints as appropriate.

    rc = pager_open_journal(pPager);
    if( rc!=SQLITE_OK ) return rc;
  }
  assert( pPager->eState>=PAGER_WRITER_CACHEMOD );
  assert( assert_pager_state(pPager) );

  /* Make sure page content is held in malloced memory */

  makePageWriteable(pPager, pPg);
  pData = pPg->pData;


  /* Mark the page as dirty.  If the page has already been written
  ** to the journal then we can return right away.
  */
  sqlite3PcacheMakeDirty(pPg);
  if( pageInJournal(pPg) && !subjRequiresPage(pPg) ){
    assert( !pagerUseWal(pPager) );

      sqlite3PcacheMove(pPgOld, pPager->dbSize+1);
    }else{
      sqlite3PcacheDrop(pPgOld);
    }
  }

  origPgno = pPg->pgno;
  makePageWriteable(pPager, pPg);
  sqlite3PcacheMove(pPg, pgno);
  sqlite3PcacheMakeDirty(pPg);

  /* For an in-memory database, make sure the original page continues
  ** to exist, in case the transaction needs to roll back.  Use pPgOld
  ** as the original page since it has already been allocated.
  */

  return SQLITE_OK;
}
#endif

/*
** Return a pointer to the data for the specified page.
*/
u8 *sqlite3PagerGetData(DbPage *pPg){
  assert( pPg->nRef>0 || pPg->pPager->memDb );
  return (u8*)pPg->pData;
}

/*
** Return a pointer to the Pager.nExtra bytes of "extra" space 
** allocated along with the specified page.
*/
void *sqlite3PagerGetExtra(DbPage *pPg){

void sqlite3PagerUnref(DbPage*);

/* Operations on page references. */
int sqlite3PagerWrite(DbPage*);
void sqlite3PagerDontWrite(DbPage*);
int sqlite3PagerMovepage(Pager*,DbPage*,Pgno,int);
int sqlite3PagerPageRefcount(DbPage*);
u8 *sqlite3PagerGetData(DbPage *); 
void *sqlite3PagerGetExtra(DbPage *); 

/* Functions used to manage pager transactions and savepoints. */
void sqlite3PagerPagecount(Pager*, int*);
int sqlite3PagerBegin(Pager*, int exFlag, int);
int sqlite3PagerCommitPhaseOne(Pager*,const char *zMaster, int);
int sqlite3PagerExclusiveLock(Pager*);

*/
static void pcacheUnpin(PgHdr *p){
  PCache *pCache = p->pCache;
  if( pCache->bPurgeable ){
    if( p->pgno==1 ){
      pCache->pPage1 = 0;
    }
    sqlite3GlobalConfig.pcache2.xUnpin(pCache->pCache, p->pPage, 1);
  }
}

/*************************************************** General Interfaces ******
**
** Initialize and shutdown the page cache subsystem. Neither of these 
** functions are threadsafe.