** 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 1.503 2008/08/25 11:57:17 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"

................................................................................
    }else{
      /* Add the newly freed page as a leaf on the current trunk */
      rc = sqlite3PagerWrite(pTrunk->pDbPage);
      if( rc==SQLITE_OK ){
        put4byte(&pTrunk->aData[4], k+1);
        put4byte(&pTrunk->aData[8+k*4], pPage->pgno);
#ifndef SQLITE_SECURE_DELETE
        sqlite3PagerDontWrite(pPage->pDbPage);
#endif
      }
      TRACE(("FREE-PAGE: %d leaf on trunk page %d\n",pPage->pgno,pTrunk->pgno));
    }
    releasePage(pTrunk);
  }
  return rc;
................................................................................
          ** represent what they do.  Write() really means "put this page in the
          ** rollback journal and mark it as dirty so that it will be written
          ** to the database file later."  DontWrite() undoes the second part of
          ** that and prevents the page from being written to the database. The
          ** page is still on the rollback journal, though.  And that is the 
          ** whole point of this block: to put pages on the rollback journal. 
          */
          sqlite3PagerDontWrite(pDbPage);
        }
        sqlite3PagerUnref(pDbPage);
      }
    }

    /* Overwrite the data in page i of the target database */
    if( rc==SQLITE_OK && i!=iSkip && i<=nNewPage ){

** 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 1.504 2008/08/27 15:16:34 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"

................................................................................
    }else{
      /* Add the newly freed page as a leaf on the current trunk */
      rc = sqlite3PagerWrite(pTrunk->pDbPage);
      if( rc==SQLITE_OK ){
        put4byte(&pTrunk->aData[4], k+1);
        put4byte(&pTrunk->aData[8+k*4], pPage->pgno);
#ifndef SQLITE_SECURE_DELETE
        rc = sqlite3PagerDontWrite(pPage->pDbPage);
#endif
      }
      TRACE(("FREE-PAGE: %d leaf on trunk page %d\n",pPage->pgno,pTrunk->pgno));
    }
    releasePage(pTrunk);
  }
  return rc;
................................................................................
          ** represent what they do.  Write() really means "put this page in the
          ** rollback journal and mark it as dirty so that it will be written
          ** to the database file later."  DontWrite() undoes the second part of
          ** that and prevents the page from being written to the database. The
          ** page is still on the rollback journal, though.  And that is the 
          ** whole point of this block: to put pages on the rollback journal. 
          */
          rc = sqlite3PagerDontWrite(pDbPage);
        }
        sqlite3PagerUnref(pDbPage);
      }
    }

    /* Overwrite the data in page i of the target database */
    if( rc==SQLITE_OK && i!=iSkip && i<=nNewPage ){

** 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 1.482 2008/08/27 09:44:40 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"

/*
** Macros for troubleshooting.  Normally turned off
*/
................................................................................
  int nExtra;                 /* Add this many bytes to each in-memory page */
  int pageSize;               /* Number of bytes in a page */
  int nPage;                  /* Total number of in-memory pages */
  int mxPage;                 /* Maximum number of pages to hold in cache */
  Pgno mxPgno;                /* Maximum allowed size of the database */
  Bitvec *pInJournal;         /* One bit for each page in the database file */
  Bitvec *pInStmt;            /* One bit for each page in the database */

  char *zFilename;            /* Name of the database file */
  char *zJournal;             /* Name of the journal file */
  char *zDirectory;           /* Directory hold database and journal files */
  sqlite3_file *fd, *jfd;     /* File descriptors for database and journal */
  sqlite3_file *stfd;         /* File descriptor for the statement subjournal*/
  BusyHandler *pBusyHandler;  /* Pointer to sqlite.busyHandler */
  i64 journalOff;             /* Current byte offset in the journal file */
................................................................................
      ** delete the file out from under us.
      */
      if( pPager->journalOpen ){
        sqlite3OsClose(pPager->jfd);
        pPager->journalOpen = 0;
        sqlite3BitvecDestroy(pPager->pInJournal);
        pPager->pInJournal = 0;


      }

      /* If Pager.errCode is set, the contents of the pager cache cannot be
      ** trusted. Now that the pager file is unlocked, the contents of the
      ** cache can be discarded and the error code safely cleared.
      */
      if( pPager->errCode ){
................................................................................
      pPager->journalOpen = 0;
      if( rc==SQLITE_OK && !pPager->tempFile ){
        rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
      }
    }
    sqlite3BitvecDestroy(pPager->pInJournal);
    pPager->pInJournal = 0;


    sqlite3PcacheCleanAll(pPager->pPCache);
#ifdef SQLITE_CHECK_PAGES
    sqlite3PcacheIterate(pPager->pPCache, pager_set_pagehash);
#endif
    sqlite3PcacheSetFlags(pPager->pPCache, 
       ~(PGHDR_IN_JOURNAL | PGHDR_NEED_SYNC | PGHDR_ALWAYS_ROLLBACK), 0
    );
    pPager->dirtyCache = 0;
    pPager->nRec = 0;
  }else{
    assert( pPager->pInJournal==0 );
  }

................................................................................
  sqlite3EndBenignMalloc();
  PAGERTRACE2("CLOSE %d\n", PAGERID(pPager));
  IOTRACE(("CLOSE %p\n", pPager))
  if( pPager->journalOpen ){
    sqlite3OsClose(pPager->jfd);
  }
  sqlite3BitvecDestroy(pPager->pInJournal);

  if( pPager->stmtOpen ){
    sqlite3OsClose(pPager->stfd);
  }
  sqlite3OsClose(pPager->fd);
  /* Temp files are automatically deleted by the OS
  ** if( pPager->tempFile ){
  **   sqlite3OsDelete(pPager->zFilename);
................................................................................

    rc = sqlite3PagerPagecount(pPager, &nMax);
    if( rc!=SQLITE_OK ){
      sqlite3PagerUnref(pPg);
      return rc;
    }

    if( nMax<(int)pgno || MEMDB || (noContent && !pPager->alwaysRollback) ){
      if( pgno>pPager->mxPgno ){
        sqlite3PagerUnref(pPg);
        return SQLITE_FULL;
      }
      memset(pPg->pData, 0, pPager->pageSize);
      if( noContent && !pPager->alwaysRollback ){
        pPg->flags |= PGHDR_NEED_READ;
      }
      IOTRACE(("ZERO %p %d\n", pPager, pgno));
    }else{
      rc = readDbPage(pPager, pPg, pgno);
      if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){
        /* sqlite3PagerUnref(pPg); */
................................................................................
      }
      goto failed_to_open_journal;
    }
  }
  pPager->journalOpen = 1;
  pPager->journalStarted = 0;
  pPager->needSync = 0;
  pPager->alwaysRollback = 0;
  pPager->nRec = 0;
  if( pPager->errCode ){
    rc = pPager->errCode;
    goto failed_to_open_journal;
  }
  pPager->origDbSize = pPager->dbSize;

................................................................................
** a transaction then removed from the freelist during a later part
** of the same transaction and reused for some other purpose.  When it
** is first added to the freelist, this routine is called.  When reused,
** the sqlite3PagerDontRollback() routine is called.  But because the
** page contains critical data, we still need to be sure it gets
** rolled back in spite of the sqlite3PagerDontRollback() call.
*/
void sqlite3PagerDontWrite(DbPage *pDbPage){
  PgHdr *pPg = pDbPage;
  Pager *pPager = pPg->pPager;


  if( MEMDB ) return;
  pPg->flags |= PGHDR_ALWAYS_ROLLBACK;











  if( (pPg->flags&PGHDR_DIRTY) && !pPager->stmtInUse ){
    assert( pPager->state>=PAGER_SHARED );
    if( pPager->dbSize==(int)pPg->pgno && pPager->origDbSize<pPager->dbSize ){
      /* If this pages is the last page in the file and the file has grown
      ** during the current transaction, then do NOT mark the page as clean.
      ** When the database file grows, we must make sure that the last page
      ** gets written at least once so that the disk file will be the correct
      ** size. If you do not write this page and the size of the file
................................................................................
      IOTRACE(("CLEAN %p %d\n", pPager, pPg->pgno))
      pPg->flags |= PGHDR_DONT_WRITE;
#ifdef SQLITE_CHECK_PAGES
      pPg->pageHash = pager_pagehash(pPg);
#endif
    }
  }

}

/*
** A call to this routine tells the pager that if a rollback occurs,
** it is not necessary to restore the data on the given page.  This
** means that the pager does not have to record the given page in the
** rollback journal.
................................................................................

  assert( pPager->state>=PAGER_RESERVED );

  /* If the journal file is not open, or DontWrite() has been called on
  ** this page (DontWrite() sets the alwaysRollback flag), then this
  ** function is a no-op.
  */
  if( pPager->journalOpen==0 || (pPg->flags&PGHDR_ALWAYS_ROLLBACK) 
   || pPager->alwaysRollback 

  ){
    return;
  }
  assert( !MEMDB );    /* For a memdb, pPager->journalOpen is always 0 */

#ifdef SQLITE_SECURE_DELETE
  if( pPg->inJournal || (int)pPg->pgno > pPager->origDbSize ){
    return;
  }
#endif

  /* If SECURE_DELETE is disabled, then there is no way that this
  ** routine can be called on a page for which sqlite3PagerDontWrite()
  ** has not been previously called during the same transaction.
................................................................................
    return SQLITE_OK;
  }
  PAGERTRACE2("COMMIT %d\n", PAGERID(pPager));
  if( MEMDB ){
    sqlite3PcacheCommit(pPager->pPCache, 0);
    sqlite3PcacheCleanAll(pPager->pPCache);
    sqlite3PcacheSetFlags(pPager->pPCache, 
       ~(PGHDR_IN_JOURNAL | PGHDR_NEED_SYNC | PGHDR_ALWAYS_ROLLBACK), 0
    );
    pPager->state = PAGER_SHARED;
  }else{
    assert( pPager->state==PAGER_SYNCED || !pPager->dirtyCache );
    rc = pager_end_transaction(pPager, pPager->setMaster);
    rc = pager_error(pPager, rc);
  }
................................................................................
  int rc = SQLITE_OK;
  PAGERTRACE2("ROLLBACK %d\n", PAGERID(pPager));
  if( MEMDB ){
    sqlite3PcacheRollback(pPager->pPCache, 1);
    sqlite3PcacheRollback(pPager->pPCache, 0);
    sqlite3PcacheCleanAll(pPager->pPCache);
    sqlite3PcacheSetFlags(pPager->pPCache, 
       ~(PGHDR_IN_JOURNAL | PGHDR_NEED_SYNC | PGHDR_ALWAYS_ROLLBACK), 0
    );
    pPager->dbSize = pPager->origDbSize;
    pager_truncate_cache(pPager);
    pPager->stmtInUse = 0;
    pPager->state = PAGER_SHARED;
  }else if( !pPager->dirtyCache || !pPager->journalOpen ){
    rc = pager_end_transaction(pPager, pPager->setMaster);
................................................................................
i64 sqlite3PagerJournalSizeLimit(Pager *pPager, i64 iLimit){
  if( iLimit>=-1 ){
    pPager->journalSizeLimit = iLimit;
  }
  return pPager->journalSizeLimit;
}

void sqlite3PagerAlwaysRollback(Pager *pPager){
  pPager->alwaysRollback = 1;
}

#endif /* SQLITE_OMIT_DISKIO */

** 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 1.483 2008/08/27 15:16:34 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"

/*
** Macros for troubleshooting.  Normally turned off
*/
................................................................................
  int nExtra;                 /* Add this many bytes to each in-memory page */
  int pageSize;               /* Number of bytes in a page */
  int nPage;                  /* Total number of in-memory pages */
  int mxPage;                 /* Maximum number of pages to hold in cache */
  Pgno mxPgno;                /* Maximum allowed size of the database */
  Bitvec *pInJournal;         /* One bit for each page in the database file */
  Bitvec *pInStmt;            /* One bit for each page in the database */
  Bitvec *pAlwaysRollback;    /* One bit for each page marked always-rollback */
  char *zFilename;            /* Name of the database file */
  char *zJournal;             /* Name of the journal file */
  char *zDirectory;           /* Directory hold database and journal files */
  sqlite3_file *fd, *jfd;     /* File descriptors for database and journal */
  sqlite3_file *stfd;         /* File descriptor for the statement subjournal*/
  BusyHandler *pBusyHandler;  /* Pointer to sqlite.busyHandler */
  i64 journalOff;             /* Current byte offset in the journal file */
................................................................................
      ** delete the file out from under us.
      */
      if( pPager->journalOpen ){
        sqlite3OsClose(pPager->jfd);
        pPager->journalOpen = 0;
        sqlite3BitvecDestroy(pPager->pInJournal);
        pPager->pInJournal = 0;
        sqlite3BitvecDestroy(pPager->pAlwaysRollback);
        pPager->pAlwaysRollback = 0;
      }

      /* If Pager.errCode is set, the contents of the pager cache cannot be
      ** trusted. Now that the pager file is unlocked, the contents of the
      ** cache can be discarded and the error code safely cleared.
      */
      if( pPager->errCode ){
................................................................................
      pPager->journalOpen = 0;
      if( rc==SQLITE_OK && !pPager->tempFile ){
        rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
      }
    }
    sqlite3BitvecDestroy(pPager->pInJournal);
    pPager->pInJournal = 0;
    sqlite3BitvecDestroy(pPager->pAlwaysRollback);
    pPager->pAlwaysRollback = 0;
    sqlite3PcacheCleanAll(pPager->pPCache);
#ifdef SQLITE_CHECK_PAGES
    sqlite3PcacheIterate(pPager->pPCache, pager_set_pagehash);
#endif
    sqlite3PcacheSetFlags(pPager->pPCache,
       ~(PGHDR_IN_JOURNAL | PGHDR_NEED_SYNC), 0
    );
    pPager->dirtyCache = 0;
    pPager->nRec = 0;
  }else{
    assert( pPager->pInJournal==0 );
  }

................................................................................
  sqlite3EndBenignMalloc();
  PAGERTRACE2("CLOSE %d\n", PAGERID(pPager));
  IOTRACE(("CLOSE %p\n", pPager))
  if( pPager->journalOpen ){
    sqlite3OsClose(pPager->jfd);
  }
  sqlite3BitvecDestroy(pPager->pInJournal);
  sqlite3BitvecDestroy(pPager->pAlwaysRollback);
  if( pPager->stmtOpen ){
    sqlite3OsClose(pPager->stfd);
  }
  sqlite3OsClose(pPager->fd);
  /* Temp files are automatically deleted by the OS
  ** if( pPager->tempFile ){
  **   sqlite3OsDelete(pPager->zFilename);
................................................................................

    rc = sqlite3PagerPagecount(pPager, &nMax);
    if( rc!=SQLITE_OK ){
      sqlite3PagerUnref(pPg);
      return rc;
    }

    if( nMax<(int)pgno || MEMDB || noContent ){
      if( pgno>pPager->mxPgno ){
        sqlite3PagerUnref(pPg);
        return SQLITE_FULL;
      }
      memset(pPg->pData, 0, pPager->pageSize);
      if( noContent ){
        pPg->flags |= PGHDR_NEED_READ;
      }
      IOTRACE(("ZERO %p %d\n", pPager, pgno));
    }else{
      rc = readDbPage(pPager, pPg, pgno);
      if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){
        /* sqlite3PagerUnref(pPg); */
................................................................................
      }
      goto failed_to_open_journal;
    }
  }
  pPager->journalOpen = 1;
  pPager->journalStarted = 0;
  pPager->needSync = 0;

  pPager->nRec = 0;
  if( pPager->errCode ){
    rc = pPager->errCode;
    goto failed_to_open_journal;
  }
  pPager->origDbSize = pPager->dbSize;

................................................................................
** a transaction then removed from the freelist during a later part
** of the same transaction and reused for some other purpose.  When it
** is first added to the freelist, this routine is called.  When reused,
** the sqlite3PagerDontRollback() routine is called.  But because the
** page contains critical data, we still need to be sure it gets
** rolled back in spite of the sqlite3PagerDontRollback() call.
*/
int sqlite3PagerDontWrite(DbPage *pDbPage){
  PgHdr *pPg = pDbPage;
  Pager *pPager = pPg->pPager;
  int rc;


  if( MEMDB || pPg->pgno>pPager->origDbSize ){
    return SQLITE_OK;
  }
  if( pPager->pAlwaysRollback==0 ){
    assert( pPager->pInJournal );
    pPager->pAlwaysRollback = sqlite3BitvecCreate(pPager->origDbSize);
    if( !pPager->pAlwaysRollback ){
      return SQLITE_NOMEM;
    }
  }
  rc = sqlite3BitvecSet(pPager->pAlwaysRollback, pPg->pgno);

  if( rc==SQLITE_OK && (pPg->flags&PGHDR_DIRTY) && !pPager->stmtInUse ){
    assert( pPager->state>=PAGER_SHARED );
    if( pPager->dbSize==(int)pPg->pgno && pPager->origDbSize<pPager->dbSize ){
      /* If this pages is the last page in the file and the file has grown
      ** during the current transaction, then do NOT mark the page as clean.
      ** When the database file grows, we must make sure that the last page
      ** gets written at least once so that the disk file will be the correct
      ** size. If you do not write this page and the size of the file
................................................................................
      IOTRACE(("CLEAN %p %d\n", pPager, pPg->pgno))
      pPg->flags |= PGHDR_DONT_WRITE;
#ifdef SQLITE_CHECK_PAGES
      pPg->pageHash = pager_pagehash(pPg);
#endif
    }
  }
  return rc;
}

/*
** A call to this routine tells the pager that if a rollback occurs,
** it is not necessary to restore the data on the given page.  This
** means that the pager does not have to record the given page in the
** rollback journal.
................................................................................

  assert( pPager->state>=PAGER_RESERVED );

  /* If the journal file is not open, or DontWrite() has been called on
  ** this page (DontWrite() sets the alwaysRollback flag), then this
  ** function is a no-op.
  */
  if( pPager->journalOpen==0 
   || sqlite3BitvecTest(pPager->pAlwaysRollback, pPg->pgno)
   || pPg->pgno>pPager->origDbSize
  ){
    return;
  }
  assert( !MEMDB );    /* For a memdb, pPager->journalOpen is always 0 */

#ifdef SQLITE_SECURE_DELETE
  if( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize ){
    return;
  }
#endif

  /* If SECURE_DELETE is disabled, then there is no way that this
  ** routine can be called on a page for which sqlite3PagerDontWrite()
  ** has not been previously called during the same transaction.
................................................................................
    return SQLITE_OK;
  }
  PAGERTRACE2("COMMIT %d\n", PAGERID(pPager));
  if( MEMDB ){
    sqlite3PcacheCommit(pPager->pPCache, 0);
    sqlite3PcacheCleanAll(pPager->pPCache);
    sqlite3PcacheSetFlags(pPager->pPCache, 
       ~(PGHDR_IN_JOURNAL | PGHDR_NEED_SYNC), 0
    );
    pPager->state = PAGER_SHARED;
  }else{
    assert( pPager->state==PAGER_SYNCED || !pPager->dirtyCache );
    rc = pager_end_transaction(pPager, pPager->setMaster);
    rc = pager_error(pPager, rc);
  }
................................................................................
  int rc = SQLITE_OK;
  PAGERTRACE2("ROLLBACK %d\n", PAGERID(pPager));
  if( MEMDB ){
    sqlite3PcacheRollback(pPager->pPCache, 1);
    sqlite3PcacheRollback(pPager->pPCache, 0);
    sqlite3PcacheCleanAll(pPager->pPCache);
    sqlite3PcacheSetFlags(pPager->pPCache, 
       ~(PGHDR_IN_JOURNAL | PGHDR_NEED_SYNC), 0
    );
    pPager->dbSize = pPager->origDbSize;
    pager_truncate_cache(pPager);
    pPager->stmtInUse = 0;
    pPager->state = PAGER_SHARED;
  }else if( !pPager->dirtyCache || !pPager->journalOpen ){
    rc = pager_end_transaction(pPager, pPager->setMaster);
................................................................................
i64 sqlite3PagerJournalSizeLimit(Pager *pPager, i64 iLimit){
  if( iLimit>=-1 ){
    pPager->journalSizeLimit = iLimit;
  }
  return pPager->journalSizeLimit;
}





#endif /* SQLITE_OMIT_DISKIO */

**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite page cache
** subsystem.  The page cache subsystem reads and writes a file a page
** at a time and provides a journal for rollback.
**
** @(#) $Id: pager.h,v 1.80 2008/08/22 17:34:45 drh Exp $
*/

#ifndef _PAGER_H_
#define _PAGER_H_

/*
** If defined as non-zero, auto-vacuum is enabled by default. Otherwise
................................................................................
int sqlite3PagerCommitPhaseTwo(Pager*);
int sqlite3PagerRollback(Pager*);
int sqlite3PagerIsreadonly(Pager*);
int sqlite3PagerStmtBegin(Pager*);
int sqlite3PagerStmtCommit(Pager*);
int sqlite3PagerStmtRollback(Pager*);
void sqlite3PagerDontRollback(DbPage*);
void sqlite3PagerDontWrite(DbPage*);
int sqlite3PagerRefcount(Pager*);
void sqlite3PagerSetSafetyLevel(Pager*,int,int);
const char *sqlite3PagerFilename(Pager*);
const sqlite3_vfs *sqlite3PagerVfs(Pager*);
sqlite3_file *sqlite3PagerFile(Pager*);
const char *sqlite3PagerDirname(Pager*);
const char *sqlite3PagerJournalname(Pager*);

**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite page cache
** subsystem.  The page cache subsystem reads and writes a file a page
** at a time and provides a journal for rollback.
**
** @(#) $Id: pager.h,v 1.81 2008/08/27 15:16:34 danielk1977 Exp $
*/

#ifndef _PAGER_H_
#define _PAGER_H_

/*
** If defined as non-zero, auto-vacuum is enabled by default. Otherwise
................................................................................
int sqlite3PagerCommitPhaseTwo(Pager*);
int sqlite3PagerRollback(Pager*);
int sqlite3PagerIsreadonly(Pager*);
int sqlite3PagerStmtBegin(Pager*);
int sqlite3PagerStmtCommit(Pager*);
int sqlite3PagerStmtRollback(Pager*);
void sqlite3PagerDontRollback(DbPage*);
int sqlite3PagerDontWrite(DbPage*);
int sqlite3PagerRefcount(Pager*);
void sqlite3PagerSetSafetyLevel(Pager*,int,int);
const char *sqlite3PagerFilename(Pager*);
const sqlite3_vfs *sqlite3PagerVfs(Pager*);
sqlite3_file *sqlite3PagerFile(Pager*);
const char *sqlite3PagerDirname(Pager*);
const char *sqlite3PagerJournalname(Pager*);

**    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.
**
*************************************************************************
** This file implements that page cache.
**
** @(#) $Id: pcache.c,v 1.16 2008/08/27 09:44:40 danielk1977 Exp $
*/
#include "sqliteInt.h"

/*
** A complete page cache is an instance of this structure.
*/
struct PCache {
................................................................................
  assert( sqlite3_mutex_held(pcache.mutex) );

  if( (p=pcache.pLruTail) ){
    assert( (p->flags&PGHDR_DIRTY)==0 );
    pcacheRemoveFromLruList(p);
    pcacheRemoveFromHash(p);
    pcacheRemoveFromList(&p->pCache->pClean, p);

    /* If the always-rollback flag is set on the page being recycled, set 
    ** the always-rollback flag on the corresponding pager. TODO: This is
    ** a thread-safety problem.
    */
    if( p->flags&PGHDR_ALWAYS_ROLLBACK ){
      assert(p->pPager);
      sqlite3PagerAlwaysRollback(p->pPager);
    }
  }

  return p;
}

/*
** Obtain space for a page. Try to recycle an old page if the limit on the 

**    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.
**
*************************************************************************
** This file implements that page cache.
**
** @(#) $Id: pcache.c,v 1.17 2008/08/27 15:16:34 danielk1977 Exp $
*/
#include "sqliteInt.h"

/*
** A complete page cache is an instance of this structure.
*/
struct PCache {
................................................................................
  assert( sqlite3_mutex_held(pcache.mutex) );

  if( (p=pcache.pLruTail) ){
    assert( (p->flags&PGHDR_DIRTY)==0 );
    pcacheRemoveFromLruList(p);
    pcacheRemoveFromHash(p);
    pcacheRemoveFromList(&p->pCache->pClean, p);









  }

  return p;
}

/*
** Obtain space for a page. Try to recycle an old page if the limit on the 

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite page cache
** subsystem. 
**
** @(#) $Id: pcache.h,v 1.6 2008/08/26 18:05:48 danielk1977 Exp $
*/

#ifndef _PCACHE_H_

typedef struct PgHdr PgHdr;
typedef struct PCache PCache;

................................................................................
};

/* Bit values for PgHdr.flags */
#define PGHDR_IN_JOURNAL        0x001  /* Page is in rollback journal */
#define PGHDR_IN_STMTJRNL       0x002  /* Page is in the statement journal */
#define PGHDR_DIRTY             0x004  /* Page has changed */
#define PGHDR_NEED_SYNC         0x008  /* Peed to fsync this page */
#define PGHDR_ALWAYS_ROLLBACK   0x010  /* Force writing to journal */
#define PGHDR_NEED_READ         0x020  /* Content is unread */
#define PGHDR_IS_INIT           0x040  /* pData is initialized */
#define PGHDR_REUSE_UNLIKELY    0x080  /* Hint: Reuse is unlikely */
#define PGHDR_DONT_WRITE        0x100  /* Do not write content to disk */

/* Initialize and shutdown the page cache subsystem */
int sqlite3PcacheInitialize(void);

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite page cache
** subsystem. 
**
** @(#) $Id: pcache.h,v 1.7 2008/08/27 15:16:34 danielk1977 Exp $
*/

#ifndef _PCACHE_H_

typedef struct PgHdr PgHdr;
typedef struct PCache PCache;

................................................................................
};

/* Bit values for PgHdr.flags */
#define PGHDR_IN_JOURNAL        0x001  /* Page is in rollback journal */
#define PGHDR_IN_STMTJRNL       0x002  /* Page is in the statement journal */
#define PGHDR_DIRTY             0x004  /* Page has changed */
#define PGHDR_NEED_SYNC         0x008  /* Peed to fsync this page */

#define PGHDR_NEED_READ         0x020  /* Content is unread */
#define PGHDR_IS_INIT           0x040  /* pData is initialized */
#define PGHDR_REUSE_UNLIKELY    0x080  /* Hint: Reuse is unlikely */
#define PGHDR_DONT_WRITE        0x100  /* Do not write content to disk */

/* Initialize and shutdown the page cache subsystem */
int sqlite3PcacheInitialize(void);