**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
******************************************************************************
**
** This file contains code that is specific to Unix systems.
**
** $Id: os_unix.c,v 1.203 2008/09/23 10:23:26 drh Exp $
*/
#include "sqliteInt.h"
#if SQLITE_OS_UNIX              /* This file is used on unix only */

/*
** If SQLITE_ENABLE_LOCKING_STYLE is defined and is non-zero, then several
** alternative locking implementations are provided:
................................................................................
** a normal expected return code of SQLITE_BUSY or SQLITE_OK
*/
#define IS_LOCK_ERROR(x)  ((x != SQLITE_OK) && (x != SQLITE_BUSY))

/*
** Helper functions to obtain and relinquish the global mutex.
*/
static void enterMutex(){
  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
}
static void leaveMutex(){
  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
}

#if SQLITE_THREADSAFE
/*
** This variable records whether or not threads can override each others
** locks.

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
******************************************************************************
**
** This file contains code that is specific to Unix systems.
**
** $Id: os_unix.c,v 1.204 2008/09/24 09:12:47 danielk1977 Exp $
*/
#include "sqliteInt.h"
#if SQLITE_OS_UNIX              /* This file is used on unix only */

/*
** If SQLITE_ENABLE_LOCKING_STYLE is defined and is non-zero, then several
** alternative locking implementations are provided:
................................................................................
** a normal expected return code of SQLITE_BUSY or SQLITE_OK
*/
#define IS_LOCK_ERROR(x)  ((x != SQLITE_OK) && (x != SQLITE_BUSY))

/*
** Helper functions to obtain and relinquish the global mutex.
*/
static void enterMutex(void){
  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
}
static void leaveMutex(void){
  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
}

#if SQLITE_THREADSAFE
/*
** This variable records whether or not threads can override each others
** locks.

**    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 1.31 2008/09/21 15:14:04 drh Exp $
*/
#include "sqliteInt.h"

/*
** A complete page cache is an instance of this structure.
**
** A cache may only be deleted by its owner and while holding the
................................................................................
** This function removes page pcache.pLruTail from the global LRU list,
** and from the hash-table and PCache.pClean list of the owner pcache.
** There should be no other references to the page.
**
** A pointer to the recycled page is returned, or NULL if no page is
** eligible for recycling.
*/
static PgHdr *pcacheRecyclePage(){
  PgHdr *p = 0;
  assert( sqlite3_mutex_held(pcache_g.mutex) );

  if( (p=pcache_g.pLruTail) ){
    assert( (p->flags&PGHDR_DIRTY)==0 );
    pcacheRemoveFromLruList(p);
    pcacheRemoveFromHash(p);
................................................................................
  pcacheExitMutex();
}

/*
** If there are currently more than pcache.nMaxPage pages allocated, try
** to recycle pages to reduce the number allocated to pcache.nMaxPage.
*/
static void pcacheEnforceMaxPage(){
  PgHdr *p;
  assert( sqlite3_mutex_held(pcache_g.mutex) );
  while( pcache_g.nCurrentPage>pcache_g.nMaxPage && (p = pcacheRecyclePage()) ){
    pcachePageFree(p);
  }
}

**    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 1.32 2008/09/24 09:12:47 danielk1977 Exp $
*/
#include "sqliteInt.h"

/*
** A complete page cache is an instance of this structure.
**
** A cache may only be deleted by its owner and while holding the
................................................................................
** This function removes page pcache.pLruTail from the global LRU list,
** and from the hash-table and PCache.pClean list of the owner pcache.
** There should be no other references to the page.
**
** A pointer to the recycled page is returned, or NULL if no page is
** eligible for recycling.
*/
static PgHdr *pcacheRecyclePage(void){
  PgHdr *p = 0;
  assert( sqlite3_mutex_held(pcache_g.mutex) );

  if( (p=pcache_g.pLruTail) ){
    assert( (p->flags&PGHDR_DIRTY)==0 );
    pcacheRemoveFromLruList(p);
    pcacheRemoveFromHash(p);
................................................................................
  pcacheExitMutex();
}

/*
** If there are currently more than pcache.nMaxPage pages allocated, try
** to recycle pages to reduce the number allocated to pcache.nMaxPage.
*/
static void pcacheEnforceMaxPage(void){
  PgHdr *p;
  assert( sqlite3_mutex_held(pcache_g.mutex) );
  while( pcache_g.nCurrentPage>pcache_g.nMaxPage && (p = pcacheRecyclePage()) ){
    pcachePageFree(p);
  }
}

#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is database locks.
#
# $Id: lock5.test,v 1.2 2008/07/12 14:52:20 drh Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

# This file is only run if using the unix backend compiled with the
# SQLITE_ENABLE_LOCKING_STYLE macro.
db close
if {[catch {sqlite3 db test.db -vfs unix-none} msg]} {
puts $msg
  finish_test
  return
}
db close

do_test lock5-dotfile.1 {
  sqlite3 db test.db -vfs unix-dotfile

#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is database locks.
#
# $Id: lock5.test,v 1.3 2008/09/24 09:12:47 danielk1977 Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

# This file is only run if using the unix backend compiled with the
# SQLITE_ENABLE_LOCKING_STYLE macro.
db close
if {[catch {sqlite3 db test.db -vfs unix-none} msg]} {

  finish_test
  return
}
db close

do_test lock5-dotfile.1 {
  sqlite3 db test.db -vfs unix-dotfile