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<?php
/**
* Data caching with dependencies.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
* @ingroup Cache
*/
/**
* This class stores an arbitrary value along with its dependencies.
* Users should typically only use DependencyWrapper::getValueFromCache(),
* rather than instantiating one of these objects directly.
* @ingroup Cache
*/
class DependencyWrapper {
var $value;
var $deps;
/**
* Create an instance.
* @param $value Mixed: the user-supplied value
* @param $deps Mixed: a dependency or dependency array. All dependencies
* must be objects implementing CacheDependency.
*/
function __construct( $value = false, $deps = array() ) {
$this->value = $value;
if ( !is_array( $deps ) ) {
$deps = array( $deps );
}
$this->deps = $deps;
}
/**
* Returns true if any of the dependencies have expired
*
* @return bool
*/
function isExpired() {
foreach ( $this->deps as $dep ) {
if ( $dep->isExpired() ) {
return true;
}
}
return false;
}
/**
* Initialise dependency values in preparation for storing. This must be
* called before serialization.
*/
function initialiseDeps() {
foreach ( $this->deps as $dep ) {
$dep->loadDependencyValues();
}
}
/**
* Get the user-defined value
* @return bool|Mixed
*/
function getValue() {
return $this->value;
}
/**
* Store the wrapper to a cache
*
* @param $cache BagOStuff
* @param $key
* @param $expiry
*/
function storeToCache( $cache, $key, $expiry = 0 ) {
$this->initialiseDeps();
$cache->set( $key, $this, $expiry );
}
/**
* Attempt to get a value from the cache. If the value is expired or missing,
* it will be generated with the callback function (if present), and the newly
* calculated value will be stored to the cache in a wrapper.
*
* @param $cache BagOStuff a cache object such as $wgMemc
* @param string $key the cache key
* @param $expiry Integer: the expiry timestamp or interval in seconds
* @param $callback Mixed: the callback for generating the value, or false
* @param array $callbackParams the function parameters for the callback
* @param array $deps the dependencies to store on a cache miss. Note: these
* are not the dependencies used on a cache hit! Cache hits use the stored
* dependency array.
*
* @return mixed The value, or null if it was not present in the cache and no
* callback was defined.
*/
static function getValueFromCache( $cache, $key, $expiry = 0, $callback = false,
$callbackParams = array(), $deps = array() )
{
$obj = $cache->get( $key );
if ( is_object( $obj ) && $obj instanceof DependencyWrapper && !$obj->isExpired() ) {
$value = $obj->value;
} elseif ( $callback ) {
$value = call_user_func_array( $callback, $callbackParams );
# Cache the newly-generated value
$wrapper = new DependencyWrapper( $value, $deps );
$wrapper->storeToCache( $cache, $key, $expiry );
} else {
$value = null;
}
return $value;
}
}
/**
* @ingroup Cache
*/
abstract class CacheDependency {
/**
* Returns true if the dependency is expired, false otherwise
*/
abstract function isExpired();
/**
* Hook to perform any expensive pre-serialize loading of dependency values.
*/
function loadDependencyValues() { }
}
/**
* @ingroup Cache
*/
class FileDependency extends CacheDependency {
var $filename, $timestamp;
/**
* Create a file dependency
*
* @param string $filename the name of the file, preferably fully qualified
* @param $timestamp Mixed: the unix last modified timestamp, or false if the
* file does not exist. If omitted, the timestamp will be loaded from
* the file.
*
* A dependency on a nonexistent file will be triggered when the file is
* created. A dependency on an existing file will be triggered when the
* file is changed.
*/
function __construct( $filename, $timestamp = null ) {
$this->filename = $filename;
$this->timestamp = $timestamp;
}
/**
* @return array
*/
function __sleep() {
$this->loadDependencyValues();
return array( 'filename', 'timestamp' );
}
function loadDependencyValues() {
if ( is_null( $this->timestamp ) ) {
if ( !file_exists( $this->filename ) ) {
# Dependency on a non-existent file
# This is a valid concept!
$this->timestamp = false;
} else {
$this->timestamp = filemtime( $this->filename );
}
}
}
/**
* @return bool
*/
function isExpired() {
if ( !file_exists( $this->filename ) ) {
if ( $this->timestamp === false ) {
# Still nonexistent
return false;
} else {
# Deleted
wfDebug( "Dependency triggered: {$this->filename} deleted.\n" );
return true;
}
} else {
$lastmod = filemtime( $this->filename );
if ( $lastmod > $this->timestamp ) {
# Modified or created
wfDebug( "Dependency triggered: {$this->filename} changed.\n" );
return true;
} else {
# Not modified
return false;
}
}
}
}
/**
* @ingroup Cache
*/
class TitleDependency extends CacheDependency {
var $titleObj;
var $ns, $dbk;
var $touched;
/**
* Construct a title dependency
* @param $title Title
*/
function __construct( Title $title ) {
$this->titleObj = $title;
$this->ns = $title->getNamespace();
$this->dbk = $title->getDBkey();
}
function loadDependencyValues() {
$this->touched = $this->getTitle()->getTouched();
}
/**
* Get rid of bulky Title object for sleep
*
* @return array
*/
function __sleep() {
return array( 'ns', 'dbk', 'touched' );
}
/**
* @return Title
*/
function getTitle() {
if ( !isset( $this->titleObj ) ) {
$this->titleObj = Title::makeTitle( $this->ns, $this->dbk );
}
return $this->titleObj;
}
/**
* @return bool
*/
function isExpired() {
$touched = $this->getTitle()->getTouched();
if ( $this->touched === false ) {
if ( $touched === false ) {
# Still missing
return false;
} else {
# Created
return true;
}
} elseif ( $touched === false ) {
# Deleted
return true;
} elseif ( $touched > $this->touched ) {
# Updated
return true;
} else {
# Unmodified
return false;
}
}
}
/**
* @ingroup Cache
*/
class TitleListDependency extends CacheDependency {
var $linkBatch;
var $timestamps;
/**
* Construct a dependency on a list of titles
* @param $linkBatch LinkBatch
*/
function __construct( LinkBatch $linkBatch ) {
$this->linkBatch = $linkBatch;
}
/**
* @return array
*/
function calculateTimestamps() {
# Initialise values to false
$timestamps = array();
foreach ( $this->getLinkBatch()->data as $ns => $dbks ) {
if ( count( $dbks ) > 0 ) {
$timestamps[$ns] = array();
foreach ( $dbks as $dbk => $value ) {
$timestamps[$ns][$dbk] = false;
}
}
}
# Do the query
if ( count( $timestamps ) ) {
$dbr = wfGetDB( DB_SLAVE );
$where = $this->getLinkBatch()->constructSet( 'page', $dbr );
$res = $dbr->select(
'page',
array( 'page_namespace', 'page_title', 'page_touched' ),
$where,
__METHOD__
);
foreach ( $res as $row ) {
$timestamps[$row->page_namespace][$row->page_title] = $row->page_touched;
}
}
return $timestamps;
}
function loadDependencyValues() {
$this->timestamps = $this->calculateTimestamps();
}
/**
* @return array
*/
function __sleep() {
return array( 'timestamps' );
}
/**
* @return LinkBatch
*/
function getLinkBatch() {
if ( !isset( $this->linkBatch ) ) {
$this->linkBatch = new LinkBatch;
$this->linkBatch->setArray( $this->timestamps );
}
return $this->linkBatch;
}
/**
* @return bool
*/
function isExpired() {
$newTimestamps = $this->calculateTimestamps();
foreach ( $this->timestamps as $ns => $dbks ) {
foreach ( $dbks as $dbk => $oldTimestamp ) {
$newTimestamp = $newTimestamps[$ns][$dbk];
if ( $oldTimestamp === false ) {
if ( $newTimestamp === false ) {
# Still missing
} else {
# Created
return true;
}
} elseif ( $newTimestamp === false ) {
# Deleted
return true;
} elseif ( $newTimestamp > $oldTimestamp ) {
# Updated
return true;
} else {
# Unmodified
}
}
}
return false;
}
}
/**
* @ingroup Cache
*/
class GlobalDependency extends CacheDependency {
var $name, $value;
function __construct( $name ) {
$this->name = $name;
$this->value = $GLOBALS[$name];
}
/**
* @return bool
*/
function isExpired() {
if( !isset( $GLOBALS[$this->name] ) ) {
return true;
}
return $GLOBALS[$this->name] != $this->value;
}
}
/**
* @ingroup Cache
*/
class ConstantDependency extends CacheDependency {
var $name, $value;
function __construct( $name ) {
$this->name = $name;
$this->value = constant( $name );
}
/**
* @return bool
*/
function isExpired() {
return constant( $this->name ) != $this->value;
}
}