1 files changed, 328 insertions, 0 deletions
diff --git a/includes/CacheDependency.php b/includes/CacheDependency.php
new file mode 100644
index 00000000..4bb3d328
--- /dev/null
+++ b/includes/CacheDependency.php
@@ -0,0 +1,328 @@
+<?php
+
+/**
+ * This class stores an arbitrary value along with its dependencies. 
+ * Users should typically only use DependencyWrapper::getFromCache(), rather
+ * than instantiating one of these objects directly.
+ */
+class DependencyWrapper {
+	var $value;
+	var $deps;
+
+	/**
+	 * Create an instance.
+	 * @param mixed $value The user-supplied value
+	 * @param mixed $deps 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
+	 */
+	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
+	 */
+	function getValue() {
+		return $this->value;
+	}
+
+	/**
+	 * Store the wrapper to a cache
+	 */
+	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 object $cache A cache object such as $wgMemc
+	 * @param string $key The cache key
+	 * @param integer $expiry The expiry timestamp or interval in seconds
+	 * @param mixed $callback 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;
+	}
+}
+
+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() {}
+}
+
+class FileDependency extends CacheDependency {
+	var $filename, $timestamp;
+
+	/**
+	 * Create a file dependency
+	 *
+	 * @param string $filename The name of the file, preferably fully qualified
+	 * @param mixed $timestamp 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;
+	}
+
+	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 );
+			}
+		}
+	}
+
+	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;
+			}
+		}
+	}
+}
+
+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
+	 */
+	function __sleep() {
+		return array( 'ns', 'dbk', 'touched' );
+	}
+
+	function getTitle() {
+		if ( !isset( $this->titleObj ) ) {
+			$this->titleObj = Title::makeTitle( $this->ns, $this->dbk );
+		} 
+		return $this->titleObj;
+	}
+
+	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;
+		}
+	}
+}
+
+class TitleListDependency extends CacheDependency {
+	var $linkBatch;
+	var $timestamps;
+	
+	/**
+	 * Construct a dependency on a list of titles
+	 */
+	function __construct( LinkBatch $linkBatch ) {
+		$this->linkBatch = $linkBatch;
+	}
+
+	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__ );
+			while ( $row = $dbr->fetchObject( $res ) ) {
+				$timestamps[$row->page_namespace][$row->page_title] = $row->page_touched;
+			}
+		}
+		return $timestamps;
+	}
+
+	function loadDependencyValues() {
+		$this->timestamps = $this->calculateTimestamps();
+	}
+
+	function __sleep() {
+		return array( 'timestamps' );
+	}
+
+	function getLinkBatch() {
+		if ( !isset( $this->linkBatch ) ){
+			$this->linkBatch = new LinkBatch;
+			$this->linkBatch->setArray( $this->timestamps );
+		}
+		return $this->linkBatch;
+	}
+
+	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;
+	}
+}
+
+class GlobalDependency extends CacheDependency {
+	var $name, $value;
+	
+	function __construct( $name ) {
+		$this->name = $name;
+		$this->value = $GLOBALS[$name];
+	}
+
+	function isExpired() {
+		return $GLOBALS[$this->name] != $this->value;
+	}
+}
+
+class ConstantDependency extends CacheDependency {
+	var $name, $value;
+
+	function __construct( $name ) {
+		$this->name = $name;
+		$this->value = constant( $name );
+	}
+
+	function isExpired() {
+		return constant( $this->name ) != $this->value;
+	}
+}
+
+?>