CacheDependency.php

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<?php
class DependencyWrapper {
        var $value;
        var $deps;

        function __construct( $value = false, $deps = array() ) {
                $this->value = $value;

                if ( !is_array( $deps ) ) {
                        $deps = array( $deps );
                }

                $this->deps = $deps;
        }

        function isExpired() {
                foreach ( $this->deps as $dep ) {
                        if ( $dep->isExpired() ) {
                                return true;
                        }
                }

                return false;
        }

        function initialiseDeps() {
                foreach ( $this->deps as $dep ) {
                        $dep->loadDependencyValues();
                }
        }

        function getValue() {
                return $this->value;
        }

        function storeToCache( $cache, $key, $expiry = 0 ) {
                $this->initialiseDeps();
                $cache->set( $key, $this, $expiry );
        }

        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 {
        abstract function isExpired();

        function loadDependencyValues() { }
}

class FileDependency extends CacheDependency {
        var $filename, $timestamp;

        function __construct( $filename, $timestamp = null ) {
                $this->filename = $filename;
                $this->timestamp = $timestamp;
        }

        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 );
                        }
                }
        }

        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;

        function __construct( Title $title ) {
                $this->titleObj = $title;
                $this->ns = $title->getNamespace();
                $this->dbk = $title->getDBkey();
        }

        function loadDependencyValues() {
                $this->touched = $this->getTitle()->getTouched();
        }

        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;

        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__
                        );

                        foreach ( $res as $row ) {
                                $timestamps[$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() {
                if( !isset($GLOBALS[$this->name]) ) {
                        return true;
                }
                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;
        }
}