Removed raw Article->field accessing

[mediawiki.git] / includes / LocalisationCache.php

<?php

define( 'MW_LC_VERSION', 1 );

/**
 * Class for caching the contents of localisation files, Messages*.php
 * and *.i18n.php.
 *
 * An instance of this class is available using Language::getLocalisationCache().
 *
 * The values retrieved from here are merged, containing items from extension
 * files, core messages files and the language fallback sequence (e.g. zh-cn ->
 * zh-hans -> en ). Some common errors are corrected, for example namespace
 * names with spaces instead of underscores, but heavyweight processing, such
 * as grammatical transformation, is done by the caller.
 */
class LocalisationCache {
        /** Configuration associative array */
        var $conf;

        /**
         * True if recaching should only be done on an explicit call to recache().
         * Setting this reduces the overhead of cache freshness checking, which
         * requires doing a stat() for every extension i18n file.
         */
        var $manualRecache = false;

        /**
         * True to treat all files as expired until they are regenerated by this object.
         */
        var $forceRecache = false;

        /**
         * The cache data. 3-d array, where the first key is the language code,
         * the second key is the item key e.g. 'messages', and the third key is
         * an item specific subkey index. Some items are not arrays and so for those
         * items, there are no subkeys.
         */
        var $data = array();

        /**
         * The persistent store object. An instance of LCStore.
         */
        var $store;

        /**
         * A 2-d associative array, code/key, where presence indicates that the item
         * is loaded. Value arbitrary.
         *
         * For split items, if set, this indicates that all of the subitems have been
         * loaded.
         */
        var $loadedItems = array();

        /**
         * A 3-d associative array, code/key/subkey, where presence indicates that
         * the subitem is loaded. Only used for the split items, i.e. messages.
         */
        var $loadedSubitems = array();

        /**
         * An array where presence of a key indicates that that language has been
         * initialised. Initialisation includes checking for cache expiry and doing
         * any necessary updates.
         */
        var $initialisedLangs = array();

        /**
         * An array mapping non-existent pseudo-languages to fallback languages. This
         * is filled by initShallowFallback() when data is requested from a language
         * that lacks a Messages*.php file.
         */
        var $shallowFallbacks = array();

        /**
         * An array where the keys are codes that have been recached by this instance.
         */
        var $recachedLangs = array();

        /**
         * All item keys
         */
        static public $allKeys = array(
                'fallback', 'namespaceNames', 'bookstoreList',
                'magicWords', 'messages', 'rtl', 'capitalizeAllNouns', 'digitTransformTable',
                'separatorTransformTable', 'fallback8bitEncoding', 'linkPrefixExtension',
                'defaultUserOptionOverrides', 'linkTrail', 'namespaceAliases',
                'dateFormats', 'datePreferences', 'datePreferenceMigrationMap',
                'defaultDateFormat', 'extraUserToggles', 'specialPageAliases',
                'imageFiles', 'preloadedMessages', 'namespaceGenderAliases',
        );

        /**
         * Keys for items which consist of associative arrays, which may be merged
         * by a fallback sequence.
         */
        static public $mergeableMapKeys = array( 'messages', 'namespaceNames',
                'dateFormats', 'defaultUserOptionOverrides', 'imageFiles',
                'preloadedMessages',
        );

        /**
         * Keys for items which are a numbered array.
         */
        static public $mergeableListKeys = array( 'extraUserToggles' );

        /**
         * Keys for items which contain an array of arrays of equivalent aliases
         * for each subitem. The aliases may be merged by a fallback sequence.
         */
        static public $mergeableAliasListKeys = array( 'specialPageAliases' );

        /**
         * Keys for items which contain an associative array, and may be merged if
         * the primary value contains the special array key "inherit". That array
         * key is removed after the first merge.
         */
        static public $optionalMergeKeys = array( 'bookstoreList' );

        /**
         * Keys for items that are formatted like $magicWords
         */
        static public $magicWordKeys = array( 'magicWords' );

        /**
         * Keys for items where the subitems are stored in the backend separately.
         */
        static public $splitKeys = array( 'messages' );

        /**
         * Keys which are loaded automatically by initLanguage()
         */
        static public $preloadedKeys = array( 'dateFormats', 'namespaceNames',
                'defaultUserOptionOverrides' );

        /**
         * Constructor.
         * For constructor parameters, see the documentation in DefaultSettings.php
         * for $wgLocalisationCacheConf.
         *
         * @param $conf Array
         */
        function __construct( $conf ) {
                global $wgCacheDirectory;

                $this->conf = $conf;
                $storeConf = array();
                if ( !empty( $conf['storeClass'] ) ) {
                        $storeClass = $conf['storeClass'];
                } else {
                        switch ( $conf['store'] ) {
                                case 'files':
                                case 'file':
                                        $storeClass = 'LCStore_CDB';
                                        break;
                                case 'db':
                                        $storeClass = 'LCStore_DB';
                                        break;
                                case 'detect':
                                        $storeClass = $wgCacheDirectory ? 'LCStore_CDB' : 'LCStore_DB';
                                        break;
                                default:
                                        throw new MWException(
                                                'Please set $wgLocalisationCacheConf[\'store\'] to something sensible.' );
                        }
                }

                wfDebug( get_class( $this ) . ": using store $storeClass\n" );
                if ( !empty( $conf['storeDirectory'] ) ) {
                        $storeConf['directory'] = $conf['storeDirectory'];
                }

                $this->store = new $storeClass( $storeConf );
                foreach ( array( 'manualRecache', 'forceRecache' ) as $var ) {
                        if ( isset( $conf[$var] ) ) {
                                $this->$var = $conf[$var];
                        }
                }
        }

        /**
         * Returns true if the given key is mergeable, that is, if it is an associative
         * array which can be merged through a fallback sequence.
         */
        public function isMergeableKey( $key ) {
                if ( !isset( $this->mergeableKeys ) ) {
                        $this->mergeableKeys = array_flip( array_merge(
                                self::$mergeableMapKeys,
                                self::$mergeableListKeys,
                                self::$mergeableAliasListKeys,
                                self::$optionalMergeKeys,
                                self::$magicWordKeys
                        ) );
                }
                return isset( $this->mergeableKeys[$key] );
        }

        /**
         * Get a cache item.
         *
         * Warning: this may be slow for split items (messages), since it will
         * need to fetch all of the subitems from the cache individually.
         */
        public function getItem( $code, $key ) {
                if ( !isset( $this->loadedItems[$code][$key] ) ) {
                        wfProfileIn( __METHOD__.'-load' );
                        $this->loadItem( $code, $key );
                        wfProfileOut( __METHOD__.'-load' );
                }
                if ( $key === 'fallback' && isset( $this->shallowFallbacks[$code] ) ) {
                        return $this->shallowFallbacks[$code];
                }
                return $this->data[$code][$key];
        }

        /**
         * Get a subitem, for instance a single message for a given language.
         */
        public function getSubitem( $code, $key, $subkey ) {
                if ( !isset( $this->loadedSubitems[$code][$key][$subkey] )
                        && !isset( $this->loadedItems[$code][$key] ) )
                {
                        wfProfileIn( __METHOD__.'-load' );
                        $this->loadSubitem( $code, $key, $subkey );
                        wfProfileOut( __METHOD__.'-load' );
                }
                if ( isset( $this->data[$code][$key][$subkey] ) ) {
                        return $this->data[$code][$key][$subkey];
                } else {
                        return null;
                }
        }

        /**
         * Get the list of subitem keys for a given item.
         *
         * This is faster than array_keys($lc->getItem(...)) for the items listed in
         * self::$splitKeys.
         *
         * Will return null if the item is not found, or false if the item is not an
         * array.
         */
        public function getSubitemList( $code, $key ) {
                if ( in_array( $key, self::$splitKeys ) ) {
                        return $this->getSubitem( $code, 'list', $key );
                } else {
                        $item = $this->getItem( $code, $key );
                        if ( is_array( $item ) ) {
                                return array_keys( $item );
                        } else {
                                return false;
                        }
                }
        }

        /**
         * Load an item into the cache.
         */
        protected function loadItem( $code, $key ) {
                if ( !isset( $this->initialisedLangs[$code] ) ) {
                        $this->initLanguage( $code );
                }
                // Check to see if initLanguage() loaded it for us
                if ( isset( $this->loadedItems[$code][$key] ) ) {
                        return;
                }
                if ( isset( $this->shallowFallbacks[$code] ) ) {
                        $this->loadItem( $this->shallowFallbacks[$code], $key );
                        return;
                }
                if ( in_array( $key, self::$splitKeys ) ) {
                        $subkeyList = $this->getSubitem( $code, 'list', $key );
                        foreach ( $subkeyList as $subkey ) {
                                if ( isset( $this->data[$code][$key][$subkey] ) ) {
                                        continue;
                                }
                                $this->data[$code][$key][$subkey] = $this->getSubitem( $code, $key, $subkey );
                        }
                } else {
                        $this->data[$code][$key] = $this->store->get( $code, $key );
                }
                $this->loadedItems[$code][$key] = true;
        }

        /**
         * Load a subitem into the cache
         */
        protected function loadSubitem( $code, $key, $subkey ) {
                if ( !in_array( $key, self::$splitKeys ) ) {
                        $this->loadItem( $code, $key );
                        return;
                }
                if ( !isset( $this->initialisedLangs[$code] ) ) {
                        $this->initLanguage( $code );
                }
                // Check to see if initLanguage() loaded it for us
                if ( isset( $this->loadedItems[$code][$key] )
                        || isset( $this->loadedSubitems[$code][$key][$subkey] ) )
                {
                        return;
                }
                if ( isset( $this->shallowFallbacks[$code] ) ) {
                        $this->loadSubitem( $this->shallowFallbacks[$code], $key, $subkey );
                        return;
                }
                $value = $this->store->get( $code, "$key:$subkey" );
                $this->data[$code][$key][$subkey] = $value;
                $this->loadedSubitems[$code][$key][$subkey] = true;
        }

        /**
         * Returns true if the cache identified by $code is missing or expired.
         */
        public function isExpired( $code ) {
                if ( $this->forceRecache && !isset( $this->recachedLangs[$code] ) ) {
                        wfDebug( __METHOD__."($code): forced reload\n" );
                        return true;
                }

                $deps = $this->store->get( $code, 'deps' );
                if ( $deps === null ) {
                        wfDebug( __METHOD__."($code): cache missing, need to make one\n" );
                        return true;
                }
                foreach ( $deps as $dep ) {
                        // Because we're unserializing stuff from cache, we
                        // could receive objects of classes that don't exist
                        // anymore (e.g. uninstalled extensions)
                        // When this happens, always expire the cache
                        if ( !$dep instanceof CacheDependency || $dep->isExpired() ) {
                                wfDebug( __METHOD__."($code): cache for $code expired due to " .
                                        get_class( $dep ) . "\n" );
                                return true;
                        }
                }
                return false;
        }

        /**
         * Initialise a language in this object. Rebuild the cache if necessary.
         */
        protected function initLanguage( $code ) {
                if ( isset( $this->initialisedLangs[$code] ) ) {
                        return;
                }
                $this->initialisedLangs[$code] = true;

                # If the code is of the wrong form for a Messages*.php file, do a shallow fallback
                if ( !Language::isValidBuiltInCode( $code ) ) {
                        $this->initShallowFallback( $code, 'en' );
                        return;
                }

                # Recache the data if necessary
                if ( !$this->manualRecache && $this->isExpired( $code ) ) {
                        if ( file_exists( Language::getMessagesFileName( $code ) ) ) {
                                $this->recache( $code );
                        } elseif ( $code === 'en' ) {
                                throw new MWException( 'MessagesEn.php is missing.' );
                        } else {
                                $this->initShallowFallback( $code, 'en' );
                        }
                        return;
                }

                # Preload some stuff
                $preload = $this->getItem( $code, 'preload' );
                if ( $preload === null ) {
                        if ( $this->manualRecache ) {
                                // No Messages*.php file. Do shallow fallback to en.
                                if ( $code === 'en' ) {
                                        throw new MWException( 'No localisation cache found for English. ' .
                                                'Please run maintenance/rebuildLocalisationCache.php.' );
                                }
                                $this->initShallowFallback( $code, 'en' );
                                return;
                        } else {
                                throw new MWException( 'Invalid or missing localisation cache.' );
                        }
                }
                $this->data[$code] = $preload;
                foreach ( $preload as $key => $item ) {
                        if ( in_array( $key, self::$splitKeys ) ) {
                                foreach ( $item as $subkey => $subitem ) {
                                        $this->loadedSubitems[$code][$key][$subkey] = true;
                                }
                        } else {
                                $this->loadedItems[$code][$key] = true;
                        }
                }
        }

        /**
         * Create a fallback from one language to another, without creating a
         * complete persistent cache.
         */
        public function initShallowFallback( $primaryCode, $fallbackCode ) {
                $this->data[$primaryCode] =& $this->data[$fallbackCode];
                $this->loadedItems[$primaryCode] =& $this->loadedItems[$fallbackCode];
                $this->loadedSubitems[$primaryCode] =& $this->loadedSubitems[$fallbackCode];
                $this->shallowFallbacks[$primaryCode] = $fallbackCode;
        }

        /**
         * Read a PHP file containing localisation data.
         */
        protected function readPHPFile( $_fileName, $_fileType ) {
                // Disable APC caching
                $_apcEnabled = ini_set( 'apc.cache_by_default', '0' );
                include( $_fileName );
                ini_set( 'apc.cache_by_default', $_apcEnabled );

                if ( $_fileType == 'core' || $_fileType == 'extension' ) {
                        $data = compact( self::$allKeys );
                } elseif ( $_fileType == 'aliases' ) {
                        $data = compact( 'aliases' );
                } else {
                        throw new MWException( __METHOD__.": Invalid file type: $_fileType" );
                }
                return $data;
        }

        /**
         * Merge two localisation values, a primary and a fallback, overwriting the
         * primary value in place.
         */
        protected function mergeItem( $key, &$value, $fallbackValue ) {
                if ( !is_null( $value ) ) {
                        if ( !is_null( $fallbackValue ) ) {
                                if ( in_array( $key, self::$mergeableMapKeys ) ) {
                                        $value = $value + $fallbackValue;
                                } elseif ( in_array( $key, self::$mergeableListKeys ) ) {
                                        $value = array_unique( array_merge( $fallbackValue, $value ) );
                                } elseif ( in_array( $key, self::$mergeableAliasListKeys ) ) {
                                        $value = array_merge_recursive( $value, $fallbackValue );
                                } elseif ( in_array( $key, self::$optionalMergeKeys ) ) {
                                        if ( !empty( $value['inherit'] ) )  {
                                                $value = array_merge( $fallbackValue, $value );
                                        }
                                        if ( isset( $value['inherit'] ) ) {
                                                unset( $value['inherit'] );
                                        }
                                } elseif ( in_array( $key, self::$magicWordKeys ) ) {
                                        $this->mergeMagicWords( $value, $fallbackValue );
                                }
                        }
                } else {
                        $value = $fallbackValue;
                }
        }

        protected function mergeMagicWords( &$value, $fallbackValue ) {
                foreach ( $fallbackValue as $magicName => $fallbackInfo ) {
                        if ( !isset( $value[$magicName] ) ) {
                                $value[$magicName] = $fallbackInfo;
                        } else {
                                $oldSynonyms = array_slice( $fallbackInfo, 1 );
                                $newSynonyms = array_slice( $value[$magicName], 1 );
                                $synonyms = array_values( array_unique( array_merge(
                                        $newSynonyms, $oldSynonyms ) ) );
                                $value[$magicName] = array_merge( array( $fallbackInfo[0] ), $synonyms );
                        }
                }
        }

        /**
         * Given an array mapping language code to localisation value, such as is
         * found in extension *.i18n.php files, iterate through a fallback sequence
         * to merge the given data with an existing primary value.
         *
         * Returns true if any data from the extension array was used, false
         * otherwise.
         */
        protected function mergeExtensionItem( $codeSequence, $key, &$value, $fallbackValue ) {
                $used = false;
                foreach ( $codeSequence as $code ) {
                        if ( isset( $fallbackValue[$code] ) ) {
                                $this->mergeItem( $key, $value, $fallbackValue[$code] );
                                $used = true;
                        }
                }
                return $used;
        }

        /**
         * Load localisation data for a given language for both core and extensions
         * and save it to the persistent cache store and the process cache
         */
        public function recache( $code ) {
                static $recursionGuard = array();
                global $wgExtensionMessagesFiles, $wgExtensionAliasesFiles;
                wfProfileIn( __METHOD__ );

                if ( !$code ) {
                        throw new MWException( "Invalid language code requested" );
                }
                $this->recachedLangs[$code] = true;

                # Initial values
                $initialData = array_combine(
                        self::$allKeys,
                        array_fill( 0, count( self::$allKeys ), null ) );
                $coreData = $initialData;
                $deps = array();

                # Load the primary localisation from the source file
                $fileName = Language::getMessagesFileName( $code );
                if ( !file_exists( $fileName ) ) {
                        wfDebug( __METHOD__.": no localisation file for $code, using fallback to en\n" );
                        $coreData['fallback'] = 'en';
                } else {
                        $deps[] = new FileDependency( $fileName );
                        $data = $this->readPHPFile( $fileName, 'core' );
                        wfDebug( __METHOD__.": got localisation for $code from source\n" );

                        # Merge primary localisation
                        foreach ( $data as $key => $value ) {
                                $this->mergeItem( $key, $coreData[$key], $value );
                        }
                }

                # Fill in the fallback if it's not there already
                if ( is_null( $coreData['fallback'] ) ) {
                        $coreData['fallback'] = $code === 'en' ? false : 'en';
                }

                if ( $coreData['fallback'] !== false ) {
                        # Guard against circular references
                        if ( isset( $recursionGuard[$code] ) ) {
                                throw new MWException( "Error: Circular fallback reference in language code $code" );
                        }
                        $recursionGuard[$code] = true;

                        # Load the fallback localisation item by item and merge it
                        $deps = array_merge( $deps, $this->getItem( $coreData['fallback'], 'deps' ) );
                        foreach ( self::$allKeys as $key ) {
                                if ( is_null( $coreData[$key] ) || $this->isMergeableKey( $key ) ) {
                                        $fallbackValue = $this->getItem( $coreData['fallback'], $key );
                                        $this->mergeItem( $key, $coreData[$key], $fallbackValue );
                                }
                        }
                        $fallbackSequence = $this->getItem( $coreData['fallback'], 'fallbackSequence' );
                        array_unshift( $fallbackSequence, $coreData['fallback'] );
                        $coreData['fallbackSequence'] = $fallbackSequence;
                        unset( $recursionGuard[$code] );
                } else {
                        $coreData['fallbackSequence'] = array();
                }
                $codeSequence = array_merge( array( $code ), $coreData['fallbackSequence'] );

                # Load the extension localisations
                # This is done after the core because we know the fallback sequence now.
                # But it has a higher precedence for merging so that we can support things
                # like site-specific message overrides.
                $allData = $initialData;
                foreach ( $wgExtensionMessagesFiles as $fileName ) {
                        $data = $this->readPHPFile( $fileName, 'extension' );
                        $used = false;
                        foreach ( $data as $key => $item ) {
                                if( $this->mergeExtensionItem( $codeSequence, $key, $allData[$key], $item ) ) {
                                        $used = true;
                                }
                        }
                        if ( $used ) {
                                $deps[] = new FileDependency( $fileName );
                        }
                }

                # Load deprecated $wgExtensionAliasesFiles
                foreach ( $wgExtensionAliasesFiles as $fileName ) {
                        $data = $this->readPHPFile( $fileName, 'aliases' );
                        if ( !isset( $data['aliases'] ) ) {
                                continue;
                        }
                        $used = $this->mergeExtensionItem( $codeSequence, 'specialPageAliases',
                                $allData['specialPageAliases'], $data['aliases'] );
                        if ( $used ) {
                                $deps[] = new FileDependency( $fileName );
                        }
                }

                # Merge core data into extension data
                foreach ( $coreData as $key => $item ) {
                        $this->mergeItem( $key, $allData[$key], $item );
                }

                # Add cache dependencies for any referenced globals
                $deps['wgExtensionMessagesFiles'] = new GlobalDependency( 'wgExtensionMessagesFiles' );
                $deps['wgExtensionAliasesFiles'] = new GlobalDependency( 'wgExtensionAliasesFiles' );
                $deps['version'] = new ConstantDependency( 'MW_LC_VERSION' );

                # Add dependencies to the cache entry
                $allData['deps'] = $deps;

                # Replace spaces with underscores in namespace names
                $allData['namespaceNames'] = str_replace( ' ', '_', $allData['namespaceNames'] );

                # And do the same for special page aliases. $page is an array.
                foreach ( $allData['specialPageAliases'] as &$page ) {
                        $page = str_replace( ' ', '_', $page );
                }
                # Decouple the reference to prevent accidental damage
                unset($page);

                # Fix broken defaultUserOptionOverrides
                if ( !is_array( $allData['defaultUserOptionOverrides'] ) ) {
                        $allData['defaultUserOptionOverrides'] = array();
                }

                # Set the list keys
                $allData['list'] = array();
                foreach ( self::$splitKeys as $key ) {
                        $allData['list'][$key] = array_keys( $allData[$key] );
                }

                # Run hooks
                wfRunHooks( 'LocalisationCacheRecache', array( $this, $code, &$allData ) );

                if ( is_null( $allData['defaultUserOptionOverrides'] ) ) {
                        throw new MWException( __METHOD__.': Localisation data failed sanity check! ' .
                                'Check that your languages/messages/MessagesEn.php file is intact.' );
                }

                # Set the preload key
                $allData['preload'] = $this->buildPreload( $allData );

                # Save to the process cache and register the items loaded
                $this->data[$code] = $allData;
                foreach ( $allData as $key => $item ) {
                        $this->loadedItems[$code][$key] = true;
                }

                # Save to the persistent cache
                $this->store->startWrite( $code );
                foreach ( $allData as $key => $value ) {
                        if ( in_array( $key, self::$splitKeys ) ) {
                                foreach ( $value as $subkey => $subvalue ) {
                                        $this->store->set( "$key:$subkey", $subvalue );
                                }
                        } else {
                                $this->store->set( $key, $value );
                        }
                }
                $this->store->finishWrite();

                # Clear out the MessageBlobStore
                # HACK: If using a null (i.e. disabled) storage backend, we
                # can't write to the MessageBlobStore either
                if ( !$this->store instanceof LCStore_Null ) {
                        MessageBlobStore::clear();
                }

                wfProfileOut( __METHOD__ );
        }

        /**
         * Build the preload item from the given pre-cache data.
         *
         * The preload item will be loaded automatically, improving performance
         * for the commonly-requested items it contains.
         */
        protected function buildPreload( $data ) {
                $preload = array( 'messages' => array() );
                foreach ( self::$preloadedKeys as $key ) {
                        $preload[$key] = $data[$key];
                }
                foreach ( $data['preloadedMessages'] as $subkey ) {
                        if ( isset( $data['messages'][$subkey] ) ) {
                                $subitem = $data['messages'][$subkey];
                        } else {
                                $subitem = null;
                        }
                        $preload['messages'][$subkey] = $subitem;
                }
                return $preload;
        }

        /**
         * Unload the data for a given language from the object cache.
         * Reduces memory usage.
         */
        public function unload( $code ) {
                unset( $this->data[$code] );
                unset( $this->loadedItems[$code] );
                unset( $this->loadedSubitems[$code] );
                unset( $this->initialisedLangs[$code] );
                foreach ( $this->shallowFallbacks as $shallowCode => $fbCode ) {
                        if ( $fbCode === $code ) {
                                $this->unload( $shallowCode );
                        }
                }
        }

        /**
         * Unload all data
         */
        public function unloadAll() {
                foreach ( $this->initialisedLangs as $lang => $unused ) {
                        $this->unload( $lang );
                }
        }

        /**
         * Disable the storage backend
         */
        public function disableBackend() {
                $this->store = new LCStore_Null;
                $this->manualRecache = false;
        }
}

/**
 * Interface for the persistence layer of LocalisationCache.
 *
 * The persistence layer is two-level hierarchical cache. The first level
 * is the language, the second level is the item or subitem.
 *
 * Since the data for a whole language is rebuilt in one operation, it needs
 * to have a fast and atomic method for deleting or replacing all of the
 * current data for a given language. The interface reflects this bulk update
 * operation. Callers writing to the cache must first call startWrite(), then
 * will call set() a couple of thousand times, then will call finishWrite()
 * to commit the operation. When finishWrite() is called, the cache is
 * expected to delete all data previously stored for that language.
 *
 * The values stored are PHP variables suitable for serialize(). Implementations
 * of LCStore are responsible for serializing and unserializing.
 */
interface LCStore {
        /**
         * Get a value.
         * @param $code Language code
         * @param $key Cache key
         */
        function get( $code, $key );

        /**
         * Start a write transaction.
         * @param $code Language code
         */
        function startWrite( $code );

        /**
         * Finish a write transaction.
         */
        function finishWrite();

        /**
         * Set a key to a given value. startWrite() must be called before this
         * is called, and finishWrite() must be called afterwards.
         */
        function set( $key, $value );

}

/**
 * LCStore implementation which uses the standard DB functions to store data.
 * This will work on any MediaWiki installation.
 */
class LCStore_DB implements LCStore {
        var $currentLang;
        var $writesDone = false;
        var $dbw, $batch;
        var $readOnly = false;

        public function get( $code, $key ) {
                if ( $this->writesDone ) {
                        $db = wfGetDB( DB_MASTER );
                } else {
                        $db = wfGetDB( DB_SLAVE );
                }
                $row = $db->selectRow( 'l10n_cache', array( 'lc_value' ),
                        array( 'lc_lang' => $code, 'lc_key' => $key ), __METHOD__ );
                if ( $row ) {
                        return unserialize( $row->lc_value );
                } else {
                        return null;
                }
        }

        public function startWrite( $code ) {
                if ( $this->readOnly ) {
                        return;
                }
                if ( !$code ) {
                        throw new MWException( __METHOD__.": Invalid language \"$code\"" );
                }
                $this->dbw = wfGetDB( DB_MASTER );
                try {
                        $this->dbw->begin();
                        $this->dbw->delete( 'l10n_cache', array( 'lc_lang' => $code ), __METHOD__ );
                } catch ( DBQueryError $e ) {
                        if ( $this->dbw->wasReadOnlyError() ) {
                                $this->readOnly = true;
                                $this->dbw->rollback();
                                $this->dbw->ignoreErrors( false );
                                return;
                        } else {
                                throw $e;
                        }
                }
                $this->currentLang = $code;
                $this->batch = array();
        }

        public function finishWrite() {
                if ( $this->readOnly ) {
                        return;
                }
                if ( $this->batch ) {
                        $this->dbw->insert( 'l10n_cache', $this->batch, __METHOD__ );
                }
                $this->dbw->commit();
                $this->currentLang = null;
                $this->dbw = null;
                $this->batch = array();
                $this->writesDone = true;
        }

        public function set( $key, $value ) {
                if ( $this->readOnly ) {
                        return;
                }
                if ( is_null( $this->currentLang ) ) {
                        throw new MWException( __CLASS__.': must call startWrite() before calling set()' );
                }
                $this->batch[] = array(
                        'lc_lang' => $this->currentLang,
                        'lc_key' => $key,
                        'lc_value' => serialize( $value ) );
                if ( count( $this->batch ) >= 100 ) {
                        $this->dbw->insert( 'l10n_cache', $this->batch, __METHOD__ );
                        $this->batch = array();
                }
        }
}

/**
 * LCStore implementation which stores data as a collection of CDB files in the
 * directory given by $wgCacheDirectory. If $wgCacheDirectory is not set, this
 * will throw an exception.
 *
 * Profiling indicates that on Linux, this implementation outperforms MySQL if
 * the directory is on a local filesystem and there is ample kernel cache
 * space. The performance advantage is greater when the DBA extension is
 * available than it is with the PHP port.
 *
 * See Cdb.php and http://cr.yp.to/cdb.html
 */
class LCStore_CDB implements LCStore {
        var $readers, $writer, $currentLang, $directory;

        function __construct( $conf = array() ) {
                global $wgCacheDirectory;
                if ( isset( $conf['directory'] ) ) {
                        $this->directory = $conf['directory'];
                } else {
                        $this->directory = $wgCacheDirectory;
                }
        }

        public function get( $code, $key ) {
                if ( !isset( $this->readers[$code] ) ) {
                        $fileName = $this->getFileName( $code );
                        if ( !file_exists( $fileName ) ) {
                                $this->readers[$code] = false;
                        } else {
                                $this->readers[$code] = CdbReader::open( $fileName );
                        }
                }
                if ( !$this->readers[$code] ) {
                        return null;
                } else {
                        $value = $this->readers[$code]->get( $key );
                        if ( $value === false ) {
                                return null;
                        }
                        return unserialize( $value );
                }
        }

        public function startWrite( $code ) {
                if ( !file_exists( $this->directory ) ) {
                        if ( !wfMkdirParents( $this->directory ) ) {
                                throw new MWException( "Unable to create the localisation store " .
                                        "directory \"{$this->directory}\"" );
                        }
                }
                // Close reader to stop permission errors on write
                if( !empty($this->readers[$code]) ) {
                        $this->readers[$code]->close();
                }
                $this->writer = CdbWriter::open( $this->getFileName( $code ) );
                $this->currentLang = $code;
        }

        public function finishWrite() {
                // Close the writer
                $this->writer->close();
                $this->writer = null;
                unset( $this->readers[$this->currentLang] );
                $this->currentLang = null;
        }

        public function set( $key, $value ) {
                if ( is_null( $this->writer ) ) {
                        throw new MWException( __CLASS__.': must call startWrite() before calling set()' );
                }
                $this->writer->set( $key, serialize( $value ) );
        }

        protected function getFileName( $code ) {
                if ( !$code || strpos( $code, '/' ) !== false ) {
                        throw new MWException( __METHOD__.": Invalid language \"$code\"" );
                }
                return "{$this->directory}/l10n_cache-$code.cdb";
        }
}

/**
 * Null store backend, used to avoid DB errors during install
 */
class LCStore_Null implements LCStore {
        public function get( $code, $key ) {
                return null;
        }

        public function startWrite( $code ) {}
        public function finishWrite() {}
        public function set( $key, $value ) {}
}

/**
 * A localisation cache optimised for loading large amounts of data for many
 * languages. Used by rebuildLocalisationCache.php.
 */
class LocalisationCache_BulkLoad extends LocalisationCache {
        /**
         * A cache of the contents of data files.
         * Core files are serialized to avoid using ~1GB of RAM during a recache.
         */
        var $fileCache = array();

        /**
         * Most recently used languages. Uses the linked-list aspect of PHP hashtables
         * to keep the most recently used language codes at the end of the array, and
         * the language codes that are ready to be deleted at the beginning.
         */
        var $mruLangs = array();

        /**
         * Maximum number of languages that may be loaded into $this->data
         */
        var $maxLoadedLangs = 10;

        protected function readPHPFile( $fileName, $fileType ) {
                $serialize = $fileType === 'core';
                if ( !isset( $this->fileCache[$fileName][$fileType] ) ) {
                        $data = parent::readPHPFile( $fileName, $fileType );
                        if ( $serialize ) {
                                $encData = serialize( $data );
                        } else {
                                $encData = $data;
                        }
                        $this->fileCache[$fileName][$fileType] = $encData;
                        return $data;
                } elseif ( $serialize ) {
                        return unserialize( $this->fileCache[$fileName][$fileType] );
                } else {
                        return $this->fileCache[$fileName][$fileType];
                }
        }

        public function getItem( $code, $key ) {
                unset( $this->mruLangs[$code] );
                $this->mruLangs[$code] = true;
                return parent::getItem( $code, $key );
        }

        public function getSubitem( $code, $key, $subkey ) {
                unset( $this->mruLangs[$code] );
                $this->mruLangs[$code] = true;
                return parent::getSubitem( $code, $key, $subkey );
        }

        public function recache( $code ) {
                parent::recache( $code );
                unset( $this->mruLangs[$code] );
                $this->mruLangs[$code] = true;
                $this->trimCache();
        }

        public function unload( $code ) {
                unset( $this->mruLangs[$code] );
                parent::unload( $code );
        }

        /**
         * Unload cached languages until there are less than $this->maxLoadedLangs
         */
        protected function trimCache() {
                while ( count( $this->data ) > $this->maxLoadedLangs && count( $this->mruLangs ) ) {
                        reset( $this->mruLangs );
                        $code = key( $this->mruLangs );
                        wfDebug( __METHOD__.": unloading $code\n" );
                        $this->unload( $code );
                }
        }
}