includes/MessageCache.php

   1 <?php
   2 /**
   3  *
   4  * @addtogroup Cache
   5  */
   6
   7 /**
   8  *
   9  */
  10 define( 'MSG_LOAD_TIMEOUT', 60);
  11 define( 'MSG_LOCK_TIMEOUT', 10);
  12 define( 'MSG_WAIT_TIMEOUT', 10);
  13 define( 'MSG_CACHE_VERSION', 1 );
  14
  15 /**
  16  * Message cache
  17  * Performs various MediaWiki namespace-related functions
  18  *
  19  */
  20 class MessageCache {
  21         var $mCache, $mUseCache, $mDisable, $mExpiry;
  22         var $mMemcKey, $mKeys, $mParserOptions, $mParser;
  23         var $mExtensionMessages = array();
  24         var $mInitialised = false;
  25         var $mDeferred = true;
  26
  27         function __construct( &$memCached, $useDB, $expiry, $memcPrefix) {
  28                 wfProfileIn( __METHOD__ );
  29
  30                 $this->mUseCache = !is_null( $memCached );
  31                 $this->mMemc = &$memCached;
  32                 $this->mDisable = !$useDB;
  33                 $this->mExpiry = $expiry;
  34                 $this->mDisableTransform = false;
  35                 $this->mMemcKey = $memcPrefix.':messages';
  36                 $this->mKeys = false; # initialised on demand
  37                 $this->mInitialised = true;
  38                 $this->mParser = null;
  39
  40                 # When we first get asked for a message,
  41                 # then we'll fill up the cache. If we
  42                 # can return a cache hit, this saves
  43                 # some extra milliseconds
  44                 $this->mDeferred = true;
  45
  46                 wfProfileOut( __METHOD__ );
  47         }
  48
  49         function getParserOptions() {
  50                 if ( !$this->mParserOptions ) {
  51                         $this->mParserOptions = new ParserOptions;
  52                 }
  53                 return $this->mParserOptions;
  54         }
  55
  56         /**
  57          * Try to load the cache from a local file
  58          */
  59         function loadFromLocal( $hash ) {
  60                 global $wgLocalMessageCache;
  61
  62                 $this->mCache = false;
  63                 if ( $wgLocalMessageCache === false ) {
  64                         return;
  65                 }
  66
  67                 $filename = "$wgLocalMessageCache/messages-" . wfWikiID();
  68
  69                 wfSuppressWarnings();
  70                 $file = fopen( $filename, 'r' );
  71                 wfRestoreWarnings();
  72                 if ( !$file ) {
  73                         return;
  74                 }
  75
  76                 // Check to see if the file has the hash specified
  77                 $localHash = fread( $file, 32 );
  78                 if ( $hash == $localHash ) {
  79                         // All good, get the rest of it
  80                         $serialized = fread( $file, 10000000 );
  81                         $this->setCache( unserialize( $serialized ) );
  82                 }
  83                 fclose( $file );
  84         }
  85
  86         /**
  87          * Save the cache to a local file
  88          */
  89         function saveToLocal( $serialized, $hash ) {
  90                 global $wgLocalMessageCache;
  91
  92                 if ( $wgLocalMessageCache === false ) {
  93                         return;
  94                 }
  95
  96                 $filename = "$wgLocalMessageCache/messages-" . wfWikiID();
  97                 $oldUmask = umask( 0 );
  98                 wfMkdirParents( $wgLocalMessageCache, 0777 );
  99                 umask( $oldUmask );
 100
 101                 $file = fopen( $filename, 'w' );
 102                 if ( !$file ) {
 103                         wfDebug( "Unable to open local cache file for writing\n" );
 104                         return;
 105                 }
 106
 107                 fwrite( $file, $hash . $serialized );
 108                 fclose( $file );
 109                 @chmod( $filename, 0666 );
 110         }
 111
 112         function loadFromScript( $hash ) {
 113                 global $wgLocalMessageCache;
 114                 if ( $wgLocalMessageCache === false ) {
 115                         return;
 116                 }
 117
 118                 $filename = "$wgLocalMessageCache/messages-" . wfWikiID();
 119
 120                 wfSuppressWarnings();
 121                 $file = fopen( $filename, 'r' );
 122                 wfRestoreWarnings();
 123                 if ( !$file ) {
 124                         return;
 125                 }
 126                 $localHash=substr(fread($file,40),8);
 127                 fclose($file);
 128                 if ($hash!=$localHash) {
 129                         return;
 130                 }
 131                 require("$wgLocalMessageCache/messages-" . wfWikiID());
 132                 $this->setCache( $this->mCache);
 133         }
 134
 135         function saveToScript($array, $hash) {
 136                 global $wgLocalMessageCache;
 137                 if ( $wgLocalMessageCache === false ) {
 138                         return;
 139                 }
 140
 141                 $filename = "$wgLocalMessageCache/messages-" . wfWikiID();
 142                 $oldUmask = umask( 0 );
 143                 wfMkdirParents( $wgLocalMessageCache, 0777 );
 144                 umask( $oldUmask );
 145                 $file = fopen( $filename.'.tmp', 'w');
 146                 fwrite($file,"<?php\n//$hash\n\n \$this->mCache = array(");
 147
 148                 foreach ($array as $key => $message) {
 149                         fwrite($file, "'". $this->escapeForScript($key).
 150                                 "' => '" . $this->escapeForScript($message).
 151                                 "',\n");
 152                 }
 153                 fwrite($file,");\n?>");
 154                 fclose($file);
 155                 rename($filename.'.tmp',$filename);
 156         }
 157
 158         function escapeForScript($string) {
 159                 $string = str_replace( '\\', '\\\\', $string );
 160                 $string = str_replace( '\'', '\\\'', $string );
 161                 return $string;
 162         }
 163
 164         /**
 165          * Set the cache to $cache, if it is valid. Otherwise set the cache to false.
 166          */
 167         function setCache( $cache ) {
 168                 if ( isset( $cache['VERSION'] ) && $cache['VERSION'] == MSG_CACHE_VERSION ) {
 169                         $this->mCache = $cache;
 170                 } else {
 171                         $this->mCache = false;
 172                 }
 173         }
 174
 175         /**
 176          * Loads messages either from memcached or the database, if not disabled
 177          * On error, quietly switches to a fallback mode
 178          * Returns false for a reportable error, true otherwise
 179          */
 180         function load() {
 181                 global $wgLocalMessageCache, $wgLocalMessageCacheSerialized;
 182
 183                 if ( $this->mDisable ) {
 184                         static $shownDisabled = false;
 185                         if ( !$shownDisabled ) {
 186                                 wfDebug( "MessageCache::load(): disabled\n" );
 187                                 $shownDisabled = true;
 188                         }
 189                         return true;
 190                 }
 191                 if ( !$this->mUseCache ) {
 192                         $this->mDeferred = false;
 193                         return true;
 194                 }
 195
 196                 $fname = 'MessageCache::load';
 197                 wfProfileIn( $fname );
 198                 $success = true;
 199
 200                 $this->mCache = false;
 201
 202                 # Try local cache
 203                 wfProfileIn( $fname.'-fromlocal' );
 204                 $hash = $this->mMemc->get( "{$this->mMemcKey}-hash" );
 205                 if ( $hash ) {
 206                         if ($wgLocalMessageCacheSerialized) {
 207                                 $this->loadFromLocal( $hash );
 208                         } else {
 209                                 $this->loadFromScript( $hash );
 210                         }
 211                         if ( $this->mCache ) {
 212                                 wfDebug( "MessageCache::load(): got from local cache\n" );
 213                         }
 214                 }
 215                 wfProfileOut( $fname.'-fromlocal' );
 216
 217                 # Try memcached
 218                 if ( !$this->mCache ) {
 219                         wfProfileIn( $fname.'-fromcache' );
 220                         $this->setCache( $this->mMemc->get( $this->mMemcKey ) );
 221                         if ( $this->mCache ) {
 222                                 wfDebug( "MessageCache::load(): got from global cache\n" );
 223                                 # Save to local cache
 224                                 if ( $wgLocalMessageCache !== false ) {
 225                                         $serialized = serialize( $this->mCache );
 226                                         if ( !$hash ) {
 227                                                 $hash = md5( $serialized );
 228                                                 $this->mMemc->set( "{$this->mMemcKey}-hash", $hash, $this->mExpiry );
 229                                         }
 230                                         if ($wgLocalMessageCacheSerialized) {
 231                                                 $this->saveToLocal( $serialized,$hash );
 232                                         } else {
 233                                                 $this->saveToScript( $this->mCache, $hash );
 234                                         }
 235                                 }
 236                         }
 237                         wfProfileOut( $fname.'-fromcache' );
 238                 }
 239
 240
 241                 # If there's nothing in memcached, load all the messages from the database
 242                 if ( !$this->mCache ) {
 243                         wfDebug( "MessageCache::load(): cache is empty\n" );
 244                         $this->lock();
 245                         # Other threads don't need to load the messages if another thread is doing it.
 246                         $success = $this->mMemc->add( $this->mMemcKey.'-status', "loading", MSG_LOAD_TIMEOUT );
 247                         if ( $success ) {
 248                                 wfProfileIn( $fname.'-load' );
 249                                 wfDebug( "MessageCache::load(): loading all messages from DB\n" );
 250                                 $this->loadFromDB();
 251                                 wfProfileOut( $fname.'-load' );
 252
 253                                 # Save in memcached
 254                                 # Keep trying if it fails, this is kind of important
 255                                 wfProfileIn( $fname.'-save' );
 256                                 for ($i=0; $i<20 &&
 257                                                    !$this->mMemc->set( $this->mMemcKey, $this->mCache, $this->mExpiry );
 258                                          $i++ ) {
 259                                         usleep(mt_rand(500000,1500000));
 260                                 }
 261
 262                                 # Save to local cache
 263                                 if ( $wgLocalMessageCache !== false ) {
 264                                         $serialized = serialize( $this->mCache );
 265                                         $hash = md5( $serialized );
 266                                         $this->mMemc->set( "{$this->mMemcKey}-hash", $hash, $this->mExpiry );
 267                                         if ($wgLocalMessageCacheSerialized) {
 268                                                 $this->saveToLocal( $serialized,$hash );
 269                                         } else {
 270                                                 $this->saveToScript( $this->mCache, $hash );
 271                                         }
 272                                 }
 273
 274                                 wfProfileOut( $fname.'-save' );
 275                                 if ( $i == 20 ) {
 276                                         $this->mMemc->set( $this->mMemcKey.'-status', 'error', 60*5 );
 277                                         wfDebug( "MemCached set error in MessageCache: restart memcached server!\n" );
 278                                 } else {
 279                                         $this->mMemc->delete( $this->mMemcKey.'-status' );
 280                                 }
 281                         }
 282                         $this->unlock();
 283                 }
 284
 285                 if ( !is_array( $this->mCache ) ) {
 286                         wfDebug( "MessageCache::load(): unable to load cache, disabled\n" );
 287                         $this->mDisable = true;
 288                         $this->mCache = false;
 289                 }
 290                 wfProfileOut( $fname );
 291                 $this->mDeferred = false;
 292                 return $success;
 293         }
 294
 295         /**
 296          * Loads all or main part of cacheable messages from the database
 297          */
 298         function loadFromDB() {
 299                 global $wgMaxMsgCacheEntrySize;
 300
 301                 wfProfileIn( __METHOD__ );
 302                 $dbr =& wfGetDB( DB_SLAVE );
 303                 $this->mCache = array();
 304
 305                 # Load titles for all oversized pages in the MediaWiki namespace
 306                 $res = $dbr->select( 'page', 'page_title',
 307                         array(
 308                                 'page_len > ' . intval( $wgMaxMsgCacheEntrySize ),
 309                                 'page_is_redirect' => 0,
 310                                 'page_namespace' => NS_MEDIAWIKI,
 311                         ),
 312                         __METHOD__ );
 313                 while ( $row = $dbr->fetchObject( $res ) ) {
 314                         $this->mCache[$row->page_title] = '!TOO BIG';
 315                 }
 316                 $dbr->freeResult( $res );
 317
 318                 # Load text for the remaining pages
 319                 $res = $dbr->select( array( 'page', 'revision', 'text' ),
 320                         array( 'page_title', 'old_text', 'old_flags' ),
 321                         array(
 322                                 'page_is_redirect' => 0,
 323                                 'page_namespace' => NS_MEDIAWIKI,
 324                                 'page_latest=rev_id',
 325                                 'rev_text_id=old_id',
 326                                 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize ) ),
 327                         __METHOD__ );
 328
 329                 for ( $row = $dbr->fetchObject( $res ); $row; $row = $dbr->fetchObject( $res ) ) {
 330                         $this->mCache[$row->page_title] = ' ' . Revision::getRevisionText( $row );
 331                 }
 332                 $this->mCache['VERSION'] = MSG_CACHE_VERSION;
 333                 $dbr->freeResult( $res );
 334                 wfProfileOut( __METHOD__ );
 335         }
 336
 337         /**
 338          * Not really needed anymore
 339          */
 340         function getKeys() {
 341                 global $wgContLang;
 342                 if ( !$this->mKeys ) {
 343                         $this->mKeys = array();
 344                         $allMessages = Language::getMessagesFor( 'en' );
 345                         foreach ( $allMessages as $key => $unused ) {
 346                                 $title = $wgContLang->ucfirst( $key );
 347                                 array_push( $this->mKeys, $title );
 348                         }
 349                 }
 350                 return $this->mKeys;
 351         }
 352
 353         function replace( $title, $text ) {
 354                 global $wgLocalMessageCache, $wgLocalMessageCacheSerialized, $parserMemc;
 355                 global $wgMaxMsgCacheEntrySize;
 356
 357                 wfProfileIn( __METHOD__ );
 358                 $this->lock();
 359                 $this->load();
 360                 $parserMemc->delete(wfMemcKey('sidebar'));
 361                 if ( is_array( $this->mCache ) ) {
 362                         if ( $text === false ) {
 363                                 # Article was deleted
 364                                 unset( $this->mCache[$title] );
 365                                 $this->mMemc->delete( "$this->mMemcKey:{$title}" );
 366                         } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 367                                 $this->mCache[$title] = '!TOO BIG';
 368                                 $this->mMemc->set( "$this->mMemcKey:{$title}", ' '.$text, $this->mExpiry );
 369                         } else {
 370                                 $this->mCache[$title] = ' ' . $text;
 371                                 $this->mMemc->delete( "$this->mMemcKey:{$title}" );
 372                         }
 373                         $this->mMemc->set( $this->mMemcKey, $this->mCache, $this->mExpiry );
 374
 375                         # Save to local cache
 376                         if ( $wgLocalMessageCache !== false ) {
 377                                 $serialized = serialize( $this->mCache );
 378                                 $hash = md5( $serialized );
 379                                 $this->mMemc->set( "{$this->mMemcKey}-hash", $hash, $this->mExpiry );
 380                                 if ($wgLocalMessageCacheSerialized) {
 381                                         $this->saveToLocal( $serialized,$hash );
 382                                 } else {
 383                                         $this->saveToScript( $this->mCache, $hash );
 384                                 }
 385                         }
 386                 }
 387                 $this->unlock();
 388                 wfProfileOut( __METHOD__ );
 389         }
 390
 391         /**
 392          * Returns success
 393          * Represents a write lock on the messages key
 394          */
 395         function lock() {
 396                 if ( !$this->mUseCache ) {
 397                         return true;
 398                 }
 399
 400                 $lockKey = $this->mMemcKey . 'lock';
 401                 for ($i=0; $i < MSG_WAIT_TIMEOUT && !$this->mMemc->add( $lockKey, 1, MSG_LOCK_TIMEOUT ); $i++ ) {
 402                         sleep(1);
 403                 }
 404
 405                 return $i >= MSG_WAIT_TIMEOUT;
 406         }
 407
 408         function unlock() {
 409                 if ( !$this->mUseCache ) {
 410                         return;
 411                 }
 412
 413                 $lockKey = $this->mMemcKey . 'lock';
 414                 $this->mMemc->delete( $lockKey );
 415         }
 416
 417         /**
 418          * Get a message from either the content language or the user language.
 419          *
 420          * @param string $key The message cache key
 421          * @param bool $useDB Get the message from the DB, false to use only the localisation
 422          * @param bool $forContent Get the message from the content language rather than the
 423          *                         user language
 424          * @param bool $isFullKey Specifies whether $key is a two part key "lang/msg".
 425          */
 426         function get( $key, $useDB = true, $forContent = true, $isFullKey = false ) {
 427                 global $wgContLanguageCode, $wgContLang, $wgLang;
 428                 if( $forContent ) {
 429                         $lang =& $wgContLang;
 430                 } else {
 431                         $lang =& $wgLang;
 432                 }
 433                 $langcode = $lang->getCode();
 434                 # If uninitialised, someone is trying to call this halfway through Setup.php
 435                 if( !$this->mInitialised ) {
 436                         return '&lt;' . htmlspecialchars($key) . '&gt;';
 437                 }
 438                 # If cache initialization was deferred, start it now.
 439                 if( $this->mDeferred && !$this->mDisable && $useDB ) {
 440                         $this->load();
 441                 }
 442
 443                 $message = false;
 444
 445                 # Normalise title-case input
 446                 $lckey = $wgContLang->lcfirst( $key );
 447                 $lckey = str_replace( ' ', '_', $lckey );
 448
 449                 # Try the MediaWiki namespace
 450                 if( !$this->mDisable && $useDB ) {
 451                         $title = $wgContLang->ucfirst( $lckey );
 452                         if(!$isFullKey && ($langcode != $wgContLanguageCode) ) {
 453                                 $title .= '/' . $langcode;
 454                         }
 455                         $message = $this->getMsgFromNamespace( $title );
 456                 }
 457                 # Try the extension array
 458                 if( $message === false && isset( $this->mExtensionMessages[$langcode][$lckey] ) ) {
 459                         $message = $this->mExtensionMessages[$langcode][$lckey];
 460                 }
 461                 if ( $message === false && isset( $this->mExtensionMessages['en'][$lckey] ) ) {
 462                         $message = $this->mExtensionMessages['en'][$lckey];
 463                 }
 464
 465                 # Try the array in the language object
 466                 if( $message === false ) {
 467                         #wfDebug( "Trying language object for message $key\n" );
 468                         wfSuppressWarnings();
 469                         $message = $lang->getMessage( $lckey );
 470                         wfRestoreWarnings();
 471                         if ( is_null( $message ) ) {
 472                                 $message = false;
 473                         }
 474                 }
 475
 476                 # Try the array of another language
 477                 if( $message === false && strpos( $lckey, '/' ) ) {
 478                         $message = explode( '/', $lckey );
 479                         if ( $message[1] ) {
 480                                 wfSuppressWarnings();
 481                                 $message = Language::getMessageFor( $message[0], $message[1] );
 482                                 wfRestoreWarnings();
 483                                 if ( is_null( $message ) ) {
 484                                         $message = false;
 485                                 }
 486                         } else {
 487                                 $message = false;
 488                         }
 489                 }
 490
 491                 # Is this a custom message? Try the default language in the db...
 492                 if( ($message === false || $message === '-' ) &&
 493                         !$this->mDisable && $useDB &&
 494                         !$isFullKey && ($langcode != $wgContLanguageCode) ) {
 495                         $message = $this->getMsgFromNamespace( $wgContLang->ucfirst( $lckey ) );
 496                 }
 497
 498                 # Final fallback
 499                 if( $message === false ) {
 500                         return '&lt;' . htmlspecialchars($key) . '&gt;';
 501                 }
 502
 503                 # Replace brace tags
 504                 $message = $this->transform( $message );
 505                 return $message;
 506         }
 507
 508         /**
 509          * Get a message from the MediaWiki namespace, with caching. The key must
 510          * first be converted to two-part lang/msg form if necessary.
 511          *
 512          * @param string $title Message cache key with initial uppercase letter
 513          */
 514         function getMsgFromNamespace( $title ) {
 515                 $message = false;
 516                 $type = false;
 517
 518                 # Try the cache
 519                 if( $this->mUseCache && isset( $this->mCache[$title] ) ) {
 520                         $entry = $this->mCache[$title];
 521                         $type = substr( $entry, 0, 1 );
 522                         if ( $type == ' ' ) {
 523                                 return substr( $entry, 1 );
 524                         }
 525                 }
 526
 527                 # Call message hooks, in case they are defined
 528                 wfRunHooks('MessagesPreLoad', array( $title, &$message ) );
 529                 if ( $message !== false ) {
 530                         return $message;
 531                 }
 532
 533                 # If there is no cache entry and no placeholder, it doesn't exist
 534                 if ( $type != '!' && $message === false ) {
 535                         return false;
 536                 }
 537
 538                 $memcKey = $this->mMemcKey . ':' . $title;
 539
 540                 # Try the individual message cache
 541                 if ( $this->mUseCache ) {
 542                         $entry = $this->mMemc->get( $memcKey );
 543                         if ( $entry ) {
 544                                 $type = substr( $entry, 0, 1 );
 545
 546                                 if ( $type == ' ' ) {
 547                                         $message = substr( $entry, 1 );
 548                                         $this->mCache[$title] = $message;
 549                                         return $message;
 550                                 } elseif ( $entry == '!NONEXISTENT' ) {
 551                                         return false;
 552                                 } else {
 553                                         # Corrupt/obsolete entry, delete it
 554                                         $this->mMemc->delete( $memcKey );
 555                                 }
 556
 557                         }
 558                 }
 559
 560                 # Try loading it from the DB
 561                 $revision = Revision::newFromTitle( Title::makeTitle( NS_MEDIAWIKI, $title ) );
 562                 if( $revision ) {
 563                         $message = $revision->getText();
 564                         if ($this->mUseCache) {
 565                                 $this->mCache[$title] = ' ' . $message;
 566                                 $this->mMemc->set( $memcKey, $message, $this->mExpiry );
 567                         }
 568                 } else {
 569                         # Negative caching
 570                         # Use some special text instead of false, because false gets converted to '' somewhere
 571                         $this->mMemc->set( $memcKey, '!NONEXISTENT', $this->mExpiry );
 572                         $this->mCache[$title] = false;
 573                 }
 574
 575                 return $message;
 576         }
 577
 578         function transform( $message ) {
 579                 global $wgParser;
 580                 if ( !$this->mParser && isset( $wgParser ) ) {
 581                         # Do some initialisation so that we don't have to do it twice
 582                         $wgParser->firstCallInit();
 583                         # Clone it and store it
 584                         $this->mParser = clone $wgParser;
 585                 }
 586                 if ( !$this->mDisableTransform && $this->mParser ) {
 587                         if( strpos( $message, '{{' ) !== false ) {
 588                                 $message = $this->mParser->transformMsg( $message, $this->getParserOptions() );
 589                         }
 590                 }
 591                 return $message;
 592         }
 593
 594         function disable() { $this->mDisable = true; }
 595         function enable() { $this->mDisable = false; }
 596         function disableTransform() { $this->mDisableTransform = true; }
 597         function enableTransform() { $this->mDisableTransform = false; }
 598         function setTransform( $x ) { $this->mDisableTransform = $x; }
 599         function getTransform() { return $this->mDisableTransform; }
 600
 601         /**
 602          * Add a message to the cache
 603          *
 604          * @param mixed $key
 605          * @param mixed $value
 606          * @param string $lang The messages language, English by default
 607          */
 608         function addMessage( $key, $value, $lang = 'en' ) {
 609                 $this->mExtensionMessages[$lang][$key] = $value;
 610         }
 611
 612         /**
 613          * Add an associative array of message to the cache
 614          *
 615          * @param array $messages An associative array of key => values to be added
 616          * @param string $lang The messages language, English by default
 617          */
 618         function addMessages( $messages, $lang = 'en' ) {
 619                 wfProfileIn( __METHOD__ );
 620                 if ( isset( $this->mExtensionMessages[$lang] ) ) {
 621                         $this->mExtensionMessages[$lang] = $messages + $this->mExtensionMessages[$lang];
 622                 } else {
 623                         $this->mExtensionMessages[$lang] = $messages;
 624                 }
 625                 wfProfileOut( __METHOD__ );
 626         }
 627
 628         /**
 629          * Add a 2-D array of messages by lang. Useful for extensions.
 630          * Introduced in 1.9. Please do not use it for now, for backwards compatibility.
 631          *
 632          * @param array $messages The array to be added
 633          */
 634         function addMessagesByLang( $messages ) {
 635                 wfProfileIn( __METHOD__ );
 636                 foreach ( $messages as $key => $value ) {
 637                         $this->addMessages( $value, $key );
 638                 }
 639                 wfProfileOut( __METHOD__ );
 640         }
 641
 642         /**
 643          * Get the extension messages for a specific language
 644          *
 645          * @param string $lang The messages language, English by default
 646          */
 647         function getExtensionMessagesFor( $lang = 'en' ) {
 648                 wfProfileIn( __METHOD__ );
 649                 $messages = array();
 650                 if ( isset( $this->mExtensionMessages[$lang] ) ) {
 651                         $messages = $this->mExtensionMessages[$lang];
 652                 }
 653                 if ( $lang != 'en' ) {
 654                         $messages = $messages + $this->mExtensionMessages['en'];
 655                 }
 656                 wfProfileOut( __METHOD__ );
 657                 return $messages;
 658         }
 659
 660         /**
 661          * Clear all stored messages. Mainly used after a mass rebuild.
 662          */
 663         function clear() {
 664                 global $wgLocalMessageCache;
 665                 if( $this->mUseCache ) {
 666                         # Global cache
 667                         $this->mMemc->delete( $this->mMemcKey );
 668                         # Invalidate all local caches
 669                         $this->mMemc->delete( "{$this->mMemcKey}-hash" );
 670                 }
 671         }
 672
 673         static function loadAllMessages() {
 674                 # Some extensions will load their messages when you load their class file
 675                 wfLoadAllExtensions();
 676                 # Others will respond to this hook
 677                 wfRunHooks( 'LoadAllMessages' );
 678                 # Still others will respond to neither, they are EVIL. We sometimes need to know!
 679         }
 680 }
 681 ?>