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         var $mAllMessagesLoaded;
  27
  28         function __construct( &$memCached, $useDB, $expiry, $memcPrefix) {
  29                 wfProfileIn( __METHOD__ );
  30
  31                 $this->mUseCache = !is_null( $memCached );
  32                 $this->mMemc = &$memCached;
  33                 $this->mDisable = !$useDB;
  34                 $this->mExpiry = $expiry;
  35                 $this->mDisableTransform = false;
  36                 $this->mMemcKey = $memcPrefix.':messages';
  37                 $this->mKeys = false; # initialised on demand
  38                 $this->mInitialised = true;
  39                 $this->mParser = null;
  40
  41                 # When we first get asked for a message,
  42                 # then we'll fill up the cache. If we
  43                 # can return a cache hit, this saves
  44                 # some extra milliseconds
  45                 $this->mDeferred = true;
  46
  47                 wfProfileOut( __METHOD__ );
  48         }
  49
  50         function getParserOptions() {
  51                 if ( !$this->mParserOptions ) {
  52                         $this->mParserOptions = new ParserOptions;
  53                 }
  54                 return $this->mParserOptions;
  55         }
  56
  57         /**
  58          * Try to load the cache from a local file
  59          */
  60         function loadFromLocal( $hash ) {
  61                 global $wgLocalMessageCache;
  62
  63                 $this->mCache = false;
  64                 if ( $wgLocalMessageCache === false ) {
  65                         return;
  66                 }
  67
  68                 $filename = "$wgLocalMessageCache/messages-" . wfWikiID();
  69
  70                 wfSuppressWarnings();
  71                 $file = fopen( $filename, 'r' );
  72                 wfRestoreWarnings();
  73                 if ( !$file ) {
  74                         return;
  75                 }
  76
  77                 // Check to see if the file has the hash specified
  78                 $localHash = fread( $file, 32 );
  79                 if ( $hash == $localHash ) {
  80                         // All good, get the rest of it
  81                         $serialized = fread( $file, 10000000 );
  82                         $this->setCache( unserialize( $serialized ) );
  83                 }
  84                 fclose( $file );
  85         }
  86
  87         /**
  88          * Save the cache to a local file
  89          */
  90         function saveToLocal( $serialized, $hash ) {
  91                 global $wgLocalMessageCache;
  92
  93                 if ( $wgLocalMessageCache === false ) {
  94                         return;
  95                 }
  96
  97                 $filename = "$wgLocalMessageCache/messages-" . wfWikiID();
  98                 $oldUmask = umask( 0 );
  99                 wfMkdirParents( $wgLocalMessageCache, 0777 );
 100                 umask( $oldUmask );
 101
 102                 $file = fopen( $filename, 'w' );
 103                 if ( !$file ) {
 104                         wfDebug( "Unable to open local cache file for writing\n" );
 105                         return;
 106                 }
 107
 108                 fwrite( $file, $hash . $serialized );
 109                 fclose( $file );
 110                 @chmod( $filename, 0666 );
 111         }
 112
 113         function loadFromScript( $hash ) {
 114                 global $wgLocalMessageCache;
 115                 if ( $wgLocalMessageCache === false ) {
 116                         return;
 117                 }
 118
 119                 $filename = "$wgLocalMessageCache/messages-" . wfWikiID();
 120
 121                 wfSuppressWarnings();
 122                 $file = fopen( $filename, 'r' );
 123                 wfRestoreWarnings();
 124                 if ( !$file ) {
 125                         return;
 126                 }
 127                 $localHash=substr(fread($file,40),8);
 128                 fclose($file);
 129                 if ($hash!=$localHash) {
 130                         return;
 131                 }
 132                 require("$wgLocalMessageCache/messages-" . wfWikiID());
 133                 $this->setCache( $this->mCache);
 134         }
 135
 136         function saveToScript($array, $hash) {
 137                 global $wgLocalMessageCache;
 138                 if ( $wgLocalMessageCache === false ) {
 139                         return;
 140                 }
 141
 142                 $filename = "$wgLocalMessageCache/messages-" . wfWikiID();
 143                 $oldUmask = umask( 0 );
 144                 wfMkdirParents( $wgLocalMessageCache, 0777 );
 145                 umask( $oldUmask );
 146                 $file = fopen( $filename.'.tmp', 'w');
 147                 fwrite($file,"<?php\n//$hash\n\n \$this->mCache = array(");
 148
 149                 foreach ($array as $key => $message) {
 150                         fwrite($file, "'". $this->escapeForScript($key).
 151                                 "' => '" . $this->escapeForScript($message).
 152                                 "',\n");
 153                 }
 154                 fwrite($file,");\n?>");
 155                 fclose($file);
 156                 rename($filename.'.tmp',$filename);
 157         }
 158
 159         function escapeForScript($string) {
 160                 $string = str_replace( '\\', '\\\\', $string );
 161                 $string = str_replace( '\'', '\\\'', $string );
 162                 return $string;
 163         }
 164
 165         /**
 166          * Set the cache to $cache, if it is valid. Otherwise set the cache to false.
 167          */
 168         function setCache( $cache ) {
 169                 if ( isset( $cache['VERSION'] ) && $cache['VERSION'] == MSG_CACHE_VERSION ) {
 170                         $this->mCache = $cache;
 171                 } else {
 172                         $this->mCache = false;
 173                 }
 174         }
 175
 176         /**
 177          * Loads messages either from memcached or the database, if not disabled
 178          * On error, quietly switches to a fallback mode
 179          * Returns false for a reportable error, true otherwise
 180          */
 181         function load() {
 182                 global $wgLocalMessageCache, $wgLocalMessageCacheSerialized;
 183
 184                 if ( $this->mDisable ) {
 185                         static $shownDisabled = false;
 186                         if ( !$shownDisabled ) {
 187                                 wfDebug( "MessageCache::load(): disabled\n" );
 188                                 $shownDisabled = true;
 189                         }
 190                         return true;
 191                 }
 192                 if ( !$this->mUseCache ) {
 193                         $this->mDeferred = false;
 194                         return true;
 195                 }
 196
 197                 $fname = 'MessageCache::load';
 198                 wfProfileIn( $fname );
 199                 $success = true;
 200
 201                 $this->mCache = false;
 202
 203                 # Try local cache
 204                 wfProfileIn( $fname.'-fromlocal' );
 205                 $hash = $this->mMemc->get( "{$this->mMemcKey}-hash" );
 206                 if ( $hash ) {
 207                         if ($wgLocalMessageCacheSerialized) {
 208                                 $this->loadFromLocal( $hash );
 209                         } else {
 210                                 $this->loadFromScript( $hash );
 211                         }
 212                         if ( $this->mCache ) {
 213                                 wfDebug( "MessageCache::load(): got from local cache\n" );
 214                         }
 215                 }
 216                 wfProfileOut( $fname.'-fromlocal' );
 217
 218                 # Try memcached
 219                 if ( !$this->mCache ) {
 220                         wfProfileIn( $fname.'-fromcache' );
 221                         $this->setCache( $this->mMemc->get( $this->mMemcKey ) );
 222                         if ( $this->mCache ) {
 223                                 wfDebug( "MessageCache::load(): got from global cache\n" );
 224                                 # Save to local cache
 225                                 if ( $wgLocalMessageCache !== false ) {
 226                                         $serialized = serialize( $this->mCache );
 227                                         if ( !$hash ) {
 228                                                 $hash = md5( $serialized );
 229                                                 $this->mMemc->set( "{$this->mMemcKey}-hash", $hash, $this->mExpiry );
 230                                         }
 231                                         if ($wgLocalMessageCacheSerialized) {
 232                                                 $this->saveToLocal( $serialized,$hash );
 233                                         } else {
 234                                                 $this->saveToScript( $this->mCache, $hash );
 235                                         }
 236                                 }
 237                         }
 238                         wfProfileOut( $fname.'-fromcache' );
 239                 }
 240
 241
 242                 # If there's nothing in memcached, load all the messages from the database
 243                 if ( !$this->mCache ) {
 244                         wfDebug( "MessageCache::load(): cache is empty\n" );
 245                         $this->lock();
 246                         # Other threads don't need to load the messages if another thread is doing it.
 247                         $success = $this->mMemc->add( $this->mMemcKey.'-status', "loading", MSG_LOAD_TIMEOUT );
 248                         if ( $success ) {
 249                                 wfProfileIn( $fname.'-load' );
 250                                 wfDebug( "MessageCache::load(): loading all messages from DB\n" );
 251                                 $this->loadFromDB();
 252                                 wfProfileOut( $fname.'-load' );
 253
 254                                 # Save in memcached
 255                                 # Keep trying if it fails, this is kind of important
 256                                 wfProfileIn( $fname.'-save' );
 257                                 for ($i=0; $i<20 &&
 258                                                    !$this->mMemc->set( $this->mMemcKey, $this->mCache, $this->mExpiry );
 259                                          $i++ ) {
 260                                         usleep(mt_rand(500000,1500000));
 261                                 }
 262
 263                                 # Save to local cache
 264                                 if ( $wgLocalMessageCache !== false ) {
 265                                         $serialized = serialize( $this->mCache );
 266                                         $hash = md5( $serialized );
 267                                         $this->mMemc->set( "{$this->mMemcKey}-hash", $hash, $this->mExpiry );
 268                                         if ($wgLocalMessageCacheSerialized) {
 269                                                 $this->saveToLocal( $serialized,$hash );
 270                                         } else {
 271                                                 $this->saveToScript( $this->mCache, $hash );
 272                                         }
 273                                 }
 274
 275                                 wfProfileOut( $fname.'-save' );
 276                                 if ( $i == 20 ) {
 277                                         $this->mMemc->set( $this->mMemcKey.'-status', 'error', 60*5 );
 278                                         wfDebug( "MemCached set error in MessageCache: restart memcached server!\n" );
 279                                 } else {
 280                                         $this->mMemc->delete( $this->mMemcKey.'-status' );
 281                                 }
 282                         }
 283                         $this->unlock();
 284                 }
 285
 286                 if ( !is_array( $this->mCache ) ) {
 287                         wfDebug( "MessageCache::load(): unable to load cache, disabled\n" );
 288                         $this->mDisable = true;
 289                         $this->mCache = false;
 290                 }
 291                 wfProfileOut( $fname );
 292                 $this->mDeferred = false;
 293                 return $success;
 294         }
 295
 296         /**
 297          * Loads all or main part of cacheable messages from the database
 298          */
 299         function loadFromDB() {
 300                 global $wgMaxMsgCacheEntrySize;
 301
 302                 wfProfileIn( __METHOD__ );
 303                 $dbr = wfGetDB( DB_SLAVE );
 304                 $this->mCache = array();
 305
 306                 # Load titles for all oversized pages in the MediaWiki namespace
 307                 $res = $dbr->select( 'page', 'page_title',
 308                         array(
 309                                 'page_len > ' . intval( $wgMaxMsgCacheEntrySize ),
 310                                 'page_is_redirect' => 0,
 311                                 'page_namespace' => NS_MEDIAWIKI,
 312                         ),
 313                         __METHOD__ );
 314                 while ( $row = $dbr->fetchObject( $res ) ) {
 315                         $this->mCache[$row->page_title] = '!TOO BIG';
 316                 }
 317                 $dbr->freeResult( $res );
 318
 319                 # Load text for the remaining pages
 320                 $res = $dbr->select( array( 'page', 'revision', 'text' ),
 321                         array( 'page_title', 'old_text', 'old_flags' ),
 322                         array(
 323                                 'page_is_redirect' => 0,
 324                                 'page_namespace' => NS_MEDIAWIKI,
 325                                 'page_latest=rev_id',
 326                                 'rev_text_id=old_id',
 327                                 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize ) ),
 328                         __METHOD__ );
 329
 330                 for ( $row = $dbr->fetchObject( $res ); $row; $row = $dbr->fetchObject( $res ) ) {
 331                         $this->mCache[$row->page_title] = ' ' . Revision::getRevisionText( $row );
 332                 }
 333                 $this->mCache['VERSION'] = MSG_CACHE_VERSION;
 334                 $dbr->freeResult( $res );
 335                 wfProfileOut( __METHOD__ );
 336         }
 337
 338         /**
 339          * Not really needed anymore
 340          */
 341         function getKeys() {
 342                 global $wgContLang;
 343                 if ( !$this->mKeys ) {
 344                         $this->mKeys = array();
 345                         $allMessages = Language::getMessagesFor( 'en' );
 346                         foreach ( $allMessages as $key => $unused ) {
 347                                 $title = $wgContLang->ucfirst( $key );
 348                                 array_push( $this->mKeys, $title );
 349                         }
 350                 }
 351                 return $this->mKeys;
 352         }
 353
 354         function replace( $title, $text ) {
 355                 global $wgLocalMessageCache, $wgLocalMessageCacheSerialized, $parserMemc;
 356                 global $wgMaxMsgCacheEntrySize;
 357
 358                 wfProfileIn( __METHOD__ );
 359                 $this->lock();
 360                 $this->load();
 361                 $parserMemc->delete(wfMemcKey('sidebar'));
 362                 if ( is_array( $this->mCache ) ) {
 363                         if ( $text === false ) {
 364                                 # Article was deleted
 365                                 unset( $this->mCache[$title] );
 366                                 $this->mMemc->delete( "$this->mMemcKey:{$title}" );
 367                         } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 368                                 $this->mCache[$title] = '!TOO BIG';
 369                                 $this->mMemc->set( "$this->mMemcKey:{$title}", ' '.$text, $this->mExpiry );
 370                         } else {
 371                                 $this->mCache[$title] = ' ' . $text;
 372                                 $this->mMemc->delete( "$this->mMemcKey:{$title}" );
 373                         }
 374                         $this->mMemc->set( $this->mMemcKey, $this->mCache, $this->mExpiry );
 375
 376                         # Save to local cache
 377                         if ( $wgLocalMessageCache !== false ) {
 378                                 $serialized = serialize( $this->mCache );
 379                                 $hash = md5( $serialized );
 380                                 $this->mMemc->set( "{$this->mMemcKey}-hash", $hash, $this->mExpiry );
 381                                 if ($wgLocalMessageCacheSerialized) {
 382                                         $this->saveToLocal( $serialized,$hash );
 383                                 } else {
 384                                         $this->saveToScript( $this->mCache, $hash );
 385                                 }
 386                         }
 387                 }
 388                 $this->unlock();
 389                 wfProfileOut( __METHOD__ );
 390         }
 391
 392         /**
 393          * Returns success
 394          * Represents a write lock on the messages key
 395          */
 396         function lock() {
 397                 if ( !$this->mUseCache ) {
 398                         return true;
 399                 }
 400
 401                 $lockKey = $this->mMemcKey . 'lock';
 402                 for ($i=0; $i < MSG_WAIT_TIMEOUT && !$this->mMemc->add( $lockKey, 1, MSG_LOCK_TIMEOUT ); $i++ ) {
 403                         sleep(1);
 404                 }
 405
 406                 return $i >= MSG_WAIT_TIMEOUT;
 407         }
 408
 409         function unlock() {
 410                 if ( !$this->mUseCache ) {
 411                         return;
 412                 }
 413
 414                 $lockKey = $this->mMemcKey . 'lock';
 415                 $this->mMemc->delete( $lockKey );
 416         }
 417
 418         /**
 419          * Get a message from either the content language or the user language.
 420          *
 421          * @param string $key The message cache key
 422          * @param bool $useDB Get the message from the DB, false to use only the localisation
 423          * @param bool $forContent Get the message from the content language rather than the
 424          *                         user language
 425          * @param bool $isFullKey Specifies whether $key is a two part key "lang/msg".
 426          */
 427         function get( $key, $useDB = true, $forContent = true, $isFullKey = false ) {
 428                 global $wgContLanguageCode, $wgContLang, $wgLang;
 429                 if( $forContent ) {
 430                         $lang =& $wgContLang;
 431                 } else {
 432                         $lang =& $wgLang;
 433                 }
 434                 $langcode = $lang->getCode();
 435                 # If uninitialised, someone is trying to call this halfway through Setup.php
 436                 if( !$this->mInitialised ) {
 437                         return '&lt;' . htmlspecialchars($key) . '&gt;';
 438                 }
 439                 # If cache initialization was deferred, start it now.
 440                 if( $this->mDeferred && !$this->mDisable && $useDB ) {
 441                         $this->load();
 442                 }
 443
 444                 $message = false;
 445
 446                 # Normalise title-case input
 447                 $lckey = $wgContLang->lcfirst( $key );
 448                 $lckey = str_replace( ' ', '_', $lckey );
 449
 450                 # Try the MediaWiki namespace
 451                 if( !$this->mDisable && $useDB ) {
 452                         $title = $wgContLang->ucfirst( $lckey );
 453                         if(!$isFullKey && ($langcode != $wgContLanguageCode) ) {
 454                                 $title .= '/' . $langcode;
 455                         }
 456                         $message = $this->getMsgFromNamespace( $title );
 457                 }
 458                 # Try the extension array
 459                 if( $message === false && isset( $this->mExtensionMessages[$langcode][$lckey] ) ) {
 460                         $message = $this->mExtensionMessages[$langcode][$lckey];
 461                 }
 462                 if ( $message === false && isset( $this->mExtensionMessages['en'][$lckey] ) ) {
 463                         $message = $this->mExtensionMessages['en'][$lckey];
 464                 }
 465
 466                 # Try the array in the language object
 467                 if( $message === false ) {
 468                         #wfDebug( "Trying language object for message $key\n" );
 469                         wfSuppressWarnings();
 470                         $message = $lang->getMessage( $lckey );
 471                         wfRestoreWarnings();
 472                         if ( is_null( $message ) ) {
 473                                 $message = false;
 474                         }
 475                 }
 476
 477                 # Try the array of another language
 478                 if( $message === false && strpos( $lckey, '/' ) ) {
 479                         $message = explode( '/', $lckey );
 480                         if ( $message[1] ) {
 481                                 wfSuppressWarnings();
 482                                 $message = Language::getMessageFor( $message[0], $message[1] );
 483                                 wfRestoreWarnings();
 484                                 if ( is_null( $message ) ) {
 485                                         $message = false;
 486                                 }
 487                         } else {
 488                                 $message = false;
 489                         }
 490                 }
 491
 492                 # Is this a custom message? Try the default language in the db...
 493                 if( ($message === false || $message === '-' ) &&
 494                         !$this->mDisable && $useDB &&
 495                         !$isFullKey && ($langcode != $wgContLanguageCode) ) {
 496                         $message = $this->getMsgFromNamespace( $wgContLang->ucfirst( $lckey ) );
 497                 }
 498
 499                 # Final fallback
 500                 if( $message === false ) {
 501                         return '&lt;' . htmlspecialchars($key) . '&gt;';
 502                 }
 503                 return $message;
 504         }
 505
 506         /**
 507          * Get a message from the MediaWiki namespace, with caching. The key must
 508          * first be converted to two-part lang/msg form if necessary.
 509          *
 510          * @param string $title Message cache key with initial uppercase letter
 511          */
 512         function getMsgFromNamespace( $title ) {
 513                 $message = false;
 514                 $type = false;
 515
 516                 # Try the cache
 517                 if( $this->mUseCache && isset( $this->mCache[$title] ) ) {
 518                         $entry = $this->mCache[$title];
 519                         $type = substr( $entry, 0, 1 );
 520                         if ( $type == ' ' ) {
 521                                 return substr( $entry, 1 );
 522                         }
 523                 }
 524
 525                 # Call message hooks, in case they are defined
 526                 wfRunHooks('MessagesPreLoad', array( $title, &$message ) );
 527                 if ( $message !== false ) {
 528                         return $message;
 529                 }
 530
 531                 # If there is no cache entry and no placeholder, it doesn't exist
 532                 if ( $type != '!' && $message === false ) {
 533                         return false;
 534                 }
 535
 536                 $memcKey = $this->mMemcKey . ':' . $title;
 537
 538                 # Try the individual message cache
 539                 if ( $this->mUseCache ) {
 540                         $entry = $this->mMemc->get( $memcKey );
 541                         if ( $entry ) {
 542                                 $type = substr( $entry, 0, 1 );
 543
 544                                 if ( $type == ' ' ) {
 545                                         $message = substr( $entry, 1 );
 546                                         $this->mCache[$title] = $entry;
 547                                         return $message;
 548                                 } elseif ( $entry == '!NONEXISTENT' ) {
 549                                         return false;
 550                                 } else {
 551                                         # Corrupt/obsolete entry, delete it
 552                                         $this->mMemc->delete( $memcKey );
 553                                 }
 554
 555                         }
 556                 }
 557
 558                 # Try loading it from the DB
 559                 $revision = Revision::newFromTitle( Title::makeTitle( NS_MEDIAWIKI, $title ) );
 560                 if( $revision ) {
 561                         $message = $revision->getText();
 562                         if ($this->mUseCache) {
 563                                 $this->mCache[$title] = ' ' . $message;
 564                                 $this->mMemc->set( $memcKey, $message, $this->mExpiry );
 565                         }
 566                 } else {
 567                         # Negative caching
 568                         # Use some special text instead of false, because false gets converted to '' somewhere
 569                         $this->mMemc->set( $memcKey, '!NONEXISTENT', $this->mExpiry );
 570                         $this->mCache[$title] = false;
 571                 }
 572
 573                 return $message;
 574         }
 575
 576         function transform( $message, $interface = false ) {
 577                 global $wgParser;
 578                 if ( !$this->mParser && isset( $wgParser ) ) {
 579                         # Do some initialisation so that we don't have to do it twice
 580                         $wgParser->firstCallInit();
 581                         # Clone it and store it
 582                         $this->mParser = clone $wgParser;
 583                 }
 584                 if ( $this->mParser ) {
 585                         if( strpos( $message, '{{' ) !== false ) {
 586                                 $popts = $this->getParserOptions();
 587                                 $popts->setInterfaceMessage( $interface );
 588                                 $message = $this->mParser->transformMsg( $message, $popts );
 589                         }
 590                 }
 591                 return $message;
 592         }
 593
 594         function disable() { $this->mDisable = true; }
 595         function enable() { $this->mDisable = false; }
 596
 597         /** @deprecated */
 598         function disableTransform() {}
 599         function enableTransform() {}
 600         function setTransform( $x ) {}
 601         function getTransform() { return false; }
 602
 603         /**
 604          * Add a message to the cache
 605          *
 606          * @param mixed $key
 607          * @param mixed $value
 608          * @param string $lang The messages language, English by default
 609          */
 610         function addMessage( $key, $value, $lang = 'en' ) {
 611                 $this->mExtensionMessages[$lang][$key] = $value;
 612         }
 613
 614         /**
 615          * Add an associative array of message to the cache
 616          *
 617          * @param array $messages An associative array of key => values to be added
 618          * @param string $lang The messages language, English by default
 619          */
 620         function addMessages( $messages, $lang = 'en' ) {
 621                 wfProfileIn( __METHOD__ );
 622                 if ( isset( $this->mExtensionMessages[$lang] ) ) {
 623                         $this->mExtensionMessages[$lang] = $messages + $this->mExtensionMessages[$lang];
 624                 } else {
 625                         $this->mExtensionMessages[$lang] = $messages;
 626                 }
 627                 wfProfileOut( __METHOD__ );
 628         }
 629
 630         /**
 631          * Add a 2-D array of messages by lang. Useful for extensions.
 632          *
 633          * @param array $messages The array to be added
 634          */
 635         function addMessagesByLang( $messages ) {
 636                 wfProfileIn( __METHOD__ );
 637                 foreach ( $messages as $key => $value ) {
 638                         $this->addMessages( $value, $key );
 639                 }
 640                 wfProfileOut( __METHOD__ );
 641         }
 642
 643         /**
 644          * Get the extension messages for a specific language
 645          *
 646          * @param string $lang The messages language, English by default
 647          */
 648         function getExtensionMessagesFor( $lang = 'en' ) {
 649                 wfProfileIn( __METHOD__ );
 650                 $messages = array();
 651                 if ( isset( $this->mExtensionMessages[$lang] ) ) {
 652                         $messages = $this->mExtensionMessages[$lang];
 653                 }
 654                 if ( $lang != 'en' ) {
 655                         $messages = $messages + $this->mExtensionMessages['en'];
 656                 }
 657                 wfProfileOut( __METHOD__ );
 658                 return $messages;
 659         }
 660
 661         /**
 662          * Clear all stored messages. Mainly used after a mass rebuild.
 663          */
 664         function clear() {
 665                 global $wgLocalMessageCache;
 666                 if( $this->mUseCache ) {
 667                         # Global cache
 668                         $this->mMemc->delete( $this->mMemcKey );
 669                         # Invalidate all local caches
 670                         $this->mMemc->delete( "{$this->mMemcKey}-hash" );
 671                 }
 672         }
 673
 674         function loadAllMessages() {
 675                 global $wgExtensionMessagesFiles;
 676                 if ( $this->mAllMessagesLoaded ) {
 677                         return;
 678                 }
 679                 $this->mAllMessagesLoaded = true;
 680
 681                 # Some extensions will load their messages when you load their class file
 682                 wfLoadAllExtensions();
 683                 # Others will respond to this hook
 684                 wfRunHooks( 'LoadAllMessages' );
 685                 # Some register their messages in $wgExtensionMessagesFiles
 686                 foreach ( $wgExtensionMessagesFiles as $name => $file ) {
 687                         if ( $file ) {
 688                                 $this->loadMessagesFile( $file );
 689                                 $wgExtensionMessagesFiles[$name] = false;
 690                         }
 691                 }
 692                 # Still others will respond to neither, they are EVIL. We sometimes need to know!
 693         }
 694
 695         /**
 696          * Load messages from a given file
 697          */
 698         function loadMessagesFile( $filename ) {
 699                 $messages = $magicWords = false;
 700                 require( $filename );
 701
 702                 if ( $messages !== false ) {
 703                         $this->addMessagesByLang( $messages );
 704                 }
 705
 706                 if ( $magicWords !== false ) {
 707                         global $wgContLang;
 708                         $wgContLang->addMagicWordsByLang( $magicWords );
 709                 }
 710         }
 711 }