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, $wgLocalMessageCacheSerialized;
  62
  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                 if ( $wgLocalMessageCacheSerialized ) {
  77                         $localHash=substr(fread($file,40),8);
  78                         fclose($file);
  79                         if ($hash!=$localHash) {
  80                                 return;
  81                         }
  82
  83                         require("$wgLocalMessageCache/messages-" . wfWikiID());
  84                         $this->setCache( $this->mCache);
  85                 } else {
  86                         // Check to see if the file has the hash specified
  87                         $localHash = fread( $file, 32 );
  88                         if ( $hash === $localHash ) {
  89                                 // All good, get the rest of it
  90                                 $serialized = fread( $file, 20000000 );
  91                                 $this->setCache( unserialize( $serialized ) );
  92                         }
  93                         fclose( $file );
  94                 }
  95         }
  96
  97         /**
  98          * Save the cache to a local file
  99          */
 100         function saveToLocal( $serialized, $hash ) {
 101                 global $wgLocalMessageCache, $wgLocalMessageCacheSerialized;
 102
 103                 if ( $wgLocalMessageCache === false ) {
 104                         return;
 105                 }
 106
 107                 $filename = "$wgLocalMessageCache/messages-" . wfWikiID();
 108                 $oldUmask = umask( 0 );
 109                 wfMkdirParents( $wgLocalMessageCache, 0777 );
 110                 umask( $oldUmask );
 111
 112                 $file = fopen( $filename, 'w' );
 113                 if ( !$file ) {
 114                         wfDebug( "Unable to open local cache file for writing\n" );
 115                         return;
 116                 }
 117
 118                 fwrite( $file, $hash . $serialized );
 119                 fclose( $file );
 120                 @chmod( $filename, 0666 );
 121         }
 122
 123         function loadFromScript( $hash ) {
 124                 trigger_error( 'Use of ' . __METHOD__ . ' is deprecated', E_USER_NOTICE );
 125                 $this->loadFromLocal( $hash );
 126         }
 127
 128         function saveToScript($array, $hash) {
 129                 global $wgLocalMessageCache;
 130                 if ( $wgLocalMessageCache === false ) {
 131                         return;
 132                 }
 133
 134                 $filename = "$wgLocalMessageCache/messages-" . wfWikiID();
 135                 $oldUmask = umask( 0 );
 136                 wfMkdirParents( $wgLocalMessageCache, 0777 );
 137                 umask( $oldUmask );
 138                 $file = fopen( $filename.'.tmp', 'w');
 139                 fwrite($file,"<?php\n//$hash\n\n \$this->mCache = array(");
 140
 141                 foreach ($array as $key => $message) {
 142                         fwrite($file, "'". $this->escapeForScript($key).
 143                                 "' => '" . $this->escapeForScript($message).
 144                                 "',\n");
 145                 }
 146                 fwrite($file,");\n?>");
 147                 fclose($file);
 148                 rename($filename.'.tmp',$filename);
 149         }
 150
 151         function escapeForScript($string) {
 152                 $string = str_replace( '\\', '\\\\', $string );
 153                 $string = str_replace( '\'', '\\\'', $string );
 154                 return $string;
 155         }
 156
 157         /**
 158          * Set the cache to $cache, if it is valid. Otherwise set the cache to false.
 159          */
 160         function setCache( $cache ) {
 161                 if ( isset( $cache['VERSION'] ) && $cache['VERSION'] == MSG_CACHE_VERSION ) {
 162                         $this->mCache = $cache;
 163                 } else {
 164                         $this->mCache = false;
 165                 }
 166         }
 167
 168         /**
 169          * Loads messages either from memcached or the database, if not disabled
 170          * On error, quietly switches to a fallback mode
 171          * Returns false for a reportable error, true otherwise
 172          */
 173         function load() {
 174                 global $wgLocalMessageCache, $wgLocalMessageCacheSerialized;
 175
 176                 if ( $this->mDisable ) {
 177                         static $shownDisabled = false;
 178                         if ( !$shownDisabled ) {
 179                                 wfDebug( "MessageCache::load(): disabled\n" );
 180                                 $shownDisabled = true;
 181                         }
 182                         return true;
 183                 }
 184                 if ( !$this->mUseCache ) {
 185                         $this->mDeferred = false;
 186                         return true;
 187                 }
 188
 189                 $fname = 'MessageCache::load';
 190                 wfProfileIn( $fname );
 191                 $success = true;
 192
 193                 $this->mCache = false;
 194
 195                 # Try local cache
 196                 if ( $wgLocalMessageCache !== false ) {
 197                         wfProfileIn( $fname.'-fromlocal' );
 198                         $hash = $this->mMemc->get( "{$this->mMemcKey}-hash" );
 199                         if ( $hash ) {
 200                                 $this->loadFromLocal( $hash );
 201                                 if ( $this->mCache ) {
 202                                         wfDebug( "MessageCache::load(): got from local cache\n" );
 203                                 }
 204                         }
 205                         wfProfileOut( $fname.'-fromlocal' );
 206                 }
 207
 208                 # Try memcached
 209                 if ( !$this->mCache ) {
 210                         wfProfileIn( $fname.'-fromcache' );
 211                         $this->setCache( $this->mMemc->get( $this->mMemcKey ) );
 212                         if ( $this->mCache ) {
 213                                 wfDebug( "MessageCache::load(): got from global cache\n" );
 214                                 # Save to local cache
 215                                 if ( $wgLocalMessageCache !== false ) {
 216                                         $serialized = serialize( $this->mCache );
 217                                         if ( !$hash ) {
 218                                                 $hash = md5( $serialized );
 219                                                 $this->mMemc->set( "{$this->mMemcKey}-hash", $hash, $this->mExpiry );
 220                                         }
 221                                         if ($wgLocalMessageCacheSerialized) {
 222                                                 $this->saveToLocal( $serialized,$hash );
 223                                         } else {
 224                                                 $this->saveToScript( $this->mCache, $hash );
 225                                         }
 226                                 }
 227                         }
 228                         wfProfileOut( $fname.'-fromcache' );
 229                 }
 230
 231
 232                 # If there's nothing in memcached, load all the messages from the database
 233                 if ( !$this->mCache ) {
 234                         wfDebug( "MessageCache::load(): cache is empty\n" );
 235                         $this->lock();
 236                         # Other threads don't need to load the messages if another thread is doing it.
 237                         $success = $this->mMemc->add( $this->mMemcKey.'-status', "loading", MSG_LOAD_TIMEOUT );
 238                         if ( $success ) {
 239                                 wfProfileIn( $fname.'-load' );
 240                                 wfDebug( "MessageCache::load(): loading all messages from DB\n" );
 241                                 $this->loadFromDB();
 242                                 wfProfileOut( $fname.'-load' );
 243
 244                                 # Save in memcached
 245                                 # Keep trying if it fails, this is kind of important
 246                                 wfProfileIn( $fname.'-save' );
 247                                 for ($i=0; $i<20 &&
 248                                                    !$this->mMemc->set( $this->mMemcKey, $this->mCache, $this->mExpiry );
 249                                          $i++ ) {
 250                                         usleep(mt_rand(500000,1500000));
 251                                 }
 252
 253                                 # Save to local cache
 254                                 if ( $wgLocalMessageCache !== false ) {
 255                                         $serialized = serialize( $this->mCache );
 256                                         $hash = md5( $serialized );
 257                                         $this->mMemc->set( "{$this->mMemcKey}-hash", $hash, $this->mExpiry );
 258                                         if ($wgLocalMessageCacheSerialized) {
 259                                                 $this->saveToLocal( $serialized,$hash );
 260                                         } else {
 261                                                 $this->saveToScript( $this->mCache, $hash );
 262                                         }
 263                                 }
 264
 265                                 wfProfileOut( $fname.'-save' );
 266                                 if ( $i == 20 ) {
 267                                         $this->mMemc->set( $this->mMemcKey.'-status', 'error', 60*5 );
 268                                         wfDebug( "MemCached set error in MessageCache: restart memcached server!\n" );
 269                                 } else {
 270                                         $this->mMemc->delete( $this->mMemcKey.'-status' );
 271                                 }
 272                         }
 273                         $this->unlock();
 274                 }
 275
 276                 if ( !is_array( $this->mCache ) ) {
 277                         wfDebug( "MessageCache::load(): unable to load cache, disabled\n" );
 278                         $this->mDisable = true;
 279                         $this->mCache = false;
 280                 }
 281                 wfProfileOut( $fname );
 282                 $this->mDeferred = false;
 283                 return $success;
 284         }
 285
 286         /**
 287          * Loads all or main part of cacheable messages from the database
 288          */
 289         function loadFromDB() {
 290                 global $wgMaxMsgCacheEntrySize;
 291
 292                 wfProfileIn( __METHOD__ );
 293                 $dbr = wfGetDB( DB_SLAVE );
 294                 $this->mCache = array();
 295
 296                 # Load titles for all oversized pages in the MediaWiki namespace
 297                 $res = $dbr->select( 'page', 'page_title',
 298                         array(
 299                                 'page_len > ' . intval( $wgMaxMsgCacheEntrySize ),
 300                                 'page_is_redirect' => 0,
 301                                 'page_namespace' => NS_MEDIAWIKI,
 302                         ),
 303                         __METHOD__ );
 304                 while ( $row = $dbr->fetchObject( $res ) ) {
 305                         $this->mCache[$row->page_title] = '!TOO BIG';
 306                 }
 307                 $dbr->freeResult( $res );
 308
 309                 # Load text for the remaining pages
 310                 $res = $dbr->select( array( 'page', 'revision', 'text' ),
 311                         array( 'page_title', 'old_text', 'old_flags' ),
 312                         array(
 313                                 'page_is_redirect' => 0,
 314                                 'page_namespace' => NS_MEDIAWIKI,
 315                                 'page_latest=rev_id',
 316                                 'rev_text_id=old_id',
 317                                 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize ) ),
 318                         __METHOD__ );
 319
 320                 for ( $row = $dbr->fetchObject( $res ); $row; $row = $dbr->fetchObject( $res ) ) {
 321                         $this->mCache[$row->page_title] = ' ' . Revision::getRevisionText( $row );
 322                 }
 323                 $this->mCache['VERSION'] = MSG_CACHE_VERSION;
 324                 $dbr->freeResult( $res );
 325                 wfProfileOut( __METHOD__ );
 326         }
 327
 328         /**
 329          * Not really needed anymore
 330          */
 331         function getKeys() {
 332                 global $wgContLang;
 333                 if ( !$this->mKeys ) {
 334                         $this->mKeys = array();
 335                         $allMessages = Language::getMessagesFor( 'en' );
 336                         foreach ( $allMessages as $key => $unused ) {
 337                                 $title = $wgContLang->ucfirst( $key );
 338                                 array_push( $this->mKeys, $title );
 339                         }
 340                 }
 341                 return $this->mKeys;
 342         }
 343
 344         function replace( $title, $text ) {
 345                 global $wgLocalMessageCache, $wgLocalMessageCacheSerialized, $parserMemc;
 346                 global $wgMaxMsgCacheEntrySize;
 347
 348                 wfProfileIn( __METHOD__ );
 349                 $this->lock();
 350                 $this->load();
 351                 $parserMemc->delete(wfMemcKey('sidebar'));
 352                 if ( is_array( $this->mCache ) ) {
 353                         if ( $text === false ) {
 354                                 # Article was deleted
 355                                 unset( $this->mCache[$title] );
 356                                 $this->mMemc->delete( "$this->mMemcKey:{$title}" );
 357                         } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 358                                 $this->mCache[$title] = '!TOO BIG';
 359                                 $this->mMemc->set( "$this->mMemcKey:{$title}", ' '.$text, $this->mExpiry );
 360                         } else {
 361                                 $this->mCache[$title] = ' ' . $text;
 362                                 $this->mMemc->delete( "$this->mMemcKey:{$title}" );
 363                         }
 364                         $this->mMemc->set( $this->mMemcKey, $this->mCache, $this->mExpiry );
 365
 366                         # Save to local cache
 367                         if ( $wgLocalMessageCache !== false ) {
 368                                 $serialized = serialize( $this->mCache );
 369                                 $hash = md5( $serialized );
 370                                 $this->mMemc->set( "{$this->mMemcKey}-hash", $hash, $this->mExpiry );
 371                                 if ($wgLocalMessageCacheSerialized) {
 372                                         $this->saveToLocal( $serialized,$hash );
 373                                 } else {
 374                                         $this->saveToScript( $this->mCache, $hash );
 375                                 }
 376                         }
 377                 }
 378                 $this->unlock();
 379                 wfProfileOut( __METHOD__ );
 380         }
 381
 382         /**
 383          * Returns success
 384          * Represents a write lock on the messages key
 385          */
 386         function lock() {
 387                 if ( !$this->mUseCache ) {
 388                         return true;
 389                 }
 390
 391                 $lockKey = $this->mMemcKey . 'lock';
 392                 for ($i=0; $i < MSG_WAIT_TIMEOUT && !$this->mMemc->add( $lockKey, 1, MSG_LOCK_TIMEOUT ); $i++ ) {
 393                         sleep(1);
 394                 }
 395
 396                 return $i >= MSG_WAIT_TIMEOUT;
 397         }
 398
 399         function unlock() {
 400                 if ( !$this->mUseCache ) {
 401                         return;
 402                 }
 403
 404                 $lockKey = $this->mMemcKey . 'lock';
 405                 $this->mMemc->delete( $lockKey );
 406         }
 407
 408         /**
 409          * Get a message from either the content language or the user language.
 410          *
 411          * @param string $key The message cache key
 412          * @param bool $useDB Get the message from the DB, false to use only the localisation
 413          * @param bool $forContent Get the message from the content language rather than the
 414          *                         user language
 415          * @param bool $isFullKey Specifies whether $key is a two part key "lang/msg".
 416          */
 417         function get( $key, $useDB = true, $forContent = true, $isFullKey = false ) {
 418                 global $wgContLanguageCode, $wgContLang, $wgLang;
 419                 if( $forContent ) {
 420                         $lang =& $wgContLang;
 421                 } else {
 422                         $lang =& $wgLang;
 423                 }
 424                 $langcode = $lang->getCode();
 425                 # If uninitialised, someone is trying to call this halfway through Setup.php
 426                 if( !$this->mInitialised ) {
 427                         return '&lt;' . htmlspecialchars($key) . '&gt;';
 428                 }
 429                 # If cache initialization was deferred, start it now.
 430                 if( $this->mDeferred && !$this->mDisable && $useDB ) {
 431                         $this->load();
 432                 }
 433
 434                 $message = false;
 435
 436                 # Normalise title-case input
 437                 $lckey = $wgContLang->lcfirst( $key );
 438                 $lckey = str_replace( ' ', '_', $lckey );
 439
 440                 # Try the MediaWiki namespace
 441                 if( !$this->mDisable && $useDB ) {
 442                         $title = $wgContLang->ucfirst( $lckey );
 443                         if(!$isFullKey && ($langcode != $wgContLanguageCode) ) {
 444                                 $title .= '/' . $langcode;
 445                         }
 446                         $message = $this->getMsgFromNamespace( $title );
 447                 }
 448                 # Try the extension array
 449                 if( $message === false && isset( $this->mExtensionMessages[$langcode][$lckey] ) ) {
 450                         $message = $this->mExtensionMessages[$langcode][$lckey];
 451                 }
 452                 if ( $message === false && isset( $this->mExtensionMessages['en'][$lckey] ) ) {
 453                         $message = $this->mExtensionMessages['en'][$lckey];
 454                 }
 455
 456                 # Try the array in the language object
 457                 if( $message === false ) {
 458                         #wfDebug( "Trying language object for message $key\n" );
 459                         wfSuppressWarnings();
 460                         $message = $lang->getMessage( $lckey );
 461                         wfRestoreWarnings();
 462                         if ( is_null( $message ) ) {
 463                                 $message = false;
 464                         }
 465                 }
 466
 467                 # Try the array of another language
 468                 $pos = strrpos( $lckey, '/' );
 469                 if( $message === false && $pos !== false) {
 470                         $mkey = substr( $lckey, 0, $pos );
 471                         $code = substr( $lckey, $pos+1 );
 472                         if ( $code ) {
 473                                 $validCodes = array_keys( Language::getLanguageNames() );
 474                                 if ( in_array( $code, $validCodes ) ) {
 475                                         $message = Language::getMessageFor( $mkey, $code );
 476                                         if ( is_null( $message ) ) {
 477                                                 $message = false;
 478                                         }
 479                                 } else {
 480                                         wfDebug( __METHOD__ . ": Invalid code $code for $mkey/$code, not trying messages array\n" );
 481                                 }
 482                         }
 483                 }
 484
 485                 # Is this a custom message? Try the default language in the db...
 486                 if( ($message === false || $message === '-' ) &&
 487                         !$this->mDisable && $useDB &&
 488                         !$isFullKey && ($langcode != $wgContLanguageCode) ) {
 489                         $message = $this->getMsgFromNamespace( $wgContLang->ucfirst( $lckey ) );
 490                 }
 491
 492                 # Final fallback
 493                 if( $message === false ) {
 494                         return '&lt;' . htmlspecialchars($key) . '&gt;';
 495                 }
 496                 return $message;
 497         }
 498
 499         /**
 500          * Get a message from the MediaWiki namespace, with caching. The key must
 501          * first be converted to two-part lang/msg form if necessary.
 502          *
 503          * @param string $title Message cache key with initial uppercase letter
 504          */
 505         function getMsgFromNamespace( $title ) {
 506                 $message = false;
 507                 $type = false;
 508
 509                 # Try the cache
 510                 if( $this->mUseCache && isset( $this->mCache[$title] ) ) {
 511                         $entry = $this->mCache[$title];
 512                         $type = substr( $entry, 0, 1 );
 513                         if ( $type == ' ' ) {
 514                                 return substr( $entry, 1 );
 515                         }
 516                 }
 517
 518                 # Call message hooks, in case they are defined
 519                 wfRunHooks('MessagesPreLoad', array( $title, &$message ) );
 520                 if ( $message !== false ) {
 521                         return $message;
 522                 }
 523
 524                 # If there is no cache entry and no placeholder, it doesn't exist
 525                 if ( $type != '!' && $message === false ) {
 526                         return false;
 527                 }
 528
 529                 $memcKey = $this->mMemcKey . ':' . $title;
 530
 531                 # Try the individual message cache
 532                 if ( $this->mUseCache ) {
 533                         $entry = $this->mMemc->get( $memcKey );
 534                         if ( $entry ) {
 535                                 $type = substr( $entry, 0, 1 );
 536
 537                                 if ( $type == ' ' ) {
 538                                         $message = substr( $entry, 1 );
 539                                         $this->mCache[$title] = $entry;
 540                                         return $message;
 541                                 } elseif ( $entry == '!NONEXISTENT' ) {
 542                                         return false;
 543                                 } else {
 544                                         # Corrupt/obsolete entry, delete it
 545                                         $this->mMemc->delete( $memcKey );
 546                                 }
 547
 548                         }
 549                 }
 550
 551                 # Try loading it from the DB
 552                 $revision = Revision::newFromTitle( Title::makeTitle( NS_MEDIAWIKI, $title ) );
 553                 if( $revision ) {
 554                         $message = $revision->getText();
 555                         if ($this->mUseCache) {
 556                                 $this->mCache[$title] = ' ' . $message;
 557                                 $this->mMemc->set( $memcKey, $message, $this->mExpiry );
 558                         }
 559                 } else {
 560                         # Negative caching
 561                         # Use some special text instead of false, because false gets converted to '' somewhere
 562                         $this->mMemc->set( $memcKey, '!NONEXISTENT', $this->mExpiry );
 563                         $this->mCache[$title] = false;
 564                 }
 565
 566                 return $message;
 567         }
 568
 569         function transform( $message, $interface = false ) {
 570                 global $wgParser;
 571                 if ( !$this->mParser && isset( $wgParser ) ) {
 572                         # Do some initialisation so that we don't have to do it twice
 573                         $wgParser->firstCallInit();
 574                         # Clone it and store it
 575                         $this->mParser = clone $wgParser;
 576                 }
 577                 if ( $this->mParser ) {
 578                         if( strpos( $message, '{{' ) !== false ) {
 579                                 $popts = $this->getParserOptions();
 580                                 $popts->setInterfaceMessage( $interface );
 581                                 $message = $this->mParser->transformMsg( $message, $popts );
 582                         }
 583                 }
 584                 return $message;
 585         }
 586
 587         function disable() { $this->mDisable = true; }
 588         function enable() { $this->mDisable = false; }
 589
 590         /** @deprecated */
 591         function disableTransform() {}
 592         function enableTransform() {}
 593         function setTransform( $x ) {}
 594         function getTransform() { return false; }
 595
 596         /**
 597          * Add a message to the cache
 598          *
 599          * @param mixed $key
 600          * @param mixed $value
 601          * @param string $lang The messages language, English by default
 602          */
 603         function addMessage( $key, $value, $lang = 'en' ) {
 604                 $this->mExtensionMessages[$lang][$key] = $value;
 605         }
 606
 607         /**
 608          * Add an associative array of message to the cache
 609          *
 610          * @param array $messages An associative array of key => values to be added
 611          * @param string $lang The messages language, English by default
 612          */
 613         function addMessages( $messages, $lang = 'en' ) {
 614                 wfProfileIn( __METHOD__ );
 615                 if ( !is_array( $messages ) ) {
 616                         throw new MWException( __METHOD__.': Invalid message array' );
 617                 }
 618                 if ( isset( $this->mExtensionMessages[$lang] ) ) {
 619                         $this->mExtensionMessages[$lang] = $messages + $this->mExtensionMessages[$lang];
 620                 } else {
 621                         $this->mExtensionMessages[$lang] = $messages;
 622                 }
 623                 wfProfileOut( __METHOD__ );
 624         }
 625
 626         /**
 627          * Add a 2-D array of messages by lang. Useful for extensions.
 628          *
 629          * @param array $messages The array to be added
 630          */
 631         function addMessagesByLang( $messages ) {
 632                 wfProfileIn( __METHOD__ );
 633                 foreach ( $messages as $key => $value ) {
 634                         $this->addMessages( $value, $key );
 635                 }
 636                 wfProfileOut( __METHOD__ );
 637         }
 638
 639         /**
 640          * Get the extension messages for a specific language. Only English, interface
 641          * and content language are guaranteed to be loaded.
 642          *
 643          * @param string $lang The messages language, English by default
 644          */
 645         function getExtensionMessagesFor( $lang = 'en' ) {
 646                 wfProfileIn( __METHOD__ );
 647                 $messages = array();
 648                 if ( isset( $this->mExtensionMessages[$lang] ) ) {
 649                         $messages = $this->mExtensionMessages[$lang];
 650                 }
 651                 if ( $lang != 'en' ) {
 652                         $messages = $messages + $this->mExtensionMessages['en'];
 653                 }
 654                 wfProfileOut( __METHOD__ );
 655                 return $messages;
 656         }
 657
 658         /**
 659          * Clear all stored messages. Mainly used after a mass rebuild.
 660          */
 661         function clear() {
 662                 global $wgLocalMessageCache;
 663                 if( $this->mUseCache ) {
 664                         # Global cache
 665                         $this->mMemc->delete( $this->mMemcKey );
 666                         # Invalidate all local caches
 667                         $this->mMemc->delete( "{$this->mMemcKey}-hash" );
 668                 }
 669         }
 670
 671         function loadAllMessages() {
 672                 global $wgExtensionMessagesFiles;
 673                 if ( $this->mAllMessagesLoaded ) {
 674                         return;
 675                 }
 676                 $this->mAllMessagesLoaded = true;
 677
 678                 # Some extensions will load their messages when you load their class file
 679                 wfLoadAllExtensions();
 680                 # Others will respond to this hook
 681                 wfRunHooks( 'LoadAllMessages' );
 682                 # Some register their messages in $wgExtensionMessagesFiles
 683                 foreach ( $wgExtensionMessagesFiles as $name => $file ) {
 684                         if ( $file ) {
 685                                 $this->loadMessagesFile( $file );
 686                                 $wgExtensionMessagesFiles[$name] = false;
 687                         }
 688                 }
 689                 # Still others will respond to neither, they are EVIL. We sometimes need to know!
 690         }
 691
 692         /**
 693          * Load messages from a given file
 694          */
 695         function loadMessagesFile( $filename ) {
 696                 global $wgLang, $wgContLang;
 697                 $messages = $magicWords = false;
 698                 require( $filename );
 699
 700                 /*
 701                  * Load only languages that are usually used, and merge all fallbacks,
 702                  * except English.
 703                  */
 704                 $langs = array_unique( array( 'en', $wgContLang->getCode(), $wgLang->getCode() ) );
 705                 foreach( $langs as $code ) {
 706                         $fbcode = $code;
 707                         $mergedMessages = array();
 708                         do {
 709                                 if ( isset($messages[$fbcode]) ) {
 710                                         $mergedMessages += $messages[$fbcode];
 711                                 }
 712                                 $fbcode = Language::getFallbackfor( $fbcode );
 713                         } while( $fbcode && $fbcode !== 'en' );
 714
 715                         if ( !empty($mergedMessages) )
 716                                 $this->addMessages( $mergedMessages, $code );
 717                 }
 718
 719                 if ( $magicWords !== false ) {
 720                         global $wgContLang;
 721                         $wgContLang->addMagicWordsByLang( $magicWords );
 722                 }
 723         }
 724 }