includes/MessageCache.php

   1 <?php
   2 /**
   3  * @file
   4  * @ingroup 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  * @ingroup Cache
  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                         // 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 = '';
  82                                 while ( !feof( $file ) ) {
  83                                         $serialized .= fread( $file, 100000 );
  84                                 }
  85                                 $this->setCache( unserialize( $serialized ) );
  86                         }
  87                         fclose( $file );
  88                 } else {
  89                         $localHash=substr(fread($file,40),8);
  90                         fclose($file);
  91                         if ($hash!=$localHash) {
  92                                 return;
  93                         }
  94
  95                         require("$wgLocalMessageCache/messages-" . wfWikiID());
  96                         $this->setCache( $this->mCache);
  97                 }
  98         }
  99
 100         /**
 101          * Save the cache to a local file
 102          */
 103         function saveToLocal( $serialized, $hash ) {
 104                 global $wgLocalMessageCache, $wgLocalMessageCacheSerialized;
 105
 106                 if ( $wgLocalMessageCache === false ) {
 107                         return;
 108                 }
 109
 110                 $filename = "$wgLocalMessageCache/messages-" . wfWikiID();
 111                 $oldUmask = umask( 0 );
 112                 wfMkdirParents( $wgLocalMessageCache, 0777 );
 113                 umask( $oldUmask );
 114
 115                 $file = fopen( $filename, 'w' );
 116                 if ( !$file ) {
 117                         wfDebug( "Unable to open local cache file for writing\n" );
 118                         return;
 119                 }
 120
 121                 fwrite( $file, $hash . $serialized );
 122                 fclose( $file );
 123                 @chmod( $filename, 0666 );
 124         }
 125
 126         function loadFromScript( $hash ) {
 127                 wfDeprecated( __METHOD__ );
 128                 $this->loadFromLocal( $hash );
 129         }
 130
 131         function saveToScript($array, $hash) {
 132                 global $wgLocalMessageCache;
 133                 if ( $wgLocalMessageCache === false ) {
 134                         return;
 135                 }
 136
 137                 $filename = "$wgLocalMessageCache/messages-" . wfWikiID();
 138                 $oldUmask = umask( 0 );
 139                 wfMkdirParents( $wgLocalMessageCache, 0777 );
 140                 umask( $oldUmask );
 141                 $file = fopen( $filename.'.tmp', 'w');
 142                 fwrite($file,"<?php\n//$hash\n\n \$this->mCache = array(");
 143
 144                 foreach ($array as $key => $message) {
 145                         fwrite($file, "'". $this->escapeForScript($key).
 146                                 "' => '" . $this->escapeForScript($message).
 147                                 "',\n");
 148                 }
 149                 fwrite($file,");\n?>");
 150                 fclose($file);
 151                 rename($filename.'.tmp',$filename);
 152         }
 153
 154         function escapeForScript($string) {
 155                 $string = str_replace( '\\', '\\\\', $string );
 156                 $string = str_replace( '\'', '\\\'', $string );
 157                 return $string;
 158         }
 159
 160         /**
 161          * Set the cache to $cache, if it is valid. Otherwise set the cache to false.
 162          */
 163         function setCache( $cache ) {
 164                 if ( isset( $cache['VERSION'] ) && $cache['VERSION'] == MSG_CACHE_VERSION ) {
 165                         $this->mCache = $cache;
 166                 } else {
 167                         $this->mCache = false;
 168                 }
 169         }
 170
 171         /**
 172          * Loads messages either from memcached or the database, if not disabled
 173          * On error, quietly switches to a fallback mode
 174          * Returns false for a reportable error, true otherwise
 175          */
 176         function load() {
 177                 global $wgLocalMessageCache, $wgLocalMessageCacheSerialized;
 178
 179                 if ( $this->mDisable ) {
 180                         static $shownDisabled = false;
 181                         if ( !$shownDisabled ) {
 182                                 wfDebug( "MessageCache::load(): disabled\n" );
 183                                 $shownDisabled = true;
 184                         }
 185                         return true;
 186                 }
 187                 if ( !$this->mUseCache ) {
 188                         $this->mDeferred = false;
 189                         return true;
 190                 }
 191
 192                 $fname = 'MessageCache::load';
 193                 wfProfileIn( $fname );
 194                 $success = true;
 195
 196                 $this->mCache = false;
 197
 198                 # Try local cache
 199                 if ( $wgLocalMessageCache !== false ) {
 200                         wfProfileIn( $fname.'-fromlocal' );
 201                         $hash = $this->mMemc->get( "{$this->mMemcKey}-hash" );
 202                         if ( $hash ) {
 203                                 $this->loadFromLocal( $hash );
 204                                 if ( $this->mCache ) {
 205                                         wfDebug( "MessageCache::load(): got from local cache\n" );
 206                                 }
 207                         }
 208                         wfProfileOut( $fname.'-fromlocal' );
 209                 }
 210
 211                 # Try memcached
 212                 if ( !$this->mCache ) {
 213                         wfProfileIn( $fname.'-fromcache' );
 214                         $this->setCache( $this->mMemc->get( $this->mMemcKey ) );
 215                         if ( $this->mCache ) {
 216                                 wfDebug( "MessageCache::load(): got from global cache\n" );
 217                                 # Save to local cache
 218                                 if ( $wgLocalMessageCache !== false ) {
 219                                         $serialized = serialize( $this->mCache );
 220                                         if ( !$hash ) {
 221                                                 $hash = md5( $serialized );
 222                                                 $this->mMemc->set( "{$this->mMemcKey}-hash", $hash, $this->mExpiry );
 223                                         }
 224                                         if ($wgLocalMessageCacheSerialized) {
 225                                                 $this->saveToLocal( $serialized,$hash );
 226                                         } else {
 227                                                 $this->saveToScript( $this->mCache, $hash );
 228                                         }
 229                                 }
 230                         }
 231                         wfProfileOut( $fname.'-fromcache' );
 232                 }
 233
 234
 235                 # If there's nothing in memcached, load all the messages from the database
 236                 if ( !$this->mCache ) {
 237                         wfDebug( "MessageCache::load(): cache is empty\n" );
 238                         $this->lock();
 239                         # Other threads don't need to load the messages if another thread is doing it.
 240                         $success = $this->mMemc->add( $this->mMemcKey.'-status', "loading", MSG_LOAD_TIMEOUT );
 241                         if ( $success ) {
 242                                 wfProfileIn( $fname.'-load' );
 243                                 wfDebug( "MessageCache::load(): loading all messages from DB\n" );
 244                                 $this->loadFromDB();
 245                                 wfProfileOut( $fname.'-load' );
 246
 247                                 # Save in memcached
 248                                 # Keep trying if it fails, this is kind of important
 249                                 wfProfileIn( $fname.'-save' );
 250                                 for ($i=0; $i<20 &&
 251                                                    !$this->mMemc->set( $this->mMemcKey, $this->mCache, $this->mExpiry );
 252                                          $i++ ) {
 253                                         usleep(mt_rand(500000,1500000));
 254                                 }
 255
 256                                 # Save to local cache
 257                                 if ( $wgLocalMessageCache !== false ) {
 258                                         $serialized = serialize( $this->mCache );
 259                                         $hash = md5( $serialized );
 260                                         $this->mMemc->set( "{$this->mMemcKey}-hash", $hash, $this->mExpiry );
 261                                         if ($wgLocalMessageCacheSerialized) {
 262                                                 $this->saveToLocal( $serialized,$hash );
 263                                         } else {
 264                                                 $this->saveToScript( $this->mCache, $hash );
 265                                         }
 266                                 }
 267
 268                                 wfProfileOut( $fname.'-save' );
 269                                 if ( $i == 20 ) {
 270                                         $this->mMemc->set( $this->mMemcKey.'-status', 'error', 60*5 );
 271                                         wfDebug( "MemCached set error in MessageCache: restart memcached server!\n" );
 272                                 } else {
 273                                         $this->mMemc->delete( $this->mMemcKey.'-status' );
 274                                 }
 275                         }
 276                         $this->unlock();
 277                 }
 278
 279                 if ( !is_array( $this->mCache ) ) {
 280                         wfDebug( "MessageCache::load(): unable to load cache, disabled\n" );
 281                         $this->mDisable = true;
 282                         $this->mCache = false;
 283                 }
 284                 wfProfileOut( $fname );
 285                 $this->mDeferred = false;
 286                 return $success;
 287         }
 288
 289         /**
 290          * Loads all or main part of cacheable messages from the database
 291          */
 292         function loadFromDB() {
 293                 global $wgMaxMsgCacheEntrySize;
 294
 295                 wfProfileIn( __METHOD__ );
 296                 $dbr = wfGetDB( DB_SLAVE );
 297                 $this->mCache = array();
 298
 299                 # Load titles for all oversized pages in the MediaWiki namespace
 300                 $res = $dbr->select( 'page', 'page_title',
 301                         array(
 302                                 'page_len > ' . intval( $wgMaxMsgCacheEntrySize ),
 303                                 'page_is_redirect' => 0,
 304                                 'page_namespace' => NS_MEDIAWIKI,
 305                         ),
 306                         __METHOD__ );
 307                 while ( $row = $dbr->fetchObject( $res ) ) {
 308                         $this->mCache[$row->page_title] = '!TOO BIG';
 309                 }
 310                 $dbr->freeResult( $res );
 311
 312                 # Load text for the remaining pages
 313                 $res = $dbr->select( array( 'page', 'revision', 'text' ),
 314                         array( 'page_title', 'old_text', 'old_flags' ),
 315                         array(
 316                                 'page_is_redirect' => 0,
 317                                 'page_namespace' => NS_MEDIAWIKI,
 318                                 'page_latest=rev_id',
 319                                 'rev_text_id=old_id',
 320                                 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize ) ),
 321                         __METHOD__ );
 322
 323                 for ( $row = $dbr->fetchObject( $res ); $row; $row = $dbr->fetchObject( $res ) ) {
 324                         $this->mCache[$row->page_title] = ' ' . Revision::getRevisionText( $row );
 325                 }
 326                 $this->mCache['VERSION'] = MSG_CACHE_VERSION;
 327                 $dbr->freeResult( $res );
 328                 wfProfileOut( __METHOD__ );
 329         }
 330
 331         function replace( $title, $text ) {
 332                 global $wgLocalMessageCache, $wgLocalMessageCacheSerialized, $parserMemc;
 333                 global $wgMaxMsgCacheEntrySize;
 334
 335                 wfProfileIn( __METHOD__ );
 336                 $this->lock();
 337                 $this->load();
 338                 if ( is_array( $this->mCache ) ) {
 339                         if ( $text === false ) {
 340                                 # Article was deleted
 341                                 unset( $this->mCache[$title] );
 342                                 $this->mMemc->delete( "$this->mMemcKey:{$title}" );
 343                         } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 344                                 $this->mCache[$title] = '!TOO BIG';
 345                                 $this->mMemc->set( "$this->mMemcKey:{$title}", ' '.$text, $this->mExpiry );
 346                         } else {
 347                                 $this->mCache[$title] = ' ' . $text;
 348                                 $this->mMemc->delete( "$this->mMemcKey:{$title}" );
 349                         }
 350                         $this->mMemc->set( $this->mMemcKey, $this->mCache, $this->mExpiry );
 351
 352                         # Save to local cache
 353                         if ( $wgLocalMessageCache !== false ) {
 354                                 $serialized = serialize( $this->mCache );
 355                                 $hash = md5( $serialized );
 356                                 $this->mMemc->set( "{$this->mMemcKey}-hash", $hash, $this->mExpiry );
 357                                 if ($wgLocalMessageCacheSerialized) {
 358                                         $this->saveToLocal( $serialized,$hash );
 359                                 } else {
 360                                         $this->saveToScript( $this->mCache, $hash );
 361                                 }
 362                         }
 363                 }
 364                 $this->unlock();
 365                 $parserMemc->delete(wfMemcKey('sidebar'));
 366                 wfRunHooks( 'wfMessageCacheReplace', array( $title, $text ) );
 367                 wfProfileOut( __METHOD__ );
 368         }
 369
 370         /**
 371          * Returns success
 372          * Represents a write lock on the messages key
 373          */
 374         function lock() {
 375                 if ( !$this->mUseCache ) {
 376                         return true;
 377                 }
 378
 379                 $lockKey = $this->mMemcKey . 'lock';
 380                 for ($i=0; $i < MSG_WAIT_TIMEOUT && !$this->mMemc->add( $lockKey, 1, MSG_LOCK_TIMEOUT ); $i++ ) {
 381                         sleep(1);
 382                 }
 383
 384                 return $i >= MSG_WAIT_TIMEOUT;
 385         }
 386
 387         function unlock() {
 388                 if ( !$this->mUseCache ) {
 389                         return;
 390                 }
 391
 392                 $lockKey = $this->mMemcKey . 'lock';
 393                 $this->mMemc->delete( $lockKey );
 394         }
 395
 396         /**
 397          * Get a message from either the content language or the user language.
 398          *
 399          * @param string $key The message cache key
 400          * @param bool $useDB Get the message from the DB, false to use only the localisation
 401          * @param string $langcode Code of the language to get the message for, if
 402          *                         it is a valid code create a language for that
 403          *                         language, if it is a string but not a valid code
 404          *                         then make a basic language object, if it is a
 405          *                         false boolean then use the current users
 406          *                         language (as a fallback for the old parameter
 407          *                         functionality), or if it is a true boolean then
 408          *                         use the wikis content language (also as a
 409          *                         fallback).
 410          * @param bool $isFullKey Specifies whether $key is a two part key "lang/msg".
 411          */
 412         function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
 413                 global $wgContLanguageCode, $wgContLang, $wgLang;
 414
 415                 # Identify which language to get or create a language object for.
 416                 if( $langcode === $wgContLang->getCode() || $langcode === true ) {
 417                         # $langcode is the language code of the wikis content language object.
 418                         # or it is a boolean and value is true
 419                         $lang =& $wgContLang;
 420                 } elseif( $langcode === $wgLang->getCode() || $langcode === false ) {
 421                         # $langcode is the language code of user language object.
 422                         # or it was a boolean and value is false
 423                         $lang =& $wgLang;
 424                 } else {
 425                         $validCodes = array_keys( Language::getLanguageNames() );
 426                         if( in_array( $langcode, $validCodes ) ) {
 427                                 # $langcode corresponds to a valid language.
 428                                 $lang = Language::factory( $langcode );
 429                         } else {
 430                                 # $langcode is a string, but not a valid language code; use content language.
 431                                 $lang =& $wgContLang;
 432                                 wfDebug( 'Invalid language code passed to MessageCache::get, falling back to content language.' );
 433                         }
 434                 }
 435
 436                 $langcode = $lang->getCode();
 437
 438                 # If uninitialised, someone is trying to call this halfway through Setup.php
 439                 if( !$this->mInitialised ) {
 440                         return '&lt;' . htmlspecialchars($key) . '&gt;';
 441                 }
 442                 # If cache initialization was deferred, start it now.
 443                 if( $this->mDeferred && !$this->mDisable && $useDB ) {
 444                         $this->load();
 445                 }
 446
 447                 $message = false;
 448
 449                 # Normalise title-case input
 450                 $lckey = $wgContLang->lcfirst( $key );
 451                 $lckey = str_replace( ' ', '_', $lckey );
 452
 453                 # Try the MediaWiki namespace
 454                 if( !$this->mDisable && $useDB ) {
 455                         $title = $wgContLang->ucfirst( $lckey );
 456                         if(!$isFullKey && ($langcode != $wgContLanguageCode) ) {
 457                                 $title .= '/' . $langcode;
 458                         }
 459                         $message = $this->getMsgFromNamespace( $title );
 460                 }
 461                 # Try the extension array
 462                 if( $message === false && isset( $this->mExtensionMessages[$langcode][$lckey] ) ) {
 463                         $message = $this->mExtensionMessages[$langcode][$lckey];
 464                 }
 465                 if ( $message === false && isset( $this->mExtensionMessages['en'][$lckey] ) ) {
 466                         $message = $this->mExtensionMessages['en'][$lckey];
 467                 }
 468
 469                 # Try the array in the language object
 470                 if( $message === false ) {
 471                         #wfDebug( "Trying language object for message $key\n" );
 472                         wfSuppressWarnings();
 473                         $message = $lang->getMessage( $lckey );
 474                         wfRestoreWarnings();
 475                         if ( is_null( $message ) ) {
 476                                 $message = false;
 477                         }
 478                 }
 479
 480                 # Try the array of another language
 481                 $pos = strrpos( $lckey, '/' );
 482                 if( $message === false && $pos !== false) {
 483                         $mkey = substr( $lckey, 0, $pos );
 484                         $code = substr( $lckey, $pos+1 );
 485                         if ( $code ) {
 486                                 $validCodes = array_keys( Language::getLanguageNames() );
 487                                 if ( in_array( $code, $validCodes ) ) {
 488                                         $message = Language::getMessageFor( $mkey, $code );
 489                                         if ( is_null( $message ) ) {
 490                                                 $message = false;
 491                                         }
 492                                 } else {
 493                                         wfDebug( __METHOD__ . ": Invalid code $code for $mkey/$code, not trying messages array\n" );
 494                                 }
 495                         }
 496                 }
 497
 498                 # Is this a custom message? Try the default language in the db...
 499                 if( ($message === false || $message === '-' ) &&
 500                         !$this->mDisable && $useDB &&
 501                         !$isFullKey && ($langcode != $wgContLanguageCode) ) {
 502                         $message = $this->getMsgFromNamespace( $wgContLang->ucfirst( $lckey ) );
 503                 }
 504
 505                 # Final fallback
 506                 if( $message === false ) {
 507                         return '&lt;' . htmlspecialchars($key) . '&gt;';
 508                 }
 509                 return $message;
 510         }
 511
 512         /**
 513          * Get a message from the MediaWiki namespace, with caching. The key must
 514          * first be converted to two-part lang/msg form if necessary.
 515          *
 516          * @param string $title Message cache key with initial uppercase letter
 517          */
 518         function getMsgFromNamespace( $title ) {
 519                 $message = false;
 520                 $type = false;
 521
 522                 # Try the cache
 523                 if( $this->mUseCache && isset( $this->mCache[$title] ) ) {
 524                         $entry = $this->mCache[$title];
 525                         $type = substr( $entry, 0, 1 );
 526                         if ( $type == ' ' ) {
 527                                 return substr( $entry, 1 );
 528                         }
 529                 }
 530
 531                 # Call message hooks, in case they are defined
 532                 wfRunHooks('MessagesPreLoad', array( $title, &$message ) );
 533                 if ( $message !== false ) {
 534                         return $message;
 535                 }
 536
 537                 # If there is no cache entry and no placeholder, it doesn't exist
 538                 if ( $type != '!' && $message === false ) {
 539                         return false;
 540                 }
 541
 542                 $memcKey = $this->mMemcKey . ':' . $title;
 543
 544                 # Try the individual message cache
 545                 if ( $this->mUseCache ) {
 546                         $entry = $this->mMemc->get( $memcKey );
 547                         if ( $entry ) {
 548                                 $type = substr( $entry, 0, 1 );
 549
 550                                 if ( $type == ' ' ) {
 551                                         $message = substr( $entry, 1 );
 552                                         $this->mCache[$title] = $entry;
 553                                         return $message;
 554                                 } elseif ( $entry == '!NONEXISTENT' ) {
 555                                         return false;
 556                                 } else {
 557                                         # Corrupt/obsolete entry, delete it
 558                                         $this->mMemc->delete( $memcKey );
 559                                 }
 560
 561                         }
 562                 }
 563
 564                 # Try loading it from the DB
 565                 $revision = Revision::newFromTitle( Title::makeTitle( NS_MEDIAWIKI, $title ) );
 566                 if( $revision ) {
 567                         $message = $revision->getText();
 568                         if ($this->mUseCache) {
 569                                 $this->mCache[$title] = ' ' . $message;
 570                                 $this->mMemc->set( $memcKey, $message, $this->mExpiry );
 571                         }
 572                 } else {
 573                         # Negative caching
 574                         # Use some special text instead of false, because false gets converted to '' somewhere
 575                         $this->mMemc->set( $memcKey, '!NONEXISTENT', $this->mExpiry );
 576                         $this->mCache[$title] = false;
 577                 }
 578
 579                 return $message;
 580         }
 581
 582         function transform( $message, $interface = false ) {
 583                 global $wgParser;
 584                 if ( !$this->mParser && isset( $wgParser ) ) {
 585                         # Do some initialisation so that we don't have to do it twice
 586                         $wgParser->firstCallInit();
 587                         # Clone it and store it
 588                         $this->mParser = clone $wgParser;
 589                 }
 590                 if ( $this->mParser ) {
 591                         if( strpos( $message, '{{' ) !== false ) {
 592                                 $popts = $this->getParserOptions();
 593                                 $popts->setInterfaceMessage( $interface );
 594                                 $message = $this->mParser->transformMsg( $message, $popts );
 595                         }
 596                 }
 597                 return $message;
 598         }
 599
 600         function disable() { $this->mDisable = true; }
 601         function enable() { $this->mDisable = false; }
 602
 603         /** @deprecated */
 604         function disableTransform(){
 605                 wfDeprecated( __METHOD__ );
 606         }
 607         function enableTransform() {
 608                 wfDeprecated( __METHOD__ );
 609         }
 610         function setTransform( $x ) {
 611                 wfDeprecated( __METHOD__ );
 612         }
 613         function getTransform() {
 614                 wfDeprecated( __METHOD__ );
 615                 return false;
 616         }
 617
 618         /**
 619          * Add a message to the cache
 620          *
 621          * @param mixed $key
 622          * @param mixed $value
 623          * @param string $lang The messages language, English by default
 624          */
 625         function addMessage( $key, $value, $lang = 'en' ) {
 626                 $this->mExtensionMessages[$lang][$key] = $value;
 627         }
 628
 629         /**
 630          * Add an associative array of message to the cache
 631          *
 632          * @param array $messages An associative array of key => values to be added
 633          * @param string $lang The messages language, English by default
 634          */
 635         function addMessages( $messages, $lang = 'en' ) {
 636                 wfProfileIn( __METHOD__ );
 637                 if ( !is_array( $messages ) ) {
 638                         throw new MWException( __METHOD__.': Invalid message array' );
 639                 }
 640                 if ( isset( $this->mExtensionMessages[$lang] ) ) {
 641                         $this->mExtensionMessages[$lang] = $messages + $this->mExtensionMessages[$lang];
 642                 } else {
 643                         $this->mExtensionMessages[$lang] = $messages;
 644                 }
 645                 wfProfileOut( __METHOD__ );
 646         }
 647
 648         /**
 649          * Add a 2-D array of messages by lang. Useful for extensions.
 650          *
 651          * @param array $messages The array to be added
 652          */
 653         function addMessagesByLang( $messages ) {
 654                 wfProfileIn( __METHOD__ );
 655                 foreach ( $messages as $key => $value ) {
 656                         $this->addMessages( $value, $key );
 657                 }
 658                 wfProfileOut( __METHOD__ );
 659         }
 660
 661         /**
 662          * Get the extension messages for a specific language. Only English, interface
 663          * and content language are guaranteed to be loaded.
 664          *
 665          * @param string $lang The messages language, English by default
 666          */
 667         function getExtensionMessagesFor( $lang = 'en' ) {
 668                 wfProfileIn( __METHOD__ );
 669                 $messages = array();
 670                 if ( isset( $this->mExtensionMessages[$lang] ) ) {
 671                         $messages = $this->mExtensionMessages[$lang];
 672                 }
 673                 if ( $lang != 'en' ) {
 674                         $messages = $messages + $this->mExtensionMessages['en'];
 675                 }
 676                 wfProfileOut( __METHOD__ );
 677                 return $messages;
 678         }
 679
 680         /**
 681          * Clear all stored messages. Mainly used after a mass rebuild.
 682          */
 683         function clear() {
 684                 global $wgLocalMessageCache;
 685                 if( $this->mUseCache ) {
 686                         # Global cache
 687                         $this->mMemc->delete( $this->mMemcKey );
 688                         # Invalidate all local caches
 689                         $this->mMemc->delete( "{$this->mMemcKey}-hash" );
 690                 }
 691         }
 692
 693         function loadAllMessages() {
 694                 global $wgExtensionMessagesFiles;
 695                 if ( $this->mAllMessagesLoaded ) {
 696                         return;
 697                 }
 698                 $this->mAllMessagesLoaded = true;
 699
 700                 # Some extensions will load their messages when you load their class file
 701                 wfLoadAllExtensions();
 702                 # Others will respond to this hook
 703                 wfRunHooks( 'LoadAllMessages' );
 704                 # Some register their messages in $wgExtensionMessagesFiles
 705                 foreach ( $wgExtensionMessagesFiles as $name => $file ) {
 706                         wfLoadExtensionMessages( $name );
 707                 }
 708                 # Still others will respond to neither, they are EVIL. We sometimes need to know!
 709         }
 710
 711         /**
 712          * Load messages from a given file
 713          *
 714          * @param string $filename Filename of file to load.
 715          * @param string $langcode Language to load messages for, or false for
 716      *                         default behvaiour (en, content language and user
 717      *                         language).
 718          */
 719         function loadMessagesFile( $filename, $langcode = false ) {
 720                 global $wgLang, $wgContLang;
 721                 $messages = $magicWords = false;
 722                 require( $filename );
 723
 724                 $validCodes = Language::getLanguageNames();
 725                 if( is_string( $langcode ) && array_key_exists( $langcode, $validCodes ) ) {
 726                         # Load messages for given language code.
 727                         $this->processMessagesArray( $messages, $langcode );
 728                 } elseif( is_string( $langcode ) && !array_key_exists( $langcode, $validCodes ) ) {
 729                         wfDebug( "Invalid language '$langcode' code passed to MessageCache::loadMessagesFile()" );
 730                 } else {
 731                         # Load only languages that are usually used, and merge all
 732                         # fallbacks, except English.
 733                         $langs = array_unique( array( 'en', $wgContLang->getCode(), $wgLang->getCode() ) );
 734                         foreach( $langs as $code ) {
 735                                 $this->processMessagesArray( $messages, $code );
 736                         }
 737                 }
 738
 739                 if ( $magicWords !== false ) {
 740                         global $wgContLang;
 741                         $wgContLang->addMagicWordsByLang( $magicWords );
 742                 }
 743         }
 744
 745         /**
 746          * Process an array of messages, loading it into the message cache.
 747          *
 748          * @param array $messages Messages array.
 749          * @param string $langcode Language code to process.
 750          */
 751         function processMessagesArray( $messages, $langcode ) {
 752                 $fallbackCode = $langcode;
 753                 $mergedMessages = array();
 754                 do {
 755                         if ( isset($messages[$fallbackCode]) ) {
 756                                 $mergedMessages += $messages[$fallbackCode];
 757                         }
 758                         $fallbackCode = Language::getFallbackfor( $fallbackCode );
 759                 } while( $fallbackCode && $fallbackCode !== 'en' );
 760
 761                 if ( !empty($mergedMessages) )
 762                         $this->addMessages( $mergedMessages, $langcode );
 763         }
 764
 765 }