includes/filerepo/backend/FileBackendStore.php

   1 <?php
   2 /**
   3  * @file
   4  * @ingroup FileBackend
   5  * @author Aaron Schulz
   6  */
   7
   8 /**
   9  * @brief Base class for all backends using particular storage medium.
  10  *
  11  * This class defines the methods as abstract that subclasses must implement.
  12  * Outside callers should *not* use functions with "Internal" in the name.
  13  *
  14  * The FileBackend operations are implemented using basic functions
  15  * such as storeInternal(), copyInternal(), deleteInternal() and the like.
  16  * This class is also responsible for path resolution and sanitization.
  17  *
  18  * @ingroup FileBackend
  19  * @since 1.19
  20  */
  21 abstract class FileBackendStore extends FileBackend {
  22         /** @var BagOStuff */
  23         protected $memCache;
  24
  25         /** @var Array Map of paths to small (RAM/disk) cache items */
  26         protected $cache = array(); // (storage path => key => value)
  27         protected $maxCacheSize = 300; // integer; max paths with entries
  28         /** @var Array Map of paths to large (RAM/disk) cache items */
  29         protected $expensiveCache = array(); // (storage path => key => value)
  30         protected $maxExpensiveCacheSize = 5; // integer; max paths with entries
  31
  32         /** @var Array Map of container names to sharding settings */
  33         protected $shardViaHashLevels = array(); // (container name => config array)
  34
  35         protected $maxFileSize = 4294967296; // integer bytes (4GiB)
  36
  37         /**
  38          * @see FileBackend::__construct()
  39          *
  40          * @param $config Array
  41          */
  42         public function __construct( array $config ) {
  43                 parent::__construct( $config );
  44                 $this->memCache = new EmptyBagOStuff(); // disabled by default
  45         }
  46
  47         /**
  48          * Get the maximum allowable file size given backend
  49          * medium restrictions and basic performance constraints.
  50          * Do not call this function from places outside FileBackend and FileOp.
  51          *
  52          * @return integer Bytes
  53          */
  54         final public function maxFileSizeInternal() {
  55                 return $this->maxFileSize;
  56         }
  57
  58         /**
  59          * Check if a file can be created at a given storage path.
  60          * FS backends should check if the parent directory exists and the file is writable.
  61          * Backends using key/value stores should check if the container exists.
  62          *
  63          * @param $storagePath string
  64          * @return bool
  65          */
  66         abstract public function isPathUsableInternal( $storagePath );
  67
  68         /**
  69          * Create a file in the backend with the given contents.
  70          * Do not call this function from places outside FileBackend and FileOp.
  71          *
  72          * $params include:
  73          *     content       : the raw file contents
  74          *     dst           : destination storage path
  75          *     overwrite     : overwrite any file that exists at the destination
  76          *
  77          * @param $params Array
  78          * @return Status
  79          */
  80         final public function createInternal( array $params ) {
  81                 wfProfileIn( __METHOD__ );
  82                 wfProfileIn( __METHOD__ . '-' . $this->name );
  83                 if ( strlen( $params['content'] ) > $this->maxFileSizeInternal() ) {
  84                         $status = Status::newFatal( 'backend-fail-maxsize',
  85                                 $params['dst'], $this->maxFileSizeInternal() );
  86                 } else {
  87                         $status = $this->doCreateInternal( $params );
  88                         $this->clearCache( array( $params['dst'] ) );
  89                 }
  90                 wfProfileOut( __METHOD__ . '-' . $this->name );
  91                 wfProfileOut( __METHOD__ );
  92                 return $status;
  93         }
  94
  95         /**
  96          * @see FileBackendStore::createInternal()
  97          */
  98         abstract protected function doCreateInternal( array $params );
  99
 100         /**
 101          * Store a file into the backend from a file on disk.
 102          * Do not call this function from places outside FileBackend and FileOp.
 103          *
 104          * $params include:
 105          *     src           : source path on disk
 106          *     dst           : destination storage path
 107          *     overwrite     : overwrite any file that exists at the destination
 108          *
 109          * @param $params Array
 110          * @return Status
 111          */
 112         final public function storeInternal( array $params ) {
 113                 wfProfileIn( __METHOD__ );
 114                 wfProfileIn( __METHOD__ . '-' . $this->name );
 115                 if ( filesize( $params['src'] ) > $this->maxFileSizeInternal() ) {
 116                         $status = Status::newFatal( 'backend-fail-store', $params['dst'] );
 117                 } else {
 118                         $status = $this->doStoreInternal( $params );
 119                         $this->clearCache( array( $params['dst'] ) );
 120                 }
 121                 wfProfileOut( __METHOD__ . '-' . $this->name );
 122                 wfProfileOut( __METHOD__ );
 123                 return $status;
 124         }
 125
 126         /**
 127          * @see FileBackendStore::storeInternal()
 128          */
 129         abstract protected function doStoreInternal( array $params );
 130
 131         /**
 132          * Copy a file from one storage path to another in the backend.
 133          * Do not call this function from places outside FileBackend and FileOp.
 134          *
 135          * $params include:
 136          *     src           : source storage path
 137          *     dst           : destination storage path
 138          *     overwrite     : overwrite any file that exists at the destination
 139          *
 140          * @param $params Array
 141          * @return Status
 142          */
 143         final public function copyInternal( array $params ) {
 144                 wfProfileIn( __METHOD__ );
 145                 wfProfileIn( __METHOD__ . '-' . $this->name );
 146                 $status = $this->doCopyInternal( $params );
 147                 $this->clearCache( array( $params['dst'] ) );
 148                 wfProfileOut( __METHOD__ . '-' . $this->name );
 149                 wfProfileOut( __METHOD__ );
 150                 return $status;
 151         }
 152
 153         /**
 154          * @see FileBackendStore::copyInternal()
 155          */
 156         abstract protected function doCopyInternal( array $params );
 157
 158         /**
 159          * Delete a file at the storage path.
 160          * Do not call this function from places outside FileBackend and FileOp.
 161          *
 162          * $params include:
 163          *     src                 : source storage path
 164          *     ignoreMissingSource : do nothing if the source file does not exist
 165          *
 166          * @param $params Array
 167          * @return Status
 168          */
 169         final public function deleteInternal( array $params ) {
 170                 wfProfileIn( __METHOD__ );
 171                 wfProfileIn( __METHOD__ . '-' . $this->name );
 172                 $status = $this->doDeleteInternal( $params );
 173                 $this->clearCache( array( $params['src'] ) );
 174                 wfProfileOut( __METHOD__ . '-' . $this->name );
 175                 wfProfileOut( __METHOD__ );
 176                 return $status;
 177         }
 178
 179         /**
 180          * @see FileBackendStore::deleteInternal()
 181          */
 182         abstract protected function doDeleteInternal( array $params );
 183
 184         /**
 185          * Move a file from one storage path to another in the backend.
 186          * Do not call this function from places outside FileBackend and FileOp.
 187          *
 188          * $params include:
 189          *     src           : source storage path
 190          *     dst           : destination storage path
 191          *     overwrite     : overwrite any file that exists at the destination
 192          *
 193          * @param $params Array
 194          * @return Status
 195          */
 196         final public function moveInternal( array $params ) {
 197                 wfProfileIn( __METHOD__ );
 198                 wfProfileIn( __METHOD__ . '-' . $this->name );
 199                 $status = $this->doMoveInternal( $params );
 200                 $this->clearCache( array( $params['src'], $params['dst'] ) );
 201                 wfProfileOut( __METHOD__ . '-' . $this->name );
 202                 wfProfileOut( __METHOD__ );
 203                 return $status;
 204         }
 205
 206         /**
 207          * @see FileBackendStore::moveInternal()
 208          * @return Status
 209          */
 210         protected function doMoveInternal( array $params ) {
 211                 // Copy source to dest
 212                 $status = $this->copyInternal( $params );
 213                 if ( $status->isOK() ) {
 214                         // Delete source (only fails due to races or medium going down)
 215                         $status->merge( $this->deleteInternal( array( 'src' => $params['src'] ) ) );
 216                         $status->setResult( true, $status->value ); // ignore delete() errors
 217                 }
 218                 return $status;
 219         }
 220
 221         /**
 222          * @see FileBackend::concatenate()
 223          * @return Status
 224          */
 225         final public function concatenate( array $params ) {
 226                 wfProfileIn( __METHOD__ );
 227                 wfProfileIn( __METHOD__ . '-' . $this->name );
 228                 $status = Status::newGood();
 229
 230                 // Try to lock the source files for the scope of this function
 231                 $scopeLockS = $this->getScopedFileLocks( $params['srcs'], LockManager::LOCK_UW, $status );
 232                 if ( $status->isOK() ) {
 233                         // Actually do the concatenation
 234                         $status->merge( $this->doConcatenate( $params ) );
 235                 }
 236
 237                 wfProfileOut( __METHOD__ . '-' . $this->name );
 238                 wfProfileOut( __METHOD__ );
 239                 return $status;
 240         }
 241
 242         /**
 243          * @see FileBackendStore::concatenate()
 244          * @return Status
 245          */
 246         protected function doConcatenate( array $params ) {
 247                 $status = Status::newGood();
 248                 $tmpPath = $params['dst']; // convenience
 249
 250                 // Check that the specified temp file is valid...
 251                 wfSuppressWarnings();
 252                 $ok = ( is_file( $tmpPath ) && !filesize( $tmpPath ) );
 253                 wfRestoreWarnings();
 254                 if ( !$ok ) { // not present or not empty
 255                         $status->fatal( 'backend-fail-opentemp', $tmpPath );
 256                         return $status;
 257                 }
 258
 259                 // Build up the temp file using the source chunks (in order)...
 260                 $tmpHandle = fopen( $tmpPath, 'ab' );
 261                 if ( $tmpHandle === false ) {
 262                         $status->fatal( 'backend-fail-opentemp', $tmpPath );
 263                         return $status;
 264                 }
 265                 foreach ( $params['srcs'] as $virtualSource ) {
 266                         // Get a local FS version of the chunk
 267                         $tmpFile = $this->getLocalReference( array( 'src' => $virtualSource ) );
 268                         if ( !$tmpFile ) {
 269                                 $status->fatal( 'backend-fail-read', $virtualSource );
 270                                 return $status;
 271                         }
 272                         // Get a handle to the local FS version
 273                         $sourceHandle = fopen( $tmpFile->getPath(), 'r' );
 274                         if ( $sourceHandle === false ) {
 275                                 fclose( $tmpHandle );
 276                                 $status->fatal( 'backend-fail-read', $virtualSource );
 277                                 return $status;
 278                         }
 279                         // Append chunk to file (pass chunk size to avoid magic quotes)
 280                         if ( !stream_copy_to_stream( $sourceHandle, $tmpHandle ) ) {
 281                                 fclose( $sourceHandle );
 282                                 fclose( $tmpHandle );
 283                                 $status->fatal( 'backend-fail-writetemp', $tmpPath );
 284                                 return $status;
 285                         }
 286                         fclose( $sourceHandle );
 287                 }
 288                 if ( !fclose( $tmpHandle ) ) {
 289                         $status->fatal( 'backend-fail-closetemp', $tmpPath );
 290                         return $status;
 291                 }
 292
 293                 clearstatcache(); // temp file changed
 294
 295                 return $status;
 296         }
 297
 298         /**
 299          * @see FileBackend::doPrepare()
 300          * @return Status
 301          */
 302         final protected function doPrepare( array $params ) {
 303                 wfProfileIn( __METHOD__ );
 304                 wfProfileIn( __METHOD__ . '-' . $this->name );
 305
 306                 $status = Status::newGood();
 307                 list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
 308                 if ( $dir === null ) {
 309                         $status->fatal( 'backend-fail-invalidpath', $params['dir'] );
 310                         wfProfileOut( __METHOD__ . '-' . $this->name );
 311                         wfProfileOut( __METHOD__ );
 312                         return $status; // invalid storage path
 313                 }
 314
 315                 if ( $shard !== null ) { // confined to a single container/shard
 316                         $status->merge( $this->doPrepareInternal( $fullCont, $dir, $params ) );
 317                 } else { // directory is on several shards
 318                         wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
 319                         list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
 320                         foreach ( $this->getContainerSuffixes( $shortCont ) as $suffix ) {
 321                                 $status->merge( $this->doPrepareInternal( "{$fullCont}{$suffix}", $dir, $params ) );
 322                         }
 323                 }
 324
 325                 wfProfileOut( __METHOD__ . '-' . $this->name );
 326                 wfProfileOut( __METHOD__ );
 327                 return $status;
 328         }
 329
 330         /**
 331          * @see FileBackendStore::doPrepare()
 332          * @return Status
 333          */
 334         protected function doPrepareInternal( $container, $dir, array $params ) {
 335                 return Status::newGood();
 336         }
 337
 338         /**
 339          * @see FileBackend::doSecure()
 340          * @return Status
 341          */
 342         final protected function doSecure( array $params ) {
 343                 wfProfileIn( __METHOD__ );
 344                 wfProfileIn( __METHOD__ . '-' . $this->name );
 345                 $status = Status::newGood();
 346
 347                 list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
 348                 if ( $dir === null ) {
 349                         $status->fatal( 'backend-fail-invalidpath', $params['dir'] );
 350                         wfProfileOut( __METHOD__ . '-' . $this->name );
 351                         wfProfileOut( __METHOD__ );
 352                         return $status; // invalid storage path
 353                 }
 354
 355                 if ( $shard !== null ) { // confined to a single container/shard
 356                         $status->merge( $this->doSecureInternal( $fullCont, $dir, $params ) );
 357                 } else { // directory is on several shards
 358                         wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
 359                         list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
 360                         foreach ( $this->getContainerSuffixes( $shortCont ) as $suffix ) {
 361                                 $status->merge( $this->doSecureInternal( "{$fullCont}{$suffix}", $dir, $params ) );
 362                         }
 363                 }
 364
 365                 wfProfileOut( __METHOD__ . '-' . $this->name );
 366                 wfProfileOut( __METHOD__ );
 367                 return $status;
 368         }
 369
 370         /**
 371          * @see FileBackendStore::doSecure()
 372          * @return Status
 373          */
 374         protected function doSecureInternal( $container, $dir, array $params ) {
 375                 return Status::newGood();
 376         }
 377
 378         /**
 379          * @see FileBackend::doClean()
 380          * @return Status
 381          */
 382         final protected function doClean( array $params ) {
 383                 wfProfileIn( __METHOD__ );
 384                 wfProfileIn( __METHOD__ . '-' . $this->name );
 385                 $status = Status::newGood();
 386
 387                 // Recursive: first delete all empty subdirs recursively
 388                 if ( !empty( $params['recursive'] ) && !$this->directoriesAreVirtual() ) {
 389                         $subDirsRel = $this->getTopDirectoryList( array( 'dir' => $params['dir'] ) );
 390                         if ( $subDirsRel !== null ) { // no errors
 391                                 foreach ( $subDirsRel as $subDirRel ) {
 392                                         $subDir = $params['dir'] . "/{$subDirRel}"; // full path
 393                                         $status->merge( $this->doClean( array( 'dir' => $subDir ) + $params ) );
 394                                 }
 395                         }
 396                 }
 397
 398                 list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
 399                 if ( $dir === null ) {
 400                         $status->fatal( 'backend-fail-invalidpath', $params['dir'] );
 401                         wfProfileOut( __METHOD__ . '-' . $this->name );
 402                         wfProfileOut( __METHOD__ );
 403                         return $status; // invalid storage path
 404                 }
 405
 406                 // Attempt to lock this directory...
 407                 $filesLockEx = array( $params['dir'] );
 408                 $scopedLockE = $this->getScopedFileLocks( $filesLockEx, LockManager::LOCK_EX, $status );
 409                 if ( !$status->isOK() ) {
 410                         wfProfileOut( __METHOD__ . '-' . $this->name );
 411                         wfProfileOut( __METHOD__ );
 412                         return $status; // abort
 413                 }
 414
 415                 if ( $shard !== null ) { // confined to a single container/shard
 416                         $status->merge( $this->doCleanInternal( $fullCont, $dir, $params ) );
 417                         $this->deleteContainerCache( $fullCont ); // purge cache
 418                 } else { // directory is on several shards
 419                         wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
 420                         list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
 421                         foreach ( $this->getContainerSuffixes( $shortCont ) as $suffix ) {
 422                                 $status->merge( $this->doCleanInternal( "{$fullCont}{$suffix}", $dir, $params ) );
 423                                 $this->deleteContainerCache( "{$fullCont}{$suffix}" ); // purge cache
 424                         }
 425                 }
 426
 427                 wfProfileOut( __METHOD__ . '-' . $this->name );
 428                 wfProfileOut( __METHOD__ );
 429                 return $status;
 430         }
 431
 432         /**
 433          * @see FileBackendStore::doClean()
 434          * @return Status
 435          */
 436         protected function doCleanInternal( $container, $dir, array $params ) {
 437                 return Status::newGood();
 438         }
 439
 440         /**
 441          * @see FileBackend::fileExists()
 442          * @return bool|null
 443          */
 444         final public function fileExists( array $params ) {
 445                 wfProfileIn( __METHOD__ );
 446                 wfProfileIn( __METHOD__ . '-' . $this->name );
 447                 $stat = $this->getFileStat( $params );
 448                 wfProfileOut( __METHOD__ . '-' . $this->name );
 449                 wfProfileOut( __METHOD__ );
 450                 return ( $stat === null ) ? null : (bool)$stat; // null => failure
 451         }
 452
 453         /**
 454          * @see FileBackend::getFileTimestamp()
 455          * @return bool
 456          */
 457         final public function getFileTimestamp( array $params ) {
 458                 wfProfileIn( __METHOD__ );
 459                 wfProfileIn( __METHOD__ . '-' . $this->name );
 460                 $stat = $this->getFileStat( $params );
 461                 wfProfileOut( __METHOD__ . '-' . $this->name );
 462                 wfProfileOut( __METHOD__ );
 463                 return $stat ? $stat['mtime'] : false;
 464         }
 465
 466         /**
 467          * @see FileBackend::getFileSize()
 468          * @return bool
 469          */
 470         final public function getFileSize( array $params ) {
 471                 wfProfileIn( __METHOD__ );
 472                 wfProfileIn( __METHOD__ . '-' . $this->name );
 473                 $stat = $this->getFileStat( $params );
 474                 wfProfileOut( __METHOD__ . '-' . $this->name );
 475                 wfProfileOut( __METHOD__ );
 476                 return $stat ? $stat['size'] : false;
 477         }
 478
 479         /**
 480          * @see FileBackend::getFileStat()
 481          * @return bool
 482          */
 483         final public function getFileStat( array $params ) {
 484                 wfProfileIn( __METHOD__ );
 485                 wfProfileIn( __METHOD__ . '-' . $this->name );
 486                 $path = self::normalizeStoragePath( $params['src'] );
 487                 if ( $path === null ) {
 488                         wfProfileOut( __METHOD__ . '-' . $this->name );
 489                         wfProfileOut( __METHOD__ );
 490                         return false; // invalid storage path
 491                 }
 492                 $latest = !empty( $params['latest'] );
 493                 if ( isset( $this->cache[$path]['stat'] ) ) {
 494                         // If we want the latest data, check that this cached
 495                         // value was in fact fetched with the latest available data.
 496                         if ( !$latest || $this->cache[$path]['stat']['latest'] ) {
 497                                 $this->pingCache( $path ); // LRU
 498                                 wfProfileOut( __METHOD__ . '-' . $this->name );
 499                                 wfProfileOut( __METHOD__ );
 500                                 return $this->cache[$path]['stat'];
 501                         }
 502                 }
 503                 wfProfileIn( __METHOD__ . '-miss' );
 504                 wfProfileIn( __METHOD__ . '-miss-' . $this->name );
 505                 $stat = $this->doGetFileStat( $params );
 506                 wfProfileOut( __METHOD__ . '-miss-' . $this->name );
 507                 wfProfileOut( __METHOD__ . '-miss' );
 508                 if ( is_array( $stat ) ) { // don't cache negatives
 509                         $this->trimCache(); // limit memory
 510                         $this->cache[$path]['stat'] = $stat;
 511                         $this->cache[$path]['stat']['latest'] = $latest;
 512                 }
 513                 wfProfileOut( __METHOD__ . '-' . $this->name );
 514                 wfProfileOut( __METHOD__ );
 515                 return $stat;
 516         }
 517
 518         /**
 519          * @see FileBackendStore::getFileStat()
 520          */
 521         abstract protected function doGetFileStat( array $params );
 522
 523         /**
 524          * @see FileBackend::getFileContents()
 525          * @return bool|string
 526          */
 527         public function getFileContents( array $params ) {
 528                 wfProfileIn( __METHOD__ );
 529                 wfProfileIn( __METHOD__ . '-' . $this->name );
 530                 $tmpFile = $this->getLocalReference( $params );
 531                 if ( !$tmpFile ) {
 532                         wfProfileOut( __METHOD__ . '-' . $this->name );
 533                         wfProfileOut( __METHOD__ );
 534                         return false;
 535                 }
 536                 wfSuppressWarnings();
 537                 $data = file_get_contents( $tmpFile->getPath() );
 538                 wfRestoreWarnings();
 539                 wfProfileOut( __METHOD__ . '-' . $this->name );
 540                 wfProfileOut( __METHOD__ );
 541                 return $data;
 542         }
 543
 544         /**
 545          * @see FileBackend::getFileSha1Base36()
 546          * @return bool|string
 547          */
 548         final public function getFileSha1Base36( array $params ) {
 549                 wfProfileIn( __METHOD__ );
 550                 wfProfileIn( __METHOD__ . '-' . $this->name );
 551                 $path = $params['src'];
 552                 if ( isset( $this->cache[$path]['sha1'] ) ) {
 553                         $this->pingCache( $path ); // LRU
 554                         wfProfileOut( __METHOD__ . '-' . $this->name );
 555                         wfProfileOut( __METHOD__ );
 556                         return $this->cache[$path]['sha1'];
 557                 }
 558                 wfProfileIn( __METHOD__ . '-miss' );
 559                 wfProfileIn( __METHOD__ . '-miss-' . $this->name );
 560                 $hash = $this->doGetFileSha1Base36( $params );
 561                 wfProfileOut( __METHOD__ . '-miss-' . $this->name );
 562                 wfProfileOut( __METHOD__ . '-miss' );
 563                 if ( $hash ) { // don't cache negatives
 564                         $this->trimCache(); // limit memory
 565                         $this->cache[$path]['sha1'] = $hash;
 566                 }
 567                 wfProfileOut( __METHOD__ . '-' . $this->name );
 568                 wfProfileOut( __METHOD__ );
 569                 return $hash;
 570         }
 571
 572         /**
 573          * @see FileBackendStore::getFileSha1Base36()
 574          * @return bool
 575          */
 576         protected function doGetFileSha1Base36( array $params ) {
 577                 $fsFile = $this->getLocalReference( $params );
 578                 if ( !$fsFile ) {
 579                         return false;
 580                 } else {
 581                         return $fsFile->getSha1Base36();
 582                 }
 583         }
 584
 585         /**
 586          * @see FileBackend::getFileProps()
 587          * @return Array
 588          */
 589         final public function getFileProps( array $params ) {
 590                 wfProfileIn( __METHOD__ );
 591                 wfProfileIn( __METHOD__ . '-' . $this->name );
 592                 $fsFile = $this->getLocalReference( $params );
 593                 $props = $fsFile ? $fsFile->getProps() : FSFile::placeholderProps();
 594                 wfProfileOut( __METHOD__ . '-' . $this->name );
 595                 wfProfileOut( __METHOD__ );
 596                 return $props;
 597         }
 598
 599         /**
 600          * @see FileBackend::getLocalReference()
 601          * @return TempFSFile|null
 602          */
 603         public function getLocalReference( array $params ) {
 604                 wfProfileIn( __METHOD__ );
 605                 wfProfileIn( __METHOD__ . '-' . $this->name );
 606                 $path = $params['src'];
 607                 if ( isset( $this->expensiveCache[$path]['localRef'] ) ) {
 608                         $this->pingExpensiveCache( $path );
 609                         wfProfileOut( __METHOD__ . '-' . $this->name );
 610                         wfProfileOut( __METHOD__ );
 611                         return $this->expensiveCache[$path]['localRef'];
 612                 }
 613                 $tmpFile = $this->getLocalCopy( $params );
 614                 if ( $tmpFile ) { // don't cache negatives
 615                         $this->trimExpensiveCache(); // limit memory
 616                         $this->expensiveCache[$path]['localRef'] = $tmpFile;
 617                 }
 618                 wfProfileOut( __METHOD__ . '-' . $this->name );
 619                 wfProfileOut( __METHOD__ );
 620                 return $tmpFile;
 621         }
 622
 623         /**
 624          * @see FileBackend::streamFile()
 625          * @return Status
 626          */
 627         final public function streamFile( array $params ) {
 628                 wfProfileIn( __METHOD__ );
 629                 wfProfileIn( __METHOD__ . '-' . $this->name );
 630                 $status = Status::newGood();
 631
 632                 $info = $this->getFileStat( $params );
 633                 if ( !$info ) { // let StreamFile handle the 404
 634                         $status->fatal( 'backend-fail-notexists', $params['src'] );
 635                 }
 636
 637                 // Set output buffer and HTTP headers for stream
 638                 $extraHeaders = isset( $params['headers'] ) ? $params['headers'] : array();
 639                 $res = StreamFile::prepareForStream( $params['src'], $info, $extraHeaders );
 640                 if ( $res == StreamFile::NOT_MODIFIED ) {
 641                         // do nothing; client cache is up to date
 642                 } elseif ( $res == StreamFile::READY_STREAM ) {
 643                         wfProfileIn( __METHOD__ . '-send' );
 644                         wfProfileIn( __METHOD__ . '-send-' . $this->name );
 645                         $status = $this->doStreamFile( $params );
 646                         wfProfileOut( __METHOD__ . '-send-' . $this->name );
 647                         wfProfileOut( __METHOD__ . '-send' );
 648                 } else {
 649                         $status->fatal( 'backend-fail-stream', $params['src'] );
 650                 }
 651
 652                 wfProfileOut( __METHOD__ . '-' . $this->name );
 653                 wfProfileOut( __METHOD__ );
 654                 return $status;
 655         }
 656
 657         /**
 658          * @see FileBackendStore::streamFile()
 659          * @return Status
 660          */
 661         protected function doStreamFile( array $params ) {
 662                 $status = Status::newGood();
 663
 664                 $fsFile = $this->getLocalReference( $params );
 665                 if ( !$fsFile ) {
 666                         $status->fatal( 'backend-fail-stream', $params['src'] );
 667                 } elseif ( !readfile( $fsFile->getPath() ) ) {
 668                         $status->fatal( 'backend-fail-stream', $params['src'] );
 669                 }
 670
 671                 return $status;
 672         }
 673
 674         /**
 675          * @see FileBackend::directoryExists()
 676          * @return bool|null
 677          */
 678         final public function directoryExists( array $params ) {
 679                 list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
 680                 if ( $dir === null ) {
 681                         return false; // invalid storage path
 682                 }
 683                 if ( $shard !== null ) { // confined to a single container/shard
 684                         return $this->doDirectoryExists( $fullCont, $dir, $params );
 685                 } else { // directory is on several shards
 686                         wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
 687                         list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
 688                         $res = false; // response
 689                         foreach ( $this->getContainerSuffixes( $shortCont ) as $suffix ) {
 690                                 $exists = $this->doDirectoryExists( "{$fullCont}{$suffix}", $dir, $params );
 691                                 if ( $exists ) {
 692                                         $res = true;
 693                                         break; // found one!
 694                                 } elseif ( $exists === null ) { // error?
 695                                         $res = null; // if we don't find anything, it is indeterminate
 696                                 }
 697                         }
 698                         return $res;
 699                 }
 700         }
 701
 702         /**
 703          * @see FileBackendStore::directoryExists()
 704          *
 705          * @param $container string Resolved container name
 706          * @param $dir string Resolved path relative to container
 707          * @param $params Array
 708          * @return bool|null
 709          */
 710         abstract protected function doDirectoryExists( $container, $dir, array $params );
 711
 712         /**
 713          * @see FileBackend::getDirectoryList()
 714          * @return Array|null|Traversable
 715          */
 716         final public function getDirectoryList( array $params ) {
 717                 list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
 718                 if ( $dir === null ) { // invalid storage path
 719                         return null;
 720                 }
 721                 if ( $shard !== null ) {
 722                         // File listing is confined to a single container/shard
 723                         return $this->getDirectoryListInternal( $fullCont, $dir, $params );
 724                 } else {
 725                         wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
 726                         // File listing spans multiple containers/shards
 727                         list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
 728                         return new FileBackendStoreShardDirIterator( $this,
 729                                 $fullCont, $dir, $this->getContainerSuffixes( $shortCont ), $params );
 730                 }
 731         }
 732
 733         /**
 734          * Do not call this function from places outside FileBackend
 735          *
 736          * @see FileBackendStore::getDirectoryList()
 737          *
 738          * @param $container string Resolved container name
 739          * @param $dir string Resolved path relative to container
 740          * @param $params Array
 741          * @return Traversable|Array|null
 742          */
 743         abstract public function getDirectoryListInternal( $container, $dir, array $params );
 744
 745         /**
 746          * @see FileBackend::getFileList()
 747          * @return Array|null|Traversable
 748          */
 749         final public function getFileList( array $params ) {
 750                 list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
 751                 if ( $dir === null ) { // invalid storage path
 752                         return null;
 753                 }
 754                 if ( $shard !== null ) {
 755                         // File listing is confined to a single container/shard
 756                         return $this->getFileListInternal( $fullCont, $dir, $params );
 757                 } else {
 758                         wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
 759                         // File listing spans multiple containers/shards
 760                         list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
 761                         return new FileBackendStoreShardFileIterator( $this,
 762                                 $fullCont, $dir, $this->getContainerSuffixes( $shortCont ), $params );
 763                 }
 764         }
 765
 766         /**
 767          * Do not call this function from places outside FileBackend
 768          *
 769          * @see FileBackendStore::getFileList()
 770          *
 771          * @param $container string Resolved container name
 772          * @param $dir string Resolved path relative to container
 773          * @param $params Array
 774          * @return Traversable|Array|null
 775          */
 776         abstract public function getFileListInternal( $container, $dir, array $params );
 777
 778         /**
 779          * Get the list of supported operations and their corresponding FileOp classes.
 780          *
 781          * @return Array
 782          */
 783         protected function supportedOperations() {
 784                 return array(
 785                         'store'       => 'StoreFileOp',
 786                         'copy'        => 'CopyFileOp',
 787                         'move'        => 'MoveFileOp',
 788                         'delete'      => 'DeleteFileOp',
 789                         'create'      => 'CreateFileOp',
 790                         'null'        => 'NullFileOp'
 791                 );
 792         }
 793
 794         /**
 795          * Return a list of FileOp objects from a list of operations.
 796          * Do not call this function from places outside FileBackend.
 797          *
 798          * The result must have the same number of items as the input.
 799          * An exception is thrown if an unsupported operation is requested.
 800          *
 801          * @param $ops Array Same format as doOperations()
 802          * @return Array List of FileOp objects
 803          * @throws MWException
 804          */
 805         final public function getOperationsInternal( array $ops ) {
 806                 $supportedOps = $this->supportedOperations();
 807
 808                 $performOps = array(); // array of FileOp objects
 809                 // Build up ordered array of FileOps...
 810                 foreach ( $ops as $operation ) {
 811                         $opName = $operation['op'];
 812                         if ( isset( $supportedOps[$opName] ) ) {
 813                                 $class = $supportedOps[$opName];
 814                                 // Get params for this operation
 815                                 $params = $operation;
 816                                 // Append the FileOp class
 817                                 $performOps[] = new $class( $this, $params );
 818                         } else {
 819                                 throw new MWException( "Operation '$opName' is not supported." );
 820                         }
 821                 }
 822
 823                 return $performOps;
 824         }
 825
 826         /**
 827          * Get a list of storage paths to lock for a list of operations
 828          * Returns an array with 'sh' (shared) and 'ex' (exclusive) keys,
 829          * each corresponding to a list of storage paths to be locked.
 830          *
 831          * @param $performOps Array List of FileOp objects
 832          * @return Array ('sh' => list of paths, 'ex' => list of paths)
 833          */
 834         final public function getPathsToLockForOpsInternal( array $performOps ) {
 835                 // Build up a list of files to lock...
 836                 $paths = array( 'sh' => array(), 'ex' => array() );
 837                 foreach ( $performOps as $fileOp ) {
 838                         $paths['sh'] = array_merge( $paths['sh'], $fileOp->storagePathsRead() );
 839                         $paths['ex'] = array_merge( $paths['ex'], $fileOp->storagePathsChanged() );
 840                 }
 841                 // Optimization: if doing an EX lock anyway, don't also set an SH one
 842                 $paths['sh'] = array_diff( $paths['sh'], $paths['ex'] );
 843                 // Get a shared lock on the parent directory of each path changed
 844                 $paths['sh'] = array_merge( $paths['sh'], array_map( 'dirname', $paths['ex'] ) );
 845
 846                 return $paths;
 847         }
 848
 849         /**
 850          * @see FileBackend::doOperationsInternal()
 851          * @return Status
 852          */
 853         protected function doOperationsInternal( array $ops, array $opts ) {
 854                 wfProfileIn( __METHOD__ );
 855                 wfProfileIn( __METHOD__ . '-' . $this->name );
 856                 $status = Status::newGood();
 857
 858                 // Build up a list of FileOps...
 859                 $performOps = $this->getOperationsInternal( $ops );
 860
 861                 // Acquire any locks as needed...
 862                 if ( empty( $opts['nonLocking'] ) ) {
 863                         // Build up a list of files to lock...
 864                         $paths = $this->getPathsToLockForOpsInternal( $performOps );
 865                         // Try to lock those files for the scope of this function...
 866                         $scopeLockS = $this->getScopedFileLocks( $paths['sh'], LockManager::LOCK_UW, $status );
 867                         $scopeLockE = $this->getScopedFileLocks( $paths['ex'], LockManager::LOCK_EX, $status );
 868                         if ( !$status->isOK() ) {
 869                                 wfProfileOut( __METHOD__ . '-' . $this->name );
 870                                 wfProfileOut( __METHOD__ );
 871                                 return $status; // abort
 872                         }
 873                 }
 874
 875                 // Clear any file cache entries (after locks acquired)
 876                 $this->clearCache();
 877
 878                 // Load from the persistent container cache
 879                 $this->primeContainerCache( $performOps );
 880
 881                 // Actually attempt the operation batch...
 882                 $subStatus = FileOp::attemptBatch( $performOps, $opts, $this->fileJournal );
 883
 884                 // Merge errors into status fields
 885                 $status->merge( $subStatus );
 886                 $status->success = $subStatus->success; // not done in merge()
 887
 888                 wfProfileOut( __METHOD__ . '-' . $this->name );
 889                 wfProfileOut( __METHOD__ );
 890                 return $status;
 891         }
 892
 893         /**
 894          * @see FileBackend::clearCache()
 895          */
 896         final public function clearCache( array $paths = null ) {
 897                 if ( is_array( $paths ) ) {
 898                         $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
 899                         $paths = array_filter( $paths, 'strlen' ); // remove nulls
 900                 }
 901                 if ( $paths === null ) {
 902                         $this->cache = array();
 903                         $this->expensiveCache = array();
 904                 } else {
 905                         foreach ( $paths as $path ) {
 906                                 unset( $this->cache[$path] );
 907                                 unset( $this->expensiveCache[$path] );
 908                         }
 909                 }
 910                 $this->doClearCache( $paths );
 911         }
 912
 913         /**
 914          * Clears any additional stat caches for storage paths
 915          *
 916          * @see FileBackend::clearCache()
 917          *
 918          * @param $paths Array Storage paths (optional)
 919          * @return void
 920          */
 921         protected function doClearCache( array $paths = null ) {}
 922
 923         /**
 924          * Is this a key/value store where directories are just virtual?
 925          * Virtual directories exists in so much as files exists that are
 926          * prefixed with the directory path followed by a forward slash.
 927          *
 928          * @return bool
 929          */
 930         abstract protected function directoriesAreVirtual();
 931
 932         /**
 933          * Move a cache entry to the top (such as when accessed)
 934          *
 935          * @param $path string Storage path
 936          */
 937         protected function pingCache( $path ) {
 938                 if ( isset( $this->cache[$path] ) ) {
 939                         $tmp = $this->cache[$path];
 940                         unset( $this->cache[$path] );
 941                         $this->cache[$path] = $tmp;
 942                 }
 943         }
 944
 945         /**
 946          * Prune the inexpensive cache if it is too big to add an item
 947          *
 948          * @return void
 949          */
 950         protected function trimCache() {
 951                 if ( count( $this->cache ) >= $this->maxCacheSize ) {
 952                         reset( $this->cache );
 953                         unset( $this->cache[key( $this->cache )] );
 954                 }
 955         }
 956
 957         /**
 958          * Move a cache entry to the top (such as when accessed)
 959          *
 960          * @param $path string Storage path
 961          */
 962         protected function pingExpensiveCache( $path ) {
 963                 if ( isset( $this->expensiveCache[$path] ) ) {
 964                         $tmp = $this->expensiveCache[$path];
 965                         unset( $this->expensiveCache[$path] );
 966                         $this->expensiveCache[$path] = $tmp;
 967                 }
 968         }
 969
 970         /**
 971          * Prune the expensive cache if it is too big to add an item
 972          *
 973          * @return void
 974          */
 975         protected function trimExpensiveCache() {
 976                 if ( count( $this->expensiveCache ) >= $this->maxExpensiveCacheSize ) {
 977                         reset( $this->expensiveCache );
 978                         unset( $this->expensiveCache[key( $this->expensiveCache )] );
 979                 }
 980         }
 981
 982         /**
 983          * Check if a container name is valid.
 984          * This checks for for length and illegal characters.
 985          *
 986          * @param $container string
 987          * @return bool
 988          */
 989         final protected static function isValidContainerName( $container ) {
 990                 // This accounts for Swift and S3 restrictions while leaving room
 991                 // for things like '.xxx' (hex shard chars) or '.seg' (segments).
 992                 // This disallows directory separators or traversal characters.
 993                 // Note that matching strings URL encode to the same string;
 994                 // in Swift, the length restriction is *after* URL encoding.
 995                 return preg_match( '/^[a-z0-9][a-z0-9-_]{0,199}$/i', $container );
 996         }
 997
 998         /**
 999          * Splits a storage path into an internal container name,
1000          * an internal relative file name, and a container shard suffix.
1001          * Any shard suffix is already appended to the internal container name.
1002          * This also checks that the storage path is valid and within this backend.
1003          *
1004          * If the container is sharded but a suffix could not be determined,
1005          * this means that the path can only refer to a directory and can only
1006          * be scanned by looking in all the container shards.
1007          *
1008          * @param $storagePath string
1009          * @return Array (container, path, container suffix) or (null, null, null) if invalid
1010          */
1011         final protected function resolveStoragePath( $storagePath ) {
1012                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
1013                 if ( $backend === $this->name ) { // must be for this backend
1014                         $relPath = self::normalizeContainerPath( $relPath );
1015                         if ( $relPath !== null ) {
1016                                 // Get shard for the normalized path if this container is sharded
1017                                 $cShard = $this->getContainerShard( $container, $relPath );
1018                                 // Validate and sanitize the relative path (backend-specific)
1019                                 $relPath = $this->resolveContainerPath( $container, $relPath );
1020                                 if ( $relPath !== null ) {
1021                                         // Prepend any wiki ID prefix to the container name
1022                                         $container = $this->fullContainerName( $container );
1023                                         if ( self::isValidContainerName( $container ) ) {
1024                                                 // Validate and sanitize the container name (backend-specific)
1025                                                 $container = $this->resolveContainerName( "{$container}{$cShard}" );
1026                                                 if ( $container !== null ) {
1027                                                         return array( $container, $relPath, $cShard );
1028                                                 }
1029                                         }
1030                                 }
1031                         }
1032                 }
1033                 return array( null, null, null );
1034         }
1035
1036         /**
1037          * Like resolveStoragePath() except null values are returned if
1038          * the container is sharded and the shard could not be determined.
1039          *
1040          * @see FileBackendStore::resolveStoragePath()
1041          *
1042          * @param $storagePath string
1043          * @return Array (container, path) or (null, null) if invalid
1044          */
1045         final protected function resolveStoragePathReal( $storagePath ) {
1046                 list( $container, $relPath, $cShard ) = $this->resolveStoragePath( $storagePath );
1047                 if ( $cShard !== null ) {
1048                         return array( $container, $relPath );
1049                 }
1050                 return array( null, null );
1051         }
1052
1053         /**
1054          * Get the container name shard suffix for a given path.
1055          * Any empty suffix means the container is not sharded.
1056          *
1057          * @param $container string Container name
1058          * @param $relStoragePath string Storage path relative to the container
1059          * @return string|null Returns null if shard could not be determined
1060          */
1061         final protected function getContainerShard( $container, $relPath ) {
1062                 list( $levels, $base, $repeat ) = $this->getContainerHashLevels( $container );
1063                 if ( $levels == 1 || $levels == 2 ) {
1064                         // Hash characters are either base 16 or 36
1065                         $char = ( $base == 36 ) ? '[0-9a-z]' : '[0-9a-f]';
1066                         // Get a regex that represents the shard portion of paths.
1067                         // The concatenation of the captures gives us the shard.
1068                         if ( $levels === 1 ) { // 16 or 36 shards per container
1069                                 $hashDirRegex = '(' . $char . ')';
1070                         } else { // 256 or 1296 shards per container
1071                                 if ( $repeat ) { // verbose hash dir format (e.g. "a/ab/abc")
1072                                         $hashDirRegex = $char . '/(' . $char . '{2})';
1073                                 } else { // short hash dir format (e.g. "a/b/c")
1074                                         $hashDirRegex = '(' . $char . ')/(' . $char . ')';
1075                                 }
1076                         }
1077                         // Allow certain directories to be above the hash dirs so as
1078                         // to work with FileRepo (e.g. "archive/a/ab" or "temp/a/ab").
1079                         // They must be 2+ chars to avoid any hash directory ambiguity.
1080                         $m = array();
1081                         if ( preg_match( "!^(?:[^/]{2,}/)*$hashDirRegex(?:/|$)!", $relPath, $m ) ) {
1082                                 return '.' . implode( '', array_slice( $m, 1 ) );
1083                         }
1084                         return null; // failed to match
1085                 }
1086                 return ''; // no sharding
1087         }
1088
1089         /**
1090          * Check if a storage path maps to a single shard.
1091          * Container dirs like "a", where the container shards on "x/xy",
1092          * can reside on several shards. Such paths are tricky to handle.
1093          *
1094          * @param $storagePath string Storage path
1095          * @return bool
1096          */
1097         final public function isSingleShardPathInternal( $storagePath ) {
1098                 list( $c, $r, $shard ) = $this->resolveStoragePath( $storagePath );
1099                 return ( $shard !== null );
1100         }
1101
1102         /**
1103          * Get the sharding config for a container.
1104          * If greater than 0, then all file storage paths within
1105          * the container are required to be hashed accordingly.
1106          *
1107          * @param $container string
1108          * @return Array (integer levels, integer base, repeat flag) or (0, 0, false)
1109          */
1110         final protected function getContainerHashLevels( $container ) {
1111                 if ( isset( $this->shardViaHashLevels[$container] ) ) {
1112                         $config = $this->shardViaHashLevels[$container];
1113                         $hashLevels = (int)$config['levels'];
1114                         if ( $hashLevels == 1 || $hashLevels == 2 ) {
1115                                 $hashBase = (int)$config['base'];
1116                                 if ( $hashBase == 16 || $hashBase == 36 ) {
1117                                         return array( $hashLevels, $hashBase, $config['repeat'] );
1118                                 }
1119                         }
1120                 }
1121                 return array( 0, 0, false ); // no sharding
1122         }
1123
1124         /**
1125          * Get a list of full container shard suffixes for a container
1126          *
1127          * @param $container string
1128          * @return Array
1129          */
1130         final protected function getContainerSuffixes( $container ) {
1131                 $shards = array();
1132                 list( $digits, $base ) = $this->getContainerHashLevels( $container );
1133                 if ( $digits > 0 ) {
1134                         $numShards = pow( $base, $digits );
1135                         for ( $index = 0; $index < $numShards; $index++ ) {
1136                                 $shards[] = '.' . wfBaseConvert( $index, 10, $base, $digits );
1137                         }
1138                 }
1139                 return $shards;
1140         }
1141
1142         /**
1143          * Get the full container name, including the wiki ID prefix
1144          *
1145          * @param $container string
1146          * @return string
1147          */
1148         final protected function fullContainerName( $container ) {
1149                 if ( $this->wikiId != '' ) {
1150                         return "{$this->wikiId}-$container";
1151                 } else {
1152                         return $container;
1153                 }
1154         }
1155
1156         /**
1157          * Resolve a container name, checking if it's allowed by the backend.
1158          * This is intended for internal use, such as encoding illegal chars.
1159          * Subclasses can override this to be more restrictive.
1160          *
1161          * @param $container string
1162          * @return string|null
1163          */
1164         protected function resolveContainerName( $container ) {
1165                 return $container;
1166         }
1167
1168         /**
1169          * Resolve a relative storage path, checking if it's allowed by the backend.
1170          * This is intended for internal use, such as encoding illegal chars or perhaps
1171          * getting absolute paths (e.g. FS based backends). Note that the relative path
1172          * may be the empty string (e.g. the path is simply to the container).
1173          *
1174          * @param $container string Container name
1175          * @param $relStoragePath string Storage path relative to the container
1176          * @return string|null Path or null if not valid
1177          */
1178         protected function resolveContainerPath( $container, $relStoragePath ) {
1179                 return $relStoragePath;
1180         }
1181
1182         /**
1183          * Get the cache key for a container
1184          *
1185          * @param $container Resolved container name
1186          * @return string
1187          */
1188         private function containerCacheKey( $container ) {
1189                 return wfMemcKey( 'backend', $this->getName(), 'container', $container );
1190         }
1191
1192         /**
1193          * Set the cached info for a container
1194          *
1195          * @param $container Resolved container name
1196          * @param $val mixed Information to cache
1197          * @return void
1198          */
1199         final protected function setContainerCache( $container, $val ) {
1200                 $this->memCache->set( $this->containerCacheKey( $container ), $val, 7*86400 );
1201         }
1202
1203         /**
1204          * Delete the cached info for a container
1205          *
1206          * @param $container Resolved container name
1207          * @return void
1208          */
1209         final protected function deleteContainerCache( $container ) {
1210                 $this->memCache->delete( $this->containerCacheKey( $container ) );
1211         }
1212
1213         /**
1214          * Do a batch lookup from cache for container stats for all containers
1215          * used in a list of container names, storage paths, or FileOp objects.
1216          *
1217          * @param $items Array List of storage paths or FileOps
1218          * @return void
1219          */
1220         final protected function primeContainerCache( array $items ) {
1221                 $paths = array(); // list of storage paths
1222                 $contNames = array(); // (cache key => resolved container name)
1223                 // Get all the paths/containers from the items...
1224                 foreach ( $items as $item ) {
1225                         if ( $item instanceof FileOp ) {
1226                                 $paths = array_merge( $paths, $item->storagePathsRead() );
1227                                 $paths = array_merge( $paths, $item->storagePathsChanged() );
1228                         } elseif ( self::isStoragePath( $item ) ) {
1229                                 $paths[] = $item;
1230                         } elseif ( is_string( $item ) ) { // full container name
1231                                 $contNames[$this->containerCacheKey( $item )] = $item;
1232                         }
1233                 }
1234                 // Get all the corresponding cache keys for paths...
1235                 foreach ( $paths as $path ) {
1236                         list( $fullCont, $r, $s ) = $this->resolveStoragePath( $path );
1237                         if ( $fullCont !== null ) { // valid path for this backend
1238                                 $contNames[$this->containerCacheKey( $fullCont )] = $fullCont;
1239                         }
1240                 }
1241
1242                 $contInfo = array(); // (resolved container name => cache value)
1243                 // Get all cache entries for these container cache keys...
1244                 $values = $this->memCache->getBatch( array_keys( $contNames ) );
1245                 foreach ( $values as $cacheKey => $val ) {
1246                         $contInfo[$contNames[$cacheKey]] = $val;
1247                 }
1248
1249                 // Populate the container process cache for the backend...
1250                 $this->doPrimeContainerCache( array_filter( $contInfo, 'is_array' ) );
1251         }
1252
1253         /**
1254          * Fill the backend-specific process cache given an array of
1255          * resolved container names and their corresponding cached info.
1256          * Only containers that actually exist should appear in the map.
1257          *
1258          * @param $containerInfo Array Map of resolved container names to cached info
1259          * @return void
1260          */
1261         protected function doPrimeContainerCache( array $containerInfo ) {}
1262 }
1263
1264 /**
1265  * FileBackendStore helper function to handle listings that span container shards.
1266  * Do not use this class from places outside of FileBackendStore.
1267  *
1268  * @ingroup FileBackend
1269  */
1270 abstract class FileBackendStoreShardListIterator implements Iterator {
1271         /** @var FileBackendStore */
1272         protected $backend;
1273         /** @var Array */
1274         protected $params;
1275         /** @var Array */
1276         protected $shardSuffixes;
1277         protected $container; // string; full container name
1278         protected $directory; // string; resolved relative path
1279
1280         /** @var Traversable */
1281         protected $iter;
1282         protected $curShard = 0; // integer
1283         protected $pos = 0; // integer
1284
1285         /** @var Array */
1286         protected $multiShardPaths = array(); // (rel path => 1)
1287
1288         /**
1289          * @param $backend FileBackendStore
1290          * @param $container string Full storage container name
1291          * @param $dir string Storage directory relative to container
1292          * @param $suffixes Array List of container shard suffixes
1293          * @param $params Array
1294          */
1295         public function __construct(
1296                 FileBackendStore $backend, $container, $dir, array $suffixes, array $params
1297         ) {
1298                 $this->backend = $backend;
1299                 $this->container = $container;
1300                 $this->directory = $dir;
1301                 $this->shardSuffixes = $suffixes;
1302                 $this->params = $params;
1303         }
1304
1305         /**
1306          * @see Iterator::current()
1307          * @return string|bool String or false
1308          */
1309         public function current() {
1310                 if ( is_array( $this->iter ) ) {
1311                         return current( $this->iter );
1312                 } else {
1313                         return $this->iter->current();
1314                 }
1315         }
1316
1317         /**
1318          * @see Iterator::key()
1319          * @return integer
1320          */
1321         public function key() {
1322                 return $this->pos;
1323         }
1324
1325         /**
1326          * @see Iterator::next()
1327          * @return void
1328          */
1329         public function next() {
1330                 ++$this->pos;
1331                 if ( is_array( $this->iter ) ) {
1332                         next( $this->iter );
1333                 } else {
1334                         $this->iter->next();
1335                 }
1336                 // Filter out items that we already listed
1337                 $this->filterViaNext();
1338                 // Find the next non-empty shard if no elements are left
1339                 $this->nextShardIteratorIfNotValid();
1340         }
1341
1342         /**
1343          * @see Iterator::rewind()
1344          * @return void
1345          */
1346         public function rewind() {
1347                 $this->pos = 0;
1348                 $this->curShard = 0;
1349                 $this->setIteratorFromCurrentShard();
1350                 // Filter out items that we already listed
1351                 $this->filterViaNext();
1352                 // Find the next non-empty shard if this one has no elements
1353                 $this->nextShardIteratorIfNotValid();
1354         }
1355
1356         /**
1357          * @see Iterator::valid()
1358          * @return bool
1359          */
1360         public function valid() {
1361                 if ( $this->iter == null ) {
1362                         return false; // some failure?
1363                 } elseif ( is_array( $this->iter ) ) {
1364                         return ( current( $this->iter ) !== false ); // no paths can have this value
1365                 } else {
1366                         return $this->iter->valid();
1367                 }
1368         }
1369
1370         /**
1371          * Filter out duplicate items by advancing to the next ones
1372          */
1373         protected function filterViaNext() {
1374                 while ( $this->iter->valid() ) {
1375                         $rel = $this->iter->current(); // path relative to given directory
1376                         $path = $this->params['dir'] . "/{$rel}"; // full storage path
1377                         if ( !$this->backend->isSingleShardPathInternal( $path ) ) {
1378                                 // Don't keep listing paths that are on multiple shards
1379                                 if ( isset( $this->multiShardPaths[$rel] ) ) {
1380                                         $this->iter->next(); // we already listed this path
1381                                 } else {
1382                                         $this->multiShardPaths[$rel] = 1;
1383                                         break;
1384                                 }
1385                         }
1386                 }
1387         }
1388
1389         /**
1390          * If the list iterator for this container shard is out of items,
1391          * then move on to the next container that has items.
1392          * If there are none, then it advances to the last container.
1393          */
1394         protected function nextShardIteratorIfNotValid() {
1395                 while ( !$this->valid() ) {
1396                         if ( ++$this->curShard >= count( $this->shardSuffixes ) ) {
1397                                 break; // no more container shards
1398                         }
1399                         $this->setIteratorFromCurrentShard();
1400                 }
1401         }
1402
1403         /**
1404          * Set the list iterator to that of the current container shard
1405          */
1406         protected function setIteratorFromCurrentShard() {
1407                 $suffix = $this->shardSuffixes[$this->curShard];
1408                 $this->iter = $this->listFromShard(
1409                         "{$this->container}{$suffix}", $this->directory, $this->params );
1410         }
1411
1412         /**
1413          * Get the list for a given container shard
1414          *
1415          * @param $container string Resolved container name
1416          * @param $dir string Resolved path relative to container
1417          * @param $params Array
1418          * @return Traversable|Array|null
1419          */
1420         abstract protected function listFromShard( $container, $dir, array $params );
1421 }
1422
1423 /**
1424  * Iterator for listing directories
1425  */
1426 class FileBackendStoreShardDirIterator extends FileBackendStoreShardListIterator {
1427         protected function listFromShard( $container, $dir, array $params ) {
1428                 return $this->backend->getDirectoryListInternal( $container, $dir, $params );
1429         }
1430 }
1431
1432 /**
1433  * Iterator for listing regular files
1434  */
1435 class FileBackendStoreShardFileIterator extends FileBackendStoreShardListIterator {
1436         protected function listFromShard( $container, $dir, array $params ) {
1437                 return $this->backend->getFileListInternal( $container, $dir, $params );
1438         }
1439 }