includes/filerepo/backend/FileBackend.php

   1 <?php
   2 /**
   3  * @file
   4  * @ingroup FileBackend
   5  * @author Aaron Schulz
   6  */
   7
   8 /**
   9  * Base class for all file backend classes (including multi-write backends).
  10  * This class defines the methods as abstract that subclasses must implement.
  11  * Outside callers can assume that all backends will have these functions.
  12  *
  13  * All "storage paths" are of the format "mwstore://backend/container/path".
  14  * The paths use UNIX file system (FS) notation, though any particular backend may
  15  * not actually be using a local filesystem. Therefore, the paths are only virtual.
  16  *
  17  * Backend contents are stored under wiki-specific container names by default.
  18  * For legacy reasons, this has no effect for the FS backend class, and per-wiki
  19  * segregation must be done by setting the container paths appropriately.
  20  *
  21  * FS-based backends are somewhat more restrictive due to the existence of real
  22  * directory files; a regular file cannot have the same name as a directory. Other
  23  * backends with virtual directories may not have this limitation. Callers should
  24  * store files in such a way that no files and directories are under the same path.
  25  *
  26  * Methods should avoid throwing exceptions at all costs.
  27  * As a corollary, external dependencies should be kept to a minimum.
  28  *
  29  * @ingroup FileBackend
  30  * @since 1.19
  31  */
  32 abstract class FileBackendBase {
  33         protected $name; // unique backend name
  34         protected $wikiId; // unique wiki name
  35         protected $readOnly; // string
  36         /** @var LockManager */
  37         protected $lockManager;
  38
  39         /**
  40          * Create a new backend instance from configuration.
  41          * This should only be called from within FileBackendGroup.
  42          *
  43          * $config includes:
  44          *     'name'        : The unique name of this backend.
  45          *     'wikiId'      : Prefix to container names that is unique to this wiki.
  46          *                     This should consist of alphanumberic, '-', and '_' chars.
  47          *     'lockManager' : Registered name of a file lock manager to use.
  48          *     'readOnly'    : Write operations are disallowed if this is a non-empty string.
  49          *                     It should be an explanation for the backend being read-only.
  50          *
  51          * @param $config Array
  52          */
  53         public function __construct( array $config ) {
  54                 $this->name = $config['name'];
  55                 $this->wikiId = isset( $config['wikiId'] )
  56                         ? $config['wikiId']
  57                         : wfWikiID(); // e.g. "my_wiki-en_"
  58                 $this->wikiId = $this->resolveWikiId( $this->wikiId );
  59                 $this->lockManager = LockManagerGroup::singleton()->get( $config['lockManager'] );
  60                 $this->readOnly = isset( $config['readOnly'] )
  61                         ? (string)$config['readOnly']
  62                         : '';
  63         }
  64
  65         /**
  66          * Normalize a wiki ID by replacing characters that are
  67          * not supported by the backend as part of container names.
  68          *
  69          * @param $wikiId string
  70          * @return string
  71          */
  72         protected function resolveWikiId( $wikiId ) {
  73                 return $wikiId;
  74         }
  75
  76         /**
  77          * Get the unique backend name.
  78          *
  79          * We may have multiple different backends of the same type.
  80          * For example, we can have two Swift backends using different proxies.
  81          *
  82          * @return string
  83          */
  84         final public function getName() {
  85                 return $this->name;
  86         }
  87
  88         /**
  89          * This is the main entry point into the backend for write operations.
  90          * Callers supply an ordered list of operations to perform as a transaction.
  91          * If any serious errors occur, all attempted operations will be rolled back.
  92          *
  93          * $ops is an array of arrays. The outer array holds a list of operations.
  94          * Each inner array is a set of key value pairs that specify an operation.
  95          *
  96          * Supported operations and their parameters:
  97          * a) Create a new file in storage with the contents of a string
  98          *     array(
  99          *         'op'                  => 'create',
 100          *         'dst'                 => <storage path>,
 101          *         'content'             => <string of new file contents>,
 102          *         'overwriteDest'       => <boolean>,
 103          *         'overwriteSame'       => <boolean>
 104          *     )
 105          * b) Copy a file system file into storage
 106          *     array(
 107          *         'op'                  => 'store',
 108          *         'src'                 => <file system path>,
 109          *         'dst'                 => <storage path>,
 110          *         'overwriteDest'       => <boolean>,
 111          *         'overwriteSame'       => <boolean>
 112          *     )
 113          * c) Copy a file within storage
 114          *     array(
 115          *         'op'                  => 'copy',
 116          *         'src'                 => <storage path>,
 117          *         'dst'                 => <storage path>,
 118          *         'overwriteDest'       => <boolean>,
 119          *         'overwriteSame'       => <boolean>
 120          *     )
 121          * d) Move a file within storage
 122          *     array(
 123          *         'op'                  => 'move',
 124          *         'src'                 => <storage path>,
 125          *         'dst'                 => <storage path>,
 126          *         'overwriteDest'       => <boolean>,
 127          *         'overwriteSame'       => <boolean>
 128          *     )
 129          * e) Delete a file within storage
 130          *     array(
 131          *         'op'                  => 'delete',
 132          *         'src'                 => <storage path>,
 133          *         'ignoreMissingSource' => <boolean>
 134          *     )
 135          * f) Do nothing (no-op)
 136          *     array(
 137          *         'op'                  => 'null',
 138          *     )
 139          *
 140          * Boolean flags for operations (operation-specific):
 141          * 'ignoreMissingSource' : The operation will simply succeed and do
 142          *                         nothing if the source file does not exist.
 143          * 'overwriteDest'       : Any destination file will be overwritten.
 144          * 'overwriteSame'       : An error will not be given if a file already
 145          *                         exists at the destination that has the same
 146          *                         contents as the new contents to be written there.
 147          *
 148          * $opts is an associative of boolean flags, including:
 149          * 'force'               : Errors that would normally cause a rollback do not.
 150          *                         The remaining operations are still attempted if any fail.
 151          * 'nonLocking'          : No locks are acquired for the operations.
 152          *                         This can increase performance for non-critical writes.
 153          *                         This has no effect unless the 'force' flag is set.
 154          * 'allowStale'          : Don't require the latest available data.
 155          *                         This can increase performance for non-critical writes.
 156          *                         This has no effect unless the 'force' flag is set.
 157          *
 158          * Return value:
 159          * This returns a Status, which contains all warnings and fatals that occured
 160          * during the operation. The 'failCount', 'successCount', and 'success' members
 161          * will reflect each operation attempted. The status will be "OK" unless any
 162          * of the operations failed and the 'force' parameter was not set.
 163          *
 164          * @param $ops Array List of operations to execute in order
 165          * @param $opts Array Batch operation options
 166          * @return Status
 167          */
 168         final public function doOperations( array $ops, array $opts = array() ) {
 169                 if ( $this->readOnly != '' ) {
 170                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 171                 }
 172                 if ( empty( $opts['force'] ) ) { // sanity
 173                         unset( $opts['nonLocking'] );
 174                         unset( $opts['allowStale'] );
 175                 }
 176                 return $this->doOperationsInternal( $ops, $opts );
 177         }
 178
 179         /**
 180          * @see FileBackendBase::doOperations()
 181          */
 182         abstract protected function doOperationsInternal( array $ops, array $opts );
 183
 184         /**
 185          * Same as doOperations() except it takes a single operation.
 186          * If you are doing a batch of operations that should either
 187          * all succeed or all fail, then use that function instead.
 188          *
 189          * @see FileBackendBase::doOperations()
 190          *
 191          * @param $op Array Operation
 192          * @param $opts Array Operation options
 193          * @return Status
 194          */
 195         final public function doOperation( array $op, array $opts = array() ) {
 196                 return $this->doOperations( array( $op ), $opts );
 197         }
 198
 199         /**
 200          * Performs a single create operation.
 201          * This sets $params['op'] to 'create' and passes it to doOperation().
 202          *
 203          * @see FileBackendBase::doOperation()
 204          *
 205          * @param $params Array Operation parameters
 206          * @param $opts Array Operation options
 207          * @return Status
 208          */
 209         final public function create( array $params, array $opts = array() ) {
 210                 $params['op'] = 'create';
 211                 return $this->doOperation( $params, $opts );
 212         }
 213
 214         /**
 215          * Performs a single store operation.
 216          * This sets $params['op'] to 'store' and passes it to doOperation().
 217          *
 218          * @see FileBackendBase::doOperation()
 219          *
 220          * @param $params Array Operation parameters
 221          * @param $opts Array Operation options
 222          * @return Status
 223          */
 224         final public function store( array $params, array $opts = array() ) {
 225                 $params['op'] = 'store';
 226                 return $this->doOperation( $params, $opts );
 227         }
 228
 229         /**
 230          * Performs a single copy operation.
 231          * This sets $params['op'] to 'copy' and passes it to doOperation().
 232          *
 233          * @see FileBackendBase::doOperation()
 234          *
 235          * @param $params Array Operation parameters
 236          * @param $opts Array Operation options
 237          * @return Status
 238          */
 239         final public function copy( array $params, array $opts = array() ) {
 240                 $params['op'] = 'copy';
 241                 return $this->doOperation( $params, $opts );
 242         }
 243
 244         /**
 245          * Performs a single move operation.
 246          * This sets $params['op'] to 'move' and passes it to doOperation().
 247          *
 248          * @see FileBackendBase::doOperation()
 249          *
 250          * @param $params Array Operation parameters
 251          * @param $opts Array Operation options
 252          * @return Status
 253          */
 254         final public function move( array $params, array $opts = array() ) {
 255                 $params['op'] = 'move';
 256                 return $this->doOperation( $params, $opts );
 257         }
 258
 259         /**
 260          * Performs a single delete operation.
 261          * This sets $params['op'] to 'delete' and passes it to doOperation().
 262          *
 263          * @see FileBackendBase::doOperation()
 264          *
 265          * @param $params Array Operation parameters
 266          * @param $opts Array Operation options
 267          * @return Status
 268          */
 269         final public function delete( array $params, array $opts = array() ) {
 270                 $params['op'] = 'delete';
 271                 return $this->doOperation( $params, $opts );
 272         }
 273
 274         /**
 275          * Concatenate a list of storage files into a single file on the file system
 276          * $params include:
 277          *     srcs          : ordered source storage paths (e.g. chunk1, chunk2, ...)
 278          *     dst           : file system path to 0-byte temp file
 279          *
 280          * @param $params Array Operation parameters
 281          * @return Status
 282          */
 283         abstract public function concatenate( array $params );
 284
 285         /**
 286          * Prepare a storage path for usage. This will create containers
 287          * that don't yet exist or, on FS backends, create parent directories.
 288          *
 289          * $params include:
 290          *     dir : storage directory
 291          *
 292          * @param $params Array
 293          * @return Status
 294          */
 295         abstract public function prepare( array $params );
 296
 297         /**
 298          * Take measures to block web access to a directory and
 299          * the container it belongs to. FS backends might add .htaccess
 300          * files wheras backends like Swift this might restrict container
 301          * access to backend user that represents end-users in web request.
 302          * This is not guaranteed to actually do anything.
 303          *
 304          * $params include:
 305          *     dir       : storage directory
 306          *     noAccess  : try to deny file access
 307          *     noListing : try to deny file listing
 308          *
 309          * @param $params Array
 310          * @return Status
 311          */
 312         abstract public function secure( array $params );
 313
 314         /**
 315          * Clean up an empty storage directory.
 316          * On FS backends, the directory will be deleted. Others may do nothing.
 317          *
 318          * $params include:
 319          *     dir : storage directory
 320          *
 321          * @param $params Array
 322          * @return Status
 323          */
 324         abstract public function clean( array $params );
 325
 326         /**
 327          * Check if a file exists at a storage path in the backend.
 328          * This returns false if only a directory exists at the path.
 329          *
 330          * $params include:
 331          *     src    : source storage path
 332          *     latest : use the latest available data
 333          *
 334          * @param $params Array
 335          * @return bool|null Returns null on failure
 336          */
 337         abstract public function fileExists( array $params );
 338
 339         /**
 340          * Get the last-modified timestamp of the file at a storage path.
 341          *
 342          * $params include:
 343          *     src    : source storage path
 344          *     latest : use the latest available data
 345          *
 346          * @param $params Array
 347          * @return string|false TS_MW timestamp or false on failure
 348          */
 349         abstract public function getFileTimestamp( array $params );
 350
 351         /**
 352          * Get the contents of a file at a storage path in the backend.
 353          * This should be avoided for potentially large files.
 354          *
 355          * $params include:
 356          *     src    : source storage path
 357          *     latest : use the latest available data
 358          *
 359          * @param $params Array
 360          * @return string|false Returns false on failure
 361          */
 362         abstract public function getFileContents( array $params );
 363
 364         /**
 365          * Get the size (bytes) of a file at a storage path in the backend.
 366          *
 367          * $params include:
 368          *     src    : source storage path
 369          *     latest : use the latest available data
 370          *
 371          * @param $params Array
 372          * @return integer|false Returns false on failure
 373          */
 374         abstract public function getFileSize( array $params );
 375
 376         /**
 377          * Get quick information about a file at a storage path in the backend.
 378          * The result is an associative array that includes:
 379          *     mtime  : the last-modified timestamp (TS_MW) or false
 380          *     size   : the file size (bytes) or false
 381          *
 382          * $params include:
 383          *     src    : source storage path
 384          *     latest : use the latest available data
 385          *
 386          * @param $params Array
 387          * @return Array|false Returns false on failure
 388          */
 389         abstract public function getFileStat( array $params );
 390
 391         /**
 392          * Get a SHA-1 hash of the file at a storage path in the backend.
 393          *
 394          * $params include:
 395          *     src    : source storage path
 396          *     latest : use the latest available data
 397          *
 398          * @param $params Array
 399          * @return string|false Hash string or false on failure
 400          */
 401         abstract public function getFileSha1Base36( array $params );
 402
 403         /**
 404          * Get the properties of the file at a storage path in the backend.
 405          * Returns FSFile::placeholderProps() on failure.
 406          *
 407          * $params include:
 408          *     src    : source storage path
 409          *     latest : use the latest available data
 410          *
 411          * @param $params Array
 412          * @return Array
 413          */
 414         abstract public function getFileProps( array $params );
 415
 416         /**
 417          * Stream the file at a storage path in the backend.
 418          * If the file does not exists, a 404 error will be given.
 419          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
 420          * must be sent if streaming began, while none should be sent otherwise.
 421          * Implementations should flush the output buffer before sending data.
 422          *
 423          * $params include:
 424          *     src     : source storage path
 425          *     headers : additional HTTP headers to send on success
 426          *     latest  : use the latest available data
 427          *
 428          * @param $params Array
 429          * @return Status
 430          */
 431         abstract public function streamFile( array $params );
 432
 433         /**
 434          * Returns a file system file, identical to the file at a storage path.
 435          * The file returned is either:
 436          * a) A local copy of the file at a storage path in the backend.
 437          *    The temporary copy will have the same extension as the source.
 438          * b) An original of the file at a storage path in the backend.
 439          * Temporary files may be purged when the file object falls out of scope.
 440          *
 441          * Write operations should *never* be done on this file as some backends
 442          * may do internal tracking or may be instances of FileBackendMultiWrite.
 443          * In that later case, there are copies of the file that must stay in sync.
 444          *
 445          * $params include:
 446          *     src    : source storage path
 447          *     latest : use the latest available data
 448          *
 449          * @param $params Array
 450          * @return FSFile|null Returns null on failure
 451          */
 452         abstract public function getLocalReference( array $params );
 453
 454         /**
 455          * Get a local copy on disk of the file at a storage path in the backend.
 456          * The temporary copy will have the same file extension as the source.
 457          * Temporary files may be purged when the file object falls out of scope.
 458          *
 459          * $params include:
 460          *     src    : source storage path
 461          *     latest : use the latest available data
 462          *
 463          * @param $params Array
 464          * @return TempFSFile|null Returns null on failure
 465          */
 466         abstract public function getLocalCopy( array $params );
 467
 468         /**
 469          * Get an iterator to list out all stored files under a storage directory.
 470          * If the directory is of the form "mwstore://container", then all items in
 471          * the container should be listed. If of the form "mwstore://container/dir",
 472          * then all items under that container directory should be listed.
 473          * Results should be storage paths relative to the given directory.
 474          *
 475          * $params include:
 476          *     dir : storage path directory
 477          *
 478          * @return Traversable|Array|null Returns null on failure
 479          */
 480         abstract public function getFileList( array $params );
 481
 482         /**
 483          * Invalidate any in-process file existence and property cache.
 484          * If $paths is given, then only the cache for those files will be cleared.
 485          *
 486          * @param $paths Array Storage paths
 487          * @return void
 488          */
 489         abstract public function clearCache( array $paths = null );
 490
 491         /**
 492          * Lock the files at the given storage paths in the backend.
 493          * This will either lock all the files or none (on failure).
 494          *
 495          * Callers should consider using getScopedFileLocks() instead.
 496          *
 497          * @param $paths Array Storage paths
 498          * @param $type integer LockManager::LOCK_* constant
 499          * @return Status
 500          */
 501         final public function lockFiles( array $paths, $type ) {
 502                 return $this->lockManager->lock( $paths, $type );
 503         }
 504
 505         /**
 506          * Unlock the files at the given storage paths in the backend.
 507          *
 508          * @param $paths Array Storage paths
 509          * @param $type integer LockManager::LOCK_* constant
 510          * @return Status
 511          */
 512         final public function unlockFiles( array $paths, $type ) {
 513                 return $this->lockManager->unlock( $paths, $type );
 514         }
 515
 516         /**
 517          * Lock the files at the given storage paths in the backend.
 518          * This will either lock all the files or none (on failure).
 519          * On failure, the status object will be updated with errors.
 520          *
 521          * Once the return value goes out scope, the locks will be released and
 522          * the status updated. Unlock fatals will not change the status "OK" value.
 523          *
 524          * @param $paths Array Storage paths
 525          * @param $type integer LockManager::LOCK_* constant
 526          * @param $status Status Status to update on lock/unlock
 527          * @return ScopedLock|null Returns null on failure
 528          */
 529         final public function getScopedFileLocks( array $paths, $type, Status $status ) {
 530                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status );
 531         }
 532 }
 533
 534 /**
 535  * Base class for all single-write backends.
 536  * This class defines the methods as abstract that subclasses must implement.
 537  * Callers outside of FileBackend and its helper classes, such as FileOp,
 538  * should only call functions that are present in FileBackendBase.
 539  *
 540  * The FileBackendBase operations are implemented using primitive functions
 541  * such as storeInternal(), copyInternal(), deleteInternal() and the like.
 542  * This class is also responsible for path resolution and sanitization.
 543  *
 544  * @ingroup FileBackend
 545  * @since 1.19
 546  */
 547 abstract class FileBackend extends FileBackendBase {
 548         /** @var Array */
 549         protected $cache = array(); // (storage path => key => value)
 550         protected $maxCacheSize = 75; // integer; max paths with entries
 551         /** @var Array */
 552         protected $shardViaHashLevels = array(); // (container name => integer)
 553
 554         /**
 555          * Create a file in the backend with the given contents.
 556          * Do not call this function from places outside FileBackend and FileOp.
 557          *
 558          * $params include:
 559          *     content       : the raw file contents
 560          *     dst           : destination storage path
 561          *     overwriteDest : overwrite any file that exists at the destination
 562          *
 563          * @param $params Array
 564          * @return Status
 565          */
 566         final public function createInternal( array $params ) {
 567                 $status = $this->doCreateInternal( $params );
 568                 $this->clearCache( array( $params['dst'] ) );
 569                 return $status;
 570         }
 571
 572         /**
 573          * @see FileBackend::createInternal()
 574          */
 575         abstract protected function doCreateInternal( array $params );
 576
 577         /**
 578          * Store a file into the backend from a file on disk.
 579          * Do not call this function from places outside FileBackend and FileOp.
 580          *
 581          * $params include:
 582          *     src           : source path on disk
 583          *     dst           : destination storage path
 584          *     overwriteDest : overwrite any file that exists at the destination
 585          *
 586          * @param $params Array
 587          * @return Status
 588          */
 589         final public function storeInternal( array $params ) {
 590                 $status = $this->doStoreInternal( $params );
 591                 $this->clearCache( array( $params['dst'] ) );
 592                 return $status;
 593         }
 594
 595         /**
 596          * @see FileBackend::storeInternal()
 597          */
 598         abstract protected function doStoreInternal( array $params );
 599
 600         /**
 601          * Copy a file from one storage path to another in the backend.
 602          * Do not call this function from places outside FileBackend and FileOp.
 603          *
 604          * $params include:
 605          *     src           : source storage path
 606          *     dst           : destination storage path
 607          *     overwriteDest : overwrite any file that exists at the destination
 608          *
 609          * @param $params Array
 610          * @return Status
 611          */
 612         final public function copyInternal( array $params ) {
 613                 $status = $this->doCopyInternal( $params );
 614                 $this->clearCache( array( $params['dst'] ) );
 615                 return $status;
 616         }
 617
 618         /**
 619          * @see FileBackend::copyInternal()
 620          */
 621         abstract protected function doCopyInternal( array $params );
 622
 623         /**
 624          * Delete a file at the storage path.
 625          * Do not call this function from places outside FileBackend and FileOp.
 626          *
 627          * $params include:
 628          *     src                 : source storage path
 629          *     ignoreMissingSource : do nothing if the source file does not exist
 630          *
 631          * @param $params Array
 632          * @return Status
 633          */
 634         final public function deleteInternal( array $params ) {
 635                 $status = $this->doDeleteInternal( $params );
 636                 $this->clearCache( array( $params['src'] ) );
 637                 return $status;
 638         }
 639
 640         /**
 641          * @see FileBackend::deleteInternal()
 642          */
 643         abstract protected function doDeleteInternal( array $params );
 644
 645         /**
 646          * Move a file from one storage path to another in the backend.
 647          * Do not call this function from places outside FileBackend and FileOp.
 648          *
 649          * $params include:
 650          *     src           : source storage path
 651          *     dst           : destination storage path
 652          *     overwriteDest : overwrite any file that exists at the destination
 653          *
 654          * @param $params Array
 655          * @return Status
 656          */
 657         final public function moveInternal( array $params ) {
 658                 $status = $this->doMoveInternal( $params );
 659                 $this->clearCache( array( $params['src'], $params['dst'] ) );
 660                 return $status;
 661         }
 662
 663         /**
 664          * @see FileBackend::moveInternal()
 665          */
 666         protected function doMoveInternal( array $params ) {
 667                 // Copy source to dest
 668                 $status = $this->copyInternal( $params );
 669                 if ( !$status->isOK() ) {
 670                         return $status;
 671                 }
 672                 // Delete source (only fails due to races or medium going down)
 673                 $status->merge( $this->deleteInternal( array( 'src' => $params['src'] ) ) );
 674                 $status->setResult( true, $status->value ); // ignore delete() errors
 675                 return $status;
 676         }
 677
 678         /**
 679          * @see FileBackendBase::concatenate()
 680          */
 681         final public function concatenate( array $params ) {
 682                 $status = Status::newGood();
 683
 684                 // Try to lock the source files for the scope of this function
 685                 $scopeLockS = $this->getScopedFileLocks( $params['srcs'], LockManager::LOCK_UW, $status );
 686                 if ( !$status->isOK() ) {
 687                         return $status; // abort
 688                 }
 689
 690                 // Actually do the concatenation
 691                 $status->merge( $this->doConcatenate( $params ) );
 692
 693                 return $status;
 694         }
 695
 696         /**
 697          * @see FileBackend::concatenate()
 698          */
 699         protected function doConcatenate( array $params ) {
 700                 $status = Status::newGood();
 701                 $tmpPath = $params['dst']; // convenience
 702
 703                 // Check that the specified temp file is valid...
 704                 wfSuppressWarnings();
 705                 $ok = ( is_file( $tmpPath ) && !filesize( $tmpPath ) );
 706                 wfRestoreWarnings();
 707                 if ( !$ok ) { // not present or not empty
 708                         $status->fatal( 'backend-fail-opentemp', $tmpPath );
 709                         return $status;
 710                 }
 711
 712                 // Build up the temp file using the source chunks (in order)...
 713                 $tmpHandle = fopen( $tmpPath, 'a' );
 714                 if ( $tmpHandle === false ) {
 715                         $status->fatal( 'backend-fail-opentemp', $tmpPath );
 716                         return $status;
 717                 }
 718                 foreach ( $params['srcs'] as $virtualSource ) {
 719                         // Get a local FS version of the chunk
 720                         $tmpFile = $this->getLocalReference( array( 'src' => $virtualSource ) );
 721                         if ( !$tmpFile ) {
 722                                 $status->fatal( 'backend-fail-read', $virtualSource );
 723                                 return $status;
 724                         }
 725                         // Get a handle to the local FS version
 726                         $sourceHandle = fopen( $tmpFile->getPath(), 'r' );
 727                         if ( $sourceHandle === false ) {
 728                                 fclose( $tmpHandle );
 729                                 $status->fatal( 'backend-fail-read', $virtualSource );
 730                                 return $status;
 731                         }
 732                         // Append chunk to file (pass chunk size to avoid magic quotes)
 733                         if ( !stream_copy_to_stream( $sourceHandle, $tmpHandle ) ) {
 734                                 fclose( $sourceHandle );
 735                                 fclose( $tmpHandle );
 736                                 $status->fatal( 'backend-fail-writetemp', $tmpPath );
 737                                 return $status;
 738                         }
 739                         fclose( $sourceHandle );
 740                 }
 741                 if ( !fclose( $tmpHandle ) ) {
 742                         $status->fatal( 'backend-fail-closetemp', $tmpPath );
 743                         return $status;
 744                 }
 745
 746                 return $status;
 747         }
 748
 749         /**
 750          * @see FileBackendBase::prepare()
 751          */
 752         final public function prepare( array $params ) {
 753                 $status = Status::newGood();
 754                 list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
 755                 if ( $dir === null ) {
 756                         $status->fatal( 'backend-fail-invalidpath', $params['dir'] );
 757                         return $status; // invalid storage path
 758                 }
 759                 if ( $shard !== null ) { // confined to a single container/shard
 760                         $status->merge( $this->doPrepare( $fullCont, $dir, $params ) );
 761                 } else { // directory is on several shards
 762                         wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
 763                         list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
 764                         foreach ( $this->getContainerSuffixes( $shortCont ) as $suffix ) {
 765                                 $status->merge( $this->doPrepare( "{$fullCont}{$suffix}", $dir, $params ) );
 766                         }
 767                 }
 768                 return $status;
 769         }
 770
 771         /**
 772          * @see FileBackend::prepare()
 773          */
 774         protected function doPrepare( $container, $dir, array $params ) {
 775                 return Status::newGood();
 776         }
 777
 778         /**
 779          * @see FileBackendBase::secure()
 780          */
 781         final public function secure( array $params ) {
 782                 $status = Status::newGood();
 783                 list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
 784                 if ( $dir === null ) {
 785                         $status->fatal( 'backend-fail-invalidpath', $params['dir'] );
 786                         return $status; // invalid storage path
 787                 }
 788                 if ( $shard !== null ) { // confined to a single container/shard
 789                         $status->merge( $this->doSecure( $fullCont, $dir, $params ) );
 790                 } else { // directory is on several shards
 791                         wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
 792                         list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
 793                         foreach ( $this->getContainerSuffixes( $shortCont ) as $suffix ) {
 794                                 $status->merge( $this->doSecure( "{$fullCont}{$suffix}", $dir, $params ) );
 795                         }
 796                 }
 797                 return $status;
 798         }
 799
 800         /**
 801          * @see FileBackend::secure()
 802          */
 803         protected function doSecure( $container, $dir, array $params ) {
 804                 return Status::newGood();
 805         }
 806
 807         /**
 808          * @see FileBackendBase::clean()
 809          */
 810         final public function clean( array $params ) {
 811                 $status = Status::newGood();
 812                 list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
 813                 if ( $dir === null ) {
 814                         $status->fatal( 'backend-fail-invalidpath', $params['dir'] );
 815                         return $status; // invalid storage path
 816                 }
 817                 if ( $shard !== null ) { // confined to a single container/shard
 818                         $status->merge( $this->doClean( $fullCont, $dir, $params ) );
 819                 } else { // directory is on several shards
 820                         wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
 821                         list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
 822                         foreach ( $this->getContainerSuffixes( $shortCont ) as $suffix ) {
 823                                 $status->merge( $this->doClean( "{$fullCont}{$suffix}", $dir, $params ) );
 824                         }
 825                 }
 826                 return $status;
 827         }
 828
 829         /**
 830          * @see FileBackend::clean()
 831          */
 832         protected function doClean( $container, $dir, array $params ) {
 833                 return Status::newGood();
 834         }
 835
 836         /**
 837          * @see FileBackendBase::fileExists()
 838          */
 839         final public function fileExists( array $params ) {
 840                 return (bool)$this->getFileStat( $params );
 841         }
 842
 843         /**
 844          * @see FileBackendBase::getFileTimestamp()
 845          */
 846         final public function getFileTimestamp( array $params ) {
 847                 $stat = $this->getFileStat( $params );
 848                 if ( $stat ) {
 849                         return $stat['mtime'];
 850                 } else {
 851                         return false;
 852                 }
 853         }
 854
 855         /**
 856          * @see FileBackendBase::getFileSize()
 857          */
 858         final public function getFileSize( array $params ) {
 859                 $stat = $this->getFileStat( $params );
 860                 if ( $stat ) {
 861                         return $stat['size'];
 862                 } else {
 863                         return false;
 864                 }
 865         }
 866
 867         /**
 868          * @see FileBackendBase::getFileStat()
 869          */
 870         final public function getFileStat( array $params ) {
 871                 $path = $params['src'];
 872                 if ( isset( $this->cache[$path]['stat'] ) ) {
 873                         return $this->cache[$path]['stat'];
 874                 }
 875                 $stat = $this->doGetFileStat( $params );
 876                 if ( is_array( $stat ) ) { // don't cache negatives
 877                         $this->trimCache(); // limit memory
 878                         $this->cache[$path]['stat'] = $stat;
 879                 }
 880                 return $stat;
 881         }
 882
 883         /**
 884          * @see FileBackend::getFileStat()
 885          */
 886         abstract protected function doGetFileStat( array $params );
 887
 888         /**
 889          * @see FileBackendBase::getFileContents()
 890          */
 891         public function getFileContents( array $params ) {
 892                 $tmpFile = $this->getLocalReference( $params );
 893                 if ( !$tmpFile ) {
 894                         return false;
 895                 }
 896                 wfSuppressWarnings();
 897                 $data = file_get_contents( $tmpFile->getPath() );
 898                 wfRestoreWarnings();
 899                 return $data;
 900         }
 901
 902         /**
 903          * @see FileBackendBase::getFileSha1Base36()
 904          */
 905         final public function getFileSha1Base36( array $params ) {
 906                 $path = $params['src'];
 907                 if ( isset( $this->cache[$path]['sha1'] ) ) {
 908                         return $this->cache[$path]['sha1'];
 909                 }
 910                 $hash = $this->doGetFileSha1Base36( $params );
 911                 if ( $hash ) { // don't cache negatives
 912                         $this->trimCache(); // limit memory
 913                         $this->cache[$path]['sha1'] = $hash;
 914                 }
 915                 return $hash;
 916         }
 917
 918         /**
 919          * @see FileBackend::getFileSha1Base36()
 920          */
 921         protected function doGetFileSha1Base36( array $params ) {
 922                 $fsFile = $this->getLocalReference( $params );
 923                 if ( !$fsFile ) {
 924                         return false;
 925                 } else {
 926                         return $fsFile->getSha1Base36();
 927                 }
 928         }
 929
 930         /**
 931          * @see FileBackendBase::getFileProps()
 932          */
 933         public function getFileProps( array $params ) {
 934                 $fsFile = $this->getLocalReference( $params );
 935                 if ( !$fsFile ) {
 936                         return FSFile::placeholderProps();
 937                 } else {
 938                         return $fsFile->getProps();
 939                 }
 940         }
 941
 942         /**
 943          * @see FileBackendBase::getLocalReference()
 944          */
 945         public function getLocalReference( array $params ) {
 946                 $path = $params['src'];
 947                 if ( isset( $this->cache[$path]['localRef'] ) ) {
 948                         return $this->cache[$path]['localRef'];
 949                 }
 950                 $tmpFile = $this->getLocalCopy( $params );
 951                 if ( $tmpFile ) { // don't cache negatives
 952                         $this->trimCache(); // limit memory
 953                         $this->cache[$path]['localRef'] = $tmpFile;
 954                 }
 955                 return $tmpFile;
 956         }
 957
 958         /**
 959          * @see FileBackendBase::streamFile()
 960          */
 961         final public function streamFile( array $params ) {
 962                 $status = Status::newGood();
 963
 964                 $info = $this->getFileStat( $params );
 965                 if ( !$info ) { // let StreamFile handle the 404
 966                         $status->fatal( 'backend-fail-notexists', $params['src'] );
 967                 }
 968
 969                 // Set output buffer and HTTP headers for stream
 970                 $extraHeaders = $params['headers'] ? $params['headers'] : array();
 971                 $res = StreamFile::prepareForStream( $params['src'], $info, $extraHeaders );
 972                 if ( $res == StreamFile::NOT_MODIFIED ) {
 973                         // do nothing; client cache is up to date
 974                 } elseif ( $res == StreamFile::READY_STREAM ) {
 975                         $status = $this->doStreamFile( $params );
 976                 } else {
 977                         $status->fatal( 'backend-fail-stream', $params['src'] );
 978                 }
 979
 980                 return $status;
 981         }
 982
 983         /**
 984          * @see FileBackend::streamFile()
 985          */
 986         protected function doStreamFile( array $params ) {
 987                 $status = Status::newGood();
 988
 989                 $fsFile = $this->getLocalReference( $params );
 990                 if ( !$fsFile ) {
 991                         $status->fatal( 'backend-fail-stream', $params['src'] );
 992                 } elseif ( !readfile( $fsFile->getPath() ) ) {
 993                         $status->fatal( 'backend-fail-stream', $params['src'] );
 994                 }
 995
 996                 return $status;
 997         }
 998
 999         /**
1000          * @see FileBackendBase::getFileList()
1001          */
1002         final public function getFileList( array $params ) {
1003                 list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
1004                 if ( $dir === null ) { // invalid storage path
1005                         return null;
1006                 }
1007                 if ( $shard !== null ) {
1008                         // File listing is confined to a single container/shard
1009                         return $this->getFileListInternal( $fullCont, $dir, $params );
1010                 } else {
1011                         wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
1012                         // File listing spans multiple containers/shards
1013                         list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
1014                         return new ContainerShardListIterator( $this,
1015                                 $fullCont, $this->getContainerSuffixes( $shortCont ), $params );
1016                 }
1017         }
1018
1019         /**
1020          * Do not call this function from places outside FileBackend and ContainerFileListIterator
1021          *
1022          * @param $container string Resolved container name
1023          * @param $dir string Resolved path relative to container
1024          * @param $params Array
1025          * @see FileBackend::getFileList()
1026          */
1027         abstract public function getFileListInternal( $container, $dir, array $params );
1028
1029         /**
1030          * Get the list of supported operations and their corresponding FileOp classes.
1031          *
1032          * @return Array
1033          */
1034         protected function supportedOperations() {
1035                 return array(
1036                         'store'       => 'StoreFileOp',
1037                         'copy'        => 'CopyFileOp',
1038                         'move'        => 'MoveFileOp',
1039                         'delete'      => 'DeleteFileOp',
1040                         'create'      => 'CreateFileOp',
1041                         'null'        => 'NullFileOp'
1042                 );
1043         }
1044
1045         /**
1046          * Return a list of FileOp objects from a list of operations.
1047          * Do not call this function from places outside FileBackend.
1048          *
1049          * The result must have the same number of items as the input.
1050          * An exception is thrown if an unsupported operation is requested.
1051          *
1052          * @param $ops Array Same format as doOperations()
1053          * @return Array List of FileOp objects
1054          * @throws MWException
1055          */
1056         final public function getOperations( array $ops ) {
1057                 $supportedOps = $this->supportedOperations();
1058
1059                 $performOps = array(); // array of FileOp objects
1060                 // Build up ordered array of FileOps...
1061                 foreach ( $ops as $operation ) {
1062                         $opName = $operation['op'];
1063                         if ( isset( $supportedOps[$opName] ) ) {
1064                                 $class = $supportedOps[$opName];
1065                                 // Get params for this operation
1066                                 $params = $operation;
1067                                 // Append the FileOp class
1068                                 $performOps[] = new $class( $this, $params );
1069                         } else {
1070                                 throw new MWException( "Operation `$opName` is not supported." );
1071                         }
1072                 }
1073
1074                 return $performOps;
1075         }
1076
1077         /**
1078          * @see FileBackendBase::doOperationsInternal()
1079          */
1080         protected function doOperationsInternal( array $ops, array $opts ) {
1081                 $status = Status::newGood();
1082
1083                 // Build up a list of FileOps...
1084                 $performOps = $this->getOperations( $ops );
1085
1086                 // Acquire any locks as needed...
1087                 if ( empty( $opts['nonLocking'] ) ) {
1088                         // Build up a list of files to lock...
1089                         $filesLockEx = $filesLockSh = array();
1090                         foreach ( $performOps as $fileOp ) {
1091                                 $filesLockSh = array_merge( $filesLockSh, $fileOp->storagePathsRead() );
1092                                 $filesLockEx = array_merge( $filesLockEx, $fileOp->storagePathsChanged() );
1093                         }
1094                         // Optimization: if doing an EX lock anyway, don't also set an SH one
1095                         $filesLockSh = array_diff( $filesLockSh, $filesLockEx );
1096                         // Try to lock those files for the scope of this function...
1097                         $scopeLockS = $this->getScopedFileLocks( $filesLockSh, LockManager::LOCK_UW, $status );
1098                         $scopeLockE = $this->getScopedFileLocks( $filesLockEx, LockManager::LOCK_EX, $status );
1099                         if ( !$status->isOK() ) {
1100                                 return $status; // abort
1101                         }
1102                 }
1103
1104                 // Clear any cache entries (after locks acquired)
1105                 $this->clearCache();
1106
1107                 // Actually attempt the operation batch...
1108                 $subStatus = FileOp::attemptBatch( $performOps, $opts );
1109
1110                 // Merge errors into status fields
1111                 $status->merge( $subStatus );
1112                 $status->success = $subStatus->success; // not done in merge()
1113
1114                 return $status;
1115         }
1116
1117         /**
1118          * @see FileBackendBase::clearCache()
1119          */
1120         final public function clearCache( array $paths = null ) {
1121                 if ( $paths === null ) {
1122                         $this->cache = array();
1123                 } else {
1124                         foreach ( $paths as $path ) {
1125                                 unset( $this->cache[$path] );
1126                         }
1127                 }
1128         }
1129
1130         /**
1131          * Prune the cache if it is too big to add an item
1132          *
1133          * @return void
1134          */
1135         protected function trimCache() {
1136                 if ( count( $this->cache ) >= $this->maxCacheSize ) {
1137                         reset( $this->cache );
1138                         $key = key( $this->cache );
1139                         unset( $this->cache[$key] );
1140                 }
1141         }
1142
1143         /**
1144          * Check if a given path is a mwstore:// path.
1145          * This does not do any actual validation or existence checks.
1146          *
1147          * @param $path string
1148          * @return bool
1149          */
1150         final public static function isStoragePath( $path ) {
1151                 return ( strpos( $path, 'mwstore://' ) === 0 );
1152         }
1153
1154         /**
1155          * Split a storage path (e.g. "mwstore://backend/container/path/to/object")
1156          * into a backend name, a container name, and a relative object path.
1157          *
1158          * @param $storagePath string
1159          * @return Array (backend, container, rel object) or (null, null, null)
1160          */
1161         final public static function splitStoragePath( $storagePath ) {
1162                 if ( self::isStoragePath( $storagePath ) ) {
1163                         // Note: strlen( 'mwstore://' ) = 10
1164                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
1165                         if ( count( $parts ) == 3 ) {
1166                                 return $parts; // e.g. "backend/container/path"
1167                         } elseif ( count( $parts ) == 2 ) {
1168                                 return array( $parts[0], $parts[1], '' ); // e.g. "backend/container"
1169                         }
1170                 }
1171                 return array( null, null, null );
1172         }
1173
1174         /**
1175          * Check if a container name is valid.
1176          * This checks for for length and illegal characters.
1177          *
1178          * @param $container string
1179          * @return bool
1180          */
1181         final protected static function isValidContainerName( $container ) {
1182                 // This accounts for Swift and S3 restrictions while leaving room
1183                 // for things like '.xxx' (hex shard chars) or '.seg' (segments).
1184                 // Note that matching strings URL encode to the same string;
1185                 // in Swift, the length resriction is *after* URL encoding.
1186                 return preg_match( '/^[a-z0-9][a-z0-9-_]{0,199}$/i', $container );
1187         }
1188
1189         /**
1190          * Validate and normalize a relative storage path.
1191          * Null is returned if the path involves directory traversal.
1192          * Traversal is insecure for FS backends and broken for others.
1193          *
1194          * @param $path string
1195          * @return string|null
1196          */
1197         final protected static function normalizeStoragePath( $path ) {
1198                 // Normalize directory separators
1199                 $path = strtr( $path, '\\', '/' );
1200                 // Use the same traversal protection as Title::secureAndSplit()
1201                 if ( strpos( $path, '.' ) !== false ) {
1202                         if (
1203                                 $path === '.' ||
1204                                 $path === '..' ||
1205                                 strpos( $path, './' ) === 0 ||
1206                                 strpos( $path, '../' ) === 0 ||
1207                                 strpos( $path, '/./' ) !== false ||
1208                                 strpos( $path, '/../' ) !== false
1209                         ) {
1210                                 return null;
1211                         }
1212                 }
1213                 return $path;
1214         }
1215
1216         /**
1217          * Splits a storage path into an internal container name,
1218          * an internal relative file name, and a container shard suffix.
1219          * Any shard suffix is already appended to the internal container name.
1220          * This also checks that the storage path is valid and within this backend.
1221          *
1222          * If the container is sharded but a suffix could not be determined,
1223          * this means that the path can only refer to a directory and can only
1224          * be scanned by looking in all the container shards.
1225          *
1226          * @param $storagePath string
1227          * @return Array (container, path, container suffix) or (null, null, null) if invalid
1228          */
1229         final protected function resolveStoragePath( $storagePath ) {
1230                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
1231                 if ( $backend === $this->name ) { // must be for this backend
1232                         $relPath = self::normalizeStoragePath( $relPath );
1233                         if ( $relPath !== null ) {
1234                                 // Get shard for the normalized path if this container is sharded
1235                                 $cShard = $this->getContainerShard( $container, $relPath );
1236                                 // Validate and sanitize the relative path (backend-specific)
1237                                 $relPath = $this->resolveContainerPath( $container, $relPath );
1238                                 if ( $relPath !== null ) {
1239                                         // Prepend any wiki ID prefix to the container name
1240                                         $container = $this->fullContainerName( $container );
1241                                         if ( self::isValidContainerName( $container ) ) {
1242                                                 // Validate and sanitize the container name (backend-specific)
1243                                                 $container = $this->resolveContainerName( "{$container}{$cShard}" );
1244                                                 if ( $container !== null ) {
1245                                                         return array( $container, $relPath, $cShard );
1246                                                 }
1247                                         }
1248                                 }
1249                         }
1250                 }
1251                 return array( null, null, null );
1252         }
1253
1254         /**
1255          * Like resolveStoragePath() except null values are returned if
1256          * the container is sharded and the shard could not be determined.
1257          *
1258          * @see FileBackend::resolveStoragePath()
1259          *
1260          * @param $storagePath string
1261          * @return Array (container, path) or (null, null) if invalid
1262          */
1263         final protected function resolveStoragePathReal( $storagePath ) {
1264                 list( $container, $relPath, $cShard ) = $this->resolveStoragePath( $storagePath );
1265                 if ( $cShard !== null ) {
1266                         return array( $container, $relPath );
1267                 }
1268                 return array( null, null );
1269         }
1270
1271         /**
1272          * Get the container name shard suffix for a given path.
1273          * Any empty suffix means the container is not sharded.
1274          *
1275          * @param $container string Container name
1276          * @param $relStoragePath string Storage path relative to the container
1277          * @return string|null Returns null if shard could not be determined
1278          */
1279         final protected function getContainerShard( $container, $relPath ) {
1280                 $hashLevels = $this->getContainerHashLevels( $container );
1281                 if ( $hashLevels === 1 ) { // 16 shards per container
1282                         $hashDirRegex = '(?P<shard>[0-9a-f])';
1283                 } elseif ( $hashLevels === 2 ) { // 256 shards per container
1284                         $hashDirRegex = '[0-9a-f]/(?P<shard>[0-9a-f]{2})';
1285                 } else {
1286                         return ''; // no sharding
1287                 }
1288                 // Allow certain directories to be above the hash dirs so as
1289                 // to work with FileRepo (e.g. "archive/a/ab" or "temp/a/ab").
1290                 // They must be 2+ chars to avoid any hash directory ambiguity.
1291                 if ( preg_match( "!^(?:[^/]{2,}/)*$hashDirRegex(?:/|$)!", $relPath, $m ) ) {
1292                         return '.' . str_pad( $m['shard'], $hashLevels, '0', STR_PAD_LEFT );
1293                 }
1294                 return null; // failed to match
1295         }
1296
1297         /**
1298          * Get the number of hash levels for a container.
1299          * If greater than 0, then all file storage paths within
1300          * the container are required to be hashed accordingly.
1301          *
1302          * @param $container string
1303          * @return integer
1304          */
1305         final protected function getContainerHashLevels( $container ) {
1306                 if ( isset( $this->shardViaHashLevels[$container] ) ) {
1307                         $hashLevels = (int)$this->shardViaHashLevels[$container];
1308                         if ( $hashLevels >= 0 && $hashLevels <= 2 ) {
1309                                 return $hashLevels;
1310                         }
1311                 }
1312                 return 0; // no sharding
1313         }
1314
1315         /**
1316          * Get a list of full container shard suffixes for a container
1317          *
1318          * @param $container string
1319          * @return Array
1320          */
1321         final protected function getContainerSuffixes( $container ) {
1322                 $shards = array();
1323                 $digits = $this->getContainerHashLevels( $container );
1324                 if ( $digits > 0 ) {
1325                         $numShards = 1 << ( $digits * 4 );
1326                         for ( $index = 0; $index < $numShards; $index++ ) {
1327                                 $shards[] = '.' . str_pad( dechex( $index ), $digits, '0', STR_PAD_LEFT );
1328                         }
1329                 }
1330                 return $shards;
1331         }
1332
1333         /**
1334          * Get the full container name, including the wiki ID prefix
1335          *
1336          * @param $container string
1337          * @return string
1338          */
1339         final protected function fullContainerName( $container ) {
1340                 if ( $this->wikiId != '' ) {
1341                         return "{$this->wikiId}-$container";
1342                 } else {
1343                         return $container;
1344                 }
1345         }
1346
1347         /**
1348          * Resolve a container name, checking if it's allowed by the backend.
1349          * This is intended for internal use, such as encoding illegal chars.
1350          * Subclasses can override this to be more restrictive.
1351          *
1352          * @param $container string
1353          * @return string|null
1354          */
1355         protected function resolveContainerName( $container ) {
1356                 return $container;
1357         }
1358
1359         /**
1360          * Resolve a relative storage path, checking if it's allowed by the backend.
1361          * This is intended for internal use, such as encoding illegal chars or perhaps
1362          * getting absolute paths (e.g. FS based backends). Note that the relative path
1363          * may be the empty string (e.g. the path is simply to the container).
1364          *
1365          * @param $container string Container name
1366          * @param $relStoragePath string Storage path relative to the container
1367          * @return string|null Path or null if not valid
1368          */
1369         protected function resolveContainerPath( $container, $relStoragePath ) {
1370                 return $relStoragePath;
1371         }
1372
1373         /**
1374          * Get the final extension from a storage or FS path
1375          *
1376          * @param $path string
1377          * @return string
1378          */
1379         final public static function extensionFromPath( $path ) {
1380                 $i = strrpos( $path, '.' );
1381                 return strtolower( $i ? substr( $path, $i + 1 ) : '' );
1382         }
1383 }
1384
1385 /**
1386  * FileBackend helper function to handle file listings that span container shards.
1387  * Do not use this class from places outside of FileBackend.
1388  *
1389  * @ingroup FileBackend
1390  */
1391 class ContainerShardListIterator implements Iterator {
1392         /* @var FileBackend */
1393         protected $backend;
1394         /* @var Array */
1395         protected $params;
1396         /* @var Array */
1397         protected $shardSuffixes;
1398         protected $container; // string
1399         protected $directory; // string
1400
1401         /* @var Traversable */
1402         protected $iter;
1403         protected $curShard = 0; // integer
1404         protected $pos = 0; // integer
1405
1406         /**
1407          * @param $backend FileBackend
1408          * @param $container string Full storage container name
1409          * @param $dir string Storage directory relative to container
1410          * @param $suffixes Array List of container shard suffixes
1411          * @param $params Array
1412          */
1413         public function __construct(
1414                 FileBackend $backend, $container, $dir, array $suffixes, array $params
1415         ) {
1416                 $this->backend = $backend;
1417                 $this->container = $container;
1418                 $this->directory = $dir;
1419                 $this->shardSuffixes = $suffixes;
1420                 $this->params = $params;
1421         }
1422
1423         public function current() {
1424                 if ( is_array( $this->iter ) ) {
1425                         return current( $this->iter );
1426                 } else {
1427                         return $this->iter->current();
1428                 }
1429         }
1430
1431         public function key() {
1432                 return $this->pos;
1433         }
1434
1435         public function next() {
1436                 ++$this->pos;
1437                 if ( is_array( $this->iter ) ) {
1438                         next( $this->iter );
1439                 } else {
1440                         $this->iter->next();
1441                 }
1442                 // Find the next non-empty shard if no elements are left
1443                 $this->nextShardIteratorIfNotValid();
1444         }
1445
1446         /**
1447          * If the iterator for this container shard is out of items,
1448          * then move on to the next container that has items.
1449          * If there are none, then it advances to the last container.
1450          */
1451         protected function nextShardIteratorIfNotValid() {
1452                 while ( !$this->valid() ) {
1453                         if ( ++$this->curShard >= count( $this->shardSuffixes ) ) {
1454                                 break; // no more container shards
1455                         }
1456                         $this->setIteratorFromCurrentShard();
1457                 }
1458         }
1459
1460         protected function setIteratorFromCurrentShard() {
1461                 $suffix = $this->shardSuffixes[$this->curShard];
1462                 $this->iter = $this->backend->getFileListInternal(
1463                         "{$this->container}{$suffix}", $this->directory, $this->params );
1464         }
1465
1466         public function rewind() {
1467                 $this->pos = 0;
1468                 $this->curShard = 0;
1469                 $this->setIteratorFromCurrentShard();
1470                 // Find the next non-empty shard if this one has no elements
1471                 $this->nextShardIteratorIfNotValid();
1472         }
1473
1474         public function valid() {
1475                 if ( $this->iter == null ) {
1476                         return false; // some failure?
1477                 } elseif ( is_array( $this->iter ) ) {
1478                         return ( current( $this->iter ) !== false ); // no paths can have this value
1479                 } else {
1480                         return $this->iter->valid();
1481                 }
1482         }
1483 }