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         final public function prepare( array $params ) {
 296                 if ( $this->readOnly != '' ) {
 297                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 298                 }
 299                 return $this->doPrepare( $params );
 300         }
 301
 302         /**
 303          * @see FileBackendBase::prepare()
 304          */
 305         abstract protected function doPrepare( array $params );
 306
 307         /**
 308          * Take measures to block web access to a directory and
 309          * the container it belongs to. FS backends might add .htaccess
 310          * files wheras backends like Swift this might restrict container
 311          * access to backend user that represents end-users in web request.
 312          * This is not guaranteed to actually do anything.
 313          *
 314          * $params include:
 315          *     dir       : storage directory
 316          *     noAccess  : try to deny file access
 317          *     noListing : try to deny file listing
 318          *
 319          * @param $params Array
 320          * @return Status
 321          */
 322         final public function secure( array $params ) {
 323                 if ( $this->readOnly != '' ) {
 324                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 325                 }
 326                 return $this->doSecure( $params );
 327         }
 328
 329         /**
 330          * @see FileBackendBase::secure()
 331          */
 332         abstract protected function doSecure( array $params );
 333
 334         /**
 335          * Clean up an empty storage directory.
 336          * On FS backends, the directory will be deleted. Others may do nothing.
 337          *
 338          * $params include:
 339          *     dir : storage directory
 340          *
 341          * @param $params Array
 342          * @return Status
 343          */
 344         final public function clean( array $params ) {
 345                 if ( $this->readOnly != '' ) {
 346                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 347                 }
 348                 return $this->doClean( $params );
 349         }
 350
 351         /**
 352          * @see FileBackendBase::clean()
 353          */
 354         abstract protected function doClean( array $params );
 355
 356         /**
 357          * Check if a file exists at a storage path in the backend.
 358          * This returns false if only a directory exists at the path.
 359          *
 360          * $params include:
 361          *     src    : source storage path
 362          *     latest : use the latest available data
 363          *
 364          * @param $params Array
 365          * @return bool|null Returns null on failure
 366          */
 367         abstract public function fileExists( array $params );
 368
 369         /**
 370          * Get the last-modified timestamp of the file at a storage path.
 371          *
 372          * $params include:
 373          *     src    : source storage path
 374          *     latest : use the latest available data
 375          *
 376          * @param $params Array
 377          * @return string|false TS_MW timestamp or false on failure
 378          */
 379         abstract public function getFileTimestamp( array $params );
 380
 381         /**
 382          * Get the contents of a file at a storage path in the backend.
 383          * This should be avoided for potentially large files.
 384          *
 385          * $params include:
 386          *     src    : source storage path
 387          *     latest : use the latest available data
 388          *
 389          * @param $params Array
 390          * @return string|false Returns false on failure
 391          */
 392         abstract public function getFileContents( array $params );
 393
 394         /**
 395          * Get the size (bytes) of a file at a storage path in the backend.
 396          *
 397          * $params include:
 398          *     src    : source storage path
 399          *     latest : use the latest available data
 400          *
 401          * @param $params Array
 402          * @return integer|false Returns false on failure
 403          */
 404         abstract public function getFileSize( array $params );
 405
 406         /**
 407          * Get quick information about a file at a storage path in the backend.
 408          * If the file does not exist, then this returns false.
 409          * Otherwise, the result is an associative array that includes:
 410          *     mtime  : the last-modified timestamp (TS_MW)
 411          *     size   : the file size (bytes)
 412          *
 413          * $params include:
 414          *     src    : source storage path
 415          *     latest : use the latest available data
 416          *
 417          * @param $params Array
 418          * @return Array|false|null Returns null on failure
 419          */
 420         abstract public function getFileStat( array $params );
 421
 422         /**
 423          * Get a SHA-1 hash of the file at a storage path in the backend.
 424          *
 425          * $params include:
 426          *     src    : source storage path
 427          *     latest : use the latest available data
 428          *
 429          * @param $params Array
 430          * @return string|false Hash string or false on failure
 431          */
 432         abstract public function getFileSha1Base36( array $params );
 433
 434         /**
 435          * Get the properties of the file at a storage path in the backend.
 436          * Returns FSFile::placeholderProps() on failure.
 437          *
 438          * $params include:
 439          *     src    : source storage path
 440          *     latest : use the latest available data
 441          *
 442          * @param $params Array
 443          * @return Array
 444          */
 445         abstract public function getFileProps( array $params );
 446
 447         /**
 448          * Stream the file at a storage path in the backend.
 449          * If the file does not exists, a 404 error will be given.
 450          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
 451          * must be sent if streaming began, while none should be sent otherwise.
 452          * Implementations should flush the output buffer before sending data.
 453          *
 454          * $params include:
 455          *     src     : source storage path
 456          *     headers : additional HTTP headers to send on success
 457          *     latest  : use the latest available data
 458          *
 459          * @param $params Array
 460          * @return Status
 461          */
 462         abstract public function streamFile( array $params );
 463
 464         /**
 465          * Returns a file system file, identical to the file at a storage path.
 466          * The file returned is either:
 467          * a) A local copy of the file at a storage path in the backend.
 468          *    The temporary copy will have the same extension as the source.
 469          * b) An original of the file at a storage path in the backend.
 470          * Temporary files may be purged when the file object falls out of scope.
 471          *
 472          * Write operations should *never* be done on this file as some backends
 473          * may do internal tracking or may be instances of FileBackendMultiWrite.
 474          * In that later case, there are copies of the file that must stay in sync.
 475          *
 476          * $params include:
 477          *     src    : source storage path
 478          *     latest : use the latest available data
 479          *
 480          * @param $params Array
 481          * @return FSFile|null Returns null on failure
 482          */
 483         abstract public function getLocalReference( array $params );
 484
 485         /**
 486          * Get a local copy on disk of the file at a storage path in the backend.
 487          * The temporary copy will have the same file extension as the source.
 488          * Temporary files may be purged when the file object falls out of scope.
 489          *
 490          * $params include:
 491          *     src    : source storage path
 492          *     latest : use the latest available data
 493          *
 494          * @param $params Array
 495          * @return TempFSFile|null Returns null on failure
 496          */
 497         abstract public function getLocalCopy( array $params );
 498
 499         /**
 500          * Get an iterator to list out all stored files under a storage directory.
 501          * If the directory is of the form "mwstore://container", then all items in
 502          * the container should be listed. If of the form "mwstore://container/dir",
 503          * then all items under that container directory should be listed.
 504          * Results should be storage paths relative to the given directory.
 505          *
 506          * $params include:
 507          *     dir : storage path directory
 508          *
 509          * @return Traversable|Array|null Returns null on failure
 510          */
 511         abstract public function getFileList( array $params );
 512
 513         /**
 514          * Invalidate any in-process file existence and property cache.
 515          * If $paths is given, then only the cache for those files will be cleared.
 516          *
 517          * @param $paths Array Storage paths
 518          * @return void
 519          */
 520         abstract public function clearCache( array $paths = null );
 521
 522         /**
 523          * Lock the files at the given storage paths in the backend.
 524          * This will either lock all the files or none (on failure).
 525          *
 526          * Callers should consider using getScopedFileLocks() instead.
 527          *
 528          * @param $paths Array Storage paths
 529          * @param $type integer LockManager::LOCK_* constant
 530          * @return Status
 531          */
 532         final public function lockFiles( array $paths, $type ) {
 533                 return $this->lockManager->lock( $paths, $type );
 534         }
 535
 536         /**
 537          * Unlock the files at the given storage paths in the backend.
 538          *
 539          * @param $paths Array Storage paths
 540          * @param $type integer LockManager::LOCK_* constant
 541          * @return Status
 542          */
 543         final public function unlockFiles( array $paths, $type ) {
 544                 return $this->lockManager->unlock( $paths, $type );
 545         }
 546
 547         /**
 548          * Lock the files at the given storage paths in the backend.
 549          * This will either lock all the files or none (on failure).
 550          * On failure, the status object will be updated with errors.
 551          *
 552          * Once the return value goes out scope, the locks will be released and
 553          * the status updated. Unlock fatals will not change the status "OK" value.
 554          *
 555          * @param $paths Array Storage paths
 556          * @param $type integer LockManager::LOCK_* constant
 557          * @param $status Status Status to update on lock/unlock
 558          * @return ScopedLock|null Returns null on failure
 559          */
 560         final public function getScopedFileLocks( array $paths, $type, Status $status ) {
 561                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status );
 562         }
 563 }
 564
 565 /**
 566  * Base class for all single-write backends.
 567  * This class defines the methods as abstract that subclasses must implement.
 568  * Callers outside of FileBackend and its helper classes, such as FileOp,
 569  * should only call functions that are present in FileBackendBase.
 570  *
 571  * The FileBackendBase operations are implemented using primitive functions
 572  * such as storeInternal(), copyInternal(), deleteInternal() and the like.
 573  * This class is also responsible for path resolution and sanitization.
 574  *
 575  * @ingroup FileBackend
 576  * @since 1.19
 577  */
 578 abstract class FileBackend extends FileBackendBase {
 579         /** @var Array */
 580         protected $cache = array(); // (storage path => key => value)
 581         protected $maxCacheSize = 75; // integer; max paths with entries
 582         /** @var Array */
 583         protected $shardViaHashLevels = array(); // (container name => integer)
 584
 585         /**
 586          * Create a file in the backend with the given contents.
 587          * Do not call this function from places outside FileBackend and FileOp.
 588          *
 589          * $params include:
 590          *     content       : the raw file contents
 591          *     dst           : destination storage path
 592          *     overwriteDest : overwrite any file that exists at the destination
 593          *
 594          * @param $params Array
 595          * @return Status
 596          */
 597         final public function createInternal( array $params ) {
 598                 $status = $this->doCreateInternal( $params );
 599                 $this->clearCache( array( $params['dst'] ) );
 600                 return $status;
 601         }
 602
 603         /**
 604          * @see FileBackend::createInternal()
 605          */
 606         abstract protected function doCreateInternal( array $params );
 607
 608         /**
 609          * Store a file into the backend from a file on disk.
 610          * Do not call this function from places outside FileBackend and FileOp.
 611          *
 612          * $params include:
 613          *     src           : source path on disk
 614          *     dst           : destination storage path
 615          *     overwriteDest : overwrite any file that exists at the destination
 616          *
 617          * @param $params Array
 618          * @return Status
 619          */
 620         final public function storeInternal( array $params ) {
 621                 $status = $this->doStoreInternal( $params );
 622                 $this->clearCache( array( $params['dst'] ) );
 623                 return $status;
 624         }
 625
 626         /**
 627          * @see FileBackend::storeInternal()
 628          */
 629         abstract protected function doStoreInternal( array $params );
 630
 631         /**
 632          * Copy a file from one storage path to another in the backend.
 633          * Do not call this function from places outside FileBackend and FileOp.
 634          *
 635          * $params include:
 636          *     src           : source storage path
 637          *     dst           : destination storage path
 638          *     overwriteDest : overwrite any file that exists at the destination
 639          *
 640          * @param $params Array
 641          * @return Status
 642          */
 643         final public function copyInternal( array $params ) {
 644                 $status = $this->doCopyInternal( $params );
 645                 $this->clearCache( array( $params['dst'] ) );
 646                 return $status;
 647         }
 648
 649         /**
 650          * @see FileBackend::copyInternal()
 651          */
 652         abstract protected function doCopyInternal( array $params );
 653
 654         /**
 655          * Delete a file at the storage path.
 656          * Do not call this function from places outside FileBackend and FileOp.
 657          *
 658          * $params include:
 659          *     src                 : source storage path
 660          *     ignoreMissingSource : do nothing if the source file does not exist
 661          *
 662          * @param $params Array
 663          * @return Status
 664          */
 665         final public function deleteInternal( array $params ) {
 666                 $status = $this->doDeleteInternal( $params );
 667                 $this->clearCache( array( $params['src'] ) );
 668                 return $status;
 669         }
 670
 671         /**
 672          * @see FileBackend::deleteInternal()
 673          */
 674         abstract protected function doDeleteInternal( array $params );
 675
 676         /**
 677          * Move a file from one storage path to another in the backend.
 678          * Do not call this function from places outside FileBackend and FileOp.
 679          *
 680          * $params include:
 681          *     src           : source storage path
 682          *     dst           : destination storage path
 683          *     overwriteDest : overwrite any file that exists at the destination
 684          *
 685          * @param $params Array
 686          * @return Status
 687          */
 688         final public function moveInternal( array $params ) {
 689                 $status = $this->doMoveInternal( $params );
 690                 $this->clearCache( array( $params['src'], $params['dst'] ) );
 691                 return $status;
 692         }
 693
 694         /**
 695          * @see FileBackend::moveInternal()
 696          */
 697         protected function doMoveInternal( array $params ) {
 698                 // Copy source to dest
 699                 $status = $this->copyInternal( $params );
 700                 if ( !$status->isOK() ) {
 701                         return $status;
 702                 }
 703                 // Delete source (only fails due to races or medium going down)
 704                 $status->merge( $this->deleteInternal( array( 'src' => $params['src'] ) ) );
 705                 $status->setResult( true, $status->value ); // ignore delete() errors
 706                 return $status;
 707         }
 708
 709         /**
 710          * @see FileBackendBase::concatenate()
 711          */
 712         final public function concatenate( array $params ) {
 713                 $status = Status::newGood();
 714
 715                 // Try to lock the source files for the scope of this function
 716                 $scopeLockS = $this->getScopedFileLocks( $params['srcs'], LockManager::LOCK_UW, $status );
 717                 if ( !$status->isOK() ) {
 718                         return $status; // abort
 719                 }
 720
 721                 // Actually do the concatenation
 722                 $status->merge( $this->doConcatenate( $params ) );
 723
 724                 return $status;
 725         }
 726
 727         /**
 728          * @see FileBackend::concatenate()
 729          */
 730         protected function doConcatenate( array $params ) {
 731                 $status = Status::newGood();
 732                 $tmpPath = $params['dst']; // convenience
 733
 734                 // Check that the specified temp file is valid...
 735                 wfSuppressWarnings();
 736                 $ok = ( is_file( $tmpPath ) && !filesize( $tmpPath ) );
 737                 wfRestoreWarnings();
 738                 if ( !$ok ) { // not present or not empty
 739                         $status->fatal( 'backend-fail-opentemp', $tmpPath );
 740                         return $status;
 741                 }
 742
 743                 // Build up the temp file using the source chunks (in order)...
 744                 $tmpHandle = fopen( $tmpPath, 'a' );
 745                 if ( $tmpHandle === false ) {
 746                         $status->fatal( 'backend-fail-opentemp', $tmpPath );
 747                         return $status;
 748                 }
 749                 foreach ( $params['srcs'] as $virtualSource ) {
 750                         // Get a local FS version of the chunk
 751                         $tmpFile = $this->getLocalReference( array( 'src' => $virtualSource ) );
 752                         if ( !$tmpFile ) {
 753                                 $status->fatal( 'backend-fail-read', $virtualSource );
 754                                 return $status;
 755                         }
 756                         // Get a handle to the local FS version
 757                         $sourceHandle = fopen( $tmpFile->getPath(), 'r' );
 758                         if ( $sourceHandle === false ) {
 759                                 fclose( $tmpHandle );
 760                                 $status->fatal( 'backend-fail-read', $virtualSource );
 761                                 return $status;
 762                         }
 763                         // Append chunk to file (pass chunk size to avoid magic quotes)
 764                         if ( !stream_copy_to_stream( $sourceHandle, $tmpHandle ) ) {
 765                                 fclose( $sourceHandle );
 766                                 fclose( $tmpHandle );
 767                                 $status->fatal( 'backend-fail-writetemp', $tmpPath );
 768                                 return $status;
 769                         }
 770                         fclose( $sourceHandle );
 771                 }
 772                 if ( !fclose( $tmpHandle ) ) {
 773                         $status->fatal( 'backend-fail-closetemp', $tmpPath );
 774                         return $status;
 775                 }
 776
 777                 return $status;
 778         }
 779
 780         /**
 781          * @see FileBackendBase::doPrepare()
 782          */
 783         final protected function doPrepare( array $params ) {
 784                 $status = Status::newGood();
 785                 list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
 786                 if ( $dir === null ) {
 787                         $status->fatal( 'backend-fail-invalidpath', $params['dir'] );
 788                         return $status; // invalid storage path
 789                 }
 790                 if ( $shard !== null ) { // confined to a single container/shard
 791                         $status->merge( $this->doPrepareInternal( $fullCont, $dir, $params ) );
 792                 } else { // directory is on several shards
 793                         wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
 794                         list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
 795                         foreach ( $this->getContainerSuffixes( $shortCont ) as $suffix ) {
 796                                 $status->merge( $this->doPrepareInternal( "{$fullCont}{$suffix}", $dir, $params ) );
 797                         }
 798                 }
 799                 return $status;
 800         }
 801
 802         /**
 803          * @see FileBackend::doPrepare()
 804          */
 805         protected function doPrepareInternal( $container, $dir, array $params ) {
 806                 return Status::newGood();
 807         }
 808
 809         /**
 810          * @see FileBackendBase::doSecure()
 811          */
 812         final protected function doSecure( array $params ) {
 813                 $status = Status::newGood();
 814                 list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
 815                 if ( $dir === null ) {
 816                         $status->fatal( 'backend-fail-invalidpath', $params['dir'] );
 817                         return $status; // invalid storage path
 818                 }
 819                 if ( $shard !== null ) { // confined to a single container/shard
 820                         $status->merge( $this->doSecureInternal( $fullCont, $dir, $params ) );
 821                 } else { // directory is on several shards
 822                         wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
 823                         list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
 824                         foreach ( $this->getContainerSuffixes( $shortCont ) as $suffix ) {
 825                                 $status->merge( $this->doSecureInternal( "{$fullCont}{$suffix}", $dir, $params ) );
 826                         }
 827                 }
 828                 return $status;
 829         }
 830
 831         /**
 832          * @see FileBackend::doSecure()
 833          */
 834         protected function doSecureInternal( $container, $dir, array $params ) {
 835                 return Status::newGood();
 836         }
 837
 838         /**
 839          * @see FileBackendBase::doClean()
 840          */
 841         final protected function doClean( array $params ) {
 842                 $status = Status::newGood();
 843                 list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
 844                 if ( $dir === null ) {
 845                         $status->fatal( 'backend-fail-invalidpath', $params['dir'] );
 846                         return $status; // invalid storage path
 847                 }
 848                 if ( $shard !== null ) { // confined to a single container/shard
 849                         $status->merge( $this->doCleanInternal( $fullCont, $dir, $params ) );
 850                 } else { // directory is on several shards
 851                         wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
 852                         list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
 853                         foreach ( $this->getContainerSuffixes( $shortCont ) as $suffix ) {
 854                                 $status->merge( $this->doCleanInternal( "{$fullCont}{$suffix}", $dir, $params ) );
 855                         }
 856                 }
 857                 return $status;
 858         }
 859
 860         /**
 861          * @see FileBackend::doClean()
 862          */
 863         protected function doCleanInternal( $container, $dir, array $params ) {
 864                 return Status::newGood();
 865         }
 866
 867         /**
 868          * @see FileBackendBase::fileExists()
 869          */
 870         final public function fileExists( array $params ) {
 871                 $stat = $this->getFileStat( $params );
 872                 if ( $stat === null ) {
 873                         return null; // failure
 874                 }
 875                 return (bool)$stat;
 876         }
 877
 878         /**
 879          * @see FileBackendBase::getFileTimestamp()
 880          */
 881         final public function getFileTimestamp( array $params ) {
 882                 $stat = $this->getFileStat( $params );
 883                 if ( $stat ) {
 884                         return $stat['mtime'];
 885                 } else {
 886                         return false;
 887                 }
 888         }
 889
 890         /**
 891          * @see FileBackendBase::getFileSize()
 892          */
 893         final public function getFileSize( array $params ) {
 894                 $stat = $this->getFileStat( $params );
 895                 if ( $stat ) {
 896                         return $stat['size'];
 897                 } else {
 898                         return false;
 899                 }
 900         }
 901
 902         /**
 903          * @see FileBackendBase::getFileStat()
 904          */
 905         final public function getFileStat( array $params ) {
 906                 $path = $params['src'];
 907                 if ( isset( $this->cache[$path]['stat'] ) ) {
 908                         return $this->cache[$path]['stat'];
 909                 }
 910                 $stat = $this->doGetFileStat( $params );
 911                 if ( is_array( $stat ) ) { // don't cache negatives
 912                         $this->trimCache(); // limit memory
 913                         $this->cache[$path]['stat'] = $stat;
 914                 }
 915                 return $stat;
 916         }
 917
 918         /**
 919          * @see FileBackend::getFileStat()
 920          */
 921         abstract protected function doGetFileStat( array $params );
 922
 923         /**
 924          * @see FileBackendBase::getFileContents()
 925          */
 926         public function getFileContents( array $params ) {
 927                 $tmpFile = $this->getLocalReference( $params );
 928                 if ( !$tmpFile ) {
 929                         return false;
 930                 }
 931                 wfSuppressWarnings();
 932                 $data = file_get_contents( $tmpFile->getPath() );
 933                 wfRestoreWarnings();
 934                 return $data;
 935         }
 936
 937         /**
 938          * @see FileBackendBase::getFileSha1Base36()
 939          */
 940         final public function getFileSha1Base36( array $params ) {
 941                 $path = $params['src'];
 942                 if ( isset( $this->cache[$path]['sha1'] ) ) {
 943                         return $this->cache[$path]['sha1'];
 944                 }
 945                 $hash = $this->doGetFileSha1Base36( $params );
 946                 if ( $hash ) { // don't cache negatives
 947                         $this->trimCache(); // limit memory
 948                         $this->cache[$path]['sha1'] = $hash;
 949                 }
 950                 return $hash;
 951         }
 952
 953         /**
 954          * @see FileBackend::getFileSha1Base36()
 955          */
 956         protected function doGetFileSha1Base36( array $params ) {
 957                 $fsFile = $this->getLocalReference( $params );
 958                 if ( !$fsFile ) {
 959                         return false;
 960                 } else {
 961                         return $fsFile->getSha1Base36();
 962                 }
 963         }
 964
 965         /**
 966          * @see FileBackendBase::getFileProps()
 967          */
 968         public function getFileProps( array $params ) {
 969                 $fsFile = $this->getLocalReference( $params );
 970                 if ( !$fsFile ) {
 971                         return FSFile::placeholderProps();
 972                 } else {
 973                         return $fsFile->getProps();
 974                 }
 975         }
 976
 977         /**
 978          * @see FileBackendBase::getLocalReference()
 979          */
 980         public function getLocalReference( array $params ) {
 981                 $path = $params['src'];
 982                 if ( isset( $this->cache[$path]['localRef'] ) ) {
 983                         return $this->cache[$path]['localRef'];
 984                 }
 985                 $tmpFile = $this->getLocalCopy( $params );
 986                 if ( $tmpFile ) { // don't cache negatives
 987                         $this->trimCache(); // limit memory
 988                         $this->cache[$path]['localRef'] = $tmpFile;
 989                 }
 990                 return $tmpFile;
 991         }
 992
 993         /**
 994          * @see FileBackendBase::streamFile()
 995          */
 996         final public function streamFile( array $params ) {
 997                 $status = Status::newGood();
 998
 999                 $info = $this->getFileStat( $params );
1000                 if ( !$info ) { // let StreamFile handle the 404
1001                         $status->fatal( 'backend-fail-notexists', $params['src'] );
1002                 }
1003
1004                 // Set output buffer and HTTP headers for stream
1005                 $extraHeaders = $params['headers'] ? $params['headers'] : array();
1006                 $res = StreamFile::prepareForStream( $params['src'], $info, $extraHeaders );
1007                 if ( $res == StreamFile::NOT_MODIFIED ) {
1008                         // do nothing; client cache is up to date
1009                 } elseif ( $res == StreamFile::READY_STREAM ) {
1010                         $status = $this->doStreamFile( $params );
1011                 } else {
1012                         $status->fatal( 'backend-fail-stream', $params['src'] );
1013                 }
1014
1015                 return $status;
1016         }
1017
1018         /**
1019          * @see FileBackend::streamFile()
1020          */
1021         protected function doStreamFile( array $params ) {
1022                 $status = Status::newGood();
1023
1024                 $fsFile = $this->getLocalReference( $params );
1025                 if ( !$fsFile ) {
1026                         $status->fatal( 'backend-fail-stream', $params['src'] );
1027                 } elseif ( !readfile( $fsFile->getPath() ) ) {
1028                         $status->fatal( 'backend-fail-stream', $params['src'] );
1029                 }
1030
1031                 return $status;
1032         }
1033
1034         /**
1035          * @see FileBackendBase::getFileList()
1036          */
1037         final public function getFileList( array $params ) {
1038                 list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
1039                 if ( $dir === null ) { // invalid storage path
1040                         return null;
1041                 }
1042                 if ( $shard !== null ) {
1043                         // File listing is confined to a single container/shard
1044                         return $this->getFileListInternal( $fullCont, $dir, $params );
1045                 } else {
1046                         wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
1047                         // File listing spans multiple containers/shards
1048                         list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
1049                         return new ContainerShardListIterator( $this,
1050                                 $fullCont, $this->getContainerSuffixes( $shortCont ), $params );
1051                 }
1052         }
1053
1054         /**
1055          * Do not call this function from places outside FileBackend and ContainerFileListIterator
1056          *
1057          * @param $container string Resolved container name
1058          * @param $dir string Resolved path relative to container
1059          * @param $params Array
1060          * @see FileBackend::getFileList()
1061          */
1062         abstract public function getFileListInternal( $container, $dir, array $params );
1063
1064         /**
1065          * Get the list of supported operations and their corresponding FileOp classes.
1066          *
1067          * @return Array
1068          */
1069         protected function supportedOperations() {
1070                 return array(
1071                         'store'       => 'StoreFileOp',
1072                         'copy'        => 'CopyFileOp',
1073                         'move'        => 'MoveFileOp',
1074                         'delete'      => 'DeleteFileOp',
1075                         'create'      => 'CreateFileOp',
1076                         'null'        => 'NullFileOp'
1077                 );
1078         }
1079
1080         /**
1081          * Return a list of FileOp objects from a list of operations.
1082          * Do not call this function from places outside FileBackend.
1083          *
1084          * The result must have the same number of items as the input.
1085          * An exception is thrown if an unsupported operation is requested.
1086          *
1087          * @param $ops Array Same format as doOperations()
1088          * @return Array List of FileOp objects
1089          * @throws MWException
1090          */
1091         final public function getOperations( array $ops ) {
1092                 $supportedOps = $this->supportedOperations();
1093
1094                 $performOps = array(); // array of FileOp objects
1095                 // Build up ordered array of FileOps...
1096                 foreach ( $ops as $operation ) {
1097                         $opName = $operation['op'];
1098                         if ( isset( $supportedOps[$opName] ) ) {
1099                                 $class = $supportedOps[$opName];
1100                                 // Get params for this operation
1101                                 $params = $operation;
1102                                 // Append the FileOp class
1103                                 $performOps[] = new $class( $this, $params );
1104                         } else {
1105                                 throw new MWException( "Operation `$opName` is not supported." );
1106                         }
1107                 }
1108
1109                 return $performOps;
1110         }
1111
1112         /**
1113          * @see FileBackendBase::doOperationsInternal()
1114          */
1115         protected function doOperationsInternal( array $ops, array $opts ) {
1116                 $status = Status::newGood();
1117
1118                 // Build up a list of FileOps...
1119                 $performOps = $this->getOperations( $ops );
1120
1121                 // Acquire any locks as needed...
1122                 if ( empty( $opts['nonLocking'] ) ) {
1123                         // Build up a list of files to lock...
1124                         $filesLockEx = $filesLockSh = array();
1125                         foreach ( $performOps as $fileOp ) {
1126                                 $filesLockSh = array_merge( $filesLockSh, $fileOp->storagePathsRead() );
1127                                 $filesLockEx = array_merge( $filesLockEx, $fileOp->storagePathsChanged() );
1128                         }
1129                         // Optimization: if doing an EX lock anyway, don't also set an SH one
1130                         $filesLockSh = array_diff( $filesLockSh, $filesLockEx );
1131                         // Try to lock those files for the scope of this function...
1132                         $scopeLockS = $this->getScopedFileLocks( $filesLockSh, LockManager::LOCK_UW, $status );
1133                         $scopeLockE = $this->getScopedFileLocks( $filesLockEx, LockManager::LOCK_EX, $status );
1134                         if ( !$status->isOK() ) {
1135                                 return $status; // abort
1136                         }
1137                 }
1138
1139                 // Clear any cache entries (after locks acquired)
1140                 $this->clearCache();
1141
1142                 // Actually attempt the operation batch...
1143                 $subStatus = FileOp::attemptBatch( $performOps, $opts );
1144
1145                 // Merge errors into status fields
1146                 $status->merge( $subStatus );
1147                 $status->success = $subStatus->success; // not done in merge()
1148
1149                 return $status;
1150         }
1151
1152         /**
1153          * @see FileBackendBase::clearCache()
1154          */
1155         final public function clearCache( array $paths = null ) {
1156                 if ( $paths === null ) {
1157                         $this->cache = array();
1158                 } else {
1159                         foreach ( $paths as $path ) {
1160                                 unset( $this->cache[$path] );
1161                         }
1162                 }
1163         }
1164
1165         /**
1166          * Prune the cache if it is too big to add an item
1167          *
1168          * @return void
1169          */
1170         protected function trimCache() {
1171                 if ( count( $this->cache ) >= $this->maxCacheSize ) {
1172                         reset( $this->cache );
1173                         $key = key( $this->cache );
1174                         unset( $this->cache[$key] );
1175                 }
1176         }
1177
1178         /**
1179          * Check if a given path is a mwstore:// path.
1180          * This does not do any actual validation or existence checks.
1181          *
1182          * @param $path string
1183          * @return bool
1184          */
1185         final public static function isStoragePath( $path ) {
1186                 return ( strpos( $path, 'mwstore://' ) === 0 );
1187         }
1188
1189         /**
1190          * Split a storage path (e.g. "mwstore://backend/container/path/to/object")
1191          * into a backend name, a container name, and a relative object path.
1192          *
1193          * @param $storagePath string
1194          * @return Array (backend, container, rel object) or (null, null, null)
1195          */
1196         final public static function splitStoragePath( $storagePath ) {
1197                 if ( self::isStoragePath( $storagePath ) ) {
1198                         // Note: strlen( 'mwstore://' ) = 10
1199                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
1200                         if ( count( $parts ) == 3 ) {
1201                                 return $parts; // e.g. "backend/container/path"
1202                         } elseif ( count( $parts ) == 2 ) {
1203                                 return array( $parts[0], $parts[1], '' ); // e.g. "backend/container"
1204                         }
1205                 }
1206                 return array( null, null, null );
1207         }
1208
1209         /**
1210          * Check if a container name is valid.
1211          * This checks for for length and illegal characters.
1212          *
1213          * @param $container string
1214          * @return bool
1215          */
1216         final protected static function isValidContainerName( $container ) {
1217                 // This accounts for Swift and S3 restrictions while leaving room
1218                 // for things like '.xxx' (hex shard chars) or '.seg' (segments).
1219                 // Note that matching strings URL encode to the same string;
1220                 // in Swift, the length resriction is *after* URL encoding.
1221                 return preg_match( '/^[a-z0-9][a-z0-9-_]{0,199}$/i', $container );
1222         }
1223
1224         /**
1225          * Validate and normalize a relative storage path.
1226          * Null is returned if the path involves directory traversal.
1227          * Traversal is insecure for FS backends and broken for others.
1228          *
1229          * @param $path string
1230          * @return string|null
1231          */
1232         final protected static function normalizeStoragePath( $path ) {
1233                 // Normalize directory separators
1234                 $path = strtr( $path, '\\', '/' );
1235                 // Use the same traversal protection as Title::secureAndSplit()
1236                 if ( strpos( $path, '.' ) !== false ) {
1237                         if (
1238                                 $path === '.' ||
1239                                 $path === '..' ||
1240                                 strpos( $path, './' ) === 0 ||
1241                                 strpos( $path, '../' ) === 0 ||
1242                                 strpos( $path, '/./' ) !== false ||
1243                                 strpos( $path, '/../' ) !== false
1244                         ) {
1245                                 return null;
1246                         }
1247                 }
1248                 return $path;
1249         }
1250
1251         /**
1252          * Splits a storage path into an internal container name,
1253          * an internal relative file name, and a container shard suffix.
1254          * Any shard suffix is already appended to the internal container name.
1255          * This also checks that the storage path is valid and within this backend.
1256          *
1257          * If the container is sharded but a suffix could not be determined,
1258          * this means that the path can only refer to a directory and can only
1259          * be scanned by looking in all the container shards.
1260          *
1261          * @param $storagePath string
1262          * @return Array (container, path, container suffix) or (null, null, null) if invalid
1263          */
1264         final protected function resolveStoragePath( $storagePath ) {
1265                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
1266                 if ( $backend === $this->name ) { // must be for this backend
1267                         $relPath = self::normalizeStoragePath( $relPath );
1268                         if ( $relPath !== null ) {
1269                                 // Get shard for the normalized path if this container is sharded
1270                                 $cShard = $this->getContainerShard( $container, $relPath );
1271                                 // Validate and sanitize the relative path (backend-specific)
1272                                 $relPath = $this->resolveContainerPath( $container, $relPath );
1273                                 if ( $relPath !== null ) {
1274                                         // Prepend any wiki ID prefix to the container name
1275                                         $container = $this->fullContainerName( $container );
1276                                         if ( self::isValidContainerName( $container ) ) {
1277                                                 // Validate and sanitize the container name (backend-specific)
1278                                                 $container = $this->resolveContainerName( "{$container}{$cShard}" );
1279                                                 if ( $container !== null ) {
1280                                                         return array( $container, $relPath, $cShard );
1281                                                 }
1282                                         }
1283                                 }
1284                         }
1285                 }
1286                 return array( null, null, null );
1287         }
1288
1289         /**
1290          * Like resolveStoragePath() except null values are returned if
1291          * the container is sharded and the shard could not be determined.
1292          *
1293          * @see FileBackend::resolveStoragePath()
1294          *
1295          * @param $storagePath string
1296          * @return Array (container, path) or (null, null) if invalid
1297          */
1298         final protected function resolveStoragePathReal( $storagePath ) {
1299                 list( $container, $relPath, $cShard ) = $this->resolveStoragePath( $storagePath );
1300                 if ( $cShard !== null ) {
1301                         return array( $container, $relPath );
1302                 }
1303                 return array( null, null );
1304         }
1305
1306         /**
1307          * Get the container name shard suffix for a given path.
1308          * Any empty suffix means the container is not sharded.
1309          *
1310          * @param $container string Container name
1311          * @param $relStoragePath string Storage path relative to the container
1312          * @return string|null Returns null if shard could not be determined
1313          */
1314         final protected function getContainerShard( $container, $relPath ) {
1315                 $hashLevels = $this->getContainerHashLevels( $container );
1316                 if ( $hashLevels === 1 ) { // 16 shards per container
1317                         $hashDirRegex = '(?P<shard>[0-9a-f])';
1318                 } elseif ( $hashLevels === 2 ) { // 256 shards per container
1319                         $hashDirRegex = '[0-9a-f]/(?P<shard>[0-9a-f]{2})';
1320                 } else {
1321                         return ''; // no sharding
1322                 }
1323                 // Allow certain directories to be above the hash dirs so as
1324                 // to work with FileRepo (e.g. "archive/a/ab" or "temp/a/ab").
1325                 // They must be 2+ chars to avoid any hash directory ambiguity.
1326                 if ( preg_match( "!^(?:[^/]{2,}/)*$hashDirRegex(?:/|$)!", $relPath, $m ) ) {
1327                         return '.' . str_pad( $m['shard'], $hashLevels, '0', STR_PAD_LEFT );
1328                 }
1329                 return null; // failed to match
1330         }
1331
1332         /**
1333          * Get the number of hash levels for a container.
1334          * If greater than 0, then all file storage paths within
1335          * the container are required to be hashed accordingly.
1336          *
1337          * @param $container string
1338          * @return integer
1339          */
1340         final protected function getContainerHashLevels( $container ) {
1341                 if ( isset( $this->shardViaHashLevels[$container] ) ) {
1342                         $hashLevels = (int)$this->shardViaHashLevels[$container];
1343                         if ( $hashLevels >= 0 && $hashLevels <= 2 ) {
1344                                 return $hashLevels;
1345                         }
1346                 }
1347                 return 0; // no sharding
1348         }
1349
1350         /**
1351          * Get a list of full container shard suffixes for a container
1352          *
1353          * @param $container string
1354          * @return Array
1355          */
1356         final protected function getContainerSuffixes( $container ) {
1357                 $shards = array();
1358                 $digits = $this->getContainerHashLevels( $container );
1359                 if ( $digits > 0 ) {
1360                         $numShards = 1 << ( $digits * 4 );
1361                         for ( $index = 0; $index < $numShards; $index++ ) {
1362                                 $shards[] = '.' . str_pad( dechex( $index ), $digits, '0', STR_PAD_LEFT );
1363                         }
1364                 }
1365                 return $shards;
1366         }
1367
1368         /**
1369          * Get the full container name, including the wiki ID prefix
1370          *
1371          * @param $container string
1372          * @return string
1373          */
1374         final protected function fullContainerName( $container ) {
1375                 if ( $this->wikiId != '' ) {
1376                         return "{$this->wikiId}-$container";
1377                 } else {
1378                         return $container;
1379                 }
1380         }
1381
1382         /**
1383          * Resolve a container name, checking if it's allowed by the backend.
1384          * This is intended for internal use, such as encoding illegal chars.
1385          * Subclasses can override this to be more restrictive.
1386          *
1387          * @param $container string
1388          * @return string|null
1389          */
1390         protected function resolveContainerName( $container ) {
1391                 return $container;
1392         }
1393
1394         /**
1395          * Resolve a relative storage path, checking if it's allowed by the backend.
1396          * This is intended for internal use, such as encoding illegal chars or perhaps
1397          * getting absolute paths (e.g. FS based backends). Note that the relative path
1398          * may be the empty string (e.g. the path is simply to the container).
1399          *
1400          * @param $container string Container name
1401          * @param $relStoragePath string Storage path relative to the container
1402          * @return string|null Path or null if not valid
1403          */
1404         protected function resolveContainerPath( $container, $relStoragePath ) {
1405                 return $relStoragePath;
1406         }
1407
1408         /**
1409          * Get the final extension from a storage or FS path
1410          *
1411          * @param $path string
1412          * @return string
1413          */
1414         final public static function extensionFromPath( $path ) {
1415                 $i = strrpos( $path, '.' );
1416                 return strtolower( $i ? substr( $path, $i + 1 ) : '' );
1417         }
1418 }
1419
1420 /**
1421  * FileBackend helper function to handle file listings that span container shards.
1422  * Do not use this class from places outside of FileBackend.
1423  *
1424  * @ingroup FileBackend
1425  */
1426 class ContainerShardListIterator implements Iterator {
1427         /* @var FileBackend */
1428         protected $backend;
1429         /* @var Array */
1430         protected $params;
1431         /* @var Array */
1432         protected $shardSuffixes;
1433         protected $container; // string
1434         protected $directory; // string
1435
1436         /* @var Traversable */
1437         protected $iter;
1438         protected $curShard = 0; // integer
1439         protected $pos = 0; // integer
1440
1441         /**
1442          * @param $backend FileBackend
1443          * @param $container string Full storage container name
1444          * @param $dir string Storage directory relative to container
1445          * @param $suffixes Array List of container shard suffixes
1446          * @param $params Array
1447          */
1448         public function __construct(
1449                 FileBackend $backend, $container, $dir, array $suffixes, array $params
1450         ) {
1451                 $this->backend = $backend;
1452                 $this->container = $container;
1453                 $this->directory = $dir;
1454                 $this->shardSuffixes = $suffixes;
1455                 $this->params = $params;
1456         }
1457
1458         public function current() {
1459                 if ( is_array( $this->iter ) ) {
1460                         return current( $this->iter );
1461                 } else {
1462                         return $this->iter->current();
1463                 }
1464         }
1465
1466         public function key() {
1467                 return $this->pos;
1468         }
1469
1470         public function next() {
1471                 ++$this->pos;
1472                 if ( is_array( $this->iter ) ) {
1473                         next( $this->iter );
1474                 } else {
1475                         $this->iter->next();
1476                 }
1477                 // Find the next non-empty shard if no elements are left
1478                 $this->nextShardIteratorIfNotValid();
1479         }
1480
1481         /**
1482          * If the iterator for this container shard is out of items,
1483          * then move on to the next container that has items.
1484          * If there are none, then it advances to the last container.
1485          */
1486         protected function nextShardIteratorIfNotValid() {
1487                 while ( !$this->valid() ) {
1488                         if ( ++$this->curShard >= count( $this->shardSuffixes ) ) {
1489                                 break; // no more container shards
1490                         }
1491                         $this->setIteratorFromCurrentShard();
1492                 }
1493         }
1494
1495         protected function setIteratorFromCurrentShard() {
1496                 $suffix = $this->shardSuffixes[$this->curShard];
1497                 $this->iter = $this->backend->getFileListInternal(
1498                         "{$this->container}{$suffix}", $this->directory, $this->params );
1499         }
1500
1501         public function rewind() {
1502                 $this->pos = 0;
1503                 $this->curShard = 0;
1504                 $this->setIteratorFromCurrentShard();
1505                 // Find the next non-empty shard if this one has no elements
1506                 $this->nextShardIteratorIfNotValid();
1507         }
1508
1509         public function valid() {
1510                 if ( $this->iter == null ) {
1511                         return false; // some failure?
1512                 } elseif ( is_array( $this->iter ) ) {
1513                         return ( current( $this->iter ) !== false ); // no paths can have this value
1514                 } else {
1515                         return $this->iter->valid();
1516                 }
1517         }
1518 }