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