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                 $defaultConfig = array(
  55                         'lockManager' => null,
  56                 );
  57                 $config = array_merge(  $defaultConfig, $config );
  58                 $this->name = $config['name'];
  59                 $this->wikiId = isset( $config['wikiId'] )
  60                         ? $config['wikiId']
  61                         : wfWikiID(); // e.g. "my_wiki-en_"
  62                 $this->wikiId = $this->resolveWikiId( $this->wikiId );
  63                 $this->lockManager = LockManagerGroup::singleton()->get( $config['lockManager'] );
  64                 $this->readOnly = isset( $config['readOnly'] )
  65                         ? (string)$config['readOnly']
  66                         : '';
  67         }
  68
  69         /**
  70          * Normalize a wiki ID by replacing characters that are
  71          * not supported by the backend as part of container names.
  72          *
  73          * @param $wikiId string
  74          * @return string
  75          */
  76         protected function resolveWikiId( $wikiId ) {
  77                 return $wikiId;
  78         }
  79
  80         /**
  81          * Get the unique backend name.
  82          * We may have multiple different backends of the same type.
  83          * For example, we can have two Swift backends using different proxies.
  84          *
  85          * @return string
  86          */
  87         final public function getName() {
  88                 return $this->name;
  89         }
  90
  91         /**
  92          * This is the main entry point into the backend for write operations.
  93          * Callers supply an ordered list of operations to perform as a transaction.
  94          * If any serious errors occur, all attempted operations will be rolled back.
  95          *
  96          * $ops is an array of arrays. The outer array holds a list of operations.
  97          * Each inner array is a set of key value pairs that specify an operation.
  98          *
  99          * Supported operations and their parameters:
 100          * a) Create a new file in storage with the contents of a string
 101          *     array(
 102          *         'op'                  => 'create',
 103          *         'dst'                 => <storage path>,
 104          *         'content'             => <string of new file contents>,
 105          *         'overwrite'           => <boolean>,
 106          *         'overwriteSame'       => <boolean>
 107          *     )
 108          * b) Copy a file system file into storage
 109          *     array(
 110          *         'op'                  => 'store',
 111          *         'src'                 => <file system path>,
 112          *         'dst'                 => <storage path>,
 113          *         'overwrite'           => <boolean>,
 114          *         'overwriteSame'       => <boolean>
 115          *     )
 116          * c) Copy a file within storage
 117          *     array(
 118          *         'op'                  => 'copy',
 119          *         'src'                 => <storage path>,
 120          *         'dst'                 => <storage path>,
 121          *         'overwrite'           => <boolean>,
 122          *         'overwriteSame'       => <boolean>
 123          *     )
 124          * d) Move a file within storage
 125          *     array(
 126          *         'op'                  => 'move',
 127          *         'src'                 => <storage path>,
 128          *         'dst'                 => <storage path>,
 129          *         'overwrite'           => <boolean>,
 130          *         'overwriteSame'       => <boolean>
 131          *     )
 132          * e) Delete a file within storage
 133          *     array(
 134          *         'op'                  => 'delete',
 135          *         'src'                 => <storage path>,
 136          *         'ignoreMissingSource' => <boolean>
 137          *     )
 138          * f) Do nothing (no-op)
 139          *     array(
 140          *         'op'                  => 'null',
 141          *     )
 142          *
 143          * Boolean flags for operations (operation-specific):
 144          * 'ignoreMissingSource' : The operation will simply succeed and do
 145          *                         nothing if the source file does not exist.
 146          * 'overwrite'           : Any destination file will be overwritten.
 147          * 'overwriteSame'       : An error will not be given if a file already
 148          *                         exists at the destination that has the same
 149          *                         contents as the new contents to be written there.
 150          *
 151          * $opts is an associative of boolean flags, including:
 152          * 'force'               : Errors that would normally cause a rollback do not.
 153          *                         The remaining operations are still attempted if any fail.
 154          * 'nonLocking'          : No locks are acquired for the operations.
 155          *                         This can increase performance for non-critical writes.
 156          *                         This has no effect unless the 'force' flag is set.
 157          * 'allowStale'          : Don't require the latest available data.
 158          *                         This can increase performance for non-critical writes.
 159          *                         This has no effect unless the 'force' flag is set.
 160          *
 161          * Remarks:
 162          * File system paths given to operations should refer to files that are
 163          * either locked or otherwise safe from modification from other processes.
 164          * Normally these files will be new temp files, which should be adequate.
 165          *
 166          * Return value:
 167          * This returns a Status, which contains all warnings and fatals that occured
 168          * during the operation. The 'failCount', 'successCount', and 'success' members
 169          * will reflect each operation attempted. The status will be "OK" unless any
 170          * of the operations failed and the 'force' parameter was not set.
 171          *
 172          * @param $ops Array List of operations to execute in order
 173          * @param $opts Array Batch operation options
 174          * @return Status
 175          */
 176         final public function doOperations( array $ops, array $opts = array() ) {
 177                 if ( $this->readOnly != '' ) {
 178                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 179                 }
 180                 if ( empty( $opts['force'] ) ) { // sanity
 181                         unset( $opts['nonLocking'] );
 182                         unset( $opts['allowStale'] );
 183                 }
 184                 return $this->doOperationsInternal( $ops, $opts );
 185         }
 186
 187         /**
 188          * @see FileBackendBase::doOperations()
 189          */
 190         abstract protected function doOperationsInternal( array $ops, array $opts );
 191
 192         /**
 193          * Same as doOperations() except it takes a single operation.
 194          * If you are doing a batch of operations that should either
 195          * all succeed or all fail, then use that function instead.
 196          *
 197          * @see FileBackendBase::doOperations()
 198          *
 199          * @param $op Array Operation
 200          * @param $opts Array Operation options
 201          * @return Status
 202          */
 203         final public function doOperation( array $op, array $opts = array() ) {
 204                 return $this->doOperations( array( $op ), $opts );
 205         }
 206
 207         /**
 208          * Performs a single create operation.
 209          * This sets $params['op'] to 'create' and passes it to doOperation().
 210          *
 211          * @see FileBackendBase::doOperation()
 212          *
 213          * @param $params Array Operation parameters
 214          * @param $opts Array Operation options
 215          * @return Status
 216          */
 217         final public function create( array $params, array $opts = array() ) {
 218                 $params['op'] = 'create';
 219                 return $this->doOperation( $params, $opts );
 220         }
 221
 222         /**
 223          * Performs a single store operation.
 224          * This sets $params['op'] to 'store' and passes it to doOperation().
 225          *
 226          * @see FileBackendBase::doOperation()
 227          *
 228          * @param $params Array Operation parameters
 229          * @param $opts Array Operation options
 230          * @return Status
 231          */
 232         final public function store( array $params, array $opts = array() ) {
 233                 $params['op'] = 'store';
 234                 return $this->doOperation( $params, $opts );
 235         }
 236
 237         /**
 238          * Performs a single copy operation.
 239          * This sets $params['op'] to 'copy' and passes it to doOperation().
 240          *
 241          * @see FileBackendBase::doOperation()
 242          *
 243          * @param $params Array Operation parameters
 244          * @param $opts Array Operation options
 245          * @return Status
 246          */
 247         final public function copy( array $params, array $opts = array() ) {
 248                 $params['op'] = 'copy';
 249                 return $this->doOperation( $params, $opts );
 250         }
 251
 252         /**
 253          * Performs a single move operation.
 254          * This sets $params['op'] to 'move' and passes it to doOperation().
 255          *
 256          * @see FileBackendBase::doOperation()
 257          *
 258          * @param $params Array Operation parameters
 259          * @param $opts Array Operation options
 260          * @return Status
 261          */
 262         final public function move( array $params, array $opts = array() ) {
 263                 $params['op'] = 'move';
 264                 return $this->doOperation( $params, $opts );
 265         }
 266
 267         /**
 268          * Performs a single delete operation.
 269          * This sets $params['op'] to 'delete' and passes it to doOperation().
 270          *
 271          * @see FileBackendBase::doOperation()
 272          *
 273          * @param $params Array Operation parameters
 274          * @param $opts Array Operation options
 275          * @return Status
 276          */
 277         final public function delete( array $params, array $opts = array() ) {
 278                 $params['op'] = 'delete';
 279                 return $this->doOperation( $params, $opts );
 280         }
 281
 282         /**
 283          * Concatenate a list of storage files into a single file on the file system
 284          * $params include:
 285          *     srcs          : ordered source storage paths (e.g. chunk1, chunk2, ...)
 286          *     dst           : file system path to 0-byte temp file
 287          *
 288          * @param $params Array Operation parameters
 289          * @return Status
 290          */
 291         abstract public function concatenate( array $params );
 292
 293         /**
 294          * Prepare a storage directory for usage.
 295          * This will create any required containers and parent directories.
 296          * Backends using key/value stores only need to create the container.
 297          *
 298          * $params include:
 299          *     dir : storage directory
 300          *
 301          * @param $params Array
 302          * @return Status
 303          */
 304         final public function prepare( array $params ) {
 305                 if ( $this->readOnly != '' ) {
 306                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 307                 }
 308                 return $this->doPrepare( $params );
 309         }
 310
 311         /**
 312          * @see FileBackendBase::prepare()
 313          */
 314         abstract protected function doPrepare( array $params );
 315
 316         /**
 317          * Take measures to block web access to a storage directory and
 318          * the container it belongs to. FS backends might add .htaccess
 319          * files whereas key/value store backends might restrict container
 320          * access to the auth user that represents end-users in web request.
 321          * This is not guaranteed to actually do anything.
 322          *
 323          * $params include:
 324          *     dir       : storage directory
 325          *     noAccess  : try to deny file access
 326          *     noListing : try to deny file listing
 327          *
 328          * @param $params Array
 329          * @return Status
 330          */
 331         final public function secure( array $params ) {
 332                 if ( $this->readOnly != '' ) {
 333                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 334                 }
 335                 $status = $this->doPrepare( $params ); // dir must exist to restrict it
 336                 if ( $status->isOK() ) {
 337                         $status->merge( $this->doSecure( $params ) );
 338                 }
 339                 return $status;
 340         }
 341
 342         /**
 343          * @see FileBackendBase::secure()
 344          */
 345         abstract protected function doSecure( array $params );
 346
 347         /**
 348          * Delete a storage directory if it is empty.
 349          * Backends using key/value stores may do nothing unless the directory
 350          * is that of an empty container, in which case it should be deleted.
 351          *
 352          * $params include:
 353          *     dir : storage directory
 354          *
 355          * @param $params Array
 356          * @return Status
 357          */
 358         final public function clean( array $params ) {
 359                 if ( $this->readOnly != '' ) {
 360                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 361                 }
 362                 return $this->doClean( $params );
 363         }
 364
 365         /**
 366          * @see FileBackendBase::clean()
 367          */
 368         abstract protected function doClean( array $params );
 369
 370         /**
 371          * Check if a file exists at a storage path in the backend.
 372          * This returns false if only a directory exists at the path.
 373          *
 374          * $params include:
 375          *     src    : source storage path
 376          *     latest : use the latest available data
 377          *
 378          * @param $params Array
 379          * @return bool|null Returns null on failure
 380          */
 381         abstract public function fileExists( array $params );
 382
 383         /**
 384          * Get the last-modified timestamp of the file at a storage path.
 385          *
 386          * $params include:
 387          *     src    : source storage path
 388          *     latest : use the latest available data
 389          *
 390          * @param $params Array
 391          * @return string|false TS_MW timestamp or false on failure
 392          */
 393         abstract public function getFileTimestamp( array $params );
 394
 395         /**
 396          * Get the contents of a file at a storage path in the backend.
 397          * This should be avoided for potentially large files.
 398          *
 399          * $params include:
 400          *     src    : source storage path
 401          *     latest : use the latest available data
 402          *
 403          * @param $params Array
 404          * @return string|false Returns false on failure
 405          */
 406         abstract public function getFileContents( array $params );
 407
 408         /**
 409          * Get the size (bytes) of a file at a storage path in the backend.
 410          *
 411          * $params include:
 412          *     src    : source storage path
 413          *     latest : use the latest available data
 414          *
 415          * @param $params Array
 416          * @return integer|false Returns false on failure
 417          */
 418         abstract public function getFileSize( array $params );
 419
 420         /**
 421          * Get quick information about a file at a storage path in the backend.
 422          * If the file does not exist, then this returns false.
 423          * Otherwise, the result is an associative array that includes:
 424          *     mtime  : the last-modified timestamp (TS_MW)
 425          *     size   : the file size (bytes)
 426          * Additional values may be included for internal use only.
 427          *
 428          * $params include:
 429          *     src    : source storage path
 430          *     latest : use the latest available data
 431          *
 432          * @param $params Array
 433          * @return Array|false|null Returns null on failure
 434          */
 435         abstract public function getFileStat( array $params );
 436
 437         /**
 438          * Get a SHA-1 hash of the file at a storage path in the backend.
 439          *
 440          * $params include:
 441          *     src    : source storage path
 442          *     latest : use the latest available data
 443          *
 444          * @param $params Array
 445          * @return string|false Hash string or false on failure
 446          */
 447         abstract public function getFileSha1Base36( array $params );
 448
 449         /**
 450          * Get the properties of the file at a storage path in the backend.
 451          * Returns FSFile::placeholderProps() on failure.
 452          *
 453          * $params include:
 454          *     src    : source storage path
 455          *     latest : use the latest available data
 456          *
 457          * @param $params Array
 458          * @return Array
 459          */
 460         abstract public function getFileProps( array $params );
 461
 462         /**
 463          * Stream the file at a storage path in the backend.
 464          * If the file does not exists, a 404 error will be given.
 465          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
 466          * must be sent if streaming began, while none should be sent otherwise.
 467          * Implementations should flush the output buffer before sending data.
 468          *
 469          * $params include:
 470          *     src     : source storage path
 471          *     headers : additional HTTP headers to send on success
 472          *     latest  : use the latest available data
 473          *
 474          * @param $params Array
 475          * @return Status
 476          */
 477         abstract public function streamFile( array $params );
 478
 479         /**
 480          * Returns a file system file, identical to the file at a storage path.
 481          * The file returned is either:
 482          * a) A local copy of the file at a storage path in the backend.
 483          *    The temporary copy will have the same extension as the source.
 484          * b) An original of the file at a storage path in the backend.
 485          * Temporary files may be purged when the file object falls out of scope.
 486          *
 487          * Write operations should *never* be done on this file as some backends
 488          * may do internal tracking or may be instances of FileBackendMultiWrite.
 489          * In that later case, there are copies of the file that must stay in sync.
 490          *
 491          * $params include:
 492          *     src    : source storage path
 493          *     latest : use the latest available data
 494          *
 495          * @param $params Array
 496          * @return FSFile|null Returns null on failure
 497          */
 498         abstract public function getLocalReference( array $params );
 499
 500         /**
 501          * Get a local copy on disk of the file at a storage path in the backend.
 502          * The temporary copy will have the same file extension as the source.
 503          * Temporary files may be purged when the file object falls out of scope.
 504          *
 505          * $params include:
 506          *     src    : source storage path
 507          *     latest : use the latest available data
 508          *
 509          * @param $params Array
 510          * @return TempFSFile|null Returns null on failure
 511          */
 512         abstract public function getLocalCopy( array $params );
 513
 514         /**
 515          * Get an iterator to list out all stored files under a storage directory.
 516          * If the directory is of the form "mwstore://container", then all items in
 517          * the container should be listed. If of the form "mwstore://container/dir",
 518          * then all items under that container directory should be listed.
 519          * Results should be storage paths relative to the given directory.
 520          *
 521          * $params include:
 522          *     dir : storage path directory
 523          *
 524          * @return Traversable|Array|null Returns null on failure
 525          */
 526         abstract public function getFileList( array $params );
 527
 528         /**
 529          * Invalidate any in-process file existence and property cache.
 530          * If $paths is given, then only the cache for those files will be cleared.
 531          *
 532          * @param $paths Array Storage paths (optional)
 533          * @return void
 534          */
 535         abstract public function clearCache( array $paths = null );
 536
 537         /**
 538          * Lock the files at the given storage paths in the backend.
 539          * This will either lock all the files or none (on failure).
 540          *
 541          * Callers should consider using getScopedFileLocks() instead.
 542          *
 543          * @param $paths Array Storage paths
 544          * @param $type integer LockManager::LOCK_* constant
 545          * @return Status
 546          */
 547         final public function lockFiles( array $paths, $type ) {
 548                 return $this->lockManager->lock( $paths, $type );
 549         }
 550
 551         /**
 552          * Unlock the files at the given storage paths in the backend.
 553          *
 554          * @param $paths Array Storage paths
 555          * @param $type integer LockManager::LOCK_* constant
 556          * @return Status
 557          */
 558         final public function unlockFiles( array $paths, $type ) {
 559                 return $this->lockManager->unlock( $paths, $type );
 560         }
 561
 562         /**
 563          * Lock the files at the given storage paths in the backend.
 564          * This will either lock all the files or none (on failure).
 565          * On failure, the status object will be updated with errors.
 566          *
 567          * Once the return value goes out scope, the locks will be released and
 568          * the status updated. Unlock fatals will not change the status "OK" value.
 569          *
 570          * @param $paths Array Storage paths
 571          * @param $type integer LockManager::LOCK_* constant
 572          * @param $status Status Status to update on lock/unlock
 573          * @return ScopedLock|null Returns null on failure
 574          */
 575         final public function getScopedFileLocks( array $paths, $type, Status $status ) {
 576                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status );
 577         }
 578 }
 579
 580 /**
 581  * Base class for all single-write backends.
 582  * This class defines the methods as abstract that subclasses must implement.
 583  * Callers outside of FileBackend and its helper classes, such as FileOp,
 584  * should only call functions that are present in FileBackendBase.
 585  *
 586  * The FileBackendBase operations are implemented using primitive functions
 587  * such as storeInternal(), copyInternal(), deleteInternal() and the like.
 588  * This class is also responsible for path resolution and sanitization.
 589  *
 590  * @ingroup FileBackend
 591  * @since 1.19
 592  */
 593 abstract class FileBackend extends FileBackendBase {
 594         /** @var Array */
 595         protected $cache = array(); // (storage path => key => value)
 596         protected $maxCacheSize = 75; // integer; max paths with entries
 597         /** @var Array */
 598         protected $shardViaHashLevels = array(); // (container name => integer)
 599
 600         protected $maxFileSize = 1000000000; // integer bytes (1GB)
 601
 602         /**
 603          * Get the maximum allowable file size given backend
 604          * medium restrictions and basic performance constraints.
 605          * Do not call this function from places outside FileBackend and FileOp.
 606          *
 607          * @return integer Bytes
 608          */
 609         final public function maxFileSizeInternal() {
 610                 return $this->maxFileSize;
 611         }
 612
 613         /**
 614          * Check if a file can be created at a given storage path.
 615          * FS backends should check if the parent directory exists and the file is writable.
 616          * Backends using key/value stores should check if the container exists.
 617          *
 618          * @param $storagePath string
 619          * @return bool
 620          */
 621         abstract public function isPathUsableInternal( $storagePath );
 622
 623         /**
 624          * Create a file in the backend with the given contents.
 625          * Do not call this function from places outside FileBackend and FileOp.
 626          *
 627          * $params include:
 628          *     content       : the raw file contents
 629          *     dst           : destination storage path
 630          *     overwrite     : overwrite any file that exists at the destination
 631          *
 632          * @param $params Array
 633          * @return Status
 634          */
 635         final public function createInternal( array $params ) {
 636                 wfProfileIn( __METHOD__ );
 637                 if ( strlen( $params['content'] ) > $this->maxFileSizeInternal() ) {
 638                         $status = Status::newFatal( 'backend-fail-create', $params['dst'] );
 639                 } else {
 640                         $status = $this->doCreateInternal( $params );
 641                         $this->clearCache( array( $params['dst'] ) );
 642                 }
 643                 wfProfileOut( __METHOD__ );
 644                 return $status;
 645         }
 646
 647         /**
 648          * @see FileBackend::createInternal()
 649          */
 650         abstract protected function doCreateInternal( array $params );
 651
 652         /**
 653          * Store a file into the backend from a file on disk.
 654          * Do not call this function from places outside FileBackend and FileOp.
 655          *
 656          * $params include:
 657          *     src           : source path on disk
 658          *     dst           : destination storage path
 659          *     overwrite     : overwrite any file that exists at the destination
 660          *
 661          * @param $params Array
 662          * @return Status
 663          */
 664         final public function storeInternal( array $params ) {
 665                 wfProfileIn( __METHOD__ );
 666                 if ( filesize( $params['src'] ) > $this->maxFileSizeInternal() ) {
 667                         $status = Status::newFatal( 'backend-fail-store', $params['dst'] );
 668                 } else {
 669                         $status = $this->doStoreInternal( $params );
 670                         $this->clearCache( array( $params['dst'] ) );
 671                 }
 672                 wfProfileOut( __METHOD__ );
 673                 return $status;
 674         }
 675
 676         /**
 677          * @see FileBackend::storeInternal()
 678          */
 679         abstract protected function doStoreInternal( array $params );
 680
 681         /**
 682          * Copy a file from one storage path to another in the backend.
 683          * Do not call this function from places outside FileBackend and FileOp.
 684          *
 685          * $params include:
 686          *     src           : source storage path
 687          *     dst           : destination storage path
 688          *     overwrite     : overwrite any file that exists at the destination
 689          *
 690          * @param $params Array
 691          * @return Status
 692          */
 693         final public function copyInternal( array $params ) {
 694                 wfProfileIn( __METHOD__ );
 695                 $status = $this->doCopyInternal( $params );
 696                 $this->clearCache( array( $params['dst'] ) );
 697                 wfProfileOut( __METHOD__ );
 698                 return $status;
 699         }
 700
 701         /**
 702          * @see FileBackend::copyInternal()
 703          */
 704         abstract protected function doCopyInternal( array $params );
 705
 706         /**
 707          * Delete a file at the storage path.
 708          * Do not call this function from places outside FileBackend and FileOp.
 709          *
 710          * $params include:
 711          *     src                 : source storage path
 712          *     ignoreMissingSource : do nothing if the source file does not exist
 713          *
 714          * @param $params Array
 715          * @return Status
 716          */
 717         final public function deleteInternal( array $params ) {
 718                 wfProfileIn( __METHOD__ );
 719                 $status = $this->doDeleteInternal( $params );
 720                 $this->clearCache( array( $params['src'] ) );
 721                 wfProfileOut( __METHOD__ );
 722                 return $status;
 723         }
 724
 725         /**
 726          * @see FileBackend::deleteInternal()
 727          */
 728         abstract protected function doDeleteInternal( array $params );
 729
 730         /**
 731          * Move a file from one storage path to another in the backend.
 732          * Do not call this function from places outside FileBackend and FileOp.
 733          *
 734          * $params include:
 735          *     src           : source storage path
 736          *     dst           : destination storage path
 737          *     overwrite     : overwrite any file that exists at the destination
 738          *
 739          * @param $params Array
 740          * @return Status
 741          */
 742         final public function moveInternal( array $params ) {
 743                 wfProfileIn( __METHOD__ );
 744                 $status = $this->doMoveInternal( $params );
 745                 $this->clearCache( array( $params['src'], $params['dst'] ) );
 746                 wfProfileOut( __METHOD__ );
 747                 return $status;
 748         }
 749
 750         /**
 751          * @see FileBackend::moveInternal()
 752          */
 753         protected function doMoveInternal( array $params ) {
 754                 // Copy source to dest
 755                 $status = $this->copyInternal( $params );
 756                 if ( $status->isOK() ) {
 757                         // Delete source (only fails due to races or medium going down)
 758                         $status->merge( $this->deleteInternal( array( 'src' => $params['src'] ) ) );
 759                         $status->setResult( true, $status->value ); // ignore delete() errors
 760                 }
 761                 return $status;
 762         }
 763
 764         /**
 765          * @see FileBackendBase::concatenate()
 766          */
 767         final public function concatenate( array $params ) {
 768                 wfProfileIn( __METHOD__ );
 769                 $status = Status::newGood();
 770
 771                 // Try to lock the source files for the scope of this function
 772                 $scopeLockS = $this->getScopedFileLocks( $params['srcs'], LockManager::LOCK_UW, $status );
 773                 if ( $status->isOK() ) {
 774                         // Actually do the concatenation
 775                         $status->merge( $this->doConcatenate( $params ) );
 776                 }
 777
 778                 wfProfileOut( __METHOD__ );
 779                 return $status;
 780         }
 781
 782         /**
 783          * @see FileBackend::concatenate()
 784          */
 785         protected function doConcatenate( array $params ) {
 786                 $status = Status::newGood();
 787                 $tmpPath = $params['dst']; // convenience
 788
 789                 // Check that the specified temp file is valid...
 790                 wfSuppressWarnings();
 791                 $ok = ( is_file( $tmpPath ) && !filesize( $tmpPath ) );
 792                 wfRestoreWarnings();
 793                 if ( !$ok ) { // not present or not empty
 794                         $status->fatal( 'backend-fail-opentemp', $tmpPath );
 795                         return $status;
 796                 }
 797
 798                 // Build up the temp file using the source chunks (in order)...
 799                 $tmpHandle = fopen( $tmpPath, 'a' );
 800                 if ( $tmpHandle === false ) {
 801                         $status->fatal( 'backend-fail-opentemp', $tmpPath );
 802                         return $status;
 803                 }
 804                 foreach ( $params['srcs'] as $virtualSource ) {
 805                         // Get a local FS version of the chunk
 806                         $tmpFile = $this->getLocalReference( array( 'src' => $virtualSource ) );
 807                         if ( !$tmpFile ) {
 808                                 $status->fatal( 'backend-fail-read', $virtualSource );
 809                                 return $status;
 810                         }
 811                         // Get a handle to the local FS version
 812                         $sourceHandle = fopen( $tmpFile->getPath(), 'r' );
 813                         if ( $sourceHandle === false ) {
 814                                 fclose( $tmpHandle );
 815                                 $status->fatal( 'backend-fail-read', $virtualSource );
 816                                 return $status;
 817                         }
 818                         // Append chunk to file (pass chunk size to avoid magic quotes)
 819                         if ( !stream_copy_to_stream( $sourceHandle, $tmpHandle ) ) {
 820                                 fclose( $sourceHandle );
 821                                 fclose( $tmpHandle );
 822                                 $status->fatal( 'backend-fail-writetemp', $tmpPath );
 823                                 return $status;
 824                         }
 825                         fclose( $sourceHandle );
 826                 }
 827                 if ( !fclose( $tmpHandle ) ) {
 828                         $status->fatal( 'backend-fail-closetemp', $tmpPath );
 829                         return $status;
 830                 }
 831
 832                 clearstatcache(); // temp file changed
 833
 834                 return $status;
 835         }
 836
 837         /**
 838          * @see FileBackendBase::doPrepare()
 839          */
 840         final protected function doPrepare( array $params ) {
 841                 wfProfileIn( __METHOD__ );
 842
 843                 $status = Status::newGood();
 844                 list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
 845                 if ( $dir === null ) {
 846                         $status->fatal( 'backend-fail-invalidpath', $params['dir'] );
 847                         wfProfileOut( __METHOD__ );
 848                         return $status; // invalid storage path
 849                 }
 850
 851                 if ( $shard !== null ) { // confined to a single container/shard
 852                         $status->merge( $this->doPrepareInternal( $fullCont, $dir, $params ) );
 853                 } else { // directory is on several shards
 854                         wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
 855                         list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
 856                         foreach ( $this->getContainerSuffixes( $shortCont ) as $suffix ) {
 857                                 $status->merge( $this->doPrepareInternal( "{$fullCont}{$suffix}", $dir, $params ) );
 858                         }
 859                 }
 860
 861                 wfProfileOut( __METHOD__ );
 862                 return $status;
 863         }
 864
 865         /**
 866          * @see FileBackend::doPrepare()
 867          */
 868         protected function doPrepareInternal( $container, $dir, array $params ) {
 869                 return Status::newGood();
 870         }
 871
 872         /**
 873          * @see FileBackendBase::doSecure()
 874          */
 875         final protected function doSecure( array $params ) {
 876                 wfProfileIn( __METHOD__ );
 877                 $status = Status::newGood();
 878
 879                 list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
 880                 if ( $dir === null ) {
 881                         $status->fatal( 'backend-fail-invalidpath', $params['dir'] );
 882                         wfProfileOut( __METHOD__ );
 883                         return $status; // invalid storage path
 884                 }
 885
 886                 if ( $shard !== null ) { // confined to a single container/shard
 887                         $status->merge( $this->doSecureInternal( $fullCont, $dir, $params ) );
 888                 } else { // directory is on several shards
 889                         wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
 890                         list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
 891                         foreach ( $this->getContainerSuffixes( $shortCont ) as $suffix ) {
 892                                 $status->merge( $this->doSecureInternal( "{$fullCont}{$suffix}", $dir, $params ) );
 893                         }
 894                 }
 895
 896                 wfProfileOut( __METHOD__ );
 897                 return $status;
 898         }
 899
 900         /**
 901          * @see FileBackend::doSecure()
 902          */
 903         protected function doSecureInternal( $container, $dir, array $params ) {
 904                 return Status::newGood();
 905         }
 906
 907         /**
 908          * @see FileBackendBase::doClean()
 909          */
 910         final protected function doClean( array $params ) {
 911                 wfProfileIn( __METHOD__ );
 912                 $status = Status::newGood();
 913
 914                 list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
 915                 if ( $dir === null ) {
 916                         $status->fatal( 'backend-fail-invalidpath', $params['dir'] );
 917                         wfProfileOut( __METHOD__ );
 918                         return $status; // invalid storage path
 919                 }
 920
 921                 // Attempt to lock this directory...
 922                 $filesLockEx = array( $params['dir'] );
 923                 $scopedLockE = $this->getScopedFileLocks( $filesLockEx, LockManager::LOCK_EX, $status );
 924                 if ( !$status->isOK() ) {
 925                         wfProfileOut( __METHOD__ );
 926                         return $status; // abort
 927                 }
 928
 929                 if ( $shard !== null ) { // confined to a single container/shard
 930                         $status->merge( $this->doCleanInternal( $fullCont, $dir, $params ) );
 931                 } else { // directory is on several shards
 932                         wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
 933                         list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
 934                         foreach ( $this->getContainerSuffixes( $shortCont ) as $suffix ) {
 935                                 $status->merge( $this->doCleanInternal( "{$fullCont}{$suffix}", $dir, $params ) );
 936                         }
 937                 }
 938
 939                 wfProfileOut( __METHOD__ );
 940                 return $status;
 941         }
 942
 943         /**
 944          * @see FileBackend::doClean()
 945          */
 946         protected function doCleanInternal( $container, $dir, array $params ) {
 947                 return Status::newGood();
 948         }
 949
 950         /**
 951          * @see FileBackendBase::fileExists()
 952          */
 953         final public function fileExists( array $params ) {
 954                 wfProfileIn( __METHOD__ );
 955                 $stat = $this->getFileStat( $params );
 956                 wfProfileOut( __METHOD__ );
 957                 return ( $stat === null ) ? null : (bool)$stat; // null => failure
 958         }
 959
 960         /**
 961          * @see FileBackendBase::getFileTimestamp()
 962          */
 963         final public function getFileTimestamp( array $params ) {
 964                 wfProfileIn( __METHOD__ );
 965                 $stat = $this->getFileStat( $params );
 966                 wfProfileOut( __METHOD__ );
 967                 return $stat ? $stat['mtime'] : false;
 968         }
 969
 970         /**
 971          * @see FileBackendBase::getFileSize()
 972          */
 973         final public function getFileSize( array $params ) {
 974                 wfProfileIn( __METHOD__ );
 975                 $stat = $this->getFileStat( $params );
 976                 wfProfileOut( __METHOD__ );
 977                 return $stat ? $stat['size'] : false;
 978         }
 979
 980         /**
 981          * @see FileBackendBase::getFileStat()
 982          */
 983         final public function getFileStat( array $params ) {
 984                 wfProfileIn( __METHOD__ );
 985                 $path = $params['src'];
 986                 $latest = !empty( $params['latest'] );
 987                 if ( isset( $this->cache[$path]['stat'] ) ) {
 988                         // If we want the latest data, check that this cached
 989                         // value was in fact fetched with the latest available data.
 990                         if ( !$latest || $this->cache[$path]['stat']['latest'] ) {
 991                                 wfProfileOut( __METHOD__ );
 992                                 return $this->cache[$path]['stat'];
 993                         }
 994                 }
 995                 $stat = $this->doGetFileStat( $params );
 996                 if ( is_array( $stat ) ) { // don't cache negatives
 997                         $this->trimCache(); // limit memory
 998                         $this->cache[$path]['stat'] = $stat;
 999                         $this->cache[$path]['stat']['latest'] = $latest;
1000                 }
1001                 wfProfileOut( __METHOD__ );
1002                 return $stat;
1003         }
1004
1005         /**
1006          * @see FileBackend::getFileStat()
1007          */
1008         abstract protected function doGetFileStat( array $params );
1009
1010         /**
1011          * @see FileBackendBase::getFileContents()
1012          */
1013         public function getFileContents( array $params ) {
1014                 wfProfileIn( __METHOD__ );
1015                 $tmpFile = $this->getLocalReference( $params );
1016                 if ( !$tmpFile ) {
1017                         wfProfileOut( __METHOD__ );
1018                         return false;
1019                 }
1020                 wfSuppressWarnings();
1021                 $data = file_get_contents( $tmpFile->getPath() );
1022                 wfRestoreWarnings();
1023                 wfProfileOut( __METHOD__ );
1024                 return $data;
1025         }
1026
1027         /**
1028          * @see FileBackendBase::getFileSha1Base36()
1029          */
1030         final public function getFileSha1Base36( array $params ) {
1031                 wfProfileIn( __METHOD__ );
1032                 $path = $params['src'];
1033                 if ( isset( $this->cache[$path]['sha1'] ) ) {
1034                         wfProfileOut( __METHOD__ );
1035                         return $this->cache[$path]['sha1'];
1036                 }
1037                 $hash = $this->doGetFileSha1Base36( $params );
1038                 if ( $hash ) { // don't cache negatives
1039                         $this->trimCache(); // limit memory
1040                         $this->cache[$path]['sha1'] = $hash;
1041                 }
1042                 wfProfileOut( __METHOD__ );
1043                 return $hash;
1044         }
1045
1046         /**
1047          * @see FileBackend::getFileSha1Base36()
1048          */
1049         protected function doGetFileSha1Base36( array $params ) {
1050                 $fsFile = $this->getLocalReference( $params );
1051                 if ( !$fsFile ) {
1052                         return false;
1053                 } else {
1054                         return $fsFile->getSha1Base36();
1055                 }
1056         }
1057
1058         /**
1059          * @see FileBackendBase::getFileProps()
1060          */
1061         final public function getFileProps( array $params ) {
1062                 wfProfileIn( __METHOD__ );
1063                 $fsFile = $this->getLocalReference( $params );
1064                 $props = $fsFile ? $fsFile->getProps() : FSFile::placeholderProps();
1065                 wfProfileOut( __METHOD__ );
1066                 return $props;
1067         }
1068
1069         /**
1070          * @see FileBackendBase::getLocalReference()
1071          */
1072         public function getLocalReference( array $params ) {
1073                 wfProfileIn( __METHOD__ );
1074                 $path = $params['src'];
1075                 if ( isset( $this->cache[$path]['localRef'] ) ) {
1076                         wfProfileOut( __METHOD__ );
1077                         return $this->cache[$path]['localRef'];
1078                 }
1079                 $tmpFile = $this->getLocalCopy( $params );
1080                 if ( $tmpFile ) { // don't cache negatives
1081                         $this->trimCache(); // limit memory
1082                         $this->cache[$path]['localRef'] = $tmpFile;
1083                 }
1084                 wfProfileOut( __METHOD__ );
1085                 return $tmpFile;
1086         }
1087
1088         /**
1089          * @see FileBackendBase::streamFile()
1090          */
1091         final public function streamFile( array $params ) {
1092                 wfProfileIn( __METHOD__ );
1093                 $status = Status::newGood();
1094
1095                 $info = $this->getFileStat( $params );
1096                 if ( !$info ) { // let StreamFile handle the 404
1097                         $status->fatal( 'backend-fail-notexists', $params['src'] );
1098                 }
1099
1100                 // Set output buffer and HTTP headers for stream
1101                 $extraHeaders = $params['headers'] ? $params['headers'] : array();
1102                 $res = StreamFile::prepareForStream( $params['src'], $info, $extraHeaders );
1103                 if ( $res == StreamFile::NOT_MODIFIED ) {
1104                         // do nothing; client cache is up to date
1105                 } elseif ( $res == StreamFile::READY_STREAM ) {
1106                         $status = $this->doStreamFile( $params );
1107                 } else {
1108                         $status->fatal( 'backend-fail-stream', $params['src'] );
1109                 }
1110
1111                 wfProfileOut( __METHOD__ );
1112                 return $status;
1113         }
1114
1115         /**
1116          * @see FileBackend::streamFile()
1117          */
1118         protected function doStreamFile( array $params ) {
1119                 $status = Status::newGood();
1120
1121                 $fsFile = $this->getLocalReference( $params );
1122                 if ( !$fsFile ) {
1123                         $status->fatal( 'backend-fail-stream', $params['src'] );
1124                 } elseif ( !readfile( $fsFile->getPath() ) ) {
1125                         $status->fatal( 'backend-fail-stream', $params['src'] );
1126                 }
1127
1128                 return $status;
1129         }
1130
1131         /**
1132          * @see FileBackendBase::getFileList()
1133          */
1134         final public function getFileList( array $params ) {
1135                 list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
1136                 if ( $dir === null ) { // invalid storage path
1137                         return null;
1138                 }
1139                 if ( $shard !== null ) {
1140                         // File listing is confined to a single container/shard
1141                         return $this->getFileListInternal( $fullCont, $dir, $params );
1142                 } else {
1143                         wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
1144                         // File listing spans multiple containers/shards
1145                         list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
1146                         return new FileBackendShardListIterator( $this,
1147                                 $fullCont, $this->getContainerSuffixes( $shortCont ), $params );
1148                 }
1149         }
1150
1151         /**
1152          * Do not call this function from places outside FileBackend and ContainerFileListIterator
1153          *
1154          * @param $container string Resolved container name
1155          * @param $dir string Resolved path relative to container
1156          * @param $params Array
1157          * @see FileBackend::getFileList()
1158          */
1159         abstract public function getFileListInternal( $container, $dir, array $params );
1160
1161         /**
1162          * Get the list of supported operations and their corresponding FileOp classes.
1163          *
1164          * @return Array
1165          */
1166         protected function supportedOperations() {
1167                 return array(
1168                         'store'       => 'StoreFileOp',
1169                         'copy'        => 'CopyFileOp',
1170                         'move'        => 'MoveFileOp',
1171                         'delete'      => 'DeleteFileOp',
1172                         'create'      => 'CreateFileOp',
1173                         'null'        => 'NullFileOp'
1174                 );
1175         }
1176
1177         /**
1178          * Return a list of FileOp objects from a list of operations.
1179          * Do not call this function from places outside FileBackend.
1180          *
1181          * The result must have the same number of items as the input.
1182          * An exception is thrown if an unsupported operation is requested.
1183          *
1184          * @param $ops Array Same format as doOperations()
1185          * @return Array List of FileOp objects
1186          * @throws MWException
1187          */
1188         final public function getOperations( array $ops ) {
1189                 $supportedOps = $this->supportedOperations();
1190
1191                 $performOps = array(); // array of FileOp objects
1192                 // Build up ordered array of FileOps...
1193                 foreach ( $ops as $operation ) {
1194                         $opName = $operation['op'];
1195                         if ( isset( $supportedOps[$opName] ) ) {
1196                                 $class = $supportedOps[$opName];
1197                                 // Get params for this operation
1198                                 $params = $operation;
1199                                 // Append the FileOp class
1200                                 $performOps[] = new $class( $this, $params );
1201                         } else {
1202                                 throw new MWException( "Operation `$opName` is not supported." );
1203                         }
1204                 }
1205
1206                 return $performOps;
1207         }
1208
1209         /**
1210          * @see FileBackendBase::doOperationsInternal()
1211          */
1212         protected function doOperationsInternal( array $ops, array $opts ) {
1213                 wfProfileIn( __METHOD__ );
1214                 $status = Status::newGood();
1215
1216                 // Build up a list of FileOps...
1217                 $performOps = $this->getOperations( $ops );
1218
1219                 // Acquire any locks as needed...
1220                 if ( empty( $opts['nonLocking'] ) ) {
1221                         // Build up a list of files to lock...
1222                         $filesLockEx = $filesLockSh = array();
1223                         foreach ( $performOps as $fileOp ) {
1224                                 $filesLockSh = array_merge( $filesLockSh, $fileOp->storagePathsRead() );
1225                                 $filesLockEx = array_merge( $filesLockEx, $fileOp->storagePathsChanged() );
1226                         }
1227                         // Optimization: if doing an EX lock anyway, don't also set an SH one
1228                         $filesLockSh = array_diff( $filesLockSh, $filesLockEx );
1229                         // Get a shared lock on the parent directory of each path changed
1230                         $filesLockSh = array_merge( $filesLockSh, array_map( 'dirname', $filesLockEx ) );
1231                         // Try to lock those files for the scope of this function...
1232                         $scopeLockS = $this->getScopedFileLocks( $filesLockSh, LockManager::LOCK_UW, $status );
1233                         $scopeLockE = $this->getScopedFileLocks( $filesLockEx, LockManager::LOCK_EX, $status );
1234                         if ( !$status->isOK() ) {
1235                                 wfProfileOut( __METHOD__ );
1236                                 return $status; // abort
1237                         }
1238                 }
1239
1240                 // Clear any cache entries (after locks acquired)
1241                 $this->clearCache();
1242
1243                 // Actually attempt the operation batch...
1244                 $subStatus = FileOp::attemptBatch( $performOps, $opts );
1245
1246                 // Merge errors into status fields
1247                 $status->merge( $subStatus );
1248                 $status->success = $subStatus->success; // not done in merge()
1249
1250                 wfProfileOut( __METHOD__ );
1251                 return $status;
1252         }
1253
1254         /**
1255          * @see FileBackendBase::clearCache()
1256          */
1257         final public function clearCache( array $paths = null ) {
1258                 if ( $paths === null ) {
1259                         $this->cache = array();
1260                 } else {
1261                         foreach ( $paths as $path ) {
1262                                 unset( $this->cache[$path] );
1263                         }
1264                 }
1265                 $this->doClearCache( $paths );
1266         }
1267
1268         /**
1269          * Clears any additional stat caches for storage paths
1270          *
1271          * @see FileBackendBase::clearCache()
1272          *
1273          * @param $paths Array Storage paths (optional)
1274          * @return void
1275          */
1276         protected function doClearCache( array $paths = null ) {}
1277
1278         /**
1279          * Prune the cache if it is too big to add an item
1280          *
1281          * @return void
1282          */
1283         protected function trimCache() {
1284                 if ( count( $this->cache ) >= $this->maxCacheSize ) {
1285                         reset( $this->cache );
1286                         $key = key( $this->cache );
1287                         unset( $this->cache[$key] );
1288                 }
1289         }
1290
1291         /**
1292          * Get the parent storage directory of a storage path.
1293          * This returns a path like "mwstore://backend/container",
1294          * "mwstore://backend/container/...", or null if there is no parent.
1295          *
1296          * @param $storagePath string
1297          * @return string|null
1298          */
1299         final public static function parentStoragePath( $storagePath ) {
1300                 $storagePath = dirname( $storagePath );
1301                 list( $b, $cont, $rel ) = self::splitStoragePath( $storagePath );
1302                 return ( $rel === null ) ? null : $storagePath;
1303         }
1304
1305         /**
1306          * Check if a given path is a mwstore:// path.
1307          * This does not do any actual validation or existence checks.
1308          *
1309          * @param $path string
1310          * @return bool
1311          */
1312         final public static function isStoragePath( $path ) {
1313                 return ( strpos( $path, 'mwstore://' ) === 0 );
1314         }
1315
1316         /**
1317          * Split a storage path (e.g. "mwstore://backend/container/path/to/object")
1318          * into a backend name, a container name, and a relative object path.
1319          *
1320          * @param $storagePath string
1321          * @return Array (backend, container, rel object) or (null, null, null)
1322          */
1323         final public static function splitStoragePath( $storagePath ) {
1324                 if ( self::isStoragePath( $storagePath ) ) {
1325                         // Note: strlen( 'mwstore://' ) = 10
1326                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
1327                         if ( count( $parts ) == 3 ) {
1328                                 return $parts; // e.g. "backend/container/path"
1329                         } elseif ( count( $parts ) == 2 ) {
1330                                 return array( $parts[0], $parts[1], '' ); // e.g. "backend/container"
1331                         }
1332                 }
1333                 return array( null, null, null );
1334         }
1335
1336         /**
1337          * Check if a container name is valid.
1338          * This checks for for length and illegal characters.
1339          *
1340          * @param $container string
1341          * @return bool
1342          */
1343         final protected static function isValidContainerName( $container ) {
1344                 // This accounts for Swift and S3 restrictions while leaving room
1345                 // for things like '.xxx' (hex shard chars) or '.seg' (segments).
1346                 // Note that matching strings URL encode to the same string;
1347                 // in Swift, the length restriction is *after* URL encoding.
1348                 return preg_match( '/^[a-z0-9][a-z0-9-_]{0,199}$/i', $container );
1349         }
1350
1351         /**
1352          * Validate and normalize a relative storage path.
1353          * Null is returned if the path involves directory traversal.
1354          * Traversal is insecure for FS backends and broken for others.
1355          *
1356          * @param $path string Storage path relative to a container
1357          * @return string|null
1358          */
1359         final protected static function normalizeContainerPath( $path ) {
1360                 // Normalize directory separators
1361                 $path = strtr( $path, '\\', '/' );
1362                 // Collapse consecutive directory separators
1363                 $path = preg_replace( '![/]{2,}!', '/', $path );
1364                 // Use the same traversal protection as Title::secureAndSplit()
1365                 if ( strpos( $path, '.' ) !== false ) {
1366                         if (
1367                                 $path === '.' ||
1368                                 $path === '..' ||
1369                                 strpos( $path, './' ) === 0 ||
1370                                 strpos( $path, '../' ) === 0 ||
1371                                 strpos( $path, '/./' ) !== false ||
1372                                 strpos( $path, '/../' ) !== false
1373                         ) {
1374                                 return null;
1375                         }
1376                 }
1377                 return $path;
1378         }
1379
1380         /**
1381          * Splits a storage path into an internal container name,
1382          * an internal relative file name, and a container shard suffix.
1383          * Any shard suffix is already appended to the internal container name.
1384          * This also checks that the storage path is valid and within this backend.
1385          *
1386          * If the container is sharded but a suffix could not be determined,
1387          * this means that the path can only refer to a directory and can only
1388          * be scanned by looking in all the container shards.
1389          *
1390          * @param $storagePath string
1391          * @return Array (container, path, container suffix) or (null, null, null) if invalid
1392          */
1393         final protected function resolveStoragePath( $storagePath ) {
1394                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
1395                 if ( $backend === $this->name ) { // must be for this backend
1396                         $relPath = self::normalizeContainerPath( $relPath );
1397                         if ( $relPath !== null ) {
1398                                 // Get shard for the normalized path if this container is sharded
1399                                 $cShard = $this->getContainerShard( $container, $relPath );
1400                                 // Validate and sanitize the relative path (backend-specific)
1401                                 $relPath = $this->resolveContainerPath( $container, $relPath );
1402                                 if ( $relPath !== null ) {
1403                                         // Prepend any wiki ID prefix to the container name
1404                                         $container = $this->fullContainerName( $container );
1405                                         if ( self::isValidContainerName( $container ) ) {
1406                                                 // Validate and sanitize the container name (backend-specific)
1407                                                 $container = $this->resolveContainerName( "{$container}{$cShard}" );
1408                                                 if ( $container !== null ) {
1409                                                         return array( $container, $relPath, $cShard );
1410                                                 }
1411                                         }
1412                                 }
1413                         }
1414                 }
1415                 return array( null, null, null );
1416         }
1417
1418         /**
1419          * Like resolveStoragePath() except null values are returned if
1420          * the container is sharded and the shard could not be determined.
1421          *
1422          * @see FileBackend::resolveStoragePath()
1423          *
1424          * @param $storagePath string
1425          * @return Array (container, path) or (null, null) if invalid
1426          */
1427         final protected function resolveStoragePathReal( $storagePath ) {
1428                 list( $container, $relPath, $cShard ) = $this->resolveStoragePath( $storagePath );
1429                 if ( $cShard !== null ) {
1430                         return array( $container, $relPath );
1431                 }
1432                 return array( null, null );
1433         }
1434
1435         /**
1436          * Get the container name shard suffix for a given path.
1437          * Any empty suffix means the container is not sharded.
1438          *
1439          * @param $container string Container name
1440          * @param $relStoragePath string Storage path relative to the container
1441          * @return string|null Returns null if shard could not be determined
1442          */
1443         final protected function getContainerShard( $container, $relPath ) {
1444                 $hashLevels = $this->getContainerHashLevels( $container );
1445                 if ( $hashLevels === 1 ) { // 16 shards per container
1446                         $hashDirRegex = '(?P<shard>[0-9a-f])';
1447                 } elseif ( $hashLevels === 2 ) { // 256 shards per container
1448                         $hashDirRegex = '[0-9a-f]/(?P<shard>[0-9a-f]{2})';
1449                 } else {
1450                         return ''; // no sharding
1451                 }
1452                 // Allow certain directories to be above the hash dirs so as
1453                 // to work with FileRepo (e.g. "archive/a/ab" or "temp/a/ab").
1454                 // They must be 2+ chars to avoid any hash directory ambiguity.
1455                 if ( preg_match( "!^(?:[^/]{2,}/)*$hashDirRegex(?:/|$)!", $relPath, $m ) ) {
1456                         return '.' . str_pad( $m['shard'], $hashLevels, '0', STR_PAD_LEFT );
1457                 }
1458                 return null; // failed to match
1459         }
1460
1461         /**
1462          * Get the number of hash levels for a container.
1463          * If greater than 0, then all file storage paths within
1464          * the container are required to be hashed accordingly.
1465          *
1466          * @param $container string
1467          * @return integer
1468          */
1469         final protected function getContainerHashLevels( $container ) {
1470                 if ( isset( $this->shardViaHashLevels[$container] ) ) {
1471                         $hashLevels = (int)$this->shardViaHashLevels[$container];
1472                         if ( $hashLevels >= 0 && $hashLevels <= 2 ) {
1473                                 return $hashLevels;
1474                         }
1475                 }
1476                 return 0; // no sharding
1477         }
1478
1479         /**
1480          * Get a list of full container shard suffixes for a container
1481          *
1482          * @param $container string
1483          * @return Array
1484          */
1485         final protected function getContainerSuffixes( $container ) {
1486                 $shards = array();
1487                 $digits = $this->getContainerHashLevels( $container );
1488                 if ( $digits > 0 ) {
1489                         $numShards = 1 << ( $digits * 4 );
1490                         for ( $index = 0; $index < $numShards; $index++ ) {
1491                                 $shards[] = '.' . str_pad( dechex( $index ), $digits, '0', STR_PAD_LEFT );
1492                         }
1493                 }
1494                 return $shards;
1495         }
1496
1497         /**
1498          * Get the full container name, including the wiki ID prefix
1499          *
1500          * @param $container string
1501          * @return string
1502          */
1503         final protected function fullContainerName( $container ) {
1504                 if ( $this->wikiId != '' ) {
1505                         return "{$this->wikiId}-$container";
1506                 } else {
1507                         return $container;
1508                 }
1509         }
1510
1511         /**
1512          * Resolve a container name, checking if it's allowed by the backend.
1513          * This is intended for internal use, such as encoding illegal chars.
1514          * Subclasses can override this to be more restrictive.
1515          *
1516          * @param $container string
1517          * @return string|null
1518          */
1519         protected function resolveContainerName( $container ) {
1520                 return $container;
1521         }
1522
1523         /**
1524          * Resolve a relative storage path, checking if it's allowed by the backend.
1525          * This is intended for internal use, such as encoding illegal chars or perhaps
1526          * getting absolute paths (e.g. FS based backends). Note that the relative path
1527          * may be the empty string (e.g. the path is simply to the container).
1528          *
1529          * @param $container string Container name
1530          * @param $relStoragePath string Storage path relative to the container
1531          * @return string|null Path or null if not valid
1532          */
1533         protected function resolveContainerPath( $container, $relStoragePath ) {
1534                 return $relStoragePath;
1535         }
1536
1537         /**
1538          * Get the final extension from a storage or FS path
1539          *
1540          * @param $path string
1541          * @return string
1542          */
1543         final public static function extensionFromPath( $path ) {
1544                 $i = strrpos( $path, '.' );
1545                 return strtolower( $i ? substr( $path, $i + 1 ) : '' );
1546         }
1547 }
1548
1549 /**
1550  * FileBackend helper function to handle file listings that span container shards.
1551  * Do not use this class from places outside of FileBackend.
1552  *
1553  * @ingroup FileBackend
1554  */
1555 class FileBackendShardListIterator implements Iterator {
1556         /* @var FileBackend */
1557         protected $backend;
1558         /* @var Array */
1559         protected $params;
1560         /* @var Array */
1561         protected $shardSuffixes;
1562         protected $container; // string
1563         protected $directory; // string
1564
1565         /* @var Traversable */
1566         protected $iter;
1567         protected $curShard = 0; // integer
1568         protected $pos = 0; // integer
1569
1570         /**
1571          * @param $backend FileBackend
1572          * @param $container string Full storage container name
1573          * @param $dir string Storage directory relative to container
1574          * @param $suffixes Array List of container shard suffixes
1575          * @param $params Array
1576          */
1577         public function __construct(
1578                 FileBackend $backend, $container, $dir, array $suffixes, array $params
1579         ) {
1580                 $this->backend = $backend;
1581                 $this->container = $container;
1582                 $this->directory = $dir;
1583                 $this->shardSuffixes = $suffixes;
1584                 $this->params = $params;
1585         }
1586
1587         public function current() {
1588                 if ( is_array( $this->iter ) ) {
1589                         return current( $this->iter );
1590                 } else {
1591                         return $this->iter->current();
1592                 }
1593         }
1594
1595         public function key() {
1596                 return $this->pos;
1597         }
1598
1599         public function next() {
1600                 ++$this->pos;
1601                 if ( is_array( $this->iter ) ) {
1602                         next( $this->iter );
1603                 } else {
1604                         $this->iter->next();
1605                 }
1606                 // Find the next non-empty shard if no elements are left
1607                 $this->nextShardIteratorIfNotValid();
1608         }
1609
1610         /**
1611          * If the iterator for this container shard is out of items,
1612          * then move on to the next container that has items.
1613          * If there are none, then it advances to the last container.
1614          */
1615         protected function nextShardIteratorIfNotValid() {
1616                 while ( !$this->valid() ) {
1617                         if ( ++$this->curShard >= count( $this->shardSuffixes ) ) {
1618                                 break; // no more container shards
1619                         }
1620                         $this->setIteratorFromCurrentShard();
1621                 }
1622         }
1623
1624         protected function setIteratorFromCurrentShard() {
1625                 $suffix = $this->shardSuffixes[$this->curShard];
1626                 $this->iter = $this->backend->getFileListInternal(
1627                         "{$this->container}{$suffix}", $this->directory, $this->params );
1628         }
1629
1630         public function rewind() {
1631                 $this->pos = 0;
1632                 $this->curShard = 0;
1633                 $this->setIteratorFromCurrentShard();
1634                 // Find the next non-empty shard if this one has no elements
1635                 $this->nextShardIteratorIfNotValid();
1636         }
1637
1638         public function valid() {
1639                 if ( $this->iter == null ) {
1640                         return false; // some failure?
1641                 } elseif ( is_array( $this->iter ) ) {
1642                         return ( current( $this->iter ) !== false ); // no paths can have this value
1643                 } else {
1644                         return $this->iter->valid();
1645                 }
1646         }
1647 }