includes/filerepo/backend/FileBackend.php

   1 <?php
   2 /**
   3  * @defgroup FileBackend File backend
   4  * @ingroup  FileRepo
   5  *
   6  * File backend is used to interact with file storage systems,
   7  * such as the local file system, NFS, or cloud storage systems.
   8  */
   9
  10 /**
  11  * @file
  12  * @ingroup FileBackend
  13  * @author Aaron Schulz
  14  */
  15
  16 /**
  17  * @brief Base class for all file backend classes (including multi-write backends).
  18  *
  19  * This class defines the methods as abstract that subclasses must implement.
  20  * Outside callers can assume that all backends will have these functions.
  21  *
  22  * All "storage paths" are of the format "mwstore://<backend>/<container>/<path>".
  23  * The <path> portion is a relative path that uses UNIX file system (FS) notation,
  24  * though any particular backend may not actually be using a local filesystem.
  25  * Therefore, the relative paths are only virtual.
  26  *
  27  * Backend contents are stored under wiki-specific container names by default.
  28  * For legacy reasons, this has no effect for the FS backend class, and per-wiki
  29  * segregation must be done by setting the container paths appropriately.
  30  *
  31  * FS-based backends are somewhat more restrictive due to the existence of real
  32  * directory files; a regular file cannot have the same name as a directory. Other
  33  * backends with virtual directories may not have this limitation. Callers should
  34  * store files in such a way that no files and directories are under the same path.
  35  *
  36  * Methods should avoid throwing exceptions at all costs.
  37  * As a corollary, external dependencies should be kept to a minimum.
  38  *
  39  * @ingroup FileBackend
  40  * @since 1.19
  41  */
  42 abstract class FileBackend {
  43         protected $name; // string; unique backend name
  44         protected $wikiId; // string; unique wiki name
  45         protected $readOnly; // string; read-only explanation message
  46         /** @var LockManager */
  47         protected $lockManager;
  48         /** @var FileJournal */
  49         protected $fileJournal;
  50
  51         /**
  52          * Create a new backend instance from configuration.
  53          * This should only be called from within FileBackendGroup.
  54          *
  55          * $config includes:
  56          *     'name'        : The unique name of this backend.
  57          *                     This should consist of alphanumberic, '-', and '_' characters.
  58          *                     This name should not be changed after use.
  59          *     'wikiId'      : Prefix to container names that is unique to this wiki.
  60          *                     This should consist of alphanumberic, '-', and '_' characters.
  61          *     'lockManager' : Registered name of a file lock manager to use.
  62          *     'readOnly'    : Write operations are disallowed if this is a non-empty string.
  63          *                     It should be an explanation for the backend being read-only.
  64          *
  65          * @param $config Array
  66          */
  67         public function __construct( array $config ) {
  68                 $this->name = $config['name'];
  69                 if ( !preg_match( '!^[a-zA-Z0-9-_]{1,255}$!', $this->name ) ) {
  70                         throw new MWException( "Backend name `{$this->name}` is invalid." );
  71                 }
  72                 $this->wikiId = isset( $config['wikiId'] )
  73                         ? $config['wikiId']
  74                         : wfWikiID(); // e.g. "my_wiki-en_"
  75                 $this->lockManager = ( $config['lockManager'] instanceof LockManager )
  76                         ? $config['lockManager']
  77                         : LockManagerGroup::singleton()->get( $config['lockManager'] );
  78                 $this->fileJournal = isset( $config['fileJournal'] )
  79                         ? FileJournal::factory( $config['fileJournal'], $this->name )
  80                         : FileJournal::factory( array( 'class' => 'NullFileJournal' ), $this->name );
  81                 $this->readOnly = isset( $config['readOnly'] )
  82                         ? (string)$config['readOnly']
  83                         : '';
  84         }
  85
  86         /**
  87          * Get the unique backend name.
  88          * We may have multiple different backends of the same type.
  89          * For example, we can have two Swift backends using different proxies.
  90          *
  91          * @return string
  92          */
  93         final public function getName() {
  94                 return $this->name;
  95         }
  96
  97         /**
  98          * Check if this backend is read-only
  99          *
 100          * @return bool
 101          */
 102         final public function isReadOnly() {
 103                 return ( $this->readOnly != '' );
 104         }
 105
 106         /**
 107          * Get an explanatory message if this backend is read-only
 108          *
 109          * @return string|bool Returns falls if the backend is not read-only
 110          */
 111         final public function getReadOnlyReason() {
 112                 return ( $this->readOnly != '' ) ? $this->readOnly : false;
 113         }
 114
 115         /**
 116          * This is the main entry point into the backend for write operations.
 117          * Callers supply an ordered list of operations to perform as a transaction.
 118          * Files will be locked, the stat cache cleared, and then the operations attempted.
 119          * If any serious errors occur, all attempted operations will be rolled back.
 120          *
 121          * $ops is an array of arrays. The outer array holds a list of operations.
 122          * Each inner array is a set of key value pairs that specify an operation.
 123          *
 124          * Supported operations and their parameters:
 125          * a) Create a new file in storage with the contents of a string
 126          *     array(
 127          *         'op'                  => 'create',
 128          *         'dst'                 => <storage path>,
 129          *         'content'             => <string of new file contents>,
 130          *         'overwrite'           => <boolean>,
 131          *         'overwriteSame'       => <boolean>
 132          *     )
 133          * b) Copy a file system file into storage
 134          *     array(
 135          *         'op'                  => 'store',
 136          *         'src'                 => <file system path>,
 137          *         'dst'                 => <storage path>,
 138          *         'overwrite'           => <boolean>,
 139          *         'overwriteSame'       => <boolean>
 140          *     )
 141          * c) Copy a file within storage
 142          *     array(
 143          *         'op'                  => 'copy',
 144          *         'src'                 => <storage path>,
 145          *         'dst'                 => <storage path>,
 146          *         'overwrite'           => <boolean>,
 147          *         'overwriteSame'       => <boolean>
 148          *     )
 149          * d) Move a file within storage
 150          *     array(
 151          *         'op'                  => 'move',
 152          *         'src'                 => <storage path>,
 153          *         'dst'                 => <storage path>,
 154          *         'overwrite'           => <boolean>,
 155          *         'overwriteSame'       => <boolean>
 156          *     )
 157          * e) Delete a file within storage
 158          *     array(
 159          *         'op'                  => 'delete',
 160          *         'src'                 => <storage path>,
 161          *         'ignoreMissingSource' => <boolean>
 162          *     )
 163          * f) Do nothing (no-op)
 164          *     array(
 165          *         'op'                  => 'null',
 166          *     )
 167          *
 168          * Boolean flags for operations (operation-specific):
 169          * 'ignoreMissingSource' : The operation will simply succeed and do
 170          *                         nothing if the source file does not exist.
 171          * 'overwrite'           : Any destination file will be overwritten.
 172          * 'overwriteSame'       : An error will not be given if a file already
 173          *                         exists at the destination that has the same
 174          *                         contents as the new contents to be written there.
 175          *
 176          * $opts is an associative of boolean flags, including:
 177          * 'force'               : Errors that would normally cause a rollback do not.
 178          *                         The remaining operations are still attempted if any fail.
 179          * 'nonLocking'          : No locks are acquired for the operations.
 180          *                         This can increase performance for non-critical writes.
 181          *                         This has no effect unless the 'force' flag is set.
 182          * 'allowStale'          : Don't require the latest available data.
 183          *                         This can increase performance for non-critical writes.
 184          *                         This has no effect unless the 'force' flag is set.
 185          * 'nonJournaled'        : Don't log this operation batch in the file journal.
 186          *                         This limits the ability of recovery scripts.
 187          *
 188          * Remarks on locking:
 189          * File system paths given to operations should refer to files that are
 190          * already locked or otherwise safe from modification from other processes.
 191          * Normally these files will be new temp files, which should be adequate.
 192          *
 193          * Return value:
 194          * This returns a Status, which contains all warnings and fatals that occured
 195          * during the operation. The 'failCount', 'successCount', and 'success' members
 196          * will reflect each operation attempted. The status will be "OK" unless:
 197          *     a) unexpected operation errors occurred (network partitions, disk full...)
 198          *     b) significant operation errors occured and 'force' was not set
 199          *
 200          * @param $ops Array List of operations to execute in order
 201          * @param $opts Array Batch operation options
 202          * @return Status
 203          */
 204         final public function doOperations( array $ops, array $opts = array() ) {
 205                 if ( $this->isReadOnly() ) {
 206                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 207                 }
 208                 if ( empty( $opts['force'] ) ) { // sanity
 209                         unset( $opts['nonLocking'] );
 210                         unset( $opts['allowStale'] );
 211                 }
 212                 return $this->doOperationsInternal( $ops, $opts );
 213         }
 214
 215         /**
 216          * @see FileBackend::doOperations()
 217          */
 218         abstract protected function doOperationsInternal( array $ops, array $opts );
 219
 220         /**
 221          * Same as doOperations() except it takes a single operation.
 222          * If you are doing a batch of operations that should either
 223          * all succeed or all fail, then use that function instead.
 224          *
 225          * @see FileBackend::doOperations()
 226          *
 227          * @param $op Array Operation
 228          * @param $opts Array Operation options
 229          * @return Status
 230          */
 231         final public function doOperation( array $op, array $opts = array() ) {
 232                 return $this->doOperations( array( $op ), $opts );
 233         }
 234
 235         /**
 236          * Performs a single create operation.
 237          * This sets $params['op'] to 'create' and passes it to doOperation().
 238          *
 239          * @see FileBackend::doOperation()
 240          *
 241          * @param $params Array Operation parameters
 242          * @param $opts Array Operation options
 243          * @return Status
 244          */
 245         final public function create( array $params, array $opts = array() ) {
 246                 $params['op'] = 'create';
 247                 return $this->doOperation( $params, $opts );
 248         }
 249
 250         /**
 251          * Performs a single store operation.
 252          * This sets $params['op'] to 'store' and passes it to doOperation().
 253          *
 254          * @see FileBackend::doOperation()
 255          *
 256          * @param $params Array Operation parameters
 257          * @param $opts Array Operation options
 258          * @return Status
 259          */
 260         final public function store( array $params, array $opts = array() ) {
 261                 $params['op'] = 'store';
 262                 return $this->doOperation( $params, $opts );
 263         }
 264
 265         /**
 266          * Performs a single copy operation.
 267          * This sets $params['op'] to 'copy' and passes it to doOperation().
 268          *
 269          * @see FileBackend::doOperation()
 270          *
 271          * @param $params Array Operation parameters
 272          * @param $opts Array Operation options
 273          * @return Status
 274          */
 275         final public function copy( array $params, array $opts = array() ) {
 276                 $params['op'] = 'copy';
 277                 return $this->doOperation( $params, $opts );
 278         }
 279
 280         /**
 281          * Performs a single move operation.
 282          * This sets $params['op'] to 'move' and passes it to doOperation().
 283          *
 284          * @see FileBackend::doOperation()
 285          *
 286          * @param $params Array Operation parameters
 287          * @param $opts Array Operation options
 288          * @return Status
 289          */
 290         final public function move( array $params, array $opts = array() ) {
 291                 $params['op'] = 'move';
 292                 return $this->doOperation( $params, $opts );
 293         }
 294
 295         /**
 296          * Performs a single delete operation.
 297          * This sets $params['op'] to 'delete' and passes it to doOperation().
 298          *
 299          * @see FileBackend::doOperation()
 300          *
 301          * @param $params Array Operation parameters
 302          * @param $opts Array Operation options
 303          * @return Status
 304          */
 305         final public function delete( array $params, array $opts = array() ) {
 306                 $params['op'] = 'delete';
 307                 return $this->doOperation( $params, $opts );
 308         }
 309
 310         /**
 311          * Concatenate a list of storage files into a single file system file.
 312          * The target path should refer to a file that is already locked or
 313          * otherwise safe from modification from other processes. Normally,
 314          * the file will be a new temp file, which should be adequate.
 315          * $params include:
 316          *     srcs          : ordered source storage paths (e.g. chunk1, chunk2, ...)
 317          *     dst           : file system path to 0-byte temp file
 318          *
 319          * @param $params Array Operation parameters
 320          * @return Status
 321          */
 322         abstract public function concatenate( array $params );
 323
 324         /**
 325          * Prepare a storage directory for usage.
 326          * This will create any required containers and parent directories.
 327          * Backends using key/value stores only need to create the container.
 328          *
 329          * $params include:
 330          *     dir : storage directory
 331          *
 332          * @param $params Array
 333          * @return Status
 334          */
 335         final public function prepare( array $params ) {
 336                 if ( $this->isReadOnly() ) {
 337                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 338                 }
 339                 return $this->doPrepare( $params );
 340         }
 341
 342         /**
 343          * @see FileBackend::prepare()
 344          */
 345         abstract protected function doPrepare( array $params );
 346
 347         /**
 348          * Take measures to block web access to a storage directory and
 349          * the container it belongs to. FS backends might add .htaccess
 350          * files whereas key/value store backends might restrict container
 351          * access to the auth user that represents end-users in web request.
 352          * This is not guaranteed to actually do anything.
 353          *
 354          * $params include:
 355          *     dir       : storage directory
 356          *     noAccess  : try to deny file access
 357          *     noListing : try to deny file listing
 358          *
 359          * @param $params Array
 360          * @return Status
 361          */
 362         final public function secure( array $params ) {
 363                 if ( $this->isReadOnly() ) {
 364                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 365                 }
 366                 $status = $this->doPrepare( $params ); // dir must exist to restrict it
 367                 if ( $status->isOK() ) {
 368                         $status->merge( $this->doSecure( $params ) );
 369                 }
 370                 return $status;
 371         }
 372
 373         /**
 374          * @see FileBackend::secure()
 375          */
 376         abstract protected function doSecure( array $params );
 377
 378         /**
 379          * Delete a storage directory if it is empty.
 380          * Backends using key/value stores may do nothing unless the directory
 381          * is that of an empty container, in which case it should be deleted.
 382          *
 383          * $params include:
 384          *     dir : storage directory
 385          *
 386          * @param $params Array
 387          * @return Status
 388          */
 389         final public function clean( array $params ) {
 390                 if ( $this->isReadOnly() ) {
 391                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 392                 }
 393                 return $this->doClean( $params );
 394         }
 395
 396         /**
 397          * @see FileBackend::clean()
 398          */
 399         abstract protected function doClean( array $params );
 400
 401         /**
 402          * Check if a file exists at a storage path in the backend.
 403          * This returns false if only a directory exists at the path.
 404          *
 405          * $params include:
 406          *     src    : source storage path
 407          *     latest : use the latest available data
 408          *
 409          * @param $params Array
 410          * @return bool|null Returns null on failure
 411          */
 412         abstract public function fileExists( array $params );
 413
 414         /**
 415          * Get the last-modified timestamp of the file at a storage path.
 416          *
 417          * $params include:
 418          *     src    : source storage path
 419          *     latest : use the latest available data
 420          *
 421          * @param $params Array
 422          * @return string|bool TS_MW timestamp or false on failure
 423          */
 424         abstract public function getFileTimestamp( array $params );
 425
 426         /**
 427          * Get the contents of a file at a storage path in the backend.
 428          * This should be avoided for potentially large files.
 429          *
 430          * $params include:
 431          *     src    : source storage path
 432          *     latest : use the latest available data
 433          *
 434          * @param $params Array
 435          * @return string|bool Returns false on failure
 436          */
 437         abstract public function getFileContents( array $params );
 438
 439         /**
 440          * Get the size (bytes) of a file at a storage path in the backend.
 441          *
 442          * $params include:
 443          *     src    : source storage path
 444          *     latest : use the latest available data
 445          *
 446          * @param $params Array
 447          * @return integer|bool Returns false on failure
 448          */
 449         abstract public function getFileSize( array $params );
 450
 451         /**
 452          * Get quick information about a file at a storage path in the backend.
 453          * If the file does not exist, then this returns false.
 454          * Otherwise, the result is an associative array that includes:
 455          *     mtime  : the last-modified timestamp (TS_MW)
 456          *     size   : the file size (bytes)
 457          * Additional values may be included for internal use only.
 458          *
 459          * $params include:
 460          *     src    : source storage path
 461          *     latest : use the latest available data
 462          *
 463          * @param $params Array
 464          * @return Array|bool|null Returns null on failure
 465          */
 466         abstract public function getFileStat( array $params );
 467
 468         /**
 469          * Get a SHA-1 hash of the file at a storage path in the backend.
 470          *
 471          * $params include:
 472          *     src    : source storage path
 473          *     latest : use the latest available data
 474          *
 475          * @param $params Array
 476          * @return string|bool Hash string or false on failure
 477          */
 478         abstract public function getFileSha1Base36( array $params );
 479
 480         /**
 481          * Get the properties of the file at a storage path in the backend.
 482          * Returns FSFile::placeholderProps() on failure.
 483          *
 484          * $params include:
 485          *     src    : source storage path
 486          *     latest : use the latest available data
 487          *
 488          * @param $params Array
 489          * @return Array
 490          */
 491         abstract public function getFileProps( array $params );
 492
 493         /**
 494          * Stream the file at a storage path in the backend.
 495          * If the file does not exists, a 404 error will be given.
 496          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
 497          * must be sent if streaming began, while none should be sent otherwise.
 498          * Implementations should flush the output buffer before sending data.
 499          *
 500          * $params include:
 501          *     src     : source storage path
 502          *     headers : additional HTTP headers to send on success
 503          *     latest  : use the latest available data
 504          *
 505          * @param $params Array
 506          * @return Status
 507          */
 508         abstract public function streamFile( array $params );
 509
 510         /**
 511          * Returns a file system file, identical to the file at a storage path.
 512          * The file returned is either:
 513          * a) A local copy of the file at a storage path in the backend.
 514          *    The temporary copy will have the same extension as the source.
 515          * b) An original of the file at a storage path in the backend.
 516          * Temporary files may be purged when the file object falls out of scope.
 517          *
 518          * Write operations should *never* be done on this file as some backends
 519          * may do internal tracking or may be instances of FileBackendMultiWrite.
 520          * In that later case, there are copies of the file that must stay in sync.
 521          * Additionally, further calls to this function may return the same file.
 522          *
 523          * $params include:
 524          *     src    : source storage path
 525          *     latest : use the latest available data
 526          *
 527          * @param $params Array
 528          * @return FSFile|null Returns null on failure
 529          */
 530         abstract public function getLocalReference( array $params );
 531
 532         /**
 533          * Get a local copy on disk of the file at a storage path in the backend.
 534          * The temporary copy will have the same file extension as the source.
 535          * Temporary files may be purged when the file object falls out of scope.
 536          *
 537          * $params include:
 538          *     src    : source storage path
 539          *     latest : use the latest available data
 540          *
 541          * @param $params Array
 542          * @return TempFSFile|null Returns null on failure
 543          */
 544         abstract public function getLocalCopy( array $params );
 545
 546         /**
 547          * Get an iterator to list out all stored files under a storage directory.
 548          * If the directory is of the form "mwstore://backend/container",
 549          * then all files in the container should be listed.
 550          * If the directory is of form "mwstore://backend/container/dir",
 551          * then all files under that container directory should be listed.
 552          * Results should be storage paths relative to the given directory.
 553          *
 554          * Storage backends with eventual consistency might return stale data.
 555          *
 556          * $params include:
 557          *     dir : storage path directory
 558          *
 559          * @return Traversable|Array|null Returns null on failure
 560          */
 561         abstract public function getFileList( array $params );
 562
 563         /**
 564          * Invalidate any in-process file existence and property cache.
 565          * If $paths is given, then only the cache for those files will be cleared.
 566          *
 567          * @param $paths Array Storage paths (optional)
 568          * @return void
 569          */
 570         public function clearCache( array $paths = null ) {}
 571
 572         /**
 573          * Lock the files at the given storage paths in the backend.
 574          * This will either lock all the files or none (on failure).
 575          *
 576          * Callers should consider using getScopedFileLocks() instead.
 577          *
 578          * @param $paths Array Storage paths
 579          * @param $type integer LockManager::LOCK_* constant
 580          * @return Status
 581          */
 582         final public function lockFiles( array $paths, $type ) {
 583                 return $this->lockManager->lock( $paths, $type );
 584         }
 585
 586         /**
 587          * Unlock the files at the given storage paths in the backend.
 588          *
 589          * @param $paths Array Storage paths
 590          * @param $type integer LockManager::LOCK_* constant
 591          * @return Status
 592          */
 593         final public function unlockFiles( array $paths, $type ) {
 594                 return $this->lockManager->unlock( $paths, $type );
 595         }
 596
 597         /**
 598          * Lock the files at the given storage paths in the backend.
 599          * This will either lock all the files or none (on failure).
 600          * On failure, the status object will be updated with errors.
 601          *
 602          * Once the return value goes out scope, the locks will be released and
 603          * the status updated. Unlock fatals will not change the status "OK" value.
 604          *
 605          * @param $paths Array Storage paths
 606          * @param $type integer LockManager::LOCK_* constant
 607          * @param $status Status Status to update on lock/unlock
 608          * @return ScopedLock|null Returns null on failure
 609          */
 610         final public function getScopedFileLocks( array $paths, $type, Status $status ) {
 611                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status );
 612         }
 613
 614         /**
 615          * Check if a given path is a "mwstore://" path.
 616          * This does not do any further validation or any existence checks.
 617          *
 618          * @param $path string
 619          * @return bool
 620          */
 621         final public static function isStoragePath( $path ) {
 622                 return ( strpos( $path, 'mwstore://' ) === 0 );
 623         }
 624
 625         /**
 626          * Split a storage path into a backend name, a container name,
 627          * and a relative file path. The relative path may be the empty string.
 628          * This does not do any path normalization or traversal checks.
 629          *
 630          * @param $storagePath string
 631          * @return Array (backend, container, rel object) or (null, null, null)
 632          */
 633         final public static function splitStoragePath( $storagePath ) {
 634                 if ( self::isStoragePath( $storagePath ) ) {
 635                         // Remove the "mwstore://" prefix and split the path
 636                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
 637                         if ( count( $parts ) >= 2 && $parts[0] != '' && $parts[1] != '' ) {
 638                                 if ( count( $parts ) == 3 ) {
 639                                         return $parts; // e.g. "backend/container/path"
 640                                 } else {
 641                                         return array( $parts[0], $parts[1], '' ); // e.g. "backend/container"
 642                                 }
 643                         }
 644                 }
 645                 return array( null, null, null );
 646         }
 647
 648         /**
 649          * Normalize a storage path by cleaning up directory separators.
 650          * Returns null if the path is not of the format of a valid storage path.
 651          *
 652          * @param $storagePath string
 653          * @return string|null
 654          */
 655         final public static function normalizeStoragePath( $storagePath ) {
 656                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
 657                 if ( $relPath !== null ) { // must be for this backend
 658                         $relPath = self::normalizeContainerPath( $relPath );
 659                         if ( $relPath !== null ) {
 660                                 return ( $relPath != '' )
 661                                         ? "mwstore://{$backend}/{$container}/{$relPath}"
 662                                         : "mwstore://{$backend}/{$container}";
 663                         }
 664                 }
 665                 return null;
 666         }
 667
 668         /**
 669          * Get the parent storage directory of a storage path.
 670          * This returns a path like "mwstore://backend/container",
 671          * "mwstore://backend/container/...", or null if there is no parent.
 672          *
 673          * @param $storagePath string
 674          * @return string|null
 675          */
 676         final public static function parentStoragePath( $storagePath ) {
 677                 $storagePath = dirname( $storagePath );
 678                 list( $b, $cont, $rel ) = self::splitStoragePath( $storagePath );
 679                 return ( $rel === null ) ? null : $storagePath;
 680         }
 681
 682         /**
 683          * Get the final extension from a storage or FS path
 684          *
 685          * @param $path string
 686          * @return string
 687          */
 688         final public static function extensionFromPath( $path ) {
 689                 $i = strrpos( $path, '.' );
 690                 return strtolower( $i ? substr( $path, $i + 1 ) : '' );
 691         }
 692
 693         /**
 694          * Validate and normalize a relative storage path.
 695          * Null is returned if the path involves directory traversal.
 696          * Traversal is insecure for FS backends and broken for others.
 697          *
 698          * @param $path string Storage path relative to a container
 699          * @return string|null
 700          */
 701         final protected static function normalizeContainerPath( $path ) {
 702                 // Normalize directory separators
 703                 $path = strtr( $path, '\\', '/' );
 704                 // Collapse any consecutive directory separators
 705                 $path = preg_replace( '![/]{2,}!', '/', $path );
 706                 // Remove any leading directory separator
 707                 $path = ltrim( $path, '/' );
 708                 // Use the same traversal protection as Title::secureAndSplit()
 709                 if ( strpos( $path, '.' ) !== false ) {
 710                         if (
 711                                 $path === '.' ||
 712                                 $path === '..' ||
 713                                 strpos( $path, './' ) === 0 ||
 714                                 strpos( $path, '../' ) === 0 ||
 715                                 strpos( $path, '/./' ) !== false ||
 716                                 strpos( $path, '/../' ) !== false
 717                         ) {
 718                                 return null;
 719                         }
 720                 }
 721                 return $path;
 722         }
 723 }