includes/filebackend/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  * Base class for all file backends.
  12  *
  13  * This program is free software; you can redistribute it and/or modify
  14  * it under the terms of the GNU General Public License as published by
  15  * the Free Software Foundation; either version 2 of the License, or
  16  * (at your option) any later version.
  17  *
  18  * This program is distributed in the hope that it will be useful,
  19  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  20  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  21  * GNU General Public License for more details.
  22  *
  23  * You should have received a copy of the GNU General Public License along
  24  * with this program; if not, write to the Free Software Foundation, Inc.,
  25  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  26  * http://www.gnu.org/copyleft/gpl.html
  27  *
  28  * @file
  29  * @ingroup FileBackend
  30  * @author Aaron Schulz
  31  */
  32
  33 /**
  34  * @brief Base class for all file backend classes (including multi-write backends).
  35  *
  36  * This class defines the methods as abstract that subclasses must implement.
  37  * Outside callers can assume that all backends will have these functions.
  38  *
  39  * All "storage paths" are of the format "mwstore://<backend>/<container>/<path>".
  40  * The "backend" portion is unique name for MediaWiki to refer to a backend, while
  41  * the "container" portion is a top-level directory of the backend. The "path" portion
  42  * is a relative path that uses UNIX file system (FS) notation, though any particular
  43  * backend may not actually be using a local filesystem. Therefore, the relative paths
  44  * are only virtual.
  45  *
  46  * Backend contents are stored under wiki-specific container names by default.
  47  * Global (qualified) backends are achieved by configuring the "wiki ID" to a constant.
  48  * For legacy reasons, the FSFileBackend class allows manually setting the paths of
  49  * containers to ones that do not respect the "wiki ID".
  50  *
  51  * In key/value stores, the container is the only hierarchy (the rest is emulated).
  52  * FS-based backends are somewhat more restrictive due to the existence of real
  53  * directory files; a regular file cannot have the same name as a directory. Other
  54  * backends with virtual directories may not have this limitation. Callers should
  55  * store files in such a way that no files and directories are under the same path.
  56  *
  57  * Methods of subclasses should avoid throwing exceptions at all costs.
  58  * As a corollary, external dependencies should be kept to a minimum.
  59  *
  60  * @ingroup FileBackend
  61  * @since 1.19
  62  */
  63 abstract class FileBackend {
  64         protected $name; // string; unique backend name
  65         protected $wikiId; // string; unique wiki name
  66         protected $readOnly; // string; read-only explanation message
  67         protected $parallelize; // string; when to do operations in parallel
  68         protected $concurrency; // integer; how many operations can be done in parallel
  69
  70         /** @var LockManager */
  71         protected $lockManager;
  72         /** @var FileJournal */
  73         protected $fileJournal;
  74
  75         /**
  76          * Create a new backend instance from configuration.
  77          * This should only be called from within FileBackendGroup.
  78          *
  79          * $config includes:
  80          *   - name        : The unique name of this backend.
  81          *                   This should consist of alphanumberic, '-', and '_' characters.
  82          *                   This name should not be changed after use (e.g. with journaling).
  83          *                   Note that the name is *not* used in actual container names.
  84          *   - wikiId      : Prefix to container names that is unique to this backend.
  85          *                   If not provided, this defaults to the current wiki ID.
  86          *                   It should only consist of alphanumberic, '-', and '_' characters.
  87          *                   This ID is what avoids collisions if multiple logical backends
  88          *                   use the same storage system, so this should be set carefully.
  89          *   - lockManager : Registered name of a file lock manager to use.
  90          *   - fileJournal : File journal configuration; see FileJournal::factory().
  91          *                   Journals simply log changes to files stored in the backend.
  92          *   - readOnly    : Write operations are disallowed if this is a non-empty string.
  93          *                   It should be an explanation for the backend being read-only.
  94          *   - parallelize : When to do file operations in parallel (when possible).
  95          *                   Allowed values are "implicit", "explicit" and "off".
  96          *   - concurrency : How many file operations can be done in parallel.
  97          *
  98          * @param $config Array
  99          * @throws MWException
 100          */
 101         public function __construct( array $config ) {
 102                 $this->name = $config['name'];
 103                 if ( !preg_match( '!^[a-zA-Z0-9-_]{1,255}$!', $this->name ) ) {
 104                         throw new MWException( "Backend name `{$this->name}` is invalid." );
 105                 }
 106                 $this->wikiId = isset( $config['wikiId'] )
 107                         ? $config['wikiId']
 108                         : wfWikiID(); // e.g. "my_wiki-en_"
 109                 $this->lockManager = ( $config['lockManager'] instanceof LockManager )
 110                         ? $config['lockManager']
 111                         : LockManagerGroup::singleton( $this->wikiId )->get( $config['lockManager'] );
 112                 $this->fileJournal = isset( $config['fileJournal'] )
 113                         ? ( ( $config['fileJournal'] instanceof FileJournal )
 114                                 ? $config['fileJournal']
 115                                 : FileJournal::factory( $config['fileJournal'], $this->name ) )
 116                         : FileJournal::factory( array( 'class' => 'NullFileJournal' ), $this->name );
 117                 $this->readOnly = isset( $config['readOnly'] )
 118                         ? (string)$config['readOnly']
 119                         : '';
 120                 $this->parallelize = isset( $config['parallelize'] )
 121                         ? (string)$config['parallelize']
 122                         : 'off';
 123                 $this->concurrency = isset( $config['concurrency'] )
 124                         ? (int)$config['concurrency']
 125                         : 50;
 126         }
 127
 128         /**
 129          * Get the unique backend name.
 130          * We may have multiple different backends of the same type.
 131          * For example, we can have two Swift backends using different proxies.
 132          *
 133          * @return string
 134          */
 135         final public function getName() {
 136                 return $this->name;
 137         }
 138
 139         /**
 140          * Get the wiki identifier used for this backend (possibly empty).
 141          * Note that this might *not* be in the same format as wfWikiID().
 142          *
 143          * @return string
 144          * @since 1.20
 145          */
 146         final public function getWikiId() {
 147                 return $this->wikiId;
 148         }
 149
 150         /**
 151          * Check if this backend is read-only
 152          *
 153          * @return bool
 154          */
 155         final public function isReadOnly() {
 156                 return ( $this->readOnly != '' );
 157         }
 158
 159         /**
 160          * Get an explanatory message if this backend is read-only
 161          *
 162          * @return string|bool Returns false if the backend is not read-only
 163          */
 164         final public function getReadOnlyReason() {
 165                 return ( $this->readOnly != '' ) ? $this->readOnly : false;
 166         }
 167
 168         /**
 169          * This is the main entry point into the backend for write operations.
 170          * Callers supply an ordered list of operations to perform as a transaction.
 171          * Files will be locked, the stat cache cleared, and then the operations attempted.
 172          * If any serious errors occur, all attempted operations will be rolled back.
 173          *
 174          * $ops is an array of arrays. The outer array holds a list of operations.
 175          * Each inner array is a set of key value pairs that specify an operation.
 176          *
 177          * Supported operations and their parameters. The supported actions are:
 178          *  - create
 179          *  - store
 180          *  - copy
 181          *  - move
 182          *  - delete
 183          *  - describe (since 1.21)
 184          *  - null
 185          *
 186          * a) Create a new file in storage with the contents of a string
 187          * @code
 188          *     array(
 189          *         'op'                  => 'create',
 190          *         'dst'                 => <storage path>,
 191          *         'content'             => <string of new file contents>,
 192          *         'overwrite'           => <boolean>,
 193          *         'overwriteSame'       => <boolean>,
 194          *         'headers'             => <HTTP header name/value map> # since 1.21
 195          *     );
 196          * @endcode
 197          *
 198          * b) Copy a file system file into storage
 199          * @code
 200          *     array(
 201          *         'op'                  => 'store',
 202          *         'src'                 => <file system path>,
 203          *         'dst'                 => <storage path>,
 204          *         'overwrite'           => <boolean>,
 205          *         'overwriteSame'       => <boolean>,
 206          *         'headers'             => <HTTP header name/value map> # since 1.21
 207          *     )
 208          * @endcode
 209          *
 210          * c) Copy a file within storage
 211          * @code
 212          *     array(
 213          *         'op'                  => 'copy',
 214          *         'src'                 => <storage path>,
 215          *         'dst'                 => <storage path>,
 216          *         'overwrite'           => <boolean>,
 217          *         'overwriteSame'       => <boolean>,
 218          *         'ignoreMissingSource' => <boolean>, # since 1.21
 219          *         'headers'             => <HTTP header name/value map> # since 1.21
 220          *     )
 221          * @endcode
 222          *
 223          * d) Move a file within storage
 224          * @code
 225          *     array(
 226          *         'op'                  => 'move',
 227          *         'src'                 => <storage path>,
 228          *         'dst'                 => <storage path>,
 229          *         'overwrite'           => <boolean>,
 230          *         'overwriteSame'       => <boolean>,
 231          *         'ignoreMissingSource' => <boolean>, # since 1.21
 232          *         'headers'             => <HTTP header name/value map> # since 1.21
 233          *     )
 234          * @endcode
 235          *
 236          * e) Delete a file within storage
 237          * @code
 238          *     array(
 239          *         'op'                  => 'delete',
 240          *         'src'                 => <storage path>,
 241          *         'ignoreMissingSource' => <boolean>
 242          *     )
 243          * @endcode
 244          *
 245          * f) Update metadata for a file within storage
 246          * @code
 247          *     array(
 248          *         'op'                  => 'describe',
 249          *         'src'                 => <storage path>,
 250          *         'headers'             => <HTTP header name/value map>
 251          *     )
 252          * @endcode
 253          *
 254          * g) Do nothing (no-op)
 255          * @code
 256          *     array(
 257          *         'op'                  => 'null',
 258          *     )
 259          * @endcode
 260          *
 261          * Boolean flags for operations (operation-specific):
 262          *   - ignoreMissingSource : The operation will simply succeed and do
 263          *                           nothing if the source file does not exist.
 264          *   - overwrite           : Any destination file will be overwritten.
 265          *   - overwriteSame       : An error will not be given if a file already
 266          *                           exists at the destination that has the same
 267          *                           contents as the new contents to be written there.
 268          *   - headers             : If supplied, the backend will return these headers when
 269          *                           GETs/HEADs of the destination file are made. Header values
 270          *                           should be smaller than 256 bytes, often options or numbers.
 271          *                           Content-Disposition headers can be longer, though the system
 272          *                           might ignore or truncate ones that are too long to store.
 273          *                           Existing headers will remain, but these will replace any
 274          *                           conflicting previous headers, and headers will be removed
 275          *                           if they are set to an empty string.
 276          *                           Backends that don't support metadata ignore this. (since 1.21)
 277          *
 278          * $opts is an associative of boolean flags, including:
 279          *   - force               : Operation precondition errors no longer trigger an abort.
 280          *                           Any remaining operations are still attempted. Unexpected
 281          *                           failures may still cause remaining operations to be aborted.
 282          *   - nonLocking          : No locks are acquired for the operations.
 283          *                           This can increase performance for non-critical writes.
 284          *                           This has no effect unless the 'force' flag is set.
 285          *   - nonJournaled        : Don't log this operation batch in the file journal.
 286          *                           This limits the ability of recovery scripts.
 287          *   - parallelize         : Try to do operations in parallel when possible.
 288          *   - bypassReadOnly      : Allow writes in read-only mode. (since 1.20)
 289          *   - preserveCache       : Don't clear the process cache before checking files.
 290          *                           This should only be used if all entries in the process
 291          *                           cache were added after the files were already locked. (since 1.20)
 292          *
 293          * @remarks Remarks on locking:
 294          * File system paths given to operations should refer to files that are
 295          * already locked or otherwise safe from modification from other processes.
 296          * Normally these files will be new temp files, which should be adequate.
 297          *
 298          * @par Return value:
 299          *
 300          * This returns a Status, which contains all warnings and fatals that occurred
 301          * during the operation. The 'failCount', 'successCount', and 'success' members
 302          * will reflect each operation attempted.
 303          *
 304          * The status will be "OK" unless:
 305          *   - a) unexpected operation errors occurred (network partitions, disk full...)
 306          *   - b) significant operation errors occurred and 'force' was not set
 307          *
 308          * @param array $ops List of operations to execute in order
 309          * @param array $opts Batch operation options
 310          * @return Status
 311          */
 312         final public function doOperations( array $ops, array $opts = array() ) {
 313                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 314                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 315                 }
 316                 if ( empty( $opts['force'] ) ) { // sanity
 317                         unset( $opts['nonLocking'] );
 318                 }
 319                 foreach ( $ops as &$op ) {
 320                         if ( isset( $op['disposition'] ) ) { // b/c (MW 1.20)
 321                                 $op['headers']['Content-Disposition'] = $op['disposition'];
 322                         }
 323                 }
 324                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 325                 return $this->doOperationsInternal( $ops, $opts );
 326         }
 327
 328         /**
 329          * @see FileBackend::doOperations()
 330          */
 331         abstract protected function doOperationsInternal( array $ops, array $opts );
 332
 333         /**
 334          * Same as doOperations() except it takes a single operation.
 335          * If you are doing a batch of operations that should either
 336          * all succeed or all fail, then use that function instead.
 337          *
 338          * @see FileBackend::doOperations()
 339          *
 340          * @param array $op Operation
 341          * @param array $opts Operation options
 342          * @return Status
 343          */
 344         final public function doOperation( array $op, array $opts = array() ) {
 345                 return $this->doOperations( array( $op ), $opts );
 346         }
 347
 348         /**
 349          * Performs a single create operation.
 350          * This sets $params['op'] to 'create' and passes it to doOperation().
 351          *
 352          * @see FileBackend::doOperation()
 353          *
 354          * @param array $params Operation parameters
 355          * @param array $opts Operation options
 356          * @return Status
 357          */
 358         final public function create( array $params, array $opts = array() ) {
 359                 return $this->doOperation( array( 'op' => 'create' ) + $params, $opts );
 360         }
 361
 362         /**
 363          * Performs a single store operation.
 364          * This sets $params['op'] to 'store' and passes it to doOperation().
 365          *
 366          * @see FileBackend::doOperation()
 367          *
 368          * @param array $params Operation parameters
 369          * @param array $opts Operation options
 370          * @return Status
 371          */
 372         final public function store( array $params, array $opts = array() ) {
 373                 return $this->doOperation( array( 'op' => 'store' ) + $params, $opts );
 374         }
 375
 376         /**
 377          * Performs a single copy operation.
 378          * This sets $params['op'] to 'copy' and passes it to doOperation().
 379          *
 380          * @see FileBackend::doOperation()
 381          *
 382          * @param array $params Operation parameters
 383          * @param array $opts Operation options
 384          * @return Status
 385          */
 386         final public function copy( array $params, array $opts = array() ) {
 387                 return $this->doOperation( array( 'op' => 'copy' ) + $params, $opts );
 388         }
 389
 390         /**
 391          * Performs a single move operation.
 392          * This sets $params['op'] to 'move' and passes it to doOperation().
 393          *
 394          * @see FileBackend::doOperation()
 395          *
 396          * @param array $params Operation parameters
 397          * @param array $opts Operation options
 398          * @return Status
 399          */
 400         final public function move( array $params, array $opts = array() ) {
 401                 return $this->doOperation( array( 'op' => 'move' ) + $params, $opts );
 402         }
 403
 404         /**
 405          * Performs a single delete operation.
 406          * This sets $params['op'] to 'delete' and passes it to doOperation().
 407          *
 408          * @see FileBackend::doOperation()
 409          *
 410          * @param array $params Operation parameters
 411          * @param array $opts Operation options
 412          * @return Status
 413          */
 414         final public function delete( array $params, array $opts = array() ) {
 415                 return $this->doOperation( array( 'op' => 'delete' ) + $params, $opts );
 416         }
 417
 418         /**
 419          * Performs a single describe operation.
 420          * This sets $params['op'] to 'describe' and passes it to doOperation().
 421          *
 422          * @see FileBackend::doOperation()
 423          *
 424          * @param array $params Operation parameters
 425          * @param array $opts Operation options
 426          * @return Status
 427          * @since 1.21
 428          */
 429         final public function describe( array $params, array $opts = array() ) {
 430                 return $this->doOperation( array( 'op' => 'describe' ) + $params, $opts );
 431         }
 432
 433         /**
 434          * Perform a set of independent file operations on some files.
 435          *
 436          * This does no locking, nor journaling, and possibly no stat calls.
 437          * Any destination files that already exist will be overwritten.
 438          * This should *only* be used on non-original files, like cache files.
 439          *
 440          * Supported operations and their parameters:
 441          *  - create
 442          *  - store
 443          *  - copy
 444          *  - move
 445          *  - delete
 446          *  - describe (since 1.21)
 447          *  - null
 448          *
 449          * a) Create a new file in storage with the contents of a string
 450          * @code
 451          *     array(
 452          *         'op'                  => 'create',
 453          *         'dst'                 => <storage path>,
 454          *         'content'             => <string of new file contents>,
 455          *         'headers'             => <HTTP header name/value map> # since 1.21
 456          *     )
 457          * @endcode
 458          *
 459          * b) Copy a file system file into storage
 460          * @code
 461          *     array(
 462          *         'op'                  => 'store',
 463          *         'src'                 => <file system path>,
 464          *         'dst'                 => <storage path>,
 465          *         'headers'             => <HTTP header name/value map> # since 1.21
 466          *     )
 467          * @endcode
 468          *
 469          * c) Copy a file within storage
 470          * @code
 471          *     array(
 472          *         'op'                  => 'copy',
 473          *         'src'                 => <storage path>,
 474          *         'dst'                 => <storage path>,
 475          *         'ignoreMissingSource' => <boolean>, # since 1.21
 476          *         'headers'             => <HTTP header name/value map> # since 1.21
 477          *     )
 478          * @endcode
 479          *
 480          * d) Move a file within storage
 481          * @code
 482          *     array(
 483          *         'op'                  => 'move',
 484          *         'src'                 => <storage path>,
 485          *         'dst'                 => <storage path>,
 486          *         'ignoreMissingSource' => <boolean>, # since 1.21
 487          *         'headers'             => <HTTP header name/value map> # since 1.21
 488          *     )
 489          * @endcode
 490          *
 491          * e) Delete a file within storage
 492          * @code
 493          *     array(
 494          *         'op'                  => 'delete',
 495          *         'src'                 => <storage path>,
 496          *         'ignoreMissingSource' => <boolean>
 497          *     )
 498          * @endcode
 499          *
 500          * f) Update metadata for a file within storage
 501          * @code
 502          *     array(
 503          *         'op'                  => 'describe',
 504          *         'src'                 => <storage path>,
 505          *         'headers'             => <HTTP header name/value map>
 506          *     )
 507          * @endcode
 508          *
 509          * g) Do nothing (no-op)
 510          * @code
 511          *     array(
 512          *         'op'                  => 'null',
 513          *     )
 514          * @endcode
 515          *
 516          * @par Boolean flags for operations (operation-specific):
 517          *   - ignoreMissingSource : The operation will simply succeed and do
 518          *                           nothing if the source file does not exist.
 519          *   - headers             : If supplied with a header name/value map, the backend will
 520          *                           reply with these headers when GETs/HEADs of the destination
 521          *                           file are made. Header values should be smaller than 256 bytes.
 522          *                           Content-Disposition headers can be longer, though the system
 523          *                           might ignore or truncate ones that are too long to store.
 524          *                           Existing headers will remain, but these will replace any
 525          *                           conflicting previous headers, and headers will be removed
 526          *                           if they are set to an empty string.
 527          *                           Backends that don't support metadata ignore this. (since 1.21)
 528          *
 529          * $opts is an associative of boolean flags, including:
 530          *   - bypassReadOnly      : Allow writes in read-only mode (since 1.20)
 531          *
 532          * @par Return value:
 533          * This returns a Status, which contains all warnings and fatals that occurred
 534          * during the operation. The 'failCount', 'successCount', and 'success' members
 535          * will reflect each operation attempted for the given files. The status will be
 536          * considered "OK" as long as no fatal errors occurred.
 537          *
 538          * @param array $ops Set of operations to execute
 539          * @param array $opts Batch operation options
 540          * @return Status
 541          * @since 1.20
 542          */
 543         final public function doQuickOperations( array $ops, array $opts = array() ) {
 544                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 545                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 546                 }
 547                 foreach ( $ops as &$op ) {
 548                         $op['overwrite'] = true; // avoids RTTs in key/value stores
 549                         if ( isset( $op['disposition'] ) ) { // b/c (MW 1.20)
 550                                 $op['headers']['Content-Disposition'] = $op['disposition'];
 551                         }
 552                 }
 553                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 554                 return $this->doQuickOperationsInternal( $ops );
 555         }
 556
 557         /**
 558          * @see FileBackend::doQuickOperations()
 559          * @since 1.20
 560          */
 561         abstract protected function doQuickOperationsInternal( array $ops );
 562
 563         /**
 564          * Same as doQuickOperations() except it takes a single operation.
 565          * If you are doing a batch of operations, then use that function instead.
 566          *
 567          * @see FileBackend::doQuickOperations()
 568          *
 569          * @param array $op Operation
 570          * @return Status
 571          * @since 1.20
 572          */
 573         final public function doQuickOperation( array $op ) {
 574                 return $this->doQuickOperations( array( $op ) );
 575         }
 576
 577         /**
 578          * Performs a single quick create operation.
 579          * This sets $params['op'] to 'create' and passes it to doQuickOperation().
 580          *
 581          * @see FileBackend::doQuickOperation()
 582          *
 583          * @param array $params Operation parameters
 584          * @return Status
 585          * @since 1.20
 586          */
 587         final public function quickCreate( array $params ) {
 588                 return $this->doQuickOperation( array( 'op' => 'create' ) + $params );
 589         }
 590
 591         /**
 592          * Performs a single quick store operation.
 593          * This sets $params['op'] to 'store' and passes it to doQuickOperation().
 594          *
 595          * @see FileBackend::doQuickOperation()
 596          *
 597          * @param array $params Operation parameters
 598          * @return Status
 599          * @since 1.20
 600          */
 601         final public function quickStore( array $params ) {
 602                 return $this->doQuickOperation( array( 'op' => 'store' ) + $params );
 603         }
 604
 605         /**
 606          * Performs a single quick copy operation.
 607          * This sets $params['op'] to 'copy' and passes it to doQuickOperation().
 608          *
 609          * @see FileBackend::doQuickOperation()
 610          *
 611          * @param array $params Operation parameters
 612          * @return Status
 613          * @since 1.20
 614          */
 615         final public function quickCopy( array $params ) {
 616                 return $this->doQuickOperation( array( 'op' => 'copy' ) + $params );
 617         }
 618
 619         /**
 620          * Performs a single quick move operation.
 621          * This sets $params['op'] to 'move' and passes it to doQuickOperation().
 622          *
 623          * @see FileBackend::doQuickOperation()
 624          *
 625          * @param array $params Operation parameters
 626          * @return Status
 627          * @since 1.20
 628          */
 629         final public function quickMove( array $params ) {
 630                 return $this->doQuickOperation( array( 'op' => 'move' ) + $params );
 631         }
 632
 633         /**
 634          * Performs a single quick delete operation.
 635          * This sets $params['op'] to 'delete' and passes it to doQuickOperation().
 636          *
 637          * @see FileBackend::doQuickOperation()
 638          *
 639          * @param array $params Operation parameters
 640          * @return Status
 641          * @since 1.20
 642          */
 643         final public function quickDelete( array $params ) {
 644                 return $this->doQuickOperation( array( 'op' => 'delete' ) + $params );
 645         }
 646
 647         /**
 648          * Performs a single quick describe operation.
 649          * This sets $params['op'] to 'describe' and passes it to doQuickOperation().
 650          *
 651          * @see FileBackend::doQuickOperation()
 652          *
 653          * @param array $params Operation parameters
 654          * @return Status
 655          * @since 1.21
 656          */
 657         final public function quickDescribe( array $params ) {
 658                 return $this->doQuickOperation( array( 'op' => 'describe' ) + $params );
 659         }
 660
 661         /**
 662          * Concatenate a list of storage files into a single file system file.
 663          * The target path should refer to a file that is already locked or
 664          * otherwise safe from modification from other processes. Normally,
 665          * the file will be a new temp file, which should be adequate.
 666          *
 667          * @param array $params Operation parameters
 668          * $params include:
 669          *   - srcs        : ordered source storage paths (e.g. chunk1, chunk2, ...)
 670          *   - dst         : file system path to 0-byte temp file
 671          *   - parallelize : try to do operations in parallel when possible
 672          * @return Status
 673          */
 674         abstract public function concatenate( array $params );
 675
 676         /**
 677          * Prepare a storage directory for usage.
 678          * This will create any required containers and parent directories.
 679          * Backends using key/value stores only need to create the container.
 680          *
 681          * The 'noAccess' and 'noListing' parameters works the same as in secure(),
 682          * except they are only applied *if* the directory/container had to be created.
 683          * These flags should always be set for directories that have private files.
 684          *
 685          * @param array $params
 686          * $params include:
 687          *   - dir            : storage directory
 688          *   - noAccess       : try to deny file access (since 1.20)
 689          *   - noListing      : try to deny file listing (since 1.20)
 690          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 691          * @return Status
 692          */
 693         final public function prepare( array $params ) {
 694                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 695                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 696                 }
 697                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 698                 return $this->doPrepare( $params );
 699         }
 700
 701         /**
 702          * @see FileBackend::prepare()
 703          */
 704         abstract protected function doPrepare( array $params );
 705
 706         /**
 707          * Take measures to block web access to a storage directory and
 708          * the container it belongs to. FS backends might add .htaccess
 709          * files whereas key/value store backends might revoke container
 710          * access to the storage user representing end-users in web requests.
 711          * This is not guaranteed to actually do anything.
 712          *
 713          * @param array $params
 714          * $params include:
 715          *   - dir            : storage directory
 716          *   - noAccess       : try to deny file access
 717          *   - noListing      : try to deny file listing
 718          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 719          * @return Status
 720          */
 721         final public function secure( array $params ) {
 722                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 723                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 724                 }
 725                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 726                 return $this->doSecure( $params );
 727         }
 728
 729         /**
 730          * @see FileBackend::secure()
 731          */
 732         abstract protected function doSecure( array $params );
 733
 734         /**
 735          * Remove measures to block web access to a storage directory and
 736          * the container it belongs to. FS backends might remove .htaccess
 737          * files whereas key/value store backends might grant container
 738          * access to the storage user representing end-users in web requests.
 739          * This essentially can undo the result of secure() calls.
 740          *
 741          * @param array $params
 742          * $params include:
 743          *   - dir            : storage directory
 744          *   - access         : try to allow file access
 745          *   - listing        : try to allow file listing
 746          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 747          * @return Status
 748          * @since 1.20
 749          */
 750         final public function publish( array $params ) {
 751                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 752                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 753                 }
 754                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 755                 return $this->doPublish( $params );
 756         }
 757
 758         /**
 759          * @see FileBackend::publish()
 760          */
 761         abstract protected function doPublish( array $params );
 762
 763         /**
 764          * Delete a storage directory if it is empty.
 765          * Backends using key/value stores may do nothing unless the directory
 766          * is that of an empty container, in which case it will be deleted.
 767          *
 768          * @param array $params
 769          * $params include:
 770          *   - dir            : storage directory
 771          *   - recursive      : recursively delete empty subdirectories first (since 1.20)
 772          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 773          * @return Status
 774          */
 775         final public function clean( array $params ) {
 776                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 777                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 778                 }
 779                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 780                 return $this->doClean( $params );
 781         }
 782
 783         /**
 784          * @see FileBackend::clean()
 785          */
 786         abstract protected function doClean( array $params );
 787
 788         /**
 789          * Enter file operation scope.
 790          * This just makes PHP ignore user aborts/disconnects until the return
 791          * value leaves scope. This returns null and does nothing in CLI mode.
 792          *
 793          * @return ScopedCallback|null
 794          */
 795         final protected function getScopedPHPBehaviorForOps() {
 796                 if ( php_sapi_name() != 'cli' ) { // http://bugs.php.net/bug.php?id=47540
 797                         $old = ignore_user_abort( true ); // avoid half-finished operations
 798                         return new ScopedCallback( function() use ( $old ) { ignore_user_abort( $old ); } );
 799                 }
 800                 return null;
 801         }
 802
 803         /**
 804          * Check if a file exists at a storage path in the backend.
 805          * This returns false if only a directory exists at the path.
 806          *
 807          * @param array $params
 808          * $params include:
 809          *   - src    : source storage path
 810          *   - latest : use the latest available data
 811          * @return bool|null Returns null on failure
 812          */
 813         abstract public function fileExists( array $params );
 814
 815         /**
 816          * Get the last-modified timestamp of the file at a storage path.
 817          *
 818          * @param array $params
 819          * $params include:
 820          *   - src    : source storage path
 821          *   - latest : use the latest available data
 822          * @return string|bool TS_MW timestamp or false on failure
 823          */
 824         abstract public function getFileTimestamp( array $params );
 825
 826         /**
 827          * Get the contents of a file at a storage path in the backend.
 828          * This should be avoided for potentially large files.
 829          *
 830          * @param array $params
 831          * $params include:
 832          *   - src    : source storage path
 833          *   - latest : use the latest available data
 834          * @return string|bool Returns false on failure
 835          */
 836         final public function getFileContents( array $params ) {
 837                 $contents = $this->getFileContentsMulti(
 838                         array( 'srcs' => array( $params['src'] ) ) + $params );
 839
 840                 return $contents[$params['src']];
 841         }
 842
 843         /**
 844          * Like getFileContents() except it takes an array of storage paths
 845          * and returns a map of storage paths to strings (or null on failure).
 846          * The map keys (paths) are in the same order as the provided list of paths.
 847          *
 848          * @see FileBackend::getFileContents()
 849          *
 850          * @param array $params
 851          * $params include:
 852          *   - srcs        : list of source storage paths
 853          *   - latest      : use the latest available data
 854          *   - parallelize : try to do operations in parallel when possible
 855          * @return Array Map of (path name => string or false on failure)
 856          * @since 1.20
 857          */
 858         abstract public function getFileContentsMulti( array $params );
 859
 860         /**
 861          * Get the size (bytes) of a file at a storage path in the backend.
 862          *
 863          * @param array $params
 864          * $params include:
 865          *   - src    : source storage path
 866          *   - latest : use the latest available data
 867          * @return integer|bool Returns false on failure
 868          */
 869         abstract public function getFileSize( array $params );
 870
 871         /**
 872          * Get quick information about a file at a storage path in the backend.
 873          * If the file does not exist, then this returns false.
 874          * Otherwise, the result is an associative array that includes:
 875          *   - mtime  : the last-modified timestamp (TS_MW)
 876          *   - size   : the file size (bytes)
 877          * Additional values may be included for internal use only.
 878          *
 879          * @param array $params
 880          * $params include:
 881          *   - src    : source storage path
 882          *   - latest : use the latest available data
 883          * @return Array|bool|null Returns null on failure
 884          */
 885         abstract public function getFileStat( array $params );
 886
 887         /**
 888          * Get a SHA-1 hash of the file at a storage path in the backend.
 889          *
 890          * @param array $params
 891          * $params include:
 892          *   - src    : source storage path
 893          *   - latest : use the latest available data
 894          * @return string|bool Hash string or false on failure
 895          */
 896         abstract public function getFileSha1Base36( array $params );
 897
 898         /**
 899          * Get the properties of the file at a storage path in the backend.
 900          * This gives the result of FSFile::getProps() on a local copy of the file.
 901          *
 902          * @param array $params
 903          * $params include:
 904          *   - src    : source storage path
 905          *   - latest : use the latest available data
 906          * @return Array Returns FSFile::placeholderProps() on failure
 907          */
 908         abstract public function getFileProps( array $params );
 909
 910         /**
 911          * Stream the file at a storage path in the backend.
 912          * If the file does not exists, an HTTP 404 error will be given.
 913          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
 914          * will be sent if streaming began, while none will be sent otherwise.
 915          * Implementations should flush the output buffer before sending data.
 916          *
 917          * @param array $params
 918          * $params include:
 919          *   - src     : source storage path
 920          *   - headers : list of additional HTTP headers to send on success
 921          *   - latest  : use the latest available data
 922          * @return Status
 923          */
 924         abstract public function streamFile( array $params );
 925
 926         /**
 927          * Returns a file system file, identical to the file at a storage path.
 928          * The file returned is either:
 929          *   - a) A local copy of the file at a storage path in the backend.
 930          *        The temporary copy will have the same extension as the source.
 931          *   - b) An original of the file at a storage path in the backend.
 932          * Temporary files may be purged when the file object falls out of scope.
 933          *
 934          * Write operations should *never* be done on this file as some backends
 935          * may do internal tracking or may be instances of FileBackendMultiWrite.
 936          * In that later case, there are copies of the file that must stay in sync.
 937          * Additionally, further calls to this function may return the same file.
 938          *
 939          * @param array $params
 940          * $params include:
 941          *   - src    : source storage path
 942          *   - latest : use the latest available data
 943          * @return FSFile|null Returns null on failure
 944          */
 945         final public function getLocalReference( array $params ) {
 946                 $fsFiles = $this->getLocalReferenceMulti(
 947                         array( 'srcs' => array( $params['src'] ) ) + $params );
 948
 949                 return $fsFiles[$params['src']];
 950         }
 951
 952         /**
 953          * Like getLocalReference() except it takes an array of storage paths
 954          * and returns a map of storage paths to FSFile objects (or null on failure).
 955          * The map keys (paths) are in the same order as the provided list of paths.
 956          *
 957          * @see FileBackend::getLocalReference()
 958          *
 959          * @param array $params
 960          * $params include:
 961          *   - srcs        : list of source storage paths
 962          *   - latest      : use the latest available data
 963          *   - parallelize : try to do operations in parallel when possible
 964          * @return Array Map of (path name => FSFile or null on failure)
 965          * @since 1.20
 966          */
 967         abstract public function getLocalReferenceMulti( array $params );
 968
 969         /**
 970          * Get a local copy on disk of the file at a storage path in the backend.
 971          * The temporary copy will have the same file extension as the source.
 972          * Temporary files may be purged when the file object falls out of scope.
 973          *
 974          * @param array $params
 975          * $params include:
 976          *   - src    : source storage path
 977          *   - latest : use the latest available data
 978          * @return TempFSFile|null Returns null on failure
 979          */
 980         final public function getLocalCopy( array $params ) {
 981                 $tmpFiles = $this->getLocalCopyMulti(
 982                         array( 'srcs' => array( $params['src'] ) ) + $params );
 983
 984                 return $tmpFiles[$params['src']];
 985         }
 986
 987         /**
 988          * Like getLocalCopy() except it takes an array of storage paths and
 989          * returns a map of storage paths to TempFSFile objects (or null on failure).
 990          * The map keys (paths) are in the same order as the provided list of paths.
 991          *
 992          * @see FileBackend::getLocalCopy()
 993          *
 994          * @param array $params
 995          * $params include:
 996          *   - srcs        : list of source storage paths
 997          *   - latest      : use the latest available data
 998          *   - parallelize : try to do operations in parallel when possible
 999          * @return Array Map of (path name => TempFSFile or null on failure)
1000          * @since 1.20
1001          */
1002         abstract public function getLocalCopyMulti( array $params );
1003
1004         /**
1005          * Return an HTTP URL to a given file that requires no authentication to use.
1006          * The URL may be pre-authenticated (via some token in the URL) and temporary.
1007          * This will return null if the backend cannot make an HTTP URL for the file.
1008          *
1009          * This is useful for key/value stores when using scripts that seek around
1010          * large files and those scripts (and the backend) support HTTP Range headers.
1011          * Otherwise, one would need to use getLocalReference(), which involves loading
1012          * the entire file on to local disk.
1013          *
1014          * @param array $params
1015          * $params include:
1016          *   - src : source storage path
1017          *   - ttl : lifetime (seconds) if pre-authenticated; default is 1 day
1018          * @return string|null
1019          * @since 1.21
1020          */
1021         abstract public function getFileHttpUrl( array $params );
1022
1023         /**
1024          * Check if a directory exists at a given storage path.
1025          * Backends using key/value stores will check if the path is a
1026          * virtual directory, meaning there are files under the given directory.
1027          *
1028          * Storage backends with eventual consistency might return stale data.
1029          *
1030          * @param $params array
1031          * $params include:
1032          *   - dir : storage directory
1033          * @return bool|null Returns null on failure
1034          * @since 1.20
1035          */
1036         abstract public function directoryExists( array $params );
1037
1038         /**
1039          * Get an iterator to list *all* directories under a storage directory.
1040          * If the directory is of the form "mwstore://backend/container",
1041          * then all directories in the container will be listed.
1042          * If the directory is of form "mwstore://backend/container/dir",
1043          * then all directories directly under that directory will be listed.
1044          * Results will be storage directories relative to the given directory.
1045          *
1046          * Storage backends with eventual consistency might return stale data.
1047          *
1048          * @param $params array
1049          * $params include:
1050          *   - dir     : storage directory
1051          *   - topOnly : only return direct child dirs of the directory
1052          * @return Traversable|Array|null Returns null on failure
1053          * @since 1.20
1054          */
1055         abstract public function getDirectoryList( array $params );
1056
1057         /**
1058          * Same as FileBackend::getDirectoryList() except only lists
1059          * directories that are immediately under the given directory.
1060          *
1061          * Storage backends with eventual consistency might return stale data.
1062          *
1063          * @param $params array
1064          * $params include:
1065          *   - dir : storage directory
1066          * @return Traversable|Array|null Returns null on failure
1067          * @since 1.20
1068          */
1069         final public function getTopDirectoryList( array $params ) {
1070                 return $this->getDirectoryList( array( 'topOnly' => true ) + $params );
1071         }
1072
1073         /**
1074          * Get an iterator to list *all* stored files under a storage directory.
1075          * If the directory is of the form "mwstore://backend/container",
1076          * then all files in the container will be listed.
1077          * If the directory is of form "mwstore://backend/container/dir",
1078          * then all files under that directory will be listed.
1079          * Results will be storage paths relative to the given directory.
1080          *
1081          * Storage backends with eventual consistency might return stale data.
1082          *
1083          * @param $params array
1084          * $params include:
1085          *   - dir     : storage directory
1086          *   - topOnly : only return direct child files of the directory (since 1.20)
1087          * @return Traversable|Array|null Returns null on failure
1088          */
1089         abstract public function getFileList( array $params );
1090
1091         /**
1092          * Same as FileBackend::getFileList() except only lists
1093          * files that are immediately under the given directory.
1094          *
1095          * Storage backends with eventual consistency might return stale data.
1096          *
1097          * @param $params array
1098          * $params include:
1099          *   - dir : storage directory
1100          * @return Traversable|Array|null Returns null on failure
1101          * @since 1.20
1102          */
1103         final public function getTopFileList( array $params ) {
1104                 return $this->getFileList( array( 'topOnly' => true ) + $params );
1105         }
1106
1107         /**
1108          * Preload persistent file stat and property cache into in-process cache.
1109          * This should be used when stat calls will be made on a known list of a many files.
1110          *
1111          * @param array $paths Storage paths
1112          * @return void
1113          */
1114         public function preloadCache( array $paths ) {}
1115
1116         /**
1117          * Invalidate any in-process file stat and property cache.
1118          * If $paths is given, then only the cache for those files will be cleared.
1119          *
1120          * @param array $paths Storage paths (optional)
1121          * @return void
1122          */
1123         public function clearCache( array $paths = null ) {}
1124
1125         /**
1126          * Lock the files at the given storage paths in the backend.
1127          * This will either lock all the files or none (on failure).
1128          *
1129          * Callers should consider using getScopedFileLocks() instead.
1130          *
1131          * @param array $paths Storage paths
1132          * @param $type integer LockManager::LOCK_* constant
1133          * @return Status
1134          */
1135         final public function lockFiles( array $paths, $type ) {
1136                 return $this->lockManager->lock( $paths, $type );
1137         }
1138
1139         /**
1140          * Unlock the files at the given storage paths in the backend.
1141          *
1142          * @param array $paths Storage paths
1143          * @param $type integer LockManager::LOCK_* constant
1144          * @return Status
1145          */
1146         final public function unlockFiles( array $paths, $type ) {
1147                 return $this->lockManager->unlock( $paths, $type );
1148         }
1149
1150         /**
1151          * Lock the files at the given storage paths in the backend.
1152          * This will either lock all the files or none (on failure).
1153          * On failure, the status object will be updated with errors.
1154          *
1155          * Once the return value goes out scope, the locks will be released and
1156          * the status updated. Unlock fatals will not change the status "OK" value.
1157          *
1158          * @param array $paths Storage paths
1159          * @param $type integer LockManager::LOCK_* constant
1160          * @param $status Status Status to update on lock/unlock
1161          * @return ScopedLock|null Returns null on failure
1162          */
1163         final public function getScopedFileLocks( array $paths, $type, Status $status ) {
1164                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status );
1165         }
1166
1167         /**
1168          * Get an array of scoped locks needed for a batch of file operations.
1169          *
1170          * Normally, FileBackend::doOperations() handles locking, unless
1171          * the 'nonLocking' param is passed in. This function is useful if you
1172          * want the files to be locked for a broader scope than just when the
1173          * files are changing. For example, if you need to update DB metadata,
1174          * you may want to keep the files locked until finished.
1175          *
1176          * @see FileBackend::doOperations()
1177          *
1178          * @param array $ops List of file operations to FileBackend::doOperations()
1179          * @param $status Status Status to update on lock/unlock
1180          * @return Array List of ScopedFileLocks or null values
1181          * @since 1.20
1182          */
1183         abstract public function getScopedLocksForOps( array $ops, Status $status );
1184
1185         /**
1186          * Get the root storage path of this backend.
1187          * All container paths are "subdirectories" of this path.
1188          *
1189          * @return string Storage path
1190          * @since 1.20
1191          */
1192         final public function getRootStoragePath() {
1193                 return "mwstore://{$this->name}";
1194         }
1195
1196         /**
1197          * Get the storage path for the given container for this backend
1198          *
1199          * @param string $container Container name
1200          * @return string Storage path
1201          * @since 1.21
1202          */
1203         final public function getContainerStoragePath( $container ) {
1204                 return $this->getRootStoragePath() . "/{$container}";
1205         }
1206
1207         /**
1208          * Get the file journal object for this backend
1209          *
1210          * @return FileJournal
1211          */
1212         final public function getJournal() {
1213                 return $this->fileJournal;
1214         }
1215
1216         /**
1217          * Check if a given path is a "mwstore://" path.
1218          * This does not do any further validation or any existence checks.
1219          *
1220          * @param $path string
1221          * @return bool
1222          */
1223         final public static function isStoragePath( $path ) {
1224                 return ( strpos( $path, 'mwstore://' ) === 0 );
1225         }
1226
1227         /**
1228          * Split a storage path into a backend name, a container name,
1229          * and a relative file path. The relative path may be the empty string.
1230          * This does not do any path normalization or traversal checks.
1231          *
1232          * @param $storagePath string
1233          * @return Array (backend, container, rel object) or (null, null, null)
1234          */
1235         final public static function splitStoragePath( $storagePath ) {
1236                 if ( self::isStoragePath( $storagePath ) ) {
1237                         // Remove the "mwstore://" prefix and split the path
1238                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
1239                         if ( count( $parts ) >= 2 && $parts[0] != '' && $parts[1] != '' ) {
1240                                 if ( count( $parts ) == 3 ) {
1241                                         return $parts; // e.g. "backend/container/path"
1242                                 } else {
1243                                         return array( $parts[0], $parts[1], '' ); // e.g. "backend/container"
1244                                 }
1245                         }
1246                 }
1247                 return array( null, null, null );
1248         }
1249
1250         /**
1251          * Normalize a storage path by cleaning up directory separators.
1252          * Returns null if the path is not of the format of a valid storage path.
1253          *
1254          * @param $storagePath string
1255          * @return string|null
1256          */
1257         final public static function normalizeStoragePath( $storagePath ) {
1258                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
1259                 if ( $relPath !== null ) { // must be for this backend
1260                         $relPath = self::normalizeContainerPath( $relPath );
1261                         if ( $relPath !== null ) {
1262                                 return ( $relPath != '' )
1263                                         ? "mwstore://{$backend}/{$container}/{$relPath}"
1264                                         : "mwstore://{$backend}/{$container}";
1265                         }
1266                 }
1267                 return null;
1268         }
1269
1270         /**
1271          * Get the parent storage directory of a storage path.
1272          * This returns a path like "mwstore://backend/container",
1273          * "mwstore://backend/container/...", or null if there is no parent.
1274          *
1275          * @param $storagePath string
1276          * @return string|null
1277          */
1278         final public static function parentStoragePath( $storagePath ) {
1279                 $storagePath = dirname( $storagePath );
1280                 list( , , $rel ) = self::splitStoragePath( $storagePath );
1281                 return ( $rel === null ) ? null : $storagePath;
1282         }
1283
1284         /**
1285          * Get the final extension from a storage or FS path
1286          *
1287          * @param $path string
1288          * @return string
1289          */
1290         final public static function extensionFromPath( $path ) {
1291                 $i = strrpos( $path, '.' );
1292                 return strtolower( $i ? substr( $path, $i + 1 ) : '' );
1293         }
1294
1295         /**
1296          * Check if a relative path has no directory traversals
1297          *
1298          * @param $path string
1299          * @return bool
1300          * @since 1.20
1301          */
1302         final public static function isPathTraversalFree( $path ) {
1303                 return ( self::normalizeContainerPath( $path ) !== null );
1304         }
1305
1306         /**
1307          * Build a Content-Disposition header value per RFC 6266.
1308          *
1309          * @param string $type One of (attachment, inline)
1310          * @param string $filename Suggested file name (should not contain slashes)
1311          * @throws MWException
1312          * @return string
1313          * @since 1.20
1314          */
1315         final public static function makeContentDisposition( $type, $filename = '' ) {
1316                 $parts = array();
1317
1318                 $type = strtolower( $type );
1319                 if ( !in_array( $type, array( 'inline', 'attachment' ) ) ) {
1320                         throw new MWException( "Invalid Content-Disposition type '$type'." );
1321                 }
1322                 $parts[] = $type;
1323
1324                 if ( strlen( $filename ) ) {
1325                         $parts[] = "filename*=UTF-8''" . rawurlencode( basename( $filename ) );
1326                 }
1327
1328                 return implode( ';', $parts );
1329         }
1330
1331         /**
1332          * Validate and normalize a relative storage path.
1333          * Null is returned if the path involves directory traversal.
1334          * Traversal is insecure for FS backends and broken for others.
1335          *
1336          * This uses the same traversal protection as Title::secureAndSplit().
1337          *
1338          * @param string $path Storage path relative to a container
1339          * @return string|null
1340          */
1341         final protected static function normalizeContainerPath( $path ) {
1342                 // Normalize directory separators
1343                 $path = strtr( $path, '\\', '/' );
1344                 // Collapse any consecutive directory separators
1345                 $path = preg_replace( '![/]{2,}!', '/', $path );
1346                 // Remove any leading directory separator
1347                 $path = ltrim( $path, '/' );
1348                 // Use the same traversal protection as Title::secureAndSplit()
1349                 if ( strpos( $path, '.' ) !== false ) {
1350                         if (
1351                                 $path === '.' ||
1352                                 $path === '..' ||
1353                                 strpos( $path, './' ) === 0 ||
1354                                 strpos( $path, '../' ) === 0 ||
1355                                 strpos( $path, '/./' ) !== false ||
1356                                 strpos( $path, '/../' ) !== false
1357                         ) {
1358                                 return null;
1359                         }
1360                 }
1361                 return $path;
1362         }
1363 }