includes/filebackend/FileBackend.php

   1 <?php
   2 /**
   3  * @defgroup FileBackend File backend
   4  *
   5  * File backend is used to interact with file storage systems,
   6  * such as the local file system, NFS, or cloud storage systems.
   7  */
   8
   9 /**
  10  * Base class for all file backends.
  11  *
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  20  * GNU General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License along
  23  * with this program; if not, write to the Free Software Foundation, Inc.,
  24  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  25  * http://www.gnu.org/copyleft/gpl.html
  26  *
  27  * @file
  28  * @ingroup FileBackend
  29  * @author Aaron Schulz
  30  */
  31
  32 /**
  33  * @brief Base class for all file backend classes (including multi-write backends).
  34  *
  35  * This class defines the methods as abstract that subclasses must implement.
  36  * Outside callers can assume that all backends will have these functions.
  37  *
  38  * All "storage paths" are of the format "mwstore://<backend>/<container>/<path>".
  39  * The "backend" portion is unique name for MediaWiki to refer to a backend, while
  40  * the "container" portion is a top-level directory of the backend. The "path" portion
  41  * is a relative path that uses UNIX file system (FS) notation, though any particular
  42  * backend may not actually be using a local filesystem. Therefore, the relative paths
  43  * are only virtual.
  44  *
  45  * Backend contents are stored under wiki-specific container names by default.
  46  * Global (qualified) backends are achieved by configuring the "wiki ID" to a constant.
  47  * For legacy reasons, the FSFileBackend class allows manually setting the paths of
  48  * containers to ones that do not respect the "wiki ID".
  49  *
  50  * In key/value stores, the container is the only hierarchy (the rest is emulated).
  51  * FS-based backends are somewhat more restrictive due to the existence of real
  52  * directory files; a regular file cannot have the same name as a directory. Other
  53  * backends with virtual directories may not have this limitation. Callers should
  54  * store files in such a way that no files and directories are under the same path.
  55  *
  56  * Methods of subclasses should avoid throwing exceptions at all costs.
  57  * As a corollary, external dependencies should be kept to a minimum.
  58  *
  59  * @ingroup FileBackend
  60  * @since 1.19
  61  */
  62 abstract class FileBackend {
  63         protected $name; // string; unique backend name
  64         protected $wikiId; // string; unique wiki name
  65         protected $readOnly; // string; read-only explanation message
  66         protected $parallelize; // string; when to do operations in parallel
  67         protected $concurrency; // integer; how many operations can be done in parallel
  68
  69         /** @var LockManager */
  70         protected $lockManager;
  71         /** @var FileJournal */
  72         protected $fileJournal;
  73
  74         /**
  75          * Create a new backend instance from configuration.
  76          * This should only be called from within FileBackendGroup.
  77          *
  78          * $config includes:
  79          *   - name        : The unique name of this backend.
  80          *                   This should consist of alphanumberic, '-', and '_' characters.
  81          *                   This name should not be changed after use (e.g. with journaling).
  82          *                   Note that the name is *not* used in actual container names.
  83          *   - wikiId      : Prefix to container names that is unique to this backend.
  84          *                   If not provided, this defaults to the current wiki ID.
  85          *                   It should only consist of alphanumberic, '-', and '_' characters.
  86          *                   This ID is what avoids collisions if multiple logical backends
  87          *                   use the same storage system, so this should be set carefully.
  88          *   - lockManager : Registered name of a file lock manager to use.
  89          *   - fileJournal : File journal configuration; see FileJournal::factory().
  90          *                   Journals simply log changes to files stored in the backend.
  91          *   - readOnly    : Write operations are disallowed if this is a non-empty string.
  92          *                   It should be an explanation for the backend being read-only.
  93          *   - parallelize : When to do file operations in parallel (when possible).
  94          *                   Allowed values are "implicit", "explicit" and "off".
  95          *   - concurrency : How many file operations can be done in parallel.
  96          *
  97          * @param $config Array
  98          * @throws MWException
  99          */
 100         public function __construct( array $config ) {
 101                 $this->name = $config['name'];
 102                 if ( !preg_match( '!^[a-zA-Z0-9-_]{1,255}$!', $this->name ) ) {
 103                         throw new MWException( "Backend name `{$this->name}` is invalid." );
 104                 }
 105                 $this->wikiId = isset( $config['wikiId'] )
 106                         ? $config['wikiId']
 107                         : wfWikiID(); // e.g. "my_wiki-en_"
 108                 $this->lockManager = ( $config['lockManager'] instanceof LockManager )
 109                         ? $config['lockManager']
 110                         : LockManagerGroup::singleton( $this->wikiId )->get( $config['lockManager'] );
 111                 $this->fileJournal = isset( $config['fileJournal'] )
 112                         ? ( ( $config['fileJournal'] instanceof FileJournal )
 113                                 ? $config['fileJournal']
 114                                 : FileJournal::factory( $config['fileJournal'], $this->name ) )
 115                         : FileJournal::factory( array( 'class' => 'NullFileJournal' ), $this->name );
 116                 $this->readOnly = isset( $config['readOnly'] )
 117                         ? (string)$config['readOnly']
 118                         : '';
 119                 $this->parallelize = isset( $config['parallelize'] )
 120                         ? (string)$config['parallelize']
 121                         : 'off';
 122                 $this->concurrency = isset( $config['concurrency'] )
 123                         ? (int)$config['concurrency']
 124                         : 50;
 125         }
 126
 127         /**
 128          * Get the unique backend name.
 129          * We may have multiple different backends of the same type.
 130          * For example, we can have two Swift backends using different proxies.
 131          *
 132          * @return string
 133          */
 134         final public function getName() {
 135                 return $this->name;
 136         }
 137
 138         /**
 139          * Get the wiki identifier used for this backend (possibly empty).
 140          * Note that this might *not* be in the same format as wfWikiID().
 141          *
 142          * @return string
 143          * @since 1.20
 144          */
 145         final public function getWikiId() {
 146                 return $this->wikiId;
 147         }
 148
 149         /**
 150          * Check if this backend is read-only
 151          *
 152          * @return bool
 153          */
 154         final public function isReadOnly() {
 155                 return ( $this->readOnly != '' );
 156         }
 157
 158         /**
 159          * Get an explanatory message if this backend is read-only
 160          *
 161          * @return string|bool Returns false if the backend is not read-only
 162          */
 163         final public function getReadOnlyReason() {
 164                 return ( $this->readOnly != '' ) ? $this->readOnly : false;
 165         }
 166
 167         /**
 168          * This is the main entry point into the backend for write operations.
 169          * Callers supply an ordered list of operations to perform as a transaction.
 170          * Files will be locked, the stat cache cleared, and then the operations attempted.
 171          * If any serious errors occur, all attempted operations will be rolled back.
 172          *
 173          * $ops is an array of arrays. The outer array holds a list of operations.
 174          * Each inner array is a set of key value pairs that specify an operation.
 175          *
 176          * Supported operations and their parameters. The supported actions are:
 177          *  - create
 178          *  - store
 179          *  - copy
 180          *  - move
 181          *  - delete
 182          *  - describe (since 1.21)
 183          *  - null
 184          *
 185          * a) Create a new file in storage with the contents of a string
 186          * @code
 187          *     array(
 188          *         'op'                  => 'create',
 189          *         'dst'                 => <storage path>,
 190          *         'content'             => <string of new file contents>,
 191          *         'overwrite'           => <boolean>,
 192          *         'overwriteSame'       => <boolean>,
 193          *         'headers'             => <HTTP header name/value map> # since 1.21
 194          *     );
 195          * @endcode
 196          *
 197          * b) Copy a file system file into storage
 198          * @code
 199          *     array(
 200          *         'op'                  => 'store',
 201          *         'src'                 => <file system path>,
 202          *         'dst'                 => <storage path>,
 203          *         'overwrite'           => <boolean>,
 204          *         'overwriteSame'       => <boolean>,
 205          *         'headers'             => <HTTP header name/value map> # since 1.21
 206          *     )
 207          * @endcode
 208          *
 209          * c) Copy a file within storage
 210          * @code
 211          *     array(
 212          *         'op'                  => 'copy',
 213          *         'src'                 => <storage path>,
 214          *         'dst'                 => <storage path>,
 215          *         'overwrite'           => <boolean>,
 216          *         'overwriteSame'       => <boolean>,
 217          *         'ignoreMissingSource' => <boolean>, # since 1.21
 218          *         'headers'             => <HTTP header name/value map> # since 1.21
 219          *     )
 220          * @endcode
 221          *
 222          * d) Move a file within storage
 223          * @code
 224          *     array(
 225          *         'op'                  => 'move',
 226          *         'src'                 => <storage path>,
 227          *         'dst'                 => <storage path>,
 228          *         'overwrite'           => <boolean>,
 229          *         'overwriteSame'       => <boolean>,
 230          *         'ignoreMissingSource' => <boolean>, # since 1.21
 231          *         'headers'             => <HTTP header name/value map> # since 1.21
 232          *     )
 233          * @endcode
 234          *
 235          * e) Delete a file within storage
 236          * @code
 237          *     array(
 238          *         'op'                  => 'delete',
 239          *         'src'                 => <storage path>,
 240          *         'ignoreMissingSource' => <boolean>
 241          *     )
 242          * @endcode
 243          *
 244          * f) Update metadata for a file within storage
 245          * @code
 246          *     array(
 247          *         'op'                  => 'describe',
 248          *         'src'                 => <storage path>,
 249          *         'headers'             => <HTTP header name/value map>
 250          *     )
 251          * @endcode
 252          *
 253          * g) Do nothing (no-op)
 254          * @code
 255          *     array(
 256          *         'op'                  => 'null',
 257          *     )
 258          * @endcode
 259          *
 260          * Boolean flags for operations (operation-specific):
 261          *   - ignoreMissingSource : The operation will simply succeed and do
 262          *                           nothing if the source file does not exist.
 263          *   - overwrite           : Any destination file will be overwritten.
 264          *   - overwriteSame       : If a file already exists at the destination with the
 265          *                           same contents, then do nothing to the destination file
 266          *                           instead of giving an error. This does not compare headers.
 267          *                           This option is ignored if 'overwrite' is already provided.
 268          *   - headers             : If supplied, the result of merging these headers with any
 269          *                           existing source file headers (replacing conflicting ones)
 270          *                           will be set as the destination file headers. Headers are
 271          *                           deleted if their value is set to the empty string. When a
 272          *                           file has headers they are included in responses to GET and
 273          *                           HEAD requests to the backing store for that file.
 274          *                           Header values should be no larger than 255 bytes, except for
 275          *                           Content-Disposition. The system might ignore or truncate any
 276          *                           headers that are too long to store (exact limits will vary).
 277          *                           Backends that don't support metadata ignore this. (since 1.21)
 278          *
 279          * $opts is an associative of boolean flags, including:
 280          *   - force               : Operation precondition errors no longer trigger an abort.
 281          *                           Any remaining operations are still attempted. Unexpected
 282          *                           failures may still cause remaining operations to be aborted.
 283          *   - nonLocking          : No locks are acquired for the operations.
 284          *                           This can increase performance for non-critical writes.
 285          *                           This has no effect unless the 'force' flag is set.
 286          *   - nonJournaled        : Don't log this operation batch in the file journal.
 287          *                           This limits the ability of recovery scripts.
 288          *   - parallelize         : Try to do operations in parallel when possible.
 289          *   - bypassReadOnly      : Allow writes in read-only mode. (since 1.20)
 290          *   - preserveCache       : Don't clear the process cache before checking files.
 291          *                           This should only be used if all entries in the process
 292          *                           cache were added after the files were already locked. (since 1.20)
 293          *
 294          * @remarks Remarks on locking:
 295          * File system paths given to operations should refer to files that are
 296          * already locked or otherwise safe from modification from other processes.
 297          * Normally these files will be new temp files, which should be adequate.
 298          *
 299          * @par Return value:
 300          *
 301          * This returns a Status, which contains all warnings and fatals that occurred
 302          * during the operation. The 'failCount', 'successCount', and 'success' members
 303          * will reflect each operation attempted.
 304          *
 305          * The status will be "OK" unless:
 306          *   - a) unexpected operation errors occurred (network partitions, disk full...)
 307          *   - b) significant operation errors occurred and 'force' was not set
 308          *
 309          * @param array $ops List of operations to execute in order
 310          * @param array $opts Batch operation options
 311          * @return Status
 312          */
 313         final public function doOperations( array $ops, array $opts = array() ) {
 314                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 315                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 316                 }
 317                 if ( empty( $opts['force'] ) ) { // sanity
 318                         unset( $opts['nonLocking'] );
 319                 }
 320                 foreach ( $ops as &$op ) {
 321                         if ( isset( $op['disposition'] ) ) { // b/c (MW 1.20)
 322                                 $op['headers']['Content-Disposition'] = $op['disposition'];
 323                         }
 324                 }
 325                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 326                 return $this->doOperationsInternal( $ops, $opts );
 327         }
 328
 329         /**
 330          * @see FileBackend::doOperations()
 331          */
 332         abstract protected function doOperationsInternal( array $ops, array $opts );
 333
 334         /**
 335          * Same as doOperations() except it takes a single operation.
 336          * If you are doing a batch of operations that should either
 337          * all succeed or all fail, then use that function instead.
 338          *
 339          * @see FileBackend::doOperations()
 340          *
 341          * @param array $op Operation
 342          * @param array $opts Operation options
 343          * @return Status
 344          */
 345         final public function doOperation( array $op, array $opts = array() ) {
 346                 return $this->doOperations( array( $op ), $opts );
 347         }
 348
 349         /**
 350          * Performs a single create operation.
 351          * This sets $params['op'] to 'create' and passes it to doOperation().
 352          *
 353          * @see FileBackend::doOperation()
 354          *
 355          * @param array $params Operation parameters
 356          * @param array $opts Operation options
 357          * @return Status
 358          */
 359         final public function create( array $params, array $opts = array() ) {
 360                 return $this->doOperation( array( 'op' => 'create' ) + $params, $opts );
 361         }
 362
 363         /**
 364          * Performs a single store operation.
 365          * This sets $params['op'] to 'store' and passes it to doOperation().
 366          *
 367          * @see FileBackend::doOperation()
 368          *
 369          * @param array $params Operation parameters
 370          * @param array $opts Operation options
 371          * @return Status
 372          */
 373         final public function store( array $params, array $opts = array() ) {
 374                 return $this->doOperation( array( 'op' => 'store' ) + $params, $opts );
 375         }
 376
 377         /**
 378          * Performs a single copy operation.
 379          * This sets $params['op'] to 'copy' and passes it to doOperation().
 380          *
 381          * @see FileBackend::doOperation()
 382          *
 383          * @param array $params Operation parameters
 384          * @param array $opts Operation options
 385          * @return Status
 386          */
 387         final public function copy( array $params, array $opts = array() ) {
 388                 return $this->doOperation( array( 'op' => 'copy' ) + $params, $opts );
 389         }
 390
 391         /**
 392          * Performs a single move operation.
 393          * This sets $params['op'] to 'move' and passes it to doOperation().
 394          *
 395          * @see FileBackend::doOperation()
 396          *
 397          * @param array $params Operation parameters
 398          * @param array $opts Operation options
 399          * @return Status
 400          */
 401         final public function move( array $params, array $opts = array() ) {
 402                 return $this->doOperation( array( 'op' => 'move' ) + $params, $opts );
 403         }
 404
 405         /**
 406          * Performs a single delete operation.
 407          * This sets $params['op'] to 'delete' and passes it to doOperation().
 408          *
 409          * @see FileBackend::doOperation()
 410          *
 411          * @param array $params Operation parameters
 412          * @param array $opts Operation options
 413          * @return Status
 414          */
 415         final public function delete( array $params, array $opts = array() ) {
 416                 return $this->doOperation( array( 'op' => 'delete' ) + $params, $opts );
 417         }
 418
 419         /**
 420          * Performs a single describe operation.
 421          * This sets $params['op'] to 'describe' and passes it to doOperation().
 422          *
 423          * @see FileBackend::doOperation()
 424          *
 425          * @param array $params Operation parameters
 426          * @param array $opts Operation options
 427          * @return Status
 428          * @since 1.21
 429          */
 430         final public function describe( array $params, array $opts = array() ) {
 431                 return $this->doOperation( array( 'op' => 'describe' ) + $params, $opts );
 432         }
 433
 434         /**
 435          * Perform a set of independent file operations on some files.
 436          *
 437          * This does no locking, nor journaling, and possibly no stat calls.
 438          * Any destination files that already exist will be overwritten.
 439          * This should *only* be used on non-original files, like cache files.
 440          *
 441          * Supported operations and their parameters:
 442          *  - create
 443          *  - store
 444          *  - copy
 445          *  - move
 446          *  - delete
 447          *  - describe (since 1.21)
 448          *  - null
 449          *
 450          * a) Create a new file in storage with the contents of a string
 451          * @code
 452          *     array(
 453          *         'op'                  => 'create',
 454          *         'dst'                 => <storage path>,
 455          *         'content'             => <string of new file contents>,
 456          *         'headers'             => <HTTP header name/value map> # since 1.21
 457          *     )
 458          * @endcode
 459          *
 460          * b) Copy a file system file into storage
 461          * @code
 462          *     array(
 463          *         'op'                  => 'store',
 464          *         'src'                 => <file system path>,
 465          *         'dst'                 => <storage path>,
 466          *         'headers'             => <HTTP header name/value map> # since 1.21
 467          *     )
 468          * @endcode
 469          *
 470          * c) Copy a file within storage
 471          * @code
 472          *     array(
 473          *         'op'                  => 'copy',
 474          *         'src'                 => <storage path>,
 475          *         'dst'                 => <storage path>,
 476          *         'ignoreMissingSource' => <boolean>, # since 1.21
 477          *         'headers'             => <HTTP header name/value map> # since 1.21
 478          *     )
 479          * @endcode
 480          *
 481          * d) Move a file within storage
 482          * @code
 483          *     array(
 484          *         'op'                  => 'move',
 485          *         'src'                 => <storage path>,
 486          *         'dst'                 => <storage path>,
 487          *         'ignoreMissingSource' => <boolean>, # since 1.21
 488          *         'headers'             => <HTTP header name/value map> # since 1.21
 489          *     )
 490          * @endcode
 491          *
 492          * e) Delete a file within storage
 493          * @code
 494          *     array(
 495          *         'op'                  => 'delete',
 496          *         'src'                 => <storage path>,
 497          *         'ignoreMissingSource' => <boolean>
 498          *     )
 499          * @endcode
 500          *
 501          * f) Update metadata for a file within storage
 502          * @code
 503          *     array(
 504          *         'op'                  => 'describe',
 505          *         'src'                 => <storage path>,
 506          *         'headers'             => <HTTP header name/value map>
 507          *     )
 508          * @endcode
 509          *
 510          * g) Do nothing (no-op)
 511          * @code
 512          *     array(
 513          *         'op'                  => 'null',
 514          *     )
 515          * @endcode
 516          *
 517          * @par Boolean flags for operations (operation-specific):
 518          *   - ignoreMissingSource : The operation will simply succeed and do
 519          *                           nothing if the source file does not exist.
 520          *   - headers             : If supplied with a header name/value map, the backend will
 521          *                           reply with these headers when GETs/HEADs of the destination
 522          *                           file are made. Header values should be smaller than 256 bytes.
 523          *                           Content-Disposition headers can be longer, though the system
 524          *                           might ignore or truncate ones that are too long to store.
 525          *                           Existing headers will remain, but these will replace any
 526          *                           conflicting previous headers, and headers will be removed
 527          *                           if they are set to an empty string.
 528          *                           Backends that don't support metadata ignore this. (since 1.21)
 529          *
 530          * $opts is an associative of boolean flags, including:
 531          *   - bypassReadOnly      : Allow writes in read-only mode (since 1.20)
 532          *
 533          * @par Return value:
 534          * This returns a Status, which contains all warnings and fatals that occurred
 535          * during the operation. The 'failCount', 'successCount', and 'success' members
 536          * will reflect each operation attempted for the given files. The status will be
 537          * considered "OK" as long as no fatal errors occurred.
 538          *
 539          * @param array $ops Set of operations to execute
 540          * @param array $opts Batch operation options
 541          * @return Status
 542          * @since 1.20
 543          */
 544         final public function doQuickOperations( array $ops, array $opts = array() ) {
 545                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 546                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 547                 }
 548                 foreach ( $ops as &$op ) {
 549                         $op['overwrite'] = true; // avoids RTTs in key/value stores
 550                         if ( isset( $op['disposition'] ) ) { // b/c (MW 1.20)
 551                                 $op['headers']['Content-Disposition'] = $op['disposition'];
 552                         }
 553                 }
 554                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 555                 return $this->doQuickOperationsInternal( $ops );
 556         }
 557
 558         /**
 559          * @see FileBackend::doQuickOperations()
 560          * @since 1.20
 561          */
 562         abstract protected function doQuickOperationsInternal( array $ops );
 563
 564         /**
 565          * Same as doQuickOperations() except it takes a single operation.
 566          * If you are doing a batch of operations, then use that function instead.
 567          *
 568          * @see FileBackend::doQuickOperations()
 569          *
 570          * @param array $op Operation
 571          * @return Status
 572          * @since 1.20
 573          */
 574         final public function doQuickOperation( array $op ) {
 575                 return $this->doQuickOperations( array( $op ) );
 576         }
 577
 578         /**
 579          * Performs a single quick create operation.
 580          * This sets $params['op'] to 'create' and passes it to doQuickOperation().
 581          *
 582          * @see FileBackend::doQuickOperation()
 583          *
 584          * @param array $params Operation parameters
 585          * @return Status
 586          * @since 1.20
 587          */
 588         final public function quickCreate( array $params ) {
 589                 return $this->doQuickOperation( array( 'op' => 'create' ) + $params );
 590         }
 591
 592         /**
 593          * Performs a single quick store operation.
 594          * This sets $params['op'] to 'store' and passes it to doQuickOperation().
 595          *
 596          * @see FileBackend::doQuickOperation()
 597          *
 598          * @param array $params Operation parameters
 599          * @return Status
 600          * @since 1.20
 601          */
 602         final public function quickStore( array $params ) {
 603                 return $this->doQuickOperation( array( 'op' => 'store' ) + $params );
 604         }
 605
 606         /**
 607          * Performs a single quick copy operation.
 608          * This sets $params['op'] to 'copy' and passes it to doQuickOperation().
 609          *
 610          * @see FileBackend::doQuickOperation()
 611          *
 612          * @param array $params Operation parameters
 613          * @return Status
 614          * @since 1.20
 615          */
 616         final public function quickCopy( array $params ) {
 617                 return $this->doQuickOperation( array( 'op' => 'copy' ) + $params );
 618         }
 619
 620         /**
 621          * Performs a single quick move operation.
 622          * This sets $params['op'] to 'move' and passes it to doQuickOperation().
 623          *
 624          * @see FileBackend::doQuickOperation()
 625          *
 626          * @param array $params Operation parameters
 627          * @return Status
 628          * @since 1.20
 629          */
 630         final public function quickMove( array $params ) {
 631                 return $this->doQuickOperation( array( 'op' => 'move' ) + $params );
 632         }
 633
 634         /**
 635          * Performs a single quick delete operation.
 636          * This sets $params['op'] to 'delete' and passes it to doQuickOperation().
 637          *
 638          * @see FileBackend::doQuickOperation()
 639          *
 640          * @param array $params Operation parameters
 641          * @return Status
 642          * @since 1.20
 643          */
 644         final public function quickDelete( array $params ) {
 645                 return $this->doQuickOperation( array( 'op' => 'delete' ) + $params );
 646         }
 647
 648         /**
 649          * Performs a single quick describe operation.
 650          * This sets $params['op'] to 'describe' and passes it to doQuickOperation().
 651          *
 652          * @see FileBackend::doQuickOperation()
 653          *
 654          * @param array $params Operation parameters
 655          * @return Status
 656          * @since 1.21
 657          */
 658         final public function quickDescribe( array $params ) {
 659                 return $this->doQuickOperation( array( 'op' => 'describe' ) + $params );
 660         }
 661
 662         /**
 663          * Concatenate a list of storage files into a single file system file.
 664          * The target path should refer to a file that is already locked or
 665          * otherwise safe from modification from other processes. Normally,
 666          * the file will be a new temp file, which should be adequate.
 667          *
 668          * @param array $params Operation parameters
 669          * $params include:
 670          *   - srcs        : ordered source storage paths (e.g. chunk1, chunk2, ...)
 671          *   - dst         : file system path to 0-byte temp file
 672          *   - parallelize : try to do operations in parallel when possible
 673          * @return Status
 674          */
 675         abstract public function concatenate( array $params );
 676
 677         /**
 678          * Prepare a storage directory for usage.
 679          * This will create any required containers and parent directories.
 680          * Backends using key/value stores only need to create the container.
 681          *
 682          * The 'noAccess' and 'noListing' parameters works the same as in secure(),
 683          * except they are only applied *if* the directory/container had to be created.
 684          * These flags should always be set for directories that have private files.
 685          * However, setting them is not guaranteed to actually do anything.
 686          * Additional server configuration may be needed to achieve the desired effect.
 687          *
 688          * @param array $params
 689          * $params include:
 690          *   - dir            : storage directory
 691          *   - noAccess       : try to deny file access (since 1.20)
 692          *   - noListing      : try to deny file listing (since 1.20)
 693          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 694          * @return Status
 695          */
 696         final public function prepare( array $params ) {
 697                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 698                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 699                 }
 700                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 701                 return $this->doPrepare( $params );
 702         }
 703
 704         /**
 705          * @see FileBackend::prepare()
 706          */
 707         abstract protected function doPrepare( array $params );
 708
 709         /**
 710          * Take measures to block web access to a storage directory and
 711          * the container it belongs to. FS backends might add .htaccess
 712          * files whereas key/value store backends might revoke container
 713          * access to the storage user representing end-users in web requests.
 714          *
 715          * This is not guaranteed to actually make files or listings publically hidden.
 716          * Additional server configuration may be needed to achieve the desired effect.
 717          *
 718          * @param array $params
 719          * $params include:
 720          *   - dir            : storage directory
 721          *   - noAccess       : try to deny file access
 722          *   - noListing      : try to deny file listing
 723          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 724          * @return Status
 725          */
 726         final public function secure( array $params ) {
 727                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 728                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 729                 }
 730                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 731                 return $this->doSecure( $params );
 732         }
 733
 734         /**
 735          * @see FileBackend::secure()
 736          */
 737         abstract protected function doSecure( array $params );
 738
 739         /**
 740          * Remove measures to block web access to a storage directory and
 741          * the container it belongs to. FS backends might remove .htaccess
 742          * files whereas key/value store backends might grant container
 743          * access to the storage user representing end-users in web requests.
 744          * This essentially can undo the result of secure() calls.
 745          *
 746          * This is not guaranteed to actually make files or listings publically viewable.
 747          * Additional server configuration may be needed to achieve the desired effect.
 748          *
 749          * @param array $params
 750          * $params include:
 751          *   - dir            : storage directory
 752          *   - access         : try to allow file access
 753          *   - listing        : try to allow file listing
 754          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 755          * @return Status
 756          * @since 1.20
 757          */
 758         final public function publish( array $params ) {
 759                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 760                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 761                 }
 762                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 763                 return $this->doPublish( $params );
 764         }
 765
 766         /**
 767          * @see FileBackend::publish()
 768          */
 769         abstract protected function doPublish( array $params );
 770
 771         /**
 772          * Delete a storage directory if it is empty.
 773          * Backends using key/value stores may do nothing unless the directory
 774          * is that of an empty container, in which case it will be deleted.
 775          *
 776          * @param array $params
 777          * $params include:
 778          *   - dir            : storage directory
 779          *   - recursive      : recursively delete empty subdirectories first (since 1.20)
 780          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 781          * @return Status
 782          */
 783         final public function clean( array $params ) {
 784                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 785                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 786                 }
 787                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 788                 return $this->doClean( $params );
 789         }
 790
 791         /**
 792          * @see FileBackend::clean()
 793          */
 794         abstract protected function doClean( array $params );
 795
 796         /**
 797          * Enter file operation scope.
 798          * This just makes PHP ignore user aborts/disconnects until the return
 799          * value leaves scope. This returns null and does nothing in CLI mode.
 800          *
 801          * @return ScopedCallback|null
 802          */
 803         final protected function getScopedPHPBehaviorForOps() {
 804                 if ( php_sapi_name() != 'cli' ) { // http://bugs.php.net/bug.php?id=47540
 805                         $old = ignore_user_abort( true ); // avoid half-finished operations
 806                         return new ScopedCallback( function() use ( $old ) {
 807                                 ignore_user_abort( $old );
 808                         } );
 809                 }
 810                 return null;
 811         }
 812
 813         /**
 814          * Check if a file exists at a storage path in the backend.
 815          * This returns false if only a directory exists at the path.
 816          *
 817          * @param array $params
 818          * $params include:
 819          *   - src    : source storage path
 820          *   - latest : use the latest available data
 821          * @return bool|null Returns null on failure
 822          */
 823         abstract public function fileExists( array $params );
 824
 825         /**
 826          * Get the last-modified timestamp of the file at a storage path.
 827          *
 828          * @param array $params
 829          * $params include:
 830          *   - src    : source storage path
 831          *   - latest : use the latest available data
 832          * @return string|bool TS_MW timestamp or false on failure
 833          */
 834         abstract public function getFileTimestamp( array $params );
 835
 836         /**
 837          * Get the contents of a file at a storage path in the backend.
 838          * This should be avoided for potentially large files.
 839          *
 840          * @param array $params
 841          * $params include:
 842          *   - src    : source storage path
 843          *   - latest : use the latest available data
 844          * @return string|bool Returns false on failure
 845          */
 846         final public function getFileContents( array $params ) {
 847                 $contents = $this->getFileContentsMulti(
 848                         array( 'srcs' => array( $params['src'] ) ) + $params );
 849
 850                 return $contents[$params['src']];
 851         }
 852
 853         /**
 854          * Like getFileContents() except it takes an array of storage paths
 855          * and returns a map of storage paths to strings (or null on failure).
 856          * The map keys (paths) are in the same order as the provided list of paths.
 857          *
 858          * @see FileBackend::getFileContents()
 859          *
 860          * @param array $params
 861          * $params include:
 862          *   - srcs        : list of source storage paths
 863          *   - latest      : use the latest available data
 864          *   - parallelize : try to do operations in parallel when possible
 865          * @return Array Map of (path name => string or false on failure)
 866          * @since 1.20
 867          */
 868         abstract public function getFileContentsMulti( array $params );
 869
 870         /**
 871          * Get the size (bytes) of a file at a storage path in the backend.
 872          *
 873          * @param array $params
 874          * $params include:
 875          *   - src    : source storage path
 876          *   - latest : use the latest available data
 877          * @return integer|bool Returns false on failure
 878          */
 879         abstract public function getFileSize( array $params );
 880
 881         /**
 882          * Get quick information about a file at a storage path in the backend.
 883          * If the file does not exist, then this returns false.
 884          * Otherwise, the result is an associative array that includes:
 885          *   - mtime  : the last-modified timestamp (TS_MW)
 886          *   - size   : the file size (bytes)
 887          * Additional values may be included for internal use only.
 888          *
 889          * @param array $params
 890          * $params include:
 891          *   - src    : source storage path
 892          *   - latest : use the latest available data
 893          * @return Array|bool|null Returns null on failure
 894          */
 895         abstract public function getFileStat( array $params );
 896
 897         /**
 898          * Get a SHA-1 hash of the file at a storage path in the backend.
 899          *
 900          * @param array $params
 901          * $params include:
 902          *   - src    : source storage path
 903          *   - latest : use the latest available data
 904          * @return string|bool Hash string or false on failure
 905          */
 906         abstract public function getFileSha1Base36( array $params );
 907
 908         /**
 909          * Get the properties of the file at a storage path in the backend.
 910          * This gives the result of FSFile::getProps() on a local copy of the file.
 911          *
 912          * @param array $params
 913          * $params include:
 914          *   - src    : source storage path
 915          *   - latest : use the latest available data
 916          * @return Array Returns FSFile::placeholderProps() on failure
 917          */
 918         abstract public function getFileProps( array $params );
 919
 920         /**
 921          * Stream the file at a storage path in the backend.
 922          * If the file does not exists, an HTTP 404 error will be given.
 923          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
 924          * will be sent if streaming began, while none will be sent otherwise.
 925          * Implementations should flush the output buffer before sending data.
 926          *
 927          * @param array $params
 928          * $params include:
 929          *   - src     : source storage path
 930          *   - headers : list of additional HTTP headers to send on success
 931          *   - latest  : use the latest available data
 932          * @return Status
 933          */
 934         abstract public function streamFile( array $params );
 935
 936         /**
 937          * Returns a file system file, identical to the file at a storage path.
 938          * The file returned is either:
 939          *   - a) A local copy of the file at a storage path in the backend.
 940          *        The temporary copy will have the same extension as the source.
 941          *   - b) An original of the file at a storage path in the backend.
 942          * Temporary files may be purged when the file object falls out of scope.
 943          *
 944          * Write operations should *never* be done on this file as some backends
 945          * may do internal tracking or may be instances of FileBackendMultiWrite.
 946          * In that later case, there are copies of the file that must stay in sync.
 947          * Additionally, further calls to this function may return the same file.
 948          *
 949          * @param array $params
 950          * $params include:
 951          *   - src    : source storage path
 952          *   - latest : use the latest available data
 953          * @return FSFile|null Returns null on failure
 954          */
 955         final public function getLocalReference( array $params ) {
 956                 $fsFiles = $this->getLocalReferenceMulti(
 957                         array( 'srcs' => array( $params['src'] ) ) + $params );
 958
 959                 return $fsFiles[$params['src']];
 960         }
 961
 962         /**
 963          * Like getLocalReference() except it takes an array of storage paths
 964          * and returns a map of storage paths to FSFile objects (or null on failure).
 965          * The map keys (paths) are in the same order as the provided list of paths.
 966          *
 967          * @see FileBackend::getLocalReference()
 968          *
 969          * @param array $params
 970          * $params include:
 971          *   - srcs        : list of source storage paths
 972          *   - latest      : use the latest available data
 973          *   - parallelize : try to do operations in parallel when possible
 974          * @return Array Map of (path name => FSFile or null on failure)
 975          * @since 1.20
 976          */
 977         abstract public function getLocalReferenceMulti( array $params );
 978
 979         /**
 980          * Get a local copy on disk of the file at a storage path in the backend.
 981          * The temporary copy will have the same file extension as the source.
 982          * Temporary files may be purged when the file object falls out of scope.
 983          *
 984          * @param array $params
 985          * $params include:
 986          *   - src    : source storage path
 987          *   - latest : use the latest available data
 988          * @return TempFSFile|null Returns null on failure
 989          */
 990         final public function getLocalCopy( array $params ) {
 991                 $tmpFiles = $this->getLocalCopyMulti(
 992                         array( 'srcs' => array( $params['src'] ) ) + $params );
 993
 994                 return $tmpFiles[$params['src']];
 995         }
 996
 997         /**
 998          * Like getLocalCopy() except it takes an array of storage paths and
 999          * returns a map of storage paths to TempFSFile objects (or null on failure).
1000          * The map keys (paths) are in the same order as the provided list of paths.
1001          *
1002          * @see FileBackend::getLocalCopy()
1003          *
1004          * @param array $params
1005          * $params include:
1006          *   - srcs        : list of source storage paths
1007          *   - latest      : use the latest available data
1008          *   - parallelize : try to do operations in parallel when possible
1009          * @return Array Map of (path name => TempFSFile or null on failure)
1010          * @since 1.20
1011          */
1012         abstract public function getLocalCopyMulti( array $params );
1013
1014         /**
1015          * Return an HTTP URL to a given file that requires no authentication to use.
1016          * The URL may be pre-authenticated (via some token in the URL) and temporary.
1017          * This will return null if the backend cannot make an HTTP URL for the file.
1018          *
1019          * This is useful for key/value stores when using scripts that seek around
1020          * large files and those scripts (and the backend) support HTTP Range headers.
1021          * Otherwise, one would need to use getLocalReference(), which involves loading
1022          * the entire file on to local disk.
1023          *
1024          * @param array $params
1025          * $params include:
1026          *   - src : source storage path
1027          *   - ttl : lifetime (seconds) if pre-authenticated; default is 1 day
1028          * @return string|null
1029          * @since 1.21
1030          */
1031         abstract public function getFileHttpUrl( array $params );
1032
1033         /**
1034          * Check if a directory exists at a given storage path.
1035          * Backends using key/value stores will check if the path is a
1036          * virtual directory, meaning there are files under the given directory.
1037          *
1038          * Storage backends with eventual consistency might return stale data.
1039          *
1040          * @param $params array
1041          * $params include:
1042          *   - dir : storage directory
1043          * @return bool|null Returns null on failure
1044          * @since 1.20
1045          */
1046         abstract public function directoryExists( array $params );
1047
1048         /**
1049          * Get an iterator to list *all* directories under a storage directory.
1050          * If the directory is of the form "mwstore://backend/container",
1051          * then all directories in the container will be listed.
1052          * If the directory is of form "mwstore://backend/container/dir",
1053          * then all directories directly under that directory will be listed.
1054          * Results will be storage directories relative to the given directory.
1055          *
1056          * Storage backends with eventual consistency might return stale data.
1057          *
1058          * @param $params array
1059          * $params include:
1060          *   - dir     : storage directory
1061          *   - topOnly : only return direct child dirs of the directory
1062          * @return Traversable|Array|null Returns null on failure
1063          * @since 1.20
1064          */
1065         abstract public function getDirectoryList( array $params );
1066
1067         /**
1068          * Same as FileBackend::getDirectoryList() except only lists
1069          * directories that are immediately under the given directory.
1070          *
1071          * Storage backends with eventual consistency might return stale data.
1072          *
1073          * @param $params array
1074          * $params include:
1075          *   - dir : storage directory
1076          * @return Traversable|Array|null Returns null on failure
1077          * @since 1.20
1078          */
1079         final public function getTopDirectoryList( array $params ) {
1080                 return $this->getDirectoryList( array( 'topOnly' => true ) + $params );
1081         }
1082
1083         /**
1084          * Get an iterator to list *all* stored files under a storage directory.
1085          * If the directory is of the form "mwstore://backend/container",
1086          * then all files in the container will be listed.
1087          * If the directory is of form "mwstore://backend/container/dir",
1088          * then all files under that directory will be listed.
1089          * Results will be storage paths relative to the given directory.
1090          *
1091          * Storage backends with eventual consistency might return stale data.
1092          *
1093          * @param $params array
1094          * $params include:
1095          *   - dir     : storage directory
1096          *   - topOnly : only return direct child files of the directory (since 1.20)
1097          * @return Traversable|Array|null Returns null on failure
1098          */
1099         abstract public function getFileList( array $params );
1100
1101         /**
1102          * Same as FileBackend::getFileList() except only lists
1103          * files that are immediately under the given directory.
1104          *
1105          * Storage backends with eventual consistency might return stale data.
1106          *
1107          * @param $params array
1108          * $params include:
1109          *   - dir : storage directory
1110          * @return Traversable|Array|null Returns null on failure
1111          * @since 1.20
1112          */
1113         final public function getTopFileList( array $params ) {
1114                 return $this->getFileList( array( 'topOnly' => true ) + $params );
1115         }
1116
1117         /**
1118          * Preload persistent file stat and property cache into in-process cache.
1119          * This should be used when stat calls will be made on a known list of a many files.
1120          *
1121          * @param array $paths Storage paths
1122          * @return void
1123          */
1124         public function preloadCache( array $paths ) {}
1125
1126         /**
1127          * Invalidate any in-process file stat and property cache.
1128          * If $paths is given, then only the cache for those files will be cleared.
1129          *
1130          * @param array $paths Storage paths (optional)
1131          * @return void
1132          */
1133         public function clearCache( array $paths = null ) {}
1134
1135         /**
1136          * Lock the files at the given storage paths in the backend.
1137          * This will either lock all the files or none (on failure).
1138          *
1139          * Callers should consider using getScopedFileLocks() instead.
1140          *
1141          * @param array $paths Storage paths
1142          * @param $type integer LockManager::LOCK_* constant
1143          * @return Status
1144          */
1145         final public function lockFiles( array $paths, $type ) {
1146                 return $this->lockManager->lock( $paths, $type );
1147         }
1148
1149         /**
1150          * Unlock the files at the given storage paths in the backend.
1151          *
1152          * @param array $paths Storage paths
1153          * @param $type integer LockManager::LOCK_* constant
1154          * @return Status
1155          */
1156         final public function unlockFiles( array $paths, $type ) {
1157                 return $this->lockManager->unlock( $paths, $type );
1158         }
1159
1160         /**
1161          * Lock the files at the given storage paths in the backend.
1162          * This will either lock all the files or none (on failure).
1163          * On failure, the status object will be updated with errors.
1164          *
1165          * Once the return value goes out scope, the locks will be released and
1166          * the status updated. Unlock fatals will not change the status "OK" value.
1167          *
1168          * @param array $paths Storage paths
1169          * @param $type integer LockManager::LOCK_* constant
1170          * @param $status Status Status to update on lock/unlock
1171          * @return ScopedLock|null Returns null on failure
1172          */
1173         final public function getScopedFileLocks( array $paths, $type, Status $status ) {
1174                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status );
1175         }
1176
1177         /**
1178          * Get an array of scoped locks needed for a batch of file operations.
1179          *
1180          * Normally, FileBackend::doOperations() handles locking, unless
1181          * the 'nonLocking' param is passed in. This function is useful if you
1182          * want the files to be locked for a broader scope than just when the
1183          * files are changing. For example, if you need to update DB metadata,
1184          * you may want to keep the files locked until finished.
1185          *
1186          * @see FileBackend::doOperations()
1187          *
1188          * @param array $ops List of file operations to FileBackend::doOperations()
1189          * @param $status Status Status to update on lock/unlock
1190          * @return Array List of ScopedFileLocks or null values
1191          * @since 1.20
1192          */
1193         abstract public function getScopedLocksForOps( array $ops, Status $status );
1194
1195         /**
1196          * Get the root storage path of this backend.
1197          * All container paths are "subdirectories" of this path.
1198          *
1199          * @return string Storage path
1200          * @since 1.20
1201          */
1202         final public function getRootStoragePath() {
1203                 return "mwstore://{$this->name}";
1204         }
1205
1206         /**
1207          * Get the storage path for the given container for this backend
1208          *
1209          * @param string $container Container name
1210          * @return string Storage path
1211          * @since 1.21
1212          */
1213         final public function getContainerStoragePath( $container ) {
1214                 return $this->getRootStoragePath() . "/{$container}";
1215         }
1216
1217         /**
1218          * Get the file journal object for this backend
1219          *
1220          * @return FileJournal
1221          */
1222         final public function getJournal() {
1223                 return $this->fileJournal;
1224         }
1225
1226         /**
1227          * Check if a given path is a "mwstore://" path.
1228          * This does not do any further validation or any existence checks.
1229          *
1230          * @param $path string
1231          * @return bool
1232          */
1233         final public static function isStoragePath( $path ) {
1234                 return ( strpos( $path, 'mwstore://' ) === 0 );
1235         }
1236
1237         /**
1238          * Split a storage path into a backend name, a container name,
1239          * and a relative file path. The relative path may be the empty string.
1240          * This does not do any path normalization or traversal checks.
1241          *
1242          * @param $storagePath string
1243          * @return Array (backend, container, rel object) or (null, null, null)
1244          */
1245         final public static function splitStoragePath( $storagePath ) {
1246                 if ( self::isStoragePath( $storagePath ) ) {
1247                         // Remove the "mwstore://" prefix and split the path
1248                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
1249                         if ( count( $parts ) >= 2 && $parts[0] != '' && $parts[1] != '' ) {
1250                                 if ( count( $parts ) == 3 ) {
1251                                         return $parts; // e.g. "backend/container/path"
1252                                 } else {
1253                                         return array( $parts[0], $parts[1], '' ); // e.g. "backend/container"
1254                                 }
1255                         }
1256                 }
1257                 return array( null, null, null );
1258         }
1259
1260         /**
1261          * Normalize a storage path by cleaning up directory separators.
1262          * Returns null if the path is not of the format of a valid storage path.
1263          *
1264          * @param $storagePath string
1265          * @return string|null
1266          */
1267         final public static function normalizeStoragePath( $storagePath ) {
1268                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
1269                 if ( $relPath !== null ) { // must be for this backend
1270                         $relPath = self::normalizeContainerPath( $relPath );
1271                         if ( $relPath !== null ) {
1272                                 return ( $relPath != '' )
1273                                         ? "mwstore://{$backend}/{$container}/{$relPath}"
1274                                         : "mwstore://{$backend}/{$container}";
1275                         }
1276                 }
1277                 return null;
1278         }
1279
1280         /**
1281          * Get the parent storage directory of a storage path.
1282          * This returns a path like "mwstore://backend/container",
1283          * "mwstore://backend/container/...", or null if there is no parent.
1284          *
1285          * @param $storagePath string
1286          * @return string|null
1287          */
1288         final public static function parentStoragePath( $storagePath ) {
1289                 $storagePath = dirname( $storagePath );
1290                 list( , , $rel ) = self::splitStoragePath( $storagePath );
1291                 return ( $rel === null ) ? null : $storagePath;
1292         }
1293
1294         /**
1295          * Get the final extension from a storage or FS path
1296          *
1297          * @param $path string
1298          * @return string
1299          */
1300         final public static function extensionFromPath( $path ) {
1301                 $i = strrpos( $path, '.' );
1302                 return strtolower( $i ? substr( $path, $i + 1 ) : '' );
1303         }
1304
1305         /**
1306          * Check if a relative path has no directory traversals
1307          *
1308          * @param $path string
1309          * @return bool
1310          * @since 1.20
1311          */
1312         final public static function isPathTraversalFree( $path ) {
1313                 return ( self::normalizeContainerPath( $path ) !== null );
1314         }
1315
1316         /**
1317          * Build a Content-Disposition header value per RFC 6266.
1318          *
1319          * @param string $type One of (attachment, inline)
1320          * @param string $filename Suggested file name (should not contain slashes)
1321          * @throws MWException
1322          * @return string
1323          * @since 1.20
1324          */
1325         final public static function makeContentDisposition( $type, $filename = '' ) {
1326                 $parts = array();
1327
1328                 $type = strtolower( $type );
1329                 if ( !in_array( $type, array( 'inline', 'attachment' ) ) ) {
1330                         throw new MWException( "Invalid Content-Disposition type '$type'." );
1331                 }
1332                 $parts[] = $type;
1333
1334                 if ( strlen( $filename ) ) {
1335                         $parts[] = "filename*=UTF-8''" . rawurlencode( basename( $filename ) );
1336                 }
1337
1338                 return implode( ';', $parts );
1339         }
1340
1341         /**
1342          * Validate and normalize a relative storage path.
1343          * Null is returned if the path involves directory traversal.
1344          * Traversal is insecure for FS backends and broken for others.
1345          *
1346          * This uses the same traversal protection as Title::secureAndSplit().
1347          *
1348          * @param string $path Storage path relative to a container
1349          * @return string|null
1350          */
1351         final protected static function normalizeContainerPath( $path ) {
1352                 // Normalize directory separators
1353                 $path = strtr( $path, '\\', '/' );
1354                 // Collapse any consecutive directory separators
1355                 $path = preg_replace( '![/]{2,}!', '/', $path );
1356                 // Remove any leading directory separator
1357                 $path = ltrim( $path, '/' );
1358                 // Use the same traversal protection as Title::secureAndSplit()
1359                 if ( strpos( $path, '.' ) !== false ) {
1360                         if (
1361                                 $path === '.' ||
1362                                 $path === '..' ||
1363                                 strpos( $path, './' ) === 0 ||
1364                                 strpos( $path, '../' ) === 0 ||
1365                                 strpos( $path, '/./' ) !== false ||
1366                                 strpos( $path, '/../' ) !== false
1367                         ) {
1368                                 return null;
1369                         }
1370                 }
1371                 return $path;
1372         }
1373 }