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          *         'disposition'         => <Content-Disposition header value>,
 195          *         'headers'             => <HTTP header name/value map> # since 1.21
 196          *     );
 197          * @endcode
 198          *
 199          * b) Copy a file system file into storage
 200          * @code
 201          *     array(
 202          *         'op'                  => 'store',
 203          *         'src'                 => <file system path>,
 204          *         'dst'                 => <storage path>,
 205          *         'overwrite'           => <boolean>,
 206          *         'overwriteSame'       => <boolean>,
 207          *         'disposition'         => <Content-Disposition header value>,
 208          *         'headers'             => <HTTP header name/value map> # since 1.21
 209          *     )
 210          * @endcode
 211          *
 212          * c) Copy a file within storage
 213          * @code
 214          *     array(
 215          *         'op'                  => 'copy',
 216          *         'src'                 => <storage path>,
 217          *         'dst'                 => <storage path>,
 218          *         'overwrite'           => <boolean>,
 219          *         'overwriteSame'       => <boolean>,
 220          *         'ignoreMissingSource' => <boolean>, # since 1.21
 221          *         'disposition'         => <Content-Disposition header value>
 222          *     )
 223          * @endcode
 224          *
 225          * d) Move a file within storage
 226          * @code
 227          *     array(
 228          *         'op'                  => 'move',
 229          *         'src'                 => <storage path>,
 230          *         'dst'                 => <storage path>,
 231          *         'overwrite'           => <boolean>,
 232          *         'overwriteSame'       => <boolean>,
 233          *         'ignoreMissingSource' => <boolean>, # since 1.21
 234          *         'disposition'         => <Content-Disposition header value>
 235          *     )
 236          * @endcode
 237          *
 238          * e) Delete a file within storage
 239          * @code
 240          *     array(
 241          *         'op'                  => 'delete',
 242          *         'src'                 => <storage path>,
 243          *         'ignoreMissingSource' => <boolean>
 244          *     )
 245          * @endcode
 246          *
 247          * f) Update metadata for a file within storage
 248          * @code
 249          *     array(
 250          *         'op'                  => 'describe',
 251          *         'src'                 => <storage path>,
 252          *         'disposition'         => <Content-Disposition header value>,
 253          *         'headers'             => <HTTP header name/value map>
 254          *     )
 255          * @endcode
 256          *
 257          * g) Do nothing (no-op)
 258          * @code
 259          *     array(
 260          *         'op'                  => 'null',
 261          *     )
 262          * @endcode
 263          *
 264          * Boolean flags for operations (operation-specific):
 265          *   - ignoreMissingSource : The operation will simply succeed and do
 266          *                           nothing if the source file does not exist.
 267          *   - overwrite           : Any destination file will be overwritten.
 268          *   - overwriteSame       : An error will not be given if a file already
 269          *                           exists at the destination that has the same
 270          *                           contents as the new contents to be written there.
 271          *   - disposition         : If supplied, the backend will return a Content-Disposition
 272          *                           header when GETs/HEADs of the destination file are made.
 273          *                           Backends that don't support metadata ignore this.
 274          *                           See http://tools.ietf.org/html/rfc6266. (since 1.20)
 275          *   - headers             : If supplied, the backend will return these headers when
 276          *                           GETs/HEADs of the destination file are made. Header values
 277          *                           should be smaller than 256 bytes, often options or numbers.
 278          *                           Existing headers will remain, but these will replace any
 279          *                           conflicting previous headers, and headers will be removed
 280          *                           if they are set to an empty string.
 281          *                           Backends that don't support metadata ignore this. (since 1.21)
 282          *
 283          * $opts is an associative of boolean flags, including:
 284          *   - force               : Operation precondition errors no longer trigger an abort.
 285          *                           Any remaining operations are still attempted. Unexpected
 286          *                           failures may still cause remaining operations to be aborted.
 287          *   - nonLocking          : No locks are acquired for the operations.
 288          *                           This can increase performance for non-critical writes.
 289          *                           This has no effect unless the 'force' flag is set.
 290          *   - nonJournaled        : Don't log this operation batch in the file journal.
 291          *                           This limits the ability of recovery scripts.
 292          *   - parallelize         : Try to do operations in parallel when possible.
 293          *   - bypassReadOnly      : Allow writes in read-only mode. (since 1.20)
 294          *   - preserveCache       : Don't clear the process cache before checking files.
 295          *                           This should only be used if all entries in the process
 296          *                           cache were added after the files were already locked. (since 1.20)
 297          *
 298          * @remarks Remarks on locking:
 299          * File system paths given to operations should refer to files that are
 300          * already locked or otherwise safe from modification from other processes.
 301          * Normally these files will be new temp files, which should be adequate.
 302          *
 303          * @par Return value:
 304          *
 305          * This returns a Status, which contains all warnings and fatals that occurred
 306          * during the operation. The 'failCount', 'successCount', and 'success' members
 307          * will reflect each operation attempted.
 308          *
 309          * The status will be "OK" unless:
 310          *   - a) unexpected operation errors occurred (network partitions, disk full...)
 311          *   - b) significant operation errors occurred and 'force' was not set
 312          *
 313          * @param $ops Array List of operations to execute in order
 314          * @param $opts Array Batch operation options
 315          * @return Status
 316          */
 317         final public function doOperations( array $ops, array $opts = array() ) {
 318                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 319                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 320                 }
 321                 if ( empty( $opts['force'] ) ) { // sanity
 322                         unset( $opts['nonLocking'] );
 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 $op Array Operation
 341          * @param $opts Array 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 $params Array Operation parameters
 355          * @param $opts Array 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 $params Array Operation parameters
 369          * @param $opts Array 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 $params Array Operation parameters
 383          * @param $opts Array 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 $params Array Operation parameters
 397          * @param $opts Array 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 $params Array Operation parameters
 411          * @param $opts Array 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 $params Array Operation parameters
 425          * @param $opts Array 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          *         'disposition'         => <Content-Disposition header value>,
 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          *         'disposition'         => <Content-Disposition header value>,
 467          *         'headers'             => <HTTP header name/value map> # since 1.21
 468          *     )
 469          * @endcode
 470          *
 471          * c) Copy a file within storage
 472          * @code
 473          *     array(
 474          *         'op'                  => 'copy',
 475          *         'src'                 => <storage path>,
 476          *         'dst'                 => <storage path>,
 477          *         'ignoreMissingSource' => <boolean>, # since 1.21
 478          *         'disposition'         => <Content-Disposition header value>
 479          *     )
 480          * @endcode
 481          *
 482          * d) Move a file within storage
 483          * @code
 484          *     array(
 485          *         'op'                  => 'move',
 486          *         'src'                 => <storage path>,
 487          *         'dst'                 => <storage path>,
 488          *         'ignoreMissingSource' => <boolean>, # since 1.21
 489          *         'disposition'         => <Content-Disposition header value>
 490          *     )
 491          * @endcode
 492          *
 493          * e) Delete a file within storage
 494          * @code
 495          *     array(
 496          *         'op'                  => 'delete',
 497          *         'src'                 => <storage path>,
 498          *         'ignoreMissingSource' => <boolean>
 499          *     )
 500          * @endcode
 501          *
 502          * f) Update metadata for a file within storage
 503          * @code
 504          *     array(
 505          *         'op'                  => 'describe',
 506          *         'src'                 => <storage path>,
 507          *         'disposition'         => <Content-Disposition header value>,
 508          *         'headers'             => <HTTP header name/value map>
 509          *     )
 510          * @endcode
 511          *
 512          * g) Do nothing (no-op)
 513          * @code
 514          *     array(
 515          *         'op'                  => 'null',
 516          *     )
 517          * @endcode
 518          *
 519          * @par Boolean flags for operations (operation-specific):
 520          *   - ignoreMissingSource : The operation will simply succeed and do
 521          *                           nothing if the source file does not exist.
 522          *   - disposition         : When supplied, the backend will add a Content-Disposition
 523          *                           header when GETs/HEADs of the destination file are made.
 524          *                           Backends that don't support file metadata will ignore this.
 525          *                           See http://tools.ietf.org/html/rfc6266 (since 1.20).
 526          *   - headers             : If supplied with a header name/value map, the backend will
 527          *                           reply with these headers when GETs/HEADs of the destination
 528          *                           file are made. Header values should be smaller than 256 bytes.
 529          *                           Existing headers will remain, but these will replace any
 530          *                           conflicting previous headers, and headers will be removed
 531          *                           if they are set to an empty string.
 532          *                           Backends that don't support metadata ignore this. (since 1.21)
 533          *
 534          * $opts is an associative of boolean flags, including:
 535          *   - bypassReadOnly      : Allow writes in read-only mode (since 1.20)
 536          *
 537          * @par Return value:
 538          * This returns a Status, which contains all warnings and fatals that occurred
 539          * during the operation. The 'failCount', 'successCount', and 'success' members
 540          * will reflect each operation attempted for the given files. The status will be
 541          * considered "OK" as long as no fatal errors occurred.
 542          *
 543          * @param $ops Array Set of operations to execute
 544          * @param $opts Array Batch operation options
 545          * @return Status
 546          * @since 1.20
 547          */
 548         final public function doQuickOperations( array $ops, array $opts = array() ) {
 549                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 550                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 551                 }
 552                 foreach ( $ops as &$op ) {
 553                         $op['overwrite'] = true; // avoids RTTs in key/value stores
 554                 }
 555                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 556                 return $this->doQuickOperationsInternal( $ops );
 557         }
 558
 559         /**
 560          * @see FileBackend::doQuickOperations()
 561          * @since 1.20
 562          */
 563         abstract protected function doQuickOperationsInternal( array $ops );
 564
 565         /**
 566          * Same as doQuickOperations() except it takes a single operation.
 567          * If you are doing a batch of operations, then use that function instead.
 568          *
 569          * @see FileBackend::doQuickOperations()
 570          *
 571          * @param $op Array Operation
 572          * @return Status
 573          * @since 1.20
 574          */
 575         final public function doQuickOperation( array $op ) {
 576                 return $this->doQuickOperations( array( $op ) );
 577         }
 578
 579         /**
 580          * Performs a single quick create operation.
 581          * This sets $params['op'] to 'create' and passes it to doQuickOperation().
 582          *
 583          * @see FileBackend::doQuickOperation()
 584          *
 585          * @param $params Array Operation parameters
 586          * @return Status
 587          * @since 1.20
 588          */
 589         final public function quickCreate( array $params ) {
 590                 return $this->doQuickOperation( array( 'op' => 'create' ) + $params );
 591         }
 592
 593         /**
 594          * Performs a single quick store operation.
 595          * This sets $params['op'] to 'store' and passes it to doQuickOperation().
 596          *
 597          * @see FileBackend::doQuickOperation()
 598          *
 599          * @param $params Array Operation parameters
 600          * @return Status
 601          * @since 1.20
 602          */
 603         final public function quickStore( array $params ) {
 604                 return $this->doQuickOperation( array( 'op' => 'store' ) + $params );
 605         }
 606
 607         /**
 608          * Performs a single quick copy operation.
 609          * This sets $params['op'] to 'copy' and passes it to doQuickOperation().
 610          *
 611          * @see FileBackend::doQuickOperation()
 612          *
 613          * @param $params Array Operation parameters
 614          * @return Status
 615          * @since 1.20
 616          */
 617         final public function quickCopy( array $params ) {
 618                 return $this->doQuickOperation( array( 'op' => 'copy' ) + $params );
 619         }
 620
 621         /**
 622          * Performs a single quick move operation.
 623          * This sets $params['op'] to 'move' and passes it to doQuickOperation().
 624          *
 625          * @see FileBackend::doQuickOperation()
 626          *
 627          * @param $params Array Operation parameters
 628          * @return Status
 629          * @since 1.20
 630          */
 631         final public function quickMove( array $params ) {
 632                 return $this->doQuickOperation( array( 'op' => 'move' ) + $params );
 633         }
 634
 635         /**
 636          * Performs a single quick delete operation.
 637          * This sets $params['op'] to 'delete' and passes it to doQuickOperation().
 638          *
 639          * @see FileBackend::doQuickOperation()
 640          *
 641          * @param $params Array Operation parameters
 642          * @return Status
 643          * @since 1.20
 644          */
 645         final public function quickDelete( array $params ) {
 646                 return $this->doQuickOperation( array( 'op' => 'delete' ) + $params );
 647         }
 648
 649         /**
 650          * Performs a single quick describe operation.
 651          * This sets $params['op'] to 'describe' and passes it to doQuickOperation().
 652          *
 653          * @see FileBackend::doQuickOperation()
 654          *
 655          * @param $params Array Operation parameters
 656          * @return Status
 657          * @since 1.21
 658          */
 659         final public function quickDescribe( array $params ) {
 660                 return $this->doQuickOperation( array( 'op' => 'describe' ) + $params );
 661         }
 662
 663         /**
 664          * Concatenate a list of storage files into a single file system file.
 665          * The target path should refer to a file that is already locked or
 666          * otherwise safe from modification from other processes. Normally,
 667          * the file will be a new temp file, which should be adequate.
 668          *
 669          * @param $params Array Operation parameters
 670          * $params include:
 671          *   - srcs        : ordered source storage paths (e.g. chunk1, chunk2, ...)
 672          *   - dst         : file system path to 0-byte temp file
 673          *   - parallelize : try to do operations in parallel when possible
 674          * @return Status
 675          */
 676         abstract public function concatenate( array $params );
 677
 678         /**
 679          * Prepare a storage directory for usage.
 680          * This will create any required containers and parent directories.
 681          * Backends using key/value stores only need to create the container.
 682          *
 683          * The 'noAccess' and 'noListing' parameters works the same as in secure(),
 684          * except they are only applied *if* the directory/container had to be created.
 685          * These flags should always be set for directories that have private files.
 686          *
 687          * @param $params Array
 688          * $params include:
 689          *   - dir            : storage directory
 690          *   - noAccess       : try to deny file access (since 1.20)
 691          *   - noListing      : try to deny file listing (since 1.20)
 692          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 693          * @return Status
 694          */
 695         final public function prepare( array $params ) {
 696                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 697                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 698                 }
 699                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 700                 return $this->doPrepare( $params );
 701         }
 702
 703         /**
 704          * @see FileBackend::prepare()
 705          */
 706         abstract protected function doPrepare( array $params );
 707
 708         /**
 709          * Take measures to block web access to a storage directory and
 710          * the container it belongs to. FS backends might add .htaccess
 711          * files whereas key/value store backends might revoke container
 712          * access to the storage user representing end-users in web requests.
 713          * This is not guaranteed to actually do anything.
 714          *
 715          * @param $params Array
 716          * $params include:
 717          *   - dir            : storage directory
 718          *   - noAccess       : try to deny file access
 719          *   - noListing      : try to deny file listing
 720          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 721          * @return Status
 722          */
 723         final public function secure( array $params ) {
 724                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 725                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 726                 }
 727                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 728                 return $this->doSecure( $params );
 729         }
 730
 731         /**
 732          * @see FileBackend::secure()
 733          */
 734         abstract protected function doSecure( array $params );
 735
 736         /**
 737          * Remove measures to block web access to a storage directory and
 738          * the container it belongs to. FS backends might remove .htaccess
 739          * files whereas key/value store backends might grant container
 740          * access to the storage user representing end-users in web requests.
 741          * This essentially can undo the result of secure() calls.
 742          *
 743          * @param $params Array
 744          * $params include:
 745          *   - dir            : storage directory
 746          *   - access         : try to allow file access
 747          *   - listing        : try to allow file listing
 748          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 749          * @return Status
 750          * @since 1.20
 751          */
 752         final public function publish( array $params ) {
 753                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 754                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 755                 }
 756                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 757                 return $this->doPublish( $params );
 758         }
 759
 760         /**
 761          * @see FileBackend::publish()
 762          */
 763         abstract protected function doPublish( array $params );
 764
 765         /**
 766          * Delete a storage directory if it is empty.
 767          * Backends using key/value stores may do nothing unless the directory
 768          * is that of an empty container, in which case it will be deleted.
 769          *
 770          * @param $params Array
 771          * $params include:
 772          *   - dir            : storage directory
 773          *   - recursive      : recursively delete empty subdirectories first (since 1.20)
 774          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 775          * @return Status
 776          */
 777         final public function clean( array $params ) {
 778                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 779                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 780                 }
 781                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 782                 return $this->doClean( $params );
 783         }
 784
 785         /**
 786          * @see FileBackend::clean()
 787          */
 788         abstract protected function doClean( array $params );
 789
 790         /**
 791          * Enter file operation scope.
 792          * This just makes PHP ignore user aborts/disconnects until the return
 793          * value leaves scope. This returns null and does nothing in CLI mode.
 794          *
 795          * @return ScopedCallback|null
 796          */
 797         final protected function getScopedPHPBehaviorForOps() {
 798                 if ( php_sapi_name() != 'cli' ) { // http://bugs.php.net/bug.php?id=47540
 799                         $old = ignore_user_abort( true ); // avoid half-finished operations
 800                         return new ScopedCallback( function() use ( $old ) { ignore_user_abort( $old ); } );
 801                 }
 802                 return null;
 803         }
 804
 805         /**
 806          * Check if a file exists at a storage path in the backend.
 807          * This returns false if only a directory exists at the path.
 808          *
 809          * @param $params Array
 810          * $params include:
 811          *   - src    : source storage path
 812          *   - latest : use the latest available data
 813          * @return bool|null Returns null on failure
 814          */
 815         abstract public function fileExists( array $params );
 816
 817         /**
 818          * Get the last-modified timestamp of the file at a storage path.
 819          *
 820          * @param $params Array
 821          * $params include:
 822          *   - src    : source storage path
 823          *   - latest : use the latest available data
 824          * @return string|bool TS_MW timestamp or false on failure
 825          */
 826         abstract public function getFileTimestamp( array $params );
 827
 828         /**
 829          * Get the contents of a file at a storage path in the backend.
 830          * This should be avoided for potentially large files.
 831          *
 832          * @param $params Array
 833          * $params include:
 834          *   - src    : source storage path
 835          *   - latest : use the latest available data
 836          * @return string|bool Returns false on failure
 837          */
 838         final public function getFileContents( array $params ) {
 839                 $contents = $this->getFileContentsMulti(
 840                         array( 'srcs' => array( $params['src'] ) ) + $params );
 841
 842                 return $contents[$params['src']];
 843         }
 844
 845         /**
 846          * Like getFileContents() except it takes an array of storage paths
 847          * and returns a map of storage paths to strings (or null on failure).
 848          * The map keys (paths) are in the same order as the provided list of paths.
 849          *
 850          * @see FileBackend::getFileContents()
 851          *
 852          * @param $params Array
 853          * $params include:
 854          *   - srcs        : list of source storage paths
 855          *   - latest      : use the latest available data
 856          *   - parallelize : try to do operations in parallel when possible
 857          * @return Array Map of (path name => string or false on failure)
 858          * @since 1.20
 859          */
 860         abstract public function getFileContentsMulti( array $params );
 861
 862         /**
 863          * Get the size (bytes) of a file at a storage path in the backend.
 864          *
 865          * @param $params Array
 866          * $params include:
 867          *   - src    : source storage path
 868          *   - latest : use the latest available data
 869          * @return integer|bool Returns false on failure
 870          */
 871         abstract public function getFileSize( array $params );
 872
 873         /**
 874          * Get quick information about a file at a storage path in the backend.
 875          * If the file does not exist, then this returns false.
 876          * Otherwise, the result is an associative array that includes:
 877          *   - mtime  : the last-modified timestamp (TS_MW)
 878          *   - size   : the file size (bytes)
 879          * Additional values may be included for internal use only.
 880          *
 881          * @param $params Array
 882          * $params include:
 883          *   - src    : source storage path
 884          *   - latest : use the latest available data
 885          * @return Array|bool|null Returns null on failure
 886          */
 887         abstract public function getFileStat( array $params );
 888
 889         /**
 890          * Get a SHA-1 hash of the file at a storage path in the backend.
 891          *
 892          * @param $params Array
 893          * $params include:
 894          *   - src    : source storage path
 895          *   - latest : use the latest available data
 896          * @return string|bool Hash string or false on failure
 897          */
 898         abstract public function getFileSha1Base36( array $params );
 899
 900         /**
 901          * Get the properties of the file at a storage path in the backend.
 902          * This gives the result of FSFile::getProps() on a local copy of the file.
 903          *
 904          * @param $params Array
 905          * $params include:
 906          *   - src    : source storage path
 907          *   - latest : use the latest available data
 908          * @return Array Returns FSFile::placeholderProps() on failure
 909          */
 910         abstract public function getFileProps( array $params );
 911
 912         /**
 913          * Stream the file at a storage path in the backend.
 914          * If the file does not exists, an HTTP 404 error will be given.
 915          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
 916          * will be sent if streaming began, while none will be sent otherwise.
 917          * Implementations should flush the output buffer before sending data.
 918          *
 919          * @param $params Array
 920          * $params include:
 921          *   - src     : source storage path
 922          *   - headers : list of additional HTTP headers to send on success
 923          *   - latest  : use the latest available data
 924          * @return Status
 925          */
 926         abstract public function streamFile( array $params );
 927
 928         /**
 929          * Returns a file system file, identical to the file at a storage path.
 930          * The file returned is either:
 931          *   - a) A local copy of the file at a storage path in the backend.
 932          *        The temporary copy will have the same extension as the source.
 933          *   - b) An original of the file at a storage path in the backend.
 934          * Temporary files may be purged when the file object falls out of scope.
 935          *
 936          * Write operations should *never* be done on this file as some backends
 937          * may do internal tracking or may be instances of FileBackendMultiWrite.
 938          * In that later case, there are copies of the file that must stay in sync.
 939          * Additionally, further calls to this function may return the same file.
 940          *
 941          * @param $params Array
 942          * $params include:
 943          *   - src    : source storage path
 944          *   - latest : use the latest available data
 945          * @return FSFile|null Returns null on failure
 946          */
 947         final public function getLocalReference( array $params ) {
 948                 $fsFiles = $this->getLocalReferenceMulti(
 949                         array( 'srcs' => array( $params['src'] ) ) + $params );
 950
 951                 return $fsFiles[$params['src']];
 952         }
 953
 954         /**
 955          * Like getLocalReference() except it takes an array of storage paths
 956          * and returns a map of storage paths to FSFile objects (or null on failure).
 957          * The map keys (paths) are in the same order as the provided list of paths.
 958          *
 959          * @see FileBackend::getLocalReference()
 960          *
 961          * @param $params Array
 962          * $params include:
 963          *   - srcs        : list of source storage paths
 964          *   - latest      : use the latest available data
 965          *   - parallelize : try to do operations in parallel when possible
 966          * @return Array Map of (path name => FSFile or null on failure)
 967          * @since 1.20
 968          */
 969         abstract public function getLocalReferenceMulti( array $params );
 970
 971         /**
 972          * Get a local copy on disk of the file at a storage path in the backend.
 973          * The temporary copy will have the same file extension as the source.
 974          * Temporary files may be purged when the file object falls out of scope.
 975          *
 976          * @param $params Array
 977          * $params include:
 978          *   - src    : source storage path
 979          *   - latest : use the latest available data
 980          * @return TempFSFile|null Returns null on failure
 981          */
 982         final public function getLocalCopy( array $params ) {
 983                 $tmpFiles = $this->getLocalCopyMulti(
 984                         array( 'srcs' => array( $params['src'] ) ) + $params );
 985
 986                 return $tmpFiles[$params['src']];
 987         }
 988
 989         /**
 990          * Like getLocalCopy() except it takes an array of storage paths and
 991          * returns a map of storage paths to TempFSFile objects (or null on failure).
 992          * The map keys (paths) are in the same order as the provided list of paths.
 993          *
 994          * @see FileBackend::getLocalCopy()
 995          *
 996          * @param $params Array
 997          * $params include:
 998          *   - srcs        : list of source storage paths
 999          *   - latest      : use the latest available data
1000          *   - parallelize : try to do operations in parallel when possible
1001          * @return Array Map of (path name => TempFSFile or null on failure)
1002          * @since 1.20
1003          */
1004         abstract public function getLocalCopyMulti( array $params );
1005
1006         /**
1007          * Return an HTTP URL to a given file that requires no authentication to use.
1008          * The URL may be pre-authenticated (via some token in the URL) and temporary.
1009          * This will return null if the backend cannot make an HTTP URL for the file.
1010          *
1011          * This is useful for key/value stores when using scripts that seek around
1012          * large files and those scripts (and the backend) support HTTP Range headers.
1013          * Otherwise, one would need to use getLocalReference(), which involves loading
1014          * the entire file on to local disk.
1015          *
1016          * @param $params Array
1017          * $params include:
1018          *   - src : source storage path
1019          *   - ttl : lifetime (seconds) if pre-authenticated; default is 1 day
1020          * @return string|null
1021          * @since 1.21
1022          */
1023         abstract public function getFileHttpUrl( array $params );
1024
1025         /**
1026          * Check if a directory exists at a given storage path.
1027          * Backends using key/value stores will check if the path is a
1028          * virtual directory, meaning there are files under the given directory.
1029          *
1030          * Storage backends with eventual consistency might return stale data.
1031          *
1032          * @param $params array
1033          * $params include:
1034          *   - dir : storage directory
1035          * @return bool|null Returns null on failure
1036          * @since 1.20
1037          */
1038         abstract public function directoryExists( array $params );
1039
1040         /**
1041          * Get an iterator to list *all* directories under a storage directory.
1042          * If the directory is of the form "mwstore://backend/container",
1043          * then all directories in the container will be listed.
1044          * If the directory is of form "mwstore://backend/container/dir",
1045          * then all directories directly under that directory will be listed.
1046          * Results will be storage directories relative to the given directory.
1047          *
1048          * Storage backends with eventual consistency might return stale data.
1049          *
1050          * @param $params array
1051          * $params include:
1052          *   - dir     : storage directory
1053          *   - topOnly : only return direct child dirs of the directory
1054          * @return Traversable|Array|null Returns null on failure
1055          * @since 1.20
1056          */
1057         abstract public function getDirectoryList( array $params );
1058
1059         /**
1060          * Same as FileBackend::getDirectoryList() except only lists
1061          * directories that are immediately under the given directory.
1062          *
1063          * Storage backends with eventual consistency might return stale data.
1064          *
1065          * @param $params array
1066          * $params include:
1067          *   - dir : storage directory
1068          * @return Traversable|Array|null Returns null on failure
1069          * @since 1.20
1070          */
1071         final public function getTopDirectoryList( array $params ) {
1072                 return $this->getDirectoryList( array( 'topOnly' => true ) + $params );
1073         }
1074
1075         /**
1076          * Get an iterator to list *all* stored files under a storage directory.
1077          * If the directory is of the form "mwstore://backend/container",
1078          * then all files in the container will be listed.
1079          * If the directory is of form "mwstore://backend/container/dir",
1080          * then all files under that directory will be listed.
1081          * Results will be storage paths relative to the given directory.
1082          *
1083          * Storage backends with eventual consistency might return stale data.
1084          *
1085          * @param $params array
1086          * $params include:
1087          *   - dir     : storage directory
1088          *   - topOnly : only return direct child files of the directory (since 1.20)
1089          * @return Traversable|Array|null Returns null on failure
1090          */
1091         abstract public function getFileList( array $params );
1092
1093         /**
1094          * Same as FileBackend::getFileList() except only lists
1095          * files that are immediately under the given directory.
1096          *
1097          * Storage backends with eventual consistency might return stale data.
1098          *
1099          * @param $params array
1100          * $params include:
1101          *   - dir : storage directory
1102          * @return Traversable|Array|null Returns null on failure
1103          * @since 1.20
1104          */
1105         final public function getTopFileList( array $params ) {
1106                 return $this->getFileList( array( 'topOnly' => true ) + $params );
1107         }
1108
1109         /**
1110          * Preload persistent file stat and property cache into in-process cache.
1111          * This should be used when stat calls will be made on a known list of a many files.
1112          *
1113          * @param $paths Array Storage paths
1114          * @return void
1115          */
1116         public function preloadCache( array $paths ) {}
1117
1118         /**
1119          * Invalidate any in-process file stat and property cache.
1120          * If $paths is given, then only the cache for those files will be cleared.
1121          *
1122          * @param $paths Array Storage paths (optional)
1123          * @return void
1124          */
1125         public function clearCache( array $paths = null ) {}
1126
1127         /**
1128          * Lock the files at the given storage paths in the backend.
1129          * This will either lock all the files or none (on failure).
1130          *
1131          * Callers should consider using getScopedFileLocks() instead.
1132          *
1133          * @param $paths Array Storage paths
1134          * @param $type integer LockManager::LOCK_* constant
1135          * @return Status
1136          */
1137         final public function lockFiles( array $paths, $type ) {
1138                 return $this->lockManager->lock( $paths, $type );
1139         }
1140
1141         /**
1142          * Unlock the files at the given storage paths in the backend.
1143          *
1144          * @param $paths Array Storage paths
1145          * @param $type integer LockManager::LOCK_* constant
1146          * @return Status
1147          */
1148         final public function unlockFiles( array $paths, $type ) {
1149                 return $this->lockManager->unlock( $paths, $type );
1150         }
1151
1152         /**
1153          * Lock the files at the given storage paths in the backend.
1154          * This will either lock all the files or none (on failure).
1155          * On failure, the status object will be updated with errors.
1156          *
1157          * Once the return value goes out scope, the locks will be released and
1158          * the status updated. Unlock fatals will not change the status "OK" value.
1159          *
1160          * @param $paths Array Storage paths
1161          * @param $type integer LockManager::LOCK_* constant
1162          * @param $status Status Status to update on lock/unlock
1163          * @return ScopedLock|null Returns null on failure
1164          */
1165         final public function getScopedFileLocks( array $paths, $type, Status $status ) {
1166                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status );
1167         }
1168
1169         /**
1170          * Get an array of scoped locks needed for a batch of file operations.
1171          *
1172          * Normally, FileBackend::doOperations() handles locking, unless
1173          * the 'nonLocking' param is passed in. This function is useful if you
1174          * want the files to be locked for a broader scope than just when the
1175          * files are changing. For example, if you need to update DB metadata,
1176          * you may want to keep the files locked until finished.
1177          *
1178          * @see FileBackend::doOperations()
1179          *
1180          * @param $ops Array List of file operations to FileBackend::doOperations()
1181          * @param $status Status Status to update on lock/unlock
1182          * @return Array List of ScopedFileLocks or null values
1183          * @since 1.20
1184          */
1185         abstract public function getScopedLocksForOps( array $ops, Status $status );
1186
1187         /**
1188          * Get the root storage path of this backend.
1189          * All container paths are "subdirectories" of this path.
1190          *
1191          * @return string Storage path
1192          * @since 1.20
1193          */
1194         final public function getRootStoragePath() {
1195                 return "mwstore://{$this->name}";
1196         }
1197
1198         /**
1199          * Get the storage path for the given container for this backend
1200          *
1201          * @param $container string Container name
1202          * @return string Storage path
1203          * @since 1.21
1204          */
1205         final public function getContainerStoragePath( $container ) {
1206                 return $this->getRootStoragePath() . "/{$container}";
1207         }
1208
1209         /**
1210          * Get the file journal object for this backend
1211          *
1212          * @return FileJournal
1213          */
1214         final public function getJournal() {
1215                 return $this->fileJournal;
1216         }
1217
1218         /**
1219          * Check if a given path is a "mwstore://" path.
1220          * This does not do any further validation or any existence checks.
1221          *
1222          * @param $path string
1223          * @return bool
1224          */
1225         final public static function isStoragePath( $path ) {
1226                 return ( strpos( $path, 'mwstore://' ) === 0 );
1227         }
1228
1229         /**
1230          * Split a storage path into a backend name, a container name,
1231          * and a relative file path. The relative path may be the empty string.
1232          * This does not do any path normalization or traversal checks.
1233          *
1234          * @param $storagePath string
1235          * @return Array (backend, container, rel object) or (null, null, null)
1236          */
1237         final public static function splitStoragePath( $storagePath ) {
1238                 if ( self::isStoragePath( $storagePath ) ) {
1239                         // Remove the "mwstore://" prefix and split the path
1240                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
1241                         if ( count( $parts ) >= 2 && $parts[0] != '' && $parts[1] != '' ) {
1242                                 if ( count( $parts ) == 3 ) {
1243                                         return $parts; // e.g. "backend/container/path"
1244                                 } else {
1245                                         return array( $parts[0], $parts[1], '' ); // e.g. "backend/container"
1246                                 }
1247                         }
1248                 }
1249                 return array( null, null, null );
1250         }
1251
1252         /**
1253          * Normalize a storage path by cleaning up directory separators.
1254          * Returns null if the path is not of the format of a valid storage path.
1255          *
1256          * @param $storagePath string
1257          * @return string|null
1258          */
1259         final public static function normalizeStoragePath( $storagePath ) {
1260                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
1261                 if ( $relPath !== null ) { // must be for this backend
1262                         $relPath = self::normalizeContainerPath( $relPath );
1263                         if ( $relPath !== null ) {
1264                                 return ( $relPath != '' )
1265                                         ? "mwstore://{$backend}/{$container}/{$relPath}"
1266                                         : "mwstore://{$backend}/{$container}";
1267                         }
1268                 }
1269                 return null;
1270         }
1271
1272         /**
1273          * Get the parent storage directory of a storage path.
1274          * This returns a path like "mwstore://backend/container",
1275          * "mwstore://backend/container/...", or null if there is no parent.
1276          *
1277          * @param $storagePath string
1278          * @return string|null
1279          */
1280         final public static function parentStoragePath( $storagePath ) {
1281                 $storagePath = dirname( $storagePath );
1282                 list( $b, $cont, $rel ) = self::splitStoragePath( $storagePath );
1283                 return ( $rel === null ) ? null : $storagePath;
1284         }
1285
1286         /**
1287          * Get the final extension from a storage or FS path
1288          *
1289          * @param $path string
1290          * @return string
1291          */
1292         final public static function extensionFromPath( $path ) {
1293                 $i = strrpos( $path, '.' );
1294                 return strtolower( $i ? substr( $path, $i + 1 ) : '' );
1295         }
1296
1297         /**
1298          * Check if a relative path has no directory traversals
1299          *
1300          * @param $path string
1301          * @return bool
1302          * @since 1.20
1303          */
1304         final public static function isPathTraversalFree( $path ) {
1305                 return ( self::normalizeContainerPath( $path ) !== null );
1306         }
1307
1308         /**
1309          * Build a Content-Disposition header value per RFC 6266.
1310          *
1311          * @param $type string One of (attachment, inline)
1312          * @param $filename string Suggested file name (should not contain slashes)
1313          * @throws MWException
1314          * @return string
1315          * @since 1.20
1316          */
1317         final public static function makeContentDisposition( $type, $filename = '' ) {
1318                 $parts = array();
1319
1320                 $type = strtolower( $type );
1321                 if ( !in_array( $type, array( 'inline', 'attachment' ) ) ) {
1322                         throw new MWException( "Invalid Content-Disposition type '$type'." );
1323                 }
1324                 $parts[] = $type;
1325
1326                 if ( strlen( $filename ) ) {
1327                         $parts[] = "filename*=UTF-8''" . rawurlencode( basename( $filename ) );
1328                 }
1329
1330                 return implode( ';', $parts );
1331         }
1332
1333         /**
1334          * Validate and normalize a relative storage path.
1335          * Null is returned if the path involves directory traversal.
1336          * Traversal is insecure for FS backends and broken for others.
1337          *
1338          * This uses the same traversal protection as Title::secureAndSplit().
1339          *
1340          * @param $path string Storage path relative to a container
1341          * @return string|null
1342          */
1343         final protected static function normalizeContainerPath( $path ) {
1344                 // Normalize directory separators
1345                 $path = strtr( $path, '\\', '/' );
1346                 // Collapse any consecutive directory separators
1347                 $path = preg_replace( '![/]{2,}!', '/', $path );
1348                 // Remove any leading directory separator
1349                 $path = ltrim( $path, '/' );
1350                 // Use the same traversal protection as Title::secureAndSplit()
1351                 if ( strpos( $path, '.' ) !== false ) {
1352                         if (
1353                                 $path === '.' ||
1354                                 $path === '..' ||
1355                                 strpos( $path, './' ) === 0 ||
1356                                 strpos( $path, '../' ) === 0 ||
1357                                 strpos( $path, '/./' ) !== false ||
1358                                 strpos( $path, '/../' ) !== false
1359                         ) {
1360                                 return null;
1361                         }
1362                 }
1363                 return $path;
1364         }
1365 }