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         /** @var  string Unique backend name */
  64         protected $name;
  65
  66         /** @var string Unique wiki name */
  67         protected $wikiId;
  68
  69         /** @var string Read-only explanation message */
  70         protected $readOnly;
  71
  72         /** @var string When to do operations in parallel */
  73         protected $parallelize;
  74
  75         /** @var int How many operations can be done in parallel */
  76         protected $concurrency;
  77
  78         /** @var LockManager */
  79         protected $lockManager;
  80
  81         /** @var FileJournal */
  82         protected $fileJournal;
  83
  84         /**
  85          * Create a new backend instance from configuration.
  86          * This should only be called from within FileBackendGroup.
  87          *
  88          * @param array $config Parameters include:
  89          *   - name        : The unique name of this backend.
  90          *                   This should consist of alphanumberic, '-', and '_' characters.
  91          *                   This name should not be changed after use (e.g. with journaling).
  92          *                   Note that the name is *not* used in actual container names.
  93          *   - wikiId      : Prefix to container names that is unique to this backend.
  94          *                   It should only consist of alphanumberic, '-', and '_' characters.
  95          *                   This ID is what avoids collisions if multiple logical backends
  96          *                   use the same storage system, so this should be set carefully.
  97          *   - lockManager : LockManager object to use for any file locking.
  98          *                   If not provided, then no file locking will be enforced.
  99          *   - fileJournal : FileJournal object to use for logging changes to files.
 100          *                   If not provided, then change journaling will be disabled.
 101          *   - readOnly    : Write operations are disallowed if this is a non-empty string.
 102          *                   It should be an explanation for the backend being read-only.
 103          *   - parallelize : When to do file operations in parallel (when possible).
 104          *                   Allowed values are "implicit", "explicit" and "off".
 105          *   - concurrency : How many file operations can be done in parallel.
 106          * @throws MWException
 107          */
 108         public function __construct( array $config ) {
 109                 $this->name = $config['name'];
 110                 if ( !preg_match( '!^[a-zA-Z0-9-_]{1,255}$!', $this->name ) ) {
 111                         throw new MWException( "Backend name `{$this->name}` is invalid." );
 112                 }
 113                 if ( !isset( $config['wikiId'] ) ) {
 114                         $config['wikiId'] = wfWikiID();
 115                         wfDeprecated( __METHOD__ . ' called without "wikiID".', '1.23' );
 116                 }
 117                 if ( isset( $config['lockManager'] ) && !is_object( $config['lockManager'] ) ) {
 118                         $config['lockManager'] =
 119                                 LockManagerGroup::singleton( $config['wikiId'] )->get( $config['lockManager'] );
 120                         wfDeprecated( __METHOD__ . ' called with non-object "lockManager".', '1.23' );
 121                 }
 122                 $this->wikiId = $config['wikiId']; // e.g. "my_wiki-en_"
 123                 $this->lockManager = isset( $config['lockManager'] )
 124                         ? $config['lockManager']
 125                         : new NullLockManager( array() );
 126                 $this->fileJournal = isset( $config['fileJournal'] )
 127                         ? $config['fileJournal']
 128                         : FileJournal::factory( array( 'class' => 'NullFileJournal' ), $this->name );
 129                 $this->readOnly = isset( $config['readOnly'] )
 130                         ? (string)$config['readOnly']
 131                         : '';
 132                 $this->parallelize = isset( $config['parallelize'] )
 133                         ? (string)$config['parallelize']
 134                         : 'off';
 135                 $this->concurrency = isset( $config['concurrency'] )
 136                         ? (int)$config['concurrency']
 137                         : 50;
 138         }
 139
 140         /**
 141          * Get the unique backend name.
 142          * We may have multiple different backends of the same type.
 143          * For example, we can have two Swift backends using different proxies.
 144          *
 145          * @return string
 146          */
 147         final public function getName() {
 148                 return $this->name;
 149         }
 150
 151         /**
 152          * Get the wiki identifier used for this backend (possibly empty).
 153          * Note that this might *not* be in the same format as wfWikiID().
 154          *
 155          * @return string
 156          * @since 1.20
 157          */
 158         final public function getWikiId() {
 159                 return $this->wikiId;
 160         }
 161
 162         /**
 163          * Check if this backend is read-only
 164          *
 165          * @return bool
 166          */
 167         final public function isReadOnly() {
 168                 return ( $this->readOnly != '' );
 169         }
 170
 171         /**
 172          * Get an explanatory message if this backend is read-only
 173          *
 174          * @return string|bool Returns false if the backend is not read-only
 175          */
 176         final public function getReadOnlyReason() {
 177                 return ( $this->readOnly != '' ) ? $this->readOnly : false;
 178         }
 179
 180         /**
 181          * This is the main entry point into the backend for write operations.
 182          * Callers supply an ordered list of operations to perform as a transaction.
 183          * Files will be locked, the stat cache cleared, and then the operations attempted.
 184          * If any serious errors occur, all attempted operations will be rolled back.
 185          *
 186          * $ops is an array of arrays. The outer array holds a list of operations.
 187          * Each inner array is a set of key value pairs that specify an operation.
 188          *
 189          * Supported operations and their parameters. The supported actions are:
 190          *  - create
 191          *  - store
 192          *  - copy
 193          *  - move
 194          *  - delete
 195          *  - describe (since 1.21)
 196          *  - null
 197          *
 198          * a) Create a new file in storage with the contents of a string
 199          * @code
 200          *     array(
 201          *         'op'                  => 'create',
 202          *         'dst'                 => <storage path>,
 203          *         'content'             => <string of new file contents>,
 204          *         'overwrite'           => <boolean>,
 205          *         'overwriteSame'       => <boolean>,
 206          *         'headers'             => <HTTP header name/value map> # since 1.21
 207          *     );
 208          * @endcode
 209          *
 210          * b) Copy a file system file into storage
 211          * @code
 212          *     array(
 213          *         'op'                  => 'store',
 214          *         'src'                 => <file system path>,
 215          *         'dst'                 => <storage path>,
 216          *         'overwrite'           => <boolean>,
 217          *         'overwriteSame'       => <boolean>,
 218          *         'headers'             => <HTTP header name/value map> # since 1.21
 219          *     )
 220          * @endcode
 221          *
 222          * c) Copy a file within storage
 223          * @code
 224          *     array(
 225          *         'op'                  => 'copy',
 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          * d) Move a file within storage
 236          * @code
 237          *     array(
 238          *         'op'                  => 'move',
 239          *         'src'                 => <storage path>,
 240          *         'dst'                 => <storage path>,
 241          *         'overwrite'           => <boolean>,
 242          *         'overwriteSame'       => <boolean>,
 243          *         'ignoreMissingSource' => <boolean>, # since 1.21
 244          *         'headers'             => <HTTP header name/value map> # since 1.21
 245          *     )
 246          * @endcode
 247          *
 248          * e) Delete a file within storage
 249          * @code
 250          *     array(
 251          *         'op'                  => 'delete',
 252          *         'src'                 => <storage path>,
 253          *         'ignoreMissingSource' => <boolean>
 254          *     )
 255          * @endcode
 256          *
 257          * f) Update metadata for a file within storage
 258          * @code
 259          *     array(
 260          *         'op'                  => 'describe',
 261          *         'src'                 => <storage path>,
 262          *         'headers'             => <HTTP header name/value map>
 263          *     )
 264          * @endcode
 265          *
 266          * g) Do nothing (no-op)
 267          * @code
 268          *     array(
 269          *         'op'                  => 'null',
 270          *     )
 271          * @endcode
 272          *
 273          * Boolean flags for operations (operation-specific):
 274          *   - ignoreMissingSource : The operation will simply succeed and do
 275          *                           nothing if the source file does not exist.
 276          *   - overwrite           : Any destination file will be overwritten.
 277          *   - overwriteSame       : If a file already exists at the destination with the
 278          *                           same contents, then do nothing to the destination file
 279          *                           instead of giving an error. This does not compare headers.
 280          *                           This option is ignored if 'overwrite' is already provided.
 281          *   - headers             : If supplied, the result of merging these headers with any
 282          *                           existing source file headers (replacing conflicting ones)
 283          *                           will be set as the destination file headers. Headers are
 284          *                           deleted if their value is set to the empty string. When a
 285          *                           file has headers they are included in responses to GET and
 286          *                           HEAD requests to the backing store for that file.
 287          *                           Header values should be no larger than 255 bytes, except for
 288          *                           Content-Disposition. The system might ignore or truncate any
 289          *                           headers that are too long to store (exact limits will vary).
 290          *                           Backends that don't support metadata ignore this. (since 1.21)
 291          *
 292          * $opts is an associative of boolean flags, including:
 293          *   - force               : Operation precondition errors no longer trigger an abort.
 294          *                           Any remaining operations are still attempted. Unexpected
 295          *                           failures may still cause remaining operations to be aborted.
 296          *   - nonLocking          : No locks are acquired for the operations.
 297          *                           This can increase performance for non-critical writes.
 298          *                           This has no effect unless the 'force' flag is set.
 299          *   - nonJournaled        : Don't log this operation batch in the file journal.
 300          *                           This limits the ability of recovery scripts.
 301          *   - parallelize         : Try to do operations in parallel when possible.
 302          *   - bypassReadOnly      : Allow writes in read-only mode. (since 1.20)
 303          *   - preserveCache       : Don't clear the process cache before checking files.
 304          *                           This should only be used if all entries in the process
 305          *                           cache were added after the files were already locked. (since 1.20)
 306          *
 307          * @remarks Remarks on locking:
 308          * File system paths given to operations should refer to files that are
 309          * already locked or otherwise safe from modification from other processes.
 310          * Normally these files will be new temp files, which should be adequate.
 311          *
 312          * @par Return value:
 313          *
 314          * This returns a Status, which contains all warnings and fatals that occurred
 315          * during the operation. The 'failCount', 'successCount', and 'success' members
 316          * will reflect each operation attempted.
 317          *
 318          * The status will be "OK" unless:
 319          *   - a) unexpected operation errors occurred (network partitions, disk full...)
 320          *   - b) significant operation errors occurred and 'force' was not set
 321          *
 322          * @param array $ops List of operations to execute in order
 323          * @param array $opts Batch operation options
 324          * @return Status
 325          */
 326         final public function doOperations( array $ops, array $opts = array() ) {
 327                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 328                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 329                 }
 330                 if ( !count( $ops ) ) {
 331                         return Status::newGood(); // nothing to do
 332                 }
 333                 if ( empty( $opts['force'] ) ) { // sanity
 334                         unset( $opts['nonLocking'] );
 335                 }
 336                 foreach ( $ops as &$op ) {
 337                         if ( isset( $op['disposition'] ) ) { // b/c (MW 1.20)
 338                                 $op['headers']['Content-Disposition'] = $op['disposition'];
 339                         }
 340                 }
 341                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 342                 return $this->doOperationsInternal( $ops, $opts );
 343         }
 344
 345         /**
 346          * @see FileBackend::doOperations()
 347          */
 348         abstract protected function doOperationsInternal( array $ops, array $opts );
 349
 350         /**
 351          * Same as doOperations() except it takes a single operation.
 352          * If you are doing a batch of operations that should either
 353          * all succeed or all fail, then use that function instead.
 354          *
 355          * @see FileBackend::doOperations()
 356          *
 357          * @param array $op Operation
 358          * @param array $opts Operation options
 359          * @return Status
 360          */
 361         final public function doOperation( array $op, array $opts = array() ) {
 362                 return $this->doOperations( array( $op ), $opts );
 363         }
 364
 365         /**
 366          * Performs a single create operation.
 367          * This sets $params['op'] to 'create' and passes it to doOperation().
 368          *
 369          * @see FileBackend::doOperation()
 370          *
 371          * @param array $params Operation parameters
 372          * @param array $opts Operation options
 373          * @return Status
 374          */
 375         final public function create( array $params, array $opts = array() ) {
 376                 return $this->doOperation( array( 'op' => 'create' ) + $params, $opts );
 377         }
 378
 379         /**
 380          * Performs a single store operation.
 381          * This sets $params['op'] to 'store' and passes it to doOperation().
 382          *
 383          * @see FileBackend::doOperation()
 384          *
 385          * @param array $params Operation parameters
 386          * @param array $opts Operation options
 387          * @return Status
 388          */
 389         final public function store( array $params, array $opts = array() ) {
 390                 return $this->doOperation( array( 'op' => 'store' ) + $params, $opts );
 391         }
 392
 393         /**
 394          * Performs a single copy operation.
 395          * This sets $params['op'] to 'copy' and passes it to doOperation().
 396          *
 397          * @see FileBackend::doOperation()
 398          *
 399          * @param array $params Operation parameters
 400          * @param array $opts Operation options
 401          * @return Status
 402          */
 403         final public function copy( array $params, array $opts = array() ) {
 404                 return $this->doOperation( array( 'op' => 'copy' ) + $params, $opts );
 405         }
 406
 407         /**
 408          * Performs a single move operation.
 409          * This sets $params['op'] to 'move' and passes it to doOperation().
 410          *
 411          * @see FileBackend::doOperation()
 412          *
 413          * @param array $params Operation parameters
 414          * @param array $opts Operation options
 415          * @return Status
 416          */
 417         final public function move( array $params, array $opts = array() ) {
 418                 return $this->doOperation( array( 'op' => 'move' ) + $params, $opts );
 419         }
 420
 421         /**
 422          * Performs a single delete operation.
 423          * This sets $params['op'] to 'delete' and passes it to doOperation().
 424          *
 425          * @see FileBackend::doOperation()
 426          *
 427          * @param array $params Operation parameters
 428          * @param array $opts Operation options
 429          * @return Status
 430          */
 431         final public function delete( array $params, array $opts = array() ) {
 432                 return $this->doOperation( array( 'op' => 'delete' ) + $params, $opts );
 433         }
 434
 435         /**
 436          * Performs a single describe operation.
 437          * This sets $params['op'] to 'describe' and passes it to doOperation().
 438          *
 439          * @see FileBackend::doOperation()
 440          *
 441          * @param array $params Operation parameters
 442          * @param array $opts Operation options
 443          * @return Status
 444          * @since 1.21
 445          */
 446         final public function describe( array $params, array $opts = array() ) {
 447                 return $this->doOperation( array( 'op' => 'describe' ) + $params, $opts );
 448         }
 449
 450         /**
 451          * Perform a set of independent file operations on some files.
 452          *
 453          * This does no locking, nor journaling, and possibly no stat calls.
 454          * Any destination files that already exist will be overwritten.
 455          * This should *only* be used on non-original files, like cache files.
 456          *
 457          * Supported operations and their parameters:
 458          *  - create
 459          *  - store
 460          *  - copy
 461          *  - move
 462          *  - delete
 463          *  - describe (since 1.21)
 464          *  - null
 465          *
 466          * a) Create a new file in storage with the contents of a string
 467          * @code
 468          *     array(
 469          *         'op'                  => 'create',
 470          *         'dst'                 => <storage path>,
 471          *         'content'             => <string of new file contents>,
 472          *         'headers'             => <HTTP header name/value map> # since 1.21
 473          *     )
 474          * @endcode
 475          *
 476          * b) Copy a file system file into storage
 477          * @code
 478          *     array(
 479          *         'op'                  => 'store',
 480          *         'src'                 => <file system path>,
 481          *         'dst'                 => <storage path>,
 482          *         'headers'             => <HTTP header name/value map> # since 1.21
 483          *     )
 484          * @endcode
 485          *
 486          * c) Copy a file within storage
 487          * @code
 488          *     array(
 489          *         'op'                  => 'copy',
 490          *         'src'                 => <storage path>,
 491          *         'dst'                 => <storage path>,
 492          *         'ignoreMissingSource' => <boolean>, # since 1.21
 493          *         'headers'             => <HTTP header name/value map> # since 1.21
 494          *     )
 495          * @endcode
 496          *
 497          * d) Move a file within storage
 498          * @code
 499          *     array(
 500          *         'op'                  => 'move',
 501          *         'src'                 => <storage path>,
 502          *         'dst'                 => <storage path>,
 503          *         'ignoreMissingSource' => <boolean>, # since 1.21
 504          *         'headers'             => <HTTP header name/value map> # since 1.21
 505          *     )
 506          * @endcode
 507          *
 508          * e) Delete a file within storage
 509          * @code
 510          *     array(
 511          *         'op'                  => 'delete',
 512          *         'src'                 => <storage path>,
 513          *         'ignoreMissingSource' => <boolean>
 514          *     )
 515          * @endcode
 516          *
 517          * f) Update metadata for a file within storage
 518          * @code
 519          *     array(
 520          *         'op'                  => 'describe',
 521          *         'src'                 => <storage path>,
 522          *         'headers'             => <HTTP header name/value map>
 523          *     )
 524          * @endcode
 525          *
 526          * g) Do nothing (no-op)
 527          * @code
 528          *     array(
 529          *         'op'                  => 'null',
 530          *     )
 531          * @endcode
 532          *
 533          * @par Boolean flags for operations (operation-specific):
 534          *   - ignoreMissingSource : The operation will simply succeed and do
 535          *                           nothing if the source file does not exist.
 536          *   - headers             : If supplied with a header name/value map, the backend will
 537          *                           reply with these headers when GETs/HEADs of the destination
 538          *                           file are made. Header values should be smaller than 256 bytes.
 539          *                           Content-Disposition headers can be longer, though the system
 540          *                           might ignore or truncate ones that are too long to store.
 541          *                           Existing headers will remain, but these will replace any
 542          *                           conflicting previous headers, and headers will be removed
 543          *                           if they are set to an empty string.
 544          *                           Backends that don't support metadata ignore this. (since 1.21)
 545          *
 546          * $opts is an associative of boolean flags, including:
 547          *   - bypassReadOnly      : Allow writes in read-only mode (since 1.20)
 548          *
 549          * @par Return value:
 550          * This returns a Status, which contains all warnings and fatals that occurred
 551          * during the operation. The 'failCount', 'successCount', and 'success' members
 552          * will reflect each operation attempted for the given files. The status will be
 553          * considered "OK" as long as no fatal errors occurred.
 554          *
 555          * @param array $ops Set of operations to execute
 556          * @param array $opts Batch operation options
 557          * @return Status
 558          * @since 1.20
 559          */
 560         final public function doQuickOperations( array $ops, array $opts = array() ) {
 561                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 562                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 563                 }
 564                 if ( !count( $ops ) ) {
 565                         return Status::newGood(); // nothing to do
 566                 }
 567                 foreach ( $ops as &$op ) {
 568                         $op['overwrite'] = true; // avoids RTTs in key/value stores
 569                         if ( isset( $op['disposition'] ) ) { // b/c (MW 1.20)
 570                                 $op['headers']['Content-Disposition'] = $op['disposition'];
 571                         }
 572                 }
 573                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 574                 return $this->doQuickOperationsInternal( $ops );
 575         }
 576
 577         /**
 578          * @see FileBackend::doQuickOperations()
 579          * @since 1.20
 580          */
 581         abstract protected function doQuickOperationsInternal( array $ops );
 582
 583         /**
 584          * Same as doQuickOperations() except it takes a single operation.
 585          * If you are doing a batch of operations, then use that function instead.
 586          *
 587          * @see FileBackend::doQuickOperations()
 588          *
 589          * @param array $op Operation
 590          * @return Status
 591          * @since 1.20
 592          */
 593         final public function doQuickOperation( array $op ) {
 594                 return $this->doQuickOperations( array( $op ) );
 595         }
 596
 597         /**
 598          * Performs a single quick create operation.
 599          * This sets $params['op'] to 'create' and passes it to doQuickOperation().
 600          *
 601          * @see FileBackend::doQuickOperation()
 602          *
 603          * @param array $params Operation parameters
 604          * @return Status
 605          * @since 1.20
 606          */
 607         final public function quickCreate( array $params ) {
 608                 return $this->doQuickOperation( array( 'op' => 'create' ) + $params );
 609         }
 610
 611         /**
 612          * Performs a single quick store operation.
 613          * This sets $params['op'] to 'store' and passes it to doQuickOperation().
 614          *
 615          * @see FileBackend::doQuickOperation()
 616          *
 617          * @param array $params Operation parameters
 618          * @return Status
 619          * @since 1.20
 620          */
 621         final public function quickStore( array $params ) {
 622                 return $this->doQuickOperation( array( 'op' => 'store' ) + $params );
 623         }
 624
 625         /**
 626          * Performs a single quick copy operation.
 627          * This sets $params['op'] to 'copy' and passes it to doQuickOperation().
 628          *
 629          * @see FileBackend::doQuickOperation()
 630          *
 631          * @param array $params Operation parameters
 632          * @return Status
 633          * @since 1.20
 634          */
 635         final public function quickCopy( array $params ) {
 636                 return $this->doQuickOperation( array( 'op' => 'copy' ) + $params );
 637         }
 638
 639         /**
 640          * Performs a single quick move operation.
 641          * This sets $params['op'] to 'move' and passes it to doQuickOperation().
 642          *
 643          * @see FileBackend::doQuickOperation()
 644          *
 645          * @param array $params Operation parameters
 646          * @return Status
 647          * @since 1.20
 648          */
 649         final public function quickMove( array $params ) {
 650                 return $this->doQuickOperation( array( 'op' => 'move' ) + $params );
 651         }
 652
 653         /**
 654          * Performs a single quick delete operation.
 655          * This sets $params['op'] to 'delete' and passes it to doQuickOperation().
 656          *
 657          * @see FileBackend::doQuickOperation()
 658          *
 659          * @param array $params Operation parameters
 660          * @return Status
 661          * @since 1.20
 662          */
 663         final public function quickDelete( array $params ) {
 664                 return $this->doQuickOperation( array( 'op' => 'delete' ) + $params );
 665         }
 666
 667         /**
 668          * Performs a single quick describe operation.
 669          * This sets $params['op'] to 'describe' and passes it to doQuickOperation().
 670          *
 671          * @see FileBackend::doQuickOperation()
 672          *
 673          * @param array $params Operation parameters
 674          * @return Status
 675          * @since 1.21
 676          */
 677         final public function quickDescribe( array $params ) {
 678                 return $this->doQuickOperation( array( 'op' => 'describe' ) + $params );
 679         }
 680
 681         /**
 682          * Concatenate a list of storage files into a single file system file.
 683          * The target path should refer to a file that is already locked or
 684          * otherwise safe from modification from other processes. Normally,
 685          * the file will be a new temp file, which should be adequate.
 686          *
 687          * @param array $params Operation parameters, include:
 688          *   - srcs        : ordered source storage paths (e.g. chunk1, chunk2, ...)
 689          *   - dst         : file system path to 0-byte temp file
 690          *   - parallelize : try to do operations in parallel when possible
 691          * @return Status
 692          */
 693         abstract public function concatenate( array $params );
 694
 695         /**
 696          * Prepare a storage directory for usage.
 697          * This will create any required containers and parent directories.
 698          * Backends using key/value stores only need to create the container.
 699          *
 700          * The 'noAccess' and 'noListing' parameters works the same as in secure(),
 701          * except they are only applied *if* the directory/container had to be created.
 702          * These flags should always be set for directories that have private files.
 703          * However, setting them is not guaranteed to actually do anything.
 704          * Additional server configuration may be needed to achieve the desired effect.
 705          *
 706          * @param array $params Parameters include:
 707          *   - dir            : storage directory
 708          *   - noAccess       : try to deny file access (since 1.20)
 709          *   - noListing      : try to deny file listing (since 1.20)
 710          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 711          * @return Status
 712          */
 713         final public function prepare( array $params ) {
 714                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 715                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 716                 }
 717                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 718                 return $this->doPrepare( $params );
 719         }
 720
 721         /**
 722          * @see FileBackend::prepare()
 723          */
 724         abstract protected function doPrepare( array $params );
 725
 726         /**
 727          * Take measures to block web access to a storage directory and
 728          * the container it belongs to. FS backends might add .htaccess
 729          * files whereas key/value store backends might revoke container
 730          * access to the storage user representing end-users in web requests.
 731          *
 732          * This is not guaranteed to actually make files or listings publically hidden.
 733          * Additional server configuration may be needed to achieve the desired effect.
 734          *
 735          * @param array $params Parameters include:
 736          *   - dir            : storage directory
 737          *   - noAccess       : try to deny file access
 738          *   - noListing      : try to deny file listing
 739          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 740          * @return Status
 741          */
 742         final public function secure( array $params ) {
 743                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 744                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 745                 }
 746                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 747                 return $this->doSecure( $params );
 748         }
 749
 750         /**
 751          * @see FileBackend::secure()
 752          */
 753         abstract protected function doSecure( array $params );
 754
 755         /**
 756          * Remove measures to block web access to a storage directory and
 757          * the container it belongs to. FS backends might remove .htaccess
 758          * files whereas key/value store backends might grant container
 759          * access to the storage user representing end-users in web requests.
 760          * This essentially can undo the result of secure() calls.
 761          *
 762          * This is not guaranteed to actually make files or listings publically viewable.
 763          * Additional server configuration may be needed to achieve the desired effect.
 764          *
 765          * @param array $params Parameters include:
 766          *   - dir            : storage directory
 767          *   - access         : try to allow file access
 768          *   - listing        : try to allow file listing
 769          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 770          * @return Status
 771          * @since 1.20
 772          */
 773         final public function publish( array $params ) {
 774                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 775                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 776                 }
 777                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 778                 return $this->doPublish( $params );
 779         }
 780
 781         /**
 782          * @see FileBackend::publish()
 783          */
 784         abstract protected function doPublish( array $params );
 785
 786         /**
 787          * Delete a storage directory if it is empty.
 788          * Backends using key/value stores may do nothing unless the directory
 789          * is that of an empty container, in which case it will be deleted.
 790          *
 791          * @param array $params Parameters include:
 792          *   - dir            : storage directory
 793          *   - recursive      : recursively delete empty subdirectories first (since 1.20)
 794          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 795          * @return Status
 796          */
 797         final public function clean( array $params ) {
 798                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 799                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 800                 }
 801                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 802                 return $this->doClean( $params );
 803         }
 804
 805         /**
 806          * @see FileBackend::clean()
 807          */
 808         abstract protected function doClean( array $params );
 809
 810         /**
 811          * Enter file operation scope.
 812          * This just makes PHP ignore user aborts/disconnects until the return
 813          * value leaves scope. This returns null and does nothing in CLI mode.
 814          *
 815          * @return ScopedCallback|null
 816          */
 817         final protected function getScopedPHPBehaviorForOps() {
 818                 if ( PHP_SAPI != 'cli' ) { // http://bugs.php.net/bug.php?id=47540
 819                         $old = ignore_user_abort( true ); // avoid half-finished operations
 820                         return new ScopedCallback( function () use ( $old ) {
 821                                 ignore_user_abort( $old );
 822                         } );
 823                 }
 824
 825                 return null;
 826         }
 827
 828         /**
 829          * Check if a file exists at a storage path in the backend.
 830          * This returns false if only a directory exists at the path.
 831          *
 832          * @param array $params Parameters include:
 833          *   - src    : source storage path
 834          *   - latest : use the latest available data
 835          * @return bool|null Returns null on failure
 836          */
 837         abstract public function fileExists( array $params );
 838
 839         /**
 840          * Get the last-modified timestamp of the file at a storage path.
 841          *
 842          * @param array $params Parameters include:
 843          *   - src    : source storage path
 844          *   - latest : use the latest available data
 845          * @return string|bool TS_MW timestamp or false on failure
 846          */
 847         abstract public function getFileTimestamp( array $params );
 848
 849         /**
 850          * Get the contents of a file at a storage path in the backend.
 851          * This should be avoided for potentially large files.
 852          *
 853          * @param array $params Parameters include:
 854          *   - src    : source storage path
 855          *   - latest : use the latest available data
 856          * @return string|bool Returns false on failure
 857          */
 858         final public function getFileContents( array $params ) {
 859                 $contents = $this->getFileContentsMulti(
 860                         array( 'srcs' => array( $params['src'] ) ) + $params );
 861
 862                 return $contents[$params['src']];
 863         }
 864
 865         /**
 866          * Like getFileContents() except it takes an array of storage paths
 867          * and returns a map of storage paths to strings (or null on failure).
 868          * The map keys (paths) are in the same order as the provided list of paths.
 869          *
 870          * @see FileBackend::getFileContents()
 871          *
 872          * @param array $params Parameters include:
 873          *   - srcs        : list of source storage paths
 874          *   - latest      : use the latest available data
 875          *   - parallelize : try to do operations in parallel when possible
 876          * @return array Map of (path name => string or false on failure)
 877          * @since 1.20
 878          */
 879         abstract public function getFileContentsMulti( array $params );
 880
 881         /**
 882          * Get the size (bytes) of a file at a storage path in the backend.
 883          *
 884          * @param array $params Parameters include:
 885          *   - src    : source storage path
 886          *   - latest : use the latest available data
 887          * @return int|bool Returns false on failure
 888          */
 889         abstract public function getFileSize( array $params );
 890
 891         /**
 892          * Get quick information about a file at a storage path in the backend.
 893          * If the file does not exist, then this returns false.
 894          * Otherwise, the result is an associative array that includes:
 895          *   - mtime  : the last-modified timestamp (TS_MW)
 896          *   - size   : the file size (bytes)
 897          * Additional values may be included for internal use only.
 898          *
 899          * @param array $params Parameters include:
 900          *   - src    : source storage path
 901          *   - latest : use the latest available data
 902          * @return array|bool|null Returns null on failure
 903          */
 904         abstract public function getFileStat( array $params );
 905
 906         /**
 907          * Get a SHA-1 hash of the file at a storage path in the backend.
 908          *
 909          * @param array $params Parameters include:
 910          *   - src    : source storage path
 911          *   - latest : use the latest available data
 912          * @return string|bool Hash string or false on failure
 913          */
 914         abstract public function getFileSha1Base36( array $params );
 915
 916         /**
 917          * Get the properties of the file at a storage path in the backend.
 918          * This gives the result of FSFile::getProps() on a local copy of the file.
 919          *
 920          * @param array $params Parameters include:
 921          *   - src    : source storage path
 922          *   - latest : use the latest available data
 923          * @return array Returns FSFile::placeholderProps() on failure
 924          */
 925         abstract public function getFileProps( array $params );
 926
 927         /**
 928          * Stream the file at a storage path in the backend.
 929          * If the file does not exists, an HTTP 404 error will be given.
 930          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
 931          * will be sent if streaming began, while none will be sent otherwise.
 932          * Implementations should flush the output buffer before sending data.
 933          *
 934          * @param array $params Parameters include:
 935          *   - src     : source storage path
 936          *   - headers : list of additional HTTP headers to send on success
 937          *   - latest  : use the latest available data
 938          * @return Status
 939          */
 940         abstract public function streamFile( array $params );
 941
 942         /**
 943          * Returns a file system file, identical to the file at a storage path.
 944          * The file returned is either:
 945          *   - a) A local copy of the file at a storage path in the backend.
 946          *        The temporary copy will have the same extension as the source.
 947          *   - b) An original of the file at a storage path in the backend.
 948          * Temporary files may be purged when the file object falls out of scope.
 949          *
 950          * Write operations should *never* be done on this file as some backends
 951          * may do internal tracking or may be instances of FileBackendMultiWrite.
 952          * In that later case, there are copies of the file that must stay in sync.
 953          * Additionally, further calls to this function may return the same file.
 954          *
 955          * @param array $params Parameters include:
 956          *   - src    : source storage path
 957          *   - latest : use the latest available data
 958          * @return FSFile|null Returns null on failure
 959          */
 960         final public function getLocalReference( array $params ) {
 961                 $fsFiles = $this->getLocalReferenceMulti(
 962                         array( 'srcs' => array( $params['src'] ) ) + $params );
 963
 964                 return $fsFiles[$params['src']];
 965         }
 966
 967         /**
 968          * Like getLocalReference() except it takes an array of storage paths
 969          * and returns a map of storage paths to FSFile objects (or null on failure).
 970          * The map keys (paths) are in the same order as the provided list of paths.
 971          *
 972          * @see FileBackend::getLocalReference()
 973          *
 974          * @param array $params Parameters include:
 975          *   - srcs        : list of source storage paths
 976          *   - latest      : use the latest available data
 977          *   - parallelize : try to do operations in parallel when possible
 978          * @return array Map of (path name => FSFile or null on failure)
 979          * @since 1.20
 980          */
 981         abstract public function getLocalReferenceMulti( array $params );
 982
 983         /**
 984          * Get a local copy on disk of the file at a storage path in the backend.
 985          * The temporary copy will have the same file extension as the source.
 986          * Temporary files may be purged when the file object falls out of scope.
 987          *
 988          * @param array $params Parameters include:
 989          *   - src    : source storage path
 990          *   - latest : use the latest available data
 991          * @return TempFSFile|null Returns null on failure
 992          */
 993         final public function getLocalCopy( array $params ) {
 994                 $tmpFiles = $this->getLocalCopyMulti(
 995                         array( 'srcs' => array( $params['src'] ) ) + $params );
 996
 997                 return $tmpFiles[$params['src']];
 998         }
 999
1000         /**
1001          * Like getLocalCopy() except it takes an array of storage paths and
1002          * returns a map of storage paths to TempFSFile objects (or null on failure).
1003          * The map keys (paths) are in the same order as the provided list of paths.
1004          *
1005          * @see FileBackend::getLocalCopy()
1006          *
1007          * @param array $params Parameters include:
1008          *   - srcs        : list of source storage paths
1009          *   - latest      : use the latest available data
1010          *   - parallelize : try to do operations in parallel when possible
1011          * @return array Map of (path name => TempFSFile or null on failure)
1012          * @since 1.20
1013          */
1014         abstract public function getLocalCopyMulti( array $params );
1015
1016         /**
1017          * Return an HTTP URL to a given file that requires no authentication to use.
1018          * The URL may be pre-authenticated (via some token in the URL) and temporary.
1019          * This will return null if the backend cannot make an HTTP URL for the file.
1020          *
1021          * This is useful for key/value stores when using scripts that seek around
1022          * large files and those scripts (and the backend) support HTTP Range headers.
1023          * Otherwise, one would need to use getLocalReference(), which involves loading
1024          * the entire file on to local disk.
1025          *
1026          * @param array $params Parameters include:
1027          *   - src : source storage path
1028          *   - ttl : lifetime (seconds) if pre-authenticated; default is 1 day
1029          * @return string|null
1030          * @since 1.21
1031          */
1032         abstract public function getFileHttpUrl( array $params );
1033
1034         /**
1035          * Check if a directory exists at a given storage path.
1036          * Backends using key/value stores will check if the path is a
1037          * virtual directory, meaning there are files under the given directory.
1038          *
1039          * Storage backends with eventual consistency might return stale data.
1040          *
1041          * @param array $params Parameters 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          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1059          *
1060          * @param array $params Parameters include:
1061          *   - dir     : storage directory
1062          *   - topOnly : only return direct child dirs of the directory
1063          * @return Traversable|Array|null Returns null on failure
1064          * @since 1.20
1065          */
1066         abstract public function getDirectoryList( array $params );
1067
1068         /**
1069          * Same as FileBackend::getDirectoryList() except only lists
1070          * directories that are immediately under the given directory.
1071          *
1072          * Storage backends with eventual consistency might return stale data.
1073          *
1074          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1075          *
1076          * @param array $params Parameters include:
1077          *   - dir : storage directory
1078          * @return Traversable|Array|null Returns null on failure
1079          * @since 1.20
1080          */
1081         final public function getTopDirectoryList( array $params ) {
1082                 return $this->getDirectoryList( array( 'topOnly' => true ) + $params );
1083         }
1084
1085         /**
1086          * Get an iterator to list *all* stored files under a storage directory.
1087          * If the directory is of the form "mwstore://backend/container",
1088          * then all files in the container will be listed.
1089          * If the directory is of form "mwstore://backend/container/dir",
1090          * then all files under that directory will be listed.
1091          * Results will be storage paths relative to the given directory.
1092          *
1093          * Storage backends with eventual consistency might return stale data.
1094          *
1095          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1096          *
1097          * @param array $params Parameters include:
1098          *   - dir        : storage directory
1099          *   - topOnly    : only return direct child files of the directory (since 1.20)
1100          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1101          * @return Traversable|Array|null Returns null on failure
1102          */
1103         abstract public function getFileList( array $params );
1104
1105         /**
1106          * Same as FileBackend::getFileList() except only lists
1107          * files that are immediately under the given directory.
1108          *
1109          * Storage backends with eventual consistency might return stale data.
1110          *
1111          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1112          *
1113          * @param array $params Parameters include:
1114          *   - dir        : storage directory
1115          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1116          * @return Traversable|Array|null Returns null on failure
1117          * @since 1.20
1118          */
1119         final public function getTopFileList( array $params ) {
1120                 return $this->getFileList( array( 'topOnly' => true ) + $params );
1121         }
1122
1123         /**
1124          * Preload persistent file stat and property cache into in-process cache.
1125          * This should be used when stat calls will be made on a known list of a many files.
1126          *
1127          * @param array $paths Storage paths
1128          */
1129         public function preloadCache( array $paths ) {
1130         }
1131
1132         /**
1133          * Invalidate any in-process file stat and property cache.
1134          * If $paths is given, then only the cache for those files will be cleared.
1135          *
1136          * @param array $paths Storage paths (optional)
1137          */
1138         public function clearCache( array $paths = null ) {
1139         }
1140
1141         /**
1142          * Lock the files at the given storage paths in the backend.
1143          * This will either lock all the files or none (on failure).
1144          *
1145          * Callers should consider using getScopedFileLocks() instead.
1146          *
1147          * @param array $paths Storage paths
1148          * @param int $type LockManager::LOCK_* constant
1149          * @return Status
1150          */
1151         final public function lockFiles( array $paths, $type ) {
1152                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1153
1154                 return $this->lockManager->lock( $paths, $type );
1155         }
1156
1157         /**
1158          * Unlock the files at the given storage paths in the backend.
1159          *
1160          * @param array $paths Storage paths
1161          * @param int $type LockManager::LOCK_* constant
1162          * @return Status
1163          */
1164         final public function unlockFiles( array $paths, $type ) {
1165                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1166
1167                 return $this->lockManager->unlock( $paths, $type );
1168         }
1169
1170         /**
1171          * Lock the files at the given storage paths in the backend.
1172          * This will either lock all the files or none (on failure).
1173          * On failure, the status object will be updated with errors.
1174          *
1175          * Once the return value goes out scope, the locks will be released and
1176          * the status updated. Unlock fatals will not change the status "OK" value.
1177          *
1178          * @see ScopedLock::factory()
1179          *
1180          * @param array $paths List of storage paths or map of lock types to path lists
1181          * @param int|string $type LockManager::LOCK_* constant or "mixed"
1182          * @param Status $status Status to update on lock/unlock
1183          * @return ScopedLock|null Returns null on failure
1184          */
1185         final public function getScopedFileLocks( array $paths, $type, Status $status ) {
1186                 if ( $type === 'mixed' ) {
1187                         foreach ( $paths as &$typePaths ) {
1188                                 $typePaths = array_map( 'FileBackend::normalizeStoragePath', $typePaths );
1189                         }
1190                 } else {
1191                         $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1192                 }
1193
1194                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status );
1195         }
1196
1197         /**
1198          * Get an array of scoped locks needed for a batch of file operations.
1199          *
1200          * Normally, FileBackend::doOperations() handles locking, unless
1201          * the 'nonLocking' param is passed in. This function is useful if you
1202          * want the files to be locked for a broader scope than just when the
1203          * files are changing. For example, if you need to update DB metadata,
1204          * you may want to keep the files locked until finished.
1205          *
1206          * @see FileBackend::doOperations()
1207          *
1208          * @param array $ops List of file operations to FileBackend::doOperations()
1209          * @param Status $status Status to update on lock/unlock
1210          * @return array List of ScopedFileLocks or null values
1211          * @since 1.20
1212          */
1213         abstract public function getScopedLocksForOps( array $ops, Status $status );
1214
1215         /**
1216          * Get the root storage path of this backend.
1217          * All container paths are "subdirectories" of this path.
1218          *
1219          * @return string Storage path
1220          * @since 1.20
1221          */
1222         final public function getRootStoragePath() {
1223                 return "mwstore://{$this->name}";
1224         }
1225
1226         /**
1227          * Get the storage path for the given container for this backend
1228          *
1229          * @param string $container Container name
1230          * @return string Storage path
1231          * @since 1.21
1232          */
1233         final public function getContainerStoragePath( $container ) {
1234                 return $this->getRootStoragePath() . "/{$container}";
1235         }
1236
1237         /**
1238          * Get the file journal object for this backend
1239          *
1240          * @return FileJournal
1241          */
1242         final public function getJournal() {
1243                 return $this->fileJournal;
1244         }
1245
1246         /**
1247          * Check if a given path is a "mwstore://" path.
1248          * This does not do any further validation or any existence checks.
1249          *
1250          * @param string $path
1251          * @return bool
1252          */
1253         final public static function isStoragePath( $path ) {
1254                 return ( strpos( $path, 'mwstore://' ) === 0 );
1255         }
1256
1257         /**
1258          * Split a storage path into a backend name, a container name,
1259          * and a relative file path. The relative path may be the empty string.
1260          * This does not do any path normalization or traversal checks.
1261          *
1262          * @param string $storagePath
1263          * @return array (backend, container, rel object) or (null, null, null)
1264          */
1265         final public static function splitStoragePath( $storagePath ) {
1266                 if ( self::isStoragePath( $storagePath ) ) {
1267                         // Remove the "mwstore://" prefix and split the path
1268                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
1269                         if ( count( $parts ) >= 2 && $parts[0] != '' && $parts[1] != '' ) {
1270                                 if ( count( $parts ) == 3 ) {
1271                                         return $parts; // e.g. "backend/container/path"
1272                                 } else {
1273                                         return array( $parts[0], $parts[1], '' ); // e.g. "backend/container"
1274                                 }
1275                         }
1276                 }
1277
1278                 return array( null, null, null );
1279         }
1280
1281         /**
1282          * Normalize a storage path by cleaning up directory separators.
1283          * Returns null if the path is not of the format of a valid storage path.
1284          *
1285          * @param string $storagePath
1286          * @return string|null
1287          */
1288         final public static function normalizeStoragePath( $storagePath ) {
1289                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
1290                 if ( $relPath !== null ) { // must be for this backend
1291                         $relPath = self::normalizeContainerPath( $relPath );
1292                         if ( $relPath !== null ) {
1293                                 return ( $relPath != '' )
1294                                         ? "mwstore://{$backend}/{$container}/{$relPath}"
1295                                         : "mwstore://{$backend}/{$container}";
1296                         }
1297                 }
1298
1299                 return null;
1300         }
1301
1302         /**
1303          * Get the parent storage directory of a storage path.
1304          * This returns a path like "mwstore://backend/container",
1305          * "mwstore://backend/container/...", or null if there is no parent.
1306          *
1307          * @param string $storagePath
1308          * @return string|null
1309          */
1310         final public static function parentStoragePath( $storagePath ) {
1311                 $storagePath = dirname( $storagePath );
1312                 list( , , $rel ) = self::splitStoragePath( $storagePath );
1313
1314                 return ( $rel === null ) ? null : $storagePath;
1315         }
1316
1317         /**
1318          * Get the final extension from a storage or FS path
1319          *
1320          * @param string $path
1321          * @return string
1322          */
1323         final public static function extensionFromPath( $path ) {
1324                 $i = strrpos( $path, '.' );
1325
1326                 return strtolower( $i ? substr( $path, $i + 1 ) : '' );
1327         }
1328
1329         /**
1330          * Check if a relative path has no directory traversals
1331          *
1332          * @param string $path
1333          * @return bool
1334          * @since 1.20
1335          */
1336         final public static function isPathTraversalFree( $path ) {
1337                 return ( self::normalizeContainerPath( $path ) !== null );
1338         }
1339
1340         /**
1341          * Build a Content-Disposition header value per RFC 6266.
1342          *
1343          * @param string $type One of (attachment, inline)
1344          * @param string $filename Suggested file name (should not contain slashes)
1345          * @throws MWException
1346          * @return string
1347          * @since 1.20
1348          */
1349         final public static function makeContentDisposition( $type, $filename = '' ) {
1350                 $parts = array();
1351
1352                 $type = strtolower( $type );
1353                 if ( !in_array( $type, array( 'inline', 'attachment' ) ) ) {
1354                         throw new MWException( "Invalid Content-Disposition type '$type'." );
1355                 }
1356                 $parts[] = $type;
1357
1358                 if ( strlen( $filename ) ) {
1359                         $parts[] = "filename*=UTF-8''" . rawurlencode( basename( $filename ) );
1360                 }
1361
1362                 return implode( ';', $parts );
1363         }
1364
1365         /**
1366          * Validate and normalize a relative storage path.
1367          * Null is returned if the path involves directory traversal.
1368          * Traversal is insecure for FS backends and broken for others.
1369          *
1370          * This uses the same traversal protection as Title::secureAndSplit().
1371          *
1372          * @param string $path Storage path relative to a container
1373          * @return string|null
1374          */
1375         final protected static function normalizeContainerPath( $path ) {
1376                 // Normalize directory separators
1377                 $path = strtr( $path, '\\', '/' );
1378                 // Collapse any consecutive directory separators
1379                 $path = preg_replace( '![/]{2,}!', '/', $path );
1380                 // Remove any leading directory separator
1381                 $path = ltrim( $path, '/' );
1382                 // Use the same traversal protection as Title::secureAndSplit()
1383                 if ( strpos( $path, '.' ) !== false ) {
1384                         if (
1385                                 $path === '.' ||
1386                                 $path === '..' ||
1387                                 strpos( $path, './' ) === 0 ||
1388                                 strpos( $path, '../' ) === 0 ||
1389                                 strpos( $path, '/./' ) !== false ||
1390                                 strpos( $path, '/../' ) !== false
1391                         ) {
1392                                 return null;
1393                         }
1394                 }
1395
1396                 return $path;
1397         }
1398 }
1399
1400 /**
1401  * @ingroup FileBackend
1402  * @since 1.22
1403  */
1404 class FileBackendError extends MWException {
1405 }