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 (object) stores, containers are 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  * In general, this class allows for callers to access storage through the same
  57  * interface, without regard to the underlying storage system. However, calling code
  58  * must follow certain patterns and be aware of certain things to ensure compatibility:
  59  *   - a) Always call prepare() on the parent directory before trying to put a file there;
  60  *        key/value stores only need the container to exist first, but filesystems need
  61  *        all the parent directories to exist first (prepare() is aware of all this)
  62  *   - b) Always call clean() on a directory when it might become empty to avoid empty
  63  *        directory buildup on filesystems; key/value stores never have empty directories,
  64  *        so doing this helps preserve consistency in both cases
  65  *   - c) Likewise, do not rely on the existence of empty directories for anything;
  66  *        calling directoryExists() on a path that prepare() was previously called on
  67  *        will return false for key/value stores if there are no files under that path
  68  *   - d) Never alter the resulting FSFile returned from getLocalReference(), as it could
  69  *        either be a copy of the source file in /tmp or the original source file itself
  70  *   - e) Use a file layout that results in never attempting to store files over directories
  71  *        or directories over files; key/value stores allow this but filesystems do not
  72  *   - f) Use ASCII file names (e.g. base32, IDs, hashes) to avoid Unicode issues in Windows
  73  *   - g) Do not assume that move operations are atomic (difficult with key/value stores)
  74  *   - h) Do not assume that file stat or read operations always have immediate consistency;
  75  *        various methods have a "latest" flag that should always be used if up-to-date
  76  *        information is required (this trades performance for correctness as needed)
  77  *   - i) Do not assume that directory listings have immediate consistency
  78  *
  79  * Methods of subclasses should avoid throwing exceptions at all costs.
  80  * As a corollary, external dependencies should be kept to a minimum.
  81  *
  82  * @ingroup FileBackend
  83  * @since 1.19
  84  */
  85 abstract class FileBackend {
  86         /** @var string Unique backend name */
  87         protected $name;
  88
  89         /** @var string Unique wiki name */
  90         protected $wikiId;
  91
  92         /** @var string Read-only explanation message */
  93         protected $readOnly;
  94
  95         /** @var string When to do operations in parallel */
  96         protected $parallelize;
  97
  98         /** @var int How many operations can be done in parallel */
  99         protected $concurrency;
 100
 101         /** @var LockManager */
 102         protected $lockManager;
 103
 104         /** @var FileJournal */
 105         protected $fileJournal;
 106
 107         /**
 108          * Create a new backend instance from configuration.
 109          * This should only be called from within FileBackendGroup.
 110          *
 111          * @param array $config Parameters include:
 112          *   - name        : The unique name of this backend.
 113          *                   This should consist of alphanumberic, '-', and '_' characters.
 114          *                   This name should not be changed after use (e.g. with journaling).
 115          *                   Note that the name is *not* used in actual container names.
 116          *   - wikiId      : Prefix to container names that is unique to this backend.
 117          *                   If not provided, this defaults to the current wiki ID.
 118          *                   It should only consist of alphanumberic, '-', and '_' characters.
 119          *                   This ID is what avoids collisions if multiple logical backends
 120          *                   use the same storage system, so this should be set carefully.
 121          *   - lockManager : Registered name of a file lock manager to use.
 122          *   - fileJournal : File journal configuration; see FileJournal::factory().
 123          *                   Journals simply log changes to files stored in the backend.
 124          *   - readOnly    : Write operations are disallowed if this is a non-empty string.
 125          *                   It should be an explanation for the backend being read-only.
 126          *   - parallelize : When to do file operations in parallel (when possible).
 127          *                   Allowed values are "implicit", "explicit" and "off".
 128          *   - concurrency : How many file operations can be done in parallel.
 129          * @throws MWException
 130          */
 131         public function __construct( array $config ) {
 132                 $this->name = $config['name'];
 133                 if ( !preg_match( '!^[a-zA-Z0-9-_]{1,255}$!', $this->name ) ) {
 134                         throw new MWException( "Backend name `{$this->name}` is invalid." );
 135                 }
 136                 $this->wikiId = isset( $config['wikiId'] )
 137                         ? $config['wikiId']
 138                         : wfWikiID(); // e.g. "my_wiki-en_"
 139                 $this->lockManager = ( $config['lockManager'] instanceof LockManager )
 140                         ? $config['lockManager']
 141                         : LockManagerGroup::singleton( $this->wikiId )->get( $config['lockManager'] );
 142                 $this->fileJournal = isset( $config['fileJournal'] )
 143                         ? ( ( $config['fileJournal'] instanceof FileJournal )
 144                                 ? $config['fileJournal']
 145                                 : FileJournal::factory( $config['fileJournal'], $this->name ) )
 146                         : FileJournal::factory( array( 'class' => 'NullFileJournal' ), $this->name );
 147                 $this->readOnly = isset( $config['readOnly'] )
 148                         ? (string)$config['readOnly']
 149                         : '';
 150                 $this->parallelize = isset( $config['parallelize'] )
 151                         ? (string)$config['parallelize']
 152                         : 'off';
 153                 $this->concurrency = isset( $config['concurrency'] )
 154                         ? (int)$config['concurrency']
 155                         : 50;
 156         }
 157
 158         /**
 159          * Get the unique backend name.
 160          * We may have multiple different backends of the same type.
 161          * For example, we can have two Swift backends using different proxies.
 162          *
 163          * @return string
 164          */
 165         final public function getName() {
 166                 return $this->name;
 167         }
 168
 169         /**
 170          * Get the wiki identifier used for this backend (possibly empty).
 171          * Note that this might *not* be in the same format as wfWikiID().
 172          *
 173          * @return string
 174          * @since 1.20
 175          */
 176         final public function getWikiId() {
 177                 return $this->wikiId;
 178         }
 179
 180         /**
 181          * Check if this backend is read-only
 182          *
 183          * @return bool
 184          */
 185         final public function isReadOnly() {
 186                 return ( $this->readOnly != '' );
 187         }
 188
 189         /**
 190          * Get an explanatory message if this backend is read-only
 191          *
 192          * @return string|bool Returns false if the backend is not read-only
 193          */
 194         final public function getReadOnlyReason() {
 195                 return ( $this->readOnly != '' ) ? $this->readOnly : false;
 196         }
 197
 198         /**
 199          * This is the main entry point into the backend for write operations.
 200          * Callers supply an ordered list of operations to perform as a transaction.
 201          * Files will be locked, the stat cache cleared, and then the operations attempted.
 202          * If any serious errors occur, all attempted operations will be rolled back.
 203          *
 204          * $ops is an array of arrays. The outer array holds a list of operations.
 205          * Each inner array is a set of key value pairs that specify an operation.
 206          *
 207          * Supported operations and their parameters. The supported actions are:
 208          *  - create
 209          *  - store
 210          *  - copy
 211          *  - move
 212          *  - delete
 213          *  - describe (since 1.21)
 214          *  - null
 215          *
 216          * a) Create a new file in storage with the contents of a string
 217          * @code
 218          *     array(
 219          *         'op'                  => 'create',
 220          *         'dst'                 => <storage path>,
 221          *         'content'             => <string of new file contents>,
 222          *         'overwrite'           => <boolean>,
 223          *         'overwriteSame'       => <boolean>,
 224          *         'headers'             => <HTTP header name/value map> # since 1.21
 225          *     );
 226          * @endcode
 227          *
 228          * b) Copy a file system file into storage
 229          * @code
 230          *     array(
 231          *         'op'                  => 'store',
 232          *         'src'                 => <file system path>,
 233          *         'dst'                 => <storage path>,
 234          *         'overwrite'           => <boolean>,
 235          *         'overwriteSame'       => <boolean>,
 236          *         'headers'             => <HTTP header name/value map> # since 1.21
 237          *     )
 238          * @endcode
 239          *
 240          * c) Copy a file within storage
 241          * @code
 242          *     array(
 243          *         'op'                  => 'copy',
 244          *         'src'                 => <storage path>,
 245          *         'dst'                 => <storage path>,
 246          *         'overwrite'           => <boolean>,
 247          *         'overwriteSame'       => <boolean>,
 248          *         'ignoreMissingSource' => <boolean>, # since 1.21
 249          *         'headers'             => <HTTP header name/value map> # since 1.21
 250          *     )
 251          * @endcode
 252          *
 253          * d) Move a file within storage
 254          * @code
 255          *     array(
 256          *         'op'                  => 'move',
 257          *         'src'                 => <storage path>,
 258          *         'dst'                 => <storage path>,
 259          *         'overwrite'           => <boolean>,
 260          *         'overwriteSame'       => <boolean>,
 261          *         'ignoreMissingSource' => <boolean>, # since 1.21
 262          *         'headers'             => <HTTP header name/value map> # since 1.21
 263          *     )
 264          * @endcode
 265          *
 266          * e) Delete a file within storage
 267          * @code
 268          *     array(
 269          *         'op'                  => 'delete',
 270          *         'src'                 => <storage path>,
 271          *         'ignoreMissingSource' => <boolean>
 272          *     )
 273          * @endcode
 274          *
 275          * f) Update metadata for a file within storage
 276          * @code
 277          *     array(
 278          *         'op'                  => 'describe',
 279          *         'src'                 => <storage path>,
 280          *         'headers'             => <HTTP header name/value map>
 281          *     )
 282          * @endcode
 283          *
 284          * g) Do nothing (no-op)
 285          * @code
 286          *     array(
 287          *         'op'                  => 'null',
 288          *     )
 289          * @endcode
 290          *
 291          * Boolean flags for operations (operation-specific):
 292          *   - ignoreMissingSource : The operation will simply succeed and do
 293          *                           nothing if the source file does not exist.
 294          *   - overwrite           : Any destination file will be overwritten.
 295          *   - overwriteSame       : If a file already exists at the destination with the
 296          *                           same contents, then do nothing to the destination file
 297          *                           instead of giving an error. This does not compare headers.
 298          *                           This option is ignored if 'overwrite' is already provided.
 299          *   - headers             : If supplied, the result of merging these headers with any
 300          *                           existing source file headers (replacing conflicting ones)
 301          *                           will be set as the destination file headers. Headers are
 302          *                           deleted if their value is set to the empty string. When a
 303          *                           file has headers they are included in responses to GET and
 304          *                           HEAD requests to the backing store for that file.
 305          *                           Header values should be no larger than 255 bytes, except for
 306          *                           Content-Disposition. The system might ignore or truncate any
 307          *                           headers that are too long to store (exact limits will vary).
 308          *                           Backends that don't support metadata ignore this. (since 1.21)
 309          *
 310          * $opts is an associative of boolean flags, including:
 311          *   - force               : Operation precondition errors no longer trigger an abort.
 312          *                           Any remaining operations are still attempted. Unexpected
 313          *                           failures may still cause remaining operations to be aborted.
 314          *   - nonLocking          : No locks are acquired for the operations.
 315          *                           This can increase performance for non-critical writes.
 316          *                           This has no effect unless the 'force' flag is set.
 317          *   - nonJournaled        : Don't log this operation batch in the file journal.
 318          *                           This limits the ability of recovery scripts.
 319          *   - parallelize         : Try to do operations in parallel when possible.
 320          *   - bypassReadOnly      : Allow writes in read-only mode. (since 1.20)
 321          *   - preserveCache       : Don't clear the process cache before checking files.
 322          *                           This should only be used if all entries in the process
 323          *                           cache were added after the files were already locked. (since 1.20)
 324          *
 325          * @remarks Remarks on locking:
 326          * File system paths given to operations should refer to files that are
 327          * already locked or otherwise safe from modification from other processes.
 328          * Normally these files will be new temp files, which should be adequate.
 329          *
 330          * @par Return value:
 331          *
 332          * This returns a Status, which contains all warnings and fatals that occurred
 333          * during the operation. The 'failCount', 'successCount', and 'success' members
 334          * will reflect each operation attempted.
 335          *
 336          * The status will be "OK" unless:
 337          *   - a) unexpected operation errors occurred (network partitions, disk full...)
 338          *   - b) significant operation errors occurred and 'force' was not set
 339          *
 340          * @param array $ops List of operations to execute in order
 341          * @param array $opts Batch operation options
 342          * @return Status
 343          */
 344         final public function doOperations( array $ops, array $opts = array() ) {
 345                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 346                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 347                 }
 348                 if ( !count( $ops ) ) {
 349                         return Status::newGood(); // nothing to do
 350                 }
 351                 if ( empty( $opts['force'] ) ) { // sanity
 352                         unset( $opts['nonLocking'] );
 353                 }
 354                 foreach ( $ops as &$op ) {
 355                         if ( isset( $op['disposition'] ) ) { // b/c (MW 1.20)
 356                                 $op['headers']['Content-Disposition'] = $op['disposition'];
 357                         }
 358                 }
 359                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 360                 return $this->doOperationsInternal( $ops, $opts );
 361         }
 362
 363         /**
 364          * @see FileBackend::doOperations()
 365          */
 366         abstract protected function doOperationsInternal( array $ops, array $opts );
 367
 368         /**
 369          * Same as doOperations() except it takes a single operation.
 370          * If you are doing a batch of operations that should either
 371          * all succeed or all fail, then use that function instead.
 372          *
 373          * @see FileBackend::doOperations()
 374          *
 375          * @param array $op Operation
 376          * @param array $opts Operation options
 377          * @return Status
 378          */
 379         final public function doOperation( array $op, array $opts = array() ) {
 380                 return $this->doOperations( array( $op ), $opts );
 381         }
 382
 383         /**
 384          * Performs a single create operation.
 385          * This sets $params['op'] to 'create' and passes it to doOperation().
 386          *
 387          * @see FileBackend::doOperation()
 388          *
 389          * @param array $params Operation parameters
 390          * @param array $opts Operation options
 391          * @return Status
 392          */
 393         final public function create( array $params, array $opts = array() ) {
 394                 return $this->doOperation( array( 'op' => 'create' ) + $params, $opts );
 395         }
 396
 397         /**
 398          * Performs a single store operation.
 399          * This sets $params['op'] to 'store' and passes it to doOperation().
 400          *
 401          * @see FileBackend::doOperation()
 402          *
 403          * @param array $params Operation parameters
 404          * @param array $opts Operation options
 405          * @return Status
 406          */
 407         final public function store( array $params, array $opts = array() ) {
 408                 return $this->doOperation( array( 'op' => 'store' ) + $params, $opts );
 409         }
 410
 411         /**
 412          * Performs a single copy operation.
 413          * This sets $params['op'] to 'copy' and passes it to doOperation().
 414          *
 415          * @see FileBackend::doOperation()
 416          *
 417          * @param array $params Operation parameters
 418          * @param array $opts Operation options
 419          * @return Status
 420          */
 421         final public function copy( array $params, array $opts = array() ) {
 422                 return $this->doOperation( array( 'op' => 'copy' ) + $params, $opts );
 423         }
 424
 425         /**
 426          * Performs a single move operation.
 427          * This sets $params['op'] to 'move' and passes it to doOperation().
 428          *
 429          * @see FileBackend::doOperation()
 430          *
 431          * @param array $params Operation parameters
 432          * @param array $opts Operation options
 433          * @return Status
 434          */
 435         final public function move( array $params, array $opts = array() ) {
 436                 return $this->doOperation( array( 'op' => 'move' ) + $params, $opts );
 437         }
 438
 439         /**
 440          * Performs a single delete operation.
 441          * This sets $params['op'] to 'delete' and passes it to doOperation().
 442          *
 443          * @see FileBackend::doOperation()
 444          *
 445          * @param array $params Operation parameters
 446          * @param array $opts Operation options
 447          * @return Status
 448          */
 449         final public function delete( array $params, array $opts = array() ) {
 450                 return $this->doOperation( array( 'op' => 'delete' ) + $params, $opts );
 451         }
 452
 453         /**
 454          * Performs a single describe operation.
 455          * This sets $params['op'] to 'describe' and passes it to doOperation().
 456          *
 457          * @see FileBackend::doOperation()
 458          *
 459          * @param array $params Operation parameters
 460          * @param array $opts Operation options
 461          * @return Status
 462          * @since 1.21
 463          */
 464         final public function describe( array $params, array $opts = array() ) {
 465                 return $this->doOperation( array( 'op' => 'describe' ) + $params, $opts );
 466         }
 467
 468         /**
 469          * Perform a set of independent file operations on some files.
 470          *
 471          * This does no locking, nor journaling, and possibly no stat calls.
 472          * Any destination files that already exist will be overwritten.
 473          * This should *only* be used on non-original files, like cache files.
 474          *
 475          * Supported operations and their parameters:
 476          *  - create
 477          *  - store
 478          *  - copy
 479          *  - move
 480          *  - delete
 481          *  - describe (since 1.21)
 482          *  - null
 483          *
 484          * a) Create a new file in storage with the contents of a string
 485          * @code
 486          *     array(
 487          *         'op'                  => 'create',
 488          *         'dst'                 => <storage path>,
 489          *         'content'             => <string of new file contents>,
 490          *         'headers'             => <HTTP header name/value map> # since 1.21
 491          *     )
 492          * @endcode
 493          *
 494          * b) Copy a file system file into storage
 495          * @code
 496          *     array(
 497          *         'op'                  => 'store',
 498          *         'src'                 => <file system path>,
 499          *         'dst'                 => <storage path>,
 500          *         'headers'             => <HTTP header name/value map> # since 1.21
 501          *     )
 502          * @endcode
 503          *
 504          * c) Copy a file within storage
 505          * @code
 506          *     array(
 507          *         'op'                  => 'copy',
 508          *         'src'                 => <storage path>,
 509          *         'dst'                 => <storage path>,
 510          *         'ignoreMissingSource' => <boolean>, # since 1.21
 511          *         'headers'             => <HTTP header name/value map> # since 1.21
 512          *     )
 513          * @endcode
 514          *
 515          * d) Move a file within storage
 516          * @code
 517          *     array(
 518          *         'op'                  => 'move',
 519          *         'src'                 => <storage path>,
 520          *         'dst'                 => <storage path>,
 521          *         'ignoreMissingSource' => <boolean>, # since 1.21
 522          *         'headers'             => <HTTP header name/value map> # since 1.21
 523          *     )
 524          * @endcode
 525          *
 526          * e) Delete a file within storage
 527          * @code
 528          *     array(
 529          *         'op'                  => 'delete',
 530          *         'src'                 => <storage path>,
 531          *         'ignoreMissingSource' => <boolean>
 532          *     )
 533          * @endcode
 534          *
 535          * f) Update metadata for a file within storage
 536          * @code
 537          *     array(
 538          *         'op'                  => 'describe',
 539          *         'src'                 => <storage path>,
 540          *         'headers'             => <HTTP header name/value map>
 541          *     )
 542          * @endcode
 543          *
 544          * g) Do nothing (no-op)
 545          * @code
 546          *     array(
 547          *         'op'                  => 'null',
 548          *     )
 549          * @endcode
 550          *
 551          * @par Boolean flags for operations (operation-specific):
 552          *   - ignoreMissingSource : The operation will simply succeed and do
 553          *                           nothing if the source file does not exist.
 554          *   - headers             : If supplied with a header name/value map, the backend will
 555          *                           reply with these headers when GETs/HEADs of the destination
 556          *                           file are made. Header values should be smaller than 256 bytes.
 557          *                           Content-Disposition headers can be longer, though the system
 558          *                           might ignore or truncate ones that are too long to store.
 559          *                           Existing headers will remain, but these will replace any
 560          *                           conflicting previous headers, and headers will be removed
 561          *                           if they are set to an empty string.
 562          *                           Backends that don't support metadata ignore this. (since 1.21)
 563          *
 564          * $opts is an associative of boolean flags, including:
 565          *   - bypassReadOnly      : Allow writes in read-only mode (since 1.20)
 566          *
 567          * @par Return value:
 568          * This returns a Status, which contains all warnings and fatals that occurred
 569          * during the operation. The 'failCount', 'successCount', and 'success' members
 570          * will reflect each operation attempted for the given files. The status will be
 571          * considered "OK" as long as no fatal errors occurred.
 572          *
 573          * @param array $ops Set of operations to execute
 574          * @param array $opts Batch operation options
 575          * @return Status
 576          * @since 1.20
 577          */
 578         final public function doQuickOperations( array $ops, array $opts = array() ) {
 579                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 580                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 581                 }
 582                 if ( !count( $ops ) ) {
 583                         return Status::newGood(); // nothing to do
 584                 }
 585                 foreach ( $ops as &$op ) {
 586                         $op['overwrite'] = true; // avoids RTTs in key/value stores
 587                         if ( isset( $op['disposition'] ) ) { // b/c (MW 1.20)
 588                                 $op['headers']['Content-Disposition'] = $op['disposition'];
 589                         }
 590                 }
 591                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 592                 return $this->doQuickOperationsInternal( $ops );
 593         }
 594
 595         /**
 596          * @see FileBackend::doQuickOperations()
 597          * @since 1.20
 598          */
 599         abstract protected function doQuickOperationsInternal( array $ops );
 600
 601         /**
 602          * Same as doQuickOperations() except it takes a single operation.
 603          * If you are doing a batch of operations, then use that function instead.
 604          *
 605          * @see FileBackend::doQuickOperations()
 606          *
 607          * @param array $op Operation
 608          * @return Status
 609          * @since 1.20
 610          */
 611         final public function doQuickOperation( array $op ) {
 612                 return $this->doQuickOperations( array( $op ) );
 613         }
 614
 615         /**
 616          * Performs a single quick create operation.
 617          * This sets $params['op'] to 'create' and passes it to doQuickOperation().
 618          *
 619          * @see FileBackend::doQuickOperation()
 620          *
 621          * @param array $params Operation parameters
 622          * @return Status
 623          * @since 1.20
 624          */
 625         final public function quickCreate( array $params ) {
 626                 return $this->doQuickOperation( array( 'op' => 'create' ) + $params );
 627         }
 628
 629         /**
 630          * Performs a single quick store operation.
 631          * This sets $params['op'] to 'store' and passes it to doQuickOperation().
 632          *
 633          * @see FileBackend::doQuickOperation()
 634          *
 635          * @param array $params Operation parameters
 636          * @return Status
 637          * @since 1.20
 638          */
 639         final public function quickStore( array $params ) {
 640                 return $this->doQuickOperation( array( 'op' => 'store' ) + $params );
 641         }
 642
 643         /**
 644          * Performs a single quick copy operation.
 645          * This sets $params['op'] to 'copy' and passes it to doQuickOperation().
 646          *
 647          * @see FileBackend::doQuickOperation()
 648          *
 649          * @param array $params Operation parameters
 650          * @return Status
 651          * @since 1.20
 652          */
 653         final public function quickCopy( array $params ) {
 654                 return $this->doQuickOperation( array( 'op' => 'copy' ) + $params );
 655         }
 656
 657         /**
 658          * Performs a single quick move operation.
 659          * This sets $params['op'] to 'move' and passes it to doQuickOperation().
 660          *
 661          * @see FileBackend::doQuickOperation()
 662          *
 663          * @param array $params Operation parameters
 664          * @return Status
 665          * @since 1.20
 666          */
 667         final public function quickMove( array $params ) {
 668                 return $this->doQuickOperation( array( 'op' => 'move' ) + $params );
 669         }
 670
 671         /**
 672          * Performs a single quick delete operation.
 673          * This sets $params['op'] to 'delete' and passes it to doQuickOperation().
 674          *
 675          * @see FileBackend::doQuickOperation()
 676          *
 677          * @param array $params Operation parameters
 678          * @return Status
 679          * @since 1.20
 680          */
 681         final public function quickDelete( array $params ) {
 682                 return $this->doQuickOperation( array( 'op' => 'delete' ) + $params );
 683         }
 684
 685         /**
 686          * Performs a single quick describe operation.
 687          * This sets $params['op'] to 'describe' and passes it to doQuickOperation().
 688          *
 689          * @see FileBackend::doQuickOperation()
 690          *
 691          * @param array $params Operation parameters
 692          * @return Status
 693          * @since 1.21
 694          */
 695         final public function quickDescribe( array $params ) {
 696                 return $this->doQuickOperation( array( 'op' => 'describe' ) + $params );
 697         }
 698
 699         /**
 700          * Concatenate a list of storage files into a single file system file.
 701          * The target path should refer to a file that is already locked or
 702          * otherwise safe from modification from other processes. Normally,
 703          * the file will be a new temp file, which should be adequate.
 704          *
 705          * @param array $params Operation parameters, include:
 706          *   - srcs        : ordered source storage paths (e.g. chunk1, chunk2, ...)
 707          *   - dst         : file system path to 0-byte temp file
 708          *   - parallelize : try to do operations in parallel when possible
 709          * @return Status
 710          */
 711         abstract public function concatenate( array $params );
 712
 713         /**
 714          * Prepare a storage directory for usage.
 715          * This will create any required containers and parent directories.
 716          * Backends using key/value stores only need to create the container.
 717          *
 718          * The 'noAccess' and 'noListing' parameters works the same as in secure(),
 719          * except they are only applied *if* the directory/container had to be created.
 720          * These flags should always be set for directories that have private files.
 721          * However, setting them is not guaranteed to actually do anything.
 722          * Additional server configuration may be needed to achieve the desired effect.
 723          *
 724          * @param array $params Parameters include:
 725          *   - dir            : storage directory
 726          *   - noAccess       : try to deny file access (since 1.20)
 727          *   - noListing      : try to deny file listing (since 1.20)
 728          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 729          * @return Status
 730          */
 731         final public function prepare( array $params ) {
 732                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 733                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 734                 }
 735                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 736                 return $this->doPrepare( $params );
 737         }
 738
 739         /**
 740          * @see FileBackend::prepare()
 741          */
 742         abstract protected function doPrepare( array $params );
 743
 744         /**
 745          * Take measures to block web access to a storage directory and
 746          * the container it belongs to. FS backends might add .htaccess
 747          * files whereas key/value store backends might revoke container
 748          * access to the storage user representing end-users in web requests.
 749          *
 750          * This is not guaranteed to actually make files or listings publically hidden.
 751          * Additional server configuration may be needed to achieve the desired effect.
 752          *
 753          * @param array $params Parameters include:
 754          *   - dir            : storage directory
 755          *   - noAccess       : try to deny file access
 756          *   - noListing      : try to deny file listing
 757          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 758          * @return Status
 759          */
 760         final public function secure( array $params ) {
 761                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 762                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 763                 }
 764                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 765                 return $this->doSecure( $params );
 766         }
 767
 768         /**
 769          * @see FileBackend::secure()
 770          */
 771         abstract protected function doSecure( array $params );
 772
 773         /**
 774          * Remove measures to block web access to a storage directory and
 775          * the container it belongs to. FS backends might remove .htaccess
 776          * files whereas key/value store backends might grant container
 777          * access to the storage user representing end-users in web requests.
 778          * This essentially can undo the result of secure() calls.
 779          *
 780          * This is not guaranteed to actually make files or listings publically viewable.
 781          * Additional server configuration may be needed to achieve the desired effect.
 782          *
 783          * @param array $params Parameters include:
 784          *   - dir            : storage directory
 785          *   - access         : try to allow file access
 786          *   - listing        : try to allow file listing
 787          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 788          * @return Status
 789          * @since 1.20
 790          */
 791         final public function publish( array $params ) {
 792                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 793                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 794                 }
 795                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 796                 return $this->doPublish( $params );
 797         }
 798
 799         /**
 800          * @see FileBackend::publish()
 801          */
 802         abstract protected function doPublish( array $params );
 803
 804         /**
 805          * Delete a storage directory if it is empty.
 806          * Backends using key/value stores may do nothing unless the directory
 807          * is that of an empty container, in which case it will be deleted.
 808          *
 809          * @param array $params Parameters include:
 810          *   - dir            : storage directory
 811          *   - recursive      : recursively delete empty subdirectories first (since 1.20)
 812          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 813          * @return Status
 814          */
 815         final public function clean( array $params ) {
 816                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 817                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 818                 }
 819                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 820                 return $this->doClean( $params );
 821         }
 822
 823         /**
 824          * @see FileBackend::clean()
 825          */
 826         abstract protected function doClean( array $params );
 827
 828         /**
 829          * Enter file operation scope.
 830          * This just makes PHP ignore user aborts/disconnects until the return
 831          * value leaves scope. This returns null and does nothing in CLI mode.
 832          *
 833          * @return ScopedCallback|null
 834          */
 835         final protected function getScopedPHPBehaviorForOps() {
 836                 if ( PHP_SAPI != 'cli' ) { // http://bugs.php.net/bug.php?id=47540
 837                         $old = ignore_user_abort( true ); // avoid half-finished operations
 838                         return new ScopedCallback( function () use ( $old ) {
 839                                 ignore_user_abort( $old );
 840                         } );
 841                 }
 842
 843                 return null;
 844         }
 845
 846         /**
 847          * Check if a file exists at a storage path in the backend.
 848          * This returns false if only a directory exists at the path.
 849          *
 850          * @param array $params Parameters include:
 851          *   - src    : source storage path
 852          *   - latest : use the latest available data
 853          * @return bool|null Returns null on failure
 854          */
 855         abstract public function fileExists( array $params );
 856
 857         /**
 858          * Get the last-modified timestamp of the file at a storage path.
 859          *
 860          * @param array $params Parameters include:
 861          *   - src    : source storage path
 862          *   - latest : use the latest available data
 863          * @return string|bool TS_MW timestamp or false on failure
 864          */
 865         abstract public function getFileTimestamp( array $params );
 866
 867         /**
 868          * Get the contents of a file at a storage path in the backend.
 869          * This should be avoided for potentially large files.
 870          *
 871          * @param array $params Parameters include:
 872          *   - src    : source storage path
 873          *   - latest : use the latest available data
 874          * @return string|bool Returns false on failure
 875          */
 876         final public function getFileContents( array $params ) {
 877                 $contents = $this->getFileContentsMulti(
 878                         array( 'srcs' => array( $params['src'] ) ) + $params );
 879
 880                 return $contents[$params['src']];
 881         }
 882
 883         /**
 884          * Like getFileContents() except it takes an array of storage paths
 885          * and returns a map of storage paths to strings (or null on failure).
 886          * The map keys (paths) are in the same order as the provided list of paths.
 887          *
 888          * @see FileBackend::getFileContents()
 889          *
 890          * @param array $params Parameters include:
 891          *   - srcs        : list of source storage paths
 892          *   - latest      : use the latest available data
 893          *   - parallelize : try to do operations in parallel when possible
 894          * @return array Map of (path name => string or false on failure)
 895          * @since 1.20
 896          */
 897         abstract public function getFileContentsMulti( array $params );
 898
 899         /**
 900          * Get the size (bytes) of a file at a storage path in the backend.
 901          *
 902          * @param array $params Parameters include:
 903          *   - src    : source storage path
 904          *   - latest : use the latest available data
 905          * @return int|bool Returns false on failure
 906          */
 907         abstract public function getFileSize( array $params );
 908
 909         /**
 910          * Get quick information about a file at a storage path in the backend.
 911          * If the file does not exist, then this returns false.
 912          * Otherwise, the result is an associative array that includes:
 913          *   - mtime  : the last-modified timestamp (TS_MW)
 914          *   - size   : the file size (bytes)
 915          * Additional values may be included for internal use only.
 916          *
 917          * @param array $params Parameters include:
 918          *   - src    : source storage path
 919          *   - latest : use the latest available data
 920          * @return array|bool|null Returns null on failure
 921          */
 922         abstract public function getFileStat( array $params );
 923
 924         /**
 925          * Get a SHA-1 hash of the file at a storage path in the backend.
 926          *
 927          * @param array $params Parameters include:
 928          *   - src    : source storage path
 929          *   - latest : use the latest available data
 930          * @return string|bool Hash string or false on failure
 931          */
 932         abstract public function getFileSha1Base36( array $params );
 933
 934         /**
 935          * Get the properties of the file at a storage path in the backend.
 936          * This gives the result of FSFile::getProps() on a local copy of the file.
 937          *
 938          * @param array $params Parameters include:
 939          *   - src    : source storage path
 940          *   - latest : use the latest available data
 941          * @return array Returns FSFile::placeholderProps() on failure
 942          */
 943         abstract public function getFileProps( array $params );
 944
 945         /**
 946          * Stream the file at a storage path in the backend.
 947          * If the file does not exists, an HTTP 404 error will be given.
 948          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
 949          * will be sent if streaming began, while none will be sent otherwise.
 950          * Implementations should flush the output buffer before sending data.
 951          *
 952          * @param array $params Parameters include:
 953          *   - src     : source storage path
 954          *   - headers : list of additional HTTP headers to send on success
 955          *   - latest  : use the latest available data
 956          * @return Status
 957          */
 958         abstract public function streamFile( array $params );
 959
 960         /**
 961          * Returns a file system file, identical to the file at a storage path.
 962          * The file returned is either:
 963          *   - a) A local copy of the file at a storage path in the backend.
 964          *        The temporary copy will have the same extension as the source.
 965          *   - b) An original of the file at a storage path in the backend.
 966          * Temporary files may be purged when the file object falls out of scope.
 967          *
 968          * Write operations should *never* be done on this file as some backends
 969          * may do internal tracking or may be instances of FileBackendMultiWrite.
 970          * In that later case, there are copies of the file that must stay in sync.
 971          * Additionally, further calls to this function may return the same file.
 972          *
 973          * @param array $params Parameters include:
 974          *   - src    : source storage path
 975          *   - latest : use the latest available data
 976          * @return FSFile|null Returns null on failure
 977          */
 978         final public function getLocalReference( array $params ) {
 979                 $fsFiles = $this->getLocalReferenceMulti(
 980                         array( 'srcs' => array( $params['src'] ) ) + $params );
 981
 982                 return $fsFiles[$params['src']];
 983         }
 984
 985         /**
 986          * Like getLocalReference() except it takes an array of storage paths
 987          * and returns a map of storage paths to FSFile objects (or null on failure).
 988          * The map keys (paths) are in the same order as the provided list of paths.
 989          *
 990          * @see FileBackend::getLocalReference()
 991          *
 992          * @param array $params Parameters include:
 993          *   - srcs        : list of source storage paths
 994          *   - latest      : use the latest available data
 995          *   - parallelize : try to do operations in parallel when possible
 996          * @return array Map of (path name => FSFile or null on failure)
 997          * @since 1.20
 998          */
 999         abstract public function getLocalReferenceMulti( array $params );
1000
1001         /**
1002          * Get a local copy on disk of the file at a storage path in the backend.
1003          * The temporary copy will have the same file extension as the source.
1004          * Temporary files may be purged when the file object falls out of scope.
1005          *
1006          * @param array $params Parameters include:
1007          *   - src    : source storage path
1008          *   - latest : use the latest available data
1009          * @return TempFSFile|null Returns null on failure
1010          */
1011         final public function getLocalCopy( array $params ) {
1012                 $tmpFiles = $this->getLocalCopyMulti(
1013                         array( 'srcs' => array( $params['src'] ) ) + $params );
1014
1015                 return $tmpFiles[$params['src']];
1016         }
1017
1018         /**
1019          * Like getLocalCopy() except it takes an array of storage paths and
1020          * returns a map of storage paths to TempFSFile objects (or null on failure).
1021          * The map keys (paths) are in the same order as the provided list of paths.
1022          *
1023          * @see FileBackend::getLocalCopy()
1024          *
1025          * @param array $params Parameters include:
1026          *   - srcs        : list of source storage paths
1027          *   - latest      : use the latest available data
1028          *   - parallelize : try to do operations in parallel when possible
1029          * @return array Map of (path name => TempFSFile or null on failure)
1030          * @since 1.20
1031          */
1032         abstract public function getLocalCopyMulti( array $params );
1033
1034         /**
1035          * Return an HTTP URL to a given file that requires no authentication to use.
1036          * The URL may be pre-authenticated (via some token in the URL) and temporary.
1037          * This will return null if the backend cannot make an HTTP URL for the file.
1038          *
1039          * This is useful for key/value stores when using scripts that seek around
1040          * large files and those scripts (and the backend) support HTTP Range headers.
1041          * Otherwise, one would need to use getLocalReference(), which involves loading
1042          * the entire file on to local disk.
1043          *
1044          * @param array $params Parameters include:
1045          *   - src : source storage path
1046          *   - ttl : lifetime (seconds) if pre-authenticated; default is 1 day
1047          * @return string|null
1048          * @since 1.21
1049          */
1050         abstract public function getFileHttpUrl( array $params );
1051
1052         /**
1053          * Check if a directory exists at a given storage path.
1054          * Backends using key/value stores will check if the path is a
1055          * virtual directory, meaning there are files under the given directory.
1056          *
1057          * Storage backends with eventual consistency might return stale data.
1058          *
1059          * @param array $params Parameters include:
1060          *   - dir : storage directory
1061          * @return bool|null Returns null on failure
1062          * @since 1.20
1063          */
1064         abstract public function directoryExists( array $params );
1065
1066         /**
1067          * Get an iterator to list *all* directories under a storage directory.
1068          * If the directory is of the form "mwstore://backend/container",
1069          * then all directories in the container will be listed.
1070          * If the directory is of form "mwstore://backend/container/dir",
1071          * then all directories directly under that directory will be listed.
1072          * Results will be storage directories relative to the given directory.
1073          *
1074          * Storage backends with eventual consistency might return stale data.
1075          *
1076          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1077          *
1078          * @param array $params Parameters include:
1079          *   - dir     : storage directory
1080          *   - topOnly : only return direct child dirs of the directory
1081          * @return Traversable|Array|null Returns null on failure
1082          * @since 1.20
1083          */
1084         abstract public function getDirectoryList( array $params );
1085
1086         /**
1087          * Same as FileBackend::getDirectoryList() except only lists
1088          * directories that are immediately under the given directory.
1089          *
1090          * Storage backends with eventual consistency might return stale data.
1091          *
1092          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1093          *
1094          * @param array $params Parameters include:
1095          *   - dir : storage directory
1096          * @return Traversable|Array|null Returns null on failure
1097          * @since 1.20
1098          */
1099         final public function getTopDirectoryList( array $params ) {
1100                 return $this->getDirectoryList( array( 'topOnly' => true ) + $params );
1101         }
1102
1103         /**
1104          * Get an iterator to list *all* stored files under a storage directory.
1105          * If the directory is of the form "mwstore://backend/container",
1106          * then all files in the container will be listed.
1107          * If the directory is of form "mwstore://backend/container/dir",
1108          * then all files under that directory will be listed.
1109          * Results will be storage paths relative to the given directory.
1110          *
1111          * Storage backends with eventual consistency might return stale data.
1112          *
1113          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1114          *
1115          * @param array $params Parameters include:
1116          *   - dir        : storage directory
1117          *   - topOnly    : only return direct child files of the directory (since 1.20)
1118          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1119          * @return Traversable|Array|null Returns null on failure
1120          */
1121         abstract public function getFileList( array $params );
1122
1123         /**
1124          * Same as FileBackend::getFileList() except only lists
1125          * files that are immediately under the given directory.
1126          *
1127          * Storage backends with eventual consistency might return stale data.
1128          *
1129          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1130          *
1131          * @param array $params Parameters include:
1132          *   - dir        : storage directory
1133          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1134          * @return Traversable|Array|null Returns null on failure
1135          * @since 1.20
1136          */
1137         final public function getTopFileList( array $params ) {
1138                 return $this->getFileList( array( 'topOnly' => true ) + $params );
1139         }
1140
1141         /**
1142          * Preload persistent file stat and property cache into in-process cache.
1143          * This should be used when stat calls will be made on a known list of a many files.
1144          *
1145          * @param array $paths Storage paths
1146          */
1147         public function preloadCache( array $paths ) {
1148         }
1149
1150         /**
1151          * Invalidate any in-process file stat and property cache.
1152          * If $paths is given, then only the cache for those files will be cleared.
1153          *
1154          * @param array $paths Storage paths (optional)
1155          */
1156         public function clearCache( array $paths = null ) {
1157         }
1158
1159         /**
1160          * Lock the files at the given storage paths in the backend.
1161          * This will either lock all the files or none (on failure).
1162          *
1163          * Callers should consider using getScopedFileLocks() instead.
1164          *
1165          * @param array $paths Storage paths
1166          * @param int $type LockManager::LOCK_* constant
1167          * @return Status
1168          */
1169         final public function lockFiles( array $paths, $type ) {
1170                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1171
1172                 return $this->lockManager->lock( $paths, $type );
1173         }
1174
1175         /**
1176          * Unlock the files at the given storage paths in the backend.
1177          *
1178          * @param array $paths Storage paths
1179          * @param int $type LockManager::LOCK_* constant
1180          * @return Status
1181          */
1182         final public function unlockFiles( array $paths, $type ) {
1183                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1184
1185                 return $this->lockManager->unlock( $paths, $type );
1186         }
1187
1188         /**
1189          * Lock the files at the given storage paths in the backend.
1190          * This will either lock all the files or none (on failure).
1191          * On failure, the status object will be updated with errors.
1192          *
1193          * Once the return value goes out scope, the locks will be released and
1194          * the status updated. Unlock fatals will not change the status "OK" value.
1195          *
1196          * @see ScopedLock::factory()
1197          *
1198          * @param array $paths List of storage paths or map of lock types to path lists
1199          * @param int|string $type LockManager::LOCK_* constant or "mixed"
1200          * @param Status $status Status to update on lock/unlock
1201          * @return ScopedLock|null Returns null on failure
1202          */
1203         final public function getScopedFileLocks( array $paths, $type, Status $status ) {
1204                 if ( $type === 'mixed' ) {
1205                         foreach ( $paths as &$typePaths ) {
1206                                 $typePaths = array_map( 'FileBackend::normalizeStoragePath', $typePaths );
1207                         }
1208                 } else {
1209                         $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1210                 }
1211
1212                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status );
1213         }
1214
1215         /**
1216          * Get an array of scoped locks needed for a batch of file operations.
1217          *
1218          * Normally, FileBackend::doOperations() handles locking, unless
1219          * the 'nonLocking' param is passed in. This function is useful if you
1220          * want the files to be locked for a broader scope than just when the
1221          * files are changing. For example, if you need to update DB metadata,
1222          * you may want to keep the files locked until finished.
1223          *
1224          * @see FileBackend::doOperations()
1225          *
1226          * @param array $ops List of file operations to FileBackend::doOperations()
1227          * @param Status $status Status to update on lock/unlock
1228          * @return array List of ScopedFileLocks or null values
1229          * @since 1.20
1230          */
1231         abstract public function getScopedLocksForOps( array $ops, Status $status );
1232
1233         /**
1234          * Get the root storage path of this backend.
1235          * All container paths are "subdirectories" of this path.
1236          *
1237          * @return string Storage path
1238          * @since 1.20
1239          */
1240         final public function getRootStoragePath() {
1241                 return "mwstore://{$this->name}";
1242         }
1243
1244         /**
1245          * Get the storage path for the given container for this backend
1246          *
1247          * @param string $container Container name
1248          * @return string Storage path
1249          * @since 1.21
1250          */
1251         final public function getContainerStoragePath( $container ) {
1252                 return $this->getRootStoragePath() . "/{$container}";
1253         }
1254
1255         /**
1256          * Get the file journal object for this backend
1257          *
1258          * @return FileJournal
1259          */
1260         final public function getJournal() {
1261                 return $this->fileJournal;
1262         }
1263
1264         /**
1265          * Check if a given path is a "mwstore://" path.
1266          * This does not do any further validation or any existence checks.
1267          *
1268          * @param string $path
1269          * @return bool
1270          */
1271         final public static function isStoragePath( $path ) {
1272                 return ( strpos( $path, 'mwstore://' ) === 0 );
1273         }
1274
1275         /**
1276          * Split a storage path into a backend name, a container name,
1277          * and a relative file path. The relative path may be the empty string.
1278          * This does not do any path normalization or traversal checks.
1279          *
1280          * @param string $storagePath
1281          * @return array (backend, container, rel object) or (null, null, null)
1282          */
1283         final public static function splitStoragePath( $storagePath ) {
1284                 if ( self::isStoragePath( $storagePath ) ) {
1285                         // Remove the "mwstore://" prefix and split the path
1286                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
1287                         if ( count( $parts ) >= 2 && $parts[0] != '' && $parts[1] != '' ) {
1288                                 if ( count( $parts ) == 3 ) {
1289                                         return $parts; // e.g. "backend/container/path"
1290                                 } else {
1291                                         return array( $parts[0], $parts[1], '' ); // e.g. "backend/container"
1292                                 }
1293                         }
1294                 }
1295
1296                 return array( null, null, null );
1297         }
1298
1299         /**
1300          * Normalize a storage path by cleaning up directory separators.
1301          * Returns null if the path is not of the format of a valid storage path.
1302          *
1303          * @param string $storagePath
1304          * @return string|null
1305          */
1306         final public static function normalizeStoragePath( $storagePath ) {
1307                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
1308                 if ( $relPath !== null ) { // must be for this backend
1309                         $relPath = self::normalizeContainerPath( $relPath );
1310                         if ( $relPath !== null ) {
1311                                 return ( $relPath != '' )
1312                                         ? "mwstore://{$backend}/{$container}/{$relPath}"
1313                                         : "mwstore://{$backend}/{$container}";
1314                         }
1315                 }
1316
1317                 return null;
1318         }
1319
1320         /**
1321          * Get the parent storage directory of a storage path.
1322          * This returns a path like "mwstore://backend/container",
1323          * "mwstore://backend/container/...", or null if there is no parent.
1324          *
1325          * @param string $storagePath
1326          * @return string|null
1327          */
1328         final public static function parentStoragePath( $storagePath ) {
1329                 $storagePath = dirname( $storagePath );
1330                 list( , , $rel ) = self::splitStoragePath( $storagePath );
1331
1332                 return ( $rel === null ) ? null : $storagePath;
1333         }
1334
1335         /**
1336          * Get the final extension from a storage or FS path
1337          *
1338          * @param string $path
1339          * @return string
1340          */
1341         final public static function extensionFromPath( $path ) {
1342                 $i = strrpos( $path, '.' );
1343
1344                 return strtolower( $i ? substr( $path, $i + 1 ) : '' );
1345         }
1346
1347         /**
1348          * Check if a relative path has no directory traversals
1349          *
1350          * @param string $path
1351          * @return bool
1352          * @since 1.20
1353          */
1354         final public static function isPathTraversalFree( $path ) {
1355                 return ( self::normalizeContainerPath( $path ) !== null );
1356         }
1357
1358         /**
1359          * Build a Content-Disposition header value per RFC 6266.
1360          *
1361          * @param string $type One of (attachment, inline)
1362          * @param string $filename Suggested file name (should not contain slashes)
1363          * @throws MWException
1364          * @return string
1365          * @since 1.20
1366          */
1367         final public static function makeContentDisposition( $type, $filename = '' ) {
1368                 $parts = array();
1369
1370                 $type = strtolower( $type );
1371                 if ( !in_array( $type, array( 'inline', 'attachment' ) ) ) {
1372                         throw new MWException( "Invalid Content-Disposition type '$type'." );
1373                 }
1374                 $parts[] = $type;
1375
1376                 if ( strlen( $filename ) ) {
1377                         $parts[] = "filename*=UTF-8''" . rawurlencode( basename( $filename ) );
1378                 }
1379
1380                 return implode( ';', $parts );
1381         }
1382
1383         /**
1384          * Validate and normalize a relative storage path.
1385          * Null is returned if the path involves directory traversal.
1386          * Traversal is insecure for FS backends and broken for others.
1387          *
1388          * This uses the same traversal protection as Title::secureAndSplit().
1389          *
1390          * @param string $path Storage path relative to a container
1391          * @return string|null
1392          */
1393         final protected static function normalizeContainerPath( $path ) {
1394                 // Normalize directory separators
1395                 $path = strtr( $path, '\\', '/' );
1396                 // Collapse any consecutive directory separators
1397                 $path = preg_replace( '![/]{2,}!', '/', $path );
1398                 // Remove any leading directory separator
1399                 $path = ltrim( $path, '/' );
1400                 // Use the same traversal protection as Title::secureAndSplit()
1401                 if ( strpos( $path, '.' ) !== false ) {
1402                         if (
1403                                 $path === '.' ||
1404                                 $path === '..' ||
1405                                 strpos( $path, './' ) === 0 ||
1406                                 strpos( $path, '../' ) === 0 ||
1407                                 strpos( $path, '/./' ) !== false ||
1408                                 strpos( $path, '/../' ) !== false
1409                         ) {
1410                                 return null;
1411                         }
1412                 }
1413
1414                 return $path;
1415         }
1416 }
1417
1418 /**
1419  * @ingroup FileBackend
1420  * @since 1.22
1421  */
1422 class FileBackendError extends MWException {
1423 }