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         /** Bitfield flags for supported features */
 108         const ATTR_HEADERS = 1; // files can be tagged with standard HTTP headers
 109         const ATTR_METADATA = 2; // files can be stored with metadata key/values
 110         const ATTR_UNICODE_PATHS = 4; // files can have Unicode paths (not just ASCII)
 111
 112         /**
 113          * Create a new backend instance from configuration.
 114          * This should only be called from within FileBackendGroup.
 115          *
 116          * @param array $config Parameters include:
 117          *   - name        : The unique name of this backend.
 118          *                   This should consist of alphanumberic, '-', and '_' characters.
 119          *                   This name should not be changed after use (e.g. with journaling).
 120          *                   Note that the name is *not* used in actual container names.
 121          *   - wikiId      : Prefix to container names that is unique to this backend.
 122          *                   It should only consist of alphanumberic, '-', and '_' characters.
 123          *                   This ID is what avoids collisions if multiple logical backends
 124          *                   use the same storage system, so this should be set carefully.
 125          *   - lockManager : LockManager object to use for any file locking.
 126          *                   If not provided, then no file locking will be enforced.
 127          *   - fileJournal : FileJournal object to use for logging changes to files.
 128          *                   If not provided, then change journaling will be disabled.
 129          *   - readOnly    : Write operations are disallowed if this is a non-empty string.
 130          *                   It should be an explanation for the backend being read-only.
 131          *   - parallelize : When to do file operations in parallel (when possible).
 132          *                   Allowed values are "implicit", "explicit" and "off".
 133          *   - concurrency : How many file operations can be done in parallel.
 134          * @throws FileBackendException
 135          */
 136         public function __construct( array $config ) {
 137                 $this->name = $config['name'];
 138                 $this->wikiId = $config['wikiId']; // e.g. "my_wiki-en_"
 139                 if ( !preg_match( '!^[a-zA-Z0-9-_]{1,255}$!', $this->name ) ) {
 140                         throw new FileBackendException( "Backend name '{$this->name}' is invalid." );
 141                 } elseif ( !is_string( $this->wikiId ) ) {
 142                         throw new FileBackendException( "Backend wiki ID not provided for '{$this->name}'." );
 143                 }
 144                 $this->lockManager = isset( $config['lockManager'] )
 145                         ? $config['lockManager']
 146                         : new NullLockManager( array() );
 147                 $this->fileJournal = isset( $config['fileJournal'] )
 148                         ? $config['fileJournal']
 149                         : FileJournal::factory( array( 'class' => 'NullFileJournal' ), $this->name );
 150                 $this->readOnly = isset( $config['readOnly'] )
 151                         ? (string)$config['readOnly']
 152                         : '';
 153                 $this->parallelize = isset( $config['parallelize'] )
 154                         ? (string)$config['parallelize']
 155                         : 'off';
 156                 $this->concurrency = isset( $config['concurrency'] )
 157                         ? (int)$config['concurrency']
 158                         : 50;
 159         }
 160
 161         /**
 162          * Get the unique backend name.
 163          * We may have multiple different backends of the same type.
 164          * For example, we can have two Swift backends using different proxies.
 165          *
 166          * @return string
 167          */
 168         final public function getName() {
 169                 return $this->name;
 170         }
 171
 172         /**
 173          * Get the wiki identifier used for this backend (possibly empty).
 174          * Note that this might *not* be in the same format as wfWikiID().
 175          *
 176          * @return string
 177          * @since 1.20
 178          */
 179         final public function getWikiId() {
 180                 return $this->wikiId;
 181         }
 182
 183         /**
 184          * Check if this backend is read-only
 185          *
 186          * @return bool
 187          */
 188         final public function isReadOnly() {
 189                 return ( $this->readOnly != '' );
 190         }
 191
 192         /**
 193          * Get an explanatory message if this backend is read-only
 194          *
 195          * @return string|bool Returns false if the backend is not read-only
 196          */
 197         final public function getReadOnlyReason() {
 198                 return ( $this->readOnly != '' ) ? $this->readOnly : false;
 199         }
 200
 201         /**
 202          * Get the a bitfield of extra features supported by the backend medium
 203          *
 204          * @return int Bitfield of FileBackend::ATTR_* flags
 205          * @since 1.23
 206          */
 207         public function getFeatures() {
 208                 return self::ATTR_UNICODE_PATHS;
 209         }
 210
 211         /**
 212          * Check if the backend medium supports a field of extra features
 213          *
 214          * @param int $bitfield Bitfield of FileBackend::ATTR_* flags
 215          * @return bool
 216          * @since 1.23
 217          */
 218         final public function hasFeatures( $bitfield ) {
 219                 return ( $this->getFeatures() & $bitfield ) === $bitfield;
 220         }
 221
 222         /**
 223          * This is the main entry point into the backend for write operations.
 224          * Callers supply an ordered list of operations to perform as a transaction.
 225          * Files will be locked, the stat cache cleared, and then the operations attempted.
 226          * If any serious errors occur, all attempted operations will be rolled back.
 227          *
 228          * $ops is an array of arrays. The outer array holds a list of operations.
 229          * Each inner array is a set of key value pairs that specify an operation.
 230          *
 231          * Supported operations and their parameters. The supported actions are:
 232          *  - create
 233          *  - store
 234          *  - copy
 235          *  - move
 236          *  - delete
 237          *  - describe (since 1.21)
 238          *  - null
 239          *
 240          * a) Create a new file in storage with the contents of a string
 241          * @code
 242          *     array(
 243          *         'op'                  => 'create',
 244          *         'dst'                 => <storage path>,
 245          *         'content'             => <string of new file contents>,
 246          *         'overwrite'           => <boolean>,
 247          *         'overwriteSame'       => <boolean>,
 248          *         'headers'             => <HTTP header name/value map> # since 1.21
 249          *     );
 250          * @endcode
 251          *
 252          * b) Copy a file system file into storage
 253          * @code
 254          *     array(
 255          *         'op'                  => 'store',
 256          *         'src'                 => <file system path>,
 257          *         'dst'                 => <storage path>,
 258          *         'overwrite'           => <boolean>,
 259          *         'overwriteSame'       => <boolean>,
 260          *         'headers'             => <HTTP header name/value map> # since 1.21
 261          *     )
 262          * @endcode
 263          *
 264          * c) Copy a file within storage
 265          * @code
 266          *     array(
 267          *         'op'                  => 'copy',
 268          *         'src'                 => <storage path>,
 269          *         'dst'                 => <storage path>,
 270          *         'overwrite'           => <boolean>,
 271          *         'overwriteSame'       => <boolean>,
 272          *         'ignoreMissingSource' => <boolean>, # since 1.21
 273          *         'headers'             => <HTTP header name/value map> # since 1.21
 274          *     )
 275          * @endcode
 276          *
 277          * d) Move a file within storage
 278          * @code
 279          *     array(
 280          *         'op'                  => 'move',
 281          *         'src'                 => <storage path>,
 282          *         'dst'                 => <storage path>,
 283          *         'overwrite'           => <boolean>,
 284          *         'overwriteSame'       => <boolean>,
 285          *         'ignoreMissingSource' => <boolean>, # since 1.21
 286          *         'headers'             => <HTTP header name/value map> # since 1.21
 287          *     )
 288          * @endcode
 289          *
 290          * e) Delete a file within storage
 291          * @code
 292          *     array(
 293          *         'op'                  => 'delete',
 294          *         'src'                 => <storage path>,
 295          *         'ignoreMissingSource' => <boolean>
 296          *     )
 297          * @endcode
 298          *
 299          * f) Update metadata for a file within storage
 300          * @code
 301          *     array(
 302          *         'op'                  => 'describe',
 303          *         'src'                 => <storage path>,
 304          *         'headers'             => <HTTP header name/value map>
 305          *     )
 306          * @endcode
 307          *
 308          * g) Do nothing (no-op)
 309          * @code
 310          *     array(
 311          *         'op'                  => 'null',
 312          *     )
 313          * @endcode
 314          *
 315          * Boolean flags for operations (operation-specific):
 316          *   - ignoreMissingSource : The operation will simply succeed and do
 317          *                           nothing if the source file does not exist.
 318          *   - overwrite           : Any destination file will be overwritten.
 319          *   - overwriteSame       : If a file already exists at the destination with the
 320          *                           same contents, then do nothing to the destination file
 321          *                           instead of giving an error. This does not compare headers.
 322          *                           This option is ignored if 'overwrite' is already provided.
 323          *   - headers             : If supplied, the result of merging these headers with any
 324          *                           existing source file headers (replacing conflicting ones)
 325          *                           will be set as the destination file headers. Headers are
 326          *                           deleted if their value is set to the empty string. When a
 327          *                           file has headers they are included in responses to GET and
 328          *                           HEAD requests to the backing store for that file.
 329          *                           Header values should be no larger than 255 bytes, except for
 330          *                           Content-Disposition. The system might ignore or truncate any
 331          *                           headers that are too long to store (exact limits will vary).
 332          *                           Backends that don't support metadata ignore this. (since 1.21)
 333          *
 334          * $opts is an associative of boolean flags, including:
 335          *   - force               : Operation precondition errors no longer trigger an abort.
 336          *                           Any remaining operations are still attempted. Unexpected
 337          *                           failures may still cause remaining operations to be aborted.
 338          *   - nonLocking          : No locks are acquired for the operations.
 339          *                           This can increase performance for non-critical writes.
 340          *                           This has no effect unless the 'force' flag is set.
 341          *   - nonJournaled        : Don't log this operation batch in the file journal.
 342          *                           This limits the ability of recovery scripts.
 343          *   - parallelize         : Try to do operations in parallel when possible.
 344          *   - bypassReadOnly      : Allow writes in read-only mode. (since 1.20)
 345          *   - preserveCache       : Don't clear the process cache before checking files.
 346          *                           This should only be used if all entries in the process
 347          *                           cache were added after the files were already locked. (since 1.20)
 348          *
 349          * @remarks Remarks on locking:
 350          * File system paths given to operations should refer to files that are
 351          * already locked or otherwise safe from modification from other processes.
 352          * Normally these files will be new temp files, which should be adequate.
 353          *
 354          * @par Return value:
 355          *
 356          * This returns a Status, which contains all warnings and fatals that occurred
 357          * during the operation. The 'failCount', 'successCount', and 'success' members
 358          * will reflect each operation attempted.
 359          *
 360          * The status will be "OK" unless:
 361          *   - a) unexpected operation errors occurred (network partitions, disk full...)
 362          *   - b) significant operation errors occurred and 'force' was not set
 363          *
 364          * @param array $ops List of operations to execute in order
 365          * @param array $opts Batch operation options
 366          * @return Status
 367          */
 368         final public function doOperations( array $ops, array $opts = array() ) {
 369                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 370                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 371                 }
 372                 if ( !count( $ops ) ) {
 373                         return Status::newGood(); // nothing to do
 374                 }
 375                 if ( empty( $opts['force'] ) ) { // sanity
 376                         unset( $opts['nonLocking'] );
 377                 }
 378                 foreach ( $ops as &$op ) {
 379                         if ( isset( $op['disposition'] ) ) { // b/c (MW 1.20)
 380                                 $op['headers']['Content-Disposition'] = $op['disposition'];
 381                         }
 382                 }
 383                 /** @noinspection PhpUnusedLocalVariableInspection */
 384                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 385                 return $this->doOperationsInternal( $ops, $opts );
 386         }
 387
 388         /**
 389          * @see FileBackend::doOperations()
 390          */
 391         abstract protected function doOperationsInternal( array $ops, array $opts );
 392
 393         /**
 394          * Same as doOperations() except it takes a single operation.
 395          * If you are doing a batch of operations that should either
 396          * all succeed or all fail, then use that function instead.
 397          *
 398          * @see FileBackend::doOperations()
 399          *
 400          * @param array $op Operation
 401          * @param array $opts Operation options
 402          * @return Status
 403          */
 404         final public function doOperation( array $op, array $opts = array() ) {
 405                 return $this->doOperations( array( $op ), $opts );
 406         }
 407
 408         /**
 409          * Performs a single create operation.
 410          * This sets $params['op'] to 'create' and passes it to doOperation().
 411          *
 412          * @see FileBackend::doOperation()
 413          *
 414          * @param array $params Operation parameters
 415          * @param array $opts Operation options
 416          * @return Status
 417          */
 418         final public function create( array $params, array $opts = array() ) {
 419                 return $this->doOperation( array( 'op' => 'create' ) + $params, $opts );
 420         }
 421
 422         /**
 423          * Performs a single store operation.
 424          * This sets $params['op'] to 'store' and passes it to doOperation().
 425          *
 426          * @see FileBackend::doOperation()
 427          *
 428          * @param array $params Operation parameters
 429          * @param array $opts Operation options
 430          * @return Status
 431          */
 432         final public function store( array $params, array $opts = array() ) {
 433                 return $this->doOperation( array( 'op' => 'store' ) + $params, $opts );
 434         }
 435
 436         /**
 437          * Performs a single copy operation.
 438          * This sets $params['op'] to 'copy' and passes it to doOperation().
 439          *
 440          * @see FileBackend::doOperation()
 441          *
 442          * @param array $params Operation parameters
 443          * @param array $opts Operation options
 444          * @return Status
 445          */
 446         final public function copy( array $params, array $opts = array() ) {
 447                 return $this->doOperation( array( 'op' => 'copy' ) + $params, $opts );
 448         }
 449
 450         /**
 451          * Performs a single move operation.
 452          * This sets $params['op'] to 'move' and passes it to doOperation().
 453          *
 454          * @see FileBackend::doOperation()
 455          *
 456          * @param array $params Operation parameters
 457          * @param array $opts Operation options
 458          * @return Status
 459          */
 460         final public function move( array $params, array $opts = array() ) {
 461                 return $this->doOperation( array( 'op' => 'move' ) + $params, $opts );
 462         }
 463
 464         /**
 465          * Performs a single delete operation.
 466          * This sets $params['op'] to 'delete' and passes it to doOperation().
 467          *
 468          * @see FileBackend::doOperation()
 469          *
 470          * @param array $params Operation parameters
 471          * @param array $opts Operation options
 472          * @return Status
 473          */
 474         final public function delete( array $params, array $opts = array() ) {
 475                 return $this->doOperation( array( 'op' => 'delete' ) + $params, $opts );
 476         }
 477
 478         /**
 479          * Performs a single describe operation.
 480          * This sets $params['op'] to 'describe' and passes it to doOperation().
 481          *
 482          * @see FileBackend::doOperation()
 483          *
 484          * @param array $params Operation parameters
 485          * @param array $opts Operation options
 486          * @return Status
 487          * @since 1.21
 488          */
 489         final public function describe( array $params, array $opts = array() ) {
 490                 return $this->doOperation( array( 'op' => 'describe' ) + $params, $opts );
 491         }
 492
 493         /**
 494          * Perform a set of independent file operations on some files.
 495          *
 496          * This does no locking, nor journaling, and possibly no stat calls.
 497          * Any destination files that already exist will be overwritten.
 498          * This should *only* be used on non-original files, like cache files.
 499          *
 500          * Supported operations and their parameters:
 501          *  - create
 502          *  - store
 503          *  - copy
 504          *  - move
 505          *  - delete
 506          *  - describe (since 1.21)
 507          *  - null
 508          *
 509          * a) Create a new file in storage with the contents of a string
 510          * @code
 511          *     array(
 512          *         'op'                  => 'create',
 513          *         'dst'                 => <storage path>,
 514          *         'content'             => <string of new file contents>,
 515          *         'headers'             => <HTTP header name/value map> # since 1.21
 516          *     )
 517          * @endcode
 518          *
 519          * b) Copy a file system file into storage
 520          * @code
 521          *     array(
 522          *         'op'                  => 'store',
 523          *         'src'                 => <file system path>,
 524          *         'dst'                 => <storage path>,
 525          *         'headers'             => <HTTP header name/value map> # since 1.21
 526          *     )
 527          * @endcode
 528          *
 529          * c) Copy a file within storage
 530          * @code
 531          *     array(
 532          *         'op'                  => 'copy',
 533          *         'src'                 => <storage path>,
 534          *         'dst'                 => <storage path>,
 535          *         'ignoreMissingSource' => <boolean>, # since 1.21
 536          *         'headers'             => <HTTP header name/value map> # since 1.21
 537          *     )
 538          * @endcode
 539          *
 540          * d) Move a file within storage
 541          * @code
 542          *     array(
 543          *         'op'                  => 'move',
 544          *         'src'                 => <storage path>,
 545          *         'dst'                 => <storage path>,
 546          *         'ignoreMissingSource' => <boolean>, # since 1.21
 547          *         'headers'             => <HTTP header name/value map> # since 1.21
 548          *     )
 549          * @endcode
 550          *
 551          * e) Delete a file within storage
 552          * @code
 553          *     array(
 554          *         'op'                  => 'delete',
 555          *         'src'                 => <storage path>,
 556          *         'ignoreMissingSource' => <boolean>
 557          *     )
 558          * @endcode
 559          *
 560          * f) Update metadata for a file within storage
 561          * @code
 562          *     array(
 563          *         'op'                  => 'describe',
 564          *         'src'                 => <storage path>,
 565          *         'headers'             => <HTTP header name/value map>
 566          *     )
 567          * @endcode
 568          *
 569          * g) Do nothing (no-op)
 570          * @code
 571          *     array(
 572          *         'op'                  => 'null',
 573          *     )
 574          * @endcode
 575          *
 576          * @par Boolean flags for operations (operation-specific):
 577          *   - ignoreMissingSource : The operation will simply succeed and do
 578          *                           nothing if the source file does not exist.
 579          *   - headers             : If supplied with a header name/value map, the backend will
 580          *                           reply with these headers when GETs/HEADs of the destination
 581          *                           file are made. Header values should be smaller than 256 bytes.
 582          *                           Content-Disposition headers can be longer, though the system
 583          *                           might ignore or truncate ones that are too long to store.
 584          *                           Existing headers will remain, but these will replace any
 585          *                           conflicting previous headers, and headers will be removed
 586          *                           if they are set to an empty string.
 587          *                           Backends that don't support metadata ignore this. (since 1.21)
 588          *
 589          * $opts is an associative of boolean flags, including:
 590          *   - bypassReadOnly      : Allow writes in read-only mode (since 1.20)
 591          *
 592          * @par Return value:
 593          * This returns a Status, which contains all warnings and fatals that occurred
 594          * during the operation. The 'failCount', 'successCount', and 'success' members
 595          * will reflect each operation attempted for the given files. The status will be
 596          * considered "OK" as long as no fatal errors occurred.
 597          *
 598          * @param array $ops Set of operations to execute
 599          * @param array $opts Batch operation options
 600          * @return Status
 601          * @since 1.20
 602          */
 603         final public function doQuickOperations( array $ops, array $opts = array() ) {
 604                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 605                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 606                 }
 607                 if ( !count( $ops ) ) {
 608                         return Status::newGood(); // nothing to do
 609                 }
 610                 foreach ( $ops as &$op ) {
 611                         $op['overwrite'] = true; // avoids RTTs in key/value stores
 612                         if ( isset( $op['disposition'] ) ) { // b/c (MW 1.20)
 613                                 $op['headers']['Content-Disposition'] = $op['disposition'];
 614                         }
 615                 }
 616                 /** @noinspection PhpUnusedLocalVariableInspection */
 617                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 618                 return $this->doQuickOperationsInternal( $ops );
 619         }
 620
 621         /**
 622          * @see FileBackend::doQuickOperations()
 623          * @since 1.20
 624          */
 625         abstract protected function doQuickOperationsInternal( array $ops );
 626
 627         /**
 628          * Same as doQuickOperations() except it takes a single operation.
 629          * If you are doing a batch of operations, then use that function instead.
 630          *
 631          * @see FileBackend::doQuickOperations()
 632          *
 633          * @param array $op Operation
 634          * @return Status
 635          * @since 1.20
 636          */
 637         final public function doQuickOperation( array $op ) {
 638                 return $this->doQuickOperations( array( $op ) );
 639         }
 640
 641         /**
 642          * Performs a single quick create operation.
 643          * This sets $params['op'] to 'create' and passes it to doQuickOperation().
 644          *
 645          * @see FileBackend::doQuickOperation()
 646          *
 647          * @param array $params Operation parameters
 648          * @return Status
 649          * @since 1.20
 650          */
 651         final public function quickCreate( array $params ) {
 652                 return $this->doQuickOperation( array( 'op' => 'create' ) + $params );
 653         }
 654
 655         /**
 656          * Performs a single quick store operation.
 657          * This sets $params['op'] to 'store' and passes it to doQuickOperation().
 658          *
 659          * @see FileBackend::doQuickOperation()
 660          *
 661          * @param array $params Operation parameters
 662          * @return Status
 663          * @since 1.20
 664          */
 665         final public function quickStore( array $params ) {
 666                 return $this->doQuickOperation( array( 'op' => 'store' ) + $params );
 667         }
 668
 669         /**
 670          * Performs a single quick copy operation.
 671          * This sets $params['op'] to 'copy' and passes it to doQuickOperation().
 672          *
 673          * @see FileBackend::doQuickOperation()
 674          *
 675          * @param array $params Operation parameters
 676          * @return Status
 677          * @since 1.20
 678          */
 679         final public function quickCopy( array $params ) {
 680                 return $this->doQuickOperation( array( 'op' => 'copy' ) + $params );
 681         }
 682
 683         /**
 684          * Performs a single quick move operation.
 685          * This sets $params['op'] to 'move' and passes it to doQuickOperation().
 686          *
 687          * @see FileBackend::doQuickOperation()
 688          *
 689          * @param array $params Operation parameters
 690          * @return Status
 691          * @since 1.20
 692          */
 693         final public function quickMove( array $params ) {
 694                 return $this->doQuickOperation( array( 'op' => 'move' ) + $params );
 695         }
 696
 697         /**
 698          * Performs a single quick delete operation.
 699          * This sets $params['op'] to 'delete' and passes it to doQuickOperation().
 700          *
 701          * @see FileBackend::doQuickOperation()
 702          *
 703          * @param array $params Operation parameters
 704          * @return Status
 705          * @since 1.20
 706          */
 707         final public function quickDelete( array $params ) {
 708                 return $this->doQuickOperation( array( 'op' => 'delete' ) + $params );
 709         }
 710
 711         /**
 712          * Performs a single quick describe operation.
 713          * This sets $params['op'] to 'describe' and passes it to doQuickOperation().
 714          *
 715          * @see FileBackend::doQuickOperation()
 716          *
 717          * @param array $params Operation parameters
 718          * @return Status
 719          * @since 1.21
 720          */
 721         final public function quickDescribe( array $params ) {
 722                 return $this->doQuickOperation( array( 'op' => 'describe' ) + $params );
 723         }
 724
 725         /**
 726          * Concatenate a list of storage files into a single file system file.
 727          * The target path should refer to a file that is already locked or
 728          * otherwise safe from modification from other processes. Normally,
 729          * the file will be a new temp file, which should be adequate.
 730          *
 731          * @param array $params Operation parameters, include:
 732          *   - srcs        : ordered source storage paths (e.g. chunk1, chunk2, ...)
 733          *   - dst         : file system path to 0-byte temp file
 734          *   - parallelize : try to do operations in parallel when possible
 735          * @return Status
 736          */
 737         abstract public function concatenate( array $params );
 738
 739         /**
 740          * Prepare a storage directory for usage.
 741          * This will create any required containers and parent directories.
 742          * Backends using key/value stores only need to create the container.
 743          *
 744          * The 'noAccess' and 'noListing' parameters works the same as in secure(),
 745          * except they are only applied *if* the directory/container had to be created.
 746          * These flags should always be set for directories that have private files.
 747          * However, setting them is not guaranteed to actually do anything.
 748          * Additional server configuration may be needed to achieve the desired effect.
 749          *
 750          * @param array $params Parameters include:
 751          *   - dir            : storage directory
 752          *   - noAccess       : try to deny file access (since 1.20)
 753          *   - noListing      : try to deny file listing (since 1.20)
 754          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 755          * @return Status
 756          */
 757         final public function prepare( array $params ) {
 758                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 759                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 760                 }
 761                 /** @noinspection PhpUnusedLocalVariableInspection */
 762                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 763                 return $this->doPrepare( $params );
 764         }
 765
 766         /**
 767          * @see FileBackend::prepare()
 768          */
 769         abstract protected function doPrepare( array $params );
 770
 771         /**
 772          * Take measures to block web access to a storage directory and
 773          * the container it belongs to. FS backends might add .htaccess
 774          * files whereas key/value store backends might revoke container
 775          * access to the storage user representing end-users in web requests.
 776          *
 777          * This is not guaranteed to actually make files or listings publically hidden.
 778          * Additional server configuration may be needed to achieve the desired effect.
 779          *
 780          * @param array $params Parameters include:
 781          *   - dir            : storage directory
 782          *   - noAccess       : try to deny file access
 783          *   - noListing      : try to deny file listing
 784          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 785          * @return Status
 786          */
 787         final public function secure( array $params ) {
 788                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 789                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 790                 }
 791                 /** @noinspection PhpUnusedLocalVariableInspection */
 792                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 793                 return $this->doSecure( $params );
 794         }
 795
 796         /**
 797          * @see FileBackend::secure()
 798          */
 799         abstract protected function doSecure( array $params );
 800
 801         /**
 802          * Remove measures to block web access to a storage directory and
 803          * the container it belongs to. FS backends might remove .htaccess
 804          * files whereas key/value store backends might grant container
 805          * access to the storage user representing end-users in web requests.
 806          * This essentially can undo the result of secure() calls.
 807          *
 808          * This is not guaranteed to actually make files or listings publically viewable.
 809          * Additional server configuration may be needed to achieve the desired effect.
 810          *
 811          * @param array $params Parameters include:
 812          *   - dir            : storage directory
 813          *   - access         : try to allow file access
 814          *   - listing        : try to allow file listing
 815          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 816          * @return Status
 817          * @since 1.20
 818          */
 819         final public function publish( array $params ) {
 820                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 821                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 822                 }
 823                 /** @noinspection PhpUnusedLocalVariableInspection */
 824                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 825                 return $this->doPublish( $params );
 826         }
 827
 828         /**
 829          * @see FileBackend::publish()
 830          */
 831         abstract protected function doPublish( array $params );
 832
 833         /**
 834          * Delete a storage directory if it is empty.
 835          * Backends using key/value stores may do nothing unless the directory
 836          * is that of an empty container, in which case it will be deleted.
 837          *
 838          * @param array $params Parameters include:
 839          *   - dir            : storage directory
 840          *   - recursive      : recursively delete empty subdirectories first (since 1.20)
 841          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 842          * @return Status
 843          */
 844         final public function clean( array $params ) {
 845                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 846                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 847                 }
 848                 /** @noinspection PhpUnusedLocalVariableInspection */
 849                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 850                 return $this->doClean( $params );
 851         }
 852
 853         /**
 854          * @see FileBackend::clean()
 855          */
 856         abstract protected function doClean( array $params );
 857
 858         /**
 859          * Enter file operation scope.
 860          * This just makes PHP ignore user aborts/disconnects until the return
 861          * value leaves scope. This returns null and does nothing in CLI mode.
 862          *
 863          * @return ScopedCallback|null
 864          */
 865         final protected function getScopedPHPBehaviorForOps() {
 866                 if ( PHP_SAPI != 'cli' ) { // http://bugs.php.net/bug.php?id=47540
 867                         $old = ignore_user_abort( true ); // avoid half-finished operations
 868                         return new ScopedCallback( function () use ( $old ) {
 869                                 ignore_user_abort( $old );
 870                         } );
 871                 }
 872
 873                 return null;
 874         }
 875
 876         /**
 877          * Check if a file exists at a storage path in the backend.
 878          * This returns false if only a directory exists at the path.
 879          *
 880          * @param array $params Parameters include:
 881          *   - src    : source storage path
 882          *   - latest : use the latest available data
 883          * @return bool|null Returns null on failure
 884          */
 885         abstract public function fileExists( array $params );
 886
 887         /**
 888          * Get the last-modified timestamp of the file at a storage path.
 889          *
 890          * @param array $params Parameters include:
 891          *   - src    : source storage path
 892          *   - latest : use the latest available data
 893          * @return string|bool TS_MW timestamp or false on failure
 894          */
 895         abstract public function getFileTimestamp( array $params );
 896
 897         /**
 898          * Get the contents of a file at a storage path in the backend.
 899          * This should be avoided for potentially large files.
 900          *
 901          * @param array $params Parameters include:
 902          *   - src    : source storage path
 903          *   - latest : use the latest available data
 904          * @return string|bool Returns false on failure
 905          */
 906         final public function getFileContents( array $params ) {
 907                 $contents = $this->getFileContentsMulti(
 908                         array( 'srcs' => array( $params['src'] ) ) + $params );
 909
 910                 return $contents[$params['src']];
 911         }
 912
 913         /**
 914          * Like getFileContents() except it takes an array of storage paths
 915          * and returns a map of storage paths to strings (or null on failure).
 916          * The map keys (paths) are in the same order as the provided list of paths.
 917          *
 918          * @see FileBackend::getFileContents()
 919          *
 920          * @param array $params Parameters include:
 921          *   - srcs        : list of source storage paths
 922          *   - latest      : use the latest available data
 923          *   - parallelize : try to do operations in parallel when possible
 924          * @return array Map of (path name => string or false on failure)
 925          * @since 1.20
 926          */
 927         abstract public function getFileContentsMulti( array $params );
 928
 929         /**
 930          * Get metadata about a file at a storage path in the backend.
 931          * If the file does not exist, then this returns false.
 932          * Otherwise, the result is an associative array that includes:
 933          *   - headers  : map of HTTP headers used for GET/HEAD requests (name => value)
 934          *   - metadata : map of file metadata (name => value)
 935          * Metadata keys and headers names will be returned in all lower-case.
 936          * Additional values may be included for internal use only.
 937          *
 938          * Use FileBackend::hasFeatures() to check how well this is supported.
 939          *
 940          * @param array $params
 941          * $params include:
 942          *   - src    : source storage path
 943          *   - latest : use the latest available data
 944          * @return array|bool Returns false on failure
 945          * @since 1.23
 946          */
 947         abstract public function getFileXAttributes( array $params );
 948
 949         /**
 950          * Get the size (bytes) of a file at a storage path in the backend.
 951          *
 952          * @param array $params Parameters include:
 953          *   - src    : source storage path
 954          *   - latest : use the latest available data
 955          * @return int|bool Returns false on failure
 956          */
 957         abstract public function getFileSize( array $params );
 958
 959         /**
 960          * Get quick information about a file at a storage path in the backend.
 961          * If the file does not exist, then this returns false.
 962          * Otherwise, the result is an associative array that includes:
 963          *   - mtime  : the last-modified timestamp (TS_MW)
 964          *   - size   : the file size (bytes)
 965          * Additional values may be included for internal use only.
 966          *
 967          * @param array $params Parameters include:
 968          *   - src    : source storage path
 969          *   - latest : use the latest available data
 970          * @return array|bool|null Returns null on failure
 971          */
 972         abstract public function getFileStat( array $params );
 973
 974         /**
 975          * Get a SHA-1 hash of the file at a storage path in the backend.
 976          *
 977          * @param array $params Parameters include:
 978          *   - src    : source storage path
 979          *   - latest : use the latest available data
 980          * @return string|bool Hash string or false on failure
 981          */
 982         abstract public function getFileSha1Base36( array $params );
 983
 984         /**
 985          * Get the properties of the file at a storage path in the backend.
 986          * This gives the result of FSFile::getProps() on a local copy of the file.
 987          *
 988          * @param array $params Parameters include:
 989          *   - src    : source storage path
 990          *   - latest : use the latest available data
 991          * @return array Returns FSFile::placeholderProps() on failure
 992          */
 993         abstract public function getFileProps( array $params );
 994
 995         /**
 996          * Stream the file at a storage path in the backend.
 997          * If the file does not exists, an HTTP 404 error will be given.
 998          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
 999          * will be sent if streaming began, while none will be sent otherwise.
1000          * Implementations should flush the output buffer before sending data.
1001          *
1002          * @param array $params Parameters include:
1003          *   - src     : source storage path
1004          *   - headers : list of additional HTTP headers to send on success
1005          *   - latest  : use the latest available data
1006          * @return Status
1007          */
1008         abstract public function streamFile( array $params );
1009
1010         /**
1011          * Returns a file system file, identical to the file at a storage path.
1012          * The file returned is either:
1013          *   - a) A local copy of the file at a storage path in the backend.
1014          *        The temporary copy will have the same extension as the source.
1015          *   - b) An original of the file at a storage path in the backend.
1016          * Temporary files may be purged when the file object falls out of scope.
1017          *
1018          * Write operations should *never* be done on this file as some backends
1019          * may do internal tracking or may be instances of FileBackendMultiWrite.
1020          * In that later case, there are copies of the file that must stay in sync.
1021          * Additionally, further calls to this function may return the same file.
1022          *
1023          * @param array $params Parameters include:
1024          *   - src    : source storage path
1025          *   - latest : use the latest available data
1026          * @return FSFile|null Returns null on failure
1027          */
1028         final public function getLocalReference( array $params ) {
1029                 $fsFiles = $this->getLocalReferenceMulti(
1030                         array( 'srcs' => array( $params['src'] ) ) + $params );
1031
1032                 return $fsFiles[$params['src']];
1033         }
1034
1035         /**
1036          * Like getLocalReference() except it takes an array of storage paths
1037          * and returns a map of storage paths to FSFile objects (or null on failure).
1038          * The map keys (paths) are in the same order as the provided list of paths.
1039          *
1040          * @see FileBackend::getLocalReference()
1041          *
1042          * @param array $params Parameters include:
1043          *   - srcs        : list of source storage paths
1044          *   - latest      : use the latest available data
1045          *   - parallelize : try to do operations in parallel when possible
1046          * @return array Map of (path name => FSFile or null on failure)
1047          * @since 1.20
1048          */
1049         abstract public function getLocalReferenceMulti( array $params );
1050
1051         /**
1052          * Get a local copy on disk of the file at a storage path in the backend.
1053          * The temporary copy will have the same file extension as the source.
1054          * Temporary files may be purged when the file object falls out of scope.
1055          *
1056          * @param array $params Parameters include:
1057          *   - src    : source storage path
1058          *   - latest : use the latest available data
1059          * @return TempFSFile|null Returns null on failure
1060          */
1061         final public function getLocalCopy( array $params ) {
1062                 $tmpFiles = $this->getLocalCopyMulti(
1063                         array( 'srcs' => array( $params['src'] ) ) + $params );
1064
1065                 return $tmpFiles[$params['src']];
1066         }
1067
1068         /**
1069          * Like getLocalCopy() except it takes an array of storage paths and
1070          * returns a map of storage paths to TempFSFile objects (or null on failure).
1071          * The map keys (paths) are in the same order as the provided list of paths.
1072          *
1073          * @see FileBackend::getLocalCopy()
1074          *
1075          * @param array $params Parameters include:
1076          *   - srcs        : list of source storage paths
1077          *   - latest      : use the latest available data
1078          *   - parallelize : try to do operations in parallel when possible
1079          * @return array Map of (path name => TempFSFile or null on failure)
1080          * @since 1.20
1081          */
1082         abstract public function getLocalCopyMulti( array $params );
1083
1084         /**
1085          * Return an HTTP URL to a given file that requires no authentication to use.
1086          * The URL may be pre-authenticated (via some token in the URL) and temporary.
1087          * This will return null if the backend cannot make an HTTP URL for the file.
1088          *
1089          * This is useful for key/value stores when using scripts that seek around
1090          * large files and those scripts (and the backend) support HTTP Range headers.
1091          * Otherwise, one would need to use getLocalReference(), which involves loading
1092          * the entire file on to local disk.
1093          *
1094          * @param array $params Parameters include:
1095          *   - src : source storage path
1096          *   - ttl : lifetime (seconds) if pre-authenticated; default is 1 day
1097          * @return string|null
1098          * @since 1.21
1099          */
1100         abstract public function getFileHttpUrl( array $params );
1101
1102         /**
1103          * Check if a directory exists at a given storage path.
1104          * Backends using key/value stores will check if the path is a
1105          * virtual directory, meaning there are files under the given directory.
1106          *
1107          * Storage backends with eventual consistency might return stale data.
1108          *
1109          * @param array $params Parameters include:
1110          *   - dir : storage directory
1111          * @return bool|null Returns null on failure
1112          * @since 1.20
1113          */
1114         abstract public function directoryExists( array $params );
1115
1116         /**
1117          * Get an iterator to list *all* directories under a storage directory.
1118          * If the directory is of the form "mwstore://backend/container",
1119          * then all directories in the container will be listed.
1120          * If the directory is of form "mwstore://backend/container/dir",
1121          * then all directories directly under that directory will be listed.
1122          * Results will be storage directories relative to the given directory.
1123          *
1124          * Storage backends with eventual consistency might return stale data.
1125          *
1126          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1127          *
1128          * @param array $params Parameters include:
1129          *   - dir     : storage directory
1130          *   - topOnly : only return direct child dirs of the directory
1131          * @return Traversable|array|null Returns null on failure
1132          * @since 1.20
1133          */
1134         abstract public function getDirectoryList( array $params );
1135
1136         /**
1137          * Same as FileBackend::getDirectoryList() except only lists
1138          * directories that are immediately under the given directory.
1139          *
1140          * Storage backends with eventual consistency might return stale data.
1141          *
1142          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1143          *
1144          * @param array $params Parameters include:
1145          *   - dir : storage directory
1146          * @return Traversable|array|null Returns null on failure
1147          * @since 1.20
1148          */
1149         final public function getTopDirectoryList( array $params ) {
1150                 return $this->getDirectoryList( array( 'topOnly' => true ) + $params );
1151         }
1152
1153         /**
1154          * Get an iterator to list *all* stored files under a storage directory.
1155          * If the directory is of the form "mwstore://backend/container",
1156          * then all files in the container will be listed.
1157          * If the directory is of form "mwstore://backend/container/dir",
1158          * then all files under that directory will be listed.
1159          * Results will be storage paths relative to the given directory.
1160          *
1161          * Storage backends with eventual consistency might return stale data.
1162          *
1163          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1164          *
1165          * @param array $params Parameters include:
1166          *   - dir        : storage directory
1167          *   - topOnly    : only return direct child files of the directory (since 1.20)
1168          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1169          * @return Traversable|array|null Returns null on failure
1170          */
1171         abstract public function getFileList( array $params );
1172
1173         /**
1174          * Same as FileBackend::getFileList() except only lists
1175          * files that are immediately under the given directory.
1176          *
1177          * Storage backends with eventual consistency might return stale data.
1178          *
1179          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1180          *
1181          * @param array $params Parameters include:
1182          *   - dir        : storage directory
1183          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1184          * @return Traversable|array|null Returns null on failure
1185          * @since 1.20
1186          */
1187         final public function getTopFileList( array $params ) {
1188                 return $this->getFileList( array( 'topOnly' => true ) + $params );
1189         }
1190
1191         /**
1192          * Preload persistent file stat cache and property cache into in-process cache.
1193          * This should be used when stat calls will be made on a known list of a many files.
1194          *
1195          * @see FileBackend::getFileStat()
1196          *
1197          * @param array $paths Storage paths
1198          */
1199         abstract public function preloadCache( array $paths );
1200
1201         /**
1202          * Invalidate any in-process file stat and property cache.
1203          * If $paths is given, then only the cache for those files will be cleared.
1204          *
1205          * @see FileBackend::getFileStat()
1206          *
1207          * @param array $paths Storage paths (optional)
1208          */
1209         abstract public function clearCache( array $paths = null );
1210
1211         /**
1212          * Preload file stat information (concurrently if possible) into in-process cache.
1213          *
1214          * This should be used when stat calls will be made on a known list of a many files.
1215          * This does not make use of the persistent file stat cache.
1216          *
1217          * @see FileBackend::getFileStat()
1218          *
1219          * @param array $params Parameters include:
1220          *   - srcs        : list of source storage paths
1221          *   - latest      : use the latest available data
1222          * @return bool All requests proceeded without I/O errors (since 1.24)
1223          * @since 1.23
1224          */
1225         abstract public function preloadFileStat( array $params );
1226
1227         /**
1228          * Lock the files at the given storage paths in the backend.
1229          * This will either lock all the files or none (on failure).
1230          *
1231          * Callers should consider using getScopedFileLocks() instead.
1232          *
1233          * @param array $paths Storage paths
1234          * @param int $type LockManager::LOCK_* constant
1235          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.24)
1236          * @return Status
1237          */
1238         final public function lockFiles( array $paths, $type, $timeout = 0 ) {
1239                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1240
1241                 return $this->lockManager->lock( $paths, $type, $timeout );
1242         }
1243
1244         /**
1245          * Unlock the files at the given storage paths in the backend.
1246          *
1247          * @param array $paths Storage paths
1248          * @param int $type LockManager::LOCK_* constant
1249          * @return Status
1250          */
1251         final public function unlockFiles( array $paths, $type ) {
1252                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1253
1254                 return $this->lockManager->unlock( $paths, $type );
1255         }
1256
1257         /**
1258          * Lock the files at the given storage paths in the backend.
1259          * This will either lock all the files or none (on failure).
1260          * On failure, the status object will be updated with errors.
1261          *
1262          * Once the return value goes out scope, the locks will be released and
1263          * the status updated. Unlock fatals will not change the status "OK" value.
1264          *
1265          * @see ScopedLock::factory()
1266          *
1267          * @param array $paths List of storage paths or map of lock types to path lists
1268          * @param int|string $type LockManager::LOCK_* constant or "mixed"
1269          * @param Status $status Status to update on lock/unlock
1270          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.24)
1271          * @return ScopedLock|null Returns null on failure
1272          */
1273         final public function getScopedFileLocks( array $paths, $type, Status $status, $timeout = 0 ) {
1274                 if ( $type === 'mixed' ) {
1275                         foreach ( $paths as &$typePaths ) {
1276                                 $typePaths = array_map( 'FileBackend::normalizeStoragePath', $typePaths );
1277                         }
1278                 } else {
1279                         $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1280                 }
1281
1282                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status, $timeout );
1283         }
1284
1285         /**
1286          * Get an array of scoped locks needed for a batch of file operations.
1287          *
1288          * Normally, FileBackend::doOperations() handles locking, unless
1289          * the 'nonLocking' param is passed in. This function is useful if you
1290          * want the files to be locked for a broader scope than just when the
1291          * files are changing. For example, if you need to update DB metadata,
1292          * you may want to keep the files locked until finished.
1293          *
1294          * @see FileBackend::doOperations()
1295          *
1296          * @param array $ops List of file operations to FileBackend::doOperations()
1297          * @param Status $status Status to update on lock/unlock
1298          * @return array List of ScopedFileLocks or null values
1299          * @since 1.20
1300          */
1301         abstract public function getScopedLocksForOps( array $ops, Status $status );
1302
1303         /**
1304          * Get the root storage path of this backend.
1305          * All container paths are "subdirectories" of this path.
1306          *
1307          * @return string Storage path
1308          * @since 1.20
1309          */
1310         final public function getRootStoragePath() {
1311                 return "mwstore://{$this->name}";
1312         }
1313
1314         /**
1315          * Get the storage path for the given container for this backend
1316          *
1317          * @param string $container Container name
1318          * @return string Storage path
1319          * @since 1.21
1320          */
1321         final public function getContainerStoragePath( $container ) {
1322                 return $this->getRootStoragePath() . "/{$container}";
1323         }
1324
1325         /**
1326          * Get the file journal object for this backend
1327          *
1328          * @return FileJournal
1329          */
1330         final public function getJournal() {
1331                 return $this->fileJournal;
1332         }
1333
1334         /**
1335          * Check if a given path is a "mwstore://" path.
1336          * This does not do any further validation or any existence checks.
1337          *
1338          * @param string $path
1339          * @return bool
1340          */
1341         final public static function isStoragePath( $path ) {
1342                 return ( strpos( $path, 'mwstore://' ) === 0 );
1343         }
1344
1345         /**
1346          * Split a storage path into a backend name, a container name,
1347          * and a relative file path. The relative path may be the empty string.
1348          * This does not do any path normalization or traversal checks.
1349          *
1350          * @param string $storagePath
1351          * @return array (backend, container, rel object) or (null, null, null)
1352          */
1353         final public static function splitStoragePath( $storagePath ) {
1354                 if ( self::isStoragePath( $storagePath ) ) {
1355                         // Remove the "mwstore://" prefix and split the path
1356                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
1357                         if ( count( $parts ) >= 2 && $parts[0] != '' && $parts[1] != '' ) {
1358                                 if ( count( $parts ) == 3 ) {
1359                                         return $parts; // e.g. "backend/container/path"
1360                                 } else {
1361                                         return array( $parts[0], $parts[1], '' ); // e.g. "backend/container"
1362                                 }
1363                         }
1364                 }
1365
1366                 return array( null, null, null );
1367         }
1368
1369         /**
1370          * Normalize a storage path by cleaning up directory separators.
1371          * Returns null if the path is not of the format of a valid storage path.
1372          *
1373          * @param string $storagePath
1374          * @return string|null
1375          */
1376         final public static function normalizeStoragePath( $storagePath ) {
1377                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
1378                 if ( $relPath !== null ) { // must be for this backend
1379                         $relPath = self::normalizeContainerPath( $relPath );
1380                         if ( $relPath !== null ) {
1381                                 return ( $relPath != '' )
1382                                         ? "mwstore://{$backend}/{$container}/{$relPath}"
1383                                         : "mwstore://{$backend}/{$container}";
1384                         }
1385                 }
1386
1387                 return null;
1388         }
1389
1390         /**
1391          * Get the parent storage directory of a storage path.
1392          * This returns a path like "mwstore://backend/container",
1393          * "mwstore://backend/container/...", or null if there is no parent.
1394          *
1395          * @param string $storagePath
1396          * @return string|null
1397          */
1398         final public static function parentStoragePath( $storagePath ) {
1399                 $storagePath = dirname( $storagePath );
1400                 list( , , $rel ) = self::splitStoragePath( $storagePath );
1401
1402                 return ( $rel === null ) ? null : $storagePath;
1403         }
1404
1405         /**
1406          * Get the final extension from a storage or FS path
1407          *
1408          * @param string $path
1409          * @param string $case One of (rawcase, uppercase, lowercase) (since 1.24)
1410          * @return string
1411          */
1412         final public static function extensionFromPath( $path, $case = 'lowercase' ) {
1413                 $i = strrpos( $path, '.' );
1414                 $ext = $i ? substr( $path, $i + 1 ) : '';
1415
1416                 if ( $case === 'lowercase' ) {
1417                         $ext = strtolower( $ext );
1418                 } elseif ( $case === 'uppercase' ) {
1419                         $ext = strtoupper( $ext );
1420                 }
1421
1422                 return $ext;
1423         }
1424
1425         /**
1426          * Check if a relative path has no directory traversals
1427          *
1428          * @param string $path
1429          * @return bool
1430          * @since 1.20
1431          */
1432         final public static function isPathTraversalFree( $path ) {
1433                 return ( self::normalizeContainerPath( $path ) !== null );
1434         }
1435
1436         /**
1437          * Build a Content-Disposition header value per RFC 6266.
1438          *
1439          * @param string $type One of (attachment, inline)
1440          * @param string $filename Suggested file name (should not contain slashes)
1441          * @throws FileBackendError
1442          * @return string
1443          * @since 1.20
1444          */
1445         final public static function makeContentDisposition( $type, $filename = '' ) {
1446                 $parts = array();
1447
1448                 $type = strtolower( $type );
1449                 if ( !in_array( $type, array( 'inline', 'attachment' ) ) ) {
1450                         throw new FileBackendError( "Invalid Content-Disposition type '$type'." );
1451                 }
1452                 $parts[] = $type;
1453
1454                 if ( strlen( $filename ) ) {
1455                         $parts[] = "filename*=UTF-8''" . rawurlencode( basename( $filename ) );
1456                 }
1457
1458                 return implode( ';', $parts );
1459         }
1460
1461         /**
1462          * Validate and normalize a relative storage path.
1463          * Null is returned if the path involves directory traversal.
1464          * Traversal is insecure for FS backends and broken for others.
1465          *
1466          * This uses the same traversal protection as Title::secureAndSplit().
1467          *
1468          * @param string $path Storage path relative to a container
1469          * @return string|null
1470          */
1471         final protected static function normalizeContainerPath( $path ) {
1472                 // Normalize directory separators
1473                 $path = strtr( $path, '\\', '/' );
1474                 // Collapse any consecutive directory separators
1475                 $path = preg_replace( '![/]{2,}!', '/', $path );
1476                 // Remove any leading directory separator
1477                 $path = ltrim( $path, '/' );
1478                 // Use the same traversal protection as Title::secureAndSplit()
1479                 if ( strpos( $path, '.' ) !== false ) {
1480                         if (
1481                                 $path === '.' ||
1482                                 $path === '..' ||
1483                                 strpos( $path, './' ) === 0 ||
1484                                 strpos( $path, '../' ) === 0 ||
1485                                 strpos( $path, '/./' ) !== false ||
1486                                 strpos( $path, '/../' ) !== false
1487                         ) {
1488                                 return null;
1489                         }
1490                 }
1491
1492                 return $path;
1493         }
1494 }
1495
1496 /**
1497  * Generic file backend exception for checked and unexpected (e.g. config) exceptions
1498  *
1499  * @ingroup FileBackend
1500  * @since 1.23
1501  */
1502 class FileBackendException extends Exception {
1503 }
1504
1505 /**
1506  * File backend exception for checked exceptions (e.g. I/O errors)
1507  *
1508  * @ingroup FileBackend
1509  * @since 1.22
1510  */
1511 class FileBackendError extends FileBackendException {
1512 }