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