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                 /** @noinspection PhpUnusedLocalVariableInspection */
 379                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 380                 return $this->doOperationsInternal( $ops, $opts );
 381         }
 382
 383         /**
 384          * @see FileBackend::doOperations()
 385          * @param array $ops
 386          * @param array $opts
 387          */
 388         abstract protected function doOperationsInternal( array $ops, array $opts );
 389
 390         /**
 391          * Same as doOperations() except it takes a single operation.
 392          * If you are doing a batch of operations that should either
 393          * all succeed or all fail, then use that function instead.
 394          *
 395          * @see FileBackend::doOperations()
 396          *
 397          * @param array $op Operation
 398          * @param array $opts Operation options
 399          * @return Status
 400          */
 401         final public function doOperation( array $op, array $opts = array() ) {
 402                 return $this->doOperations( array( $op ), $opts );
 403         }
 404
 405         /**
 406          * Performs a single create operation.
 407          * This sets $params['op'] to 'create' and passes it to doOperation().
 408          *
 409          * @see FileBackend::doOperation()
 410          *
 411          * @param array $params Operation parameters
 412          * @param array $opts Operation options
 413          * @return Status
 414          */
 415         final public function create( array $params, array $opts = array() ) {
 416                 return $this->doOperation( array( 'op' => 'create' ) + $params, $opts );
 417         }
 418
 419         /**
 420          * Performs a single store operation.
 421          * This sets $params['op'] to 'store' and passes it to doOperation().
 422          *
 423          * @see FileBackend::doOperation()
 424          *
 425          * @param array $params Operation parameters
 426          * @param array $opts Operation options
 427          * @return Status
 428          */
 429         final public function store( array $params, array $opts = array() ) {
 430                 return $this->doOperation( array( 'op' => 'store' ) + $params, $opts );
 431         }
 432
 433         /**
 434          * Performs a single copy operation.
 435          * This sets $params['op'] to 'copy' and passes it to doOperation().
 436          *
 437          * @see FileBackend::doOperation()
 438          *
 439          * @param array $params Operation parameters
 440          * @param array $opts Operation options
 441          * @return Status
 442          */
 443         final public function copy( array $params, array $opts = array() ) {
 444                 return $this->doOperation( array( 'op' => 'copy' ) + $params, $opts );
 445         }
 446
 447         /**
 448          * Performs a single move operation.
 449          * This sets $params['op'] to 'move' and passes it to doOperation().
 450          *
 451          * @see FileBackend::doOperation()
 452          *
 453          * @param array $params Operation parameters
 454          * @param array $opts Operation options
 455          * @return Status
 456          */
 457         final public function move( array $params, array $opts = array() ) {
 458                 return $this->doOperation( array( 'op' => 'move' ) + $params, $opts );
 459         }
 460
 461         /**
 462          * Performs a single delete operation.
 463          * This sets $params['op'] to 'delete' and passes it to doOperation().
 464          *
 465          * @see FileBackend::doOperation()
 466          *
 467          * @param array $params Operation parameters
 468          * @param array $opts Operation options
 469          * @return Status
 470          */
 471         final public function delete( array $params, array $opts = array() ) {
 472                 return $this->doOperation( array( 'op' => 'delete' ) + $params, $opts );
 473         }
 474
 475         /**
 476          * Performs a single describe operation.
 477          * This sets $params['op'] to 'describe' and passes it to doOperation().
 478          *
 479          * @see FileBackend::doOperation()
 480          *
 481          * @param array $params Operation parameters
 482          * @param array $opts Operation options
 483          * @return Status
 484          * @since 1.21
 485          */
 486         final public function describe( array $params, array $opts = array() ) {
 487                 return $this->doOperation( array( 'op' => 'describe' ) + $params, $opts );
 488         }
 489
 490         /**
 491          * Perform a set of independent file operations on some files.
 492          *
 493          * This does no locking, nor journaling, and possibly no stat calls.
 494          * Any destination files that already exist will be overwritten.
 495          * This should *only* be used on non-original files, like cache files.
 496          *
 497          * Supported operations and their parameters:
 498          *  - create
 499          *  - store
 500          *  - copy
 501          *  - move
 502          *  - delete
 503          *  - describe (since 1.21)
 504          *  - null
 505          *
 506          * a) Create a new file in storage with the contents of a string
 507          * @code
 508          *     array(
 509          *         'op'                  => 'create',
 510          *         'dst'                 => <storage path>,
 511          *         'content'             => <string of new file contents>,
 512          *         'headers'             => <HTTP header name/value map> # since 1.21
 513          *     )
 514          * @endcode
 515          *
 516          * b) Copy a file system file into storage
 517          * @code
 518          *     array(
 519          *         'op'                  => 'store',
 520          *         'src'                 => <file system path>,
 521          *         'dst'                 => <storage path>,
 522          *         'headers'             => <HTTP header name/value map> # since 1.21
 523          *     )
 524          * @endcode
 525          *
 526          * c) Copy a file within storage
 527          * @code
 528          *     array(
 529          *         'op'                  => 'copy',
 530          *         'src'                 => <storage path>,
 531          *         'dst'                 => <storage path>,
 532          *         'ignoreMissingSource' => <boolean>, # since 1.21
 533          *         'headers'             => <HTTP header name/value map> # since 1.21
 534          *     )
 535          * @endcode
 536          *
 537          * d) Move a file within storage
 538          * @code
 539          *     array(
 540          *         'op'                  => 'move',
 541          *         'src'                 => <storage path>,
 542          *         'dst'                 => <storage path>,
 543          *         'ignoreMissingSource' => <boolean>, # since 1.21
 544          *         'headers'             => <HTTP header name/value map> # since 1.21
 545          *     )
 546          * @endcode
 547          *
 548          * e) Delete a file within storage
 549          * @code
 550          *     array(
 551          *         'op'                  => 'delete',
 552          *         'src'                 => <storage path>,
 553          *         'ignoreMissingSource' => <boolean>
 554          *     )
 555          * @endcode
 556          *
 557          * f) Update metadata for a file within storage
 558          * @code
 559          *     array(
 560          *         'op'                  => 'describe',
 561          *         'src'                 => <storage path>,
 562          *         'headers'             => <HTTP header name/value map>
 563          *     )
 564          * @endcode
 565          *
 566          * g) Do nothing (no-op)
 567          * @code
 568          *     array(
 569          *         'op'                  => 'null',
 570          *     )
 571          * @endcode
 572          *
 573          * @par Boolean flags for operations (operation-specific):
 574          *   - ignoreMissingSource : The operation will simply succeed and do
 575          *                           nothing if the source file does not exist.
 576          *   - headers             : If supplied with a header name/value map, the backend will
 577          *                           reply with these headers when GETs/HEADs of the destination
 578          *                           file are made. Header values should be smaller than 256 bytes.
 579          *                           Content-Disposition headers can be longer, though the system
 580          *                           might ignore or truncate ones that are too long to store.
 581          *                           Existing headers will remain, but these will replace any
 582          *                           conflicting previous headers, and headers will be removed
 583          *                           if they are set to an empty string.
 584          *                           Backends that don't support metadata ignore this. (since 1.21)
 585          *
 586          * $opts is an associative of boolean flags, including:
 587          *   - bypassReadOnly      : Allow writes in read-only mode (since 1.20)
 588          *
 589          * @par Return value:
 590          * This returns a Status, which contains all warnings and fatals that occurred
 591          * during the operation. The 'failCount', 'successCount', and 'success' members
 592          * will reflect each operation attempted for the given files. The status will be
 593          * considered "OK" as long as no fatal errors occurred.
 594          *
 595          * @param array $ops Set of operations to execute
 596          * @param array $opts Batch operation options
 597          * @return Status
 598          * @since 1.20
 599          */
 600         final public function doQuickOperations( array $ops, array $opts = array() ) {
 601                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 602                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 603                 }
 604                 if ( !count( $ops ) ) {
 605                         return Status::newGood(); // nothing to do
 606                 }
 607                 foreach ( $ops as &$op ) {
 608                         $op['overwrite'] = true; // avoids RTTs in key/value stores
 609                 }
 610                 /** @noinspection PhpUnusedLocalVariableInspection */
 611                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 612                 return $this->doQuickOperationsInternal( $ops );
 613         }
 614
 615         /**
 616          * @see FileBackend::doQuickOperations()
 617          * @param array $ops
 618          * @since 1.20
 619          */
 620         abstract protected function doQuickOperationsInternal( array $ops );
 621
 622         /**
 623          * Same as doQuickOperations() except it takes a single operation.
 624          * If you are doing a batch of operations, then use that function instead.
 625          *
 626          * @see FileBackend::doQuickOperations()
 627          *
 628          * @param array $op Operation
 629          * @return Status
 630          * @since 1.20
 631          */
 632         final public function doQuickOperation( array $op ) {
 633                 return $this->doQuickOperations( array( $op ) );
 634         }
 635
 636         /**
 637          * Performs a single quick create operation.
 638          * This sets $params['op'] to 'create' and passes it to doQuickOperation().
 639          *
 640          * @see FileBackend::doQuickOperation()
 641          *
 642          * @param array $params Operation parameters
 643          * @return Status
 644          * @since 1.20
 645          */
 646         final public function quickCreate( array $params ) {
 647                 return $this->doQuickOperation( array( 'op' => 'create' ) + $params );
 648         }
 649
 650         /**
 651          * Performs a single quick store operation.
 652          * This sets $params['op'] to 'store' and passes it to doQuickOperation().
 653          *
 654          * @see FileBackend::doQuickOperation()
 655          *
 656          * @param array $params Operation parameters
 657          * @return Status
 658          * @since 1.20
 659          */
 660         final public function quickStore( array $params ) {
 661                 return $this->doQuickOperation( array( 'op' => 'store' ) + $params );
 662         }
 663
 664         /**
 665          * Performs a single quick copy operation.
 666          * This sets $params['op'] to 'copy' and passes it to doQuickOperation().
 667          *
 668          * @see FileBackend::doQuickOperation()
 669          *
 670          * @param array $params Operation parameters
 671          * @return Status
 672          * @since 1.20
 673          */
 674         final public function quickCopy( array $params ) {
 675                 return $this->doQuickOperation( array( 'op' => 'copy' ) + $params );
 676         }
 677
 678         /**
 679          * Performs a single quick move operation.
 680          * This sets $params['op'] to 'move' and passes it to doQuickOperation().
 681          *
 682          * @see FileBackend::doQuickOperation()
 683          *
 684          * @param array $params Operation parameters
 685          * @return Status
 686          * @since 1.20
 687          */
 688         final public function quickMove( array $params ) {
 689                 return $this->doQuickOperation( array( 'op' => 'move' ) + $params );
 690         }
 691
 692         /**
 693          * Performs a single quick delete operation.
 694          * This sets $params['op'] to 'delete' and passes it to doQuickOperation().
 695          *
 696          * @see FileBackend::doQuickOperation()
 697          *
 698          * @param array $params Operation parameters
 699          * @return Status
 700          * @since 1.20
 701          */
 702         final public function quickDelete( array $params ) {
 703                 return $this->doQuickOperation( array( 'op' => 'delete' ) + $params );
 704         }
 705
 706         /**
 707          * Performs a single quick describe operation.
 708          * This sets $params['op'] to 'describe' and passes it to doQuickOperation().
 709          *
 710          * @see FileBackend::doQuickOperation()
 711          *
 712          * @param array $params Operation parameters
 713          * @return Status
 714          * @since 1.21
 715          */
 716         final public function quickDescribe( array $params ) {
 717                 return $this->doQuickOperation( array( 'op' => 'describe' ) + $params );
 718         }
 719
 720         /**
 721          * Concatenate a list of storage files into a single file system file.
 722          * The target path should refer to a file that is already locked or
 723          * otherwise safe from modification from other processes. Normally,
 724          * the file will be a new temp file, which should be adequate.
 725          *
 726          * @param array $params Operation parameters, include:
 727          *   - srcs        : ordered source storage paths (e.g. chunk1, chunk2, ...)
 728          *   - dst         : file system path to 0-byte temp file
 729          *   - parallelize : try to do operations in parallel when possible
 730          * @return Status
 731          */
 732         abstract public function concatenate( array $params );
 733
 734         /**
 735          * Prepare a storage directory for usage.
 736          * This will create any required containers and parent directories.
 737          * Backends using key/value stores only need to create the container.
 738          *
 739          * The 'noAccess' and 'noListing' parameters works the same as in secure(),
 740          * except they are only applied *if* the directory/container had to be created.
 741          * These flags should always be set for directories that have private files.
 742          * However, setting them is not guaranteed to actually do anything.
 743          * Additional server configuration may be needed to achieve the desired effect.
 744          *
 745          * @param array $params Parameters include:
 746          *   - dir            : storage directory
 747          *   - noAccess       : try to deny file access (since 1.20)
 748          *   - noListing      : try to deny file listing (since 1.20)
 749          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 750          * @return Status
 751          */
 752         final public function prepare( array $params ) {
 753                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 754                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 755                 }
 756                 /** @noinspection PhpUnusedLocalVariableInspection */
 757                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 758                 return $this->doPrepare( $params );
 759         }
 760
 761         /**
 762          * @see FileBackend::prepare()
 763          * @param array $params
 764          */
 765         abstract protected function doPrepare( array $params );
 766
 767         /**
 768          * Take measures to block web access to a storage directory and
 769          * the container it belongs to. FS backends might add .htaccess
 770          * files whereas key/value store backends might revoke container
 771          * access to the storage user representing end-users in web requests.
 772          *
 773          * This is not guaranteed to actually make files or listings publically hidden.
 774          * Additional server configuration may be needed to achieve the desired effect.
 775          *
 776          * @param array $params Parameters include:
 777          *   - dir            : storage directory
 778          *   - noAccess       : try to deny file access
 779          *   - noListing      : try to deny file listing
 780          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 781          * @return Status
 782          */
 783         final public function secure( array $params ) {
 784                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 785                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 786                 }
 787                 /** @noinspection PhpUnusedLocalVariableInspection */
 788                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 789                 return $this->doSecure( $params );
 790         }
 791
 792         /**
 793          * @see FileBackend::secure()
 794          * @param array $params
 795          */
 796         abstract protected function doSecure( array $params );
 797
 798         /**
 799          * Remove measures to block web access to a storage directory and
 800          * the container it belongs to. FS backends might remove .htaccess
 801          * files whereas key/value store backends might grant container
 802          * access to the storage user representing end-users in web requests.
 803          * This essentially can undo the result of secure() calls.
 804          *
 805          * This is not guaranteed to actually make files or listings publically viewable.
 806          * Additional server configuration may be needed to achieve the desired effect.
 807          *
 808          * @param array $params Parameters include:
 809          *   - dir            : storage directory
 810          *   - access         : try to allow file access
 811          *   - listing        : try to allow file listing
 812          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 813          * @return Status
 814          * @since 1.20
 815          */
 816         final public function publish( array $params ) {
 817                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 818                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 819                 }
 820                 /** @noinspection PhpUnusedLocalVariableInspection */
 821                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 822                 return $this->doPublish( $params );
 823         }
 824
 825         /**
 826          * @see FileBackend::publish()
 827          * @param array $params
 828          */
 829         abstract protected function doPublish( array $params );
 830
 831         /**
 832          * Delete a storage directory if it is empty.
 833          * Backends using key/value stores may do nothing unless the directory
 834          * is that of an empty container, in which case it will be deleted.
 835          *
 836          * @param array $params Parameters include:
 837          *   - dir            : storage directory
 838          *   - recursive      : recursively delete empty subdirectories first (since 1.20)
 839          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 840          * @return Status
 841          */
 842         final public function clean( array $params ) {
 843                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 844                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 845                 }
 846                 /** @noinspection PhpUnusedLocalVariableInspection */
 847                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 848                 return $this->doClean( $params );
 849         }
 850
 851         /**
 852          * @see FileBackend::clean()
 853          * @param array $params
 854          */
 855         abstract protected function doClean( array $params );
 856
 857         /**
 858          * Enter file operation scope.
 859          * This just makes PHP ignore user aborts/disconnects until the return
 860          * value leaves scope. This returns null and does nothing in CLI mode.
 861          *
 862          * @return ScopedCallback|null
 863          */
 864         final protected function getScopedPHPBehaviorForOps() {
 865                 if ( PHP_SAPI != 'cli' ) { // http://bugs.php.net/bug.php?id=47540
 866                         $old = ignore_user_abort( true ); // avoid half-finished operations
 867                         return new ScopedCallback( function () use ( $old ) {
 868                                 ignore_user_abort( $old );
 869                         } );
 870                 }
 871
 872                 return null;
 873         }
 874
 875         /**
 876          * Check if a file exists at a storage path in the backend.
 877          * This returns false if only a directory exists at the path.
 878          *
 879          * @param array $params Parameters include:
 880          *   - src    : source storage path
 881          *   - latest : use the latest available data
 882          * @return bool|null Returns null on failure
 883          */
 884         abstract public function fileExists( array $params );
 885
 886         /**
 887          * Get the last-modified timestamp of the file at a storage path.
 888          *
 889          * @param array $params Parameters include:
 890          *   - src    : source storage path
 891          *   - latest : use the latest available data
 892          * @return string|bool TS_MW timestamp or false on failure
 893          */
 894         abstract public function getFileTimestamp( array $params );
 895
 896         /**
 897          * Get the contents of a file at a storage path in the backend.
 898          * This should be avoided for potentially large files.
 899          *
 900          * @param array $params Parameters include:
 901          *   - src    : source storage path
 902          *   - latest : use the latest available data
 903          * @return string|bool Returns false on failure
 904          */
 905         final public function getFileContents( array $params ) {
 906                 $contents = $this->getFileContentsMulti(
 907                         array( 'srcs' => array( $params['src'] ) ) + $params );
 908
 909                 return $contents[$params['src']];
 910         }
 911
 912         /**
 913          * Like getFileContents() except it takes an array of storage paths
 914          * and returns a map of storage paths to strings (or null on failure).
 915          * The map keys (paths) are in the same order as the provided list of paths.
 916          *
 917          * @see FileBackend::getFileContents()
 918          *
 919          * @param array $params Parameters include:
 920          *   - srcs        : list of source storage paths
 921          *   - latest      : use the latest available data
 922          *   - parallelize : try to do operations in parallel when possible
 923          * @return array Map of (path name => string or false on failure)
 924          * @since 1.20
 925          */
 926         abstract public function getFileContentsMulti( array $params );
 927
 928         /**
 929          * Get metadata about a file at a storage path in the backend.
 930          * If the file does not exist, then this returns false.
 931          * Otherwise, the result is an associative array that includes:
 932          *   - headers  : map of HTTP headers used for GET/HEAD requests (name => value)
 933          *   - metadata : map of file metadata (name => value)
 934          * Metadata keys and headers names will be returned in all lower-case.
 935          * Additional values may be included for internal use only.
 936          *
 937          * Use FileBackend::hasFeatures() to check how well this is supported.
 938          *
 939          * @param array $params
 940          * $params include:
 941          *   - src    : source storage path
 942          *   - latest : use the latest available data
 943          * @return array|bool Returns false on failure
 944          * @since 1.23
 945          */
 946         abstract public function getFileXAttributes( array $params );
 947
 948         /**
 949          * Get the size (bytes) of a file at a storage path in the backend.
 950          *
 951          * @param array $params Parameters include:
 952          *   - src    : source storage path
 953          *   - latest : use the latest available data
 954          * @return int|bool Returns false on failure
 955          */
 956         abstract public function getFileSize( array $params );
 957
 958         /**
 959          * Get quick information about a file at a storage path in the backend.
 960          * If the file does not exist, then this returns false.
 961          * Otherwise, the result is an associative array that includes:
 962          *   - mtime  : the last-modified timestamp (TS_MW)
 963          *   - size   : the file size (bytes)
 964          * Additional values may be included for internal use only.
 965          *
 966          * @param array $params Parameters include:
 967          *   - src    : source storage path
 968          *   - latest : use the latest available data
 969          * @return array|bool|null Returns null on failure
 970          */
 971         abstract public function getFileStat( array $params );
 972
 973         /**
 974          * Get a SHA-1 hash of the file at a storage path in the backend.
 975          *
 976          * @param array $params Parameters include:
 977          *   - src    : source storage path
 978          *   - latest : use the latest available data
 979          * @return string|bool Hash string or false on failure
 980          */
 981         abstract public function getFileSha1Base36( array $params );
 982
 983         /**
 984          * Get the properties of the file at a storage path in the backend.
 985          * This gives the result of FSFile::getProps() on a local copy of the file.
 986          *
 987          * @param array $params Parameters include:
 988          *   - src    : source storage path
 989          *   - latest : use the latest available data
 990          * @return array Returns FSFile::placeholderProps() on failure
 991          */
 992         abstract public function getFileProps( array $params );
 993
 994         /**
 995          * Stream the file at a storage path in the backend.
 996          * If the file does not exists, an HTTP 404 error will be given.
 997          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
 998          * will be sent if streaming began, while none will be sent otherwise.
 999          * Implementations should flush the output buffer before sending data.
1000          *
1001          * @param array $params Parameters include:
1002          *   - src     : source storage path
1003          *   - headers : list of additional HTTP headers to send on success
1004          *   - latest  : use the latest available data
1005          * @return Status
1006          */
1007         abstract public function streamFile( array $params );
1008
1009         /**
1010          * Returns a file system file, identical to the file at a storage path.
1011          * The file returned is either:
1012          *   - a) A local copy of the file at a storage path in the backend.
1013          *        The temporary copy will have the same extension as the source.
1014          *   - b) An original of the file at a storage path in the backend.
1015          * Temporary files may be purged when the file object falls out of scope.
1016          *
1017          * Write operations should *never* be done on this file as some backends
1018          * may do internal tracking or may be instances of FileBackendMultiWrite.
1019          * In that later case, there are copies of the file that must stay in sync.
1020          * Additionally, further calls to this function may return the same file.
1021          *
1022          * @param array $params Parameters include:
1023          *   - src    : source storage path
1024          *   - latest : use the latest available data
1025          * @return FSFile|null Returns null on failure
1026          */
1027         final public function getLocalReference( array $params ) {
1028                 $fsFiles = $this->getLocalReferenceMulti(
1029                         array( 'srcs' => array( $params['src'] ) ) + $params );
1030
1031                 return $fsFiles[$params['src']];
1032         }
1033
1034         /**
1035          * Like getLocalReference() except it takes an array of storage paths
1036          * and returns a map of storage paths to FSFile objects (or null on failure).
1037          * The map keys (paths) are in the same order as the provided list of paths.
1038          *
1039          * @see FileBackend::getLocalReference()
1040          *
1041          * @param array $params Parameters include:
1042          *   - srcs        : list of source storage paths
1043          *   - latest      : use the latest available data
1044          *   - parallelize : try to do operations in parallel when possible
1045          * @return array Map of (path name => FSFile or null on failure)
1046          * @since 1.20
1047          */
1048         abstract public function getLocalReferenceMulti( array $params );
1049
1050         /**
1051          * Get a local copy on disk of the file at a storage path in the backend.
1052          * The temporary copy will have the same file extension as the source.
1053          * Temporary files may be purged when the file object falls out of scope.
1054          *
1055          * @param array $params Parameters include:
1056          *   - src    : source storage path
1057          *   - latest : use the latest available data
1058          * @return TempFSFile|null Returns null on failure
1059          */
1060         final public function getLocalCopy( array $params ) {
1061                 $tmpFiles = $this->getLocalCopyMulti(
1062                         array( 'srcs' => array( $params['src'] ) ) + $params );
1063
1064                 return $tmpFiles[$params['src']];
1065         }
1066
1067         /**
1068          * Like getLocalCopy() except it takes an array of storage paths and
1069          * returns a map of storage paths to TempFSFile objects (or null on failure).
1070          * The map keys (paths) are in the same order as the provided list of paths.
1071          *
1072          * @see FileBackend::getLocalCopy()
1073          *
1074          * @param array $params Parameters include:
1075          *   - srcs        : list of source storage paths
1076          *   - latest      : use the latest available data
1077          *   - parallelize : try to do operations in parallel when possible
1078          * @return array Map of (path name => TempFSFile or null on failure)
1079          * @since 1.20
1080          */
1081         abstract public function getLocalCopyMulti( array $params );
1082
1083         /**
1084          * Return an HTTP URL to a given file that requires no authentication to use.
1085          * The URL may be pre-authenticated (via some token in the URL) and temporary.
1086          * This will return null if the backend cannot make an HTTP URL for the file.
1087          *
1088          * This is useful for key/value stores when using scripts that seek around
1089          * large files and those scripts (and the backend) support HTTP Range headers.
1090          * Otherwise, one would need to use getLocalReference(), which involves loading
1091          * the entire file on to local disk.
1092          *
1093          * @param array $params Parameters include:
1094          *   - src : source storage path
1095          *   - ttl : lifetime (seconds) if pre-authenticated; default is 1 day
1096          * @return string|null
1097          * @since 1.21
1098          */
1099         abstract public function getFileHttpUrl( array $params );
1100
1101         /**
1102          * Check if a directory exists at a given storage path.
1103          * Backends using key/value stores will check if the path is a
1104          * virtual directory, meaning there are files under the given directory.
1105          *
1106          * Storage backends with eventual consistency might return stale data.
1107          *
1108          * @param array $params Parameters include:
1109          *   - dir : storage directory
1110          * @return bool|null Returns null on failure
1111          * @since 1.20
1112          */
1113         abstract public function directoryExists( array $params );
1114
1115         /**
1116          * Get an iterator to list *all* directories under a storage directory.
1117          * If the directory is of the form "mwstore://backend/container",
1118          * then all directories in the container will be listed.
1119          * If the directory is of form "mwstore://backend/container/dir",
1120          * then all directories directly under that directory will be listed.
1121          * Results will be storage directories relative to the given directory.
1122          *
1123          * Storage backends with eventual consistency might return stale data.
1124          *
1125          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1126          *
1127          * @param array $params Parameters include:
1128          *   - dir     : storage directory
1129          *   - topOnly : only return direct child dirs of the directory
1130          * @return Traversable|array|null Returns null on failure
1131          * @since 1.20
1132          */
1133         abstract public function getDirectoryList( array $params );
1134
1135         /**
1136          * Same as FileBackend::getDirectoryList() except only lists
1137          * directories that are immediately under the given directory.
1138          *
1139          * Storage backends with eventual consistency might return stale data.
1140          *
1141          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1142          *
1143          * @param array $params Parameters include:
1144          *   - dir : storage directory
1145          * @return Traversable|array|null Returns null on failure
1146          * @since 1.20
1147          */
1148         final public function getTopDirectoryList( array $params ) {
1149                 return $this->getDirectoryList( array( 'topOnly' => true ) + $params );
1150         }
1151
1152         /**
1153          * Get an iterator to list *all* stored files under a storage directory.
1154          * If the directory is of the form "mwstore://backend/container",
1155          * then all files in the container will be listed.
1156          * If the directory is of form "mwstore://backend/container/dir",
1157          * then all files under that directory will be listed.
1158          * Results will be storage paths relative to the given directory.
1159          *
1160          * Storage backends with eventual consistency might return stale data.
1161          *
1162          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1163          *
1164          * @param array $params Parameters include:
1165          *   - dir        : storage directory
1166          *   - topOnly    : only return direct child files of the directory (since 1.20)
1167          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1168          * @return Traversable|array|null Returns null on failure
1169          */
1170         abstract public function getFileList( array $params );
1171
1172         /**
1173          * Same as FileBackend::getFileList() except only lists
1174          * files that are immediately under the given directory.
1175          *
1176          * Storage backends with eventual consistency might return stale data.
1177          *
1178          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1179          *
1180          * @param array $params Parameters include:
1181          *   - dir        : storage directory
1182          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1183          * @return Traversable|array|null Returns null on failure
1184          * @since 1.20
1185          */
1186         final public function getTopFileList( array $params ) {
1187                 return $this->getFileList( array( 'topOnly' => true ) + $params );
1188         }
1189
1190         /**
1191          * Preload persistent file stat cache and property cache into in-process cache.
1192          * This should be used when stat calls will be made on a known list of a many files.
1193          *
1194          * @see FileBackend::getFileStat()
1195          *
1196          * @param array $paths Storage paths
1197          */
1198         abstract public function preloadCache( array $paths );
1199
1200         /**
1201          * Invalidate any in-process file stat and property cache.
1202          * If $paths is given, then only the cache for those files will be cleared.
1203          *
1204          * @see FileBackend::getFileStat()
1205          *
1206          * @param array $paths Storage paths (optional)
1207          */
1208         abstract public function clearCache( array $paths = null );
1209
1210         /**
1211          * Preload file stat information (concurrently if possible) into in-process cache.
1212          *
1213          * This should be used when stat calls will be made on a known list of a many files.
1214          * This does not make use of the persistent file stat cache.
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 ScopedLock|null
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 Exception {
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 }