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         /** @var callable */
 108         protected $statusWrapper;
 109
 110         /** Bitfield flags for supported features */
 111         const ATTR_HEADERS = 1; // files can be tagged with standard HTTP headers
 112         const ATTR_METADATA = 2; // files can be stored with metadata key/values
 113         const ATTR_UNICODE_PATHS = 4; // files can have Unicode paths (not just ASCII)
 114
 115         /**
 116          * Create a new backend instance from configuration.
 117          * This should only be called from within FileBackendGroup.
 118          *
 119          * @param array $config Parameters include:
 120          *   - name        : The unique name of this backend.
 121          *                   This should consist of alphanumberic, '-', and '_' characters.
 122          *                   This name should not be changed after use (e.g. with journaling).
 123          *                   Note that the name is *not* used in actual container names.
 124          *   - wikiId      : Prefix to container names that is unique to this backend.
 125          *                   It should only consist of alphanumberic, '-', and '_' characters.
 126          *                   This ID is what avoids collisions if multiple logical backends
 127          *                   use the same storage system, so this should be set carefully.
 128          *   - lockManager : LockManager object to use for any file locking.
 129          *                   If not provided, then no file locking will be enforced.
 130          *   - fileJournal : FileJournal object to use for logging changes to files.
 131          *                   If not provided, then change journaling will be disabled.
 132          *   - readOnly    : Write operations are disallowed if this is a non-empty string.
 133          *                   It should be an explanation for the backend being read-only.
 134          *   - parallelize : When to do file operations in parallel (when possible).
 135          *                   Allowed values are "implicit", "explicit" and "off".
 136          *   - concurrency : How many file operations can be done in parallel.
 137          * @throws FileBackendException
 138          */
 139         public function __construct( array $config ) {
 140                 $this->name = $config['name'];
 141                 $this->wikiId = $config['wikiId']; // e.g. "my_wiki-en_"
 142                 if ( !preg_match( '!^[a-zA-Z0-9-_]{1,255}$!', $this->name ) ) {
 143                         throw new FileBackendException( "Backend name '{$this->name}' is invalid." );
 144                 } elseif ( !is_string( $this->wikiId ) ) {
 145                         throw new FileBackendException( "Backend wiki ID not provided for '{$this->name}'." );
 146                 }
 147                 $this->lockManager = isset( $config['lockManager'] )
 148                         ? $config['lockManager']
 149                         : new NullLockManager( [] );
 150                 $this->fileJournal = isset( $config['fileJournal'] )
 151                         ? $config['fileJournal']
 152                         : FileJournal::factory( [ 'class' => 'NullFileJournal' ], $this->name );
 153                 $this->readOnly = isset( $config['readOnly'] )
 154                         ? (string)$config['readOnly']
 155                         : '';
 156                 $this->parallelize = isset( $config['parallelize'] )
 157                         ? (string)$config['parallelize']
 158                         : 'off';
 159                 $this->concurrency = isset( $config['concurrency'] )
 160                         ? (int)$config['concurrency']
 161                         : 50;
 162                 // @TODO: dependency inject this
 163                 $this->statusWrapper = [ 'Status', 'wrap' ];
 164         }
 165
 166         /**
 167          * Get the unique backend name.
 168          * We may have multiple different backends of the same type.
 169          * For example, we can have two Swift backends using different proxies.
 170          *
 171          * @return string
 172          */
 173         final public function getName() {
 174                 return $this->name;
 175         }
 176
 177         /**
 178          * Get the wiki identifier used for this backend (possibly empty).
 179          * Note that this might *not* be in the same format as wfWikiID().
 180          *
 181          * @return string
 182          * @since 1.20
 183          */
 184         final public function getWikiId() {
 185                 return $this->wikiId;
 186         }
 187
 188         /**
 189          * Check if this backend is read-only
 190          *
 191          * @return bool
 192          */
 193         final public function isReadOnly() {
 194                 return ( $this->readOnly != '' );
 195         }
 196
 197         /**
 198          * Get an explanatory message if this backend is read-only
 199          *
 200          * @return string|bool Returns false if the backend is not read-only
 201          */
 202         final public function getReadOnlyReason() {
 203                 return ( $this->readOnly != '' ) ? $this->readOnly : false;
 204         }
 205
 206         /**
 207          * Get the a bitfield of extra features supported by the backend medium
 208          *
 209          * @return int Bitfield of FileBackend::ATTR_* flags
 210          * @since 1.23
 211          */
 212         public function getFeatures() {
 213                 return self::ATTR_UNICODE_PATHS;
 214         }
 215
 216         /**
 217          * Check if the backend medium supports a field of extra features
 218          *
 219          * @param int $bitfield Bitfield of FileBackend::ATTR_* flags
 220          * @return bool
 221          * @since 1.23
 222          */
 223         final public function hasFeatures( $bitfield ) {
 224                 return ( $this->getFeatures() & $bitfield ) === $bitfield;
 225         }
 226
 227         /**
 228          * This is the main entry point into the backend for write operations.
 229          * Callers supply an ordered list of operations to perform as a transaction.
 230          * Files will be locked, the stat cache cleared, and then the operations attempted.
 231          * If any serious errors occur, all attempted operations will be rolled back.
 232          *
 233          * $ops is an array of arrays. The outer array holds a list of operations.
 234          * Each inner array is a set of key value pairs that specify an operation.
 235          *
 236          * Supported operations and their parameters. The supported actions are:
 237          *  - create
 238          *  - store
 239          *  - copy
 240          *  - move
 241          *  - delete
 242          *  - describe (since 1.21)
 243          *  - null
 244          *
 245          * FSFile/TempFSFile object support was added in 1.27.
 246          *
 247          * a) Create a new file in storage with the contents of a string
 248          * @code
 249          *     [
 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          *     [
 262          *         'op'                  => 'store',
 263          *         'src'                 => <file system path, FSFile, or TempFSFile>,
 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          *     [
 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          *     [
 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          *     [
 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          *     [
 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          *     [
 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 StatusValue 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 StatusValue
 374          */
 375         final public function doOperations( array $ops, array $opts = [] ) {
 376                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 377                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 378                 }
 379                 if ( !count( $ops ) ) {
 380                         return $this->newStatus(); // nothing to do
 381                 }
 382
 383                 $ops = $this->resolveFSFileObjects( $ops );
 384                 if ( empty( $opts['force'] ) ) { // sanity
 385                         unset( $opts['nonLocking'] );
 386                 }
 387
 388                 /** @noinspection PhpUnusedLocalVariableInspection */
 389                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 390
 391                 return $this->doOperationsInternal( $ops, $opts );
 392         }
 393
 394         /**
 395          * @see FileBackend::doOperations()
 396          * @param array $ops
 397          * @param array $opts
 398          */
 399         abstract protected function doOperationsInternal( array $ops, array $opts );
 400
 401         /**
 402          * Same as doOperations() except it takes a single operation.
 403          * If you are doing a batch of operations that should either
 404          * all succeed or all fail, then use that function instead.
 405          *
 406          * @see FileBackend::doOperations()
 407          *
 408          * @param array $op Operation
 409          * @param array $opts Operation options
 410          * @return StatusValue
 411          */
 412         final public function doOperation( array $op, array $opts = [] ) {
 413                 return $this->doOperations( [ $op ], $opts );
 414         }
 415
 416         /**
 417          * Performs a single create operation.
 418          * This sets $params['op'] to 'create' and passes it to doOperation().
 419          *
 420          * @see FileBackend::doOperation()
 421          *
 422          * @param array $params Operation parameters
 423          * @param array $opts Operation options
 424          * @return StatusValue
 425          */
 426         final public function create( array $params, array $opts = [] ) {
 427                 return $this->doOperation( [ 'op' => 'create' ] + $params, $opts );
 428         }
 429
 430         /**
 431          * Performs a single store operation.
 432          * This sets $params['op'] to 'store' and passes it to doOperation().
 433          *
 434          * @see FileBackend::doOperation()
 435          *
 436          * @param array $params Operation parameters
 437          * @param array $opts Operation options
 438          * @return StatusValue
 439          */
 440         final public function store( array $params, array $opts = [] ) {
 441                 return $this->doOperation( [ 'op' => 'store' ] + $params, $opts );
 442         }
 443
 444         /**
 445          * Performs a single copy operation.
 446          * This sets $params['op'] to 'copy' and passes it to doOperation().
 447          *
 448          * @see FileBackend::doOperation()
 449          *
 450          * @param array $params Operation parameters
 451          * @param array $opts Operation options
 452          * @return StatusValue
 453          */
 454         final public function copy( array $params, array $opts = [] ) {
 455                 return $this->doOperation( [ 'op' => 'copy' ] + $params, $opts );
 456         }
 457
 458         /**
 459          * Performs a single move operation.
 460          * This sets $params['op'] to 'move' and passes it to doOperation().
 461          *
 462          * @see FileBackend::doOperation()
 463          *
 464          * @param array $params Operation parameters
 465          * @param array $opts Operation options
 466          * @return StatusValue
 467          */
 468         final public function move( array $params, array $opts = [] ) {
 469                 return $this->doOperation( [ 'op' => 'move' ] + $params, $opts );
 470         }
 471
 472         /**
 473          * Performs a single delete operation.
 474          * This sets $params['op'] to 'delete' and passes it to doOperation().
 475          *
 476          * @see FileBackend::doOperation()
 477          *
 478          * @param array $params Operation parameters
 479          * @param array $opts Operation options
 480          * @return StatusValue
 481          */
 482         final public function delete( array $params, array $opts = [] ) {
 483                 return $this->doOperation( [ 'op' => 'delete' ] + $params, $opts );
 484         }
 485
 486         /**
 487          * Performs a single describe operation.
 488          * This sets $params['op'] to 'describe' and passes it to doOperation().
 489          *
 490          * @see FileBackend::doOperation()
 491          *
 492          * @param array $params Operation parameters
 493          * @param array $opts Operation options
 494          * @return StatusValue
 495          * @since 1.21
 496          */
 497         final public function describe( array $params, array $opts = [] ) {
 498                 return $this->doOperation( [ 'op' => 'describe' ] + $params, $opts );
 499         }
 500
 501         /**
 502          * Perform a set of independent file operations on some files.
 503          *
 504          * This does no locking, nor journaling, and possibly no stat calls.
 505          * Any destination files that already exist will be overwritten.
 506          * This should *only* be used on non-original files, like cache files.
 507          *
 508          * Supported operations and their parameters:
 509          *  - create
 510          *  - store
 511          *  - copy
 512          *  - move
 513          *  - delete
 514          *  - describe (since 1.21)
 515          *  - null
 516          *
 517          * FSFile/TempFSFile object support was added in 1.27.
 518          *
 519          * a) Create a new file in storage with the contents of a string
 520          * @code
 521          *     [
 522          *         'op'                  => 'create',
 523          *         'dst'                 => <storage path>,
 524          *         'content'             => <string of new file contents>,
 525          *         'headers'             => <HTTP header name/value map> # since 1.21
 526          *     ]
 527          * @endcode
 528          *
 529          * b) Copy a file system file into storage
 530          * @code
 531          *     [
 532          *         'op'                  => 'store',
 533          *         'src'                 => <file system path, FSFile, or TempFSFile>,
 534          *         'dst'                 => <storage path>,
 535          *         'headers'             => <HTTP header name/value map> # since 1.21
 536          *     ]
 537          * @endcode
 538          *
 539          * c) Copy a file within storage
 540          * @code
 541          *     [
 542          *         'op'                  => 'copy',
 543          *         'src'                 => <storage path>,
 544          *         'dst'                 => <storage path>,
 545          *         'ignoreMissingSource' => <boolean>, # since 1.21
 546          *         'headers'             => <HTTP header name/value map> # since 1.21
 547          *     ]
 548          * @endcode
 549          *
 550          * d) Move a file within storage
 551          * @code
 552          *     [
 553          *         'op'                  => 'move',
 554          *         'src'                 => <storage path>,
 555          *         'dst'                 => <storage path>,
 556          *         'ignoreMissingSource' => <boolean>, # since 1.21
 557          *         'headers'             => <HTTP header name/value map> # since 1.21
 558          *     ]
 559          * @endcode
 560          *
 561          * e) Delete a file within storage
 562          * @code
 563          *     [
 564          *         'op'                  => 'delete',
 565          *         'src'                 => <storage path>,
 566          *         'ignoreMissingSource' => <boolean>
 567          *     ]
 568          * @endcode
 569          *
 570          * f) Update metadata for a file within storage
 571          * @code
 572          *     [
 573          *         'op'                  => 'describe',
 574          *         'src'                 => <storage path>,
 575          *         'headers'             => <HTTP header name/value map>
 576          *     ]
 577          * @endcode
 578          *
 579          * g) Do nothing (no-op)
 580          * @code
 581          *     [
 582          *         'op'                  => 'null',
 583          *     ]
 584          * @endcode
 585          *
 586          * @par Boolean flags for operations (operation-specific):
 587          *   - ignoreMissingSource : The operation will simply succeed and do
 588          *                           nothing if the source file does not exist.
 589          *   - headers             : If supplied with a header name/value map, the backend will
 590          *                           reply with these headers when GETs/HEADs of the destination
 591          *                           file are made. Header values should be smaller than 256 bytes.
 592          *                           Content-Disposition headers can be longer, though the system
 593          *                           might ignore or truncate ones that are too long to store.
 594          *                           Existing headers will remain, but these will replace any
 595          *                           conflicting previous headers, and headers will be removed
 596          *                           if they are set to an empty string.
 597          *                           Backends that don't support metadata ignore this. (since 1.21)
 598          *
 599          * $opts is an associative of boolean flags, including:
 600          *   - bypassReadOnly      : Allow writes in read-only mode (since 1.20)
 601          *
 602          * @par Return value:
 603          * This returns a Status, which contains all warnings and fatals that occurred
 604          * during the operation. The 'failCount', 'successCount', and 'success' members
 605          * will reflect each operation attempted for the given files. The StatusValue will be
 606          * considered "OK" as long as no fatal errors occurred.
 607          *
 608          * @param array $ops Set of operations to execute
 609          * @param array $opts Batch operation options
 610          * @return StatusValue
 611          * @since 1.20
 612          */
 613         final public function doQuickOperations( array $ops, array $opts = [] ) {
 614                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 615                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 616                 }
 617                 if ( !count( $ops ) ) {
 618                         return $this->newStatus(); // nothing to do
 619                 }
 620
 621                 $ops = $this->resolveFSFileObjects( $ops );
 622                 foreach ( $ops as &$op ) {
 623                         $op['overwrite'] = true; // avoids RTTs in key/value stores
 624                 }
 625
 626                 /** @noinspection PhpUnusedLocalVariableInspection */
 627                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 628
 629                 return $this->doQuickOperationsInternal( $ops );
 630         }
 631
 632         /**
 633          * @see FileBackend::doQuickOperations()
 634          * @param array $ops
 635          * @since 1.20
 636          */
 637         abstract protected function doQuickOperationsInternal( array $ops );
 638
 639         /**
 640          * Same as doQuickOperations() except it takes a single operation.
 641          * If you are doing a batch of operations, then use that function instead.
 642          *
 643          * @see FileBackend::doQuickOperations()
 644          *
 645          * @param array $op Operation
 646          * @return StatusValue
 647          * @since 1.20
 648          */
 649         final public function doQuickOperation( array $op ) {
 650                 return $this->doQuickOperations( [ $op ] );
 651         }
 652
 653         /**
 654          * Performs a single quick create operation.
 655          * This sets $params['op'] to 'create' and passes it to doQuickOperation().
 656          *
 657          * @see FileBackend::doQuickOperation()
 658          *
 659          * @param array $params Operation parameters
 660          * @return StatusValue
 661          * @since 1.20
 662          */
 663         final public function quickCreate( array $params ) {
 664                 return $this->doQuickOperation( [ 'op' => 'create' ] + $params );
 665         }
 666
 667         /**
 668          * Performs a single quick store operation.
 669          * This sets $params['op'] to 'store' and passes it to doQuickOperation().
 670          *
 671          * @see FileBackend::doQuickOperation()
 672          *
 673          * @param array $params Operation parameters
 674          * @return StatusValue
 675          * @since 1.20
 676          */
 677         final public function quickStore( array $params ) {
 678                 return $this->doQuickOperation( [ 'op' => 'store' ] + $params );
 679         }
 680
 681         /**
 682          * Performs a single quick copy operation.
 683          * This sets $params['op'] to 'copy' and passes it to doQuickOperation().
 684          *
 685          * @see FileBackend::doQuickOperation()
 686          *
 687          * @param array $params Operation parameters
 688          * @return StatusValue
 689          * @since 1.20
 690          */
 691         final public function quickCopy( array $params ) {
 692                 return $this->doQuickOperation( [ 'op' => 'copy' ] + $params );
 693         }
 694
 695         /**
 696          * Performs a single quick move operation.
 697          * This sets $params['op'] to 'move' and passes it to doQuickOperation().
 698          *
 699          * @see FileBackend::doQuickOperation()
 700          *
 701          * @param array $params Operation parameters
 702          * @return StatusValue
 703          * @since 1.20
 704          */
 705         final public function quickMove( array $params ) {
 706                 return $this->doQuickOperation( [ 'op' => 'move' ] + $params );
 707         }
 708
 709         /**
 710          * Performs a single quick delete operation.
 711          * This sets $params['op'] to 'delete' and passes it to doQuickOperation().
 712          *
 713          * @see FileBackend::doQuickOperation()
 714          *
 715          * @param array $params Operation parameters
 716          * @return StatusValue
 717          * @since 1.20
 718          */
 719         final public function quickDelete( array $params ) {
 720                 return $this->doQuickOperation( [ 'op' => 'delete' ] + $params );
 721         }
 722
 723         /**
 724          * Performs a single quick describe operation.
 725          * This sets $params['op'] to 'describe' and passes it to doQuickOperation().
 726          *
 727          * @see FileBackend::doQuickOperation()
 728          *
 729          * @param array $params Operation parameters
 730          * @return StatusValue
 731          * @since 1.21
 732          */
 733         final public function quickDescribe( array $params ) {
 734                 return $this->doQuickOperation( [ 'op' => 'describe' ] + $params );
 735         }
 736
 737         /**
 738          * Concatenate a list of storage files into a single file system file.
 739          * The target path should refer to a file that is already locked or
 740          * otherwise safe from modification from other processes. Normally,
 741          * the file will be a new temp file, which should be adequate.
 742          *
 743          * @param array $params Operation parameters, include:
 744          *   - srcs        : ordered source storage paths (e.g. chunk1, chunk2, ...)
 745          *   - dst         : file system path to 0-byte temp file
 746          *   - parallelize : try to do operations in parallel when possible
 747          * @return StatusValue
 748          */
 749         abstract public function concatenate( array $params );
 750
 751         /**
 752          * Prepare a storage directory for usage.
 753          * This will create any required containers and parent directories.
 754          * Backends using key/value stores only need to create the container.
 755          *
 756          * The 'noAccess' and 'noListing' parameters works the same as in secure(),
 757          * except they are only applied *if* the directory/container had to be created.
 758          * These flags should always be set for directories that have private files.
 759          * However, setting them is not guaranteed to actually do anything.
 760          * Additional server configuration may be needed to achieve the desired effect.
 761          *
 762          * @param array $params Parameters include:
 763          *   - dir            : storage directory
 764          *   - noAccess       : try to deny file access (since 1.20)
 765          *   - noListing      : try to deny file listing (since 1.20)
 766          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 767          * @return StatusValue
 768          */
 769         final public function prepare( array $params ) {
 770                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 771                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 772                 }
 773                 /** @noinspection PhpUnusedLocalVariableInspection */
 774                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 775                 return $this->doPrepare( $params );
 776         }
 777
 778         /**
 779          * @see FileBackend::prepare()
 780          * @param array $params
 781          */
 782         abstract protected function doPrepare( array $params );
 783
 784         /**
 785          * Take measures to block web access to a storage directory and
 786          * the container it belongs to. FS backends might add .htaccess
 787          * files whereas key/value store backends might revoke container
 788          * access to the storage user representing end-users in web requests.
 789          *
 790          * This is not guaranteed to actually make files or listings publically hidden.
 791          * Additional server configuration may be needed to achieve the desired effect.
 792          *
 793          * @param array $params Parameters include:
 794          *   - dir            : storage directory
 795          *   - noAccess       : try to deny file access
 796          *   - noListing      : try to deny file listing
 797          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 798          * @return StatusValue
 799          */
 800         final public function secure( array $params ) {
 801                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 802                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 803                 }
 804                 /** @noinspection PhpUnusedLocalVariableInspection */
 805                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 806                 return $this->doSecure( $params );
 807         }
 808
 809         /**
 810          * @see FileBackend::secure()
 811          * @param array $params
 812          */
 813         abstract protected function doSecure( array $params );
 814
 815         /**
 816          * Remove measures to block web access to a storage directory and
 817          * the container it belongs to. FS backends might remove .htaccess
 818          * files whereas key/value store backends might grant container
 819          * access to the storage user representing end-users in web requests.
 820          * This essentially can undo the result of secure() calls.
 821          *
 822          * This is not guaranteed to actually make files or listings publically viewable.
 823          * Additional server configuration may be needed to achieve the desired effect.
 824          *
 825          * @param array $params Parameters include:
 826          *   - dir            : storage directory
 827          *   - access         : try to allow file access
 828          *   - listing        : try to allow file listing
 829          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 830          * @return StatusValue
 831          * @since 1.20
 832          */
 833         final public function publish( array $params ) {
 834                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 835                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 836                 }
 837                 /** @noinspection PhpUnusedLocalVariableInspection */
 838                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 839                 return $this->doPublish( $params );
 840         }
 841
 842         /**
 843          * @see FileBackend::publish()
 844          * @param array $params
 845          */
 846         abstract protected function doPublish( array $params );
 847
 848         /**
 849          * Delete a storage directory if it is empty.
 850          * Backends using key/value stores may do nothing unless the directory
 851          * is that of an empty container, in which case it will be deleted.
 852          *
 853          * @param array $params Parameters include:
 854          *   - dir            : storage directory
 855          *   - recursive      : recursively delete empty subdirectories first (since 1.20)
 856          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 857          * @return StatusValue
 858          */
 859         final public function clean( array $params ) {
 860                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 861                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 862                 }
 863                 /** @noinspection PhpUnusedLocalVariableInspection */
 864                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 865                 return $this->doClean( $params );
 866         }
 867
 868         /**
 869          * @see FileBackend::clean()
 870          * @param array $params
 871          */
 872         abstract protected function doClean( array $params );
 873
 874         /**
 875          * Enter file operation scope.
 876          * This just makes PHP ignore user aborts/disconnects until the return
 877          * value leaves scope. This returns null and does nothing in CLI mode.
 878          *
 879          * @return ScopedCallback|null
 880          */
 881         final protected function getScopedPHPBehaviorForOps() {
 882                 if ( PHP_SAPI != 'cli' ) { // http://bugs.php.net/bug.php?id=47540
 883                         $old = ignore_user_abort( true ); // avoid half-finished operations
 884                         return new ScopedCallback( function () use ( $old ) {
 885                                 ignore_user_abort( $old );
 886                         } );
 887                 }
 888
 889                 return null;
 890         }
 891
 892         /**
 893          * Check if a file exists at a storage path in the backend.
 894          * This returns false if only a directory exists at the path.
 895          *
 896          * @param array $params Parameters include:
 897          *   - src    : source storage path
 898          *   - latest : use the latest available data
 899          * @return bool|null Returns null on failure
 900          */
 901         abstract public function fileExists( array $params );
 902
 903         /**
 904          * Get the last-modified timestamp of the file at a storage path.
 905          *
 906          * @param array $params Parameters include:
 907          *   - src    : source storage path
 908          *   - latest : use the latest available data
 909          * @return string|bool TS_MW timestamp or false on failure
 910          */
 911         abstract public function getFileTimestamp( array $params );
 912
 913         /**
 914          * Get the contents of a file at a storage path in the backend.
 915          * This should be avoided for potentially large files.
 916          *
 917          * @param array $params Parameters include:
 918          *   - src    : source storage path
 919          *   - latest : use the latest available data
 920          * @return string|bool Returns false on failure
 921          */
 922         final public function getFileContents( array $params ) {
 923                 $contents = $this->getFileContentsMulti(
 924                         [ 'srcs' => [ $params['src'] ] ] + $params );
 925
 926                 return $contents[$params['src']];
 927         }
 928
 929         /**
 930          * Like getFileContents() except it takes an array of storage paths
 931          * and returns a map of storage paths to strings (or null on failure).
 932          * The map keys (paths) are in the same order as the provided list of paths.
 933          *
 934          * @see FileBackend::getFileContents()
 935          *
 936          * @param array $params Parameters include:
 937          *   - srcs        : list of source storage paths
 938          *   - latest      : use the latest available data
 939          *   - parallelize : try to do operations in parallel when possible
 940          * @return array Map of (path name => string or false on failure)
 941          * @since 1.20
 942          */
 943         abstract public function getFileContentsMulti( array $params );
 944
 945         /**
 946          * Get metadata about a file at a storage path in the backend.
 947          * If the file does not exist, then this returns false.
 948          * Otherwise, the result is an associative array that includes:
 949          *   - headers  : map of HTTP headers used for GET/HEAD requests (name => value)
 950          *   - metadata : map of file metadata (name => value)
 951          * Metadata keys and headers names will be returned in all lower-case.
 952          * Additional values may be included for internal use only.
 953          *
 954          * Use FileBackend::hasFeatures() to check how well this is supported.
 955          *
 956          * @param array $params
 957          * $params include:
 958          *   - src    : source storage path
 959          *   - latest : use the latest available data
 960          * @return array|bool Returns false on failure
 961          * @since 1.23
 962          */
 963         abstract public function getFileXAttributes( array $params );
 964
 965         /**
 966          * Get the size (bytes) of a file at a storage path in the backend.
 967          *
 968          * @param array $params Parameters include:
 969          *   - src    : source storage path
 970          *   - latest : use the latest available data
 971          * @return int|bool Returns false on failure
 972          */
 973         abstract public function getFileSize( array $params );
 974
 975         /**
 976          * Get quick information about a file at a storage path in the backend.
 977          * If the file does not exist, then this returns false.
 978          * Otherwise, the result is an associative array that includes:
 979          *   - mtime  : the last-modified timestamp (TS_MW)
 980          *   - size   : the file size (bytes)
 981          * Additional values may be included for internal use only.
 982          *
 983          * @param array $params Parameters include:
 984          *   - src    : source storage path
 985          *   - latest : use the latest available data
 986          * @return array|bool|null Returns null on failure
 987          */
 988         abstract public function getFileStat( array $params );
 989
 990         /**
 991          * Get a SHA-1 hash of the file at a storage path in the backend.
 992          *
 993          * @param array $params Parameters include:
 994          *   - src    : source storage path
 995          *   - latest : use the latest available data
 996          * @return string|bool Hash string or false on failure
 997          */
 998         abstract public function getFileSha1Base36( array $params );
 999
1000         /**
1001          * Get the properties of the file at a storage path in the backend.
1002          * This gives the result of FSFile::getProps() on a local copy of the file.
1003          *
1004          * @param array $params Parameters include:
1005          *   - src    : source storage path
1006          *   - latest : use the latest available data
1007          * @return array Returns FSFile::placeholderProps() on failure
1008          */
1009         abstract public function getFileProps( array $params );
1010
1011         /**
1012          * Stream the file at a storage path in the backend.
1013          *
1014          * If the file does not exists, an HTTP 404 error will be given.
1015          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
1016          * will be sent if streaming began, while none will be sent otherwise.
1017          * Implementations should flush the output buffer before sending data.
1018          *
1019          * @param array $params Parameters include:
1020          *   - src      : source storage path
1021          *   - headers  : list of additional HTTP headers to send if the file exists
1022          *   - options  : HTTP request header map with lower case keys (since 1.28). Supports:
1023          *                range             : format is "bytes=(\d*-\d*)"
1024          *                if-modified-since : format is an HTTP date
1025          *   - headless : only include the body (and headers from "headers") (since 1.28)
1026          *   - latest   : use the latest available data
1027          *   - allowOB  : preserve any output buffers (since 1.28)
1028          * @return StatusValue
1029          */
1030         abstract public function streamFile( array $params );
1031
1032         /**
1033          * Returns a file system file, identical to the file at a storage path.
1034          * The file returned is either:
1035          *   - a) A local copy of the file at a storage path in the backend.
1036          *        The temporary copy will have the same extension as the source.
1037          *   - b) An original of the file at a storage path in the backend.
1038          * Temporary files may be purged when the file object falls out of scope.
1039          *
1040          * Write operations should *never* be done on this file as some backends
1041          * may do internal tracking or may be instances of FileBackendMultiWrite.
1042          * In that latter case, there are copies of the file that must stay in sync.
1043          * Additionally, further calls to this function may return the same file.
1044          *
1045          * @param array $params Parameters include:
1046          *   - src    : source storage path
1047          *   - latest : use the latest available data
1048          * @return FSFile|null Returns null on failure
1049          */
1050         final public function getLocalReference( array $params ) {
1051                 $fsFiles = $this->getLocalReferenceMulti(
1052                         [ 'srcs' => [ $params['src'] ] ] + $params );
1053
1054                 return $fsFiles[$params['src']];
1055         }
1056
1057         /**
1058          * Like getLocalReference() except it takes an array of storage paths
1059          * and returns a map of storage paths to FSFile objects (or null on failure).
1060          * The map keys (paths) are in the same order as the provided list of paths.
1061          *
1062          * @see FileBackend::getLocalReference()
1063          *
1064          * @param array $params Parameters include:
1065          *   - srcs        : list of source storage paths
1066          *   - latest      : use the latest available data
1067          *   - parallelize : try to do operations in parallel when possible
1068          * @return array Map of (path name => FSFile or null on failure)
1069          * @since 1.20
1070          */
1071         abstract public function getLocalReferenceMulti( array $params );
1072
1073         /**
1074          * Get a local copy on disk of the file at a storage path in the backend.
1075          * The temporary copy will have the same file extension as the source.
1076          * Temporary files may be purged when the file object falls out of scope.
1077          *
1078          * @param array $params Parameters include:
1079          *   - src    : source storage path
1080          *   - latest : use the latest available data
1081          * @return TempFSFile|null Returns null on failure
1082          */
1083         final public function getLocalCopy( array $params ) {
1084                 $tmpFiles = $this->getLocalCopyMulti(
1085                         [ 'srcs' => [ $params['src'] ] ] + $params );
1086
1087                 return $tmpFiles[$params['src']];
1088         }
1089
1090         /**
1091          * Like getLocalCopy() except it takes an array of storage paths and
1092          * returns a map of storage paths to TempFSFile objects (or null on failure).
1093          * The map keys (paths) are in the same order as the provided list of paths.
1094          *
1095          * @see FileBackend::getLocalCopy()
1096          *
1097          * @param array $params Parameters include:
1098          *   - srcs        : list of source storage paths
1099          *   - latest      : use the latest available data
1100          *   - parallelize : try to do operations in parallel when possible
1101          * @return array Map of (path name => TempFSFile or null on failure)
1102          * @since 1.20
1103          */
1104         abstract public function getLocalCopyMulti( array $params );
1105
1106         /**
1107          * Return an HTTP URL to a given file that requires no authentication to use.
1108          * The URL may be pre-authenticated (via some token in the URL) and temporary.
1109          * This will return null if the backend cannot make an HTTP URL for the file.
1110          *
1111          * This is useful for key/value stores when using scripts that seek around
1112          * large files and those scripts (and the backend) support HTTP Range headers.
1113          * Otherwise, one would need to use getLocalReference(), which involves loading
1114          * the entire file on to local disk.
1115          *
1116          * @param array $params Parameters include:
1117          *   - src : source storage path
1118          *   - ttl : lifetime (seconds) if pre-authenticated; default is 1 day
1119          * @return string|null
1120          * @since 1.21
1121          */
1122         abstract public function getFileHttpUrl( array $params );
1123
1124         /**
1125          * Check if a directory exists at a given storage path.
1126          * Backends using key/value stores will check if the path is a
1127          * virtual directory, meaning there are files under the given directory.
1128          *
1129          * Storage backends with eventual consistency might return stale data.
1130          *
1131          * @param array $params Parameters include:
1132          *   - dir : storage directory
1133          * @return bool|null Returns null on failure
1134          * @since 1.20
1135          */
1136         abstract public function directoryExists( array $params );
1137
1138         /**
1139          * Get an iterator to list *all* directories under a storage directory.
1140          * If the directory is of the form "mwstore://backend/container",
1141          * then all directories in the container will be listed.
1142          * If the directory is of form "mwstore://backend/container/dir",
1143          * then all directories directly under that directory will be listed.
1144          * Results will be storage directories relative to the given directory.
1145          *
1146          * Storage backends with eventual consistency might return stale data.
1147          *
1148          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1149          *
1150          * @param array $params Parameters include:
1151          *   - dir     : storage directory
1152          *   - topOnly : only return direct child dirs of the directory
1153          * @return Traversable|array|null Returns null on failure
1154          * @since 1.20
1155          */
1156         abstract public function getDirectoryList( array $params );
1157
1158         /**
1159          * Same as FileBackend::getDirectoryList() except only lists
1160          * directories that are immediately under 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          * @return Traversable|array|null Returns null on failure
1169          * @since 1.20
1170          */
1171         final public function getTopDirectoryList( array $params ) {
1172                 return $this->getDirectoryList( [ 'topOnly' => true ] + $params );
1173         }
1174
1175         /**
1176          * Get an iterator to list *all* stored files under a storage directory.
1177          * If the directory is of the form "mwstore://backend/container",
1178          * then all files in the container will be listed.
1179          * If the directory is of form "mwstore://backend/container/dir",
1180          * then all files under that directory will be listed.
1181          * Results will be storage paths relative to the given directory.
1182          *
1183          * Storage backends with eventual consistency might return stale data.
1184          *
1185          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1186          *
1187          * @param array $params Parameters include:
1188          *   - dir        : storage directory
1189          *   - topOnly    : only return direct child files of the directory (since 1.20)
1190          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1191          * @return Traversable|array|null Returns null on failure
1192          */
1193         abstract public function getFileList( array $params );
1194
1195         /**
1196          * Same as FileBackend::getFileList() except only lists
1197          * files that are immediately under the given directory.
1198          *
1199          * Storage backends with eventual consistency might return stale data.
1200          *
1201          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1202          *
1203          * @param array $params Parameters include:
1204          *   - dir        : storage directory
1205          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1206          * @return Traversable|array|null Returns null on failure
1207          * @since 1.20
1208          */
1209         final public function getTopFileList( array $params ) {
1210                 return $this->getFileList( [ 'topOnly' => true ] + $params );
1211         }
1212
1213         /**
1214          * Preload persistent file stat cache and property cache into in-process cache.
1215          * This should be used when stat calls will be made on a known list of a many files.
1216          *
1217          * @see FileBackend::getFileStat()
1218          *
1219          * @param array $paths Storage paths
1220          */
1221         abstract public function preloadCache( array $paths );
1222
1223         /**
1224          * Invalidate any in-process file stat and property cache.
1225          * If $paths is given, then only the cache for those files will be cleared.
1226          *
1227          * @see FileBackend::getFileStat()
1228          *
1229          * @param array $paths Storage paths (optional)
1230          */
1231         abstract public function clearCache( array $paths = null );
1232
1233         /**
1234          * Preload file stat information (concurrently if possible) into in-process cache.
1235          *
1236          * This should be used when stat calls will be made on a known list of a many files.
1237          * This does not make use of the persistent file stat cache.
1238          *
1239          * @see FileBackend::getFileStat()
1240          *
1241          * @param array $params Parameters include:
1242          *   - srcs        : list of source storage paths
1243          *   - latest      : use the latest available data
1244          * @return bool All requests proceeded without I/O errors (since 1.24)
1245          * @since 1.23
1246          */
1247         abstract public function preloadFileStat( array $params );
1248
1249         /**
1250          * Lock the files at the given storage paths in the backend.
1251          * This will either lock all the files or none (on failure).
1252          *
1253          * Callers should consider using getScopedFileLocks() instead.
1254          *
1255          * @param array $paths Storage paths
1256          * @param int $type LockManager::LOCK_* constant
1257          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.24)
1258          * @return StatusValue
1259          */
1260         final public function lockFiles( array $paths, $type, $timeout = 0 ) {
1261                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1262
1263                 return $this->wrapStatus( $this->lockManager->lock( $paths, $type, $timeout ) );
1264         }
1265
1266         /**
1267          * Unlock the files at the given storage paths in the backend.
1268          *
1269          * @param array $paths Storage paths
1270          * @param int $type LockManager::LOCK_* constant
1271          * @return StatusValue
1272          */
1273         final public function unlockFiles( array $paths, $type ) {
1274                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1275
1276                 return $this->wrapStatus( $this->lockManager->unlock( $paths, $type ) );
1277         }
1278
1279         /**
1280          * Lock the files at the given storage paths in the backend.
1281          * This will either lock all the files or none (on failure).
1282          * On failure, the StatusValue object will be updated with errors.
1283          *
1284          * Once the return value goes out scope, the locks will be released and
1285          * the StatusValue updated. Unlock fatals will not change the StatusValue "OK" value.
1286          *
1287          * @see ScopedLock::factory()
1288          *
1289          * @param array $paths List of storage paths or map of lock types to path lists
1290          * @param int|string $type LockManager::LOCK_* constant or "mixed"
1291          * @param StatusValue $status StatusValue to update on lock/unlock
1292          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.24)
1293          * @return ScopedLock|null Returns null on failure
1294          */
1295         final public function getScopedFileLocks(
1296                 array $paths, $type, StatusValue $status, $timeout = 0
1297         ) {
1298                 if ( $type === 'mixed' ) {
1299                         foreach ( $paths as &$typePaths ) {
1300                                 $typePaths = array_map( 'FileBackend::normalizeStoragePath', $typePaths );
1301                         }
1302                 } else {
1303                         $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1304                 }
1305
1306                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status, $timeout );
1307         }
1308
1309         /**
1310          * Get an array of scoped locks needed for a batch of file operations.
1311          *
1312          * Normally, FileBackend::doOperations() handles locking, unless
1313          * the 'nonLocking' param is passed in. This function is useful if you
1314          * want the files to be locked for a broader scope than just when the
1315          * files are changing. For example, if you need to update DB metadata,
1316          * you may want to keep the files locked until finished.
1317          *
1318          * @see FileBackend::doOperations()
1319          *
1320          * @param array $ops List of file operations to FileBackend::doOperations()
1321          * @param StatusValue $status StatusValue to update on lock/unlock
1322          * @return ScopedLock|null
1323          * @since 1.20
1324          */
1325         abstract public function getScopedLocksForOps( array $ops, StatusValue $status );
1326
1327         /**
1328          * Get the root storage path of this backend.
1329          * All container paths are "subdirectories" of this path.
1330          *
1331          * @return string Storage path
1332          * @since 1.20
1333          */
1334         final public function getRootStoragePath() {
1335                 return "mwstore://{$this->name}";
1336         }
1337
1338         /**
1339          * Get the storage path for the given container for this backend
1340          *
1341          * @param string $container Container name
1342          * @return string Storage path
1343          * @since 1.21
1344          */
1345         final public function getContainerStoragePath( $container ) {
1346                 return $this->getRootStoragePath() . "/{$container}";
1347         }
1348
1349         /**
1350          * Get the file journal object for this backend
1351          *
1352          * @return FileJournal
1353          */
1354         final public function getJournal() {
1355                 return $this->fileJournal;
1356         }
1357
1358         /**
1359          * Convert FSFile 'src' paths to string paths (with an 'srcRef' field set to the FSFile)
1360          *
1361          * The 'srcRef' field keeps any TempFSFile objects in scope for the backend to have it
1362          * around as long it needs (which may vary greatly depending on configuration)
1363          *
1364          * @param array $ops File operation batch for FileBaclend::doOperations()
1365          * @return array File operation batch
1366          */
1367         protected function resolveFSFileObjects( array $ops ) {
1368                 foreach ( $ops as &$op ) {
1369                         $src = isset( $op['src'] ) ? $op['src'] : null;
1370                         if ( $src instanceof FSFile ) {
1371                                 $op['srcRef'] = $src;
1372                                 $op['src'] = $src->getPath();
1373                         }
1374                 }
1375                 unset( $op );
1376
1377                 return $ops;
1378         }
1379
1380         /**
1381          * Check if a given path is a "mwstore://" path.
1382          * This does not do any further validation or any existence checks.
1383          *
1384          * @param string $path
1385          * @return bool
1386          */
1387         final public static function isStoragePath( $path ) {
1388                 return ( strpos( $path, 'mwstore://' ) === 0 );
1389         }
1390
1391         /**
1392          * Split a storage path into a backend name, a container name,
1393          * and a relative file path. The relative path may be the empty string.
1394          * This does not do any path normalization or traversal checks.
1395          *
1396          * @param string $storagePath
1397          * @return array (backend, container, rel object) or (null, null, null)
1398          */
1399         final public static function splitStoragePath( $storagePath ) {
1400                 if ( self::isStoragePath( $storagePath ) ) {
1401                         // Remove the "mwstore://" prefix and split the path
1402                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
1403                         if ( count( $parts ) >= 2 && $parts[0] != '' && $parts[1] != '' ) {
1404                                 if ( count( $parts ) == 3 ) {
1405                                         return $parts; // e.g. "backend/container/path"
1406                                 } else {
1407                                         return [ $parts[0], $parts[1], '' ]; // e.g. "backend/container"
1408                                 }
1409                         }
1410                 }
1411
1412                 return [ null, null, null ];
1413         }
1414
1415         /**
1416          * Normalize a storage path by cleaning up directory separators.
1417          * Returns null if the path is not of the format of a valid storage path.
1418          *
1419          * @param string $storagePath
1420          * @return string|null
1421          */
1422         final public static function normalizeStoragePath( $storagePath ) {
1423                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
1424                 if ( $relPath !== null ) { // must be for this backend
1425                         $relPath = self::normalizeContainerPath( $relPath );
1426                         if ( $relPath !== null ) {
1427                                 return ( $relPath != '' )
1428                                         ? "mwstore://{$backend}/{$container}/{$relPath}"
1429                                         : "mwstore://{$backend}/{$container}";
1430                         }
1431                 }
1432
1433                 return null;
1434         }
1435
1436         /**
1437          * Get the parent storage directory of a storage path.
1438          * This returns a path like "mwstore://backend/container",
1439          * "mwstore://backend/container/...", or null if there is no parent.
1440          *
1441          * @param string $storagePath
1442          * @return string|null
1443          */
1444         final public static function parentStoragePath( $storagePath ) {
1445                 $storagePath = dirname( $storagePath );
1446                 list( , , $rel ) = self::splitStoragePath( $storagePath );
1447
1448                 return ( $rel === null ) ? null : $storagePath;
1449         }
1450
1451         /**
1452          * Get the final extension from a storage or FS path
1453          *
1454          * @param string $path
1455          * @param string $case One of (rawcase, uppercase, lowercase) (since 1.24)
1456          * @return string
1457          */
1458         final public static function extensionFromPath( $path, $case = 'lowercase' ) {
1459                 $i = strrpos( $path, '.' );
1460                 $ext = $i ? substr( $path, $i + 1 ) : '';
1461
1462                 if ( $case === 'lowercase' ) {
1463                         $ext = strtolower( $ext );
1464                 } elseif ( $case === 'uppercase' ) {
1465                         $ext = strtoupper( $ext );
1466                 }
1467
1468                 return $ext;
1469         }
1470
1471         /**
1472          * Check if a relative path has no directory traversals
1473          *
1474          * @param string $path
1475          * @return bool
1476          * @since 1.20
1477          */
1478         final public static function isPathTraversalFree( $path ) {
1479                 return ( self::normalizeContainerPath( $path ) !== null );
1480         }
1481
1482         /**
1483          * Build a Content-Disposition header value per RFC 6266.
1484          *
1485          * @param string $type One of (attachment, inline)
1486          * @param string $filename Suggested file name (should not contain slashes)
1487          * @throws FileBackendError
1488          * @return string
1489          * @since 1.20
1490          */
1491         final public static function makeContentDisposition( $type, $filename = '' ) {
1492                 $parts = [];
1493
1494                 $type = strtolower( $type );
1495                 if ( !in_array( $type, [ 'inline', 'attachment' ] ) ) {
1496                         throw new FileBackendError( "Invalid Content-Disposition type '$type'." );
1497                 }
1498                 $parts[] = $type;
1499
1500                 if ( strlen( $filename ) ) {
1501                         $parts[] = "filename*=UTF-8''" . rawurlencode( basename( $filename ) );
1502                 }
1503
1504                 return implode( ';', $parts );
1505         }
1506
1507         /**
1508          * Validate and normalize a relative storage path.
1509          * Null is returned if the path involves directory traversal.
1510          * Traversal is insecure for FS backends and broken for others.
1511          *
1512          * This uses the same traversal protection as Title::secureAndSplit().
1513          *
1514          * @param string $path Storage path relative to a container
1515          * @return string|null
1516          */
1517         final protected static function normalizeContainerPath( $path ) {
1518                 // Normalize directory separators
1519                 $path = strtr( $path, '\\', '/' );
1520                 // Collapse any consecutive directory separators
1521                 $path = preg_replace( '![/]{2,}!', '/', $path );
1522                 // Remove any leading directory separator
1523                 $path = ltrim( $path, '/' );
1524                 // Use the same traversal protection as Title::secureAndSplit()
1525                 if ( strpos( $path, '.' ) !== false ) {
1526                         if (
1527                                 $path === '.' ||
1528                                 $path === '..' ||
1529                                 strpos( $path, './' ) === 0 ||
1530                                 strpos( $path, '../' ) === 0 ||
1531                                 strpos( $path, '/./' ) !== false ||
1532                                 strpos( $path, '/../' ) !== false
1533                         ) {
1534                                 return null;
1535                         }
1536                 }
1537
1538                 return $path;
1539         }
1540
1541         /**
1542          * Yields the result of the status wrapper callback on either:
1543          *   - StatusValue::newGood() if this method is called without parameters
1544          *   - StatusValue::newFatal() with all parameters to this method if passed in
1545          *
1546          * @param ... string
1547          * @return StatusValue
1548          */
1549         final protected function newStatus() {
1550                 $args = func_get_args();
1551                 if ( count( $args ) ) {
1552                         $sv = call_user_func_array( [ 'StatusValue', 'newFatal' ], $args );
1553                 } else {
1554                         $sv = StatusValue::newGood();
1555                 }
1556
1557                 return $this->wrapStatus( $sv );
1558         }
1559
1560         /**
1561          * @param StatusValue $sv
1562          * @return StatusValue Modified status or StatusValue subclass
1563          */
1564         final protected function wrapStatus( StatusValue $sv ) {
1565                 return $this->statusWrapper ? call_user_func( $this->statusWrapper, $sv ) : $sv;
1566         }
1567 }
1568
1569 /**
1570  * Generic file backend exception for checked and unexpected (e.g. config) exceptions
1571  *
1572  * @ingroup FileBackend
1573  * @since 1.23
1574  */
1575 class FileBackendException extends Exception {
1576 }
1577
1578 /**
1579  * File backend exception for checked exceptions (e.g. I/O errors)
1580  *
1581  * @ingroup FileBackend
1582  * @since 1.22
1583  */
1584 class FileBackendError extends FileBackendException {
1585 }