includes/libs/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  */
  30 use Psr\Log\LoggerAwareInterface;
  31 use Psr\Log\LoggerInterface;
  32 use Wikimedia\ScopedCallback;
  33 use Psr\Log\NullLogger;
  34
  35 /**
  36  * @brief Base class for all file backend classes (including multi-write backends).
  37  *
  38  * This class defines the methods as abstract that subclasses must implement.
  39  * Outside callers can assume that all backends will have these functions.
  40  *
  41  * All "storage paths" are of the format "mwstore://<backend>/<container>/<path>".
  42  * The "backend" portion is unique name for the application to refer to a backend, while
  43  * the "container" portion is a top-level directory of the backend. The "path" portion
  44  * is a relative path that uses UNIX file system (FS) notation, though any particular
  45  * backend may not actually be using a local filesystem. Therefore, the relative paths
  46  * are only virtual.
  47  *
  48  * Backend contents are stored under "domain"-specific container names by default.
  49  * A domain is simply a logical umbrella for entities, such as those belonging to a certain
  50  * application or portion of a website, for example. A domain can be local or global.
  51  * Global (qualified) backends are achieved by configuring the "domain ID" to a constant.
  52  * Global domains are simpler, but local domains can be used by choosing a domain ID based on
  53  * the current context, such as which language of a website is being used.
  54  *
  55  * For legacy reasons, the FSFileBackend class allows manually setting the paths of
  56  * containers to ones that do not respect the "domain ID".
  57  *
  58  * In key/value (object) stores, containers are the only hierarchy (the rest is emulated).
  59  * FS-based backends are somewhat more restrictive due to the existence of real
  60  * directory files; a regular file cannot have the same name as a directory. Other
  61  * backends with virtual directories may not have this limitation. Callers should
  62  * store files in such a way that no files and directories are under the same path.
  63  *
  64  * In general, this class allows for callers to access storage through the same
  65  * interface, without regard to the underlying storage system. However, calling code
  66  * must follow certain patterns and be aware of certain things to ensure compatibility:
  67  *   - a) Always call prepare() on the parent directory before trying to put a file there;
  68  *        key/value stores only need the container to exist first, but filesystems need
  69  *        all the parent directories to exist first (prepare() is aware of all this)
  70  *   - b) Always call clean() on a directory when it might become empty to avoid empty
  71  *        directory buildup on filesystems; key/value stores never have empty directories,
  72  *        so doing this helps preserve consistency in both cases
  73  *   - c) Likewise, do not rely on the existence of empty directories for anything;
  74  *        calling directoryExists() on a path that prepare() was previously called on
  75  *        will return false for key/value stores if there are no files under that path
  76  *   - d) Never alter the resulting FSFile returned from getLocalReference(), as it could
  77  *        either be a copy of the source file in /tmp or the original source file itself
  78  *   - e) Use a file layout that results in never attempting to store files over directories
  79  *        or directories over files; key/value stores allow this but filesystems do not
  80  *   - f) Use ASCII file names (e.g. base32, IDs, hashes) to avoid Unicode issues in Windows
  81  *   - g) Do not assume that move operations are atomic (difficult with key/value stores)
  82  *   - h) Do not assume that file stat or read operations always have immediate consistency;
  83  *        various methods have a "latest" flag that should always be used if up-to-date
  84  *        information is required (this trades performance for correctness as needed)
  85  *   - i) Do not assume that directory listings have immediate consistency
  86  *
  87  * Methods of subclasses should avoid throwing exceptions at all costs.
  88  * As a corollary, external dependencies should be kept to a minimum.
  89  *
  90  * @ingroup FileBackend
  91  * @since 1.19
  92  */
  93 abstract class FileBackend implements LoggerAwareInterface {
  94         /** @var string Unique backend name */
  95         protected $name;
  96
  97         /** @var string Unique domain name */
  98         protected $domainId;
  99
 100         /** @var string Read-only explanation message */
 101         protected $readOnly;
 102
 103         /** @var string When to do operations in parallel */
 104         protected $parallelize;
 105
 106         /** @var int How many operations can be done in parallel */
 107         protected $concurrency;
 108
 109         /** @var string Temporary file directory */
 110         protected $tmpDirectory;
 111
 112         /** @var LockManager */
 113         protected $lockManager;
 114         /** @var FileJournal */
 115         protected $fileJournal;
 116         /** @var LoggerInterface */
 117         protected $logger;
 118         /** @var callable|null */
 119         protected $profiler;
 120
 121         /** @var callable */
 122         protected $obResetFunc;
 123         /** @var callable */
 124         protected $streamMimeFunc;
 125         /** @var callable */
 126         protected $statusWrapper;
 127
 128         /** Bitfield flags for supported features */
 129         const ATTR_HEADERS = 1; // files can be tagged with standard HTTP headers
 130         const ATTR_METADATA = 2; // files can be stored with metadata key/values
 131         const ATTR_UNICODE_PATHS = 4; // files can have Unicode paths (not just ASCII)
 132
 133         /**
 134          * Create a new backend instance from configuration.
 135          * This should only be called from within FileBackendGroup.
 136          *
 137          * @param array $config Parameters include:
 138          *   - name : The unique name of this backend.
 139          *      This should consist of alphanumberic, '-', and '_' characters.
 140          *      This name should not be changed after use (e.g. with journaling).
 141          *      Note that the name is *not* used in actual container names.
 142          *   - domainId : Prefix to container names that is unique to this backend.
 143          *      It should only consist of alphanumberic, '-', and '_' characters.
 144          *      This ID is what avoids collisions if multiple logical backends
 145          *      use the same storage system, so this should be set carefully.
 146          *   - lockManager : LockManager object to use for any file locking.
 147          *      If not provided, then no file locking will be enforced.
 148          *   - fileJournal : FileJournal object to use for logging changes to files.
 149          *      If not provided, then change journaling will be disabled.
 150          *   - readOnly : Write operations are disallowed if this is a non-empty string.
 151          *      It should be an explanation for the backend being read-only.
 152          *   - parallelize : When to do file operations in parallel (when possible).
 153          *      Allowed values are "implicit", "explicit" and "off".
 154          *   - concurrency : How many file operations can be done in parallel.
 155          *   - tmpDirectory : Directory to use for temporary files. If this is not set or null,
 156          *      then the backend will try to discover a usable temporary directory.
 157          *   - obResetFunc : alternative callback to clear the output buffer
 158          *   - streamMimeFunc : alternative method to determine the content type from the path
 159          *   - logger : Optional PSR logger object.
 160          *   - profiler : Optional callback that takes a section name argument and returns
 161          *      a ScopedCallback instance that ends the profile section in its destructor.
 162          * @throws InvalidArgumentException
 163          */
 164         public function __construct( array $config ) {
 165                 $this->name = $config['name'];
 166                 $this->domainId = $config['domainId'] // e.g. "my_wiki-en_"
 167                         ?? $config['wikiId']; // b/c alias
 168                 if ( !preg_match( '!^[a-zA-Z0-9-_]{1,255}$!', $this->name ) ) {
 169                         throw new InvalidArgumentException( "Backend name '{$this->name}' is invalid." );
 170                 } elseif ( !is_string( $this->domainId ) ) {
 171                         throw new InvalidArgumentException(
 172                                 "Backend domain ID not provided for '{$this->name}'." );
 173                 }
 174                 $this->lockManager = $config['lockManager'] ?? new NullLockManager( [] );
 175                 $this->fileJournal = $config['fileJournal']
 176                         ?? FileJournal::factory( [ 'class' => NullFileJournal::class ], $this->name );
 177                 $this->readOnly = isset( $config['readOnly'] )
 178                         ? (string)$config['readOnly']
 179                         : '';
 180                 $this->parallelize = isset( $config['parallelize'] )
 181                         ? (string)$config['parallelize']
 182                         : 'off';
 183                 $this->concurrency = isset( $config['concurrency'] )
 184                         ? (int)$config['concurrency']
 185                         : 50;
 186                 $this->obResetFunc = $config['obResetFunc'] ?? [ $this, 'resetOutputBuffer' ];
 187                 $this->streamMimeFunc = $config['streamMimeFunc'] ?? null;
 188                 $this->statusWrapper = $config['statusWrapper'] ?? null;
 189
 190                 $this->profiler = $config['profiler'] ?? null;
 191                 if ( !is_callable( $this->profiler ) ) {
 192                         $this->profiler = null;
 193                 }
 194                 $this->logger = $config['logger'] ?? new NullLogger();
 195                 $this->statusWrapper = $config['statusWrapper'] ?? null;
 196                 $this->tmpDirectory = $config['tmpDirectory'] ?? null;
 197         }
 198
 199         public function setLogger( LoggerInterface $logger ) {
 200                 $this->logger = $logger;
 201         }
 202
 203         /**
 204          * Get the unique backend name.
 205          * We may have multiple different backends of the same type.
 206          * For example, we can have two Swift backends using different proxies.
 207          *
 208          * @return string
 209          */
 210         final public function getName() {
 211                 return $this->name;
 212         }
 213
 214         /**
 215          * Get the domain identifier used for this backend (possibly empty).
 216          *
 217          * @return string
 218          * @since 1.28
 219          */
 220         final public function getDomainId() {
 221                 return $this->domainId;
 222         }
 223
 224         /**
 225          * Alias to getDomainId()
 226          * @return string
 227          * @since 1.20
 228          */
 229         final public function getWikiId() {
 230                 return $this->getDomainId();
 231         }
 232
 233         /**
 234          * Check if this backend is read-only
 235          *
 236          * @return bool
 237          */
 238         final public function isReadOnly() {
 239                 return ( $this->readOnly != '' );
 240         }
 241
 242         /**
 243          * Get an explanatory message if this backend is read-only
 244          *
 245          * @return string|bool Returns false if the backend is not read-only
 246          */
 247         final public function getReadOnlyReason() {
 248                 return ( $this->readOnly != '' ) ? $this->readOnly : false;
 249         }
 250
 251         /**
 252          * Get the a bitfield of extra features supported by the backend medium
 253          *
 254          * @return int Bitfield of FileBackend::ATTR_* flags
 255          * @since 1.23
 256          */
 257         public function getFeatures() {
 258                 return self::ATTR_UNICODE_PATHS;
 259         }
 260
 261         /**
 262          * Check if the backend medium supports a field of extra features
 263          *
 264          * @param int $bitfield Bitfield of FileBackend::ATTR_* flags
 265          * @return bool
 266          * @since 1.23
 267          */
 268         final public function hasFeatures( $bitfield ) {
 269                 return ( $this->getFeatures() & $bitfield ) === $bitfield;
 270         }
 271
 272         /**
 273          * This is the main entry point into the backend for write operations.
 274          * Callers supply an ordered list of operations to perform as a transaction.
 275          * Files will be locked, the stat cache cleared, and then the operations attempted.
 276          * If any serious errors occur, all attempted operations will be rolled back.
 277          *
 278          * $ops is an array of arrays. The outer array holds a list of operations.
 279          * Each inner array is a set of key value pairs that specify an operation.
 280          *
 281          * Supported operations and their parameters. The supported actions are:
 282          *  - create
 283          *  - store
 284          *  - copy
 285          *  - move
 286          *  - delete
 287          *  - describe (since 1.21)
 288          *  - null
 289          *
 290          * FSFile/TempFSFile object support was added in 1.27.
 291          *
 292          * a) Create a new file in storage with the contents of a string
 293          * @code
 294          *     [
 295          *         'op'                  => 'create',
 296          *         'dst'                 => <storage path>,
 297          *         'content'             => <string of new file contents>,
 298          *         'overwrite'           => <boolean>,
 299          *         'overwriteSame'       => <boolean>,
 300          *         'headers'             => <HTTP header name/value map> # since 1.21
 301          *     ]
 302          * @endcode
 303          *
 304          * b) Copy a file system file into storage
 305          * @code
 306          *     [
 307          *         'op'                  => 'store',
 308          *         'src'                 => <file system path, FSFile, or TempFSFile>,
 309          *         'dst'                 => <storage path>,
 310          *         'overwrite'           => <boolean>,
 311          *         'overwriteSame'       => <boolean>,
 312          *         'headers'             => <HTTP header name/value map> # since 1.21
 313          *     ]
 314          * @endcode
 315          *
 316          * c) Copy a file within storage
 317          * @code
 318          *     [
 319          *         'op'                  => 'copy',
 320          *         'src'                 => <storage path>,
 321          *         'dst'                 => <storage path>,
 322          *         'overwrite'           => <boolean>,
 323          *         'overwriteSame'       => <boolean>,
 324          *         'ignoreMissingSource' => <boolean>, # since 1.21
 325          *         'headers'             => <HTTP header name/value map> # since 1.21
 326          *     ]
 327          * @endcode
 328          *
 329          * d) Move a file within storage
 330          * @code
 331          *     [
 332          *         'op'                  => 'move',
 333          *         'src'                 => <storage path>,
 334          *         'dst'                 => <storage path>,
 335          *         'overwrite'           => <boolean>,
 336          *         'overwriteSame'       => <boolean>,
 337          *         'ignoreMissingSource' => <boolean>, # since 1.21
 338          *         'headers'             => <HTTP header name/value map> # since 1.21
 339          *     ]
 340          * @endcode
 341          *
 342          * e) Delete a file within storage
 343          * @code
 344          *     [
 345          *         'op'                  => 'delete',
 346          *         'src'                 => <storage path>,
 347          *         'ignoreMissingSource' => <boolean>
 348          *     ]
 349          * @endcode
 350          *
 351          * f) Update metadata for a file within storage
 352          * @code
 353          *     [
 354          *         'op'                  => 'describe',
 355          *         'src'                 => <storage path>,
 356          *         'headers'             => <HTTP header name/value map>
 357          *     ]
 358          * @endcode
 359          *
 360          * g) Do nothing (no-op)
 361          * @code
 362          *     [
 363          *         'op'                  => 'null',
 364          *     ]
 365          * @endcode
 366          *
 367          * Boolean flags for operations (operation-specific):
 368          *   - ignoreMissingSource : The operation will simply succeed and do
 369          *                           nothing if the source file does not exist.
 370          *   - overwrite           : Any destination file will be overwritten.
 371          *   - overwriteSame       : If a file already exists at the destination with the
 372          *                           same contents, then do nothing to the destination file
 373          *                           instead of giving an error. This does not compare headers.
 374          *                           This option is ignored if 'overwrite' is already provided.
 375          *   - headers             : If supplied, the result of merging these headers with any
 376          *                           existing source file headers (replacing conflicting ones)
 377          *                           will be set as the destination file headers. Headers are
 378          *                           deleted if their value is set to the empty string. When a
 379          *                           file has headers they are included in responses to GET and
 380          *                           HEAD requests to the backing store for that file.
 381          *                           Header values should be no larger than 255 bytes, except for
 382          *                           Content-Disposition. The system might ignore or truncate any
 383          *                           headers that are too long to store (exact limits will vary).
 384          *                           Backends that don't support metadata ignore this. (since 1.21)
 385          *
 386          * $opts is an associative of boolean flags, including:
 387          *   - force               : Operation precondition errors no longer trigger an abort.
 388          *                           Any remaining operations are still attempted. Unexpected
 389          *                           failures may still cause remaining operations to be aborted.
 390          *   - nonLocking          : No locks are acquired for the operations.
 391          *                           This can increase performance for non-critical writes.
 392          *                           This has no effect unless the 'force' flag is set.
 393          *   - nonJournaled        : Don't log this operation batch in the file journal.
 394          *                           This limits the ability of recovery scripts.
 395          *   - parallelize         : Try to do operations in parallel when possible.
 396          *   - bypassReadOnly      : Allow writes in read-only mode. (since 1.20)
 397          *   - preserveCache       : Don't clear the process cache before checking files.
 398          *                           This should only be used if all entries in the process
 399          *                           cache were added after the files were already locked. (since 1.20)
 400          *
 401          * @note Remarks on locking:
 402          * File system paths given to operations should refer to files that are
 403          * already locked or otherwise safe from modification from other processes.
 404          * Normally these files will be new temp files, which should be adequate.
 405          *
 406          * @par Return value:
 407          *
 408          * This returns a Status, which contains all warnings and fatals that occurred
 409          * during the operation. The 'failCount', 'successCount', and 'success' members
 410          * will reflect each operation attempted.
 411          *
 412          * The StatusValue will be "OK" unless:
 413          *   - a) unexpected operation errors occurred (network partitions, disk full...)
 414          *   - b) significant operation errors occurred and 'force' was not set
 415          *
 416          * @param array $ops List of operations to execute in order
 417          * @param array $opts Batch operation options
 418          * @return StatusValue
 419          */
 420         final public function doOperations( array $ops, array $opts = [] ) {
 421                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 422                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 423                 }
 424                 if ( $ops === [] ) {
 425                         return $this->newStatus(); // nothing to do
 426                 }
 427
 428                 $ops = $this->resolveFSFileObjects( $ops );
 429                 if ( empty( $opts['force'] ) ) { // sanity
 430                         unset( $opts['nonLocking'] );
 431                 }
 432
 433                 /** @noinspection PhpUnusedLocalVariableInspection */
 434                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 435
 436                 return $this->doOperationsInternal( $ops, $opts );
 437         }
 438
 439         /**
 440          * @see FileBackend::doOperations()
 441          * @param array $ops
 442          * @param array $opts
 443          * @return StatusValue
 444          */
 445         abstract protected function doOperationsInternal( array $ops, array $opts );
 446
 447         /**
 448          * Same as doOperations() except it takes a single operation.
 449          * If you are doing a batch of operations that should either
 450          * all succeed or all fail, then use that function instead.
 451          *
 452          * @see FileBackend::doOperations()
 453          *
 454          * @param array $op Operation
 455          * @param array $opts Operation options
 456          * @return StatusValue
 457          */
 458         final public function doOperation( array $op, array $opts = [] ) {
 459                 return $this->doOperations( [ $op ], $opts );
 460         }
 461
 462         /**
 463          * Performs a single create operation.
 464          * This sets $params['op'] to 'create' and passes it to doOperation().
 465          *
 466          * @see FileBackend::doOperation()
 467          *
 468          * @param array $params Operation parameters
 469          * @param array $opts Operation options
 470          * @return StatusValue
 471          */
 472         final public function create( array $params, array $opts = [] ) {
 473                 return $this->doOperation( [ 'op' => 'create' ] + $params, $opts );
 474         }
 475
 476         /**
 477          * Performs a single store operation.
 478          * This sets $params['op'] to 'store' and passes it to doOperation().
 479          *
 480          * @see FileBackend::doOperation()
 481          *
 482          * @param array $params Operation parameters
 483          * @param array $opts Operation options
 484          * @return StatusValue
 485          */
 486         final public function store( array $params, array $opts = [] ) {
 487                 return $this->doOperation( [ 'op' => 'store' ] + $params, $opts );
 488         }
 489
 490         /**
 491          * Performs a single copy operation.
 492          * This sets $params['op'] to 'copy' and passes it to doOperation().
 493          *
 494          * @see FileBackend::doOperation()
 495          *
 496          * @param array $params Operation parameters
 497          * @param array $opts Operation options
 498          * @return StatusValue
 499          */
 500         final public function copy( array $params, array $opts = [] ) {
 501                 return $this->doOperation( [ 'op' => 'copy' ] + $params, $opts );
 502         }
 503
 504         /**
 505          * Performs a single move operation.
 506          * This sets $params['op'] to 'move' and passes it to doOperation().
 507          *
 508          * @see FileBackend::doOperation()
 509          *
 510          * @param array $params Operation parameters
 511          * @param array $opts Operation options
 512          * @return StatusValue
 513          */
 514         final public function move( array $params, array $opts = [] ) {
 515                 return $this->doOperation( [ 'op' => 'move' ] + $params, $opts );
 516         }
 517
 518         /**
 519          * Performs a single delete operation.
 520          * This sets $params['op'] to 'delete' and passes it to doOperation().
 521          *
 522          * @see FileBackend::doOperation()
 523          *
 524          * @param array $params Operation parameters
 525          * @param array $opts Operation options
 526          * @return StatusValue
 527          */
 528         final public function delete( array $params, array $opts = [] ) {
 529                 return $this->doOperation( [ 'op' => 'delete' ] + $params, $opts );
 530         }
 531
 532         /**
 533          * Performs a single describe operation.
 534          * This sets $params['op'] to 'describe' and passes it to doOperation().
 535          *
 536          * @see FileBackend::doOperation()
 537          *
 538          * @param array $params Operation parameters
 539          * @param array $opts Operation options
 540          * @return StatusValue
 541          * @since 1.21
 542          */
 543         final public function describe( array $params, array $opts = [] ) {
 544                 return $this->doOperation( [ 'op' => 'describe' ] + $params, $opts );
 545         }
 546
 547         /**
 548          * Perform a set of independent file operations on some files.
 549          *
 550          * This does no locking, nor journaling, and possibly no stat calls.
 551          * Any destination files that already exist will be overwritten.
 552          * This should *only* be used on non-original files, like cache files.
 553          *
 554          * Supported operations and their parameters:
 555          *  - create
 556          *  - store
 557          *  - copy
 558          *  - move
 559          *  - delete
 560          *  - describe (since 1.21)
 561          *  - null
 562          *
 563          * FSFile/TempFSFile object support was added in 1.27.
 564          *
 565          * a) Create a new file in storage with the contents of a string
 566          * @code
 567          *     [
 568          *         'op'                  => 'create',
 569          *         'dst'                 => <storage path>,
 570          *         'content'             => <string of new file contents>,
 571          *         'headers'             => <HTTP header name/value map> # since 1.21
 572          *     ]
 573          * @endcode
 574          *
 575          * b) Copy a file system file into storage
 576          * @code
 577          *     [
 578          *         'op'                  => 'store',
 579          *         'src'                 => <file system path, FSFile, or TempFSFile>,
 580          *         'dst'                 => <storage path>,
 581          *         'headers'             => <HTTP header name/value map> # since 1.21
 582          *     ]
 583          * @endcode
 584          *
 585          * c) Copy a file within storage
 586          * @code
 587          *     [
 588          *         'op'                  => 'copy',
 589          *         'src'                 => <storage path>,
 590          *         'dst'                 => <storage path>,
 591          *         'ignoreMissingSource' => <boolean>, # since 1.21
 592          *         'headers'             => <HTTP header name/value map> # since 1.21
 593          *     ]
 594          * @endcode
 595          *
 596          * d) Move a file within storage
 597          * @code
 598          *     [
 599          *         'op'                  => 'move',
 600          *         'src'                 => <storage path>,
 601          *         'dst'                 => <storage path>,
 602          *         'ignoreMissingSource' => <boolean>, # since 1.21
 603          *         'headers'             => <HTTP header name/value map> # since 1.21
 604          *     ]
 605          * @endcode
 606          *
 607          * e) Delete a file within storage
 608          * @code
 609          *     [
 610          *         'op'                  => 'delete',
 611          *         'src'                 => <storage path>,
 612          *         'ignoreMissingSource' => <boolean>
 613          *     ]
 614          * @endcode
 615          *
 616          * f) Update metadata for a file within storage
 617          * @code
 618          *     [
 619          *         'op'                  => 'describe',
 620          *         'src'                 => <storage path>,
 621          *         'headers'             => <HTTP header name/value map>
 622          *     ]
 623          * @endcode
 624          *
 625          * g) Do nothing (no-op)
 626          * @code
 627          *     [
 628          *         'op'                  => 'null',
 629          *     ]
 630          * @endcode
 631          *
 632          * @par Boolean flags for operations (operation-specific):
 633          *   - ignoreMissingSource : The operation will simply succeed and do
 634          *                           nothing if the source file does not exist.
 635          *   - headers             : If supplied with a header name/value map, the backend will
 636          *                           reply with these headers when GETs/HEADs of the destination
 637          *                           file are made. Header values should be smaller than 256 bytes.
 638          *                           Content-Disposition headers can be longer, though the system
 639          *                           might ignore or truncate ones that are too long to store.
 640          *                           Existing headers will remain, but these will replace any
 641          *                           conflicting previous headers, and headers will be removed
 642          *                           if they are set to an empty string.
 643          *                           Backends that don't support metadata ignore this. (since 1.21)
 644          *
 645          * $opts is an associative of boolean flags, including:
 646          *   - bypassReadOnly      : Allow writes in read-only mode (since 1.20)
 647          *
 648          * @par Return value:
 649          * This returns a Status, which contains all warnings and fatals that occurred
 650          * during the operation. The 'failCount', 'successCount', and 'success' members
 651          * will reflect each operation attempted for the given files. The StatusValue will be
 652          * considered "OK" as long as no fatal errors occurred.
 653          *
 654          * @param array $ops Set of operations to execute
 655          * @param array $opts Batch operation options
 656          * @return StatusValue
 657          * @since 1.20
 658          */
 659         final public function doQuickOperations( array $ops, array $opts = [] ) {
 660                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 661                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 662                 }
 663                 if ( $ops === [] ) {
 664                         return $this->newStatus(); // nothing to do
 665                 }
 666
 667                 $ops = $this->resolveFSFileObjects( $ops );
 668                 foreach ( $ops as &$op ) {
 669                         $op['overwrite'] = true; // avoids RTTs in key/value stores
 670                 }
 671
 672                 /** @noinspection PhpUnusedLocalVariableInspection */
 673                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 674
 675                 return $this->doQuickOperationsInternal( $ops );
 676         }
 677
 678         /**
 679          * @see FileBackend::doQuickOperations()
 680          * @param array $ops
 681          * @return StatusValue
 682          * @since 1.20
 683          */
 684         abstract protected function doQuickOperationsInternal( array $ops );
 685
 686         /**
 687          * Same as doQuickOperations() except it takes a single operation.
 688          * If you are doing a batch of operations, then use that function instead.
 689          *
 690          * @see FileBackend::doQuickOperations()
 691          *
 692          * @param array $op Operation
 693          * @return StatusValue
 694          * @since 1.20
 695          */
 696         final public function doQuickOperation( array $op ) {
 697                 return $this->doQuickOperations( [ $op ] );
 698         }
 699
 700         /**
 701          * Performs a single quick create operation.
 702          * This sets $params['op'] to 'create' and passes it to doQuickOperation().
 703          *
 704          * @see FileBackend::doQuickOperation()
 705          *
 706          * @param array $params Operation parameters
 707          * @return StatusValue
 708          * @since 1.20
 709          */
 710         final public function quickCreate( array $params ) {
 711                 return $this->doQuickOperation( [ 'op' => 'create' ] + $params );
 712         }
 713
 714         /**
 715          * Performs a single quick store operation.
 716          * This sets $params['op'] to 'store' and passes it to doQuickOperation().
 717          *
 718          * @see FileBackend::doQuickOperation()
 719          *
 720          * @param array $params Operation parameters
 721          * @return StatusValue
 722          * @since 1.20
 723          */
 724         final public function quickStore( array $params ) {
 725                 return $this->doQuickOperation( [ 'op' => 'store' ] + $params );
 726         }
 727
 728         /**
 729          * Performs a single quick copy operation.
 730          * This sets $params['op'] to 'copy' and passes it to doQuickOperation().
 731          *
 732          * @see FileBackend::doQuickOperation()
 733          *
 734          * @param array $params Operation parameters
 735          * @return StatusValue
 736          * @since 1.20
 737          */
 738         final public function quickCopy( array $params ) {
 739                 return $this->doQuickOperation( [ 'op' => 'copy' ] + $params );
 740         }
 741
 742         /**
 743          * Performs a single quick move operation.
 744          * This sets $params['op'] to 'move' and passes it to doQuickOperation().
 745          *
 746          * @see FileBackend::doQuickOperation()
 747          *
 748          * @param array $params Operation parameters
 749          * @return StatusValue
 750          * @since 1.20
 751          */
 752         final public function quickMove( array $params ) {
 753                 return $this->doQuickOperation( [ 'op' => 'move' ] + $params );
 754         }
 755
 756         /**
 757          * Performs a single quick delete operation.
 758          * This sets $params['op'] to 'delete' and passes it to doQuickOperation().
 759          *
 760          * @see FileBackend::doQuickOperation()
 761          *
 762          * @param array $params Operation parameters
 763          * @return StatusValue
 764          * @since 1.20
 765          */
 766         final public function quickDelete( array $params ) {
 767                 return $this->doQuickOperation( [ 'op' => 'delete' ] + $params );
 768         }
 769
 770         /**
 771          * Performs a single quick describe operation.
 772          * This sets $params['op'] to 'describe' and passes it to doQuickOperation().
 773          *
 774          * @see FileBackend::doQuickOperation()
 775          *
 776          * @param array $params Operation parameters
 777          * @return StatusValue
 778          * @since 1.21
 779          */
 780         final public function quickDescribe( array $params ) {
 781                 return $this->doQuickOperation( [ 'op' => 'describe' ] + $params );
 782         }
 783
 784         /**
 785          * Concatenate a list of storage files into a single file system file.
 786          * The target path should refer to a file that is already locked or
 787          * otherwise safe from modification from other processes. Normally,
 788          * the file will be a new temp file, which should be adequate.
 789          *
 790          * @param array $params Operation parameters, include:
 791          *   - srcs        : ordered source storage paths (e.g. chunk1, chunk2, ...)
 792          *   - dst         : file system path to 0-byte temp file
 793          *   - parallelize : try to do operations in parallel when possible
 794          * @return StatusValue
 795          */
 796         abstract public function concatenate( array $params );
 797
 798         /**
 799          * Prepare a storage directory for usage.
 800          * This will create any required containers and parent directories.
 801          * Backends using key/value stores only need to create the container.
 802          *
 803          * The 'noAccess' and 'noListing' parameters works the same as in secure(),
 804          * except they are only applied *if* the directory/container had to be created.
 805          * These flags should always be set for directories that have private files.
 806          * However, setting them is not guaranteed to actually do anything.
 807          * Additional server configuration may be needed to achieve the desired effect.
 808          *
 809          * @param array $params Parameters include:
 810          *   - dir            : storage directory
 811          *   - noAccess       : try to deny file access (since 1.20)
 812          *   - noListing      : try to deny file listing (since 1.20)
 813          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 814          * @return StatusValue
 815          */
 816         final public function prepare( array $params ) {
 817                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 818                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 819                 }
 820                 /** @noinspection PhpUnusedLocalVariableInspection */
 821                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 822                 return $this->doPrepare( $params );
 823         }
 824
 825         /**
 826          * @see FileBackend::prepare()
 827          * @param array $params
 828          * @return StatusValue
 829          */
 830         abstract protected function doPrepare( array $params );
 831
 832         /**
 833          * Take measures to block web access to a storage directory and
 834          * the container it belongs to. FS backends might add .htaccess
 835          * files whereas key/value store backends might revoke container
 836          * access to the storage user representing end-users in web requests.
 837          *
 838          * This is not guaranteed to actually make files or listings publicly hidden.
 839          * Additional server configuration may be needed to achieve the desired effect.
 840          *
 841          * @param array $params Parameters include:
 842          *   - dir            : storage directory
 843          *   - noAccess       : try to deny file access
 844          *   - noListing      : try to deny file listing
 845          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 846          * @return StatusValue
 847          */
 848         final public function secure( array $params ) {
 849                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 850                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 851                 }
 852                 /** @noinspection PhpUnusedLocalVariableInspection */
 853                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 854                 return $this->doSecure( $params );
 855         }
 856
 857         /**
 858          * @see FileBackend::secure()
 859          * @param array $params
 860          * @return StatusValue
 861          */
 862         abstract protected function doSecure( array $params );
 863
 864         /**
 865          * Remove measures to block web access to a storage directory and
 866          * the container it belongs to. FS backends might remove .htaccess
 867          * files whereas key/value store backends might grant container
 868          * access to the storage user representing end-users in web requests.
 869          * This essentially can undo the result of secure() calls.
 870          *
 871          * This is not guaranteed to actually make files or listings publicly viewable.
 872          * Additional server configuration may be needed to achieve the desired effect.
 873          *
 874          * @param array $params Parameters include:
 875          *   - dir            : storage directory
 876          *   - access         : try to allow file access
 877          *   - listing        : try to allow file listing
 878          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 879          * @return StatusValue
 880          * @since 1.20
 881          */
 882         final public function publish( array $params ) {
 883                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 884                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 885                 }
 886                 /** @noinspection PhpUnusedLocalVariableInspection */
 887                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 888                 return $this->doPublish( $params );
 889         }
 890
 891         /**
 892          * @see FileBackend::publish()
 893          * @param array $params
 894          * @return StatusValue
 895          */
 896         abstract protected function doPublish( array $params );
 897
 898         /**
 899          * Delete a storage directory if it is empty.
 900          * Backends using key/value stores may do nothing unless the directory
 901          * is that of an empty container, in which case it will be deleted.
 902          *
 903          * @param array $params Parameters include:
 904          *   - dir            : storage directory
 905          *   - recursive      : recursively delete empty subdirectories first (since 1.20)
 906          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 907          * @return StatusValue
 908          */
 909         final public function clean( array $params ) {
 910                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 911                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 912                 }
 913                 /** @noinspection PhpUnusedLocalVariableInspection */
 914                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 915                 return $this->doClean( $params );
 916         }
 917
 918         /**
 919          * @see FileBackend::clean()
 920          * @param array $params
 921          * @return StatusValue
 922          */
 923         abstract protected function doClean( array $params );
 924
 925         /**
 926          * Check if a file exists at a storage path in the backend.
 927          * This returns false if only a directory exists at the path.
 928          *
 929          * @param array $params Parameters include:
 930          *   - src    : source storage path
 931          *   - latest : use the latest available data
 932          * @return bool|null Returns null on failure
 933          */
 934         abstract public function fileExists( array $params );
 935
 936         /**
 937          * Get the last-modified timestamp of the file at a storage path.
 938          *
 939          * @param array $params Parameters include:
 940          *   - src    : source storage path
 941          *   - latest : use the latest available data
 942          * @return string|bool TS_MW timestamp or false on failure
 943          */
 944         abstract public function getFileTimestamp( array $params );
 945
 946         /**
 947          * Get the contents of a file at a storage path in the backend.
 948          * This should be avoided for potentially large files.
 949          *
 950          * @param array $params Parameters include:
 951          *   - src    : source storage path
 952          *   - latest : use the latest available data
 953          * @return string|bool Returns false on failure
 954          */
 955         final public function getFileContents( array $params ) {
 956                 $contents = $this->getFileContentsMulti(
 957                         [ 'srcs' => [ $params['src'] ] ] + $params );
 958
 959                 return $contents[$params['src']];
 960         }
 961
 962         /**
 963          * Like getFileContents() except it takes an array of storage paths
 964          * and returns a map of storage paths to strings (or null on failure).
 965          * The map keys (paths) are in the same order as the provided list of paths.
 966          *
 967          * @see FileBackend::getFileContents()
 968          *
 969          * @param array $params Parameters include:
 970          *   - srcs        : list of source storage paths
 971          *   - latest      : use the latest available data
 972          *   - parallelize : try to do operations in parallel when possible
 973          * @return array Map of (path name => string or false on failure)
 974          * @since 1.20
 975          */
 976         abstract public function getFileContentsMulti( array $params );
 977
 978         /**
 979          * Get metadata about a file at a storage path in the backend.
 980          * If the file does not exist, then this returns false.
 981          * Otherwise, the result is an associative array that includes:
 982          *   - headers  : map of HTTP headers used for GET/HEAD requests (name => value)
 983          *   - metadata : map of file metadata (name => value)
 984          * Metadata keys and headers names will be returned in all lower-case.
 985          * Additional values may be included for internal use only.
 986          *
 987          * Use FileBackend::hasFeatures() to check how well this is supported.
 988          *
 989          * @param array $params
 990          * $params include:
 991          *   - src    : source storage path
 992          *   - latest : use the latest available data
 993          * @return array|bool Returns false on failure
 994          * @since 1.23
 995          */
 996         abstract public function getFileXAttributes( array $params );
 997
 998         /**
 999          * Get the size (bytes) of a file at a storage path in the backend.
1000          *
1001          * @param array $params Parameters include:
1002          *   - src    : source storage path
1003          *   - latest : use the latest available data
1004          * @return int|bool Returns false on failure
1005          */
1006         abstract public function getFileSize( array $params );
1007
1008         /**
1009          * Get quick information about a file at a storage path in the backend.
1010          * If the file does not exist, then this returns false.
1011          * Otherwise, the result is an associative array that includes:
1012          *   - mtime  : the last-modified timestamp (TS_MW)
1013          *   - size   : the file size (bytes)
1014          * Additional values may be included for internal use only.
1015          *
1016          * @param array $params Parameters include:
1017          *   - src    : source storage path
1018          *   - latest : use the latest available data
1019          * @return array|bool|null Returns null on failure
1020          */
1021         abstract public function getFileStat( array $params );
1022
1023         /**
1024          * Get a SHA-1 hash of the file at a storage path in the backend.
1025          *
1026          * @param array $params Parameters include:
1027          *   - src    : source storage path
1028          *   - latest : use the latest available data
1029          * @return string|bool Hash string or false on failure
1030          */
1031         abstract public function getFileSha1Base36( array $params );
1032
1033         /**
1034          * Get the properties of the file at a storage path in the backend.
1035          * This gives the result of FSFile::getProps() on a local copy of the file.
1036          *
1037          * @param array $params Parameters include:
1038          *   - src    : source storage path
1039          *   - latest : use the latest available data
1040          * @return array Returns FSFile::placeholderProps() on failure
1041          */
1042         abstract public function getFileProps( array $params );
1043
1044         /**
1045          * Stream the file at a storage path in the backend.
1046          *
1047          * If the file does not exists, an HTTP 404 error will be given.
1048          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
1049          * will be sent if streaming began, while none will be sent otherwise.
1050          * Implementations should flush the output buffer before sending data.
1051          *
1052          * @param array $params Parameters include:
1053          *   - src      : source storage path
1054          *   - headers  : list of additional HTTP headers to send if the file exists
1055          *   - options  : HTTP request header map with lower case keys (since 1.28). Supports:
1056          *                range             : format is "bytes=(\d*-\d*)"
1057          *                if-modified-since : format is an HTTP date
1058          *   - headless : only include the body (and headers from "headers") (since 1.28)
1059          *   - latest   : use the latest available data
1060          *   - allowOB  : preserve any output buffers (since 1.28)
1061          * @return StatusValue
1062          */
1063         abstract public function streamFile( array $params );
1064
1065         /**
1066          * Returns a file system file, identical to the file at a storage path.
1067          * The file returned is either:
1068          *   - a) A local copy of the file at a storage path in the backend.
1069          *        The temporary copy will have the same extension as the source.
1070          *   - b) An original of the file at a storage path in the backend.
1071          * Temporary files may be purged when the file object falls out of scope.
1072          *
1073          * Write operations should *never* be done on this file as some backends
1074          * may do internal tracking or may be instances of FileBackendMultiWrite.
1075          * In that latter case, there are copies of the file that must stay in sync.
1076          * Additionally, further calls to this function may return the same file.
1077          *
1078          * @param array $params Parameters include:
1079          *   - src    : source storage path
1080          *   - latest : use the latest available data
1081          * @return FSFile|null Returns null on failure
1082          */
1083         final public function getLocalReference( array $params ) {
1084                 $fsFiles = $this->getLocalReferenceMulti(
1085                         [ 'srcs' => [ $params['src'] ] ] + $params );
1086
1087                 return $fsFiles[$params['src']];
1088         }
1089
1090         /**
1091          * Like getLocalReference() except it takes an array of storage paths
1092          * and returns a map of storage paths to FSFile 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::getLocalReference()
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 => FSFile or null on failure)
1102          * @since 1.20
1103          */
1104         abstract public function getLocalReferenceMulti( array $params );
1105
1106         /**
1107          * Get a local copy on disk of the file at a storage path in the backend.
1108          * The temporary copy will have the same file extension as the source.
1109          * Temporary files may be purged when the file object falls out of scope.
1110          *
1111          * @param array $params Parameters include:
1112          *   - src    : source storage path
1113          *   - latest : use the latest available data
1114          * @return TempFSFile|null Returns null on failure
1115          */
1116         final public function getLocalCopy( array $params ) {
1117                 $tmpFiles = $this->getLocalCopyMulti(
1118                         [ 'srcs' => [ $params['src'] ] ] + $params );
1119
1120                 return $tmpFiles[$params['src']];
1121         }
1122
1123         /**
1124          * Like getLocalCopy() except it takes an array of storage paths and
1125          * returns a map of storage paths to TempFSFile objects (or null on failure).
1126          * The map keys (paths) are in the same order as the provided list of paths.
1127          *
1128          * @see FileBackend::getLocalCopy()
1129          *
1130          * @param array $params Parameters include:
1131          *   - srcs        : list of source storage paths
1132          *   - latest      : use the latest available data
1133          *   - parallelize : try to do operations in parallel when possible
1134          * @return array Map of (path name => TempFSFile or null on failure)
1135          * @since 1.20
1136          */
1137         abstract public function getLocalCopyMulti( array $params );
1138
1139         /**
1140          * Return an HTTP URL to a given file that requires no authentication to use.
1141          * The URL may be pre-authenticated (via some token in the URL) and temporary.
1142          * This will return null if the backend cannot make an HTTP URL for the file.
1143          *
1144          * This is useful for key/value stores when using scripts that seek around
1145          * large files and those scripts (and the backend) support HTTP Range headers.
1146          * Otherwise, one would need to use getLocalReference(), which involves loading
1147          * the entire file on to local disk.
1148          *
1149          * @param array $params Parameters include:
1150          *   - src : source storage path
1151          *   - ttl : lifetime (seconds) if pre-authenticated; default is 1 day
1152          * @return string|null
1153          * @since 1.21
1154          */
1155         abstract public function getFileHttpUrl( array $params );
1156
1157         /**
1158          * Check if a directory exists at a given storage path.
1159          * Backends using key/value stores will check if the path is a
1160          * virtual directory, meaning there are files under the given directory.
1161          *
1162          * Storage backends with eventual consistency might return stale data.
1163          *
1164          * @param array $params Parameters include:
1165          *   - dir : storage directory
1166          * @return bool|null Returns null on failure
1167          * @since 1.20
1168          */
1169         abstract public function directoryExists( array $params );
1170
1171         /**
1172          * Get an iterator to list *all* directories under a storage directory.
1173          * If the directory is of the form "mwstore://backend/container",
1174          * then all directories in the container will be listed.
1175          * If the directory is of form "mwstore://backend/container/dir",
1176          * then all directories directly under that directory will be listed.
1177          * Results will be storage directories relative to the given directory.
1178          *
1179          * Storage backends with eventual consistency might return stale data.
1180          *
1181          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1182          *
1183          * @param array $params Parameters include:
1184          *   - dir     : storage directory
1185          *   - topOnly : only return direct child dirs of the directory
1186          * @return Traversable|array|null Returns null on failure
1187          * @since 1.20
1188          */
1189         abstract public function getDirectoryList( array $params );
1190
1191         /**
1192          * Same as FileBackend::getDirectoryList() except only lists
1193          * directories that are immediately under the given directory.
1194          *
1195          * Storage backends with eventual consistency might return stale data.
1196          *
1197          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1198          *
1199          * @param array $params Parameters include:
1200          *   - dir : storage directory
1201          * @return Traversable|array|null Returns null on failure
1202          * @since 1.20
1203          */
1204         final public function getTopDirectoryList( array $params ) {
1205                 return $this->getDirectoryList( [ 'topOnly' => true ] + $params );
1206         }
1207
1208         /**
1209          * Get an iterator to list *all* stored files under a storage directory.
1210          * If the directory is of the form "mwstore://backend/container",
1211          * then all files in the container will be listed.
1212          * If the directory is of form "mwstore://backend/container/dir",
1213          * then all files under that directory will be listed.
1214          * Results will be storage paths relative to the given directory.
1215          *
1216          * Storage backends with eventual consistency might return stale data.
1217          *
1218          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1219          *
1220          * @param array $params Parameters include:
1221          *   - dir        : storage directory
1222          *   - topOnly    : only return direct child files of the directory (since 1.20)
1223          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1224          * @return Traversable|array|null Returns null on failure
1225          */
1226         abstract public function getFileList( array $params );
1227
1228         /**
1229          * Same as FileBackend::getFileList() except only lists
1230          * files that are immediately under the given directory.
1231          *
1232          * Storage backends with eventual consistency might return stale data.
1233          *
1234          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1235          *
1236          * @param array $params Parameters include:
1237          *   - dir        : storage directory
1238          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1239          * @return Traversable|array|null Returns null on failure
1240          * @since 1.20
1241          */
1242         final public function getTopFileList( array $params ) {
1243                 return $this->getFileList( [ 'topOnly' => true ] + $params );
1244         }
1245
1246         /**
1247          * Preload persistent file stat cache and property cache into in-process cache.
1248          * This should be used when stat calls will be made on a known list of a many files.
1249          *
1250          * @see FileBackend::getFileStat()
1251          *
1252          * @param array $paths Storage paths
1253          */
1254         abstract public function preloadCache( array $paths );
1255
1256         /**
1257          * Invalidate any in-process file stat and property cache.
1258          * If $paths is given, then only the cache for those files will be cleared.
1259          *
1260          * @see FileBackend::getFileStat()
1261          *
1262          * @param array|null $paths Storage paths (optional)
1263          */
1264         abstract public function clearCache( array $paths = null );
1265
1266         /**
1267          * Preload file stat information (concurrently if possible) into in-process cache.
1268          *
1269          * This should be used when stat calls will be made on a known list of a many files.
1270          * This does not make use of the persistent file stat cache.
1271          *
1272          * @see FileBackend::getFileStat()
1273          *
1274          * @param array $params Parameters include:
1275          *   - srcs        : list of source storage paths
1276          *   - latest      : use the latest available data
1277          * @return bool All requests proceeded without I/O errors (since 1.24)
1278          * @since 1.23
1279          */
1280         abstract public function preloadFileStat( array $params );
1281
1282         /**
1283          * Lock the files at the given storage paths in the backend.
1284          * This will either lock all the files or none (on failure).
1285          *
1286          * Callers should consider using getScopedFileLocks() instead.
1287          *
1288          * @param array $paths Storage paths
1289          * @param int $type LockManager::LOCK_* constant
1290          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.24)
1291          * @return StatusValue
1292          */
1293         final public function lockFiles( array $paths, $type, $timeout = 0 ) {
1294                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1295
1296                 return $this->wrapStatus( $this->lockManager->lock( $paths, $type, $timeout ) );
1297         }
1298
1299         /**
1300          * Unlock the files at the given storage paths in the backend.
1301          *
1302          * @param array $paths Storage paths
1303          * @param int $type LockManager::LOCK_* constant
1304          * @return StatusValue
1305          */
1306         final public function unlockFiles( array $paths, $type ) {
1307                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1308
1309                 return $this->wrapStatus( $this->lockManager->unlock( $paths, $type ) );
1310         }
1311
1312         /**
1313          * Lock the files at the given storage paths in the backend.
1314          * This will either lock all the files or none (on failure).
1315          * On failure, the StatusValue object will be updated with errors.
1316          *
1317          * Once the return value goes out scope, the locks will be released and
1318          * the StatusValue updated. Unlock fatals will not change the StatusValue "OK" value.
1319          *
1320          * @see ScopedLock::factory()
1321          *
1322          * @param array $paths List of storage paths or map of lock types to path lists
1323          * @param int|string $type LockManager::LOCK_* constant or "mixed"
1324          * @param StatusValue $status StatusValue to update on lock/unlock
1325          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.24)
1326          * @return ScopedLock|null Returns null on failure
1327          */
1328         final public function getScopedFileLocks(
1329                 array $paths, $type, StatusValue $status, $timeout = 0
1330         ) {
1331                 if ( $type === 'mixed' ) {
1332                         foreach ( $paths as &$typePaths ) {
1333                                 $typePaths = array_map( 'FileBackend::normalizeStoragePath', $typePaths );
1334                         }
1335                 } else {
1336                         $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1337                 }
1338
1339                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status, $timeout );
1340         }
1341
1342         /**
1343          * Get an array of scoped locks needed for a batch of file operations.
1344          *
1345          * Normally, FileBackend::doOperations() handles locking, unless
1346          * the 'nonLocking' param is passed in. This function is useful if you
1347          * want the files to be locked for a broader scope than just when the
1348          * files are changing. For example, if you need to update DB metadata,
1349          * you may want to keep the files locked until finished.
1350          *
1351          * @see FileBackend::doOperations()
1352          *
1353          * @param array $ops List of file operations to FileBackend::doOperations()
1354          * @param StatusValue $status StatusValue to update on lock/unlock
1355          * @return ScopedLock|null
1356          * @since 1.20
1357          */
1358         abstract public function getScopedLocksForOps( array $ops, StatusValue $status );
1359
1360         /**
1361          * Get the root storage path of this backend.
1362          * All container paths are "subdirectories" of this path.
1363          *
1364          * @return string Storage path
1365          * @since 1.20
1366          */
1367         final public function getRootStoragePath() {
1368                 return "mwstore://{$this->name}";
1369         }
1370
1371         /**
1372          * Get the storage path for the given container for this backend
1373          *
1374          * @param string $container Container name
1375          * @return string Storage path
1376          * @since 1.21
1377          */
1378         final public function getContainerStoragePath( $container ) {
1379                 return $this->getRootStoragePath() . "/{$container}";
1380         }
1381
1382         /**
1383          * Get the file journal object for this backend
1384          *
1385          * @return FileJournal
1386          */
1387         final public function getJournal() {
1388                 return $this->fileJournal;
1389         }
1390
1391         /**
1392          * Convert FSFile 'src' paths to string paths (with an 'srcRef' field set to the FSFile)
1393          *
1394          * The 'srcRef' field keeps any TempFSFile objects in scope for the backend to have it
1395          * around as long it needs (which may vary greatly depending on configuration)
1396          *
1397          * @param array $ops File operation batch for FileBaclend::doOperations()
1398          * @return array File operation batch
1399          */
1400         protected function resolveFSFileObjects( array $ops ) {
1401                 foreach ( $ops as &$op ) {
1402                         $src = $op['src'] ?? null;
1403                         if ( $src instanceof FSFile ) {
1404                                 $op['srcRef'] = $src;
1405                                 $op['src'] = $src->getPath();
1406                         }
1407                 }
1408                 unset( $op );
1409
1410                 return $ops;
1411         }
1412
1413         /**
1414          * Check if a given path is a "mwstore://" path.
1415          * This does not do any further validation or any existence checks.
1416          *
1417          * @param string $path
1418          * @return bool
1419          */
1420         final public static function isStoragePath( $path ) {
1421                 return ( strpos( $path, 'mwstore://' ) === 0 );
1422         }
1423
1424         /**
1425          * Split a storage path into a backend name, a container name,
1426          * and a relative file path. The relative path may be the empty string.
1427          * This does not do any path normalization or traversal checks.
1428          *
1429          * @param string $storagePath
1430          * @return array (backend, container, rel object) or (null, null, null)
1431          */
1432         final public static function splitStoragePath( $storagePath ) {
1433                 if ( self::isStoragePath( $storagePath ) ) {
1434                         // Remove the "mwstore://" prefix and split the path
1435                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
1436                         if ( count( $parts ) >= 2 && $parts[0] != '' && $parts[1] != '' ) {
1437                                 if ( count( $parts ) == 3 ) {
1438                                         return $parts; // e.g. "backend/container/path"
1439                                 } else {
1440                                         return [ $parts[0], $parts[1], '' ]; // e.g. "backend/container"
1441                                 }
1442                         }
1443                 }
1444
1445                 return [ null, null, null ];
1446         }
1447
1448         /**
1449          * Normalize a storage path by cleaning up directory separators.
1450          * Returns null if the path is not of the format of a valid storage path.
1451          *
1452          * @param string $storagePath
1453          * @return string|null
1454          */
1455         final public static function normalizeStoragePath( $storagePath ) {
1456                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
1457                 if ( $relPath !== null ) { // must be for this backend
1458                         $relPath = self::normalizeContainerPath( $relPath );
1459                         if ( $relPath !== null ) {
1460                                 return ( $relPath != '' )
1461                                         ? "mwstore://{$backend}/{$container}/{$relPath}"
1462                                         : "mwstore://{$backend}/{$container}";
1463                         }
1464                 }
1465
1466                 return null;
1467         }
1468
1469         /**
1470          * Get the parent storage directory of a storage path.
1471          * This returns a path like "mwstore://backend/container",
1472          * "mwstore://backend/container/...", or null if there is no parent.
1473          *
1474          * @param string $storagePath
1475          * @return string|null
1476          */
1477         final public static function parentStoragePath( $storagePath ) {
1478                 $storagePath = dirname( $storagePath );
1479                 list( , , $rel ) = self::splitStoragePath( $storagePath );
1480
1481                 return ( $rel === null ) ? null : $storagePath;
1482         }
1483
1484         /**
1485          * Get the final extension from a storage or FS path
1486          *
1487          * @param string $path
1488          * @param string $case One of (rawcase, uppercase, lowercase) (since 1.24)
1489          * @return string
1490          */
1491         final public static function extensionFromPath( $path, $case = 'lowercase' ) {
1492                 $i = strrpos( $path, '.' );
1493                 $ext = $i ? substr( $path, $i + 1 ) : '';
1494
1495                 if ( $case === 'lowercase' ) {
1496                         $ext = strtolower( $ext );
1497                 } elseif ( $case === 'uppercase' ) {
1498                         $ext = strtoupper( $ext );
1499                 }
1500
1501                 return $ext;
1502         }
1503
1504         /**
1505          * Check if a relative path has no directory traversals
1506          *
1507          * @param string $path
1508          * @return bool
1509          * @since 1.20
1510          */
1511         final public static function isPathTraversalFree( $path ) {
1512                 return ( self::normalizeContainerPath( $path ) !== null );
1513         }
1514
1515         /**
1516          * Build a Content-Disposition header value per RFC 6266.
1517          *
1518          * @param string $type One of (attachment, inline)
1519          * @param string $filename Suggested file name (should not contain slashes)
1520          * @throws FileBackendError
1521          * @return string
1522          * @since 1.20
1523          */
1524         final public static function makeContentDisposition( $type, $filename = '' ) {
1525                 $parts = [];
1526
1527                 $type = strtolower( $type );
1528                 if ( !in_array( $type, [ 'inline', 'attachment' ] ) ) {
1529                         throw new InvalidArgumentException( "Invalid Content-Disposition type '$type'." );
1530                 }
1531                 $parts[] = $type;
1532
1533                 if ( strlen( $filename ) ) {
1534                         $parts[] = "filename*=UTF-8''" . rawurlencode( basename( $filename ) );
1535                 }
1536
1537                 return implode( ';', $parts );
1538         }
1539
1540         /**
1541          * Validate and normalize a relative storage path.
1542          * Null is returned if the path involves directory traversal.
1543          * Traversal is insecure for FS backends and broken for others.
1544          *
1545          * This uses the same traversal protection as Title::secureAndSplit().
1546          *
1547          * @param string $path Storage path relative to a container
1548          * @return string|null
1549          */
1550         final protected static function normalizeContainerPath( $path ) {
1551                 // Normalize directory separators
1552                 $path = strtr( $path, '\\', '/' );
1553                 // Collapse any consecutive directory separators
1554                 $path = preg_replace( '![/]{2,}!', '/', $path );
1555                 // Remove any leading directory separator
1556                 $path = ltrim( $path, '/' );
1557                 // Use the same traversal protection as Title::secureAndSplit()
1558                 if ( strpos( $path, '.' ) !== false ) {
1559                         if (
1560                                 $path === '.' ||
1561                                 $path === '..' ||
1562                                 strpos( $path, './' ) === 0 ||
1563                                 strpos( $path, '../' ) === 0 ||
1564                                 strpos( $path, '/./' ) !== false ||
1565                                 strpos( $path, '/../' ) !== false
1566                         ) {
1567                                 return null;
1568                         }
1569                 }
1570
1571                 return $path;
1572         }
1573
1574         /**
1575          * Yields the result of the status wrapper callback on either:
1576          *   - StatusValue::newGood() if this method is called without parameters
1577          *   - StatusValue::newFatal() with all parameters to this method if passed in
1578          *
1579          * @param string ...$args
1580          * @return StatusValue
1581          */
1582         final protected function newStatus( ...$args ) {
1583                 if ( count( $args ) ) {
1584                         $sv = StatusValue::newFatal( ...$args );
1585                 } else {
1586                         $sv = StatusValue::newGood();
1587                 }
1588
1589                 return $this->wrapStatus( $sv );
1590         }
1591
1592         /**
1593          * @param StatusValue $sv
1594          * @return StatusValue Modified status or StatusValue subclass
1595          */
1596         final protected function wrapStatus( StatusValue $sv ) {
1597                 return $this->statusWrapper ? call_user_func( $this->statusWrapper, $sv ) : $sv;
1598         }
1599
1600         /**
1601          * @param string $section
1602          * @return ScopedCallback|null
1603          */
1604         protected function scopedProfileSection( $section ) {
1605                 return $this->profiler ? ( $this->profiler )( $section ) : null;
1606         }
1607
1608         protected function resetOutputBuffer() {
1609                 while ( ob_get_status() ) {
1610                         if ( !ob_end_clean() ) {
1611                                 // Could not remove output buffer handler; abort now
1612                                 // to avoid getting in some kind of infinite loop.
1613                                 break;
1614                         }
1615                 }
1616         }
1617 }