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
  34 /**
  35  * @brief Base class for all file backend classes (including multi-write backends).
  36  *
  37  * This class defines the methods as abstract that subclasses must implement.
  38  * Outside callers can assume that all backends will have these functions.
  39  *
  40  * All "storage paths" are of the format "mwstore://<backend>/<container>/<path>".
  41  * The "backend" portion is unique name for the application to refer to a backend, while
  42  * the "container" portion is a top-level directory of the backend. The "path" portion
  43  * is a relative path that uses UNIX file system (FS) notation, though any particular
  44  * backend may not actually be using a local filesystem. Therefore, the relative paths
  45  * are only virtual.
  46  *
  47  * Backend contents are stored under "domain"-specific container names by default.
  48  * A domain is simply a logical umbrella for entities, such as those belonging to a certain
  49  * application or portion of a website, for example. A domain can be local or global.
  50  * Global (qualified) backends are achieved by configuring the "domain ID" to a constant.
  51  * Global domains are simpler, but local domains can be used by choosing a domain ID based on
  52  * the current context, such as which language of a website is being used.
  53  *
  54  * For legacy reasons, the FSFileBackend class allows manually setting the paths of
  55  * containers to ones that do not respect the "domain ID".
  56  *
  57  * In key/value (object) stores, containers are the only hierarchy (the rest is emulated).
  58  * FS-based backends are somewhat more restrictive due to the existence of real
  59  * directory files; a regular file cannot have the same name as a directory. Other
  60  * backends with virtual directories may not have this limitation. Callers should
  61  * store files in such a way that no files and directories are under the same path.
  62  *
  63  * In general, this class allows for callers to access storage through the same
  64  * interface, without regard to the underlying storage system. However, calling code
  65  * must follow certain patterns and be aware of certain things to ensure compatibility:
  66  *   - a) Always call prepare() on the parent directory before trying to put a file there;
  67  *        key/value stores only need the container to exist first, but filesystems need
  68  *        all the parent directories to exist first (prepare() is aware of all this)
  69  *   - b) Always call clean() on a directory when it might become empty to avoid empty
  70  *        directory buildup on filesystems; key/value stores never have empty directories,
  71  *        so doing this helps preserve consistency in both cases
  72  *   - c) Likewise, do not rely on the existence of empty directories for anything;
  73  *        calling directoryExists() on a path that prepare() was previously called on
  74  *        will return false for key/value stores if there are no files under that path
  75  *   - d) Never alter the resulting FSFile returned from getLocalReference(), as it could
  76  *        either be a copy of the source file in /tmp or the original source file itself
  77  *   - e) Use a file layout that results in never attempting to store files over directories
  78  *        or directories over files; key/value stores allow this but filesystems do not
  79  *   - f) Use ASCII file names (e.g. base32, IDs, hashes) to avoid Unicode issues in Windows
  80  *   - g) Do not assume that move operations are atomic (difficult with key/value stores)
  81  *   - h) Do not assume that file stat or read operations always have immediate consistency;
  82  *        various methods have a "latest" flag that should always be used if up-to-date
  83  *        information is required (this trades performance for correctness as needed)
  84  *   - i) Do not assume that directory listings have immediate consistency
  85  *
  86  * Methods of subclasses should avoid throwing exceptions at all costs.
  87  * As a corollary, external dependencies should be kept to a minimum.
  88  *
  89  * @ingroup FileBackend
  90  * @since 1.19
  91  */
  92 abstract class FileBackend implements LoggerAwareInterface {
  93         /** @var string Unique backend name */
  94         protected $name;
  95
  96         /** @var string Unique domain name */
  97         protected $domainId;
  98
  99         /** @var string Read-only explanation message */
 100         protected $readOnly;
 101
 102         /** @var string When to do operations in parallel */
 103         protected $parallelize;
 104
 105         /** @var int How many operations can be done in parallel */
 106         protected $concurrency;
 107
 108         /** @var string Temporary file directory */
 109         protected $tmpDirectory;
 110
 111         /** @var LockManager */
 112         protected $lockManager;
 113         /** @var FileJournal */
 114         protected $fileJournal;
 115         /** @var LoggerInterface */
 116         protected $logger;
 117         /** @var callable|null */
 118         protected $profiler;
 119
 120         /** @var callable */
 121         protected $obResetFunc;
 122         /** @var callable */
 123         protected $streamMimeFunc;
 124         /** @var callable */
 125         protected $statusWrapper;
 126
 127         /** Bitfield flags for supported features */
 128         const ATTR_HEADERS = 1; // files can be tagged with standard HTTP headers
 129         const ATTR_METADATA = 2; // files can be stored with metadata key/values
 130         const ATTR_UNICODE_PATHS = 4; // files can have Unicode paths (not just ASCII)
 131
 132         /**
 133          * Create a new backend instance from configuration.
 134          * This should only be called from within FileBackendGroup.
 135          *
 136          * @param array $config Parameters include:
 137          *   - name : The unique name of this backend.
 138          *      This should consist of alphanumberic, '-', and '_' characters.
 139          *      This name should not be changed after use (e.g. with journaling).
 140          *      Note that the name is *not* used in actual container names.
 141          *   - domainId : Prefix to container names that is unique to this backend.
 142          *      It should only consist of alphanumberic, '-', and '_' characters.
 143          *      This ID is what avoids collisions if multiple logical backends
 144          *      use the same storage system, so this should be set carefully.
 145          *   - lockManager : LockManager object to use for any file locking.
 146          *      If not provided, then no file locking will be enforced.
 147          *   - fileJournal : FileJournal object to use for logging changes to files.
 148          *      If not provided, then change journaling will be disabled.
 149          *   - readOnly : Write operations are disallowed if this is a non-empty string.
 150          *      It should be an explanation for the backend being read-only.
 151          *   - parallelize : When to do file operations in parallel (when possible).
 152          *      Allowed values are "implicit", "explicit" and "off".
 153          *   - concurrency : How many file operations can be done in parallel.
 154          *   - tmpDirectory : Directory to use for temporary files. If this is not set or null,
 155          *      then the backend will try to discover a usable temporary directory.
 156          *   - obResetFunc : alternative callback to clear the output buffer
 157          *   - streamMimeFunc : alternative method to determine the content type from the path
 158          *   - logger : Optional PSR logger object.
 159          *   - profiler : Optional callback that takes a section name argument and returns
 160          *      a ScopedCallback instance that ends the profile section in its destructor.
 161          * @throws InvalidArgumentException
 162          */
 163         public function __construct( array $config ) {
 164                 $this->name = $config['name'];
 165                 $this->domainId = $config['domainId'] // e.g. "my_wiki-en_"
 166                         ?? $config['wikiId']; // b/c alias
 167                 if ( !preg_match( '!^[a-zA-Z0-9-_]{1,255}$!', $this->name ) ) {
 168                         throw new InvalidArgumentException( "Backend name '{$this->name}' is invalid." );
 169                 } elseif ( !is_string( $this->domainId ) ) {
 170                         throw new InvalidArgumentException(
 171                                 "Backend domain ID not provided for '{$this->name}'." );
 172                 }
 173                 $this->lockManager = $config['lockManager'] ?? new NullLockManager( [] );
 174                 $this->fileJournal = $config['fileJournal']
 175                         ?? FileJournal::factory( [ 'class' => NullFileJournal::class ], $this->name );
 176                 $this->readOnly = isset( $config['readOnly'] )
 177                         ? (string)$config['readOnly']
 178                         : '';
 179                 $this->parallelize = isset( $config['parallelize'] )
 180                         ? (string)$config['parallelize']
 181                         : 'off';
 182                 $this->concurrency = isset( $config['concurrency'] )
 183                         ? (int)$config['concurrency']
 184                         : 50;
 185                 $this->obResetFunc = $config['obResetFunc'] ?? [ $this, 'resetOutputBuffer' ];
 186                 $this->streamMimeFunc = $config['streamMimeFunc'] ?? null;
 187                 $this->statusWrapper = $config['statusWrapper'] ?? null;
 188
 189                 $this->profiler = $config['profiler'] ?? null;
 190                 if ( !is_callable( $this->profiler ) ) {
 191                         $this->profiler = null;
 192                 }
 193                 $this->logger = $config['logger'] ?? new \Psr\Log\NullLogger();
 194                 $this->statusWrapper = $config['statusWrapper'] ?? null;
 195                 $this->tmpDirectory = $config['tmpDirectory'] ?? null;
 196         }
 197
 198         public function setLogger( LoggerInterface $logger ) {
 199                 $this->logger = $logger;
 200         }
 201
 202         /**
 203          * Get the unique backend name.
 204          * We may have multiple different backends of the same type.
 205          * For example, we can have two Swift backends using different proxies.
 206          *
 207          * @return string
 208          */
 209         final public function getName() {
 210                 return $this->name;
 211         }
 212
 213         /**
 214          * Get the domain identifier used for this backend (possibly empty).
 215          *
 216          * @return string
 217          * @since 1.28
 218          */
 219         final public function getDomainId() {
 220                 return $this->domainId;
 221         }
 222
 223         /**
 224          * Alias to getDomainId()
 225          * @return string
 226          * @since 1.20
 227          */
 228         final public function getWikiId() {
 229                 return $this->getDomainId();
 230         }
 231
 232         /**
 233          * Check if this backend is read-only
 234          *
 235          * @return bool
 236          */
 237         final public function isReadOnly() {
 238                 return ( $this->readOnly != '' );
 239         }
 240
 241         /**
 242          * Get an explanatory message if this backend is read-only
 243          *
 244          * @return string|bool Returns false if the backend is not read-only
 245          */
 246         final public function getReadOnlyReason() {
 247                 return ( $this->readOnly != '' ) ? $this->readOnly : false;
 248         }
 249
 250         /**
 251          * Get the a bitfield of extra features supported by the backend medium
 252          *
 253          * @return int Bitfield of FileBackend::ATTR_* flags
 254          * @since 1.23
 255          */
 256         public function getFeatures() {
 257                 return self::ATTR_UNICODE_PATHS;
 258         }
 259
 260         /**
 261          * Check if the backend medium supports a field of extra features
 262          *
 263          * @param int $bitfield Bitfield of FileBackend::ATTR_* flags
 264          * @return bool
 265          * @since 1.23
 266          */
 267         final public function hasFeatures( $bitfield ) {
 268                 return ( $this->getFeatures() & $bitfield ) === $bitfield;
 269         }
 270
 271         /**
 272          * This is the main entry point into the backend for write operations.
 273          * Callers supply an ordered list of operations to perform as a transaction.
 274          * Files will be locked, the stat cache cleared, and then the operations attempted.
 275          * If any serious errors occur, all attempted operations will be rolled back.
 276          *
 277          * $ops is an array of arrays. The outer array holds a list of operations.
 278          * Each inner array is a set of key value pairs that specify an operation.
 279          *
 280          * Supported operations and their parameters. The supported actions are:
 281          *  - create
 282          *  - store
 283          *  - copy
 284          *  - move
 285          *  - delete
 286          *  - describe (since 1.21)
 287          *  - null
 288          *
 289          * FSFile/TempFSFile object support was added in 1.27.
 290          *
 291          * a) Create a new file in storage with the contents of a string
 292          * @code
 293          *     [
 294          *         'op'                  => 'create',
 295          *         'dst'                 => <storage path>,
 296          *         'content'             => <string of new file contents>,
 297          *         'overwrite'           => <boolean>,
 298          *         'overwriteSame'       => <boolean>,
 299          *         'headers'             => <HTTP header name/value map> # since 1.21
 300          *     ]
 301          * @endcode
 302          *
 303          * b) Copy a file system file into storage
 304          * @code
 305          *     [
 306          *         'op'                  => 'store',
 307          *         'src'                 => <file system path, FSFile, or TempFSFile>,
 308          *         'dst'                 => <storage path>,
 309          *         'overwrite'           => <boolean>,
 310          *         'overwriteSame'       => <boolean>,
 311          *         'headers'             => <HTTP header name/value map> # since 1.21
 312          *     ]
 313          * @endcode
 314          *
 315          * c) Copy a file within storage
 316          * @code
 317          *     [
 318          *         'op'                  => 'copy',
 319          *         'src'                 => <storage path>,
 320          *         'dst'                 => <storage path>,
 321          *         'overwrite'           => <boolean>,
 322          *         'overwriteSame'       => <boolean>,
 323          *         'ignoreMissingSource' => <boolean>, # since 1.21
 324          *         'headers'             => <HTTP header name/value map> # since 1.21
 325          *     ]
 326          * @endcode
 327          *
 328          * d) Move a file within storage
 329          * @code
 330          *     [
 331          *         'op'                  => 'move',
 332          *         'src'                 => <storage path>,
 333          *         'dst'                 => <storage path>,
 334          *         'overwrite'           => <boolean>,
 335          *         'overwriteSame'       => <boolean>,
 336          *         'ignoreMissingSource' => <boolean>, # since 1.21
 337          *         'headers'             => <HTTP header name/value map> # since 1.21
 338          *     ]
 339          * @endcode
 340          *
 341          * e) Delete a file within storage
 342          * @code
 343          *     [
 344          *         'op'                  => 'delete',
 345          *         'src'                 => <storage path>,
 346          *         'ignoreMissingSource' => <boolean>
 347          *     ]
 348          * @endcode
 349          *
 350          * f) Update metadata for a file within storage
 351          * @code
 352          *     [
 353          *         'op'                  => 'describe',
 354          *         'src'                 => <storage path>,
 355          *         'headers'             => <HTTP header name/value map>
 356          *     ]
 357          * @endcode
 358          *
 359          * g) Do nothing (no-op)
 360          * @code
 361          *     [
 362          *         'op'                  => 'null',
 363          *     ]
 364          * @endcode
 365          *
 366          * Boolean flags for operations (operation-specific):
 367          *   - ignoreMissingSource : The operation will simply succeed and do
 368          *                           nothing if the source file does not exist.
 369          *   - overwrite           : Any destination file will be overwritten.
 370          *   - overwriteSame       : If a file already exists at the destination with the
 371          *                           same contents, then do nothing to the destination file
 372          *                           instead of giving an error. This does not compare headers.
 373          *                           This option is ignored if 'overwrite' is already provided.
 374          *   - headers             : If supplied, the result of merging these headers with any
 375          *                           existing source file headers (replacing conflicting ones)
 376          *                           will be set as the destination file headers. Headers are
 377          *                           deleted if their value is set to the empty string. When a
 378          *                           file has headers they are included in responses to GET and
 379          *                           HEAD requests to the backing store for that file.
 380          *                           Header values should be no larger than 255 bytes, except for
 381          *                           Content-Disposition. The system might ignore or truncate any
 382          *                           headers that are too long to store (exact limits will vary).
 383          *                           Backends that don't support metadata ignore this. (since 1.21)
 384          *
 385          * $opts is an associative of boolean flags, including:
 386          *   - force               : Operation precondition errors no longer trigger an abort.
 387          *                           Any remaining operations are still attempted. Unexpected
 388          *                           failures may still cause remaining operations to be aborted.
 389          *   - nonLocking          : No locks are acquired for the operations.
 390          *                           This can increase performance for non-critical writes.
 391          *                           This has no effect unless the 'force' flag is set.
 392          *   - nonJournaled        : Don't log this operation batch in the file journal.
 393          *                           This limits the ability of recovery scripts.
 394          *   - parallelize         : Try to do operations in parallel when possible.
 395          *   - bypassReadOnly      : Allow writes in read-only mode. (since 1.20)
 396          *   - preserveCache       : Don't clear the process cache before checking files.
 397          *                           This should only be used if all entries in the process
 398          *                           cache were added after the files were already locked. (since 1.20)
 399          *
 400          * @note Remarks on locking:
 401          * File system paths given to operations should refer to files that are
 402          * already locked or otherwise safe from modification from other processes.
 403          * Normally these files will be new temp files, which should be adequate.
 404          *
 405          * @par Return value:
 406          *
 407          * This returns a Status, which contains all warnings and fatals that occurred
 408          * during the operation. The 'failCount', 'successCount', and 'success' members
 409          * will reflect each operation attempted.
 410          *
 411          * The StatusValue will be "OK" unless:
 412          *   - a) unexpected operation errors occurred (network partitions, disk full...)
 413          *   - b) significant operation errors occurred and 'force' was not set
 414          *
 415          * @param array $ops List of operations to execute in order
 416          * @param array $opts Batch operation options
 417          * @return StatusValue
 418          */
 419         final public function doOperations( array $ops, array $opts = [] ) {
 420                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 421                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 422                 }
 423                 if ( $ops === [] ) {
 424                         return $this->newStatus(); // nothing to do
 425                 }
 426
 427                 $ops = $this->resolveFSFileObjects( $ops );
 428                 if ( empty( $opts['force'] ) ) { // sanity
 429                         unset( $opts['nonLocking'] );
 430                 }
 431
 432                 /** @noinspection PhpUnusedLocalVariableInspection */
 433                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 434
 435                 return $this->doOperationsInternal( $ops, $opts );
 436         }
 437
 438         /**
 439          * @see FileBackend::doOperations()
 440          * @param array $ops
 441          * @param array $opts
 442          * @return StatusValue
 443          */
 444         abstract protected function doOperationsInternal( array $ops, array $opts );
 445
 446         /**
 447          * Same as doOperations() except it takes a single operation.
 448          * If you are doing a batch of operations that should either
 449          * all succeed or all fail, then use that function instead.
 450          *
 451          * @see FileBackend::doOperations()
 452          *
 453          * @param array $op Operation
 454          * @param array $opts Operation options
 455          * @return StatusValue
 456          */
 457         final public function doOperation( array $op, array $opts = [] ) {
 458                 return $this->doOperations( [ $op ], $opts );
 459         }
 460
 461         /**
 462          * Performs a single create operation.
 463          * This sets $params['op'] to 'create' and passes it to doOperation().
 464          *
 465          * @see FileBackend::doOperation()
 466          *
 467          * @param array $params Operation parameters
 468          * @param array $opts Operation options
 469          * @return StatusValue
 470          */
 471         final public function create( array $params, array $opts = [] ) {
 472                 return $this->doOperation( [ 'op' => 'create' ] + $params, $opts );
 473         }
 474
 475         /**
 476          * Performs a single store operation.
 477          * This sets $params['op'] to 'store' and passes it to doOperation().
 478          *
 479          * @see FileBackend::doOperation()
 480          *
 481          * @param array $params Operation parameters
 482          * @param array $opts Operation options
 483          * @return StatusValue
 484          */
 485         final public function store( array $params, array $opts = [] ) {
 486                 return $this->doOperation( [ 'op' => 'store' ] + $params, $opts );
 487         }
 488
 489         /**
 490          * Performs a single copy operation.
 491          * This sets $params['op'] to 'copy' and passes it to doOperation().
 492          *
 493          * @see FileBackend::doOperation()
 494          *
 495          * @param array $params Operation parameters
 496          * @param array $opts Operation options
 497          * @return StatusValue
 498          */
 499         final public function copy( array $params, array $opts = [] ) {
 500                 return $this->doOperation( [ 'op' => 'copy' ] + $params, $opts );
 501         }
 502
 503         /**
 504          * Performs a single move operation.
 505          * This sets $params['op'] to 'move' and passes it to doOperation().
 506          *
 507          * @see FileBackend::doOperation()
 508          *
 509          * @param array $params Operation parameters
 510          * @param array $opts Operation options
 511          * @return StatusValue
 512          */
 513         final public function move( array $params, array $opts = [] ) {
 514                 return $this->doOperation( [ 'op' => 'move' ] + $params, $opts );
 515         }
 516
 517         /**
 518          * Performs a single delete operation.
 519          * This sets $params['op'] to 'delete' and passes it to doOperation().
 520          *
 521          * @see FileBackend::doOperation()
 522          *
 523          * @param array $params Operation parameters
 524          * @param array $opts Operation options
 525          * @return StatusValue
 526          */
 527         final public function delete( array $params, array $opts = [] ) {
 528                 return $this->doOperation( [ 'op' => 'delete' ] + $params, $opts );
 529         }
 530
 531         /**
 532          * Performs a single describe operation.
 533          * This sets $params['op'] to 'describe' and passes it to doOperation().
 534          *
 535          * @see FileBackend::doOperation()
 536          *
 537          * @param array $params Operation parameters
 538          * @param array $opts Operation options
 539          * @return StatusValue
 540          * @since 1.21
 541          */
 542         final public function describe( array $params, array $opts = [] ) {
 543                 return $this->doOperation( [ 'op' => 'describe' ] + $params, $opts );
 544         }
 545
 546         /**
 547          * Perform a set of independent file operations on some files.
 548          *
 549          * This does no locking, nor journaling, and possibly no stat calls.
 550          * Any destination files that already exist will be overwritten.
 551          * This should *only* be used on non-original files, like cache files.
 552          *
 553          * Supported operations and their parameters:
 554          *  - create
 555          *  - store
 556          *  - copy
 557          *  - move
 558          *  - delete
 559          *  - describe (since 1.21)
 560          *  - null
 561          *
 562          * FSFile/TempFSFile object support was added in 1.27.
 563          *
 564          * a) Create a new file in storage with the contents of a string
 565          * @code
 566          *     [
 567          *         'op'                  => 'create',
 568          *         'dst'                 => <storage path>,
 569          *         'content'             => <string of new file contents>,
 570          *         'headers'             => <HTTP header name/value map> # since 1.21
 571          *     ]
 572          * @endcode
 573          *
 574          * b) Copy a file system file into storage
 575          * @code
 576          *     [
 577          *         'op'                  => 'store',
 578          *         'src'                 => <file system path, FSFile, or TempFSFile>,
 579          *         'dst'                 => <storage path>,
 580          *         'headers'             => <HTTP header name/value map> # since 1.21
 581          *     ]
 582          * @endcode
 583          *
 584          * c) Copy a file within storage
 585          * @code
 586          *     [
 587          *         'op'                  => 'copy',
 588          *         'src'                 => <storage path>,
 589          *         'dst'                 => <storage path>,
 590          *         'ignoreMissingSource' => <boolean>, # since 1.21
 591          *         'headers'             => <HTTP header name/value map> # since 1.21
 592          *     ]
 593          * @endcode
 594          *
 595          * d) Move a file within storage
 596          * @code
 597          *     [
 598          *         'op'                  => 'move',
 599          *         'src'                 => <storage path>,
 600          *         'dst'                 => <storage path>,
 601          *         'ignoreMissingSource' => <boolean>, # since 1.21
 602          *         'headers'             => <HTTP header name/value map> # since 1.21
 603          *     ]
 604          * @endcode
 605          *
 606          * e) Delete a file within storage
 607          * @code
 608          *     [
 609          *         'op'                  => 'delete',
 610          *         'src'                 => <storage path>,
 611          *         'ignoreMissingSource' => <boolean>
 612          *     ]
 613          * @endcode
 614          *
 615          * f) Update metadata for a file within storage
 616          * @code
 617          *     [
 618          *         'op'                  => 'describe',
 619          *         'src'                 => <storage path>,
 620          *         'headers'             => <HTTP header name/value map>
 621          *     ]
 622          * @endcode
 623          *
 624          * g) Do nothing (no-op)
 625          * @code
 626          *     [
 627          *         'op'                  => 'null',
 628          *     ]
 629          * @endcode
 630          *
 631          * @par Boolean flags for operations (operation-specific):
 632          *   - ignoreMissingSource : The operation will simply succeed and do
 633          *                           nothing if the source file does not exist.
 634          *   - headers             : If supplied with a header name/value map, the backend will
 635          *                           reply with these headers when GETs/HEADs of the destination
 636          *                           file are made. Header values should be smaller than 256 bytes.
 637          *                           Content-Disposition headers can be longer, though the system
 638          *                           might ignore or truncate ones that are too long to store.
 639          *                           Existing headers will remain, but these will replace any
 640          *                           conflicting previous headers, and headers will be removed
 641          *                           if they are set to an empty string.
 642          *                           Backends that don't support metadata ignore this. (since 1.21)
 643          *
 644          * $opts is an associative of boolean flags, including:
 645          *   - bypassReadOnly      : Allow writes in read-only mode (since 1.20)
 646          *
 647          * @par Return value:
 648          * This returns a Status, which contains all warnings and fatals that occurred
 649          * during the operation. The 'failCount', 'successCount', and 'success' members
 650          * will reflect each operation attempted for the given files. The StatusValue will be
 651          * considered "OK" as long as no fatal errors occurred.
 652          *
 653          * @param array $ops Set of operations to execute
 654          * @param array $opts Batch operation options
 655          * @return StatusValue
 656          * @since 1.20
 657          */
 658         final public function doQuickOperations( array $ops, array $opts = [] ) {
 659                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 660                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 661                 }
 662                 if ( $ops === [] ) {
 663                         return $this->newStatus(); // nothing to do
 664                 }
 665
 666                 $ops = $this->resolveFSFileObjects( $ops );
 667                 foreach ( $ops as &$op ) {
 668                         $op['overwrite'] = true; // avoids RTTs in key/value stores
 669                 }
 670
 671                 /** @noinspection PhpUnusedLocalVariableInspection */
 672                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 673
 674                 return $this->doQuickOperationsInternal( $ops );
 675         }
 676
 677         /**
 678          * @see FileBackend::doQuickOperations()
 679          * @param array $ops
 680          * @return StatusValue
 681          * @since 1.20
 682          */
 683         abstract protected function doQuickOperationsInternal( array $ops );
 684
 685         /**
 686          * Same as doQuickOperations() except it takes a single operation.
 687          * If you are doing a batch of operations, then use that function instead.
 688          *
 689          * @see FileBackend::doQuickOperations()
 690          *
 691          * @param array $op Operation
 692          * @return StatusValue
 693          * @since 1.20
 694          */
 695         final public function doQuickOperation( array $op ) {
 696                 return $this->doQuickOperations( [ $op ] );
 697         }
 698
 699         /**
 700          * Performs a single quick create operation.
 701          * This sets $params['op'] to 'create' and passes it to doQuickOperation().
 702          *
 703          * @see FileBackend::doQuickOperation()
 704          *
 705          * @param array $params Operation parameters
 706          * @return StatusValue
 707          * @since 1.20
 708          */
 709         final public function quickCreate( array $params ) {
 710                 return $this->doQuickOperation( [ 'op' => 'create' ] + $params );
 711         }
 712
 713         /**
 714          * Performs a single quick store operation.
 715          * This sets $params['op'] to 'store' and passes it to doQuickOperation().
 716          *
 717          * @see FileBackend::doQuickOperation()
 718          *
 719          * @param array $params Operation parameters
 720          * @return StatusValue
 721          * @since 1.20
 722          */
 723         final public function quickStore( array $params ) {
 724                 return $this->doQuickOperation( [ 'op' => 'store' ] + $params );
 725         }
 726
 727         /**
 728          * Performs a single quick copy operation.
 729          * This sets $params['op'] to 'copy' and passes it to doQuickOperation().
 730          *
 731          * @see FileBackend::doQuickOperation()
 732          *
 733          * @param array $params Operation parameters
 734          * @return StatusValue
 735          * @since 1.20
 736          */
 737         final public function quickCopy( array $params ) {
 738                 return $this->doQuickOperation( [ 'op' => 'copy' ] + $params );
 739         }
 740
 741         /**
 742          * Performs a single quick move operation.
 743          * This sets $params['op'] to 'move' and passes it to doQuickOperation().
 744          *
 745          * @see FileBackend::doQuickOperation()
 746          *
 747          * @param array $params Operation parameters
 748          * @return StatusValue
 749          * @since 1.20
 750          */
 751         final public function quickMove( array $params ) {
 752                 return $this->doQuickOperation( [ 'op' => 'move' ] + $params );
 753         }
 754
 755         /**
 756          * Performs a single quick delete operation.
 757          * This sets $params['op'] to 'delete' and passes it to doQuickOperation().
 758          *
 759          * @see FileBackend::doQuickOperation()
 760          *
 761          * @param array $params Operation parameters
 762          * @return StatusValue
 763          * @since 1.20
 764          */
 765         final public function quickDelete( array $params ) {
 766                 return $this->doQuickOperation( [ 'op' => 'delete' ] + $params );
 767         }
 768
 769         /**
 770          * Performs a single quick describe operation.
 771          * This sets $params['op'] to 'describe' and passes it to doQuickOperation().
 772          *
 773          * @see FileBackend::doQuickOperation()
 774          *
 775          * @param array $params Operation parameters
 776          * @return StatusValue
 777          * @since 1.21
 778          */
 779         final public function quickDescribe( array $params ) {
 780                 return $this->doQuickOperation( [ 'op' => 'describe' ] + $params );
 781         }
 782
 783         /**
 784          * Concatenate a list of storage files into a single file system file.
 785          * The target path should refer to a file that is already locked or
 786          * otherwise safe from modification from other processes. Normally,
 787          * the file will be a new temp file, which should be adequate.
 788          *
 789          * @param array $params Operation parameters, include:
 790          *   - srcs        : ordered source storage paths (e.g. chunk1, chunk2, ...)
 791          *   - dst         : file system path to 0-byte temp file
 792          *   - parallelize : try to do operations in parallel when possible
 793          * @return StatusValue
 794          */
 795         abstract public function concatenate( array $params );
 796
 797         /**
 798          * Prepare a storage directory for usage.
 799          * This will create any required containers and parent directories.
 800          * Backends using key/value stores only need to create the container.
 801          *
 802          * The 'noAccess' and 'noListing' parameters works the same as in secure(),
 803          * except they are only applied *if* the directory/container had to be created.
 804          * These flags should always be set for directories that have private files.
 805          * However, setting them is not guaranteed to actually do anything.
 806          * Additional server configuration may be needed to achieve the desired effect.
 807          *
 808          * @param array $params Parameters include:
 809          *   - dir            : storage directory
 810          *   - noAccess       : try to deny file access (since 1.20)
 811          *   - noListing      : try to deny file listing (since 1.20)
 812          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 813          * @return StatusValue
 814          */
 815         final public function prepare( array $params ) {
 816                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 817                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 818                 }
 819                 /** @noinspection PhpUnusedLocalVariableInspection */
 820                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 821                 return $this->doPrepare( $params );
 822         }
 823
 824         /**
 825          * @see FileBackend::prepare()
 826          * @param array $params
 827          * @return StatusValue
 828          */
 829         abstract protected function doPrepare( array $params );
 830
 831         /**
 832          * Take measures to block web access to a storage directory and
 833          * the container it belongs to. FS backends might add .htaccess
 834          * files whereas key/value store backends might revoke container
 835          * access to the storage user representing end-users in web requests.
 836          *
 837          * This is not guaranteed to actually make files or listings publicly hidden.
 838          * Additional server configuration may be needed to achieve the desired effect.
 839          *
 840          * @param array $params Parameters include:
 841          *   - dir            : storage directory
 842          *   - noAccess       : try to deny file access
 843          *   - noListing      : try to deny file listing
 844          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 845          * @return StatusValue
 846          */
 847         final public function secure( array $params ) {
 848                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 849                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 850                 }
 851                 /** @noinspection PhpUnusedLocalVariableInspection */
 852                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 853                 return $this->doSecure( $params );
 854         }
 855
 856         /**
 857          * @see FileBackend::secure()
 858          * @param array $params
 859          * @return StatusValue
 860          */
 861         abstract protected function doSecure( array $params );
 862
 863         /**
 864          * Remove measures to block web access to a storage directory and
 865          * the container it belongs to. FS backends might remove .htaccess
 866          * files whereas key/value store backends might grant container
 867          * access to the storage user representing end-users in web requests.
 868          * This essentially can undo the result of secure() calls.
 869          *
 870          * This is not guaranteed to actually make files or listings publicly viewable.
 871          * Additional server configuration may be needed to achieve the desired effect.
 872          *
 873          * @param array $params Parameters include:
 874          *   - dir            : storage directory
 875          *   - access         : try to allow file access
 876          *   - listing        : try to allow file listing
 877          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 878          * @return StatusValue
 879          * @since 1.20
 880          */
 881         final public function publish( array $params ) {
 882                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 883                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 884                 }
 885                 /** @noinspection PhpUnusedLocalVariableInspection */
 886                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 887                 return $this->doPublish( $params );
 888         }
 889
 890         /**
 891          * @see FileBackend::publish()
 892          * @param array $params
 893          * @return StatusValue
 894          */
 895         abstract protected function doPublish( array $params );
 896
 897         /**
 898          * Delete a storage directory if it is empty.
 899          * Backends using key/value stores may do nothing unless the directory
 900          * is that of an empty container, in which case it will be deleted.
 901          *
 902          * @param array $params Parameters include:
 903          *   - dir            : storage directory
 904          *   - recursive      : recursively delete empty subdirectories first (since 1.20)
 905          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 906          * @return StatusValue
 907          */
 908         final public function clean( array $params ) {
 909                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 910                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 911                 }
 912                 /** @noinspection PhpUnusedLocalVariableInspection */
 913                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 914                 return $this->doClean( $params );
 915         }
 916
 917         /**
 918          * @see FileBackend::clean()
 919          * @param array $params
 920          * @return StatusValue
 921          */
 922         abstract protected function doClean( array $params );
 923
 924         /**
 925          * Check if a file exists at a storage path in the backend.
 926          * This returns false if only a directory exists at the path.
 927          *
 928          * @param array $params Parameters include:
 929          *   - src    : source storage path
 930          *   - latest : use the latest available data
 931          * @return bool|null Returns null on failure
 932          */
 933         abstract public function fileExists( array $params );
 934
 935         /**
 936          * Get the last-modified timestamp of the file at a storage path.
 937          *
 938          * @param array $params Parameters include:
 939          *   - src    : source storage path
 940          *   - latest : use the latest available data
 941          * @return string|bool TS_MW timestamp or false on failure
 942          */
 943         abstract public function getFileTimestamp( array $params );
 944
 945         /**
 946          * Get the contents of a file at a storage path in the backend.
 947          * This should be avoided for potentially large files.
 948          *
 949          * @param array $params Parameters include:
 950          *   - src    : source storage path
 951          *   - latest : use the latest available data
 952          * @return string|bool Returns false on failure
 953          */
 954         final public function getFileContents( array $params ) {
 955                 $contents = $this->getFileContentsMulti(
 956                         [ 'srcs' => [ $params['src'] ] ] + $params );
 957
 958                 return $contents[$params['src']];
 959         }
 960
 961         /**
 962          * Like getFileContents() except it takes an array of storage paths
 963          * and returns a map of storage paths to strings (or null on failure).
 964          * The map keys (paths) are in the same order as the provided list of paths.
 965          *
 966          * @see FileBackend::getFileContents()
 967          *
 968          * @param array $params Parameters include:
 969          *   - srcs        : list of source storage paths
 970          *   - latest      : use the latest available data
 971          *   - parallelize : try to do operations in parallel when possible
 972          * @return array Map of (path name => string or false on failure)
 973          * @since 1.20
 974          */
 975         abstract public function getFileContentsMulti( array $params );
 976
 977         /**
 978          * Get metadata about a file at a storage path in the backend.
 979          * If the file does not exist, then this returns false.
 980          * Otherwise, the result is an associative array that includes:
 981          *   - headers  : map of HTTP headers used for GET/HEAD requests (name => value)
 982          *   - metadata : map of file metadata (name => value)
 983          * Metadata keys and headers names will be returned in all lower-case.
 984          * Additional values may be included for internal use only.
 985          *
 986          * Use FileBackend::hasFeatures() to check how well this is supported.
 987          *
 988          * @param array $params
 989          * $params include:
 990          *   - src    : source storage path
 991          *   - latest : use the latest available data
 992          * @return array|bool Returns false on failure
 993          * @since 1.23
 994          */
 995         abstract public function getFileXAttributes( array $params );
 996
 997         /**
 998          * Get the size (bytes) of a file at a storage path in the backend.
 999          *
1000          * @param array $params Parameters include:
1001          *   - src    : source storage path
1002          *   - latest : use the latest available data
1003          * @return int|bool Returns false on failure
1004          */
1005         abstract public function getFileSize( array $params );
1006
1007         /**
1008          * Get quick information about a file at a storage path in the backend.
1009          * If the file does not exist, then this returns false.
1010          * Otherwise, the result is an associative array that includes:
1011          *   - mtime  : the last-modified timestamp (TS_MW)
1012          *   - size   : the file size (bytes)
1013          * Additional values may be included for internal use only.
1014          *
1015          * @param array $params Parameters include:
1016          *   - src    : source storage path
1017          *   - latest : use the latest available data
1018          * @return array|bool|null Returns null on failure
1019          */
1020         abstract public function getFileStat( array $params );
1021
1022         /**
1023          * Get a SHA-1 hash of the file at a storage path in the backend.
1024          *
1025          * @param array $params Parameters include:
1026          *   - src    : source storage path
1027          *   - latest : use the latest available data
1028          * @return string|bool Hash string or false on failure
1029          */
1030         abstract public function getFileSha1Base36( array $params );
1031
1032         /**
1033          * Get the properties of the file at a storage path in the backend.
1034          * This gives the result of FSFile::getProps() on a local copy of the file.
1035          *
1036          * @param array $params Parameters include:
1037          *   - src    : source storage path
1038          *   - latest : use the latest available data
1039          * @return array Returns FSFile::placeholderProps() on failure
1040          */
1041         abstract public function getFileProps( array $params );
1042
1043         /**
1044          * Stream the file at a storage path in the backend.
1045          *
1046          * If the file does not exists, an HTTP 404 error will be given.
1047          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
1048          * will be sent if streaming began, while none will be sent otherwise.
1049          * Implementations should flush the output buffer before sending data.
1050          *
1051          * @param array $params Parameters include:
1052          *   - src      : source storage path
1053          *   - headers  : list of additional HTTP headers to send if the file exists
1054          *   - options  : HTTP request header map with lower case keys (since 1.28). Supports:
1055          *                range             : format is "bytes=(\d*-\d*)"
1056          *                if-modified-since : format is an HTTP date
1057          *   - headless : only include the body (and headers from "headers") (since 1.28)
1058          *   - latest   : use the latest available data
1059          *   - allowOB  : preserve any output buffers (since 1.28)
1060          * @return StatusValue
1061          */
1062         abstract public function streamFile( array $params );
1063
1064         /**
1065          * Returns a file system file, identical to the file at a storage path.
1066          * The file returned is either:
1067          *   - a) A local copy of the file at a storage path in the backend.
1068          *        The temporary copy will have the same extension as the source.
1069          *   - b) An original of the file at a storage path in the backend.
1070          * Temporary files may be purged when the file object falls out of scope.
1071          *
1072          * Write operations should *never* be done on this file as some backends
1073          * may do internal tracking or may be instances of FileBackendMultiWrite.
1074          * In that latter case, there are copies of the file that must stay in sync.
1075          * Additionally, further calls to this function may return the same file.
1076          *
1077          * @param array $params Parameters include:
1078          *   - src    : source storage path
1079          *   - latest : use the latest available data
1080          * @return FSFile|null Returns null on failure
1081          */
1082         final public function getLocalReference( array $params ) {
1083                 $fsFiles = $this->getLocalReferenceMulti(
1084                         [ 'srcs' => [ $params['src'] ] ] + $params );
1085
1086                 return $fsFiles[$params['src']];
1087         }
1088
1089         /**
1090          * Like getLocalReference() except it takes an array of storage paths
1091          * and returns a map of storage paths to FSFile objects (or null on failure).
1092          * The map keys (paths) are in the same order as the provided list of paths.
1093          *
1094          * @see FileBackend::getLocalReference()
1095          *
1096          * @param array $params Parameters include:
1097          *   - srcs        : list of source storage paths
1098          *   - latest      : use the latest available data
1099          *   - parallelize : try to do operations in parallel when possible
1100          * @return array Map of (path name => FSFile or null on failure)
1101          * @since 1.20
1102          */
1103         abstract public function getLocalReferenceMulti( array $params );
1104
1105         /**
1106          * Get a local copy on disk of the file at a storage path in the backend.
1107          * The temporary copy will have the same file extension as the source.
1108          * Temporary files may be purged when the file object falls out of scope.
1109          *
1110          * @param array $params Parameters include:
1111          *   - src    : source storage path
1112          *   - latest : use the latest available data
1113          * @return TempFSFile|null Returns null on failure
1114          */
1115         final public function getLocalCopy( array $params ) {
1116                 $tmpFiles = $this->getLocalCopyMulti(
1117                         [ 'srcs' => [ $params['src'] ] ] + $params );
1118
1119                 return $tmpFiles[$params['src']];
1120         }
1121
1122         /**
1123          * Like getLocalCopy() except it takes an array of storage paths and
1124          * returns a map of storage paths to TempFSFile objects (or null on failure).
1125          * The map keys (paths) are in the same order as the provided list of paths.
1126          *
1127          * @see FileBackend::getLocalCopy()
1128          *
1129          * @param array $params Parameters include:
1130          *   - srcs        : list of source storage paths
1131          *   - latest      : use the latest available data
1132          *   - parallelize : try to do operations in parallel when possible
1133          * @return array Map of (path name => TempFSFile or null on failure)
1134          * @since 1.20
1135          */
1136         abstract public function getLocalCopyMulti( array $params );
1137
1138         /**
1139          * Return an HTTP URL to a given file that requires no authentication to use.
1140          * The URL may be pre-authenticated (via some token in the URL) and temporary.
1141          * This will return null if the backend cannot make an HTTP URL for the file.
1142          *
1143          * This is useful for key/value stores when using scripts that seek around
1144          * large files and those scripts (and the backend) support HTTP Range headers.
1145          * Otherwise, one would need to use getLocalReference(), which involves loading
1146          * the entire file on to local disk.
1147          *
1148          * @param array $params Parameters include:
1149          *   - src : source storage path
1150          *   - ttl : lifetime (seconds) if pre-authenticated; default is 1 day
1151          * @return string|null
1152          * @since 1.21
1153          */
1154         abstract public function getFileHttpUrl( array $params );
1155
1156         /**
1157          * Check if a directory exists at a given storage path.
1158          * Backends using key/value stores will check if the path is a
1159          * virtual directory, meaning there are files under the given directory.
1160          *
1161          * Storage backends with eventual consistency might return stale data.
1162          *
1163          * @param array $params Parameters include:
1164          *   - dir : storage directory
1165          * @return bool|null Returns null on failure
1166          * @since 1.20
1167          */
1168         abstract public function directoryExists( array $params );
1169
1170         /**
1171          * Get an iterator to list *all* directories under a storage directory.
1172          * If the directory is of the form "mwstore://backend/container",
1173          * then all directories in the container will be listed.
1174          * If the directory is of form "mwstore://backend/container/dir",
1175          * then all directories directly under that directory will be listed.
1176          * Results will be storage directories relative to the given directory.
1177          *
1178          * Storage backends with eventual consistency might return stale data.
1179          *
1180          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1181          *
1182          * @param array $params Parameters include:
1183          *   - dir     : storage directory
1184          *   - topOnly : only return direct child dirs of the directory
1185          * @return Traversable|array|null Returns null on failure
1186          * @since 1.20
1187          */
1188         abstract public function getDirectoryList( array $params );
1189
1190         /**
1191          * Same as FileBackend::getDirectoryList() except only lists
1192          * directories that are immediately under the given directory.
1193          *
1194          * Storage backends with eventual consistency might return stale data.
1195          *
1196          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1197          *
1198          * @param array $params Parameters include:
1199          *   - dir : storage directory
1200          * @return Traversable|array|null Returns null on failure
1201          * @since 1.20
1202          */
1203         final public function getTopDirectoryList( array $params ) {
1204                 return $this->getDirectoryList( [ 'topOnly' => true ] + $params );
1205         }
1206
1207         /**
1208          * Get an iterator to list *all* stored files under a storage directory.
1209          * If the directory is of the form "mwstore://backend/container",
1210          * then all files in the container will be listed.
1211          * If the directory is of form "mwstore://backend/container/dir",
1212          * then all files under that directory will be listed.
1213          * Results will be storage paths relative to the given directory.
1214          *
1215          * Storage backends with eventual consistency might return stale data.
1216          *
1217          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1218          *
1219          * @param array $params Parameters include:
1220          *   - dir        : storage directory
1221          *   - topOnly    : only return direct child files of the directory (since 1.20)
1222          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1223          * @return Traversable|array|null Returns null on failure
1224          */
1225         abstract public function getFileList( array $params );
1226
1227         /**
1228          * Same as FileBackend::getFileList() except only lists
1229          * files that are immediately under the given directory.
1230          *
1231          * Storage backends with eventual consistency might return stale data.
1232          *
1233          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1234          *
1235          * @param array $params Parameters include:
1236          *   - dir        : storage directory
1237          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1238          * @return Traversable|array|null Returns null on failure
1239          * @since 1.20
1240          */
1241         final public function getTopFileList( array $params ) {
1242                 return $this->getFileList( [ 'topOnly' => true ] + $params );
1243         }
1244
1245         /**
1246          * Preload persistent file stat cache and property cache into in-process cache.
1247          * This should be used when stat calls will be made on a known list of a many files.
1248          *
1249          * @see FileBackend::getFileStat()
1250          *
1251          * @param array $paths Storage paths
1252          */
1253         abstract public function preloadCache( array $paths );
1254
1255         /**
1256          * Invalidate any in-process file stat and property cache.
1257          * If $paths is given, then only the cache for those files will be cleared.
1258          *
1259          * @see FileBackend::getFileStat()
1260          *
1261          * @param array|null $paths Storage paths (optional)
1262          */
1263         abstract public function clearCache( array $paths = null );
1264
1265         /**
1266          * Preload file stat information (concurrently if possible) into in-process cache.
1267          *
1268          * This should be used when stat calls will be made on a known list of a many files.
1269          * This does not make use of the persistent file stat cache.
1270          *
1271          * @see FileBackend::getFileStat()
1272          *
1273          * @param array $params Parameters include:
1274          *   - srcs        : list of source storage paths
1275          *   - latest      : use the latest available data
1276          * @return bool All requests proceeded without I/O errors (since 1.24)
1277          * @since 1.23
1278          */
1279         abstract public function preloadFileStat( array $params );
1280
1281         /**
1282          * Lock the files at the given storage paths in the backend.
1283          * This will either lock all the files or none (on failure).
1284          *
1285          * Callers should consider using getScopedFileLocks() instead.
1286          *
1287          * @param array $paths Storage paths
1288          * @param int $type LockManager::LOCK_* constant
1289          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.24)
1290          * @return StatusValue
1291          */
1292         final public function lockFiles( array $paths, $type, $timeout = 0 ) {
1293                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1294
1295                 return $this->wrapStatus( $this->lockManager->lock( $paths, $type, $timeout ) );
1296         }
1297
1298         /**
1299          * Unlock the files at the given storage paths in the backend.
1300          *
1301          * @param array $paths Storage paths
1302          * @param int $type LockManager::LOCK_* constant
1303          * @return StatusValue
1304          */
1305         final public function unlockFiles( array $paths, $type ) {
1306                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1307
1308                 return $this->wrapStatus( $this->lockManager->unlock( $paths, $type ) );
1309         }
1310
1311         /**
1312          * Lock the files at the given storage paths in the backend.
1313          * This will either lock all the files or none (on failure).
1314          * On failure, the StatusValue object will be updated with errors.
1315          *
1316          * Once the return value goes out scope, the locks will be released and
1317          * the StatusValue updated. Unlock fatals will not change the StatusValue "OK" value.
1318          *
1319          * @see ScopedLock::factory()
1320          *
1321          * @param array $paths List of storage paths or map of lock types to path lists
1322          * @param int|string $type LockManager::LOCK_* constant or "mixed"
1323          * @param StatusValue $status StatusValue to update on lock/unlock
1324          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.24)
1325          * @return ScopedLock|null Returns null on failure
1326          */
1327         final public function getScopedFileLocks(
1328                 array $paths, $type, StatusValue $status, $timeout = 0
1329         ) {
1330                 if ( $type === 'mixed' ) {
1331                         foreach ( $paths as &$typePaths ) {
1332                                 $typePaths = array_map( 'FileBackend::normalizeStoragePath', $typePaths );
1333                         }
1334                 } else {
1335                         $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1336                 }
1337
1338                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status, $timeout );
1339         }
1340
1341         /**
1342          * Get an array of scoped locks needed for a batch of file operations.
1343          *
1344          * Normally, FileBackend::doOperations() handles locking, unless
1345          * the 'nonLocking' param is passed in. This function is useful if you
1346          * want the files to be locked for a broader scope than just when the
1347          * files are changing. For example, if you need to update DB metadata,
1348          * you may want to keep the files locked until finished.
1349          *
1350          * @see FileBackend::doOperations()
1351          *
1352          * @param array $ops List of file operations to FileBackend::doOperations()
1353          * @param StatusValue $status StatusValue to update on lock/unlock
1354          * @return ScopedLock|null
1355          * @since 1.20
1356          */
1357         abstract public function getScopedLocksForOps( array $ops, StatusValue $status );
1358
1359         /**
1360          * Get the root storage path of this backend.
1361          * All container paths are "subdirectories" of this path.
1362          *
1363          * @return string Storage path
1364          * @since 1.20
1365          */
1366         final public function getRootStoragePath() {
1367                 return "mwstore://{$this->name}";
1368         }
1369
1370         /**
1371          * Get the storage path for the given container for this backend
1372          *
1373          * @param string $container Container name
1374          * @return string Storage path
1375          * @since 1.21
1376          */
1377         final public function getContainerStoragePath( $container ) {
1378                 return $this->getRootStoragePath() . "/{$container}";
1379         }
1380
1381         /**
1382          * Get the file journal object for this backend
1383          *
1384          * @return FileJournal
1385          */
1386         final public function getJournal() {
1387                 return $this->fileJournal;
1388         }
1389
1390         /**
1391          * Convert FSFile 'src' paths to string paths (with an 'srcRef' field set to the FSFile)
1392          *
1393          * The 'srcRef' field keeps any TempFSFile objects in scope for the backend to have it
1394          * around as long it needs (which may vary greatly depending on configuration)
1395          *
1396          * @param array $ops File operation batch for FileBaclend::doOperations()
1397          * @return array File operation batch
1398          */
1399         protected function resolveFSFileObjects( array $ops ) {
1400                 foreach ( $ops as &$op ) {
1401                         $src = $op['src'] ?? null;
1402                         if ( $src instanceof FSFile ) {
1403                                 $op['srcRef'] = $src;
1404                                 $op['src'] = $src->getPath();
1405                         }
1406                 }
1407                 unset( $op );
1408
1409                 return $ops;
1410         }
1411
1412         /**
1413          * Check if a given path is a "mwstore://" path.
1414          * This does not do any further validation or any existence checks.
1415          *
1416          * @param string $path
1417          * @return bool
1418          */
1419         final public static function isStoragePath( $path ) {
1420                 return ( strpos( $path, 'mwstore://' ) === 0 );
1421         }
1422
1423         /**
1424          * Split a storage path into a backend name, a container name,
1425          * and a relative file path. The relative path may be the empty string.
1426          * This does not do any path normalization or traversal checks.
1427          *
1428          * @param string $storagePath
1429          * @return array (backend, container, rel object) or (null, null, null)
1430          */
1431         final public static function splitStoragePath( $storagePath ) {
1432                 if ( self::isStoragePath( $storagePath ) ) {
1433                         // Remove the "mwstore://" prefix and split the path
1434                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
1435                         if ( count( $parts ) >= 2 && $parts[0] != '' && $parts[1] != '' ) {
1436                                 if ( count( $parts ) == 3 ) {
1437                                         return $parts; // e.g. "backend/container/path"
1438                                 } else {
1439                                         return [ $parts[0], $parts[1], '' ]; // e.g. "backend/container"
1440                                 }
1441                         }
1442                 }
1443
1444                 return [ null, null, null ];
1445         }
1446
1447         /**
1448          * Normalize a storage path by cleaning up directory separators.
1449          * Returns null if the path is not of the format of a valid storage path.
1450          *
1451          * @param string $storagePath
1452          * @return string|null
1453          */
1454         final public static function normalizeStoragePath( $storagePath ) {
1455                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
1456                 if ( $relPath !== null ) { // must be for this backend
1457                         $relPath = self::normalizeContainerPath( $relPath );
1458                         if ( $relPath !== null ) {
1459                                 return ( $relPath != '' )
1460                                         ? "mwstore://{$backend}/{$container}/{$relPath}"
1461                                         : "mwstore://{$backend}/{$container}";
1462                         }
1463                 }
1464
1465                 return null;
1466         }
1467
1468         /**
1469          * Get the parent storage directory of a storage path.
1470          * This returns a path like "mwstore://backend/container",
1471          * "mwstore://backend/container/...", or null if there is no parent.
1472          *
1473          * @param string $storagePath
1474          * @return string|null
1475          */
1476         final public static function parentStoragePath( $storagePath ) {
1477                 $storagePath = dirname( $storagePath );
1478                 list( , , $rel ) = self::splitStoragePath( $storagePath );
1479
1480                 return ( $rel === null ) ? null : $storagePath;
1481         }
1482
1483         /**
1484          * Get the final extension from a storage or FS path
1485          *
1486          * @param string $path
1487          * @param string $case One of (rawcase, uppercase, lowercase) (since 1.24)
1488          * @return string
1489          */
1490         final public static function extensionFromPath( $path, $case = 'lowercase' ) {
1491                 $i = strrpos( $path, '.' );
1492                 $ext = $i ? substr( $path, $i + 1 ) : '';
1493
1494                 if ( $case === 'lowercase' ) {
1495                         $ext = strtolower( $ext );
1496                 } elseif ( $case === 'uppercase' ) {
1497                         $ext = strtoupper( $ext );
1498                 }
1499
1500                 return $ext;
1501         }
1502
1503         /**
1504          * Check if a relative path has no directory traversals
1505          *
1506          * @param string $path
1507          * @return bool
1508          * @since 1.20
1509          */
1510         final public static function isPathTraversalFree( $path ) {
1511                 return ( self::normalizeContainerPath( $path ) !== null );
1512         }
1513
1514         /**
1515          * Build a Content-Disposition header value per RFC 6266.
1516          *
1517          * @param string $type One of (attachment, inline)
1518          * @param string $filename Suggested file name (should not contain slashes)
1519          * @throws FileBackendError
1520          * @return string
1521          * @since 1.20
1522          */
1523         final public static function makeContentDisposition( $type, $filename = '' ) {
1524                 $parts = [];
1525
1526                 $type = strtolower( $type );
1527                 if ( !in_array( $type, [ 'inline', 'attachment' ] ) ) {
1528                         throw new InvalidArgumentException( "Invalid Content-Disposition type '$type'." );
1529                 }
1530                 $parts[] = $type;
1531
1532                 if ( strlen( $filename ) ) {
1533                         $parts[] = "filename*=UTF-8''" . rawurlencode( basename( $filename ) );
1534                 }
1535
1536                 return implode( ';', $parts );
1537         }
1538
1539         /**
1540          * Validate and normalize a relative storage path.
1541          * Null is returned if the path involves directory traversal.
1542          * Traversal is insecure for FS backends and broken for others.
1543          *
1544          * This uses the same traversal protection as Title::secureAndSplit().
1545          *
1546          * @param string $path Storage path relative to a container
1547          * @return string|null
1548          */
1549         final protected static function normalizeContainerPath( $path ) {
1550                 // Normalize directory separators
1551                 $path = strtr( $path, '\\', '/' );
1552                 // Collapse any consecutive directory separators
1553                 $path = preg_replace( '![/]{2,}!', '/', $path );
1554                 // Remove any leading directory separator
1555                 $path = ltrim( $path, '/' );
1556                 // Use the same traversal protection as Title::secureAndSplit()
1557                 if ( strpos( $path, '.' ) !== false ) {
1558                         if (
1559                                 $path === '.' ||
1560                                 $path === '..' ||
1561                                 strpos( $path, './' ) === 0 ||
1562                                 strpos( $path, '../' ) === 0 ||
1563                                 strpos( $path, '/./' ) !== false ||
1564                                 strpos( $path, '/../' ) !== false
1565                         ) {
1566                                 return null;
1567                         }
1568                 }
1569
1570                 return $path;
1571         }
1572
1573         /**
1574          * Yields the result of the status wrapper callback on either:
1575          *   - StatusValue::newGood() if this method is called without parameters
1576          *   - StatusValue::newFatal() with all parameters to this method if passed in
1577          *
1578          * @param string $args,...
1579          * @return StatusValue
1580          */
1581         final protected function newStatus() {
1582                 $args = func_get_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 }