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 object|string Class name or object With profileIn/profileOut methods */
 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 class name or object With profileIn/profileOut methods.
 160          * @throws InvalidArgumentException
 161          */
 162         public function __construct( array $config ) {
 163                 $this->name = $config['name'];
 164                 $this->domainId = isset( $config['domainId'] )
 165                         ? $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                 $this->logger = $config['logger'] ?? new \Psr\Log\NullLogger();
 191                 $this->statusWrapper = $config['statusWrapper'] ?? null;
 192                 $this->tmpDirectory = $config['tmpDirectory'] ?? null;
 193         }
 194
 195         public function setLogger( LoggerInterface $logger ) {
 196                 $this->logger = $logger;
 197         }
 198
 199         /**
 200          * Get the unique backend name.
 201          * We may have multiple different backends of the same type.
 202          * For example, we can have two Swift backends using different proxies.
 203          *
 204          * @return string
 205          */
 206         final public function getName() {
 207                 return $this->name;
 208         }
 209
 210         /**
 211          * Get the domain identifier used for this backend (possibly empty).
 212          *
 213          * @return string
 214          * @since 1.28
 215          */
 216         final public function getDomainId() {
 217                 return $this->domainId;
 218         }
 219
 220         /**
 221          * Alias to getDomainId()
 222          * @return string
 223          * @since 1.20
 224          */
 225         final public function getWikiId() {
 226                 return $this->getDomainId();
 227         }
 228
 229         /**
 230          * Check if this backend is read-only
 231          *
 232          * @return bool
 233          */
 234         final public function isReadOnly() {
 235                 return ( $this->readOnly != '' );
 236         }
 237
 238         /**
 239          * Get an explanatory message if this backend is read-only
 240          *
 241          * @return string|bool Returns false if the backend is not read-only
 242          */
 243         final public function getReadOnlyReason() {
 244                 return ( $this->readOnly != '' ) ? $this->readOnly : false;
 245         }
 246
 247         /**
 248          * Get the a bitfield of extra features supported by the backend medium
 249          *
 250          * @return int Bitfield of FileBackend::ATTR_* flags
 251          * @since 1.23
 252          */
 253         public function getFeatures() {
 254                 return self::ATTR_UNICODE_PATHS;
 255         }
 256
 257         /**
 258          * Check if the backend medium supports a field of extra features
 259          *
 260          * @param int $bitfield Bitfield of FileBackend::ATTR_* flags
 261          * @return bool
 262          * @since 1.23
 263          */
 264         final public function hasFeatures( $bitfield ) {
 265                 return ( $this->getFeatures() & $bitfield ) === $bitfield;
 266         }
 267
 268         /**
 269          * This is the main entry point into the backend for write operations.
 270          * Callers supply an ordered list of operations to perform as a transaction.
 271          * Files will be locked, the stat cache cleared, and then the operations attempted.
 272          * If any serious errors occur, all attempted operations will be rolled back.
 273          *
 274          * $ops is an array of arrays. The outer array holds a list of operations.
 275          * Each inner array is a set of key value pairs that specify an operation.
 276          *
 277          * Supported operations and their parameters. The supported actions are:
 278          *  - create
 279          *  - store
 280          *  - copy
 281          *  - move
 282          *  - delete
 283          *  - describe (since 1.21)
 284          *  - null
 285          *
 286          * FSFile/TempFSFile object support was added in 1.27.
 287          *
 288          * a) Create a new file in storage with the contents of a string
 289          * @code
 290          *     [
 291          *         'op'                  => 'create',
 292          *         'dst'                 => <storage path>,
 293          *         'content'             => <string of new file contents>,
 294          *         'overwrite'           => <boolean>,
 295          *         'overwriteSame'       => <boolean>,
 296          *         'headers'             => <HTTP header name/value map> # since 1.21
 297          *     ]
 298          * @endcode
 299          *
 300          * b) Copy a file system file into storage
 301          * @code
 302          *     [
 303          *         'op'                  => 'store',
 304          *         'src'                 => <file system path, FSFile, or TempFSFile>,
 305          *         'dst'                 => <storage path>,
 306          *         'overwrite'           => <boolean>,
 307          *         'overwriteSame'       => <boolean>,
 308          *         'headers'             => <HTTP header name/value map> # since 1.21
 309          *     ]
 310          * @endcode
 311          *
 312          * c) Copy a file within storage
 313          * @code
 314          *     [
 315          *         'op'                  => 'copy',
 316          *         'src'                 => <storage path>,
 317          *         'dst'                 => <storage path>,
 318          *         'overwrite'           => <boolean>,
 319          *         'overwriteSame'       => <boolean>,
 320          *         'ignoreMissingSource' => <boolean>, # since 1.21
 321          *         'headers'             => <HTTP header name/value map> # since 1.21
 322          *     ]
 323          * @endcode
 324          *
 325          * d) Move a file within storage
 326          * @code
 327          *     [
 328          *         'op'                  => 'move',
 329          *         'src'                 => <storage path>,
 330          *         'dst'                 => <storage path>,
 331          *         'overwrite'           => <boolean>,
 332          *         'overwriteSame'       => <boolean>,
 333          *         'ignoreMissingSource' => <boolean>, # since 1.21
 334          *         'headers'             => <HTTP header name/value map> # since 1.21
 335          *     ]
 336          * @endcode
 337          *
 338          * e) Delete a file within storage
 339          * @code
 340          *     [
 341          *         'op'                  => 'delete',
 342          *         'src'                 => <storage path>,
 343          *         'ignoreMissingSource' => <boolean>
 344          *     ]
 345          * @endcode
 346          *
 347          * f) Update metadata for a file within storage
 348          * @code
 349          *     [
 350          *         'op'                  => 'describe',
 351          *         'src'                 => <storage path>,
 352          *         'headers'             => <HTTP header name/value map>
 353          *     ]
 354          * @endcode
 355          *
 356          * g) Do nothing (no-op)
 357          * @code
 358          *     [
 359          *         'op'                  => 'null',
 360          *     ]
 361          * @endcode
 362          *
 363          * Boolean flags for operations (operation-specific):
 364          *   - ignoreMissingSource : The operation will simply succeed and do
 365          *                           nothing if the source file does not exist.
 366          *   - overwrite           : Any destination file will be overwritten.
 367          *   - overwriteSame       : If a file already exists at the destination with the
 368          *                           same contents, then do nothing to the destination file
 369          *                           instead of giving an error. This does not compare headers.
 370          *                           This option is ignored if 'overwrite' is already provided.
 371          *   - headers             : If supplied, the result of merging these headers with any
 372          *                           existing source file headers (replacing conflicting ones)
 373          *                           will be set as the destination file headers. Headers are
 374          *                           deleted if their value is set to the empty string. When a
 375          *                           file has headers they are included in responses to GET and
 376          *                           HEAD requests to the backing store for that file.
 377          *                           Header values should be no larger than 255 bytes, except for
 378          *                           Content-Disposition. The system might ignore or truncate any
 379          *                           headers that are too long to store (exact limits will vary).
 380          *                           Backends that don't support metadata ignore this. (since 1.21)
 381          *
 382          * $opts is an associative of boolean flags, including:
 383          *   - force               : Operation precondition errors no longer trigger an abort.
 384          *                           Any remaining operations are still attempted. Unexpected
 385          *                           failures may still cause remaining operations to be aborted.
 386          *   - nonLocking          : No locks are acquired for the operations.
 387          *                           This can increase performance for non-critical writes.
 388          *                           This has no effect unless the 'force' flag is set.
 389          *   - nonJournaled        : Don't log this operation batch in the file journal.
 390          *                           This limits the ability of recovery scripts.
 391          *   - parallelize         : Try to do operations in parallel when possible.
 392          *   - bypassReadOnly      : Allow writes in read-only mode. (since 1.20)
 393          *   - preserveCache       : Don't clear the process cache before checking files.
 394          *                           This should only be used if all entries in the process
 395          *                           cache were added after the files were already locked. (since 1.20)
 396          *
 397          * @note Remarks on locking:
 398          * File system paths given to operations should refer to files that are
 399          * already locked or otherwise safe from modification from other processes.
 400          * Normally these files will be new temp files, which should be adequate.
 401          *
 402          * @par Return value:
 403          *
 404          * This returns a Status, which contains all warnings and fatals that occurred
 405          * during the operation. The 'failCount', 'successCount', and 'success' members
 406          * will reflect each operation attempted.
 407          *
 408          * The StatusValue will be "OK" unless:
 409          *   - a) unexpected operation errors occurred (network partitions, disk full...)
 410          *   - b) significant operation errors occurred and 'force' was not set
 411          *
 412          * @param array $ops List of operations to execute in order
 413          * @param array $opts Batch operation options
 414          * @return StatusValue
 415          */
 416         final public function doOperations( array $ops, array $opts = [] ) {
 417                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 418                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 419                 }
 420                 if ( !count( $ops ) ) {
 421                         return $this->newStatus(); // nothing to do
 422                 }
 423
 424                 $ops = $this->resolveFSFileObjects( $ops );
 425                 if ( empty( $opts['force'] ) ) { // sanity
 426                         unset( $opts['nonLocking'] );
 427                 }
 428
 429                 /** @noinspection PhpUnusedLocalVariableInspection */
 430                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 431
 432                 return $this->doOperationsInternal( $ops, $opts );
 433         }
 434
 435         /**
 436          * @see FileBackend::doOperations()
 437          * @param array $ops
 438          * @param array $opts
 439          */
 440         abstract protected function doOperationsInternal( array $ops, array $opts );
 441
 442         /**
 443          * Same as doOperations() except it takes a single operation.
 444          * If you are doing a batch of operations that should either
 445          * all succeed or all fail, then use that function instead.
 446          *
 447          * @see FileBackend::doOperations()
 448          *
 449          * @param array $op Operation
 450          * @param array $opts Operation options
 451          * @return StatusValue
 452          */
 453         final public function doOperation( array $op, array $opts = [] ) {
 454                 return $this->doOperations( [ $op ], $opts );
 455         }
 456
 457         /**
 458          * Performs a single create operation.
 459          * This sets $params['op'] to 'create' and passes it to doOperation().
 460          *
 461          * @see FileBackend::doOperation()
 462          *
 463          * @param array $params Operation parameters
 464          * @param array $opts Operation options
 465          * @return StatusValue
 466          */
 467         final public function create( array $params, array $opts = [] ) {
 468                 return $this->doOperation( [ 'op' => 'create' ] + $params, $opts );
 469         }
 470
 471         /**
 472          * Performs a single store operation.
 473          * This sets $params['op'] to 'store' and passes it to doOperation().
 474          *
 475          * @see FileBackend::doOperation()
 476          *
 477          * @param array $params Operation parameters
 478          * @param array $opts Operation options
 479          * @return StatusValue
 480          */
 481         final public function store( array $params, array $opts = [] ) {
 482                 return $this->doOperation( [ 'op' => 'store' ] + $params, $opts );
 483         }
 484
 485         /**
 486          * Performs a single copy operation.
 487          * This sets $params['op'] to 'copy' and passes it to doOperation().
 488          *
 489          * @see FileBackend::doOperation()
 490          *
 491          * @param array $params Operation parameters
 492          * @param array $opts Operation options
 493          * @return StatusValue
 494          */
 495         final public function copy( array $params, array $opts = [] ) {
 496                 return $this->doOperation( [ 'op' => 'copy' ] + $params, $opts );
 497         }
 498
 499         /**
 500          * Performs a single move operation.
 501          * This sets $params['op'] to 'move' and passes it to doOperation().
 502          *
 503          * @see FileBackend::doOperation()
 504          *
 505          * @param array $params Operation parameters
 506          * @param array $opts Operation options
 507          * @return StatusValue
 508          */
 509         final public function move( array $params, array $opts = [] ) {
 510                 return $this->doOperation( [ 'op' => 'move' ] + $params, $opts );
 511         }
 512
 513         /**
 514          * Performs a single delete operation.
 515          * This sets $params['op'] to 'delete' and passes it to doOperation().
 516          *
 517          * @see FileBackend::doOperation()
 518          *
 519          * @param array $params Operation parameters
 520          * @param array $opts Operation options
 521          * @return StatusValue
 522          */
 523         final public function delete( array $params, array $opts = [] ) {
 524                 return $this->doOperation( [ 'op' => 'delete' ] + $params, $opts );
 525         }
 526
 527         /**
 528          * Performs a single describe operation.
 529          * This sets $params['op'] to 'describe' and passes it to doOperation().
 530          *
 531          * @see FileBackend::doOperation()
 532          *
 533          * @param array $params Operation parameters
 534          * @param array $opts Operation options
 535          * @return StatusValue
 536          * @since 1.21
 537          */
 538         final public function describe( array $params, array $opts = [] ) {
 539                 return $this->doOperation( [ 'op' => 'describe' ] + $params, $opts );
 540         }
 541
 542         /**
 543          * Perform a set of independent file operations on some files.
 544          *
 545          * This does no locking, nor journaling, and possibly no stat calls.
 546          * Any destination files that already exist will be overwritten.
 547          * This should *only* be used on non-original files, like cache files.
 548          *
 549          * Supported operations and their parameters:
 550          *  - create
 551          *  - store
 552          *  - copy
 553          *  - move
 554          *  - delete
 555          *  - describe (since 1.21)
 556          *  - null
 557          *
 558          * FSFile/TempFSFile object support was added in 1.27.
 559          *
 560          * a) Create a new file in storage with the contents of a string
 561          * @code
 562          *     [
 563          *         'op'                  => 'create',
 564          *         'dst'                 => <storage path>,
 565          *         'content'             => <string of new file contents>,
 566          *         'headers'             => <HTTP header name/value map> # since 1.21
 567          *     ]
 568          * @endcode
 569          *
 570          * b) Copy a file system file into storage
 571          * @code
 572          *     [
 573          *         'op'                  => 'store',
 574          *         'src'                 => <file system path, FSFile, or TempFSFile>,
 575          *         'dst'                 => <storage path>,
 576          *         'headers'             => <HTTP header name/value map> # since 1.21
 577          *     ]
 578          * @endcode
 579          *
 580          * c) Copy a file within storage
 581          * @code
 582          *     [
 583          *         'op'                  => 'copy',
 584          *         'src'                 => <storage path>,
 585          *         'dst'                 => <storage path>,
 586          *         'ignoreMissingSource' => <boolean>, # since 1.21
 587          *         'headers'             => <HTTP header name/value map> # since 1.21
 588          *     ]
 589          * @endcode
 590          *
 591          * d) Move a file within storage
 592          * @code
 593          *     [
 594          *         'op'                  => 'move',
 595          *         'src'                 => <storage path>,
 596          *         'dst'                 => <storage path>,
 597          *         'ignoreMissingSource' => <boolean>, # since 1.21
 598          *         'headers'             => <HTTP header name/value map> # since 1.21
 599          *     ]
 600          * @endcode
 601          *
 602          * e) Delete a file within storage
 603          * @code
 604          *     [
 605          *         'op'                  => 'delete',
 606          *         'src'                 => <storage path>,
 607          *         'ignoreMissingSource' => <boolean>
 608          *     ]
 609          * @endcode
 610          *
 611          * f) Update metadata for a file within storage
 612          * @code
 613          *     [
 614          *         'op'                  => 'describe',
 615          *         'src'                 => <storage path>,
 616          *         'headers'             => <HTTP header name/value map>
 617          *     ]
 618          * @endcode
 619          *
 620          * g) Do nothing (no-op)
 621          * @code
 622          *     [
 623          *         'op'                  => 'null',
 624          *     ]
 625          * @endcode
 626          *
 627          * @par Boolean flags for operations (operation-specific):
 628          *   - ignoreMissingSource : The operation will simply succeed and do
 629          *                           nothing if the source file does not exist.
 630          *   - headers             : If supplied with a header name/value map, the backend will
 631          *                           reply with these headers when GETs/HEADs of the destination
 632          *                           file are made. Header values should be smaller than 256 bytes.
 633          *                           Content-Disposition headers can be longer, though the system
 634          *                           might ignore or truncate ones that are too long to store.
 635          *                           Existing headers will remain, but these will replace any
 636          *                           conflicting previous headers, and headers will be removed
 637          *                           if they are set to an empty string.
 638          *                           Backends that don't support metadata ignore this. (since 1.21)
 639          *
 640          * $opts is an associative of boolean flags, including:
 641          *   - bypassReadOnly      : Allow writes in read-only mode (since 1.20)
 642          *
 643          * @par Return value:
 644          * This returns a Status, which contains all warnings and fatals that occurred
 645          * during the operation. The 'failCount', 'successCount', and 'success' members
 646          * will reflect each operation attempted for the given files. The StatusValue will be
 647          * considered "OK" as long as no fatal errors occurred.
 648          *
 649          * @param array $ops Set of operations to execute
 650          * @param array $opts Batch operation options
 651          * @return StatusValue
 652          * @since 1.20
 653          */
 654         final public function doQuickOperations( array $ops, array $opts = [] ) {
 655                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 656                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 657                 }
 658                 if ( !count( $ops ) ) {
 659                         return $this->newStatus(); // nothing to do
 660                 }
 661
 662                 $ops = $this->resolveFSFileObjects( $ops );
 663                 foreach ( $ops as &$op ) {
 664                         $op['overwrite'] = true; // avoids RTTs in key/value stores
 665                 }
 666
 667                 /** @noinspection PhpUnusedLocalVariableInspection */
 668                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 669
 670                 return $this->doQuickOperationsInternal( $ops );
 671         }
 672
 673         /**
 674          * @see FileBackend::doQuickOperations()
 675          * @param array $ops
 676          * @since 1.20
 677          */
 678         abstract protected function doQuickOperationsInternal( array $ops );
 679
 680         /**
 681          * Same as doQuickOperations() except it takes a single operation.
 682          * If you are doing a batch of operations, then use that function instead.
 683          *
 684          * @see FileBackend::doQuickOperations()
 685          *
 686          * @param array $op Operation
 687          * @return StatusValue
 688          * @since 1.20
 689          */
 690         final public function doQuickOperation( array $op ) {
 691                 return $this->doQuickOperations( [ $op ] );
 692         }
 693
 694         /**
 695          * Performs a single quick create operation.
 696          * This sets $params['op'] to 'create' and passes it to doQuickOperation().
 697          *
 698          * @see FileBackend::doQuickOperation()
 699          *
 700          * @param array $params Operation parameters
 701          * @return StatusValue
 702          * @since 1.20
 703          */
 704         final public function quickCreate( array $params ) {
 705                 return $this->doQuickOperation( [ 'op' => 'create' ] + $params );
 706         }
 707
 708         /**
 709          * Performs a single quick store operation.
 710          * This sets $params['op'] to 'store' and passes it to doQuickOperation().
 711          *
 712          * @see FileBackend::doQuickOperation()
 713          *
 714          * @param array $params Operation parameters
 715          * @return StatusValue
 716          * @since 1.20
 717          */
 718         final public function quickStore( array $params ) {
 719                 return $this->doQuickOperation( [ 'op' => 'store' ] + $params );
 720         }
 721
 722         /**
 723          * Performs a single quick copy operation.
 724          * This sets $params['op'] to 'copy' and passes it to doQuickOperation().
 725          *
 726          * @see FileBackend::doQuickOperation()
 727          *
 728          * @param array $params Operation parameters
 729          * @return StatusValue
 730          * @since 1.20
 731          */
 732         final public function quickCopy( array $params ) {
 733                 return $this->doQuickOperation( [ 'op' => 'copy' ] + $params );
 734         }
 735
 736         /**
 737          * Performs a single quick move operation.
 738          * This sets $params['op'] to 'move' and passes it to doQuickOperation().
 739          *
 740          * @see FileBackend::doQuickOperation()
 741          *
 742          * @param array $params Operation parameters
 743          * @return StatusValue
 744          * @since 1.20
 745          */
 746         final public function quickMove( array $params ) {
 747                 return $this->doQuickOperation( [ 'op' => 'move' ] + $params );
 748         }
 749
 750         /**
 751          * Performs a single quick delete operation.
 752          * This sets $params['op'] to 'delete' and passes it to doQuickOperation().
 753          *
 754          * @see FileBackend::doQuickOperation()
 755          *
 756          * @param array $params Operation parameters
 757          * @return StatusValue
 758          * @since 1.20
 759          */
 760         final public function quickDelete( array $params ) {
 761                 return $this->doQuickOperation( [ 'op' => 'delete' ] + $params );
 762         }
 763
 764         /**
 765          * Performs a single quick describe operation.
 766          * This sets $params['op'] to 'describe' and passes it to doQuickOperation().
 767          *
 768          * @see FileBackend::doQuickOperation()
 769          *
 770          * @param array $params Operation parameters
 771          * @return StatusValue
 772          * @since 1.21
 773          */
 774         final public function quickDescribe( array $params ) {
 775                 return $this->doQuickOperation( [ 'op' => 'describe' ] + $params );
 776         }
 777
 778         /**
 779          * Concatenate a list of storage files into a single file system file.
 780          * The target path should refer to a file that is already locked or
 781          * otherwise safe from modification from other processes. Normally,
 782          * the file will be a new temp file, which should be adequate.
 783          *
 784          * @param array $params Operation parameters, include:
 785          *   - srcs        : ordered source storage paths (e.g. chunk1, chunk2, ...)
 786          *   - dst         : file system path to 0-byte temp file
 787          *   - parallelize : try to do operations in parallel when possible
 788          * @return StatusValue
 789          */
 790         abstract public function concatenate( array $params );
 791
 792         /**
 793          * Prepare a storage directory for usage.
 794          * This will create any required containers and parent directories.
 795          * Backends using key/value stores only need to create the container.
 796          *
 797          * The 'noAccess' and 'noListing' parameters works the same as in secure(),
 798          * except they are only applied *if* the directory/container had to be created.
 799          * These flags should always be set for directories that have private files.
 800          * However, setting them is not guaranteed to actually do anything.
 801          * Additional server configuration may be needed to achieve the desired effect.
 802          *
 803          * @param array $params Parameters include:
 804          *   - dir            : storage directory
 805          *   - noAccess       : try to deny file access (since 1.20)
 806          *   - noListing      : try to deny file listing (since 1.20)
 807          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 808          * @return StatusValue
 809          */
 810         final public function prepare( array $params ) {
 811                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 812                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 813                 }
 814                 /** @noinspection PhpUnusedLocalVariableInspection */
 815                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 816                 return $this->doPrepare( $params );
 817         }
 818
 819         /**
 820          * @see FileBackend::prepare()
 821          * @param array $params
 822          */
 823         abstract protected function doPrepare( array $params );
 824
 825         /**
 826          * Take measures to block web access to a storage directory and
 827          * the container it belongs to. FS backends might add .htaccess
 828          * files whereas key/value store backends might revoke container
 829          * access to the storage user representing end-users in web requests.
 830          *
 831          * This is not guaranteed to actually make files or listings publically hidden.
 832          * Additional server configuration may be needed to achieve the desired effect.
 833          *
 834          * @param array $params Parameters include:
 835          *   - dir            : storage directory
 836          *   - noAccess       : try to deny file access
 837          *   - noListing      : try to deny file listing
 838          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 839          * @return StatusValue
 840          */
 841         final public function secure( array $params ) {
 842                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 843                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 844                 }
 845                 /** @noinspection PhpUnusedLocalVariableInspection */
 846                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 847                 return $this->doSecure( $params );
 848         }
 849
 850         /**
 851          * @see FileBackend::secure()
 852          * @param array $params
 853          */
 854         abstract protected function doSecure( array $params );
 855
 856         /**
 857          * Remove measures to block web access to a storage directory and
 858          * the container it belongs to. FS backends might remove .htaccess
 859          * files whereas key/value store backends might grant container
 860          * access to the storage user representing end-users in web requests.
 861          * This essentially can undo the result of secure() calls.
 862          *
 863          * This is not guaranteed to actually make files or listings publically viewable.
 864          * Additional server configuration may be needed to achieve the desired effect.
 865          *
 866          * @param array $params Parameters include:
 867          *   - dir            : storage directory
 868          *   - access         : try to allow file access
 869          *   - listing        : try to allow file listing
 870          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 871          * @return StatusValue
 872          * @since 1.20
 873          */
 874         final public function publish( array $params ) {
 875                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 876                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 877                 }
 878                 /** @noinspection PhpUnusedLocalVariableInspection */
 879                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 880                 return $this->doPublish( $params );
 881         }
 882
 883         /**
 884          * @see FileBackend::publish()
 885          * @param array $params
 886          */
 887         abstract protected function doPublish( array $params );
 888
 889         /**
 890          * Delete a storage directory if it is empty.
 891          * Backends using key/value stores may do nothing unless the directory
 892          * is that of an empty container, in which case it will be deleted.
 893          *
 894          * @param array $params Parameters include:
 895          *   - dir            : storage directory
 896          *   - recursive      : recursively delete empty subdirectories first (since 1.20)
 897          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 898          * @return StatusValue
 899          */
 900         final public function clean( array $params ) {
 901                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 902                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 903                 }
 904                 /** @noinspection PhpUnusedLocalVariableInspection */
 905                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 906                 return $this->doClean( $params );
 907         }
 908
 909         /**
 910          * @see FileBackend::clean()
 911          * @param array $params
 912          */
 913         abstract protected function doClean( array $params );
 914
 915         /**
 916          * Check if a file exists at a storage path in the backend.
 917          * This returns false if only a directory exists at the path.
 918          *
 919          * @param array $params Parameters include:
 920          *   - src    : source storage path
 921          *   - latest : use the latest available data
 922          * @return bool|null Returns null on failure
 923          */
 924         abstract public function fileExists( array $params );
 925
 926         /**
 927          * Get the last-modified timestamp of the file at a storage path.
 928          *
 929          * @param array $params Parameters include:
 930          *   - src    : source storage path
 931          *   - latest : use the latest available data
 932          * @return string|bool TS_MW timestamp or false on failure
 933          */
 934         abstract public function getFileTimestamp( array $params );
 935
 936         /**
 937          * Get the contents of a file at a storage path in the backend.
 938          * This should be avoided for potentially large files.
 939          *
 940          * @param array $params Parameters include:
 941          *   - src    : source storage path
 942          *   - latest : use the latest available data
 943          * @return string|bool Returns false on failure
 944          */
 945         final public function getFileContents( array $params ) {
 946                 $contents = $this->getFileContentsMulti(
 947                         [ 'srcs' => [ $params['src'] ] ] + $params );
 948
 949                 return $contents[$params['src']];
 950         }
 951
 952         /**
 953          * Like getFileContents() except it takes an array of storage paths
 954          * and returns a map of storage paths to strings (or null on failure).
 955          * The map keys (paths) are in the same order as the provided list of paths.
 956          *
 957          * @see FileBackend::getFileContents()
 958          *
 959          * @param array $params Parameters include:
 960          *   - srcs        : list of source storage paths
 961          *   - latest      : use the latest available data
 962          *   - parallelize : try to do operations in parallel when possible
 963          * @return array Map of (path name => string or false on failure)
 964          * @since 1.20
 965          */
 966         abstract public function getFileContentsMulti( array $params );
 967
 968         /**
 969          * Get metadata about a file at a storage path in the backend.
 970          * If the file does not exist, then this returns false.
 971          * Otherwise, the result is an associative array that includes:
 972          *   - headers  : map of HTTP headers used for GET/HEAD requests (name => value)
 973          *   - metadata : map of file metadata (name => value)
 974          * Metadata keys and headers names will be returned in all lower-case.
 975          * Additional values may be included for internal use only.
 976          *
 977          * Use FileBackend::hasFeatures() to check how well this is supported.
 978          *
 979          * @param array $params
 980          * $params include:
 981          *   - src    : source storage path
 982          *   - latest : use the latest available data
 983          * @return array|bool Returns false on failure
 984          * @since 1.23
 985          */
 986         abstract public function getFileXAttributes( array $params );
 987
 988         /**
 989          * Get the size (bytes) of a file at a storage path in the backend.
 990          *
 991          * @param array $params Parameters include:
 992          *   - src    : source storage path
 993          *   - latest : use the latest available data
 994          * @return int|bool Returns false on failure
 995          */
 996         abstract public function getFileSize( array $params );
 997
 998         /**
 999          * Get quick information about a file at a storage path in the backend.
1000          * If the file does not exist, then this returns false.
1001          * Otherwise, the result is an associative array that includes:
1002          *   - mtime  : the last-modified timestamp (TS_MW)
1003          *   - size   : the file size (bytes)
1004          * Additional values may be included for internal use only.
1005          *
1006          * @param array $params Parameters include:
1007          *   - src    : source storage path
1008          *   - latest : use the latest available data
1009          * @return array|bool|null Returns null on failure
1010          */
1011         abstract public function getFileStat( array $params );
1012
1013         /**
1014          * Get a SHA-1 hash of the file at a storage path in the backend.
1015          *
1016          * @param array $params Parameters include:
1017          *   - src    : source storage path
1018          *   - latest : use the latest available data
1019          * @return string|bool Hash string or false on failure
1020          */
1021         abstract public function getFileSha1Base36( array $params );
1022
1023         /**
1024          * Get the properties of the file at a storage path in the backend.
1025          * This gives the result of FSFile::getProps() on a local copy of the file.
1026          *
1027          * @param array $params Parameters include:
1028          *   - src    : source storage path
1029          *   - latest : use the latest available data
1030          * @return array Returns FSFile::placeholderProps() on failure
1031          */
1032         abstract public function getFileProps( array $params );
1033
1034         /**
1035          * Stream the file at a storage path in the backend.
1036          *
1037          * If the file does not exists, an HTTP 404 error will be given.
1038          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
1039          * will be sent if streaming began, while none will be sent otherwise.
1040          * Implementations should flush the output buffer before sending data.
1041          *
1042          * @param array $params Parameters include:
1043          *   - src      : source storage path
1044          *   - headers  : list of additional HTTP headers to send if the file exists
1045          *   - options  : HTTP request header map with lower case keys (since 1.28). Supports:
1046          *                range             : format is "bytes=(\d*-\d*)"
1047          *                if-modified-since : format is an HTTP date
1048          *   - headless : only include the body (and headers from "headers") (since 1.28)
1049          *   - latest   : use the latest available data
1050          *   - allowOB  : preserve any output buffers (since 1.28)
1051          * @return StatusValue
1052          */
1053         abstract public function streamFile( array $params );
1054
1055         /**
1056          * Returns a file system file, identical to the file at a storage path.
1057          * The file returned is either:
1058          *   - a) A local copy of the file at a storage path in the backend.
1059          *        The temporary copy will have the same extension as the source.
1060          *   - b) An original of the file at a storage path in the backend.
1061          * Temporary files may be purged when the file object falls out of scope.
1062          *
1063          * Write operations should *never* be done on this file as some backends
1064          * may do internal tracking or may be instances of FileBackendMultiWrite.
1065          * In that latter case, there are copies of the file that must stay in sync.
1066          * Additionally, further calls to this function may return the same file.
1067          *
1068          * @param array $params Parameters include:
1069          *   - src    : source storage path
1070          *   - latest : use the latest available data
1071          * @return FSFile|null Returns null on failure
1072          */
1073         final public function getLocalReference( array $params ) {
1074                 $fsFiles = $this->getLocalReferenceMulti(
1075                         [ 'srcs' => [ $params['src'] ] ] + $params );
1076
1077                 return $fsFiles[$params['src']];
1078         }
1079
1080         /**
1081          * Like getLocalReference() except it takes an array of storage paths
1082          * and returns a map of storage paths to FSFile objects (or null on failure).
1083          * The map keys (paths) are in the same order as the provided list of paths.
1084          *
1085          * @see FileBackend::getLocalReference()
1086          *
1087          * @param array $params Parameters include:
1088          *   - srcs        : list of source storage paths
1089          *   - latest      : use the latest available data
1090          *   - parallelize : try to do operations in parallel when possible
1091          * @return array Map of (path name => FSFile or null on failure)
1092          * @since 1.20
1093          */
1094         abstract public function getLocalReferenceMulti( array $params );
1095
1096         /**
1097          * Get a local copy on disk of the file at a storage path in the backend.
1098          * The temporary copy will have the same file extension as the source.
1099          * Temporary files may be purged when the file object falls out of scope.
1100          *
1101          * @param array $params Parameters include:
1102          *   - src    : source storage path
1103          *   - latest : use the latest available data
1104          * @return TempFSFile|null Returns null on failure
1105          */
1106         final public function getLocalCopy( array $params ) {
1107                 $tmpFiles = $this->getLocalCopyMulti(
1108                         [ 'srcs' => [ $params['src'] ] ] + $params );
1109
1110                 return $tmpFiles[$params['src']];
1111         }
1112
1113         /**
1114          * Like getLocalCopy() except it takes an array of storage paths and
1115          * returns a map of storage paths to TempFSFile objects (or null on failure).
1116          * The map keys (paths) are in the same order as the provided list of paths.
1117          *
1118          * @see FileBackend::getLocalCopy()
1119          *
1120          * @param array $params Parameters include:
1121          *   - srcs        : list of source storage paths
1122          *   - latest      : use the latest available data
1123          *   - parallelize : try to do operations in parallel when possible
1124          * @return array Map of (path name => TempFSFile or null on failure)
1125          * @since 1.20
1126          */
1127         abstract public function getLocalCopyMulti( array $params );
1128
1129         /**
1130          * Return an HTTP URL to a given file that requires no authentication to use.
1131          * The URL may be pre-authenticated (via some token in the URL) and temporary.
1132          * This will return null if the backend cannot make an HTTP URL for the file.
1133          *
1134          * This is useful for key/value stores when using scripts that seek around
1135          * large files and those scripts (and the backend) support HTTP Range headers.
1136          * Otherwise, one would need to use getLocalReference(), which involves loading
1137          * the entire file on to local disk.
1138          *
1139          * @param array $params Parameters include:
1140          *   - src : source storage path
1141          *   - ttl : lifetime (seconds) if pre-authenticated; default is 1 day
1142          * @return string|null
1143          * @since 1.21
1144          */
1145         abstract public function getFileHttpUrl( array $params );
1146
1147         /**
1148          * Check if a directory exists at a given storage path.
1149          * Backends using key/value stores will check if the path is a
1150          * virtual directory, meaning there are files under the given directory.
1151          *
1152          * Storage backends with eventual consistency might return stale data.
1153          *
1154          * @param array $params Parameters include:
1155          *   - dir : storage directory
1156          * @return bool|null Returns null on failure
1157          * @since 1.20
1158          */
1159         abstract public function directoryExists( array $params );
1160
1161         /**
1162          * Get an iterator to list *all* directories under a storage directory.
1163          * If the directory is of the form "mwstore://backend/container",
1164          * then all directories in the container will be listed.
1165          * If the directory is of form "mwstore://backend/container/dir",
1166          * then all directories directly under that directory will be listed.
1167          * Results will be storage directories relative to the given directory.
1168          *
1169          * Storage backends with eventual consistency might return stale data.
1170          *
1171          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1172          *
1173          * @param array $params Parameters include:
1174          *   - dir     : storage directory
1175          *   - topOnly : only return direct child dirs of the directory
1176          * @return Traversable|array|null Returns null on failure
1177          * @since 1.20
1178          */
1179         abstract public function getDirectoryList( array $params );
1180
1181         /**
1182          * Same as FileBackend::getDirectoryList() except only lists
1183          * directories that are immediately under the given directory.
1184          *
1185          * Storage backends with eventual consistency might return stale data.
1186          *
1187          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1188          *
1189          * @param array $params Parameters include:
1190          *   - dir : storage directory
1191          * @return Traversable|array|null Returns null on failure
1192          * @since 1.20
1193          */
1194         final public function getTopDirectoryList( array $params ) {
1195                 return $this->getDirectoryList( [ 'topOnly' => true ] + $params );
1196         }
1197
1198         /**
1199          * Get an iterator to list *all* stored files under a storage directory.
1200          * If the directory is of the form "mwstore://backend/container",
1201          * then all files in the container will be listed.
1202          * If the directory is of form "mwstore://backend/container/dir",
1203          * then all files under that directory will be listed.
1204          * Results will be storage paths relative to the given directory.
1205          *
1206          * Storage backends with eventual consistency might return stale data.
1207          *
1208          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1209          *
1210          * @param array $params Parameters include:
1211          *   - dir        : storage directory
1212          *   - topOnly    : only return direct child files of the directory (since 1.20)
1213          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1214          * @return Traversable|array|null Returns null on failure
1215          */
1216         abstract public function getFileList( array $params );
1217
1218         /**
1219          * Same as FileBackend::getFileList() except only lists
1220          * files that are immediately under the given directory.
1221          *
1222          * Storage backends with eventual consistency might return stale data.
1223          *
1224          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1225          *
1226          * @param array $params Parameters include:
1227          *   - dir        : storage directory
1228          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1229          * @return Traversable|array|null Returns null on failure
1230          * @since 1.20
1231          */
1232         final public function getTopFileList( array $params ) {
1233                 return $this->getFileList( [ 'topOnly' => true ] + $params );
1234         }
1235
1236         /**
1237          * Preload persistent file stat cache and property cache into in-process cache.
1238          * This should be used when stat calls will be made on a known list of a many files.
1239          *
1240          * @see FileBackend::getFileStat()
1241          *
1242          * @param array $paths Storage paths
1243          */
1244         abstract public function preloadCache( array $paths );
1245
1246         /**
1247          * Invalidate any in-process file stat and property cache.
1248          * If $paths is given, then only the cache for those files will be cleared.
1249          *
1250          * @see FileBackend::getFileStat()
1251          *
1252          * @param array|null $paths Storage paths (optional)
1253          */
1254         abstract public function clearCache( array $paths = null );
1255
1256         /**
1257          * Preload file stat information (concurrently if possible) into in-process cache.
1258          *
1259          * This should be used when stat calls will be made on a known list of a many files.
1260          * This does not make use of the persistent file stat cache.
1261          *
1262          * @see FileBackend::getFileStat()
1263          *
1264          * @param array $params Parameters include:
1265          *   - srcs        : list of source storage paths
1266          *   - latest      : use the latest available data
1267          * @return bool All requests proceeded without I/O errors (since 1.24)
1268          * @since 1.23
1269          */
1270         abstract public function preloadFileStat( array $params );
1271
1272         /**
1273          * Lock the files at the given storage paths in the backend.
1274          * This will either lock all the files or none (on failure).
1275          *
1276          * Callers should consider using getScopedFileLocks() instead.
1277          *
1278          * @param array $paths Storage paths
1279          * @param int $type LockManager::LOCK_* constant
1280          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.24)
1281          * @return StatusValue
1282          */
1283         final public function lockFiles( array $paths, $type, $timeout = 0 ) {
1284                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1285
1286                 return $this->wrapStatus( $this->lockManager->lock( $paths, $type, $timeout ) );
1287         }
1288
1289         /**
1290          * Unlock the files at the given storage paths in the backend.
1291          *
1292          * @param array $paths Storage paths
1293          * @param int $type LockManager::LOCK_* constant
1294          * @return StatusValue
1295          */
1296         final public function unlockFiles( array $paths, $type ) {
1297                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1298
1299                 return $this->wrapStatus( $this->lockManager->unlock( $paths, $type ) );
1300         }
1301
1302         /**
1303          * Lock the files at the given storage paths in the backend.
1304          * This will either lock all the files or none (on failure).
1305          * On failure, the StatusValue object will be updated with errors.
1306          *
1307          * Once the return value goes out scope, the locks will be released and
1308          * the StatusValue updated. Unlock fatals will not change the StatusValue "OK" value.
1309          *
1310          * @see ScopedLock::factory()
1311          *
1312          * @param array $paths List of storage paths or map of lock types to path lists
1313          * @param int|string $type LockManager::LOCK_* constant or "mixed"
1314          * @param StatusValue $status StatusValue to update on lock/unlock
1315          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.24)
1316          * @return ScopedLock|null Returns null on failure
1317          */
1318         final public function getScopedFileLocks(
1319                 array $paths, $type, StatusValue $status, $timeout = 0
1320         ) {
1321                 if ( $type === 'mixed' ) {
1322                         foreach ( $paths as &$typePaths ) {
1323                                 $typePaths = array_map( 'FileBackend::normalizeStoragePath', $typePaths );
1324                         }
1325                 } else {
1326                         $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1327                 }
1328
1329                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status, $timeout );
1330         }
1331
1332         /**
1333          * Get an array of scoped locks needed for a batch of file operations.
1334          *
1335          * Normally, FileBackend::doOperations() handles locking, unless
1336          * the 'nonLocking' param is passed in. This function is useful if you
1337          * want the files to be locked for a broader scope than just when the
1338          * files are changing. For example, if you need to update DB metadata,
1339          * you may want to keep the files locked until finished.
1340          *
1341          * @see FileBackend::doOperations()
1342          *
1343          * @param array $ops List of file operations to FileBackend::doOperations()
1344          * @param StatusValue $status StatusValue to update on lock/unlock
1345          * @return ScopedLock|null
1346          * @since 1.20
1347          */
1348         abstract public function getScopedLocksForOps( array $ops, StatusValue $status );
1349
1350         /**
1351          * Get the root storage path of this backend.
1352          * All container paths are "subdirectories" of this path.
1353          *
1354          * @return string Storage path
1355          * @since 1.20
1356          */
1357         final public function getRootStoragePath() {
1358                 return "mwstore://{$this->name}";
1359         }
1360
1361         /**
1362          * Get the storage path for the given container for this backend
1363          *
1364          * @param string $container Container name
1365          * @return string Storage path
1366          * @since 1.21
1367          */
1368         final public function getContainerStoragePath( $container ) {
1369                 return $this->getRootStoragePath() . "/{$container}";
1370         }
1371
1372         /**
1373          * Get the file journal object for this backend
1374          *
1375          * @return FileJournal
1376          */
1377         final public function getJournal() {
1378                 return $this->fileJournal;
1379         }
1380
1381         /**
1382          * Convert FSFile 'src' paths to string paths (with an 'srcRef' field set to the FSFile)
1383          *
1384          * The 'srcRef' field keeps any TempFSFile objects in scope for the backend to have it
1385          * around as long it needs (which may vary greatly depending on configuration)
1386          *
1387          * @param array $ops File operation batch for FileBaclend::doOperations()
1388          * @return array File operation batch
1389          */
1390         protected function resolveFSFileObjects( array $ops ) {
1391                 foreach ( $ops as &$op ) {
1392                         $src = $op['src'] ?? null;
1393                         if ( $src instanceof FSFile ) {
1394                                 $op['srcRef'] = $src;
1395                                 $op['src'] = $src->getPath();
1396                         }
1397                 }
1398                 unset( $op );
1399
1400                 return $ops;
1401         }
1402
1403         /**
1404          * Check if a given path is a "mwstore://" path.
1405          * This does not do any further validation or any existence checks.
1406          *
1407          * @param string $path
1408          * @return bool
1409          */
1410         final public static function isStoragePath( $path ) {
1411                 return ( strpos( $path, 'mwstore://' ) === 0 );
1412         }
1413
1414         /**
1415          * Split a storage path into a backend name, a container name,
1416          * and a relative file path. The relative path may be the empty string.
1417          * This does not do any path normalization or traversal checks.
1418          *
1419          * @param string $storagePath
1420          * @return array (backend, container, rel object) or (null, null, null)
1421          */
1422         final public static function splitStoragePath( $storagePath ) {
1423                 if ( self::isStoragePath( $storagePath ) ) {
1424                         // Remove the "mwstore://" prefix and split the path
1425                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
1426                         if ( count( $parts ) >= 2 && $parts[0] != '' && $parts[1] != '' ) {
1427                                 if ( count( $parts ) == 3 ) {
1428                                         return $parts; // e.g. "backend/container/path"
1429                                 } else {
1430                                         return [ $parts[0], $parts[1], '' ]; // e.g. "backend/container"
1431                                 }
1432                         }
1433                 }
1434
1435                 return [ null, null, null ];
1436         }
1437
1438         /**
1439          * Normalize a storage path by cleaning up directory separators.
1440          * Returns null if the path is not of the format of a valid storage path.
1441          *
1442          * @param string $storagePath
1443          * @return string|null
1444          */
1445         final public static function normalizeStoragePath( $storagePath ) {
1446                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
1447                 if ( $relPath !== null ) { // must be for this backend
1448                         $relPath = self::normalizeContainerPath( $relPath );
1449                         if ( $relPath !== null ) {
1450                                 return ( $relPath != '' )
1451                                         ? "mwstore://{$backend}/{$container}/{$relPath}"
1452                                         : "mwstore://{$backend}/{$container}";
1453                         }
1454                 }
1455
1456                 return null;
1457         }
1458
1459         /**
1460          * Get the parent storage directory of a storage path.
1461          * This returns a path like "mwstore://backend/container",
1462          * "mwstore://backend/container/...", or null if there is no parent.
1463          *
1464          * @param string $storagePath
1465          * @return string|null
1466          */
1467         final public static function parentStoragePath( $storagePath ) {
1468                 $storagePath = dirname( $storagePath );
1469                 list( , , $rel ) = self::splitStoragePath( $storagePath );
1470
1471                 return ( $rel === null ) ? null : $storagePath;
1472         }
1473
1474         /**
1475          * Get the final extension from a storage or FS path
1476          *
1477          * @param string $path
1478          * @param string $case One of (rawcase, uppercase, lowercase) (since 1.24)
1479          * @return string
1480          */
1481         final public static function extensionFromPath( $path, $case = 'lowercase' ) {
1482                 $i = strrpos( $path, '.' );
1483                 $ext = $i ? substr( $path, $i + 1 ) : '';
1484
1485                 if ( $case === 'lowercase' ) {
1486                         $ext = strtolower( $ext );
1487                 } elseif ( $case === 'uppercase' ) {
1488                         $ext = strtoupper( $ext );
1489                 }
1490
1491                 return $ext;
1492         }
1493
1494         /**
1495          * Check if a relative path has no directory traversals
1496          *
1497          * @param string $path
1498          * @return bool
1499          * @since 1.20
1500          */
1501         final public static function isPathTraversalFree( $path ) {
1502                 return ( self::normalizeContainerPath( $path ) !== null );
1503         }
1504
1505         /**
1506          * Build a Content-Disposition header value per RFC 6266.
1507          *
1508          * @param string $type One of (attachment, inline)
1509          * @param string $filename Suggested file name (should not contain slashes)
1510          * @throws FileBackendError
1511          * @return string
1512          * @since 1.20
1513          */
1514         final public static function makeContentDisposition( $type, $filename = '' ) {
1515                 $parts = [];
1516
1517                 $type = strtolower( $type );
1518                 if ( !in_array( $type, [ 'inline', 'attachment' ] ) ) {
1519                         throw new InvalidArgumentException( "Invalid Content-Disposition type '$type'." );
1520                 }
1521                 $parts[] = $type;
1522
1523                 if ( strlen( $filename ) ) {
1524                         $parts[] = "filename*=UTF-8''" . rawurlencode( basename( $filename ) );
1525                 }
1526
1527                 return implode( ';', $parts );
1528         }
1529
1530         /**
1531          * Validate and normalize a relative storage path.
1532          * Null is returned if the path involves directory traversal.
1533          * Traversal is insecure for FS backends and broken for others.
1534          *
1535          * This uses the same traversal protection as Title::secureAndSplit().
1536          *
1537          * @param string $path Storage path relative to a container
1538          * @return string|null
1539          */
1540         final protected static function normalizeContainerPath( $path ) {
1541                 // Normalize directory separators
1542                 $path = strtr( $path, '\\', '/' );
1543                 // Collapse any consecutive directory separators
1544                 $path = preg_replace( '![/]{2,}!', '/', $path );
1545                 // Remove any leading directory separator
1546                 $path = ltrim( $path, '/' );
1547                 // Use the same traversal protection as Title::secureAndSplit()
1548                 if ( strpos( $path, '.' ) !== false ) {
1549                         if (
1550                                 $path === '.' ||
1551                                 $path === '..' ||
1552                                 strpos( $path, './' ) === 0 ||
1553                                 strpos( $path, '../' ) === 0 ||
1554                                 strpos( $path, '/./' ) !== false ||
1555                                 strpos( $path, '/../' ) !== false
1556                         ) {
1557                                 return null;
1558                         }
1559                 }
1560
1561                 return $path;
1562         }
1563
1564         /**
1565          * Yields the result of the status wrapper callback on either:
1566          *   - StatusValue::newGood() if this method is called without parameters
1567          *   - StatusValue::newFatal() with all parameters to this method if passed in
1568          *
1569          * @param string $args,...
1570          * @return StatusValue
1571          */
1572         final protected function newStatus() {
1573                 $args = func_get_args();
1574                 if ( count( $args ) ) {
1575                         $sv = StatusValue::newFatal( ...$args );
1576                 } else {
1577                         $sv = StatusValue::newGood();
1578                 }
1579
1580                 return $this->wrapStatus( $sv );
1581         }
1582
1583         /**
1584          * @param StatusValue $sv
1585          * @return StatusValue Modified status or StatusValue subclass
1586          */
1587         final protected function wrapStatus( StatusValue $sv ) {
1588                 return $this->statusWrapper ? call_user_func( $this->statusWrapper, $sv ) : $sv;
1589         }
1590
1591         /**
1592          * @param string $section
1593          * @return ScopedCallback|null
1594          */
1595         protected function scopedProfileSection( $section ) {
1596                 if ( $this->profiler ) {
1597                         call_user_func( [ $this->profiler, 'profileIn' ], $section );
1598                         return new ScopedCallback( [ $this->profiler, 'profileOut' ], [ $section ] );
1599                 }
1600
1601                 return null;
1602         }
1603
1604         protected function resetOutputBuffer() {
1605                 while ( ob_get_status() ) {
1606                         if ( !ob_end_clean() ) {
1607                                 // Could not remove output buffer handler; abort now
1608                                 // to avoid getting in some kind of infinite loop.
1609                                 break;
1610                         }
1611                 }
1612         }
1613 }