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  * @author Aaron Schulz
  30  */
  31 use Psr\Log\LoggerAwareInterface;
  32 use Psr\Log\LoggerInterface;
  33 use Wikimedia\ScopedCallback;
  34
  35 /**
  36  * @brief Base class for all file backend classes (including multi-write backends).
  37  *
  38  * This class defines the methods as abstract that subclasses must implement.
  39  * Outside callers can assume that all backends will have these functions.
  40  *
  41  * All "storage paths" are of the format "mwstore://<backend>/<container>/<path>".
  42  * The "backend" portion is unique name for the application to refer to a backend, while
  43  * the "container" portion is a top-level directory of the backend. The "path" portion
  44  * is a relative path that uses UNIX file system (FS) notation, though any particular
  45  * backend may not actually be using a local filesystem. Therefore, the relative paths
  46  * are only virtual.
  47  *
  48  * Backend contents are stored under "domain"-specific container names by default.
  49  * A domain is simply a logical umbrella for entities, such as those belonging to a certain
  50  * application or portion of a website, for example. A domain can be local or global.
  51  * Global (qualified) backends are achieved by configuring the "domain ID" to a constant.
  52  * Global domains are simpler, but local domains can be used by choosing a domain ID based on
  53  * the current context, such as which language of a website is being used.
  54  *
  55  * For legacy reasons, the FSFileBackend class allows manually setting the paths of
  56  * containers to ones that do not respect the "domain ID".
  57  *
  58  * In key/value (object) stores, containers are the only hierarchy (the rest is emulated).
  59  * FS-based backends are somewhat more restrictive due to the existence of real
  60  * directory files; a regular file cannot have the same name as a directory. Other
  61  * backends with virtual directories may not have this limitation. Callers should
  62  * store files in such a way that no files and directories are under the same path.
  63  *
  64  * In general, this class allows for callers to access storage through the same
  65  * interface, without regard to the underlying storage system. However, calling code
  66  * must follow certain patterns and be aware of certain things to ensure compatibility:
  67  *   - a) Always call prepare() on the parent directory before trying to put a file there;
  68  *        key/value stores only need the container to exist first, but filesystems need
  69  *        all the parent directories to exist first (prepare() is aware of all this)
  70  *   - b) Always call clean() on a directory when it might become empty to avoid empty
  71  *        directory buildup on filesystems; key/value stores never have empty directories,
  72  *        so doing this helps preserve consistency in both cases
  73  *   - c) Likewise, do not rely on the existence of empty directories for anything;
  74  *        calling directoryExists() on a path that prepare() was previously called on
  75  *        will return false for key/value stores if there are no files under that path
  76  *   - d) Never alter the resulting FSFile returned from getLocalReference(), as it could
  77  *        either be a copy of the source file in /tmp or the original source file itself
  78  *   - e) Use a file layout that results in never attempting to store files over directories
  79  *        or directories over files; key/value stores allow this but filesystems do not
  80  *   - f) Use ASCII file names (e.g. base32, IDs, hashes) to avoid Unicode issues in Windows
  81  *   - g) Do not assume that move operations are atomic (difficult with key/value stores)
  82  *   - h) Do not assume that file stat or read operations always have immediate consistency;
  83  *        various methods have a "latest" flag that should always be used if up-to-date
  84  *        information is required (this trades performance for correctness as needed)
  85  *   - i) Do not assume that directory listings have immediate consistency
  86  *
  87  * Methods of subclasses should avoid throwing exceptions at all costs.
  88  * As a corollary, external dependencies should be kept to a minimum.
  89  *
  90  * @ingroup FileBackend
  91  * @since 1.19
  92  */
  93 abstract class FileBackend implements LoggerAwareInterface {
  94         /** @var string Unique backend name */
  95         protected $name;
  96
  97         /** @var string Unique domain name */
  98         protected $domainId;
  99
 100         /** @var string Read-only explanation message */
 101         protected $readOnly;
 102
 103         /** @var string When to do operations in parallel */
 104         protected $parallelize;
 105
 106         /** @var int How many operations can be done in parallel */
 107         protected $concurrency;
 108
 109         /** @var string Temporary file directory */
 110         protected $tmpDirectory;
 111
 112         /** @var LockManager */
 113         protected $lockManager;
 114         /** @var FileJournal */
 115         protected $fileJournal;
 116         /** @var LoggerInterface */
 117         protected $logger;
 118         /** @var object|string Class name or object With profileIn/profileOut methods */
 119         protected $profiler;
 120
 121         /** @var callable */
 122         protected $obResetFunc;
 123         /** @var callable */
 124         protected $streamMimeFunc;
 125         /** @var callable */
 126         protected $statusWrapper;
 127
 128         /** Bitfield flags for supported features */
 129         const ATTR_HEADERS = 1; // files can be tagged with standard HTTP headers
 130         const ATTR_METADATA = 2; // files can be stored with metadata key/values
 131         const ATTR_UNICODE_PATHS = 4; // files can have Unicode paths (not just ASCII)
 132
 133         /**
 134          * Create a new backend instance from configuration.
 135          * This should only be called from within FileBackendGroup.
 136          *
 137          * @param array $config Parameters include:
 138          *   - name : The unique name of this backend.
 139          *      This should consist of alphanumberic, '-', and '_' characters.
 140          *      This name should not be changed after use (e.g. with journaling).
 141          *      Note that the name is *not* used in actual container names.
 142          *   - domainId : Prefix to container names that is unique to this backend.
 143          *      It should only consist of alphanumberic, '-', and '_' characters.
 144          *      This ID is what avoids collisions if multiple logical backends
 145          *      use the same storage system, so this should be set carefully.
 146          *   - lockManager : LockManager object to use for any file locking.
 147          *      If not provided, then no file locking will be enforced.
 148          *   - fileJournal : FileJournal object to use for logging changes to files.
 149          *      If not provided, then change journaling will be disabled.
 150          *   - readOnly : Write operations are disallowed if this is a non-empty string.
 151          *      It should be an explanation for the backend being read-only.
 152          *   - parallelize : When to do file operations in parallel (when possible).
 153          *      Allowed values are "implicit", "explicit" and "off".
 154          *   - concurrency : How many file operations can be done in parallel.
 155          *   - tmpDirectory : Directory to use for temporary files. If this is not set or null,
 156          *      then the backend will try to discover a usable temporary directory.
 157          *   - obResetFunc : alternative callback to clear the output buffer
 158          *   - streamMimeFunc : alternative method to determine the content type from the path
 159          *   - logger : Optional PSR logger object.
 160          *   - profiler : Optional class name or object With profileIn/profileOut methods.
 161          * @throws InvalidArgumentException
 162          */
 163         public function __construct( array $config ) {
 164                 $this->name = $config['name'];
 165                 $this->domainId = isset( $config['domainId'] )
 166                         ? $config['domainId'] // e.g. "my_wiki-en_"
 167                         : $config['wikiId']; // b/c alias
 168                 if ( !preg_match( '!^[a-zA-Z0-9-_]{1,255}$!', $this->name ) ) {
 169                         throw new InvalidArgumentException( "Backend name '{$this->name}' is invalid." );
 170                 } elseif ( !is_string( $this->domainId ) ) {
 171                         throw new InvalidArgumentException(
 172                                 "Backend domain ID not provided for '{$this->name}'." );
 173                 }
 174                 $this->lockManager = isset( $config['lockManager'] )
 175                         ? $config['lockManager']
 176                         : new NullLockManager( [] );
 177                 $this->fileJournal = isset( $config['fileJournal'] )
 178                         ? $config['fileJournal']
 179                         : FileJournal::factory( [ 'class' => 'NullFileJournal' ], $this->name );
 180                 $this->readOnly = isset( $config['readOnly'] )
 181                         ? (string)$config['readOnly']
 182                         : '';
 183                 $this->parallelize = isset( $config['parallelize'] )
 184                         ? (string)$config['parallelize']
 185                         : 'off';
 186                 $this->concurrency = isset( $config['concurrency'] )
 187                         ? (int)$config['concurrency']
 188                         : 50;
 189                 $this->obResetFunc = isset( $config['obResetFunc'] )
 190                         ? $config['obResetFunc']
 191                         : [ $this, 'resetOutputBuffer' ];
 192                 $this->streamMimeFunc = isset( $config['streamMimeFunc'] )
 193                         ? $config['streamMimeFunc']
 194                         : null;
 195                 $this->statusWrapper = isset( $config['statusWrapper'] ) ? $config['statusWrapper'] : null;
 196
 197                 $this->profiler = isset( $config['profiler'] ) ? $config['profiler'] : null;
 198                 $this->logger = isset( $config['logger'] ) ? $config['logger'] : new \Psr\Log\NullLogger();
 199                 $this->statusWrapper = isset( $config['statusWrapper'] ) ? $config['statusWrapper'] : null;
 200                 $this->tmpDirectory = isset( $config['tmpDirectory'] ) ? $config['tmpDirectory'] : null;
 201         }
 202
 203         public function setLogger( LoggerInterface $logger ) {
 204                 $this->logger = $logger;
 205         }
 206
 207         /**
 208          * Get the unique backend name.
 209          * We may have multiple different backends of the same type.
 210          * For example, we can have two Swift backends using different proxies.
 211          *
 212          * @return string
 213          */
 214         final public function getName() {
 215                 return $this->name;
 216         }
 217
 218         /**
 219          * Get the domain identifier used for this backend (possibly empty).
 220          *
 221          * @return string
 222          * @since 1.28
 223          */
 224         final public function getDomainId() {
 225                 return $this->domainId;
 226         }
 227
 228         /**
 229          * Alias to getDomainId()
 230          * @return string
 231          * @since 1.20
 232          */
 233         final public function getWikiId() {
 234                 return $this->getDomainId();
 235         }
 236
 237         /**
 238          * Check if this backend is read-only
 239          *
 240          * @return bool
 241          */
 242         final public function isReadOnly() {
 243                 return ( $this->readOnly != '' );
 244         }
 245
 246         /**
 247          * Get an explanatory message if this backend is read-only
 248          *
 249          * @return string|bool Returns false if the backend is not read-only
 250          */
 251         final public function getReadOnlyReason() {
 252                 return ( $this->readOnly != '' ) ? $this->readOnly : false;
 253         }
 254
 255         /**
 256          * Get the a bitfield of extra features supported by the backend medium
 257          *
 258          * @return int Bitfield of FileBackend::ATTR_* flags
 259          * @since 1.23
 260          */
 261         public function getFeatures() {
 262                 return self::ATTR_UNICODE_PATHS;
 263         }
 264
 265         /**
 266          * Check if the backend medium supports a field of extra features
 267          *
 268          * @param int $bitfield Bitfield of FileBackend::ATTR_* flags
 269          * @return bool
 270          * @since 1.23
 271          */
 272         final public function hasFeatures( $bitfield ) {
 273                 return ( $this->getFeatures() & $bitfield ) === $bitfield;
 274         }
 275
 276         /**
 277          * This is the main entry point into the backend for write operations.
 278          * Callers supply an ordered list of operations to perform as a transaction.
 279          * Files will be locked, the stat cache cleared, and then the operations attempted.
 280          * If any serious errors occur, all attempted operations will be rolled back.
 281          *
 282          * $ops is an array of arrays. The outer array holds a list of operations.
 283          * Each inner array is a set of key value pairs that specify an operation.
 284          *
 285          * Supported operations and their parameters. The supported actions are:
 286          *  - create
 287          *  - store
 288          *  - copy
 289          *  - move
 290          *  - delete
 291          *  - describe (since 1.21)
 292          *  - null
 293          *
 294          * FSFile/TempFSFile object support was added in 1.27.
 295          *
 296          * a) Create a new file in storage with the contents of a string
 297          * @code
 298          *     [
 299          *         'op'                  => 'create',
 300          *         'dst'                 => <storage path>,
 301          *         'content'             => <string of new file contents>,
 302          *         'overwrite'           => <boolean>,
 303          *         'overwriteSame'       => <boolean>,
 304          *         'headers'             => <HTTP header name/value map> # since 1.21
 305          *     ]
 306          * @endcode
 307          *
 308          * b) Copy a file system file into storage
 309          * @code
 310          *     [
 311          *         'op'                  => 'store',
 312          *         'src'                 => <file system path, FSFile, or TempFSFile>,
 313          *         'dst'                 => <storage path>,
 314          *         'overwrite'           => <boolean>,
 315          *         'overwriteSame'       => <boolean>,
 316          *         'headers'             => <HTTP header name/value map> # since 1.21
 317          *     ]
 318          * @endcode
 319          *
 320          * c) Copy a file within storage
 321          * @code
 322          *     [
 323          *         'op'                  => 'copy',
 324          *         'src'                 => <storage path>,
 325          *         'dst'                 => <storage path>,
 326          *         'overwrite'           => <boolean>,
 327          *         'overwriteSame'       => <boolean>,
 328          *         'ignoreMissingSource' => <boolean>, # since 1.21
 329          *         'headers'             => <HTTP header name/value map> # since 1.21
 330          *     ]
 331          * @endcode
 332          *
 333          * d) Move a file within storage
 334          * @code
 335          *     [
 336          *         'op'                  => 'move',
 337          *         'src'                 => <storage path>,
 338          *         'dst'                 => <storage path>,
 339          *         'overwrite'           => <boolean>,
 340          *         'overwriteSame'       => <boolean>,
 341          *         'ignoreMissingSource' => <boolean>, # since 1.21
 342          *         'headers'             => <HTTP header name/value map> # since 1.21
 343          *     ]
 344          * @endcode
 345          *
 346          * e) Delete a file within storage
 347          * @code
 348          *     [
 349          *         'op'                  => 'delete',
 350          *         'src'                 => <storage path>,
 351          *         'ignoreMissingSource' => <boolean>
 352          *     ]
 353          * @endcode
 354          *
 355          * f) Update metadata for a file within storage
 356          * @code
 357          *     [
 358          *         'op'                  => 'describe',
 359          *         'src'                 => <storage path>,
 360          *         'headers'             => <HTTP header name/value map>
 361          *     ]
 362          * @endcode
 363          *
 364          * g) Do nothing (no-op)
 365          * @code
 366          *     [
 367          *         'op'                  => 'null',
 368          *     ]
 369          * @endcode
 370          *
 371          * Boolean flags for operations (operation-specific):
 372          *   - ignoreMissingSource : The operation will simply succeed and do
 373          *                           nothing if the source file does not exist.
 374          *   - overwrite           : Any destination file will be overwritten.
 375          *   - overwriteSame       : If a file already exists at the destination with the
 376          *                           same contents, then do nothing to the destination file
 377          *                           instead of giving an error. This does not compare headers.
 378          *                           This option is ignored if 'overwrite' is already provided.
 379          *   - headers             : If supplied, the result of merging these headers with any
 380          *                           existing source file headers (replacing conflicting ones)
 381          *                           will be set as the destination file headers. Headers are
 382          *                           deleted if their value is set to the empty string. When a
 383          *                           file has headers they are included in responses to GET and
 384          *                           HEAD requests to the backing store for that file.
 385          *                           Header values should be no larger than 255 bytes, except for
 386          *                           Content-Disposition. The system might ignore or truncate any
 387          *                           headers that are too long to store (exact limits will vary).
 388          *                           Backends that don't support metadata ignore this. (since 1.21)
 389          *
 390          * $opts is an associative of boolean flags, including:
 391          *   - force               : Operation precondition errors no longer trigger an abort.
 392          *                           Any remaining operations are still attempted. Unexpected
 393          *                           failures may still cause remaining operations to be aborted.
 394          *   - nonLocking          : No locks are acquired for the operations.
 395          *                           This can increase performance for non-critical writes.
 396          *                           This has no effect unless the 'force' flag is set.
 397          *   - nonJournaled        : Don't log this operation batch in the file journal.
 398          *                           This limits the ability of recovery scripts.
 399          *   - parallelize         : Try to do operations in parallel when possible.
 400          *   - bypassReadOnly      : Allow writes in read-only mode. (since 1.20)
 401          *   - preserveCache       : Don't clear the process cache before checking files.
 402          *                           This should only be used if all entries in the process
 403          *                           cache were added after the files were already locked. (since 1.20)
 404          *
 405          * @remarks Remarks on locking:
 406          * File system paths given to operations should refer to files that are
 407          * already locked or otherwise safe from modification from other processes.
 408          * Normally these files will be new temp files, which should be adequate.
 409          *
 410          * @par Return value:
 411          *
 412          * This returns a Status, which contains all warnings and fatals that occurred
 413          * during the operation. The 'failCount', 'successCount', and 'success' members
 414          * will reflect each operation attempted.
 415          *
 416          * The StatusValue will be "OK" unless:
 417          *   - a) unexpected operation errors occurred (network partitions, disk full...)
 418          *   - b) significant operation errors occurred and 'force' was not set
 419          *
 420          * @param array $ops List of operations to execute in order
 421          * @param array $opts Batch operation options
 422          * @return StatusValue
 423          */
 424         final public function doOperations( array $ops, array $opts = [] ) {
 425                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 426                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 427                 }
 428                 if ( !count( $ops ) ) {
 429                         return $this->newStatus(); // nothing to do
 430                 }
 431
 432                 $ops = $this->resolveFSFileObjects( $ops );
 433                 if ( empty( $opts['force'] ) ) { // sanity
 434                         unset( $opts['nonLocking'] );
 435                 }
 436
 437                 /** @noinspection PhpUnusedLocalVariableInspection */
 438                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 439
 440                 return $this->doOperationsInternal( $ops, $opts );
 441         }
 442
 443         /**
 444          * @see FileBackend::doOperations()
 445          * @param array $ops
 446          * @param array $opts
 447          */
 448         abstract protected function doOperationsInternal( array $ops, array $opts );
 449
 450         /**
 451          * Same as doOperations() except it takes a single operation.
 452          * If you are doing a batch of operations that should either
 453          * all succeed or all fail, then use that function instead.
 454          *
 455          * @see FileBackend::doOperations()
 456          *
 457          * @param array $op Operation
 458          * @param array $opts Operation options
 459          * @return StatusValue
 460          */
 461         final public function doOperation( array $op, array $opts = [] ) {
 462                 return $this->doOperations( [ $op ], $opts );
 463         }
 464
 465         /**
 466          * Performs a single create operation.
 467          * This sets $params['op'] to 'create' and passes it to doOperation().
 468          *
 469          * @see FileBackend::doOperation()
 470          *
 471          * @param array $params Operation parameters
 472          * @param array $opts Operation options
 473          * @return StatusValue
 474          */
 475         final public function create( array $params, array $opts = [] ) {
 476                 return $this->doOperation( [ 'op' => 'create' ] + $params, $opts );
 477         }
 478
 479         /**
 480          * Performs a single store operation.
 481          * This sets $params['op'] to 'store' and passes it to doOperation().
 482          *
 483          * @see FileBackend::doOperation()
 484          *
 485          * @param array $params Operation parameters
 486          * @param array $opts Operation options
 487          * @return StatusValue
 488          */
 489         final public function store( array $params, array $opts = [] ) {
 490                 return $this->doOperation( [ 'op' => 'store' ] + $params, $opts );
 491         }
 492
 493         /**
 494          * Performs a single copy operation.
 495          * This sets $params['op'] to 'copy' and passes it to doOperation().
 496          *
 497          * @see FileBackend::doOperation()
 498          *
 499          * @param array $params Operation parameters
 500          * @param array $opts Operation options
 501          * @return StatusValue
 502          */
 503         final public function copy( array $params, array $opts = [] ) {
 504                 return $this->doOperation( [ 'op' => 'copy' ] + $params, $opts );
 505         }
 506
 507         /**
 508          * Performs a single move operation.
 509          * This sets $params['op'] to 'move' and passes it to doOperation().
 510          *
 511          * @see FileBackend::doOperation()
 512          *
 513          * @param array $params Operation parameters
 514          * @param array $opts Operation options
 515          * @return StatusValue
 516          */
 517         final public function move( array $params, array $opts = [] ) {
 518                 return $this->doOperation( [ 'op' => 'move' ] + $params, $opts );
 519         }
 520
 521         /**
 522          * Performs a single delete operation.
 523          * This sets $params['op'] to 'delete' and passes it to doOperation().
 524          *
 525          * @see FileBackend::doOperation()
 526          *
 527          * @param array $params Operation parameters
 528          * @param array $opts Operation options
 529          * @return StatusValue
 530          */
 531         final public function delete( array $params, array $opts = [] ) {
 532                 return $this->doOperation( [ 'op' => 'delete' ] + $params, $opts );
 533         }
 534
 535         /**
 536          * Performs a single describe operation.
 537          * This sets $params['op'] to 'describe' and passes it to doOperation().
 538          *
 539          * @see FileBackend::doOperation()
 540          *
 541          * @param array $params Operation parameters
 542          * @param array $opts Operation options
 543          * @return StatusValue
 544          * @since 1.21
 545          */
 546         final public function describe( array $params, array $opts = [] ) {
 547                 return $this->doOperation( [ 'op' => 'describe' ] + $params, $opts );
 548         }
 549
 550         /**
 551          * Perform a set of independent file operations on some files.
 552          *
 553          * This does no locking, nor journaling, and possibly no stat calls.
 554          * Any destination files that already exist will be overwritten.
 555          * This should *only* be used on non-original files, like cache files.
 556          *
 557          * Supported operations and their parameters:
 558          *  - create
 559          *  - store
 560          *  - copy
 561          *  - move
 562          *  - delete
 563          *  - describe (since 1.21)
 564          *  - null
 565          *
 566          * FSFile/TempFSFile object support was added in 1.27.
 567          *
 568          * a) Create a new file in storage with the contents of a string
 569          * @code
 570          *     [
 571          *         'op'                  => 'create',
 572          *         'dst'                 => <storage path>,
 573          *         'content'             => <string of new file contents>,
 574          *         'headers'             => <HTTP header name/value map> # since 1.21
 575          *     ]
 576          * @endcode
 577          *
 578          * b) Copy a file system file into storage
 579          * @code
 580          *     [
 581          *         'op'                  => 'store',
 582          *         'src'                 => <file system path, FSFile, or TempFSFile>,
 583          *         'dst'                 => <storage path>,
 584          *         'headers'             => <HTTP header name/value map> # since 1.21
 585          *     ]
 586          * @endcode
 587          *
 588          * c) Copy a file within storage
 589          * @code
 590          *     [
 591          *         'op'                  => 'copy',
 592          *         'src'                 => <storage path>,
 593          *         'dst'                 => <storage path>,
 594          *         'ignoreMissingSource' => <boolean>, # since 1.21
 595          *         'headers'             => <HTTP header name/value map> # since 1.21
 596          *     ]
 597          * @endcode
 598          *
 599          * d) Move a file within storage
 600          * @code
 601          *     [
 602          *         'op'                  => 'move',
 603          *         'src'                 => <storage path>,
 604          *         'dst'                 => <storage path>,
 605          *         'ignoreMissingSource' => <boolean>, # since 1.21
 606          *         'headers'             => <HTTP header name/value map> # since 1.21
 607          *     ]
 608          * @endcode
 609          *
 610          * e) Delete a file within storage
 611          * @code
 612          *     [
 613          *         'op'                  => 'delete',
 614          *         'src'                 => <storage path>,
 615          *         'ignoreMissingSource' => <boolean>
 616          *     ]
 617          * @endcode
 618          *
 619          * f) Update metadata for a file within storage
 620          * @code
 621          *     [
 622          *         'op'                  => 'describe',
 623          *         'src'                 => <storage path>,
 624          *         'headers'             => <HTTP header name/value map>
 625          *     ]
 626          * @endcode
 627          *
 628          * g) Do nothing (no-op)
 629          * @code
 630          *     [
 631          *         'op'                  => 'null',
 632          *     ]
 633          * @endcode
 634          *
 635          * @par Boolean flags for operations (operation-specific):
 636          *   - ignoreMissingSource : The operation will simply succeed and do
 637          *                           nothing if the source file does not exist.
 638          *   - headers             : If supplied with a header name/value map, the backend will
 639          *                           reply with these headers when GETs/HEADs of the destination
 640          *                           file are made. Header values should be smaller than 256 bytes.
 641          *                           Content-Disposition headers can be longer, though the system
 642          *                           might ignore or truncate ones that are too long to store.
 643          *                           Existing headers will remain, but these will replace any
 644          *                           conflicting previous headers, and headers will be removed
 645          *                           if they are set to an empty string.
 646          *                           Backends that don't support metadata ignore this. (since 1.21)
 647          *
 648          * $opts is an associative of boolean flags, including:
 649          *   - bypassReadOnly      : Allow writes in read-only mode (since 1.20)
 650          *
 651          * @par Return value:
 652          * This returns a Status, which contains all warnings and fatals that occurred
 653          * during the operation. The 'failCount', 'successCount', and 'success' members
 654          * will reflect each operation attempted for the given files. The StatusValue will be
 655          * considered "OK" as long as no fatal errors occurred.
 656          *
 657          * @param array $ops Set of operations to execute
 658          * @param array $opts Batch operation options
 659          * @return StatusValue
 660          * @since 1.20
 661          */
 662         final public function doQuickOperations( array $ops, array $opts = [] ) {
 663                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 664                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 665                 }
 666                 if ( !count( $ops ) ) {
 667                         return $this->newStatus(); // nothing to do
 668                 }
 669
 670                 $ops = $this->resolveFSFileObjects( $ops );
 671                 foreach ( $ops as &$op ) {
 672                         $op['overwrite'] = true; // avoids RTTs in key/value stores
 673                 }
 674
 675                 /** @noinspection PhpUnusedLocalVariableInspection */
 676                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 677
 678                 return $this->doQuickOperationsInternal( $ops );
 679         }
 680
 681         /**
 682          * @see FileBackend::doQuickOperations()
 683          * @param array $ops
 684          * @since 1.20
 685          */
 686         abstract protected function doQuickOperationsInternal( array $ops );
 687
 688         /**
 689          * Same as doQuickOperations() except it takes a single operation.
 690          * If you are doing a batch of operations, then use that function instead.
 691          *
 692          * @see FileBackend::doQuickOperations()
 693          *
 694          * @param array $op Operation
 695          * @return StatusValue
 696          * @since 1.20
 697          */
 698         final public function doQuickOperation( array $op ) {
 699                 return $this->doQuickOperations( [ $op ] );
 700         }
 701
 702         /**
 703          * Performs a single quick create operation.
 704          * This sets $params['op'] to 'create' and passes it to doQuickOperation().
 705          *
 706          * @see FileBackend::doQuickOperation()
 707          *
 708          * @param array $params Operation parameters
 709          * @return StatusValue
 710          * @since 1.20
 711          */
 712         final public function quickCreate( array $params ) {
 713                 return $this->doQuickOperation( [ 'op' => 'create' ] + $params );
 714         }
 715
 716         /**
 717          * Performs a single quick store operation.
 718          * This sets $params['op'] to 'store' and passes it to doQuickOperation().
 719          *
 720          * @see FileBackend::doQuickOperation()
 721          *
 722          * @param array $params Operation parameters
 723          * @return StatusValue
 724          * @since 1.20
 725          */
 726         final public function quickStore( array $params ) {
 727                 return $this->doQuickOperation( [ 'op' => 'store' ] + $params );
 728         }
 729
 730         /**
 731          * Performs a single quick copy operation.
 732          * This sets $params['op'] to 'copy' and passes it to doQuickOperation().
 733          *
 734          * @see FileBackend::doQuickOperation()
 735          *
 736          * @param array $params Operation parameters
 737          * @return StatusValue
 738          * @since 1.20
 739          */
 740         final public function quickCopy( array $params ) {
 741                 return $this->doQuickOperation( [ 'op' => 'copy' ] + $params );
 742         }
 743
 744         /**
 745          * Performs a single quick move operation.
 746          * This sets $params['op'] to 'move' and passes it to doQuickOperation().
 747          *
 748          * @see FileBackend::doQuickOperation()
 749          *
 750          * @param array $params Operation parameters
 751          * @return StatusValue
 752          * @since 1.20
 753          */
 754         final public function quickMove( array $params ) {
 755                 return $this->doQuickOperation( [ 'op' => 'move' ] + $params );
 756         }
 757
 758         /**
 759          * Performs a single quick delete operation.
 760          * This sets $params['op'] to 'delete' and passes it to doQuickOperation().
 761          *
 762          * @see FileBackend::doQuickOperation()
 763          *
 764          * @param array $params Operation parameters
 765          * @return StatusValue
 766          * @since 1.20
 767          */
 768         final public function quickDelete( array $params ) {
 769                 return $this->doQuickOperation( [ 'op' => 'delete' ] + $params );
 770         }
 771
 772         /**
 773          * Performs a single quick describe operation.
 774          * This sets $params['op'] to 'describe' and passes it to doQuickOperation().
 775          *
 776          * @see FileBackend::doQuickOperation()
 777          *
 778          * @param array $params Operation parameters
 779          * @return StatusValue
 780          * @since 1.21
 781          */
 782         final public function quickDescribe( array $params ) {
 783                 return $this->doQuickOperation( [ 'op' => 'describe' ] + $params );
 784         }
 785
 786         /**
 787          * Concatenate a list of storage files into a single file system file.
 788          * The target path should refer to a file that is already locked or
 789          * otherwise safe from modification from other processes. Normally,
 790          * the file will be a new temp file, which should be adequate.
 791          *
 792          * @param array $params Operation parameters, include:
 793          *   - srcs        : ordered source storage paths (e.g. chunk1, chunk2, ...)
 794          *   - dst         : file system path to 0-byte temp file
 795          *   - parallelize : try to do operations in parallel when possible
 796          * @return StatusValue
 797          */
 798         abstract public function concatenate( array $params );
 799
 800         /**
 801          * Prepare a storage directory for usage.
 802          * This will create any required containers and parent directories.
 803          * Backends using key/value stores only need to create the container.
 804          *
 805          * The 'noAccess' and 'noListing' parameters works the same as in secure(),
 806          * except they are only applied *if* the directory/container had to be created.
 807          * These flags should always be set for directories that have private files.
 808          * However, setting them is not guaranteed to actually do anything.
 809          * Additional server configuration may be needed to achieve the desired effect.
 810          *
 811          * @param array $params Parameters include:
 812          *   - dir            : storage directory
 813          *   - noAccess       : try to deny file access (since 1.20)
 814          *   - noListing      : try to deny file listing (since 1.20)
 815          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 816          * @return StatusValue
 817          */
 818         final public function prepare( array $params ) {
 819                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 820                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 821                 }
 822                 /** @noinspection PhpUnusedLocalVariableInspection */
 823                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 824                 return $this->doPrepare( $params );
 825         }
 826
 827         /**
 828          * @see FileBackend::prepare()
 829          * @param array $params
 830          */
 831         abstract protected function doPrepare( array $params );
 832
 833         /**
 834          * Take measures to block web access to a storage directory and
 835          * the container it belongs to. FS backends might add .htaccess
 836          * files whereas key/value store backends might revoke container
 837          * access to the storage user representing end-users in web requests.
 838          *
 839          * This is not guaranteed to actually make files or listings publically hidden.
 840          * Additional server configuration may be needed to achieve the desired effect.
 841          *
 842          * @param array $params Parameters include:
 843          *   - dir            : storage directory
 844          *   - noAccess       : try to deny file access
 845          *   - noListing      : try to deny file listing
 846          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 847          * @return StatusValue
 848          */
 849         final public function secure( array $params ) {
 850                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 851                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 852                 }
 853                 /** @noinspection PhpUnusedLocalVariableInspection */
 854                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 855                 return $this->doSecure( $params );
 856         }
 857
 858         /**
 859          * @see FileBackend::secure()
 860          * @param array $params
 861          */
 862         abstract protected function doSecure( array $params );
 863
 864         /**
 865          * Remove measures to block web access to a storage directory and
 866          * the container it belongs to. FS backends might remove .htaccess
 867          * files whereas key/value store backends might grant container
 868          * access to the storage user representing end-users in web requests.
 869          * This essentially can undo the result of secure() calls.
 870          *
 871          * This is not guaranteed to actually make files or listings publically viewable.
 872          * Additional server configuration may be needed to achieve the desired effect.
 873          *
 874          * @param array $params Parameters include:
 875          *   - dir            : storage directory
 876          *   - access         : try to allow file access
 877          *   - listing        : try to allow file listing
 878          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 879          * @return StatusValue
 880          * @since 1.20
 881          */
 882         final public function publish( array $params ) {
 883                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 884                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 885                 }
 886                 /** @noinspection PhpUnusedLocalVariableInspection */
 887                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 888                 return $this->doPublish( $params );
 889         }
 890
 891         /**
 892          * @see FileBackend::publish()
 893          * @param array $params
 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 = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 914                 return $this->doClean( $params );
 915         }
 916
 917         /**
 918          * @see FileBackend::clean()
 919          * @param array $params
 920          */
 921         abstract protected function doClean( array $params );
 922
 923         /**
 924          * Enter file operation scope.
 925          * This just makes PHP ignore user aborts/disconnects until the return
 926          * value leaves scope. This returns null and does nothing in CLI mode.
 927          *
 928          * @return ScopedCallback|null
 929          */
 930         final protected function getScopedPHPBehaviorForOps() {
 931                 if ( PHP_SAPI != 'cli' ) { // https://bugs.php.net/bug.php?id=47540
 932                         $old = ignore_user_abort( true ); // avoid half-finished operations
 933                         return new ScopedCallback( function () use ( $old ) {
 934                                 ignore_user_abort( $old );
 935                         } );
 936                 }
 937
 938                 return null;
 939         }
 940
 941         /**
 942          * Check if a file exists at a storage path in the backend.
 943          * This returns false if only a directory exists at the path.
 944          *
 945          * @param array $params Parameters include:
 946          *   - src    : source storage path
 947          *   - latest : use the latest available data
 948          * @return bool|null Returns null on failure
 949          */
 950         abstract public function fileExists( array $params );
 951
 952         /**
 953          * Get the last-modified timestamp of the file at a storage path.
 954          *
 955          * @param array $params Parameters include:
 956          *   - src    : source storage path
 957          *   - latest : use the latest available data
 958          * @return string|bool TS_MW timestamp or false on failure
 959          */
 960         abstract public function getFileTimestamp( array $params );
 961
 962         /**
 963          * Get the contents of a file at a storage path in the backend.
 964          * This should be avoided for potentially large files.
 965          *
 966          * @param array $params Parameters include:
 967          *   - src    : source storage path
 968          *   - latest : use the latest available data
 969          * @return string|bool Returns false on failure
 970          */
 971         final public function getFileContents( array $params ) {
 972                 $contents = $this->getFileContentsMulti(
 973                         [ 'srcs' => [ $params['src'] ] ] + $params );
 974
 975                 return $contents[$params['src']];
 976         }
 977
 978         /**
 979          * Like getFileContents() except it takes an array of storage paths
 980          * and returns a map of storage paths to strings (or null on failure).
 981          * The map keys (paths) are in the same order as the provided list of paths.
 982          *
 983          * @see FileBackend::getFileContents()
 984          *
 985          * @param array $params Parameters include:
 986          *   - srcs        : list of source storage paths
 987          *   - latest      : use the latest available data
 988          *   - parallelize : try to do operations in parallel when possible
 989          * @return array Map of (path name => string or false on failure)
 990          * @since 1.20
 991          */
 992         abstract public function getFileContentsMulti( array $params );
 993
 994         /**
 995          * Get metadata about a file at a storage path in the backend.
 996          * If the file does not exist, then this returns false.
 997          * Otherwise, the result is an associative array that includes:
 998          *   - headers  : map of HTTP headers used for GET/HEAD requests (name => value)
 999          *   - metadata : map of file metadata (name => value)
1000          * Metadata keys and headers names will be returned in all lower-case.
1001          * Additional values may be included for internal use only.
1002          *
1003          * Use FileBackend::hasFeatures() to check how well this is supported.
1004          *
1005          * @param array $params
1006          * $params include:
1007          *   - src    : source storage path
1008          *   - latest : use the latest available data
1009          * @return array|bool Returns false on failure
1010          * @since 1.23
1011          */
1012         abstract public function getFileXAttributes( array $params );
1013
1014         /**
1015          * Get the size (bytes) of a file at a storage path in the backend.
1016          *
1017          * @param array $params Parameters include:
1018          *   - src    : source storage path
1019          *   - latest : use the latest available data
1020          * @return int|bool Returns false on failure
1021          */
1022         abstract public function getFileSize( array $params );
1023
1024         /**
1025          * Get quick information about a file at a storage path in the backend.
1026          * If the file does not exist, then this returns false.
1027          * Otherwise, the result is an associative array that includes:
1028          *   - mtime  : the last-modified timestamp (TS_MW)
1029          *   - size   : the file size (bytes)
1030          * Additional values may be included for internal use only.
1031          *
1032          * @param array $params Parameters include:
1033          *   - src    : source storage path
1034          *   - latest : use the latest available data
1035          * @return array|bool|null Returns null on failure
1036          */
1037         abstract public function getFileStat( array $params );
1038
1039         /**
1040          * Get a SHA-1 hash of the file at a storage path in the backend.
1041          *
1042          * @param array $params Parameters include:
1043          *   - src    : source storage path
1044          *   - latest : use the latest available data
1045          * @return string|bool Hash string or false on failure
1046          */
1047         abstract public function getFileSha1Base36( array $params );
1048
1049         /**
1050          * Get the properties of the file at a storage path in the backend.
1051          * This gives the result of FSFile::getProps() on a local copy of the file.
1052          *
1053          * @param array $params Parameters include:
1054          *   - src    : source storage path
1055          *   - latest : use the latest available data
1056          * @return array Returns FSFile::placeholderProps() on failure
1057          */
1058         abstract public function getFileProps( array $params );
1059
1060         /**
1061          * Stream the file at a storage path in the backend.
1062          *
1063          * If the file does not exists, an HTTP 404 error will be given.
1064          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
1065          * will be sent if streaming began, while none will be sent otherwise.
1066          * Implementations should flush the output buffer before sending data.
1067          *
1068          * @param array $params Parameters include:
1069          *   - src      : source storage path
1070          *   - headers  : list of additional HTTP headers to send if the file exists
1071          *   - options  : HTTP request header map with lower case keys (since 1.28). Supports:
1072          *                range             : format is "bytes=(\d*-\d*)"
1073          *                if-modified-since : format is an HTTP date
1074          *   - headless : only include the body (and headers from "headers") (since 1.28)
1075          *   - latest   : use the latest available data
1076          *   - allowOB  : preserve any output buffers (since 1.28)
1077          * @return StatusValue
1078          */
1079         abstract public function streamFile( array $params );
1080
1081         /**
1082          * Returns a file system file, identical to the file at a storage path.
1083          * The file returned is either:
1084          *   - a) A local copy of the file at a storage path in the backend.
1085          *        The temporary copy will have the same extension as the source.
1086          *   - b) An original of the file at a storage path in the backend.
1087          * Temporary files may be purged when the file object falls out of scope.
1088          *
1089          * Write operations should *never* be done on this file as some backends
1090          * may do internal tracking or may be instances of FileBackendMultiWrite.
1091          * In that latter case, there are copies of the file that must stay in sync.
1092          * Additionally, further calls to this function may return the same file.
1093          *
1094          * @param array $params Parameters include:
1095          *   - src    : source storage path
1096          *   - latest : use the latest available data
1097          * @return FSFile|null Returns null on failure
1098          */
1099         final public function getLocalReference( array $params ) {
1100                 $fsFiles = $this->getLocalReferenceMulti(
1101                         [ 'srcs' => [ $params['src'] ] ] + $params );
1102
1103                 return $fsFiles[$params['src']];
1104         }
1105
1106         /**
1107          * Like getLocalReference() except it takes an array of storage paths
1108          * and returns a map of storage paths to FSFile objects (or null on failure).
1109          * The map keys (paths) are in the same order as the provided list of paths.
1110          *
1111          * @see FileBackend::getLocalReference()
1112          *
1113          * @param array $params Parameters include:
1114          *   - srcs        : list of source storage paths
1115          *   - latest      : use the latest available data
1116          *   - parallelize : try to do operations in parallel when possible
1117          * @return array Map of (path name => FSFile or null on failure)
1118          * @since 1.20
1119          */
1120         abstract public function getLocalReferenceMulti( array $params );
1121
1122         /**
1123          * Get a local copy on disk of the file at a storage path in the backend.
1124          * The temporary copy will have the same file extension as the source.
1125          * Temporary files may be purged when the file object falls out of scope.
1126          *
1127          * @param array $params Parameters include:
1128          *   - src    : source storage path
1129          *   - latest : use the latest available data
1130          * @return TempFSFile|null Returns null on failure
1131          */
1132         final public function getLocalCopy( array $params ) {
1133                 $tmpFiles = $this->getLocalCopyMulti(
1134                         [ 'srcs' => [ $params['src'] ] ] + $params );
1135
1136                 return $tmpFiles[$params['src']];
1137         }
1138
1139         /**
1140          * Like getLocalCopy() except it takes an array of storage paths and
1141          * returns a map of storage paths to TempFSFile objects (or null on failure).
1142          * The map keys (paths) are in the same order as the provided list of paths.
1143          *
1144          * @see FileBackend::getLocalCopy()
1145          *
1146          * @param array $params Parameters include:
1147          *   - srcs        : list of source storage paths
1148          *   - latest      : use the latest available data
1149          *   - parallelize : try to do operations in parallel when possible
1150          * @return array Map of (path name => TempFSFile or null on failure)
1151          * @since 1.20
1152          */
1153         abstract public function getLocalCopyMulti( array $params );
1154
1155         /**
1156          * Return an HTTP URL to a given file that requires no authentication to use.
1157          * The URL may be pre-authenticated (via some token in the URL) and temporary.
1158          * This will return null if the backend cannot make an HTTP URL for the file.
1159          *
1160          * This is useful for key/value stores when using scripts that seek around
1161          * large files and those scripts (and the backend) support HTTP Range headers.
1162          * Otherwise, one would need to use getLocalReference(), which involves loading
1163          * the entire file on to local disk.
1164          *
1165          * @param array $params Parameters include:
1166          *   - src : source storage path
1167          *   - ttl : lifetime (seconds) if pre-authenticated; default is 1 day
1168          * @return string|null
1169          * @since 1.21
1170          */
1171         abstract public function getFileHttpUrl( array $params );
1172
1173         /**
1174          * Check if a directory exists at a given storage path.
1175          * Backends using key/value stores will check if the path is a
1176          * virtual directory, meaning there are files under the given directory.
1177          *
1178          * Storage backends with eventual consistency might return stale data.
1179          *
1180          * @param array $params Parameters include:
1181          *   - dir : storage directory
1182          * @return bool|null Returns null on failure
1183          * @since 1.20
1184          */
1185         abstract public function directoryExists( array $params );
1186
1187         /**
1188          * Get an iterator to list *all* directories under a storage directory.
1189          * If the directory is of the form "mwstore://backend/container",
1190          * then all directories in the container will be listed.
1191          * If the directory is of form "mwstore://backend/container/dir",
1192          * then all directories directly under that directory will be listed.
1193          * Results will be storage directories relative to the given directory.
1194          *
1195          * Storage backends with eventual consistency might return stale data.
1196          *
1197          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1198          *
1199          * @param array $params Parameters include:
1200          *   - dir     : storage directory
1201          *   - topOnly : only return direct child dirs of the directory
1202          * @return Traversable|array|null Returns null on failure
1203          * @since 1.20
1204          */
1205         abstract public function getDirectoryList( array $params );
1206
1207         /**
1208          * Same as FileBackend::getDirectoryList() except only lists
1209          * directories that are immediately under the given directory.
1210          *
1211          * Storage backends with eventual consistency might return stale data.
1212          *
1213          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1214          *
1215          * @param array $params Parameters include:
1216          *   - dir : storage directory
1217          * @return Traversable|array|null Returns null on failure
1218          * @since 1.20
1219          */
1220         final public function getTopDirectoryList( array $params ) {
1221                 return $this->getDirectoryList( [ 'topOnly' => true ] + $params );
1222         }
1223
1224         /**
1225          * Get an iterator to list *all* stored files under a storage directory.
1226          * If the directory is of the form "mwstore://backend/container",
1227          * then all files in the container will be listed.
1228          * If the directory is of form "mwstore://backend/container/dir",
1229          * then all files under that directory will be listed.
1230          * Results will be storage paths relative to the given directory.
1231          *
1232          * Storage backends with eventual consistency might return stale data.
1233          *
1234          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1235          *
1236          * @param array $params Parameters include:
1237          *   - dir        : storage directory
1238          *   - topOnly    : only return direct child files of the directory (since 1.20)
1239          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1240          * @return Traversable|array|null Returns null on failure
1241          */
1242         abstract public function getFileList( array $params );
1243
1244         /**
1245          * Same as FileBackend::getFileList() except only lists
1246          * files that are immediately under the given directory.
1247          *
1248          * Storage backends with eventual consistency might return stale data.
1249          *
1250          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1251          *
1252          * @param array $params Parameters include:
1253          *   - dir        : storage directory
1254          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1255          * @return Traversable|array|null Returns null on failure
1256          * @since 1.20
1257          */
1258         final public function getTopFileList( array $params ) {
1259                 return $this->getFileList( [ 'topOnly' => true ] + $params );
1260         }
1261
1262         /**
1263          * Preload persistent file stat cache and property cache into in-process cache.
1264          * This should be used when stat calls will be made on a known list of a many files.
1265          *
1266          * @see FileBackend::getFileStat()
1267          *
1268          * @param array $paths Storage paths
1269          */
1270         abstract public function preloadCache( array $paths );
1271
1272         /**
1273          * Invalidate any in-process file stat and property cache.
1274          * If $paths is given, then only the cache for those files will be cleared.
1275          *
1276          * @see FileBackend::getFileStat()
1277          *
1278          * @param array $paths Storage paths (optional)
1279          */
1280         abstract public function clearCache( array $paths = null );
1281
1282         /**
1283          * Preload file stat information (concurrently if possible) into in-process cache.
1284          *
1285          * This should be used when stat calls will be made on a known list of a many files.
1286          * This does not make use of the persistent file stat cache.
1287          *
1288          * @see FileBackend::getFileStat()
1289          *
1290          * @param array $params Parameters include:
1291          *   - srcs        : list of source storage paths
1292          *   - latest      : use the latest available data
1293          * @return bool All requests proceeded without I/O errors (since 1.24)
1294          * @since 1.23
1295          */
1296         abstract public function preloadFileStat( array $params );
1297
1298         /**
1299          * Lock the files at the given storage paths in the backend.
1300          * This will either lock all the files or none (on failure).
1301          *
1302          * Callers should consider using getScopedFileLocks() instead.
1303          *
1304          * @param array $paths Storage paths
1305          * @param int $type LockManager::LOCK_* constant
1306          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.24)
1307          * @return StatusValue
1308          */
1309         final public function lockFiles( array $paths, $type, $timeout = 0 ) {
1310                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1311
1312                 return $this->wrapStatus( $this->lockManager->lock( $paths, $type, $timeout ) );
1313         }
1314
1315         /**
1316          * Unlock the files at the given storage paths in the backend.
1317          *
1318          * @param array $paths Storage paths
1319          * @param int $type LockManager::LOCK_* constant
1320          * @return StatusValue
1321          */
1322         final public function unlockFiles( array $paths, $type ) {
1323                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1324
1325                 return $this->wrapStatus( $this->lockManager->unlock( $paths, $type ) );
1326         }
1327
1328         /**
1329          * Lock the files at the given storage paths in the backend.
1330          * This will either lock all the files or none (on failure).
1331          * On failure, the StatusValue object will be updated with errors.
1332          *
1333          * Once the return value goes out scope, the locks will be released and
1334          * the StatusValue updated. Unlock fatals will not change the StatusValue "OK" value.
1335          *
1336          * @see ScopedLock::factory()
1337          *
1338          * @param array $paths List of storage paths or map of lock types to path lists
1339          * @param int|string $type LockManager::LOCK_* constant or "mixed"
1340          * @param StatusValue $status StatusValue to update on lock/unlock
1341          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.24)
1342          * @return ScopedLock|null Returns null on failure
1343          */
1344         final public function getScopedFileLocks(
1345                 array $paths, $type, StatusValue $status, $timeout = 0
1346         ) {
1347                 if ( $type === 'mixed' ) {
1348                         foreach ( $paths as &$typePaths ) {
1349                                 $typePaths = array_map( 'FileBackend::normalizeStoragePath', $typePaths );
1350                         }
1351                 } else {
1352                         $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1353                 }
1354
1355                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status, $timeout );
1356         }
1357
1358         /**
1359          * Get an array of scoped locks needed for a batch of file operations.
1360          *
1361          * Normally, FileBackend::doOperations() handles locking, unless
1362          * the 'nonLocking' param is passed in. This function is useful if you
1363          * want the files to be locked for a broader scope than just when the
1364          * files are changing. For example, if you need to update DB metadata,
1365          * you may want to keep the files locked until finished.
1366          *
1367          * @see FileBackend::doOperations()
1368          *
1369          * @param array $ops List of file operations to FileBackend::doOperations()
1370          * @param StatusValue $status StatusValue to update on lock/unlock
1371          * @return ScopedLock|null
1372          * @since 1.20
1373          */
1374         abstract public function getScopedLocksForOps( array $ops, StatusValue $status );
1375
1376         /**
1377          * Get the root storage path of this backend.
1378          * All container paths are "subdirectories" of this path.
1379          *
1380          * @return string Storage path
1381          * @since 1.20
1382          */
1383         final public function getRootStoragePath() {
1384                 return "mwstore://{$this->name}";
1385         }
1386
1387         /**
1388          * Get the storage path for the given container for this backend
1389          *
1390          * @param string $container Container name
1391          * @return string Storage path
1392          * @since 1.21
1393          */
1394         final public function getContainerStoragePath( $container ) {
1395                 return $this->getRootStoragePath() . "/{$container}";
1396         }
1397
1398         /**
1399          * Get the file journal object for this backend
1400          *
1401          * @return FileJournal
1402          */
1403         final public function getJournal() {
1404                 return $this->fileJournal;
1405         }
1406
1407         /**
1408          * Convert FSFile 'src' paths to string paths (with an 'srcRef' field set to the FSFile)
1409          *
1410          * The 'srcRef' field keeps any TempFSFile objects in scope for the backend to have it
1411          * around as long it needs (which may vary greatly depending on configuration)
1412          *
1413          * @param array $ops File operation batch for FileBaclend::doOperations()
1414          * @return array File operation batch
1415          */
1416         protected function resolveFSFileObjects( array $ops ) {
1417                 foreach ( $ops as &$op ) {
1418                         $src = isset( $op['src'] ) ? $op['src'] : null;
1419                         if ( $src instanceof FSFile ) {
1420                                 $op['srcRef'] = $src;
1421                                 $op['src'] = $src->getPath();
1422                         }
1423                 }
1424                 unset( $op );
1425
1426                 return $ops;
1427         }
1428
1429         /**
1430          * Check if a given path is a "mwstore://" path.
1431          * This does not do any further validation or any existence checks.
1432          *
1433          * @param string $path
1434          * @return bool
1435          */
1436         final public static function isStoragePath( $path ) {
1437                 return ( strpos( $path, 'mwstore://' ) === 0 );
1438         }
1439
1440         /**
1441          * Split a storage path into a backend name, a container name,
1442          * and a relative file path. The relative path may be the empty string.
1443          * This does not do any path normalization or traversal checks.
1444          *
1445          * @param string $storagePath
1446          * @return array (backend, container, rel object) or (null, null, null)
1447          */
1448         final public static function splitStoragePath( $storagePath ) {
1449                 if ( self::isStoragePath( $storagePath ) ) {
1450                         // Remove the "mwstore://" prefix and split the path
1451                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
1452                         if ( count( $parts ) >= 2 && $parts[0] != '' && $parts[1] != '' ) {
1453                                 if ( count( $parts ) == 3 ) {
1454                                         return $parts; // e.g. "backend/container/path"
1455                                 } else {
1456                                         return [ $parts[0], $parts[1], '' ]; // e.g. "backend/container"
1457                                 }
1458                         }
1459                 }
1460
1461                 return [ null, null, null ];
1462         }
1463
1464         /**
1465          * Normalize a storage path by cleaning up directory separators.
1466          * Returns null if the path is not of the format of a valid storage path.
1467          *
1468          * @param string $storagePath
1469          * @return string|null
1470          */
1471         final public static function normalizeStoragePath( $storagePath ) {
1472                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
1473                 if ( $relPath !== null ) { // must be for this backend
1474                         $relPath = self::normalizeContainerPath( $relPath );
1475                         if ( $relPath !== null ) {
1476                                 return ( $relPath != '' )
1477                                         ? "mwstore://{$backend}/{$container}/{$relPath}"
1478                                         : "mwstore://{$backend}/{$container}";
1479                         }
1480                 }
1481
1482                 return null;
1483         }
1484
1485         /**
1486          * Get the parent storage directory of a storage path.
1487          * This returns a path like "mwstore://backend/container",
1488          * "mwstore://backend/container/...", or null if there is no parent.
1489          *
1490          * @param string $storagePath
1491          * @return string|null
1492          */
1493         final public static function parentStoragePath( $storagePath ) {
1494                 $storagePath = dirname( $storagePath );
1495                 list( , , $rel ) = self::splitStoragePath( $storagePath );
1496
1497                 return ( $rel === null ) ? null : $storagePath;
1498         }
1499
1500         /**
1501          * Get the final extension from a storage or FS path
1502          *
1503          * @param string $path
1504          * @param string $case One of (rawcase, uppercase, lowercase) (since 1.24)
1505          * @return string
1506          */
1507         final public static function extensionFromPath( $path, $case = 'lowercase' ) {
1508                 $i = strrpos( $path, '.' );
1509                 $ext = $i ? substr( $path, $i + 1 ) : '';
1510
1511                 if ( $case === 'lowercase' ) {
1512                         $ext = strtolower( $ext );
1513                 } elseif ( $case === 'uppercase' ) {
1514                         $ext = strtoupper( $ext );
1515                 }
1516
1517                 return $ext;
1518         }
1519
1520         /**
1521          * Check if a relative path has no directory traversals
1522          *
1523          * @param string $path
1524          * @return bool
1525          * @since 1.20
1526          */
1527         final public static function isPathTraversalFree( $path ) {
1528                 return ( self::normalizeContainerPath( $path ) !== null );
1529         }
1530
1531         /**
1532          * Build a Content-Disposition header value per RFC 6266.
1533          *
1534          * @param string $type One of (attachment, inline)
1535          * @param string $filename Suggested file name (should not contain slashes)
1536          * @throws FileBackendError
1537          * @return string
1538          * @since 1.20
1539          */
1540         final public static function makeContentDisposition( $type, $filename = '' ) {
1541                 $parts = [];
1542
1543                 $type = strtolower( $type );
1544                 if ( !in_array( $type, [ 'inline', 'attachment' ] ) ) {
1545                         throw new InvalidArgumentException( "Invalid Content-Disposition type '$type'." );
1546                 }
1547                 $parts[] = $type;
1548
1549                 if ( strlen( $filename ) ) {
1550                         $parts[] = "filename*=UTF-8''" . rawurlencode( basename( $filename ) );
1551                 }
1552
1553                 return implode( ';', $parts );
1554         }
1555
1556         /**
1557          * Validate and normalize a relative storage path.
1558          * Null is returned if the path involves directory traversal.
1559          * Traversal is insecure for FS backends and broken for others.
1560          *
1561          * This uses the same traversal protection as Title::secureAndSplit().
1562          *
1563          * @param string $path Storage path relative to a container
1564          * @return string|null
1565          */
1566         final protected static function normalizeContainerPath( $path ) {
1567                 // Normalize directory separators
1568                 $path = strtr( $path, '\\', '/' );
1569                 // Collapse any consecutive directory separators
1570                 $path = preg_replace( '![/]{2,}!', '/', $path );
1571                 // Remove any leading directory separator
1572                 $path = ltrim( $path, '/' );
1573                 // Use the same traversal protection as Title::secureAndSplit()
1574                 if ( strpos( $path, '.' ) !== false ) {
1575                         if (
1576                                 $path === '.' ||
1577                                 $path === '..' ||
1578                                 strpos( $path, './' ) === 0 ||
1579                                 strpos( $path, '../' ) === 0 ||
1580                                 strpos( $path, '/./' ) !== false ||
1581                                 strpos( $path, '/../' ) !== false
1582                         ) {
1583                                 return null;
1584                         }
1585                 }
1586
1587                 return $path;
1588         }
1589
1590         /**
1591          * Yields the result of the status wrapper callback on either:
1592          *   - StatusValue::newGood() if this method is called without parameters
1593          *   - StatusValue::newFatal() with all parameters to this method if passed in
1594          *
1595          * @param ... string
1596          * @return StatusValue
1597          */
1598         final protected function newStatus() {
1599                 $args = func_get_args();
1600                 if ( count( $args ) ) {
1601                         $sv = call_user_func_array( [ 'StatusValue', 'newFatal' ], $args );
1602                 } else {
1603                         $sv = StatusValue::newGood();
1604                 }
1605
1606                 return $this->wrapStatus( $sv );
1607         }
1608
1609         /**
1610          * @param StatusValue $sv
1611          * @return StatusValue Modified status or StatusValue subclass
1612          */
1613         final protected function wrapStatus( StatusValue $sv ) {
1614                 return $this->statusWrapper ? call_user_func( $this->statusWrapper, $sv ) : $sv;
1615         }
1616
1617         /**
1618          * @param string $section
1619          * @return ScopedCallback|null
1620          */
1621         protected function scopedProfileSection( $section ) {
1622                 if ( $this->profiler ) {
1623                         call_user_func( [ $this->profiler, 'profileIn' ], $section );
1624                         return new ScopedCallback( [ $this->profiler, 'profileOut' ], [ $section ] );
1625                 }
1626
1627                 return null;
1628         }
1629
1630         protected function resetOutputBuffer() {
1631                 while ( ob_get_status() ) {
1632                         if ( !ob_end_clean() ) {
1633                                 // Could not remove output buffer handler; abort now
1634                                 // to avoid getting in some kind of infinite loop.
1635                                 break;
1636                         }
1637                 }
1638         }
1639 }