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 MediaWiki\FileBackend\FSFile\TempFSFileFactory;
  31 use Psr\Log\LoggerAwareInterface;
  32 use Psr\Log\LoggerInterface;
  33 use Wikimedia\ScopedCallback;
  34 use Psr\Log\NullLogger;
  35
  36 /**
  37  * @brief Base class for all file backend classes (including multi-write backends).
  38  *
  39  * This class defines the methods as abstract that subclasses must implement.
  40  * Outside callers can assume that all backends will have these functions.
  41  *
  42  * All "storage paths" are of the format "mwstore://<backend>/<container>/<path>".
  43  * The "backend" portion is unique name for the application to refer to a backend, while
  44  * the "container" portion is a top-level directory of the backend. The "path" portion
  45  * is a relative path that uses UNIX file system (FS) notation, though any particular
  46  * backend may not actually be using a local filesystem. Therefore, the relative paths
  47  * are only virtual.
  48  *
  49  * Backend contents are stored under "domain"-specific container names by default.
  50  * A domain is simply a logical umbrella for entities, such as those belonging to a certain
  51  * application or portion of a website, for example. A domain can be local or global.
  52  * Global (qualified) backends are achieved by configuring the "domain ID" to a constant.
  53  * Global domains are simpler, but local domains can be used by choosing a domain ID based on
  54  * the current context, such as which language of a website is being used.
  55  *
  56  * For legacy reasons, the FSFileBackend class allows manually setting the paths of
  57  * containers to ones that do not respect the "domain ID".
  58  *
  59  * In key/value (object) stores, containers are the only hierarchy (the rest is emulated).
  60  * FS-based backends are somewhat more restrictive due to the existence of real
  61  * directory files; a regular file cannot have the same name as a directory. Other
  62  * backends with virtual directories may not have this limitation. Callers should
  63  * store files in such a way that no files and directories are under the same path.
  64  *
  65  * In general, this class allows for callers to access storage through the same
  66  * interface, without regard to the underlying storage system. However, calling code
  67  * must follow certain patterns and be aware of certain things to ensure compatibility:
  68  *   - a) Always call prepare() on the parent directory before trying to put a file there;
  69  *        key/value stores only need the container to exist first, but filesystems need
  70  *        all the parent directories to exist first (prepare() is aware of all this)
  71  *   - b) Always call clean() on a directory when it might become empty to avoid empty
  72  *        directory buildup on filesystems; key/value stores never have empty directories,
  73  *        so doing this helps preserve consistency in both cases
  74  *   - c) Likewise, do not rely on the existence of empty directories for anything;
  75  *        calling directoryExists() on a path that prepare() was previously called on
  76  *        will return false for key/value stores if there are no files under that path
  77  *   - d) Never alter the resulting FSFile returned from getLocalReference(), as it could
  78  *        either be a copy of the source file in /tmp or the original source file itself
  79  *   - e) Use a file layout that results in never attempting to store files over directories
  80  *        or directories over files; key/value stores allow this but filesystems do not
  81  *   - f) Use ASCII file names (e.g. base32, IDs, hashes) to avoid Unicode issues in Windows
  82  *   - g) Do not assume that move operations are atomic (difficult with key/value stores)
  83  *   - h) Do not assume that file stat or read operations always have immediate consistency;
  84  *        various methods have a "latest" flag that should always be used if up-to-date
  85  *        information is required (this trades performance for correctness as needed)
  86  *   - i) Do not assume that directory listings have immediate consistency
  87  *
  88  * Methods of subclasses should avoid throwing exceptions at all costs.
  89  * As a corollary, external dependencies should be kept to a minimum.
  90  *
  91  * @ingroup FileBackend
  92  * @since 1.19
  93  */
  94 abstract class FileBackend implements LoggerAwareInterface {
  95         /** @var string Unique backend name */
  96         protected $name;
  97
  98         /** @var string Unique domain name */
  99         protected $domainId;
 100
 101         /** @var string Read-only explanation message */
 102         protected $readOnly;
 103
 104         /** @var string When to do operations in parallel */
 105         protected $parallelize;
 106
 107         /** @var int How many operations can be done in parallel */
 108         protected $concurrency;
 109
 110         /** @var TempFSFileFactory */
 111         protected $tmpFileFactory;
 112
 113         /** @var LockManager */
 114         protected $lockManager;
 115         /** @var FileJournal */
 116         protected $fileJournal;
 117         /** @var LoggerInterface */
 118         protected $logger;
 119         /** @var callable|null */
 120         protected $profiler;
 121
 122         /** @var callable */
 123         protected $obResetFunc;
 124         /** @var callable */
 125         protected $streamMimeFunc;
 126         /** @var callable */
 127         protected $statusWrapper;
 128
 129         /** Bitfield flags for supported features */
 130         const ATTR_HEADERS = 1; // files can be tagged with standard HTTP headers
 131         const ATTR_METADATA = 2; // files can be stored with metadata key/values
 132         const ATTR_UNICODE_PATHS = 4; // files can have Unicode paths (not just ASCII)
 133
 134         /** @var null Idiom for "could not determine due to I/O errors" */
 135         const UNKNOWN = null;
 136
 137         /**
 138          * Create a new backend instance from configuration.
 139          * This should only be called from within FileBackendGroup.
 140          *
 141          * @param array $config Parameters include:
 142          *   - name : The unique name of this backend.
 143          *      This should consist of alphanumberic, '-', and '_' characters.
 144          *      This name should not be changed after use (e.g. with journaling).
 145          *      Note that the name is *not* used in actual container names.
 146          *   - domainId : Prefix to container names that is unique to this backend.
 147          *      It should only consist of alphanumberic, '-', and '_' characters.
 148          *      This ID is what avoids collisions if multiple logical backends
 149          *      use the same storage system, so this should be set carefully.
 150          *   - lockManager : LockManager object to use for any file locking.
 151          *      If not provided, then no file locking will be enforced.
 152          *   - fileJournal : FileJournal object to use for logging changes to files.
 153          *      If not provided, then change journaling will be disabled.
 154          *   - readOnly : Write operations are disallowed if this is a non-empty string.
 155          *      It should be an explanation for the backend being read-only.
 156          *   - parallelize : When to do file operations in parallel (when possible).
 157          *      Allowed values are "implicit", "explicit" and "off".
 158          *   - concurrency : How many file operations can be done in parallel.
 159          *   - tmpDirectory : Directory to use for temporary files.
 160          *   - tmpFileFactory : Optional TempFSFileFactory object. Only has an effect if tmpDirectory is
 161          *      not set. If both are unset or null, then the backend will try to discover a usable
 162          *      temporary directory.
 163          *   - obResetFunc : alternative callback to clear the output buffer
 164          *   - streamMimeFunc : alternative method to determine the content type from the path
 165          *   - logger : Optional PSR logger object.
 166          *   - profiler : Optional callback that takes a section name argument and returns
 167          *      a ScopedCallback instance that ends the profile section in its destructor.
 168          * @throws InvalidArgumentException
 169          */
 170         public function __construct( array $config ) {
 171                 $this->name = $config['name'];
 172                 $this->domainId = $config['domainId'] // e.g. "my_wiki-en_"
 173                         ?? $config['wikiId']; // b/c alias
 174                 if ( !preg_match( '!^[a-zA-Z0-9-_]{1,255}$!', $this->name ) ) {
 175                         throw new InvalidArgumentException( "Backend name '{$this->name}' is invalid." );
 176                 } elseif ( !is_string( $this->domainId ) ) {
 177                         throw new InvalidArgumentException(
 178                                 "Backend domain ID not provided for '{$this->name}'." );
 179                 }
 180                 $this->lockManager = $config['lockManager'] ?? new NullLockManager( [] );
 181                 $this->fileJournal = $config['fileJournal']
 182                         ?? FileJournal::factory( [ 'class' => NullFileJournal::class ], $this->name );
 183                 $this->readOnly = isset( $config['readOnly'] )
 184                         ? (string)$config['readOnly']
 185                         : '';
 186                 $this->parallelize = isset( $config['parallelize'] )
 187                         ? (string)$config['parallelize']
 188                         : 'off';
 189                 $this->concurrency = isset( $config['concurrency'] )
 190                         ? (int)$config['concurrency']
 191                         : 50;
 192                 $this->obResetFunc = $config['obResetFunc'] ?? [ $this, 'resetOutputBuffer' ];
 193                 $this->streamMimeFunc = $config['streamMimeFunc'] ?? null;
 194                 $this->statusWrapper = $config['statusWrapper'] ?? null;
 195
 196                 $this->profiler = $config['profiler'] ?? null;
 197                 if ( !is_callable( $this->profiler ) ) {
 198                         $this->profiler = null;
 199                 }
 200                 $this->logger = $config['logger'] ?? new NullLogger();
 201                 $this->statusWrapper = $config['statusWrapper'] ?? null;
 202                 // tmpDirectory gets precedence for backward compatibility
 203                 if ( isset( $config['tmpDirectory'] ) ) {
 204                         $this->tmpFileFactory = new TempFSFileFactory( $config['tmpDirectory'] );
 205                 } else {
 206                         $this->tmpFileFactory = $config['tmpFileFactory'] ?? new TempFSFileFactory();
 207                 }
 208         }
 209
 210         public function setLogger( LoggerInterface $logger ) {
 211                 $this->logger = $logger;
 212         }
 213
 214         /**
 215          * Get the unique backend name
 216          *
 217          * We may have multiple different backends of the same type.
 218          * For example, we can have two Swift backends using different proxies.
 219          *
 220          * @return string
 221          */
 222         final public function getName() {
 223                 return $this->name;
 224         }
 225
 226         /**
 227          * Get the domain identifier used for this backend (possibly empty).
 228          *
 229          * @return string
 230          * @since 1.28
 231          */
 232         final public function getDomainId() {
 233                 return $this->domainId;
 234         }
 235
 236         /**
 237          * Alias to getDomainId()
 238          *
 239          * @return string
 240          * @since 1.20
 241          * @deprecated Since 1.34 Use getDomainId()
 242          */
 243         final public function getWikiId() {
 244                 return $this->getDomainId();
 245         }
 246
 247         /**
 248          * Check if this backend is read-only
 249          *
 250          * @return bool
 251          */
 252         final public function isReadOnly() {
 253                 return ( $this->readOnly != '' );
 254         }
 255
 256         /**
 257          * Get an explanatory message if this backend is read-only
 258          *
 259          * @return string|bool Returns false if the backend is not read-only
 260          */
 261         final public function getReadOnlyReason() {
 262                 return ( $this->readOnly != '' ) ? $this->readOnly : false;
 263         }
 264
 265         /**
 266          * Get the a bitfield of extra features supported by the backend medium
 267          *
 268          * @return int Bitfield of FileBackend::ATTR_* flags
 269          * @since 1.23
 270          */
 271         public function getFeatures() {
 272                 return self::ATTR_UNICODE_PATHS;
 273         }
 274
 275         /**
 276          * Check if the backend medium supports a field of extra features
 277          *
 278          * @param int $bitfield Bitfield of FileBackend::ATTR_* flags
 279          * @return bool
 280          * @since 1.23
 281          */
 282         final public function hasFeatures( $bitfield ) {
 283                 return ( $this->getFeatures() & $bitfield ) === $bitfield;
 284         }
 285
 286         /**
 287          * This is the main entry point into the backend for write operations.
 288          * Callers supply an ordered list of operations to perform as a transaction.
 289          * Files will be locked, the stat cache cleared, and then the operations attempted.
 290          * If any serious errors occur, all attempted operations will be rolled back.
 291          *
 292          * $ops is an array of arrays. The outer array holds a list of operations.
 293          * Each inner array is a set of key value pairs that specify an operation.
 294          *
 295          * Supported operations and their parameters. The supported actions are:
 296          *  - create
 297          *  - store
 298          *  - copy
 299          *  - move
 300          *  - delete
 301          *  - describe (since 1.21)
 302          *  - null
 303          *
 304          * FSFile/TempFSFile object support was added in 1.27.
 305          *
 306          * a) Create a new file in storage with the contents of a string
 307          * @code
 308          *     [
 309          *         'op'                  => 'create',
 310          *         'dst'                 => <storage path>,
 311          *         'content'             => <string of new file contents>,
 312          *         'overwrite'           => <boolean>,
 313          *         'overwriteSame'       => <boolean>,
 314          *         'headers'             => <HTTP header name/value map> # since 1.21
 315          *     ]
 316          * @endcode
 317          *
 318          * b) Copy a file system file into storage
 319          * @code
 320          *     [
 321          *         'op'                  => 'store',
 322          *         'src'                 => <file system path, FSFile, or TempFSFile>,
 323          *         'dst'                 => <storage path>,
 324          *         'overwrite'           => <boolean>,
 325          *         'overwriteSame'       => <boolean>,
 326          *         'headers'             => <HTTP header name/value map> # since 1.21
 327          *     ]
 328          * @endcode
 329          *
 330          * c) Copy a file within storage
 331          * @code
 332          *     [
 333          *         'op'                  => 'copy',
 334          *         'src'                 => <storage path>,
 335          *         'dst'                 => <storage path>,
 336          *         'overwrite'           => <boolean>,
 337          *         'overwriteSame'       => <boolean>,
 338          *         'ignoreMissingSource' => <boolean>, # since 1.21
 339          *         'headers'             => <HTTP header name/value map> # since 1.21
 340          *     ]
 341          * @endcode
 342          *
 343          * d) Move a file within storage
 344          * @code
 345          *     [
 346          *         'op'                  => 'move',
 347          *         'src'                 => <storage path>,
 348          *         'dst'                 => <storage path>,
 349          *         'overwrite'           => <boolean>,
 350          *         'overwriteSame'       => <boolean>,
 351          *         'ignoreMissingSource' => <boolean>, # since 1.21
 352          *         'headers'             => <HTTP header name/value map> # since 1.21
 353          *     ]
 354          * @endcode
 355          *
 356          * e) Delete a file within storage
 357          * @code
 358          *     [
 359          *         'op'                  => 'delete',
 360          *         'src'                 => <storage path>,
 361          *         'ignoreMissingSource' => <boolean>
 362          *     ]
 363          * @endcode
 364          *
 365          * f) Update metadata for a file within storage
 366          * @code
 367          *     [
 368          *         'op'                  => 'describe',
 369          *         'src'                 => <storage path>,
 370          *         'headers'             => <HTTP header name/value map>
 371          *     ]
 372          * @endcode
 373          *
 374          * g) Do nothing (no-op)
 375          * @code
 376          *     [
 377          *         'op'                  => 'null',
 378          *     ]
 379          * @endcode
 380          *
 381          * Boolean flags for operations (operation-specific):
 382          *   - ignoreMissingSource : The operation will simply succeed and do
 383          *                           nothing if the source file does not exist.
 384          *   - overwrite           : Any destination file will be overwritten.
 385          *   - overwriteSame       : If a file already exists at the destination with the
 386          *                           same contents, then do nothing to the destination file
 387          *                           instead of giving an error. This does not compare headers.
 388          *                           This option is ignored if 'overwrite' is already provided.
 389          *   - headers             : If supplied, the result of merging these headers with any
 390          *                           existing source file headers (replacing conflicting ones)
 391          *                           will be set as the destination file headers. Headers are
 392          *                           deleted if their value is set to the empty string. When a
 393          *                           file has headers they are included in responses to GET and
 394          *                           HEAD requests to the backing store for that file.
 395          *                           Header values should be no larger than 255 bytes, except for
 396          *                           Content-Disposition. The system might ignore or truncate any
 397          *                           headers that are too long to store (exact limits will vary).
 398          *                           Backends that don't support metadata ignore this. (since 1.21)
 399          *
 400          * $opts is an associative of boolean flags, including:
 401          *   - force               : Operation precondition errors no longer trigger an abort.
 402          *                           Any remaining operations are still attempted. Unexpected
 403          *                           failures may still cause remaining operations to be aborted.
 404          *   - nonLocking          : No locks are acquired for the operations.
 405          *                           This can increase performance for non-critical writes.
 406          *                           This has no effect unless the 'force' flag is set.
 407          *   - nonJournaled        : Don't log this operation batch in the file journal.
 408          *                           This limits the ability of recovery scripts.
 409          *   - parallelize         : Try to do operations in parallel when possible.
 410          *   - bypassReadOnly      : Allow writes in read-only mode. (since 1.20)
 411          *   - preserveCache       : Don't clear the process cache before checking files.
 412          *                           This should only be used if all entries in the process
 413          *                           cache were added after the files were already locked. (since 1.20)
 414          *
 415          * @note Remarks on locking:
 416          * File system paths given to operations should refer to files that are
 417          * already locked or otherwise safe from modification from other processes.
 418          * Normally these files will be new temp files, which should be adequate.
 419          *
 420          * @par Return value:
 421          *
 422          * This returns a Status, which contains all warnings and fatals that occurred
 423          * during the operation. The 'failCount', 'successCount', and 'success' members
 424          * will reflect each operation attempted.
 425          *
 426          * The StatusValue will be "OK" unless:
 427          *   - a) unexpected operation errors occurred (network partitions, disk full...)
 428          *   - b) predicted operation errors occurred and 'force' was not set
 429          *
 430          * @param array $ops List of operations to execute in order
 431          * @param array $opts Batch operation options
 432          * @return StatusValue
 433          */
 434         final public function doOperations( array $ops, array $opts = [] ) {
 435                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 436                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 437                 }
 438                 if ( $ops === [] ) {
 439                         return $this->newStatus(); // nothing to do
 440                 }
 441
 442                 $ops = $this->resolveFSFileObjects( $ops );
 443                 if ( empty( $opts['force'] ) ) { // sanity
 444                         unset( $opts['nonLocking'] );
 445                 }
 446
 447                 /** @noinspection PhpUnusedLocalVariableInspection */
 448                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 449
 450                 return $this->doOperationsInternal( $ops, $opts );
 451         }
 452
 453         /**
 454          * @see FileBackend::doOperations()
 455          * @param array $ops
 456          * @param array $opts
 457          * @return StatusValue
 458          */
 459         abstract protected function doOperationsInternal( array $ops, array $opts );
 460
 461         /**
 462          * Same as doOperations() except it takes a single operation.
 463          * If you are doing a batch of operations that should either
 464          * all succeed or all fail, then use that function instead.
 465          *
 466          * @see FileBackend::doOperations()
 467          *
 468          * @param array $op Operation
 469          * @param array $opts Operation options
 470          * @return StatusValue
 471          */
 472         final public function doOperation( array $op, array $opts = [] ) {
 473                 return $this->doOperations( [ $op ], $opts );
 474         }
 475
 476         /**
 477          * Performs a single create operation.
 478          * This sets $params['op'] to 'create' and passes it to doOperation().
 479          *
 480          * @see FileBackend::doOperation()
 481          *
 482          * @param array $params Operation parameters
 483          * @param array $opts Operation options
 484          * @return StatusValue
 485          */
 486         final public function create( array $params, array $opts = [] ) {
 487                 return $this->doOperation( [ 'op' => 'create' ] + $params, $opts );
 488         }
 489
 490         /**
 491          * Performs a single store operation.
 492          * This sets $params['op'] to 'store' and passes it to doOperation().
 493          *
 494          * @see FileBackend::doOperation()
 495          *
 496          * @param array $params Operation parameters
 497          * @param array $opts Operation options
 498          * @return StatusValue
 499          */
 500         final public function store( array $params, array $opts = [] ) {
 501                 return $this->doOperation( [ 'op' => 'store' ] + $params, $opts );
 502         }
 503
 504         /**
 505          * Performs a single copy operation.
 506          * This sets $params['op'] to 'copy' and passes it to doOperation().
 507          *
 508          * @see FileBackend::doOperation()
 509          *
 510          * @param array $params Operation parameters
 511          * @param array $opts Operation options
 512          * @return StatusValue
 513          */
 514         final public function copy( array $params, array $opts = [] ) {
 515                 return $this->doOperation( [ 'op' => 'copy' ] + $params, $opts );
 516         }
 517
 518         /**
 519          * Performs a single move operation.
 520          * This sets $params['op'] to 'move' and passes it to doOperation().
 521          *
 522          * @see FileBackend::doOperation()
 523          *
 524          * @param array $params Operation parameters
 525          * @param array $opts Operation options
 526          * @return StatusValue
 527          */
 528         final public function move( array $params, array $opts = [] ) {
 529                 return $this->doOperation( [ 'op' => 'move' ] + $params, $opts );
 530         }
 531
 532         /**
 533          * Performs a single delete operation.
 534          * This sets $params['op'] to 'delete' and passes it to doOperation().
 535          *
 536          * @see FileBackend::doOperation()
 537          *
 538          * @param array $params Operation parameters
 539          * @param array $opts Operation options
 540          * @return StatusValue
 541          */
 542         final public function delete( array $params, array $opts = [] ) {
 543                 return $this->doOperation( [ 'op' => 'delete' ] + $params, $opts );
 544         }
 545
 546         /**
 547          * Performs a single describe operation.
 548          * This sets $params['op'] to 'describe' and passes it to doOperation().
 549          *
 550          * @see FileBackend::doOperation()
 551          *
 552          * @param array $params Operation parameters
 553          * @param array $opts Operation options
 554          * @return StatusValue
 555          * @since 1.21
 556          */
 557         final public function describe( array $params, array $opts = [] ) {
 558                 return $this->doOperation( [ 'op' => 'describe' ] + $params, $opts );
 559         }
 560
 561         /**
 562          * Perform a set of independent file operations on some files.
 563          *
 564          * This does no locking, nor journaling, and possibly no stat calls.
 565          * Any destination files that already exist will be overwritten.
 566          * This should *only* be used on non-original files, like cache files.
 567          *
 568          * Supported operations and their parameters:
 569          *  - create
 570          *  - store
 571          *  - copy
 572          *  - move
 573          *  - delete
 574          *  - describe (since 1.21)
 575          *  - null
 576          *
 577          * FSFile/TempFSFile object support was added in 1.27.
 578          *
 579          * a) Create a new file in storage with the contents of a string
 580          * @code
 581          *     [
 582          *         'op'                  => 'create',
 583          *         'dst'                 => <storage path>,
 584          *         'content'             => <string of new file contents>,
 585          *         'headers'             => <HTTP header name/value map> # since 1.21
 586          *     ]
 587          * @endcode
 588          *
 589          * b) Copy a file system file into storage
 590          * @code
 591          *     [
 592          *         'op'                  => 'store',
 593          *         'src'                 => <file system path, FSFile, or TempFSFile>,
 594          *         'dst'                 => <storage path>,
 595          *         'headers'             => <HTTP header name/value map> # since 1.21
 596          *     ]
 597          * @endcode
 598          *
 599          * c) Copy a file within storage
 600          * @code
 601          *     [
 602          *         'op'                  => 'copy',
 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          * d) Move a file within storage
 611          * @code
 612          *     [
 613          *         'op'                  => 'move',
 614          *         'src'                 => <storage path>,
 615          *         'dst'                 => <storage path>,
 616          *         'ignoreMissingSource' => <boolean>, # since 1.21
 617          *         'headers'             => <HTTP header name/value map> # since 1.21
 618          *     ]
 619          * @endcode
 620          *
 621          * e) Delete a file within storage
 622          * @code
 623          *     [
 624          *         'op'                  => 'delete',
 625          *         'src'                 => <storage path>,
 626          *         'ignoreMissingSource' => <boolean>
 627          *     ]
 628          * @endcode
 629          *
 630          * f) Update metadata for a file within storage
 631          * @code
 632          *     [
 633          *         'op'                  => 'describe',
 634          *         'src'                 => <storage path>,
 635          *         'headers'             => <HTTP header name/value map>
 636          *     ]
 637          * @endcode
 638          *
 639          * g) Do nothing (no-op)
 640          * @code
 641          *     [
 642          *         'op'                  => 'null',
 643          *     ]
 644          * @endcode
 645          *
 646          * @par Boolean flags for operations (operation-specific):
 647          *   - ignoreMissingSource : The operation will simply succeed and do
 648          *                           nothing if the source file does not exist.
 649          *   - headers             : If supplied with a header name/value map, the backend will
 650          *                           reply with these headers when GETs/HEADs of the destination
 651          *                           file are made. Header values should be smaller than 256 bytes.
 652          *                           Content-Disposition headers can be longer, though the system
 653          *                           might ignore or truncate ones that are too long to store.
 654          *                           Existing headers will remain, but these will replace any
 655          *                           conflicting previous headers, and headers will be removed
 656          *                           if they are set to an empty string.
 657          *                           Backends that don't support metadata ignore this. (since 1.21)
 658          *
 659          * $opts is an associative of boolean flags, including:
 660          *   - bypassReadOnly      : Allow writes in read-only mode (since 1.20)
 661          *
 662          * @par Return value:
 663          * This returns a Status, which contains all warnings and fatals that occurred
 664          * during the operation. The 'failCount', 'successCount', and 'success' members
 665          * will reflect each operation attempted for the given files. The StatusValue will be
 666          * considered "OK" as long as no fatal errors occurred.
 667          *
 668          * @param array $ops Set of operations to execute
 669          * @param array $opts Batch operation options
 670          * @return StatusValue
 671          * @since 1.20
 672          */
 673         final public function doQuickOperations( array $ops, array $opts = [] ) {
 674                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 675                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 676                 }
 677                 if ( $ops === [] ) {
 678                         return $this->newStatus(); // nothing to do
 679                 }
 680
 681                 $ops = $this->resolveFSFileObjects( $ops );
 682                 foreach ( $ops as &$op ) {
 683                         $op['overwrite'] = true; // avoids RTTs in key/value stores
 684                 }
 685
 686                 /** @noinspection PhpUnusedLocalVariableInspection */
 687                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 688
 689                 return $this->doQuickOperationsInternal( $ops );
 690         }
 691
 692         /**
 693          * @see FileBackend::doQuickOperations()
 694          * @param array $ops
 695          * @return StatusValue
 696          * @since 1.20
 697          */
 698         abstract protected function doQuickOperationsInternal( array $ops );
 699
 700         /**
 701          * Same as doQuickOperations() except it takes a single operation.
 702          * If you are doing a batch of operations, then use that function instead.
 703          *
 704          * @see FileBackend::doQuickOperations()
 705          *
 706          * @param array $op Operation
 707          * @return StatusValue
 708          * @since 1.20
 709          */
 710         final public function doQuickOperation( array $op ) {
 711                 return $this->doQuickOperations( [ $op ] );
 712         }
 713
 714         /**
 715          * Performs a single quick create operation.
 716          * This sets $params['op'] to 'create' and passes it to doQuickOperation().
 717          *
 718          * @see FileBackend::doQuickOperation()
 719          *
 720          * @param array $params Operation parameters
 721          * @return StatusValue
 722          * @since 1.20
 723          */
 724         final public function quickCreate( array $params ) {
 725                 return $this->doQuickOperation( [ 'op' => 'create' ] + $params );
 726         }
 727
 728         /**
 729          * Performs a single quick store operation.
 730          * This sets $params['op'] to 'store' and passes it to doQuickOperation().
 731          *
 732          * @see FileBackend::doQuickOperation()
 733          *
 734          * @param array $params Operation parameters
 735          * @return StatusValue
 736          * @since 1.20
 737          */
 738         final public function quickStore( array $params ) {
 739                 return $this->doQuickOperation( [ 'op' => 'store' ] + $params );
 740         }
 741
 742         /**
 743          * Performs a single quick copy operation.
 744          * This sets $params['op'] to 'copy' and passes it to doQuickOperation().
 745          *
 746          * @see FileBackend::doQuickOperation()
 747          *
 748          * @param array $params Operation parameters
 749          * @return StatusValue
 750          * @since 1.20
 751          */
 752         final public function quickCopy( array $params ) {
 753                 return $this->doQuickOperation( [ 'op' => 'copy' ] + $params );
 754         }
 755
 756         /**
 757          * Performs a single quick move operation.
 758          * This sets $params['op'] to 'move' and passes it to doQuickOperation().
 759          *
 760          * @see FileBackend::doQuickOperation()
 761          *
 762          * @param array $params Operation parameters
 763          * @return StatusValue
 764          * @since 1.20
 765          */
 766         final public function quickMove( array $params ) {
 767                 return $this->doQuickOperation( [ 'op' => 'move' ] + $params );
 768         }
 769
 770         /**
 771          * Performs a single quick delete operation.
 772          * This sets $params['op'] to 'delete' and passes it to doQuickOperation().
 773          *
 774          * @see FileBackend::doQuickOperation()
 775          *
 776          * @param array $params Operation parameters
 777          * @return StatusValue
 778          * @since 1.20
 779          */
 780         final public function quickDelete( array $params ) {
 781                 return $this->doQuickOperation( [ 'op' => 'delete' ] + $params );
 782         }
 783
 784         /**
 785          * Performs a single quick describe operation.
 786          * This sets $params['op'] to 'describe' and passes it to doQuickOperation().
 787          *
 788          * @see FileBackend::doQuickOperation()
 789          *
 790          * @param array $params Operation parameters
 791          * @return StatusValue
 792          * @since 1.21
 793          */
 794         final public function quickDescribe( array $params ) {
 795                 return $this->doQuickOperation( [ 'op' => 'describe' ] + $params );
 796         }
 797
 798         /**
 799          * Concatenate a list of storage files into a single file system file.
 800          * The target path should refer to a file that is already locked or
 801          * otherwise safe from modification from other processes. Normally,
 802          * the file will be a new temp file, which should be adequate.
 803          *
 804          * @param array $params Operation parameters, include:
 805          *   - srcs        : ordered source storage paths (e.g. chunk1, chunk2, ...)
 806          *   - dst         : file system path to 0-byte temp file
 807          *   - parallelize : try to do operations in parallel when possible
 808          * @return StatusValue
 809          */
 810         abstract public function concatenate( array $params );
 811
 812         /**
 813          * Prepare a storage directory for usage.
 814          * This will create any required containers and parent directories.
 815          * Backends using key/value stores only need to create the container.
 816          *
 817          * The 'noAccess' and 'noListing' parameters works the same as in secure(),
 818          * except they are only applied *if* the directory/container had to be created.
 819          * These flags should always be set for directories that have private files.
 820          * However, setting them is not guaranteed to actually do anything.
 821          * Additional server configuration may be needed to achieve the desired effect.
 822          *
 823          * @param array $params Parameters include:
 824          *   - dir            : storage directory
 825          *   - noAccess       : try to deny file access (since 1.20)
 826          *   - noListing      : try to deny file listing (since 1.20)
 827          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 828          * @return StatusValue
 829          */
 830         final public function prepare( array $params ) {
 831                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 832                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 833                 }
 834                 /** @noinspection PhpUnusedLocalVariableInspection */
 835                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 836                 return $this->doPrepare( $params );
 837         }
 838
 839         /**
 840          * @see FileBackend::prepare()
 841          * @param array $params
 842          * @return StatusValue
 843          */
 844         abstract protected function doPrepare( array $params );
 845
 846         /**
 847          * Take measures to block web access to a storage directory and
 848          * the container it belongs to. FS backends might add .htaccess
 849          * files whereas key/value store backends might revoke container
 850          * access to the storage user representing end-users in web requests.
 851          *
 852          * This is not guaranteed to actually make files or listings publicly hidden.
 853          * Additional server configuration may be needed to achieve the desired effect.
 854          *
 855          * @param array $params Parameters include:
 856          *   - dir            : storage directory
 857          *   - noAccess       : try to deny file access
 858          *   - noListing      : try to deny file listing
 859          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 860          * @return StatusValue
 861          */
 862         final public function secure( array $params ) {
 863                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 864                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 865                 }
 866                 /** @noinspection PhpUnusedLocalVariableInspection */
 867                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 868                 return $this->doSecure( $params );
 869         }
 870
 871         /**
 872          * @see FileBackend::secure()
 873          * @param array $params
 874          * @return StatusValue
 875          */
 876         abstract protected function doSecure( array $params );
 877
 878         /**
 879          * Remove measures to block web access to a storage directory and
 880          * the container it belongs to. FS backends might remove .htaccess
 881          * files whereas key/value store backends might grant container
 882          * access to the storage user representing end-users in web requests.
 883          * This essentially can undo the result of secure() calls.
 884          *
 885          * This is not guaranteed to actually make files or listings publicly viewable.
 886          * Additional server configuration may be needed to achieve the desired effect.
 887          *
 888          * @param array $params Parameters include:
 889          *   - dir            : storage directory
 890          *   - access         : try to allow file access
 891          *   - listing        : try to allow file listing
 892          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 893          * @return StatusValue
 894          * @since 1.20
 895          */
 896         final public function publish( array $params ) {
 897                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 898                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 899                 }
 900                 /** @noinspection PhpUnusedLocalVariableInspection */
 901                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 902                 return $this->doPublish( $params );
 903         }
 904
 905         /**
 906          * @see FileBackend::publish()
 907          * @param array $params
 908          * @return StatusValue
 909          */
 910         abstract protected function doPublish( array $params );
 911
 912         /**
 913          * Delete a storage directory if it is empty.
 914          * Backends using key/value stores may do nothing unless the directory
 915          * is that of an empty container, in which case it will be deleted.
 916          *
 917          * @param array $params Parameters include:
 918          *   - dir            : storage directory
 919          *   - recursive      : recursively delete empty subdirectories first (since 1.20)
 920          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 921          * @return StatusValue
 922          */
 923         final public function clean( array $params ) {
 924                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 925                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 926                 }
 927                 /** @noinspection PhpUnusedLocalVariableInspection */
 928                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 929                 return $this->doClean( $params );
 930         }
 931
 932         /**
 933          * @see FileBackend::clean()
 934          * @param array $params
 935          * @return StatusValue
 936          */
 937         abstract protected function doClean( array $params );
 938
 939         /**
 940          * Check if a file exists at a storage path in the backend.
 941          * This returns false if only a directory exists at the path.
 942          *
 943          * @param array $params Parameters include:
 944          *   - src    : source storage path
 945          *   - latest : use the latest available data
 946          * @return bool|null Returns null on failure
 947          */
 948         abstract public function fileExists( array $params );
 949
 950         /**
 951          * Get the last-modified timestamp of the file at a storage path.
 952          *
 953          * @param array $params Parameters include:
 954          *   - src    : source storage path
 955          *   - latest : use the latest available data
 956          * @return string|bool TS_MW timestamp or false on failure
 957          */
 958         abstract public function getFileTimestamp( array $params );
 959
 960         /**
 961          * Get the contents of a file at a storage path in the backend.
 962          * This should be avoided for potentially large files.
 963          *
 964          * @param array $params Parameters include:
 965          *   - src    : source storage path
 966          *   - latest : use the latest available data
 967          * @return string|bool Returns false on failure
 968          */
 969         final public function getFileContents( array $params ) {
 970                 $contents = $this->getFileContentsMulti(
 971                         [ 'srcs' => [ $params['src'] ] ] + $params );
 972
 973                 return $contents[$params['src']];
 974         }
 975
 976         /**
 977          * Like getFileContents() except it takes an array of storage paths
 978          * and returns a map of storage paths to strings (or null on failure).
 979          * The map keys (paths) are in the same order as the provided list of paths.
 980          *
 981          * @see FileBackend::getFileContents()
 982          *
 983          * @param array $params Parameters include:
 984          *   - srcs        : list of source storage paths
 985          *   - latest      : use the latest available data
 986          *   - parallelize : try to do operations in parallel when possible
 987          * @return array Map of (path name => string or false on failure)
 988          * @since 1.20
 989          */
 990         abstract public function getFileContentsMulti( array $params );
 991
 992         /**
 993          * Get metadata about a file at a storage path in the backend.
 994          * If the file does not exist, then this returns false.
 995          * Otherwise, the result is an associative array that includes:
 996          *   - headers  : map of HTTP headers used for GET/HEAD requests (name => value)
 997          *   - metadata : map of file metadata (name => value)
 998          * Metadata keys and headers names will be returned in all lower-case.
 999          * Additional values may be included for internal use only.
1000          *
1001          * Use FileBackend::hasFeatures() to check how well this is supported.
1002          *
1003          * @param array $params
1004          * $params include:
1005          *   - src    : source storage path
1006          *   - latest : use the latest available data
1007          * @return array|bool Returns false on failure
1008          * @since 1.23
1009          */
1010         abstract public function getFileXAttributes( array $params );
1011
1012         /**
1013          * Get the size (bytes) of a file at a storage path in the backend.
1014          *
1015          * @param array $params Parameters include:
1016          *   - src    : source storage path
1017          *   - latest : use the latest available data
1018          * @return int|bool Returns false on failure
1019          */
1020         abstract public function getFileSize( array $params );
1021
1022         /**
1023          * Get quick information about a file at a storage path in the backend.
1024          * If the file does not exist, then this returns false.
1025          * Otherwise, the result is an associative array that includes:
1026          *   - mtime  : the last-modified timestamp (TS_MW)
1027          *   - size   : the file size (bytes)
1028          * Additional values may be included for internal use only.
1029          *
1030          * @param array $params Parameters include:
1031          *   - src    : source storage path
1032          *   - latest : use the latest available data
1033          * @return array|bool|null Returns null on failure
1034          */
1035         abstract public function getFileStat( array $params );
1036
1037         /**
1038          * Get a SHA-1 hash of the file at a storage path in the backend.
1039          *
1040          * @param array $params Parameters include:
1041          *   - src    : source storage path
1042          *   - latest : use the latest available data
1043          * @return string|bool Hash string or false on failure
1044          */
1045         abstract public function getFileSha1Base36( array $params );
1046
1047         /**
1048          * Get the properties of the file at a storage path in the backend.
1049          * This gives the result of FSFile::getProps() on a local copy of the file.
1050          *
1051          * @param array $params Parameters include:
1052          *   - src    : source storage path
1053          *   - latest : use the latest available data
1054          * @return array Returns FSFile::placeholderProps() on failure
1055          */
1056         abstract public function getFileProps( array $params );
1057
1058         /**
1059          * Stream the file at a storage path in the backend.
1060          *
1061          * If the file does not exists, an HTTP 404 error will be given.
1062          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
1063          * will be sent if streaming began, while none will be sent otherwise.
1064          * Implementations should flush the output buffer before sending data.
1065          *
1066          * @param array $params Parameters include:
1067          *   - src      : source storage path
1068          *   - headers  : list of additional HTTP headers to send if the file exists
1069          *   - options  : HTTP request header map with lower case keys (since 1.28). Supports:
1070          *                range             : format is "bytes=(\d*-\d*)"
1071          *                if-modified-since : format is an HTTP date
1072          *   - headless : only include the body (and headers from "headers") (since 1.28)
1073          *   - latest   : use the latest available data
1074          *   - allowOB  : preserve any output buffers (since 1.28)
1075          * @return StatusValue
1076          */
1077         abstract public function streamFile( array $params );
1078
1079         /**
1080          * Returns a file system file, identical to the file at a storage path.
1081          * The file returned is either:
1082          *   - a) A local copy of the file at a storage path in the backend.
1083          *        The temporary copy will have the same extension as the source.
1084          *   - b) An original of the file at a storage path in the backend.
1085          * Temporary files may be purged when the file object falls out of scope.
1086          *
1087          * Write operations should *never* be done on this file as some backends
1088          * may do internal tracking or may be instances of FileBackendMultiWrite.
1089          * In that latter case, there are copies of the file that must stay in sync.
1090          * Additionally, further calls to this function may return the same file.
1091          *
1092          * @param array $params Parameters include:
1093          *   - src    : source storage path
1094          *   - latest : use the latest available data
1095          * @return FSFile|null Returns null on failure
1096          */
1097         final public function getLocalReference( array $params ) {
1098                 $fsFiles = $this->getLocalReferenceMulti(
1099                         [ 'srcs' => [ $params['src'] ] ] + $params );
1100
1101                 return $fsFiles[$params['src']];
1102         }
1103
1104         /**
1105          * Like getLocalReference() except it takes an array of storage paths
1106          * and returns a map of storage paths to FSFile objects (or null on failure).
1107          * The map keys (paths) are in the same order as the provided list of paths.
1108          *
1109          * @see FileBackend::getLocalReference()
1110          *
1111          * @param array $params Parameters include:
1112          *   - srcs        : list of source storage paths
1113          *   - latest      : use the latest available data
1114          *   - parallelize : try to do operations in parallel when possible
1115          * @return array Map of (path name => FSFile or null on failure)
1116          * @since 1.20
1117          */
1118         abstract public function getLocalReferenceMulti( array $params );
1119
1120         /**
1121          * Get a local copy on disk of the file at a storage path in the backend.
1122          * The temporary copy will have the same file extension as the source.
1123          * Temporary files may be purged when the file object falls out of scope.
1124          *
1125          * @param array $params Parameters include:
1126          *   - src    : source storage path
1127          *   - latest : use the latest available data
1128          * @return TempFSFile|null Returns null on failure
1129          */
1130         final public function getLocalCopy( array $params ) {
1131                 $tmpFiles = $this->getLocalCopyMulti(
1132                         [ 'srcs' => [ $params['src'] ] ] + $params );
1133
1134                 return $tmpFiles[$params['src']];
1135         }
1136
1137         /**
1138          * Like getLocalCopy() except it takes an array of storage paths and
1139          * returns a map of storage paths to TempFSFile objects (or null on failure).
1140          * The map keys (paths) are in the same order as the provided list of paths.
1141          *
1142          * @see FileBackend::getLocalCopy()
1143          *
1144          * @param array $params Parameters include:
1145          *   - srcs        : list of source storage paths
1146          *   - latest      : use the latest available data
1147          *   - parallelize : try to do operations in parallel when possible
1148          * @return array Map of (path name => TempFSFile or null on failure)
1149          * @since 1.20
1150          */
1151         abstract public function getLocalCopyMulti( array $params );
1152
1153         /**
1154          * Return an HTTP URL to a given file that requires no authentication to use.
1155          * The URL may be pre-authenticated (via some token in the URL) and temporary.
1156          * This will return null if the backend cannot make an HTTP URL for the file.
1157          *
1158          * This is useful for key/value stores when using scripts that seek around
1159          * large files and those scripts (and the backend) support HTTP Range headers.
1160          * Otherwise, one would need to use getLocalReference(), which involves loading
1161          * the entire file on to local disk.
1162          *
1163          * @param array $params Parameters include:
1164          *   - src : source storage path
1165          *   - ttl : lifetime (seconds) if pre-authenticated; default is 1 day
1166          * @return string|null
1167          * @since 1.21
1168          */
1169         abstract public function getFileHttpUrl( array $params );
1170
1171         /**
1172          * Check if a directory exists at a given storage path
1173          *
1174          * For backends using key/value stores, a directory is said to exist whenever
1175          * there exist any files with paths using the given directory path as a prefix
1176          * followed by a forward slash. For example, if there is a file called
1177          * "mwstore://backend/container/dir/path.svg" then directories are said to exist
1178          * at "mwstore://backend/container" and "mwstore://backend/container/dir". These
1179          * can be thought of as "virtual" directories.
1180          *
1181          * Backends that directly use a filesystem layer might enumerate empty directories.
1182          * The clean() method should always be used when files are deleted or moved if this
1183          * is a concern. This is a trade-off to avoid write amplication/contention on file
1184          * changes or read amplification when calling this method.
1185          *
1186          * Storage backends with eventual consistency might return stale data.
1187          *
1188          * @see FileBackend::clean()
1189          *
1190          * @param array $params Parameters include:
1191          *   - dir : storage directory
1192          * @return bool|null Whether a directory exists or null on failure
1193          * @since 1.20
1194          */
1195         abstract public function directoryExists( array $params );
1196
1197         /**
1198          * Get an iterator to list *all* directories under a storage directory
1199          *
1200          * If the directory is of the form "mwstore://backend/container",
1201          * then all directories in the container will be listed.
1202          * If the directory is of form "mwstore://backend/container/dir",
1203          * then all directories directly under that directory will be listed.
1204          * Results will be storage directories 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          * @see FileBackend::directoryExists()
1211          *
1212          * @param array $params Parameters include:
1213          *   - dir     : storage directory
1214          *   - topOnly : only return direct child dirs of the directory
1215          * @return Traversable|array|null Directory list enumerator null on failure
1216          * @since 1.20
1217          */
1218         abstract public function getDirectoryList( array $params );
1219
1220         /**
1221          * Same as FileBackend::getDirectoryList() except only lists
1222          * directories that are immediately under the given directory.
1223          *
1224          * Storage backends with eventual consistency might return stale data.
1225          *
1226          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1227          *
1228          * @see FileBackend::directoryExists()
1229          *
1230          * @param array $params Parameters include:
1231          *   - dir : storage directory
1232          * @return Traversable|array|null Directory list enumerator or null on failure
1233          * @since 1.20
1234          */
1235         final public function getTopDirectoryList( array $params ) {
1236                 return $this->getDirectoryList( [ 'topOnly' => true ] + $params );
1237         }
1238
1239         /**
1240          * Get an iterator to list *all* stored files under a storage directory
1241          *
1242          * If the directory is of the form "mwstore://backend/container", then all
1243          * files in the container will be listed. If the directory is of form
1244          * "mwstore://backend/container/dir", then all files under that directory will
1245          * be listed. Results will be storage paths relative to the given directory.
1246          *
1247          * Storage backends with eventual consistency might return stale data.
1248          *
1249          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1250          *
1251          * @param array $params Parameters include:
1252          *   - dir        : storage directory
1253          *   - topOnly    : only return direct child files of the directory (since 1.20)
1254          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1255          * @return Traversable|array|null File list enumerator or null on failure
1256          */
1257         abstract public function getFileList( array $params );
1258
1259         /**
1260          * Same as FileBackend::getFileList() except only lists
1261          * files that are immediately under the given directory.
1262          *
1263          * Storage backends with eventual consistency might return stale data.
1264          *
1265          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1266          *
1267          * @param array $params Parameters include:
1268          *   - dir        : storage directory
1269          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1270          * @return Traversable|array|null File list enumerator or null on failure
1271          * @since 1.20
1272          */
1273         final public function getTopFileList( array $params ) {
1274                 return $this->getFileList( [ 'topOnly' => true ] + $params );
1275         }
1276
1277         /**
1278          * Preload persistent file stat cache and property cache into in-process cache.
1279          * This should be used when stat calls will be made on a known list of a many files.
1280          *
1281          * @see FileBackend::getFileStat()
1282          *
1283          * @param array $paths Storage paths
1284          */
1285         abstract public function preloadCache( array $paths );
1286
1287         /**
1288          * Invalidate any in-process file stat and property cache.
1289          * If $paths is given, then only the cache for those files will be cleared.
1290          *
1291          * @see FileBackend::getFileStat()
1292          *
1293          * @param array|null $paths Storage paths (optional)
1294          */
1295         abstract public function clearCache( array $paths = null );
1296
1297         /**
1298          * Preload file stat information (concurrently if possible) into in-process cache.
1299          *
1300          * This should be used when stat calls will be made on a known list of a many files.
1301          * This does not make use of the persistent file stat cache.
1302          *
1303          * @see FileBackend::getFileStat()
1304          *
1305          * @param array $params Parameters include:
1306          *   - srcs        : list of source storage paths
1307          *   - latest      : use the latest available data
1308          * @return bool Whether all requests proceeded without I/O errors (since 1.24)
1309          * @since 1.23
1310          */
1311         abstract public function preloadFileStat( array $params );
1312
1313         /**
1314          * Lock the files at the given storage paths in the backend.
1315          * This will either lock all the files or none (on failure).
1316          *
1317          * Callers should consider using getScopedFileLocks() instead.
1318          *
1319          * @param array $paths Storage paths
1320          * @param int $type LockManager::LOCK_* constant
1321          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.24)
1322          * @return StatusValue
1323          */
1324         final public function lockFiles( array $paths, $type, $timeout = 0 ) {
1325                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1326
1327                 return $this->wrapStatus( $this->lockManager->lock( $paths, $type, $timeout ) );
1328         }
1329
1330         /**
1331          * Unlock the files at the given storage paths in the backend.
1332          *
1333          * @param array $paths Storage paths
1334          * @param int $type LockManager::LOCK_* constant
1335          * @return StatusValue
1336          */
1337         final public function unlockFiles( array $paths, $type ) {
1338                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1339
1340                 return $this->wrapStatus( $this->lockManager->unlock( $paths, $type ) );
1341         }
1342
1343         /**
1344          * Lock the files at the given storage paths in the backend.
1345          * This will either lock all the files or none (on failure).
1346          * On failure, the StatusValue object will be updated with errors.
1347          *
1348          * Once the return value goes out scope, the locks will be released and
1349          * the StatusValue updated. Unlock fatals will not change the StatusValue "OK" value.
1350          *
1351          * @see ScopedLock::factory()
1352          *
1353          * @param array $paths List of storage paths or map of lock types to path lists
1354          * @param int|string $type LockManager::LOCK_* constant or "mixed"
1355          * @param StatusValue $status StatusValue to update on lock/unlock
1356          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.24)
1357          * @return ScopedLock|null Returns null on failure
1358          */
1359         final public function getScopedFileLocks(
1360                 array $paths, $type, StatusValue $status, $timeout = 0
1361         ) {
1362                 if ( $type === 'mixed' ) {
1363                         foreach ( $paths as &$typePaths ) {
1364                                 $typePaths = array_map( 'FileBackend::normalizeStoragePath', $typePaths );
1365                         }
1366                 } else {
1367                         $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1368                 }
1369
1370                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status, $timeout );
1371         }
1372
1373         /**
1374          * Get an array of scoped locks needed for a batch of file operations.
1375          *
1376          * Normally, FileBackend::doOperations() handles locking, unless
1377          * the 'nonLocking' param is passed in. This function is useful if you
1378          * want the files to be locked for a broader scope than just when the
1379          * files are changing. For example, if you need to update DB metadata,
1380          * you may want to keep the files locked until finished.
1381          *
1382          * @see FileBackend::doOperations()
1383          *
1384          * @param array $ops List of file operations to FileBackend::doOperations()
1385          * @param StatusValue $status StatusValue to update on lock/unlock
1386          * @return ScopedLock|null
1387          * @since 1.20
1388          */
1389         abstract public function getScopedLocksForOps( array $ops, StatusValue $status );
1390
1391         /**
1392          * Get the root storage path of this backend.
1393          * All container paths are "subdirectories" of this path.
1394          *
1395          * @return string Storage path
1396          * @since 1.20
1397          */
1398         final public function getRootStoragePath() {
1399                 return "mwstore://{$this->name}";
1400         }
1401
1402         /**
1403          * Get the storage path for the given container for this backend
1404          *
1405          * @param string $container Container name
1406          * @return string Storage path
1407          * @since 1.21
1408          */
1409         final public function getContainerStoragePath( $container ) {
1410                 return $this->getRootStoragePath() . "/{$container}";
1411         }
1412
1413         /**
1414          * Get the file journal object for this backend
1415          *
1416          * @return FileJournal
1417          */
1418         final public function getJournal() {
1419                 return $this->fileJournal;
1420         }
1421
1422         /**
1423          * Convert FSFile 'src' paths to string paths (with an 'srcRef' field set to the FSFile)
1424          *
1425          * The 'srcRef' field keeps any TempFSFile objects in scope for the backend to have it
1426          * around as long it needs (which may vary greatly depending on configuration)
1427          *
1428          * @param array $ops File operation batch for FileBaclend::doOperations()
1429          * @return array File operation batch
1430          */
1431         protected function resolveFSFileObjects( array $ops ) {
1432                 foreach ( $ops as &$op ) {
1433                         $src = $op['src'] ?? null;
1434                         if ( $src instanceof FSFile ) {
1435                                 $op['srcRef'] = $src;
1436                                 $op['src'] = $src->getPath();
1437                         }
1438                 }
1439                 unset( $op );
1440
1441                 return $ops;
1442         }
1443
1444         /**
1445          * Check if a given path is a "mwstore://" path.
1446          * This does not do any further validation or any existence checks.
1447          *
1448          * @param string $path
1449          * @return bool
1450          */
1451         final public static function isStoragePath( $path ) {
1452                 return ( strpos( $path, 'mwstore://' ) === 0 );
1453         }
1454
1455         /**
1456          * Split a storage path into a backend name, a container name,
1457          * and a relative file path. The relative path may be the empty string.
1458          * This does not do any path normalization or traversal checks.
1459          *
1460          * @param string $storagePath
1461          * @return array (backend, container, rel object) or (null, null, null)
1462          */
1463         final public static function splitStoragePath( $storagePath ) {
1464                 if ( self::isStoragePath( $storagePath ) ) {
1465                         // Remove the "mwstore://" prefix and split the path
1466                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
1467                         if ( count( $parts ) >= 2 && $parts[0] != '' && $parts[1] != '' ) {
1468                                 if ( count( $parts ) == 3 ) {
1469                                         return $parts; // e.g. "backend/container/path"
1470                                 } else {
1471                                         return [ $parts[0], $parts[1], '' ]; // e.g. "backend/container"
1472                                 }
1473                         }
1474                 }
1475
1476                 return [ null, null, null ];
1477         }
1478
1479         /**
1480          * Normalize a storage path by cleaning up directory separators.
1481          * Returns null if the path is not of the format of a valid storage path.
1482          *
1483          * @param string $storagePath
1484          * @return string|null
1485          */
1486         final public static function normalizeStoragePath( $storagePath ) {
1487                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
1488                 if ( $relPath !== null ) { // must be for this backend
1489                         $relPath = self::normalizeContainerPath( $relPath );
1490                         if ( $relPath !== null ) {
1491                                 return ( $relPath != '' )
1492                                         ? "mwstore://{$backend}/{$container}/{$relPath}"
1493                                         : "mwstore://{$backend}/{$container}";
1494                         }
1495                 }
1496
1497                 return null;
1498         }
1499
1500         /**
1501          * Get the parent storage directory of a storage path.
1502          * This returns a path like "mwstore://backend/container",
1503          * "mwstore://backend/container/...", or null if there is no parent.
1504          *
1505          * @param string $storagePath
1506          * @return string|null
1507          */
1508         final public static function parentStoragePath( $storagePath ) {
1509                 $storagePath = dirname( $storagePath );
1510                 list( , , $rel ) = self::splitStoragePath( $storagePath );
1511
1512                 return ( $rel === null ) ? null : $storagePath;
1513         }
1514
1515         /**
1516          * Get the final extension from a storage or FS path
1517          *
1518          * @param string $path
1519          * @param string $case One of (rawcase, uppercase, lowercase) (since 1.24)
1520          * @return string
1521          */
1522         final public static function extensionFromPath( $path, $case = 'lowercase' ) {
1523                 $i = strrpos( $path, '.' );
1524                 $ext = $i ? substr( $path, $i + 1 ) : '';
1525
1526                 if ( $case === 'lowercase' ) {
1527                         $ext = strtolower( $ext );
1528                 } elseif ( $case === 'uppercase' ) {
1529                         $ext = strtoupper( $ext );
1530                 }
1531
1532                 return $ext;
1533         }
1534
1535         /**
1536          * Check if a relative path has no directory traversals
1537          *
1538          * @param string $path
1539          * @return bool
1540          * @since 1.20
1541          */
1542         final public static function isPathTraversalFree( $path ) {
1543                 return ( self::normalizeContainerPath( $path ) !== null );
1544         }
1545
1546         /**
1547          * Build a Content-Disposition header value per RFC 6266.
1548          *
1549          * @param string $type One of (attachment, inline)
1550          * @param string $filename Suggested file name (should not contain slashes)
1551          * @throws InvalidArgumentException
1552          * @return string
1553          * @since 1.20
1554          */
1555         final public static function makeContentDisposition( $type, $filename = '' ) {
1556                 $parts = [];
1557
1558                 $type = strtolower( $type );
1559                 if ( !in_array( $type, [ 'inline', 'attachment' ] ) ) {
1560                         throw new InvalidArgumentException( "Invalid Content-Disposition type '$type'." );
1561                 }
1562                 $parts[] = $type;
1563
1564                 if ( strlen( $filename ) ) {
1565                         $parts[] = "filename*=UTF-8''" . rawurlencode( basename( $filename ) );
1566                 }
1567
1568                 return implode( ';', $parts );
1569         }
1570
1571         /**
1572          * Validate and normalize a relative storage path.
1573          * Null is returned if the path involves directory traversal.
1574          * Traversal is insecure for FS backends and broken for others.
1575          *
1576          * This uses the same traversal protection as Title::secureAndSplit().
1577          *
1578          * @param string $path Storage path relative to a container
1579          * @return string|null
1580          */
1581         final protected static function normalizeContainerPath( $path ) {
1582                 // Normalize directory separators
1583                 $path = strtr( $path, '\\', '/' );
1584                 // Collapse any consecutive directory separators
1585                 $path = preg_replace( '![/]{2,}!', '/', $path );
1586                 // Remove any leading directory separator
1587                 $path = ltrim( $path, '/' );
1588                 // Use the same traversal protection as Title::secureAndSplit()
1589                 if ( strpos( $path, '.' ) !== false ) {
1590                         if (
1591                                 $path === '.' ||
1592                                 $path === '..' ||
1593                                 strpos( $path, './' ) === 0 ||
1594                                 strpos( $path, '../' ) === 0 ||
1595                                 strpos( $path, '/./' ) !== false ||
1596                                 strpos( $path, '/../' ) !== false
1597                         ) {
1598                                 return null;
1599                         }
1600                 }
1601
1602                 return $path;
1603         }
1604
1605         /**
1606          * Yields the result of the status wrapper callback on either:
1607          *   - StatusValue::newGood() if this method is called without parameters
1608          *   - StatusValue::newFatal() with all parameters to this method if passed in
1609          *
1610          * @param string ...$args
1611          * @return StatusValue
1612          */
1613         final protected function newStatus( ...$args ) {
1614                 if ( count( $args ) ) {
1615                         $sv = StatusValue::newFatal( ...$args );
1616                 } else {
1617                         $sv = StatusValue::newGood();
1618                 }
1619
1620                 return $this->wrapStatus( $sv );
1621         }
1622
1623         /**
1624          * @param StatusValue $sv
1625          * @return StatusValue Modified status or StatusValue subclass
1626          */
1627         final protected function wrapStatus( StatusValue $sv ) {
1628                 return $this->statusWrapper ? call_user_func( $this->statusWrapper, $sv ) : $sv;
1629         }
1630
1631         /**
1632          * @param string $section
1633          * @return ScopedCallback|null
1634          */
1635         protected function scopedProfileSection( $section ) {
1636                 return $this->profiler ? ( $this->profiler )( $section ) : null;
1637         }
1638
1639         protected function resetOutputBuffer() {
1640                 while ( ob_get_status() ) {
1641                         if ( !ob_end_clean() ) {
1642                                 // Could not remove output buffer handler; abort now
1643                                 // to avoid getting in some kind of infinite loop.
1644                                 break;
1645                         }
1646                 }
1647         }
1648 }