includes/libs/filebackend/FileBackend.php

   1 <?php
   2 /**
   3  * @defgroup FileBackend File backend
   4  *
   5  * File backend is used to interact with file storage systems,
   6  * such as the local file system, NFS, or cloud storage systems.
   7  */
   8
   9 /**
  10  * Base class for all file backends.
  11  *
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  20  * GNU General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License along
  23  * with this program; if not, write to the Free Software Foundation, Inc.,
  24  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  25  * http://www.gnu.org/copyleft/gpl.html
  26  *
  27  * @file
  28  * @ingroup FileBackend
  29  */
  30 use Psr\Log\LoggerAwareInterface;
  31 use Psr\Log\LoggerInterface;
  32 use Wikimedia\ScopedCallback;
  33 use Psr\Log\NullLogger;
  34
  35 /**
  36  * @brief Base class for all file backend classes (including multi-write backends).
  37  *
  38  * This class defines the methods as abstract that subclasses must implement.
  39  * Outside callers can assume that all backends will have these functions.
  40  *
  41  * All "storage paths" are of the format "mwstore://<backend>/<container>/<path>".
  42  * The "backend" portion is unique name for the application to refer to a backend, while
  43  * the "container" portion is a top-level directory of the backend. The "path" portion
  44  * is a relative path that uses UNIX file system (FS) notation, though any particular
  45  * backend may not actually be using a local filesystem. Therefore, the relative paths
  46  * are only virtual.
  47  *
  48  * Backend contents are stored under "domain"-specific container names by default.
  49  * A domain is simply a logical umbrella for entities, such as those belonging to a certain
  50  * application or portion of a website, for example. A domain can be local or global.
  51  * Global (qualified) backends are achieved by configuring the "domain ID" to a constant.
  52  * Global domains are simpler, but local domains can be used by choosing a domain ID based on
  53  * the current context, such as which language of a website is being used.
  54  *
  55  * For legacy reasons, the FSFileBackend class allows manually setting the paths of
  56  * containers to ones that do not respect the "domain ID".
  57  *
  58  * In key/value (object) stores, containers are the only hierarchy (the rest is emulated).
  59  * FS-based backends are somewhat more restrictive due to the existence of real
  60  * directory files; a regular file cannot have the same name as a directory. Other
  61  * backends with virtual directories may not have this limitation. Callers should
  62  * store files in such a way that no files and directories are under the same path.
  63  *
  64  * In general, this class allows for callers to access storage through the same
  65  * interface, without regard to the underlying storage system. However, calling code
  66  * must follow certain patterns and be aware of certain things to ensure compatibility:
  67  *   - a) Always call prepare() on the parent directory before trying to put a file there;
  68  *        key/value stores only need the container to exist first, but filesystems need
  69  *        all the parent directories to exist first (prepare() is aware of all this)
  70  *   - b) Always call clean() on a directory when it might become empty to avoid empty
  71  *        directory buildup on filesystems; key/value stores never have empty directories,
  72  *        so doing this helps preserve consistency in both cases
  73  *   - c) Likewise, do not rely on the existence of empty directories for anything;
  74  *        calling directoryExists() on a path that prepare() was previously called on
  75  *        will return false for key/value stores if there are no files under that path
  76  *   - d) Never alter the resulting FSFile returned from getLocalReference(), as it could
  77  *        either be a copy of the source file in /tmp or the original source file itself
  78  *   - e) Use a file layout that results in never attempting to store files over directories
  79  *        or directories over files; key/value stores allow this but filesystems do not
  80  *   - f) Use ASCII file names (e.g. base32, IDs, hashes) to avoid Unicode issues in Windows
  81  *   - g) Do not assume that move operations are atomic (difficult with key/value stores)
  82  *   - h) Do not assume that file stat or read operations always have immediate consistency;
  83  *        various methods have a "latest" flag that should always be used if up-to-date
  84  *        information is required (this trades performance for correctness as needed)
  85  *   - i) Do not assume that directory listings have immediate consistency
  86  *
  87  * Methods of subclasses should avoid throwing exceptions at all costs.
  88  * As a corollary, external dependencies should be kept to a minimum.
  89  *
  90  * @ingroup FileBackend
  91  * @since 1.19
  92  */
  93 abstract class FileBackend implements LoggerAwareInterface {
  94         /** @var string Unique backend name */
  95         protected $name;
  96
  97         /** @var string Unique domain name */
  98         protected $domainId;
  99
 100         /** @var string Read-only explanation message */
 101         protected $readOnly;
 102
 103         /** @var string When to do operations in parallel */
 104         protected $parallelize;
 105
 106         /** @var int How many operations can be done in parallel */
 107         protected $concurrency;
 108
 109         /** @var string Temporary file directory */
 110         protected $tmpDirectory;
 111
 112         /** @var LockManager */
 113         protected $lockManager;
 114         /** @var FileJournal */
 115         protected $fileJournal;
 116         /** @var LoggerInterface */
 117         protected $logger;
 118         /** @var callable|null */
 119         protected $profiler;
 120
 121         /** @var callable */
 122         protected $obResetFunc;
 123         /** @var callable */
 124         protected $streamMimeFunc;
 125         /** @var callable */
 126         protected $statusWrapper;
 127
 128         /** Bitfield flags for supported features */
 129         const ATTR_HEADERS = 1; // files can be tagged with standard HTTP headers
 130         const ATTR_METADATA = 2; // files can be stored with metadata key/values
 131         const ATTR_UNICODE_PATHS = 4; // files can have Unicode paths (not just ASCII)
 132
 133         /**
 134          * Create a new backend instance from configuration.
 135          * This should only be called from within FileBackendGroup.
 136          *
 137          * @param array $config Parameters include:
 138          *   - name : The unique name of this backend.
 139          *      This should consist of alphanumberic, '-', and '_' characters.
 140          *      This name should not be changed after use (e.g. with journaling).
 141          *      Note that the name is *not* used in actual container names.
 142          *   - domainId : Prefix to container names that is unique to this backend.
 143          *      It should only consist of alphanumberic, '-', and '_' characters.
 144          *      This ID is what avoids collisions if multiple logical backends
 145          *      use the same storage system, so this should be set carefully.
 146          *   - lockManager : LockManager object to use for any file locking.
 147          *      If not provided, then no file locking will be enforced.
 148          *   - fileJournal : FileJournal object to use for logging changes to files.
 149          *      If not provided, then change journaling will be disabled.
 150          *   - readOnly : Write operations are disallowed if this is a non-empty string.
 151          *      It should be an explanation for the backend being read-only.
 152          *   - parallelize : When to do file operations in parallel (when possible).
 153          *      Allowed values are "implicit", "explicit" and "off".
 154          *   - concurrency : How many file operations can be done in parallel.
 155          *   - tmpDirectory : Directory to use for temporary files. If this is not set or null,
 156          *      then the backend will try to discover a usable temporary directory.
 157          *   - obResetFunc : alternative callback to clear the output buffer
 158          *   - streamMimeFunc : alternative method to determine the content type from the path
 159          *   - logger : Optional PSR logger object.
 160          *   - profiler : Optional callback that takes a section name argument and returns
 161          *      a ScopedCallback instance that ends the profile section in its destructor.
 162          * @throws InvalidArgumentException
 163          */
 164         public function __construct( array $config ) {
 165                 $this->name = $config['name'];
 166                 $this->domainId = $config['domainId'] // e.g. "my_wiki-en_"
 167                         ?? $config['wikiId']; // b/c alias
 168                 if ( !preg_match( '!^[a-zA-Z0-9-_]{1,255}$!', $this->name ) ) {
 169                         throw new InvalidArgumentException( "Backend name '{$this->name}' is invalid." );
 170                 } elseif ( !is_string( $this->domainId ) ) {
 171                         throw new InvalidArgumentException(
 172                                 "Backend domain ID not provided for '{$this->name}'." );
 173                 }
 174                 $this->lockManager = $config['lockManager'] ?? new NullLockManager( [] );
 175                 $this->fileJournal = $config['fileJournal']
 176                         ?? FileJournal::factory( [ 'class' => NullFileJournal::class ], $this->name );
 177                 $this->readOnly = isset( $config['readOnly'] )
 178                         ? (string)$config['readOnly']
 179                         : '';
 180                 $this->parallelize = isset( $config['parallelize'] )
 181                         ? (string)$config['parallelize']
 182                         : 'off';
 183                 $this->concurrency = isset( $config['concurrency'] )
 184                         ? (int)$config['concurrency']
 185                         : 50;
 186                 $this->obResetFunc = $config['obResetFunc'] ?? [ $this, 'resetOutputBuffer' ];
 187                 $this->streamMimeFunc = $config['streamMimeFunc'] ?? null;
 188                 $this->statusWrapper = $config['statusWrapper'] ?? null;
 189
 190                 $this->profiler = $config['profiler'] ?? null;
 191                 if ( !is_callable( $this->profiler ) ) {
 192                         $this->profiler = null;
 193                 }
 194                 $this->logger = $config['logger'] ?? new NullLogger();
 195                 $this->statusWrapper = $config['statusWrapper'] ?? null;
 196                 $this->tmpDirectory = $config['tmpDirectory'] ?? null;
 197         }
 198
 199         public function setLogger( LoggerInterface $logger ) {
 200                 $this->logger = $logger;
 201         }
 202
 203         /**
 204          * Get the unique backend name.
 205          * We may have multiple different backends of the same type.
 206          * For example, we can have two Swift backends using different proxies.
 207          *
 208          * @return string
 209          */
 210         final public function getName() {
 211                 return $this->name;
 212         }
 213
 214         /**
 215          * Get the domain identifier used for this backend (possibly empty).
 216          *
 217          * @return string
 218          * @since 1.28
 219          */
 220         final public function getDomainId() {
 221                 return $this->domainId;
 222         }
 223
 224         /**
 225          * Alias to getDomainId()
 226          * @return string
 227          * @since 1.20
 228          * @deprecated Since 1.34 Use getDomainId()
 229          */
 230         final public function getWikiId() {
 231                 return $this->getDomainId();
 232         }
 233
 234         /**
 235          * Check if this backend is read-only
 236          *
 237          * @return bool
 238          */
 239         final public function isReadOnly() {
 240                 return ( $this->readOnly != '' );
 241         }
 242
 243         /**
 244          * Get an explanatory message if this backend is read-only
 245          *
 246          * @return string|bool Returns false if the backend is not read-only
 247          */
 248         final public function getReadOnlyReason() {
 249                 return ( $this->readOnly != '' ) ? $this->readOnly : false;
 250         }
 251
 252         /**
 253          * Get the a bitfield of extra features supported by the backend medium
 254          *
 255          * @return int Bitfield of FileBackend::ATTR_* flags
 256          * @since 1.23
 257          */
 258         public function getFeatures() {
 259                 return self::ATTR_UNICODE_PATHS;
 260         }
 261
 262         /**
 263          * Check if the backend medium supports a field of extra features
 264          *
 265          * @param int $bitfield Bitfield of FileBackend::ATTR_* flags
 266          * @return bool
 267          * @since 1.23
 268          */
 269         final public function hasFeatures( $bitfield ) {
 270                 return ( $this->getFeatures() & $bitfield ) === $bitfield;
 271         }
 272
 273         /**
 274          * This is the main entry point into the backend for write operations.
 275          * Callers supply an ordered list of operations to perform as a transaction.
 276          * Files will be locked, the stat cache cleared, and then the operations attempted.
 277          * If any serious errors occur, all attempted operations will be rolled back.
 278          *
 279          * $ops is an array of arrays. The outer array holds a list of operations.
 280          * Each inner array is a set of key value pairs that specify an operation.
 281          *
 282          * Supported operations and their parameters. The supported actions are:
 283          *  - create
 284          *  - store
 285          *  - copy
 286          *  - move
 287          *  - delete
 288          *  - describe (since 1.21)
 289          *  - null
 290          *
 291          * FSFile/TempFSFile object support was added in 1.27.
 292          *
 293          * a) Create a new file in storage with the contents of a string
 294          * @code
 295          *     [
 296          *         'op'                  => 'create',
 297          *         'dst'                 => <storage path>,
 298          *         'content'             => <string of new file contents>,
 299          *         'overwrite'           => <boolean>,
 300          *         'overwriteSame'       => <boolean>,
 301          *         'headers'             => <HTTP header name/value map> # since 1.21
 302          *     ]
 303          * @endcode
 304          *
 305          * b) Copy a file system file into storage
 306          * @code
 307          *     [
 308          *         'op'                  => 'store',
 309          *         'src'                 => <file system path, FSFile, or TempFSFile>,
 310          *         'dst'                 => <storage path>,
 311          *         'overwrite'           => <boolean>,
 312          *         'overwriteSame'       => <boolean>,
 313          *         'headers'             => <HTTP header name/value map> # since 1.21
 314          *     ]
 315          * @endcode
 316          *
 317          * c) Copy a file within storage
 318          * @code
 319          *     [
 320          *         'op'                  => 'copy',
 321          *         'src'                 => <storage path>,
 322          *         'dst'                 => <storage path>,
 323          *         'overwrite'           => <boolean>,
 324          *         'overwriteSame'       => <boolean>,
 325          *         'ignoreMissingSource' => <boolean>, # since 1.21
 326          *         'headers'             => <HTTP header name/value map> # since 1.21
 327          *     ]
 328          * @endcode
 329          *
 330          * d) Move a file within storage
 331          * @code
 332          *     [
 333          *         'op'                  => 'move',
 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          * e) Delete a file within storage
 344          * @code
 345          *     [
 346          *         'op'                  => 'delete',
 347          *         'src'                 => <storage path>,
 348          *         'ignoreMissingSource' => <boolean>
 349          *     ]
 350          * @endcode
 351          *
 352          * f) Update metadata for a file within storage
 353          * @code
 354          *     [
 355          *         'op'                  => 'describe',
 356          *         'src'                 => <storage path>,
 357          *         'headers'             => <HTTP header name/value map>
 358          *     ]
 359          * @endcode
 360          *
 361          * g) Do nothing (no-op)
 362          * @code
 363          *     [
 364          *         'op'                  => 'null',
 365          *     ]
 366          * @endcode
 367          *
 368          * Boolean flags for operations (operation-specific):
 369          *   - ignoreMissingSource : The operation will simply succeed and do
 370          *                           nothing if the source file does not exist.
 371          *   - overwrite           : Any destination file will be overwritten.
 372          *   - overwriteSame       : If a file already exists at the destination with the
 373          *                           same contents, then do nothing to the destination file
 374          *                           instead of giving an error. This does not compare headers.
 375          *                           This option is ignored if 'overwrite' is already provided.
 376          *   - headers             : If supplied, the result of merging these headers with any
 377          *                           existing source file headers (replacing conflicting ones)
 378          *                           will be set as the destination file headers. Headers are
 379          *                           deleted if their value is set to the empty string. When a
 380          *                           file has headers they are included in responses to GET and
 381          *                           HEAD requests to the backing store for that file.
 382          *                           Header values should be no larger than 255 bytes, except for
 383          *                           Content-Disposition. The system might ignore or truncate any
 384          *                           headers that are too long to store (exact limits will vary).
 385          *                           Backends that don't support metadata ignore this. (since 1.21)
 386          *
 387          * $opts is an associative of boolean flags, including:
 388          *   - force               : Operation precondition errors no longer trigger an abort.
 389          *                           Any remaining operations are still attempted. Unexpected
 390          *                           failures may still cause remaining operations to be aborted.
 391          *   - nonLocking          : No locks are acquired for the operations.
 392          *                           This can increase performance for non-critical writes.
 393          *                           This has no effect unless the 'force' flag is set.
 394          *   - nonJournaled        : Don't log this operation batch in the file journal.
 395          *                           This limits the ability of recovery scripts.
 396          *   - parallelize         : Try to do operations in parallel when possible.
 397          *   - bypassReadOnly      : Allow writes in read-only mode. (since 1.20)
 398          *   - preserveCache       : Don't clear the process cache before checking files.
 399          *                           This should only be used if all entries in the process
 400          *                           cache were added after the files were already locked. (since 1.20)
 401          *
 402          * @note Remarks on locking:
 403          * File system paths given to operations should refer to files that are
 404          * already locked or otherwise safe from modification from other processes.
 405          * Normally these files will be new temp files, which should be adequate.
 406          *
 407          * @par Return value:
 408          *
 409          * This returns a Status, which contains all warnings and fatals that occurred
 410          * during the operation. The 'failCount', 'successCount', and 'success' members
 411          * will reflect each operation attempted.
 412          *
 413          * The StatusValue will be "OK" unless:
 414          *   - a) unexpected operation errors occurred (network partitions, disk full...)
 415          *   - b) significant operation errors occurred and 'force' was not set
 416          *
 417          * @param array $ops List of operations to execute in order
 418          * @param array $opts Batch operation options
 419          * @return StatusValue
 420          */
 421         final public function doOperations( array $ops, array $opts = [] ) {
 422                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 423                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 424                 }
 425                 if ( $ops === [] ) {
 426                         return $this->newStatus(); // nothing to do
 427                 }
 428
 429                 $ops = $this->resolveFSFileObjects( $ops );
 430                 if ( empty( $opts['force'] ) ) { // sanity
 431                         unset( $opts['nonLocking'] );
 432                 }
 433
 434                 /** @noinspection PhpUnusedLocalVariableInspection */
 435                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 436
 437                 return $this->doOperationsInternal( $ops, $opts );
 438         }
 439
 440         /**
 441          * @see FileBackend::doOperations()
 442          * @param array $ops
 443          * @param array $opts
 444          * @return StatusValue
 445          */
 446         abstract protected function doOperationsInternal( array $ops, array $opts );
 447
 448         /**
 449          * Same as doOperations() except it takes a single operation.
 450          * If you are doing a batch of operations that should either
 451          * all succeed or all fail, then use that function instead.
 452          *
 453          * @see FileBackend::doOperations()
 454          *
 455          * @param array $op Operation
 456          * @param array $opts Operation options
 457          * @return StatusValue
 458          */
 459         final public function doOperation( array $op, array $opts = [] ) {
 460                 return $this->doOperations( [ $op ], $opts );
 461         }
 462
 463         /**
 464          * Performs a single create operation.
 465          * This sets $params['op'] to 'create' and passes it to doOperation().
 466          *
 467          * @see FileBackend::doOperation()
 468          *
 469          * @param array $params Operation parameters
 470          * @param array $opts Operation options
 471          * @return StatusValue
 472          */
 473         final public function create( array $params, array $opts = [] ) {
 474                 return $this->doOperation( [ 'op' => 'create' ] + $params, $opts );
 475         }
 476
 477         /**
 478          * Performs a single store operation.
 479          * This sets $params['op'] to 'store' and passes it to doOperation().
 480          *
 481          * @see FileBackend::doOperation()
 482          *
 483          * @param array $params Operation parameters
 484          * @param array $opts Operation options
 485          * @return StatusValue
 486          */
 487         final public function store( array $params, array $opts = [] ) {
 488                 return $this->doOperation( [ 'op' => 'store' ] + $params, $opts );
 489         }
 490
 491         /**
 492          * Performs a single copy operation.
 493          * This sets $params['op'] to 'copy' and passes it to doOperation().
 494          *
 495          * @see FileBackend::doOperation()
 496          *
 497          * @param array $params Operation parameters
 498          * @param array $opts Operation options
 499          * @return StatusValue
 500          */
 501         final public function copy( array $params, array $opts = [] ) {
 502                 return $this->doOperation( [ 'op' => 'copy' ] + $params, $opts );
 503         }
 504
 505         /**
 506          * Performs a single move operation.
 507          * This sets $params['op'] to 'move' and passes it to doOperation().
 508          *
 509          * @see FileBackend::doOperation()
 510          *
 511          * @param array $params Operation parameters
 512          * @param array $opts Operation options
 513          * @return StatusValue
 514          */
 515         final public function move( array $params, array $opts = [] ) {
 516                 return $this->doOperation( [ 'op' => 'move' ] + $params, $opts );
 517         }
 518
 519         /**
 520          * Performs a single delete operation.
 521          * This sets $params['op'] to 'delete' and passes it to doOperation().
 522          *
 523          * @see FileBackend::doOperation()
 524          *
 525          * @param array $params Operation parameters
 526          * @param array $opts Operation options
 527          * @return StatusValue
 528          */
 529         final public function delete( array $params, array $opts = [] ) {
 530                 return $this->doOperation( [ 'op' => 'delete' ] + $params, $opts );
 531         }
 532
 533         /**
 534          * Performs a single describe operation.
 535          * This sets $params['op'] to 'describe' and passes it to doOperation().
 536          *
 537          * @see FileBackend::doOperation()
 538          *
 539          * @param array $params Operation parameters
 540          * @param array $opts Operation options
 541          * @return StatusValue
 542          * @since 1.21
 543          */
 544         final public function describe( array $params, array $opts = [] ) {
 545                 return $this->doOperation( [ 'op' => 'describe' ] + $params, $opts );
 546         }
 547
 548         /**
 549          * Perform a set of independent file operations on some files.
 550          *
 551          * This does no locking, nor journaling, and possibly no stat calls.
 552          * Any destination files that already exist will be overwritten.
 553          * This should *only* be used on non-original files, like cache files.
 554          *
 555          * Supported operations and their parameters:
 556          *  - create
 557          *  - store
 558          *  - copy
 559          *  - move
 560          *  - delete
 561          *  - describe (since 1.21)
 562          *  - null
 563          *
 564          * FSFile/TempFSFile object support was added in 1.27.
 565          *
 566          * a) Create a new file in storage with the contents of a string
 567          * @code
 568          *     [
 569          *         'op'                  => 'create',
 570          *         'dst'                 => <storage path>,
 571          *         'content'             => <string of new file contents>,
 572          *         'headers'             => <HTTP header name/value map> # since 1.21
 573          *     ]
 574          * @endcode
 575          *
 576          * b) Copy a file system file into storage
 577          * @code
 578          *     [
 579          *         'op'                  => 'store',
 580          *         'src'                 => <file system path, FSFile, or TempFSFile>,
 581          *         'dst'                 => <storage path>,
 582          *         'headers'             => <HTTP header name/value map> # since 1.21
 583          *     ]
 584          * @endcode
 585          *
 586          * c) Copy a file within storage
 587          * @code
 588          *     [
 589          *         'op'                  => 'copy',
 590          *         'src'                 => <storage path>,
 591          *         'dst'                 => <storage path>,
 592          *         'ignoreMissingSource' => <boolean>, # since 1.21
 593          *         'headers'             => <HTTP header name/value map> # since 1.21
 594          *     ]
 595          * @endcode
 596          *
 597          * d) Move a file within storage
 598          * @code
 599          *     [
 600          *         'op'                  => 'move',
 601          *         'src'                 => <storage path>,
 602          *         'dst'                 => <storage path>,
 603          *         'ignoreMissingSource' => <boolean>, # since 1.21
 604          *         'headers'             => <HTTP header name/value map> # since 1.21
 605          *     ]
 606          * @endcode
 607          *
 608          * e) Delete a file within storage
 609          * @code
 610          *     [
 611          *         'op'                  => 'delete',
 612          *         'src'                 => <storage path>,
 613          *         'ignoreMissingSource' => <boolean>
 614          *     ]
 615          * @endcode
 616          *
 617          * f) Update metadata for a file within storage
 618          * @code
 619          *     [
 620          *         'op'                  => 'describe',
 621          *         'src'                 => <storage path>,
 622          *         'headers'             => <HTTP header name/value map>
 623          *     ]
 624          * @endcode
 625          *
 626          * g) Do nothing (no-op)
 627          * @code
 628          *     [
 629          *         'op'                  => 'null',
 630          *     ]
 631          * @endcode
 632          *
 633          * @par Boolean flags for operations (operation-specific):
 634          *   - ignoreMissingSource : The operation will simply succeed and do
 635          *                           nothing if the source file does not exist.
 636          *   - headers             : If supplied with a header name/value map, the backend will
 637          *                           reply with these headers when GETs/HEADs of the destination
 638          *                           file are made. Header values should be smaller than 256 bytes.
 639          *                           Content-Disposition headers can be longer, though the system
 640          *                           might ignore or truncate ones that are too long to store.
 641          *                           Existing headers will remain, but these will replace any
 642          *                           conflicting previous headers, and headers will be removed
 643          *                           if they are set to an empty string.
 644          *                           Backends that don't support metadata ignore this. (since 1.21)
 645          *
 646          * $opts is an associative of boolean flags, including:
 647          *   - bypassReadOnly      : Allow writes in read-only mode (since 1.20)
 648          *
 649          * @par Return value:
 650          * This returns a Status, which contains all warnings and fatals that occurred
 651          * during the operation. The 'failCount', 'successCount', and 'success' members
 652          * will reflect each operation attempted for the given files. The StatusValue will be
 653          * considered "OK" as long as no fatal errors occurred.
 654          *
 655          * @param array $ops Set of operations to execute
 656          * @param array $opts Batch operation options
 657          * @return StatusValue
 658          * @since 1.20
 659          */
 660         final public function doQuickOperations( array $ops, array $opts = [] ) {
 661                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 662                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 663                 }
 664                 if ( $ops === [] ) {
 665                         return $this->newStatus(); // nothing to do
 666                 }
 667
 668                 $ops = $this->resolveFSFileObjects( $ops );
 669                 foreach ( $ops as &$op ) {
 670                         $op['overwrite'] = true; // avoids RTTs in key/value stores
 671                 }
 672
 673                 /** @noinspection PhpUnusedLocalVariableInspection */
 674                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 675
 676                 return $this->doQuickOperationsInternal( $ops );
 677         }
 678
 679         /**
 680          * @see FileBackend::doQuickOperations()
 681          * @param array $ops
 682          * @return StatusValue
 683          * @since 1.20
 684          */
 685         abstract protected function doQuickOperationsInternal( array $ops );
 686
 687         /**
 688          * Same as doQuickOperations() except it takes a single operation.
 689          * If you are doing a batch of operations, then use that function instead.
 690          *
 691          * @see FileBackend::doQuickOperations()
 692          *
 693          * @param array $op Operation
 694          * @return StatusValue
 695          * @since 1.20
 696          */
 697         final public function doQuickOperation( array $op ) {
 698                 return $this->doQuickOperations( [ $op ] );
 699         }
 700
 701         /**
 702          * Performs a single quick create operation.
 703          * This sets $params['op'] to 'create' and passes it to doQuickOperation().
 704          *
 705          * @see FileBackend::doQuickOperation()
 706          *
 707          * @param array $params Operation parameters
 708          * @return StatusValue
 709          * @since 1.20
 710          */
 711         final public function quickCreate( array $params ) {
 712                 return $this->doQuickOperation( [ 'op' => 'create' ] + $params );
 713         }
 714
 715         /**
 716          * Performs a single quick store operation.
 717          * This sets $params['op'] to 'store' and passes it to doQuickOperation().
 718          *
 719          * @see FileBackend::doQuickOperation()
 720          *
 721          * @param array $params Operation parameters
 722          * @return StatusValue
 723          * @since 1.20
 724          */
 725         final public function quickStore( array $params ) {
 726                 return $this->doQuickOperation( [ 'op' => 'store' ] + $params );
 727         }
 728
 729         /**
 730          * Performs a single quick copy operation.
 731          * This sets $params['op'] to 'copy' and passes it to doQuickOperation().
 732          *
 733          * @see FileBackend::doQuickOperation()
 734          *
 735          * @param array $params Operation parameters
 736          * @return StatusValue
 737          * @since 1.20
 738          */
 739         final public function quickCopy( array $params ) {
 740                 return $this->doQuickOperation( [ 'op' => 'copy' ] + $params );
 741         }
 742
 743         /**
 744          * Performs a single quick move operation.
 745          * This sets $params['op'] to 'move' and passes it to doQuickOperation().
 746          *
 747          * @see FileBackend::doQuickOperation()
 748          *
 749          * @param array $params Operation parameters
 750          * @return StatusValue
 751          * @since 1.20
 752          */
 753         final public function quickMove( array $params ) {
 754                 return $this->doQuickOperation( [ 'op' => 'move' ] + $params );
 755         }
 756
 757         /**
 758          * Performs a single quick delete operation.
 759          * This sets $params['op'] to 'delete' and passes it to doQuickOperation().
 760          *
 761          * @see FileBackend::doQuickOperation()
 762          *
 763          * @param array $params Operation parameters
 764          * @return StatusValue
 765          * @since 1.20
 766          */
 767         final public function quickDelete( array $params ) {
 768                 return $this->doQuickOperation( [ 'op' => 'delete' ] + $params );
 769         }
 770
 771         /**
 772          * Performs a single quick describe operation.
 773          * This sets $params['op'] to 'describe' and passes it to doQuickOperation().
 774          *
 775          * @see FileBackend::doQuickOperation()
 776          *
 777          * @param array $params Operation parameters
 778          * @return StatusValue
 779          * @since 1.21
 780          */
 781         final public function quickDescribe( array $params ) {
 782                 return $this->doQuickOperation( [ 'op' => 'describe' ] + $params );
 783         }
 784
 785         /**
 786          * Concatenate a list of storage files into a single file system file.
 787          * The target path should refer to a file that is already locked or
 788          * otherwise safe from modification from other processes. Normally,
 789          * the file will be a new temp file, which should be adequate.
 790          *
 791          * @param array $params Operation parameters, include:
 792          *   - srcs        : ordered source storage paths (e.g. chunk1, chunk2, ...)
 793          *   - dst         : file system path to 0-byte temp file
 794          *   - parallelize : try to do operations in parallel when possible
 795          * @return StatusValue
 796          */
 797         abstract public function concatenate( array $params );
 798
 799         /**
 800          * Prepare a storage directory for usage.
 801          * This will create any required containers and parent directories.
 802          * Backends using key/value stores only need to create the container.
 803          *
 804          * The 'noAccess' and 'noListing' parameters works the same as in secure(),
 805          * except they are only applied *if* the directory/container had to be created.
 806          * These flags should always be set for directories that have private files.
 807          * However, setting them is not guaranteed to actually do anything.
 808          * Additional server configuration may be needed to achieve the desired effect.
 809          *
 810          * @param array $params Parameters include:
 811          *   - dir            : storage directory
 812          *   - noAccess       : try to deny file access (since 1.20)
 813          *   - noListing      : try to deny file listing (since 1.20)
 814          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 815          * @return StatusValue
 816          */
 817         final public function prepare( array $params ) {
 818                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 819                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 820                 }
 821                 /** @noinspection PhpUnusedLocalVariableInspection */
 822                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 823                 return $this->doPrepare( $params );
 824         }
 825
 826         /**
 827          * @see FileBackend::prepare()
 828          * @param array $params
 829          * @return StatusValue
 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 publicly 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 = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 855                 return $this->doSecure( $params );
 856         }
 857
 858         /**
 859          * @see FileBackend::secure()
 860          * @param array $params
 861          * @return StatusValue
 862          */
 863         abstract protected function doSecure( array $params );
 864
 865         /**
 866          * Remove measures to block web access to a storage directory and
 867          * the container it belongs to. FS backends might remove .htaccess
 868          * files whereas key/value store backends might grant container
 869          * access to the storage user representing end-users in web requests.
 870          * This essentially can undo the result of secure() calls.
 871          *
 872          * This is not guaranteed to actually make files or listings publicly viewable.
 873          * Additional server configuration may be needed to achieve the desired effect.
 874          *
 875          * @param array $params Parameters include:
 876          *   - dir            : storage directory
 877          *   - access         : try to allow file access
 878          *   - listing        : try to allow file listing
 879          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 880          * @return StatusValue
 881          * @since 1.20
 882          */
 883         final public function publish( array $params ) {
 884                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 885                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 886                 }
 887                 /** @noinspection PhpUnusedLocalVariableInspection */
 888                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 889                 return $this->doPublish( $params );
 890         }
 891
 892         /**
 893          * @see FileBackend::publish()
 894          * @param array $params
 895          * @return StatusValue
 896          */
 897         abstract protected function doPublish( array $params );
 898
 899         /**
 900          * Delete a storage directory if it is empty.
 901          * Backends using key/value stores may do nothing unless the directory
 902          * is that of an empty container, in which case it will be deleted.
 903          *
 904          * @param array $params Parameters include:
 905          *   - dir            : storage directory
 906          *   - recursive      : recursively delete empty subdirectories first (since 1.20)
 907          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 908          * @return StatusValue
 909          */
 910         final public function clean( array $params ) {
 911                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 912                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 913                 }
 914                 /** @noinspection PhpUnusedLocalVariableInspection */
 915                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 916                 return $this->doClean( $params );
 917         }
 918
 919         /**
 920          * @see FileBackend::clean()
 921          * @param array $params
 922          * @return StatusValue
 923          */
 924         abstract protected function doClean( array $params );
 925
 926         /**
 927          * Check if a file exists at a storage path in the backend.
 928          * This returns false if only a directory exists at the path.
 929          *
 930          * @param array $params Parameters include:
 931          *   - src    : source storage path
 932          *   - latest : use the latest available data
 933          * @return bool|null Returns null on failure
 934          */
 935         abstract public function fileExists( array $params );
 936
 937         /**
 938          * Get the last-modified timestamp of the file at a storage path.
 939          *
 940          * @param array $params Parameters include:
 941          *   - src    : source storage path
 942          *   - latest : use the latest available data
 943          * @return string|bool TS_MW timestamp or false on failure
 944          */
 945         abstract public function getFileTimestamp( array $params );
 946
 947         /**
 948          * Get the contents of a file at a storage path in the backend.
 949          * This should be avoided for potentially large files.
 950          *
 951          * @param array $params Parameters include:
 952          *   - src    : source storage path
 953          *   - latest : use the latest available data
 954          * @return string|bool Returns false on failure
 955          */
 956         final public function getFileContents( array $params ) {
 957                 $contents = $this->getFileContentsMulti(
 958                         [ 'srcs' => [ $params['src'] ] ] + $params );
 959
 960                 return $contents[$params['src']];
 961         }
 962
 963         /**
 964          * Like getFileContents() except it takes an array of storage paths
 965          * and returns a map of storage paths to strings (or null on failure).
 966          * The map keys (paths) are in the same order as the provided list of paths.
 967          *
 968          * @see FileBackend::getFileContents()
 969          *
 970          * @param array $params Parameters include:
 971          *   - srcs        : list of source storage paths
 972          *   - latest      : use the latest available data
 973          *   - parallelize : try to do operations in parallel when possible
 974          * @return array Map of (path name => string or false on failure)
 975          * @since 1.20
 976          */
 977         abstract public function getFileContentsMulti( array $params );
 978
 979         /**
 980          * Get metadata about a file at a storage path in the backend.
 981          * If the file does not exist, then this returns false.
 982          * Otherwise, the result is an associative array that includes:
 983          *   - headers  : map of HTTP headers used for GET/HEAD requests (name => value)
 984          *   - metadata : map of file metadata (name => value)
 985          * Metadata keys and headers names will be returned in all lower-case.
 986          * Additional values may be included for internal use only.
 987          *
 988          * Use FileBackend::hasFeatures() to check how well this is supported.
 989          *
 990          * @param array $params
 991          * $params include:
 992          *   - src    : source storage path
 993          *   - latest : use the latest available data
 994          * @return array|bool Returns false on failure
 995          * @since 1.23
 996          */
 997         abstract public function getFileXAttributes( array $params );
 998
 999         /**
1000          * Get the size (bytes) of a file at a storage path in the backend.
1001          *
1002          * @param array $params Parameters include:
1003          *   - src    : source storage path
1004          *   - latest : use the latest available data
1005          * @return int|bool Returns false on failure
1006          */
1007         abstract public function getFileSize( array $params );
1008
1009         /**
1010          * Get quick information about a file at a storage path in the backend.
1011          * If the file does not exist, then this returns false.
1012          * Otherwise, the result is an associative array that includes:
1013          *   - mtime  : the last-modified timestamp (TS_MW)
1014          *   - size   : the file size (bytes)
1015          * Additional values may be included for internal use only.
1016          *
1017          * @param array $params Parameters include:
1018          *   - src    : source storage path
1019          *   - latest : use the latest available data
1020          * @return array|bool|null Returns null on failure
1021          */
1022         abstract public function getFileStat( array $params );
1023
1024         /**
1025          * Get a SHA-1 hash of the file at a storage path in the backend.
1026          *
1027          * @param array $params Parameters include:
1028          *   - src    : source storage path
1029          *   - latest : use the latest available data
1030          * @return string|bool Hash string or false on failure
1031          */
1032         abstract public function getFileSha1Base36( array $params );
1033
1034         /**
1035          * Get the properties of the file at a storage path in the backend.
1036          * This gives the result of FSFile::getProps() on a local copy of the file.
1037          *
1038          * @param array $params Parameters include:
1039          *   - src    : source storage path
1040          *   - latest : use the latest available data
1041          * @return array Returns FSFile::placeholderProps() on failure
1042          */
1043         abstract public function getFileProps( array $params );
1044
1045         /**
1046          * Stream the file at a storage path in the backend.
1047          *
1048          * If the file does not exists, an HTTP 404 error will be given.
1049          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
1050          * will be sent if streaming began, while none will be sent otherwise.
1051          * Implementations should flush the output buffer before sending data.
1052          *
1053          * @param array $params Parameters include:
1054          *   - src      : source storage path
1055          *   - headers  : list of additional HTTP headers to send if the file exists
1056          *   - options  : HTTP request header map with lower case keys (since 1.28). Supports:
1057          *                range             : format is "bytes=(\d*-\d*)"
1058          *                if-modified-since : format is an HTTP date
1059          *   - headless : only include the body (and headers from "headers") (since 1.28)
1060          *   - latest   : use the latest available data
1061          *   - allowOB  : preserve any output buffers (since 1.28)
1062          * @return StatusValue
1063          */
1064         abstract public function streamFile( array $params );
1065
1066         /**
1067          * Returns a file system file, identical to the file at a storage path.
1068          * The file returned is either:
1069          *   - a) A local copy of the file at a storage path in the backend.
1070          *        The temporary copy will have the same extension as the source.
1071          *   - b) An original of the file at a storage path in the backend.
1072          * Temporary files may be purged when the file object falls out of scope.
1073          *
1074          * Write operations should *never* be done on this file as some backends
1075          * may do internal tracking or may be instances of FileBackendMultiWrite.
1076          * In that latter case, there are copies of the file that must stay in sync.
1077          * Additionally, further calls to this function may return the same file.
1078          *
1079          * @param array $params Parameters include:
1080          *   - src    : source storage path
1081          *   - latest : use the latest available data
1082          * @return FSFile|null Returns null on failure
1083          */
1084         final public function getLocalReference( array $params ) {
1085                 $fsFiles = $this->getLocalReferenceMulti(
1086                         [ 'srcs' => [ $params['src'] ] ] + $params );
1087
1088                 return $fsFiles[$params['src']];
1089         }
1090
1091         /**
1092          * Like getLocalReference() except it takes an array of storage paths
1093          * and returns a map of storage paths to FSFile objects (or null on failure).
1094          * The map keys (paths) are in the same order as the provided list of paths.
1095          *
1096          * @see FileBackend::getLocalReference()
1097          *
1098          * @param array $params Parameters include:
1099          *   - srcs        : list of source storage paths
1100          *   - latest      : use the latest available data
1101          *   - parallelize : try to do operations in parallel when possible
1102          * @return array Map of (path name => FSFile or null on failure)
1103          * @since 1.20
1104          */
1105         abstract public function getLocalReferenceMulti( array $params );
1106
1107         /**
1108          * Get a local copy on disk of the file at a storage path in the backend.
1109          * The temporary copy will have the same file extension as the source.
1110          * Temporary files may be purged when the file object falls out of scope.
1111          *
1112          * @param array $params Parameters include:
1113          *   - src    : source storage path
1114          *   - latest : use the latest available data
1115          * @return TempFSFile|null Returns null on failure
1116          */
1117         final public function getLocalCopy( array $params ) {
1118                 $tmpFiles = $this->getLocalCopyMulti(
1119                         [ 'srcs' => [ $params['src'] ] ] + $params );
1120
1121                 return $tmpFiles[$params['src']];
1122         }
1123
1124         /**
1125          * Like getLocalCopy() except it takes an array of storage paths and
1126          * returns a map of storage paths to TempFSFile objects (or null on failure).
1127          * The map keys (paths) are in the same order as the provided list of paths.
1128          *
1129          * @see FileBackend::getLocalCopy()
1130          *
1131          * @param array $params Parameters include:
1132          *   - srcs        : list of source storage paths
1133          *   - latest      : use the latest available data
1134          *   - parallelize : try to do operations in parallel when possible
1135          * @return array Map of (path name => TempFSFile or null on failure)
1136          * @since 1.20
1137          */
1138         abstract public function getLocalCopyMulti( array $params );
1139
1140         /**
1141          * Return an HTTP URL to a given file that requires no authentication to use.
1142          * The URL may be pre-authenticated (via some token in the URL) and temporary.
1143          * This will return null if the backend cannot make an HTTP URL for the file.
1144          *
1145          * This is useful for key/value stores when using scripts that seek around
1146          * large files and those scripts (and the backend) support HTTP Range headers.
1147          * Otherwise, one would need to use getLocalReference(), which involves loading
1148          * the entire file on to local disk.
1149          *
1150          * @param array $params Parameters include:
1151          *   - src : source storage path
1152          *   - ttl : lifetime (seconds) if pre-authenticated; default is 1 day
1153          * @return string|null
1154          * @since 1.21
1155          */
1156         abstract public function getFileHttpUrl( array $params );
1157
1158         /**
1159          * Check if a directory exists at a given storage path.
1160          * Backends using key/value stores will check if the path is a
1161          * virtual directory, meaning there are files under the given directory.
1162          *
1163          * Storage backends with eventual consistency might return stale data.
1164          *
1165          * @param array $params Parameters include:
1166          *   - dir : storage directory
1167          * @return bool|null Returns null on failure
1168          * @since 1.20
1169          */
1170         abstract public function directoryExists( array $params );
1171
1172         /**
1173          * Get an iterator to list *all* directories under a storage directory.
1174          * If the directory is of the form "mwstore://backend/container",
1175          * then all directories in the container will be listed.
1176          * If the directory is of form "mwstore://backend/container/dir",
1177          * then all directories directly under that directory will be listed.
1178          * Results will be storage directories relative to the given directory.
1179          *
1180          * Storage backends with eventual consistency might return stale data.
1181          *
1182          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1183          *
1184          * @param array $params Parameters include:
1185          *   - dir     : storage directory
1186          *   - topOnly : only return direct child dirs of the directory
1187          * @return Traversable|array|null Returns null on failure
1188          * @since 1.20
1189          */
1190         abstract public function getDirectoryList( array $params );
1191
1192         /**
1193          * Same as FileBackend::getDirectoryList() except only lists
1194          * directories that are immediately under the given directory.
1195          *
1196          * Storage backends with eventual consistency might return stale data.
1197          *
1198          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1199          *
1200          * @param array $params Parameters include:
1201          *   - dir : storage directory
1202          * @return Traversable|array|null Returns null on failure
1203          * @since 1.20
1204          */
1205         final public function getTopDirectoryList( array $params ) {
1206                 return $this->getDirectoryList( [ 'topOnly' => true ] + $params );
1207         }
1208
1209         /**
1210          * Get an iterator to list *all* stored files under a storage directory.
1211          * If the directory is of the form "mwstore://backend/container",
1212          * then all files in the container will be listed.
1213          * If the directory is of form "mwstore://backend/container/dir",
1214          * then all files under that directory will be listed.
1215          * Results will be storage paths relative to the given directory.
1216          *
1217          * Storage backends with eventual consistency might return stale data.
1218          *
1219          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1220          *
1221          * @param array $params Parameters include:
1222          *   - dir        : storage directory
1223          *   - topOnly    : only return direct child files of the directory (since 1.20)
1224          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1225          * @return Traversable|array|null Returns null on failure
1226          */
1227         abstract public function getFileList( array $params );
1228
1229         /**
1230          * Same as FileBackend::getFileList() except only lists
1231          * files that are immediately under the given directory.
1232          *
1233          * Storage backends with eventual consistency might return stale data.
1234          *
1235          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1236          *
1237          * @param array $params Parameters include:
1238          *   - dir        : storage directory
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          * @since 1.20
1242          */
1243         final public function getTopFileList( array $params ) {
1244                 return $this->getFileList( [ 'topOnly' => true ] + $params );
1245         }
1246
1247         /**
1248          * Preload persistent file stat cache and property cache into in-process cache.
1249          * This should be used when stat calls will be made on a known list of a many files.
1250          *
1251          * @see FileBackend::getFileStat()
1252          *
1253          * @param array $paths Storage paths
1254          */
1255         abstract public function preloadCache( array $paths );
1256
1257         /**
1258          * Invalidate any in-process file stat and property cache.
1259          * If $paths is given, then only the cache for those files will be cleared.
1260          *
1261          * @see FileBackend::getFileStat()
1262          *
1263          * @param array|null $paths Storage paths (optional)
1264          */
1265         abstract public function clearCache( array $paths = null );
1266
1267         /**
1268          * Preload file stat information (concurrently if possible) into in-process cache.
1269          *
1270          * This should be used when stat calls will be made on a known list of a many files.
1271          * This does not make use of the persistent file stat cache.
1272          *
1273          * @see FileBackend::getFileStat()
1274          *
1275          * @param array $params Parameters include:
1276          *   - srcs        : list of source storage paths
1277          *   - latest      : use the latest available data
1278          * @return bool All requests proceeded without I/O errors (since 1.24)
1279          * @since 1.23
1280          */
1281         abstract public function preloadFileStat( array $params );
1282
1283         /**
1284          * Lock the files at the given storage paths in the backend.
1285          * This will either lock all the files or none (on failure).
1286          *
1287          * Callers should consider using getScopedFileLocks() instead.
1288          *
1289          * @param array $paths Storage paths
1290          * @param int $type LockManager::LOCK_* constant
1291          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.24)
1292          * @return StatusValue
1293          */
1294         final public function lockFiles( array $paths, $type, $timeout = 0 ) {
1295                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1296
1297                 return $this->wrapStatus( $this->lockManager->lock( $paths, $type, $timeout ) );
1298         }
1299
1300         /**
1301          * Unlock the files at the given storage paths in the backend.
1302          *
1303          * @param array $paths Storage paths
1304          * @param int $type LockManager::LOCK_* constant
1305          * @return StatusValue
1306          */
1307         final public function unlockFiles( array $paths, $type ) {
1308                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1309
1310                 return $this->wrapStatus( $this->lockManager->unlock( $paths, $type ) );
1311         }
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          * On failure, the StatusValue object will be updated with errors.
1317          *
1318          * Once the return value goes out scope, the locks will be released and
1319          * the StatusValue updated. Unlock fatals will not change the StatusValue "OK" value.
1320          *
1321          * @see ScopedLock::factory()
1322          *
1323          * @param array $paths List of storage paths or map of lock types to path lists
1324          * @param int|string $type LockManager::LOCK_* constant or "mixed"
1325          * @param StatusValue $status StatusValue to update on lock/unlock
1326          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.24)
1327          * @return ScopedLock|null Returns null on failure
1328          */
1329         final public function getScopedFileLocks(
1330                 array $paths, $type, StatusValue $status, $timeout = 0
1331         ) {
1332                 if ( $type === 'mixed' ) {
1333                         foreach ( $paths as &$typePaths ) {
1334                                 $typePaths = array_map( 'FileBackend::normalizeStoragePath', $typePaths );
1335                         }
1336                 } else {
1337                         $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1338                 }
1339
1340                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status, $timeout );
1341         }
1342
1343         /**
1344          * Get an array of scoped locks needed for a batch of file operations.
1345          *
1346          * Normally, FileBackend::doOperations() handles locking, unless
1347          * the 'nonLocking' param is passed in. This function is useful if you
1348          * want the files to be locked for a broader scope than just when the
1349          * files are changing. For example, if you need to update DB metadata,
1350          * you may want to keep the files locked until finished.
1351          *
1352          * @see FileBackend::doOperations()
1353          *
1354          * @param array $ops List of file operations to FileBackend::doOperations()
1355          * @param StatusValue $status StatusValue to update on lock/unlock
1356          * @return ScopedLock|null
1357          * @since 1.20
1358          */
1359         abstract public function getScopedLocksForOps( array $ops, StatusValue $status );
1360
1361         /**
1362          * Get the root storage path of this backend.
1363          * All container paths are "subdirectories" of this path.
1364          *
1365          * @return string Storage path
1366          * @since 1.20
1367          */
1368         final public function getRootStoragePath() {
1369                 return "mwstore://{$this->name}";
1370         }
1371
1372         /**
1373          * Get the storage path for the given container for this backend
1374          *
1375          * @param string $container Container name
1376          * @return string Storage path
1377          * @since 1.21
1378          */
1379         final public function getContainerStoragePath( $container ) {
1380                 return $this->getRootStoragePath() . "/{$container}";
1381         }
1382
1383         /**
1384          * Get the file journal object for this backend
1385          *
1386          * @return FileJournal
1387          */
1388         final public function getJournal() {
1389                 return $this->fileJournal;
1390         }
1391
1392         /**
1393          * Convert FSFile 'src' paths to string paths (with an 'srcRef' field set to the FSFile)
1394          *
1395          * The 'srcRef' field keeps any TempFSFile objects in scope for the backend to have it
1396          * around as long it needs (which may vary greatly depending on configuration)
1397          *
1398          * @param array $ops File operation batch for FileBaclend::doOperations()
1399          * @return array File operation batch
1400          */
1401         protected function resolveFSFileObjects( array $ops ) {
1402                 foreach ( $ops as &$op ) {
1403                         $src = $op['src'] ?? null;
1404                         if ( $src instanceof FSFile ) {
1405                                 $op['srcRef'] = $src;
1406                                 $op['src'] = $src->getPath();
1407                         }
1408                 }
1409                 unset( $op );
1410
1411                 return $ops;
1412         }
1413
1414         /**
1415          * Check if a given path is a "mwstore://" path.
1416          * This does not do any further validation or any existence checks.
1417          *
1418          * @param string $path
1419          * @return bool
1420          */
1421         final public static function isStoragePath( $path ) {
1422                 return ( strpos( $path, 'mwstore://' ) === 0 );
1423         }
1424
1425         /**
1426          * Split a storage path into a backend name, a container name,
1427          * and a relative file path. The relative path may be the empty string.
1428          * This does not do any path normalization or traversal checks.
1429          *
1430          * @param string $storagePath
1431          * @return array (backend, container, rel object) or (null, null, null)
1432          */
1433         final public static function splitStoragePath( $storagePath ) {
1434                 if ( self::isStoragePath( $storagePath ) ) {
1435                         // Remove the "mwstore://" prefix and split the path
1436                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
1437                         if ( count( $parts ) >= 2 && $parts[0] != '' && $parts[1] != '' ) {
1438                                 if ( count( $parts ) == 3 ) {
1439                                         return $parts; // e.g. "backend/container/path"
1440                                 } else {
1441                                         return [ $parts[0], $parts[1], '' ]; // e.g. "backend/container"
1442                                 }
1443                         }
1444                 }
1445
1446                 return [ null, null, null ];
1447         }
1448
1449         /**
1450          * Normalize a storage path by cleaning up directory separators.
1451          * Returns null if the path is not of the format of a valid storage path.
1452          *
1453          * @param string $storagePath
1454          * @return string|null
1455          */
1456         final public static function normalizeStoragePath( $storagePath ) {
1457                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
1458                 if ( $relPath !== null ) { // must be for this backend
1459                         $relPath = self::normalizeContainerPath( $relPath );
1460                         if ( $relPath !== null ) {
1461                                 return ( $relPath != '' )
1462                                         ? "mwstore://{$backend}/{$container}/{$relPath}"
1463                                         : "mwstore://{$backend}/{$container}";
1464                         }
1465                 }
1466
1467                 return null;
1468         }
1469
1470         /**
1471          * Get the parent storage directory of a storage path.
1472          * This returns a path like "mwstore://backend/container",
1473          * "mwstore://backend/container/...", or null if there is no parent.
1474          *
1475          * @param string $storagePath
1476          * @return string|null
1477          */
1478         final public static function parentStoragePath( $storagePath ) {
1479                 $storagePath = dirname( $storagePath );
1480                 list( , , $rel ) = self::splitStoragePath( $storagePath );
1481
1482                 return ( $rel === null ) ? null : $storagePath;
1483         }
1484
1485         /**
1486          * Get the final extension from a storage or FS path
1487          *
1488          * @param string $path
1489          * @param string $case One of (rawcase, uppercase, lowercase) (since 1.24)
1490          * @return string
1491          */
1492         final public static function extensionFromPath( $path, $case = 'lowercase' ) {
1493                 $i = strrpos( $path, '.' );
1494                 $ext = $i ? substr( $path, $i + 1 ) : '';
1495
1496                 if ( $case === 'lowercase' ) {
1497                         $ext = strtolower( $ext );
1498                 } elseif ( $case === 'uppercase' ) {
1499                         $ext = strtoupper( $ext );
1500                 }
1501
1502                 return $ext;
1503         }
1504
1505         /**
1506          * Check if a relative path has no directory traversals
1507          *
1508          * @param string $path
1509          * @return bool
1510          * @since 1.20
1511          */
1512         final public static function isPathTraversalFree( $path ) {
1513                 return ( self::normalizeContainerPath( $path ) !== null );
1514         }
1515
1516         /**
1517          * Build a Content-Disposition header value per RFC 6266.
1518          *
1519          * @param string $type One of (attachment, inline)
1520          * @param string $filename Suggested file name (should not contain slashes)
1521          * @throws FileBackendError
1522          * @return string
1523          * @since 1.20
1524          */
1525         final public static function makeContentDisposition( $type, $filename = '' ) {
1526                 $parts = [];
1527
1528                 $type = strtolower( $type );
1529                 if ( !in_array( $type, [ 'inline', 'attachment' ] ) ) {
1530                         throw new InvalidArgumentException( "Invalid Content-Disposition type '$type'." );
1531                 }
1532                 $parts[] = $type;
1533
1534                 if ( strlen( $filename ) ) {
1535                         $parts[] = "filename*=UTF-8''" . rawurlencode( basename( $filename ) );
1536                 }
1537
1538                 return implode( ';', $parts );
1539         }
1540
1541         /**
1542          * Validate and normalize a relative storage path.
1543          * Null is returned if the path involves directory traversal.
1544          * Traversal is insecure for FS backends and broken for others.
1545          *
1546          * This uses the same traversal protection as Title::secureAndSplit().
1547          *
1548          * @param string $path Storage path relative to a container
1549          * @return string|null
1550          */
1551         final protected static function normalizeContainerPath( $path ) {
1552                 // Normalize directory separators
1553                 $path = strtr( $path, '\\', '/' );
1554                 // Collapse any consecutive directory separators
1555                 $path = preg_replace( '![/]{2,}!', '/', $path );
1556                 // Remove any leading directory separator
1557                 $path = ltrim( $path, '/' );
1558                 // Use the same traversal protection as Title::secureAndSplit()
1559                 if ( strpos( $path, '.' ) !== false ) {
1560                         if (
1561                                 $path === '.' ||
1562                                 $path === '..' ||
1563                                 strpos( $path, './' ) === 0 ||
1564                                 strpos( $path, '../' ) === 0 ||
1565                                 strpos( $path, '/./' ) !== false ||
1566                                 strpos( $path, '/../' ) !== false
1567                         ) {
1568                                 return null;
1569                         }
1570                 }
1571
1572                 return $path;
1573         }
1574
1575         /**
1576          * Yields the result of the status wrapper callback on either:
1577          *   - StatusValue::newGood() if this method is called without parameters
1578          *   - StatusValue::newFatal() with all parameters to this method if passed in
1579          *
1580          * @param string ...$args
1581          * @return StatusValue
1582          */
1583         final protected function newStatus( ...$args ) {
1584                 if ( count( $args ) ) {
1585                         $sv = StatusValue::newFatal( ...$args );
1586                 } else {
1587                         $sv = StatusValue::newGood();
1588                 }
1589
1590                 return $this->wrapStatus( $sv );
1591         }
1592
1593         /**
1594          * @param StatusValue $sv
1595          * @return StatusValue Modified status or StatusValue subclass
1596          */
1597         final protected function wrapStatus( StatusValue $sv ) {
1598                 return $this->statusWrapper ? call_user_func( $this->statusWrapper, $sv ) : $sv;
1599         }
1600
1601         /**
1602          * @param string $section
1603          * @return ScopedCallback|null
1604          */
1605         protected function scopedProfileSection( $section ) {
1606                 return $this->profiler ? ( $this->profiler )( $section ) : null;
1607         }
1608
1609         protected function resetOutputBuffer() {
1610                 while ( ob_get_status() ) {
1611                         if ( !ob_end_clean() ) {
1612                                 // Could not remove output buffer handler; abort now
1613                                 // to avoid getting in some kind of infinite loop.
1614                                 break;
1615                         }
1616                 }
1617         }
1618 }