includes/filerepo/backend/FileBackend.php

   1 <?php
   2 /**
   3  * @defgroup FileBackend File backend
   4  * @ingroup  FileRepo
   5  *
   6  * File backend is used to interact with file storage systems,
   7  * such as the local file system, NFS, or cloud storage systems.
   8  */
   9
  10 /**
  11  * @file
  12  * @ingroup FileBackend
  13  * @author Aaron Schulz
  14  */
  15
  16 /**
  17  * @brief Base class for all file backend classes (including multi-write backends).
  18  *
  19  * This class defines the methods as abstract that subclasses must implement.
  20  * Outside callers can assume that all backends will have these functions.
  21  *
  22  * All "storage paths" are of the format "mwstore://<backend>/<container>/<path>".
  23  * The <path> portion is a relative path that uses UNIX file system (FS) notation,
  24  * though any particular backend may not actually be using a local filesystem.
  25  * Therefore, the relative paths are only virtual.
  26  *
  27  * Backend contents are stored under wiki-specific container names by default.
  28  * For legacy reasons, this has no effect for the FS backend class, and per-wiki
  29  * segregation must be done by setting the container paths appropriately.
  30  *
  31  * FS-based backends are somewhat more restrictive due to the existence of real
  32  * directory files; a regular file cannot have the same name as a directory. Other
  33  * backends with virtual directories may not have this limitation. Callers should
  34  * store files in such a way that no files and directories are under the same path.
  35  *
  36  * Methods should avoid throwing exceptions at all costs.
  37  * As a corollary, external dependencies should be kept to a minimum.
  38  *
  39  * @ingroup FileBackend
  40  * @since 1.19
  41  */
  42 abstract class FileBackend {
  43         protected $name; // string; unique backend name
  44         protected $wikiId; // string; unique wiki name
  45         protected $readOnly; // string; read-only explanation message
  46         /** @var LockManager */
  47         protected $lockManager;
  48         /** @var FileJournal */
  49         protected $fileJournal;
  50
  51         /**
  52          * Create a new backend instance from configuration.
  53          * This should only be called from within FileBackendGroup.
  54          *
  55          * $config includes:
  56          *     'name'        : The unique name of this backend.
  57          *                     This should consist of alphanumberic, '-', and '_' characters.
  58          *                     This name should not be changed after use.
  59          *     'wikiId'      : Prefix to container names that is unique to this wiki.
  60          *                     It should only consist of alphanumberic, '-', and '_' characters.
  61          *     'lockManager' : Registered name of a file lock manager to use.
  62          *     'fileJournal' : File journal configuration; see FileJournal::factory().
  63          *                     Journals simply log changes to files stored in the backend.
  64          *     'readOnly'    : Write operations are disallowed if this is a non-empty string.
  65          *                     It should be an explanation for the backend being read-only.
  66          *
  67          * @param $config Array
  68          */
  69         public function __construct( array $config ) {
  70                 $this->name = $config['name'];
  71                 if ( !preg_match( '!^[a-zA-Z0-9-_]{1,255}$!', $this->name ) ) {
  72                         throw new MWException( "Backend name `{$this->name}` is invalid." );
  73                 }
  74                 $this->wikiId = isset( $config['wikiId'] )
  75                         ? $config['wikiId']
  76                         : wfWikiID(); // e.g. "my_wiki-en_"
  77                 $this->lockManager = ( $config['lockManager'] instanceof LockManager )
  78                         ? $config['lockManager']
  79                         : LockManagerGroup::singleton()->get( $config['lockManager'] );
  80                 $this->fileJournal = isset( $config['fileJournal'] )
  81                         ? FileJournal::factory( $config['fileJournal'], $this->name )
  82                         : FileJournal::factory( array( 'class' => 'NullFileJournal' ), $this->name );
  83                 $this->readOnly = isset( $config['readOnly'] )
  84                         ? (string)$config['readOnly']
  85                         : '';
  86         }
  87
  88         /**
  89          * Get the unique backend name.
  90          * We may have multiple different backends of the same type.
  91          * For example, we can have two Swift backends using different proxies.
  92          *
  93          * @return string
  94          */
  95         final public function getName() {
  96                 return $this->name;
  97         }
  98
  99         /**
 100          * Check if this backend is read-only
 101          *
 102          * @return bool
 103          */
 104         final public function isReadOnly() {
 105                 return ( $this->readOnly != '' );
 106         }
 107
 108         /**
 109          * Get an explanatory message if this backend is read-only
 110          *
 111          * @return string|bool Returns false if the backend is not read-only
 112          */
 113         final public function getReadOnlyReason() {
 114                 return ( $this->readOnly != '' ) ? $this->readOnly : false;
 115         }
 116
 117         /**
 118          * This is the main entry point into the backend for write operations.
 119          * Callers supply an ordered list of operations to perform as a transaction.
 120          * Files will be locked, the stat cache cleared, and then the operations attempted.
 121          * If any serious errors occur, all attempted operations will be rolled back.
 122          *
 123          * $ops is an array of arrays. The outer array holds a list of operations.
 124          * Each inner array is a set of key value pairs that specify an operation.
 125          *
 126          * Supported operations and their parameters:
 127          * a) Create a new file in storage with the contents of a string
 128          *     array(
 129          *         'op'                  => 'create',
 130          *         'dst'                 => <storage path>,
 131          *         'content'             => <string of new file contents>,
 132          *         'overwrite'           => <boolean>,
 133          *         'overwriteSame'       => <boolean>
 134          *     )
 135          * b) Copy a file system file into storage
 136          *     array(
 137          *         'op'                  => 'store',
 138          *         'src'                 => <file system path>,
 139          *         'dst'                 => <storage path>,
 140          *         'overwrite'           => <boolean>,
 141          *         'overwriteSame'       => <boolean>
 142          *     )
 143          * c) Copy a file within storage
 144          *     array(
 145          *         'op'                  => 'copy',
 146          *         'src'                 => <storage path>,
 147          *         'dst'                 => <storage path>,
 148          *         'overwrite'           => <boolean>,
 149          *         'overwriteSame'       => <boolean>
 150          *     )
 151          * d) Move a file within storage
 152          *     array(
 153          *         'op'                  => 'move',
 154          *         'src'                 => <storage path>,
 155          *         'dst'                 => <storage path>,
 156          *         'overwrite'           => <boolean>,
 157          *         'overwriteSame'       => <boolean>
 158          *     )
 159          * e) Delete a file within storage
 160          *     array(
 161          *         'op'                  => 'delete',
 162          *         'src'                 => <storage path>,
 163          *         'ignoreMissingSource' => <boolean>
 164          *     )
 165          * f) Do nothing (no-op)
 166          *     array(
 167          *         'op'                  => 'null',
 168          *     )
 169          *
 170          * Boolean flags for operations (operation-specific):
 171          * 'ignoreMissingSource' : The operation will simply succeed and do
 172          *                         nothing if the source file does not exist.
 173          * 'overwrite'           : Any destination file will be overwritten.
 174          * 'overwriteSame'       : An error will not be given if a file already
 175          *                         exists at the destination that has the same
 176          *                         contents as the new contents to be written there.
 177          *
 178          * $opts is an associative of boolean flags, including:
 179          * 'force'               : Errors that would normally cause a rollback do not.
 180          *                         The remaining operations are still attempted if any fail.
 181          * 'nonLocking'          : No locks are acquired for the operations.
 182          *                         This can increase performance for non-critical writes.
 183          *                         This has no effect unless the 'force' flag is set.
 184          * 'allowStale'          : Don't require the latest available data.
 185          *                         This can increase performance for non-critical writes.
 186          *                         This has no effect unless the 'force' flag is set.
 187          * 'nonJournaled'        : Don't log this operation batch in the file journal.
 188          *                         This limits the ability of recovery scripts.
 189          *
 190          * Remarks on locking:
 191          * File system paths given to operations should refer to files that are
 192          * already locked or otherwise safe from modification from other processes.
 193          * Normally these files will be new temp files, which should be adequate.
 194          *
 195          * Return value:
 196          * This returns a Status, which contains all warnings and fatals that occured
 197          * during the operation. The 'failCount', 'successCount', and 'success' members
 198          * will reflect each operation attempted. The status will be "OK" unless:
 199          *     a) unexpected operation errors occurred (network partitions, disk full...)
 200          *     b) significant operation errors occured and 'force' was not set
 201          *
 202          * @param $ops Array List of operations to execute in order
 203          * @param $opts Array Batch operation options
 204          * @return Status
 205          */
 206         final public function doOperations( array $ops, array $opts = array() ) {
 207                 if ( $this->isReadOnly() ) {
 208                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 209                 }
 210                 if ( empty( $opts['force'] ) ) { // sanity
 211                         unset( $opts['nonLocking'] );
 212                         unset( $opts['allowStale'] );
 213                 }
 214                 return $this->doOperationsInternal( $ops, $opts );
 215         }
 216
 217         /**
 218          * @see FileBackend::doOperations()
 219          */
 220         abstract protected function doOperationsInternal( array $ops, array $opts );
 221
 222         /**
 223          * Same as doOperations() except it takes a single operation.
 224          * If you are doing a batch of operations that should either
 225          * all succeed or all fail, then use that function instead.
 226          *
 227          * @see FileBackend::doOperations()
 228          *
 229          * @param $op Array Operation
 230          * @param $opts Array Operation options
 231          * @return Status
 232          */
 233         final public function doOperation( array $op, array $opts = array() ) {
 234                 return $this->doOperations( array( $op ), $opts );
 235         }
 236
 237         /**
 238          * Performs a single create operation.
 239          * This sets $params['op'] to 'create' and passes it to doOperation().
 240          *
 241          * @see FileBackend::doOperation()
 242          *
 243          * @param $params Array Operation parameters
 244          * @param $opts Array Operation options
 245          * @return Status
 246          */
 247         final public function create( array $params, array $opts = array() ) {
 248                 $params['op'] = 'create';
 249                 return $this->doOperation( $params, $opts );
 250         }
 251
 252         /**
 253          * Performs a single store operation.
 254          * This sets $params['op'] to 'store' and passes it to doOperation().
 255          *
 256          * @see FileBackend::doOperation()
 257          *
 258          * @param $params Array Operation parameters
 259          * @param $opts Array Operation options
 260          * @return Status
 261          */
 262         final public function store( array $params, array $opts = array() ) {
 263                 $params['op'] = 'store';
 264                 return $this->doOperation( $params, $opts );
 265         }
 266
 267         /**
 268          * Performs a single copy operation.
 269          * This sets $params['op'] to 'copy' and passes it to doOperation().
 270          *
 271          * @see FileBackend::doOperation()
 272          *
 273          * @param $params Array Operation parameters
 274          * @param $opts Array Operation options
 275          * @return Status
 276          */
 277         final public function copy( array $params, array $opts = array() ) {
 278                 $params['op'] = 'copy';
 279                 return $this->doOperation( $params, $opts );
 280         }
 281
 282         /**
 283          * Performs a single move operation.
 284          * This sets $params['op'] to 'move' and passes it to doOperation().
 285          *
 286          * @see FileBackend::doOperation()
 287          *
 288          * @param $params Array Operation parameters
 289          * @param $opts Array Operation options
 290          * @return Status
 291          */
 292         final public function move( array $params, array $opts = array() ) {
 293                 $params['op'] = 'move';
 294                 return $this->doOperation( $params, $opts );
 295         }
 296
 297         /**
 298          * Performs a single delete operation.
 299          * This sets $params['op'] to 'delete' and passes it to doOperation().
 300          *
 301          * @see FileBackend::doOperation()
 302          *
 303          * @param $params Array Operation parameters
 304          * @param $opts Array Operation options
 305          * @return Status
 306          */
 307         final public function delete( array $params, array $opts = array() ) {
 308                 $params['op'] = 'delete';
 309                 return $this->doOperation( $params, $opts );
 310         }
 311
 312         /**
 313          * Concatenate a list of storage files into a single file system file.
 314          * The target path should refer to a file that is already locked or
 315          * otherwise safe from modification from other processes. Normally,
 316          * the file will be a new temp file, which should be adequate.
 317          * $params include:
 318          *     srcs          : ordered source storage paths (e.g. chunk1, chunk2, ...)
 319          *     dst           : file system path to 0-byte temp file
 320          *
 321          * @param $params Array Operation parameters
 322          * @return Status
 323          */
 324         abstract public function concatenate( array $params );
 325
 326         /**
 327          * Prepare a storage directory for usage.
 328          * This will create any required containers and parent directories.
 329          * Backends using key/value stores only need to create the container.
 330          *
 331          * $params include:
 332          *     dir : storage directory
 333          *
 334          * @param $params Array
 335          * @return Status
 336          */
 337         final public function prepare( array $params ) {
 338                 if ( $this->isReadOnly() ) {
 339                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 340                 }
 341                 return $this->doPrepare( $params );
 342         }
 343
 344         /**
 345          * @see FileBackend::prepare()
 346          */
 347         abstract protected function doPrepare( array $params );
 348
 349         /**
 350          * Take measures to block web access to a storage directory and
 351          * the container it belongs to. FS backends might add .htaccess
 352          * files whereas key/value store backends might restrict container
 353          * access to the auth user that represents end-users in web request.
 354          * This is not guaranteed to actually do anything.
 355          *
 356          * $params include:
 357          *     dir       : storage directory
 358          *     noAccess  : try to deny file access
 359          *     noListing : try to deny file listing
 360          *
 361          * @param $params Array
 362          * @return Status
 363          */
 364         final public function secure( array $params ) {
 365                 if ( $this->isReadOnly() ) {
 366                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 367                 }
 368                 $status = $this->doPrepare( $params ); // dir must exist to restrict it
 369                 if ( $status->isOK() ) {
 370                         $status->merge( $this->doSecure( $params ) );
 371                 }
 372                 return $status;
 373         }
 374
 375         /**
 376          * @see FileBackend::secure()
 377          */
 378         abstract protected function doSecure( array $params );
 379
 380         /**
 381          * Delete a storage directory if it is empty.
 382          * Backends using key/value stores may do nothing unless the directory
 383          * is that of an empty container, in which case it should be deleted.
 384          *
 385          * $params include:
 386          *     dir : storage directory
 387          *
 388          * @param $params Array
 389          * @return Status
 390          */
 391         final public function clean( array $params ) {
 392                 if ( $this->isReadOnly() ) {
 393                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 394                 }
 395                 return $this->doClean( $params );
 396         }
 397
 398         /**
 399          * @see FileBackend::clean()
 400          */
 401         abstract protected function doClean( array $params );
 402
 403         /**
 404          * Check if a file exists at a storage path in the backend.
 405          * This returns false if only a directory exists at the path.
 406          *
 407          * $params include:
 408          *     src    : source storage path
 409          *     latest : use the latest available data
 410          *
 411          * @param $params Array
 412          * @return bool|null Returns null on failure
 413          */
 414         abstract public function fileExists( array $params );
 415
 416         /**
 417          * Get the last-modified timestamp of the file at a storage path.
 418          *
 419          * $params include:
 420          *     src    : source storage path
 421          *     latest : use the latest available data
 422          *
 423          * @param $params Array
 424          * @return string|bool TS_MW timestamp or false on failure
 425          */
 426         abstract public function getFileTimestamp( array $params );
 427
 428         /**
 429          * Get the contents of a file at a storage path in the backend.
 430          * This should be avoided for potentially large files.
 431          *
 432          * $params include:
 433          *     src    : source storage path
 434          *     latest : use the latest available data
 435          *
 436          * @param $params Array
 437          * @return string|bool Returns false on failure
 438          */
 439         abstract public function getFileContents( array $params );
 440
 441         /**
 442          * Get the size (bytes) of a file at a storage path in the backend.
 443          *
 444          * $params include:
 445          *     src    : source storage path
 446          *     latest : use the latest available data
 447          *
 448          * @param $params Array
 449          * @return integer|bool Returns false on failure
 450          */
 451         abstract public function getFileSize( array $params );
 452
 453         /**
 454          * Get quick information about a file at a storage path in the backend.
 455          * If the file does not exist, then this returns false.
 456          * Otherwise, the result is an associative array that includes:
 457          *     mtime  : the last-modified timestamp (TS_MW)
 458          *     size   : the file size (bytes)
 459          * Additional values may be included for internal use only.
 460          *
 461          * $params include:
 462          *     src    : source storage path
 463          *     latest : use the latest available data
 464          *
 465          * @param $params Array
 466          * @return Array|bool|null Returns null on failure
 467          */
 468         abstract public function getFileStat( array $params );
 469
 470         /**
 471          * Get a SHA-1 hash of the file at a storage path in the backend.
 472          *
 473          * $params include:
 474          *     src    : source storage path
 475          *     latest : use the latest available data
 476          *
 477          * @param $params Array
 478          * @return string|bool Hash string or false on failure
 479          */
 480         abstract public function getFileSha1Base36( array $params );
 481
 482         /**
 483          * Get the properties of the file at a storage path in the backend.
 484          * Returns FSFile::placeholderProps() on failure.
 485          *
 486          * $params include:
 487          *     src    : source storage path
 488          *     latest : use the latest available data
 489          *
 490          * @param $params Array
 491          * @return Array
 492          */
 493         abstract public function getFileProps( array $params );
 494
 495         /**
 496          * Stream the file at a storage path in the backend.
 497          * If the file does not exists, a 404 error will be given.
 498          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
 499          * must be sent if streaming began, while none should be sent otherwise.
 500          * Implementations should flush the output buffer before sending data.
 501          *
 502          * $params include:
 503          *     src     : source storage path
 504          *     headers : additional HTTP headers to send on success
 505          *     latest  : use the latest available data
 506          *
 507          * @param $params Array
 508          * @return Status
 509          */
 510         abstract public function streamFile( array $params );
 511
 512         /**
 513          * Returns a file system file, identical to the file at a storage path.
 514          * The file returned is either:
 515          * a) A local copy of the file at a storage path in the backend.
 516          *    The temporary copy will have the same extension as the source.
 517          * b) An original of the file at a storage path in the backend.
 518          * Temporary files may be purged when the file object falls out of scope.
 519          *
 520          * Write operations should *never* be done on this file as some backends
 521          * may do internal tracking or may be instances of FileBackendMultiWrite.
 522          * In that later case, there are copies of the file that must stay in sync.
 523          * Additionally, further calls to this function may return the same file.
 524          *
 525          * $params include:
 526          *     src    : source storage path
 527          *     latest : use the latest available data
 528          *
 529          * @param $params Array
 530          * @return FSFile|null Returns null on failure
 531          */
 532         abstract public function getLocalReference( array $params );
 533
 534         /**
 535          * Get a local copy on disk of the file at a storage path in the backend.
 536          * The temporary copy will have the same file extension as the source.
 537          * Temporary files may be purged when the file object falls out of scope.
 538          *
 539          * $params include:
 540          *     src    : source storage path
 541          *     latest : use the latest available data
 542          *
 543          * @param $params Array
 544          * @return TempFSFile|null Returns null on failure
 545          */
 546         abstract public function getLocalCopy( array $params );
 547
 548         /**
 549          * Check if a directory exists at a given storage path.
 550          * Backends using key/value stores will check if the path is a
 551          * virtual directory, meaning there are files under the given directory.
 552          *
 553          * Storage backends with eventual consistency might return stale data.
 554          *
 555          * $params include:
 556          *     dir : storage directory
 557          *
 558          * @return bool|null Returns null on failure
 559          * @since 1.20
 560          */
 561         abstract public function directoryExists( array $params );
 562
 563         /**
 564          * Get an iterator to list *all* directories under a storage directory.
 565          * If the directory is of the form "mwstore://backend/container",
 566          * then all directories in the container should be listed.
 567          * If the directory is of form "mwstore://backend/container/dir",
 568          * then all directories directly under that directory should be listed.
 569          * Results should be storage directories relative to the given directory.
 570          *
 571          * Storage backends with eventual consistency might return stale data.
 572          *
 573          * $params include:
 574          *     dir     : storage directory
 575          *     topOnly : only return direct child directories of the directory
 576          *
 577          * @return Traversable|Array|null Returns null on failure
 578          * @since 1.20
 579          */
 580         abstract public function getDirectoryList( array $params );
 581
 582         /**
 583          * Same as FileBackend::getDirectoryList() except only lists
 584          * directories that are immediately under the given directory.
 585          *
 586          * Storage backends with eventual consistency might return stale data.
 587          *
 588          * $params include:
 589          *     dir : storage directory
 590          *
 591          * @return Traversable|Array|null Returns null on failure
 592          * @since 1.20
 593          */
 594         final public function getTopDirectoryList( array $params ) {
 595                 return $this->getDirectoryList( array( 'topOnly' => true ) + $params );
 596         }
 597
 598         /**
 599          * Get an iterator to list *all* stored files under a storage directory.
 600          * If the directory is of the form "mwstore://backend/container",
 601          * then all files in the container should be listed.
 602          * If the directory is of form "mwstore://backend/container/dir",
 603          * then all files under that directory should be listed.
 604          * Results should be storage paths relative to the given directory.
 605          *
 606          * Storage backends with eventual consistency might return stale data.
 607          *
 608          * $params include:
 609          *     dir     : storage directory
 610          *     topOnly : only return direct child files of the directory
 611          *
 612          * @return Traversable|Array|null Returns null on failure
 613          */
 614         abstract public function getFileList( array $params );
 615
 616         /**
 617          * Same as FileBackend::getFileList() except only lists
 618          * files that are immediately under the given directory.
 619          *
 620          * Storage backends with eventual consistency might return stale data.
 621          *
 622          * $params include:
 623          *     dir : storage directory
 624          *
 625          * @return Traversable|Array|null Returns null on failure
 626          * @since 1.20
 627          */
 628         final public function getTopFileList( array $params ) {
 629                 return $this->getFileList( array( 'topOnly' => true ) + $params );
 630         }
 631
 632         /**
 633          * Invalidate any in-process file existence and property cache.
 634          * If $paths is given, then only the cache for those files will be cleared.
 635          *
 636          * @param $paths Array Storage paths (optional)
 637          * @return void
 638          */
 639         public function clearCache( array $paths = null ) {}
 640
 641         /**
 642          * Lock the files at the given storage paths in the backend.
 643          * This will either lock all the files or none (on failure).
 644          *
 645          * Callers should consider using getScopedFileLocks() instead.
 646          *
 647          * @param $paths Array Storage paths
 648          * @param $type integer LockManager::LOCK_* constant
 649          * @return Status
 650          */
 651         final public function lockFiles( array $paths, $type ) {
 652                 return $this->lockManager->lock( $paths, $type );
 653         }
 654
 655         /**
 656          * Unlock the files at the given storage paths in the backend.
 657          *
 658          * @param $paths Array Storage paths
 659          * @param $type integer LockManager::LOCK_* constant
 660          * @return Status
 661          */
 662         final public function unlockFiles( array $paths, $type ) {
 663                 return $this->lockManager->unlock( $paths, $type );
 664         }
 665
 666         /**
 667          * Lock the files at the given storage paths in the backend.
 668          * This will either lock all the files or none (on failure).
 669          * On failure, the status object will be updated with errors.
 670          *
 671          * Once the return value goes out scope, the locks will be released and
 672          * the status updated. Unlock fatals will not change the status "OK" value.
 673          *
 674          * @param $paths Array Storage paths
 675          * @param $type integer LockManager::LOCK_* constant
 676          * @param $status Status Status to update on lock/unlock
 677          * @return ScopedLock|null Returns null on failure
 678          */
 679         final public function getScopedFileLocks( array $paths, $type, Status $status ) {
 680                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status );
 681         }
 682
 683         /**
 684          * Get the root storage path of this backend.
 685          * All container paths are "subdirectories" of this path.
 686          *
 687          * @return string Storage path
 688          * @since 1.20
 689          */
 690         final public function getRootStoragePath() {
 691                 return "mwstore://{$this->name}";
 692         }
 693
 694         /**
 695          * Check if a given path is a "mwstore://" path.
 696          * This does not do any further validation or any existence checks.
 697          *
 698          * @param $path string
 699          * @return bool
 700          */
 701         final public static function isStoragePath( $path ) {
 702                 return ( strpos( $path, 'mwstore://' ) === 0 );
 703         }
 704
 705         /**
 706          * Split a storage path into a backend name, a container name,
 707          * and a relative file path. The relative path may be the empty string.
 708          * This does not do any path normalization or traversal checks.
 709          *
 710          * @param $storagePath string
 711          * @return Array (backend, container, rel object) or (null, null, null)
 712          */
 713         final public static function splitStoragePath( $storagePath ) {
 714                 if ( self::isStoragePath( $storagePath ) ) {
 715                         // Remove the "mwstore://" prefix and split the path
 716                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
 717                         if ( count( $parts ) >= 2 && $parts[0] != '' && $parts[1] != '' ) {
 718                                 if ( count( $parts ) == 3 ) {
 719                                         return $parts; // e.g. "backend/container/path"
 720                                 } else {
 721                                         return array( $parts[0], $parts[1], '' ); // e.g. "backend/container"
 722                                 }
 723                         }
 724                 }
 725                 return array( null, null, null );
 726         }
 727
 728         /**
 729          * Normalize a storage path by cleaning up directory separators.
 730          * Returns null if the path is not of the format of a valid storage path.
 731          *
 732          * @param $storagePath string
 733          * @return string|null
 734          */
 735         final public static function normalizeStoragePath( $storagePath ) {
 736                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
 737                 if ( $relPath !== null ) { // must be for this backend
 738                         $relPath = self::normalizeContainerPath( $relPath );
 739                         if ( $relPath !== null ) {
 740                                 return ( $relPath != '' )
 741                                         ? "mwstore://{$backend}/{$container}/{$relPath}"
 742                                         : "mwstore://{$backend}/{$container}";
 743                         }
 744                 }
 745                 return null;
 746         }
 747
 748         /**
 749          * Get the parent storage directory of a storage path.
 750          * This returns a path like "mwstore://backend/container",
 751          * "mwstore://backend/container/...", or null if there is no parent.
 752          *
 753          * @param $storagePath string
 754          * @return string|null
 755          */
 756         final public static function parentStoragePath( $storagePath ) {
 757                 $storagePath = dirname( $storagePath );
 758                 list( $b, $cont, $rel ) = self::splitStoragePath( $storagePath );
 759                 return ( $rel === null ) ? null : $storagePath;
 760         }
 761
 762         /**
 763          * Get the final extension from a storage or FS path
 764          *
 765          * @param $path string
 766          * @return string
 767          */
 768         final public static function extensionFromPath( $path ) {
 769                 $i = strrpos( $path, '.' );
 770                 return strtolower( $i ? substr( $path, $i + 1 ) : '' );
 771         }
 772
 773         /**
 774          * Check if a relative path has no directory traversals
 775          *
 776          * @param $path string
 777          * @return bool
 778          * @since 1.20
 779          */
 780         final public static function isPathTraversalFree( $path ) {
 781                 return ( self::normalizeContainerPath( $path ) !== null );
 782         }
 783
 784         /**
 785          * Validate and normalize a relative storage path.
 786          * Null is returned if the path involves directory traversal.
 787          * Traversal is insecure for FS backends and broken for others.
 788          *
 789          * This uses the same traversal protection as Title::secureAndSplit().
 790          *
 791          * @param $path string Storage path relative to a container
 792          * @return string|null
 793          */
 794         final protected static function normalizeContainerPath( $path ) {
 795                 // Normalize directory separators
 796                 $path = strtr( $path, '\\', '/' );
 797                 // Collapse any consecutive directory separators
 798                 $path = preg_replace( '![/]{2,}!', '/', $path );
 799                 // Remove any leading directory separator
 800                 $path = ltrim( $path, '/' );
 801                 // Use the same traversal protection as Title::secureAndSplit()
 802                 if ( strpos( $path, '.' ) !== false ) {
 803                         if (
 804                                 $path === '.' ||
 805                                 $path === '..' ||
 806                                 strpos( $path, './' ) === 0 ||
 807                                 strpos( $path, '../' ) === 0 ||
 808                                 strpos( $path, '/./' ) !== false ||
 809                                 strpos( $path, '/../' ) !== false
 810                         ) {
 811                                 return null;
 812                         }
 813                 }
 814                 return $path;
 815         }
 816 }