includes/filerepo/backend/FileOp.php

   1 <?php
   2 /**
   3  * Helper class for representing operations with transaction support.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup FileBackend
  22  * @author Aaron Schulz
  23  */
  24
  25 /**
  26  * FileBackend helper class for representing operations.
  27  * Do not use this class from places outside FileBackend.
  28  *
  29  * Methods called from FileOpBatch::attempt() should avoid throwing
  30  * exceptions at all costs. FileOp objects should be lightweight in order
  31  * to support large arrays in memory and serialization.
  32  *
  33  * @ingroup FileBackend
  34  * @since 1.19
  35  */
  36 abstract class FileOp {
  37         /** @var Array */
  38         protected $params = array();
  39         /** @var FileBackendStore */
  40         protected $backend;
  41
  42         protected $state = self::STATE_NEW; // integer
  43         protected $failed = false; // boolean
  44         protected $async = false; // boolean
  45         protected $useLatest = true; // boolean
  46         protected $batchId; // string
  47
  48         protected $sourceSha1; // string
  49         protected $destSameAsSource; // boolean
  50
  51         /* Object life-cycle */
  52         const STATE_NEW = 1;
  53         const STATE_CHECKED = 2;
  54         const STATE_ATTEMPTED = 3;
  55
  56         /**
  57          * Build a new file operation transaction
  58          *
  59          * @param $backend FileBackendStore
  60          * @param $params Array
  61          * @throws MWException
  62          */
  63         final public function __construct( FileBackendStore $backend, array $params ) {
  64                 $this->backend = $backend;
  65                 list( $required, $optional ) = $this->allowedParams();
  66                 foreach ( $required as $name ) {
  67                         if ( isset( $params[$name] ) ) {
  68                                 $this->params[$name] = $params[$name];
  69                         } else {
  70                                 throw new MWException( "File operation missing parameter '$name'." );
  71                         }
  72                 }
  73                 foreach ( $optional as $name ) {
  74                         if ( isset( $params[$name] ) ) {
  75                                 $this->params[$name] = $params[$name];
  76                         }
  77                 }
  78                 $this->params = $params;
  79         }
  80
  81         /**
  82          * Set the batch UUID this operation belongs to
  83          *
  84          * @param $batchId string
  85          * @return void
  86          */
  87         final public function setBatchId( $batchId ) {
  88                 $this->batchId = $batchId;
  89         }
  90
  91         /**
  92          * Whether to allow stale data for file reads and stat checks
  93          *
  94          * @param $allowStale bool
  95          * @return void
  96          */
  97         final public function allowStaleReads( $allowStale ) {
  98                 $this->useLatest = !$allowStale;
  99         }
 100
 101         /**
 102          * Get the value of the parameter with the given name
 103          *
 104          * @param $name string
 105          * @return mixed Returns null if the parameter is not set
 106          */
 107         final public function getParam( $name ) {
 108                 return isset( $this->params[$name] ) ? $this->params[$name] : null;
 109         }
 110
 111         /**
 112          * Check if this operation failed precheck() or attempt()
 113          *
 114          * @return bool
 115          */
 116         final public function failed() {
 117                 return $this->failed;
 118         }
 119
 120         /**
 121          * Get a new empty predicates array for precheck()
 122          *
 123          * @return Array
 124          */
 125         final public static function newPredicates() {
 126                 return array( 'exists' => array(), 'sha1' => array() );
 127         }
 128
 129         /**
 130          * Get a new empty dependency tracking array for paths read/written to
 131          *
 132          * @return Array
 133          */
 134         final public static function newDependencies() {
 135                 return array( 'read' => array(), 'write' => array() );
 136         }
 137
 138         /**
 139          * Update a dependency tracking array to account for this operation
 140          *
 141          * @param $deps Array Prior path reads/writes; format of FileOp::newPredicates()
 142          * @return Array
 143          */
 144         final public function applyDependencies( array $deps ) {
 145                 $deps['read']  += array_fill_keys( $this->storagePathsRead(), 1 );
 146                 $deps['write'] += array_fill_keys( $this->storagePathsChanged(), 1 );
 147                 return $deps;
 148         }
 149
 150         /**
 151          * Check if this operation changes files listed in $paths
 152          *
 153          * @param $paths Array Prior path reads/writes; format of FileOp::newPredicates()
 154          * @return boolean
 155          */
 156         final public function dependsOn( array $deps ) {
 157                 foreach ( $this->storagePathsChanged() as $path ) {
 158                         if ( isset( $deps['read'][$path] ) || isset( $deps['write'][$path] ) ) {
 159                                 return true; // "output" or "anti" dependency
 160                         }
 161                 }
 162                 foreach ( $this->storagePathsRead() as $path ) {
 163                         if ( isset( $deps['write'][$path] ) ) {
 164                                 return true; // "flow" dependency
 165                         }
 166                 }
 167                 return false;
 168         }
 169
 170         /**
 171          * Get the file journal entries for this file operation
 172          *
 173          * @param $oPredicates Array Pre-op info about files (format of FileOp::newPredicates)
 174          * @param $nPredicates Array Post-op info about files (format of FileOp::newPredicates)
 175          * @return Array
 176          */
 177         final public function getJournalEntries( array $oPredicates, array $nPredicates ) {
 178                 $nullEntries = array();
 179                 $updateEntries = array();
 180                 $deleteEntries = array();
 181                 $pathsUsed = array_merge( $this->storagePathsRead(), $this->storagePathsChanged() );
 182                 foreach ( $pathsUsed as $path ) {
 183                         $nullEntries[] = array( // assertion for recovery
 184                                 'op'      => 'null',
 185                                 'path'    => $path,
 186                                 'newSha1' => $this->fileSha1( $path, $oPredicates )
 187                         );
 188                 }
 189                 foreach ( $this->storagePathsChanged() as $path ) {
 190                         if ( $nPredicates['sha1'][$path] === false ) { // deleted
 191                                 $deleteEntries[] = array(
 192                                         'op'      => 'delete',
 193                                         'path'    => $path,
 194                                         'newSha1' => ''
 195                                 );
 196                         } else { // created/updated
 197                                 $updateEntries[] = array(
 198                                         'op'      => $this->fileExists( $path, $oPredicates ) ? 'update' : 'create',
 199                                         'path'    => $path,
 200                                         'newSha1' => $nPredicates['sha1'][$path]
 201                                 );
 202                         }
 203                 }
 204                 return array_merge( $nullEntries, $updateEntries, $deleteEntries );
 205         }
 206
 207         /**
 208          * Check preconditions of the operation without writing anything
 209          *
 210          * @param $predicates Array
 211          * @return Status
 212          */
 213         final public function precheck( array &$predicates ) {
 214                 if ( $this->state !== self::STATE_NEW ) {
 215                         return Status::newFatal( 'fileop-fail-state', self::STATE_NEW, $this->state );
 216                 }
 217                 $this->state = self::STATE_CHECKED;
 218                 $status = $this->doPrecheck( $predicates );
 219                 if ( !$status->isOK() ) {
 220                         $this->failed = true;
 221                 }
 222                 return $status;
 223         }
 224
 225         /**
 226          * @return Status
 227          */
 228         protected function doPrecheck( array &$predicates ) {
 229                 return Status::newGood();
 230         }
 231
 232         /**
 233          * Attempt the operation
 234          *
 235          * @return Status
 236          */
 237         final public function attempt() {
 238                 if ( $this->state !== self::STATE_CHECKED ) {
 239                         return Status::newFatal( 'fileop-fail-state', self::STATE_CHECKED, $this->state );
 240                 } elseif ( $this->failed ) { // failed precheck
 241                         return Status::newFatal( 'fileop-fail-attempt-precheck' );
 242                 }
 243                 $this->state = self::STATE_ATTEMPTED;
 244                 $status = $this->doAttempt();
 245                 if ( !$status->isOK() ) {
 246                         $this->failed = true;
 247                         $this->logFailure( 'attempt' );
 248                 }
 249                 return $status;
 250         }
 251
 252         /**
 253          * @return Status
 254          */
 255         protected function doAttempt() {
 256                 return Status::newGood();
 257         }
 258
 259         /**
 260          * Attempt the operation in the background
 261          *
 262          * @return Status
 263          */
 264         final public function attemptAsync() {
 265                 $this->async = true;
 266                 $result = $this->attempt();
 267                 $this->async = false;
 268                 return $result;
 269         }
 270
 271         /**
 272          * Get the file operation parameters
 273          *
 274          * @return Array (required params list, optional params list)
 275          */
 276         protected function allowedParams() {
 277                 return array( array(), array() );
 278         }
 279
 280         /**
 281          * Adjust params to FileBackendStore internal file calls
 282          *
 283          * @param $params Array
 284          * @return Array (required params list, optional params list)
 285          */
 286         protected function setFlags( array $params ) {
 287                 return array( 'async' => $this->async ) + $params;
 288         }
 289
 290         /**
 291          * Get a list of storage paths read from for this operation
 292          *
 293          * @return Array
 294          */
 295         final public function storagePathsRead() {
 296                 return array_map( 'FileBackend::normalizeStoragePath', $this->doStoragePathsRead() );
 297         }
 298
 299         /**
 300          * @see FileOp::storagePathsRead()
 301          * @return Array
 302          */
 303         protected function doStoragePathsRead() {
 304                 return array();
 305         }
 306
 307         /**
 308          * Get a list of storage paths written to for this operation
 309          *
 310          * @return Array
 311          */
 312         final public function storagePathsChanged() {
 313                 return array_map( 'FileBackend::normalizeStoragePath', $this->doStoragePathsChanged() );
 314         }
 315
 316         /**
 317          * @see FileOp::storagePathsChanged()
 318          * @return Array
 319          */
 320         protected function doStoragePathsChanged() {
 321                 return array();
 322         }
 323
 324         /**
 325          * Check for errors with regards to the destination file already existing.
 326          * This also updates the destSameAsSource and sourceSha1 member variables.
 327          * A bad status will be returned if there is no chance it can be overwritten.
 328          *
 329          * @param $predicates Array
 330          * @return Status
 331          */
 332         protected function precheckDestExistence( array $predicates ) {
 333                 $status = Status::newGood();
 334                 // Get hash of source file/string and the destination file
 335                 $this->sourceSha1 = $this->getSourceSha1Base36(); // FS file or data string
 336                 if ( $this->sourceSha1 === null ) { // file in storage?
 337                         $this->sourceSha1 = $this->fileSha1( $this->params['src'], $predicates );
 338                 }
 339                 $this->destSameAsSource = false;
 340                 if ( $this->fileExists( $this->params['dst'], $predicates ) ) {
 341                         if ( $this->getParam( 'overwrite' ) ) {
 342                                 return $status; // OK
 343                         } elseif ( $this->getParam( 'overwriteSame' ) ) {
 344                                 $dhash = $this->fileSha1( $this->params['dst'], $predicates );
 345                                 // Check if hashes are valid and match each other...
 346                                 if ( !strlen( $this->sourceSha1 ) || !strlen( $dhash ) ) {
 347                                         $status->fatal( 'backend-fail-hashes' );
 348                                 } elseif ( $this->sourceSha1 !== $dhash ) {
 349                                         // Give an error if the files are not identical
 350                                         $status->fatal( 'backend-fail-notsame', $this->params['dst'] );
 351                                 } else {
 352                                         $this->destSameAsSource = true; // OK
 353                                 }
 354                                 return $status; // do nothing; either OK or bad status
 355                         } else {
 356                                 $status->fatal( 'backend-fail-alreadyexists', $this->params['dst'] );
 357                                 return $status;
 358                         }
 359                 }
 360                 return $status;
 361         }
 362
 363         /**
 364          * precheckDestExistence() helper function to get the source file SHA-1.
 365          * Subclasses should overwride this iff the source is not in storage.
 366          *
 367          * @return string|bool Returns false on failure
 368          */
 369         protected function getSourceSha1Base36() {
 370                 return null; // N/A
 371         }
 372
 373         /**
 374          * Check if a file will exist in storage when this operation is attempted
 375          *
 376          * @param $source string Storage path
 377          * @param $predicates Array
 378          * @return bool
 379          */
 380         final protected function fileExists( $source, array $predicates ) {
 381                 if ( isset( $predicates['exists'][$source] ) ) {
 382                         return $predicates['exists'][$source]; // previous op assures this
 383                 } else {
 384                         $params = array( 'src' => $source, 'latest' => $this->useLatest );
 385                         return $this->backend->fileExists( $params );
 386                 }
 387         }
 388
 389         /**
 390          * Get the SHA-1 of a file in storage when this operation is attempted
 391          *
 392          * @param $source string Storage path
 393          * @param $predicates Array
 394          * @return string|bool False on failure
 395          */
 396         final protected function fileSha1( $source, array $predicates ) {
 397                 if ( isset( $predicates['sha1'][$source] ) ) {
 398                         return $predicates['sha1'][$source]; // previous op assures this
 399                 } else {
 400                         $params = array( 'src' => $source, 'latest' => $this->useLatest );
 401                         return $this->backend->getFileSha1Base36( $params );
 402                 }
 403         }
 404
 405         /**
 406          * Get the backend this operation is for
 407          *
 408          * @return FileBackendStore
 409          */
 410         public function getBackend() {
 411                 return $this->backend;
 412         }
 413
 414         /**
 415          * Log a file operation failure and preserve any temp files
 416          *
 417          * @param $action string
 418          * @return void
 419          */
 420         final public function logFailure( $action ) {
 421                 $params = $this->params;
 422                 $params['failedAction'] = $action;
 423                 try {
 424                         wfDebugLog( 'FileOperation', get_class( $this ) .
 425                                 " failed (batch #{$this->batchId}): " . FormatJson::encode( $params ) );
 426                 } catch ( Exception $e ) {
 427                         // bad config? debug log error?
 428                 }
 429         }
 430 }
 431
 432 /**
 433  * Store a file into the backend from a file on the file system.
 434  * Parameters similar to FileBackendStore::storeInternal(), which include:
 435  *     src           : source path on file system
 436  *     dst           : destination storage path
 437  *     overwrite     : do nothing and pass if an identical file exists at destination
 438  *     overwriteSame : override any existing file at destination
 439  */
 440 class StoreFileOp extends FileOp {
 441
 442         /**
 443          * @return array
 444          */
 445         protected function allowedParams() {
 446                 return array( array( 'src', 'dst' ), array( 'overwrite', 'overwriteSame' ) );
 447         }
 448
 449         /**
 450          * @param $predicates array
 451          * @return Status
 452          */
 453         protected function doPrecheck( array &$predicates ) {
 454                 $status = Status::newGood();
 455                 // Check if the source file exists on the file system
 456                 if ( !is_file( $this->params['src'] ) ) {
 457                         $status->fatal( 'backend-fail-notexists', $this->params['src'] );
 458                         return $status;
 459                 // Check if the source file is too big
 460                 } elseif ( filesize( $this->params['src'] ) > $this->backend->maxFileSizeInternal() ) {
 461                         $status->fatal( 'backend-fail-maxsize',
 462                                 $this->params['dst'], $this->backend->maxFileSizeInternal() );
 463                         $status->fatal( 'backend-fail-store', $this->params['src'], $this->params['dst'] );
 464                         return $status;
 465                 // Check if a file can be placed at the destination
 466                 } elseif ( !$this->backend->isPathUsableInternal( $this->params['dst'] ) ) {
 467                         $status->fatal( 'backend-fail-usable', $this->params['dst'] );
 468                         $status->fatal( 'backend-fail-store', $this->params['src'], $this->params['dst'] );
 469                         return $status;
 470                 }
 471                 // Check if destination file exists
 472                 $status->merge( $this->precheckDestExistence( $predicates ) );
 473                 if ( $status->isOK() ) {
 474                         // Update file existence predicates
 475                         $predicates['exists'][$this->params['dst']] = true;
 476                         $predicates['sha1'][$this->params['dst']] = $this->sourceSha1;
 477                 }
 478                 return $status; // safe to call attempt()
 479         }
 480
 481         /**
 482          * @return Status
 483          */
 484         protected function doAttempt() {
 485                 // Store the file at the destination
 486                 if ( !$this->destSameAsSource ) {
 487                         return $this->backend->storeInternal( $this->setFlags( $this->params ) );
 488                 }
 489                 return Status::newGood();
 490         }
 491
 492         /**
 493          * @return bool|string
 494          */
 495         protected function getSourceSha1Base36() {
 496                 wfSuppressWarnings();
 497                 $hash = sha1_file( $this->params['src'] );
 498                 wfRestoreWarnings();
 499                 if ( $hash !== false ) {
 500                         $hash = wfBaseConvert( $hash, 16, 36, 31 );
 501                 }
 502                 return $hash;
 503         }
 504
 505         protected function doStoragePathsChanged() {
 506                 return array( $this->params['dst'] );
 507         }
 508 }
 509
 510 /**
 511  * Create a file in the backend with the given content.
 512  * Parameters similar to FileBackendStore::createInternal(), which include:
 513  *     content       : the raw file contents
 514  *     dst           : destination storage path
 515  *     overwrite     : do nothing and pass if an identical file exists at destination
 516  *     overwriteSame : override any existing file at destination
 517  */
 518 class CreateFileOp extends FileOp {
 519         protected function allowedParams() {
 520                 return array( array( 'content', 'dst' ), array( 'overwrite', 'overwriteSame' ) );
 521         }
 522
 523         protected function doPrecheck( array &$predicates ) {
 524                 $status = Status::newGood();
 525                 // Check if the source data is too big
 526                 if ( strlen( $this->getParam( 'content' ) ) > $this->backend->maxFileSizeInternal() ) {
 527                         $status->fatal( 'backend-fail-maxsize',
 528                                 $this->params['dst'], $this->backend->maxFileSizeInternal() );
 529                         $status->fatal( 'backend-fail-create', $this->params['dst'] );
 530                         return $status;
 531                 // Check if a file can be placed at the destination
 532                 } elseif ( !$this->backend->isPathUsableInternal( $this->params['dst'] ) ) {
 533                         $status->fatal( 'backend-fail-usable', $this->params['dst'] );
 534                         $status->fatal( 'backend-fail-create', $this->params['dst'] );
 535                         return $status;
 536                 }
 537                 // Check if destination file exists
 538                 $status->merge( $this->precheckDestExistence( $predicates ) );
 539                 if ( $status->isOK() ) {
 540                         // Update file existence predicates
 541                         $predicates['exists'][$this->params['dst']] = true;
 542                         $predicates['sha1'][$this->params['dst']] = $this->sourceSha1;
 543                 }
 544                 return $status; // safe to call attempt()
 545         }
 546
 547         /**
 548          * @return Status
 549          */
 550         protected function doAttempt() {
 551                 if ( !$this->destSameAsSource ) {
 552                         // Create the file at the destination
 553                         return $this->backend->createInternal( $this->setFlags( $this->params ) );
 554                 }
 555                 return Status::newGood();
 556         }
 557
 558         /**
 559          * @return bool|String
 560          */
 561         protected function getSourceSha1Base36() {
 562                 return wfBaseConvert( sha1( $this->params['content'] ), 16, 36, 31 );
 563         }
 564
 565         /**
 566          * @return array
 567          */
 568         protected function doStoragePathsChanged() {
 569                 return array( $this->params['dst'] );
 570         }
 571 }
 572
 573 /**
 574  * Copy a file from one storage path to another in the backend.
 575  * Parameters similar to FileBackendStore::copyInternal(), which include:
 576  *     src           : source storage path
 577  *     dst           : destination storage path
 578  *     overwrite     : do nothing and pass if an identical file exists at destination
 579  *     overwriteSame : override any existing file at destination
 580  */
 581 class CopyFileOp extends FileOp {
 582
 583         /**
 584          * @return array
 585          */
 586         protected function allowedParams() {
 587                 return array( array( 'src', 'dst' ), array( 'overwrite', 'overwriteSame' ) );
 588         }
 589
 590         /**
 591          * @param $predicates array
 592          * @return Status
 593          */
 594         protected function doPrecheck( array &$predicates ) {
 595                 $status = Status::newGood();
 596                 // Check if the source file exists
 597                 if ( !$this->fileExists( $this->params['src'], $predicates ) ) {
 598                         $status->fatal( 'backend-fail-notexists', $this->params['src'] );
 599                         return $status;
 600                 // Check if a file can be placed at the destination
 601                 } elseif ( !$this->backend->isPathUsableInternal( $this->params['dst'] ) ) {
 602                         $status->fatal( 'backend-fail-usable', $this->params['dst'] );
 603                         $status->fatal( 'backend-fail-copy', $this->params['src'], $this->params['dst'] );
 604                         return $status;
 605                 }
 606                 // Check if destination file exists
 607                 $status->merge( $this->precheckDestExistence( $predicates ) );
 608                 if ( $status->isOK() ) {
 609                         // Update file existence predicates
 610                         $predicates['exists'][$this->params['dst']] = true;
 611                         $predicates['sha1'][$this->params['dst']] = $this->sourceSha1;
 612                 }
 613                 return $status; // safe to call attempt()
 614         }
 615
 616         /**
 617          * @return Status
 618          */
 619         protected function doAttempt() {
 620                 // Do nothing if the src/dst paths are the same
 621                 if ( $this->params['src'] !== $this->params['dst'] ) {
 622                         // Copy the file into the destination
 623                         if ( !$this->destSameAsSource ) {
 624                                 return $this->backend->copyInternal( $this->setFlags( $this->params ) );
 625                         }
 626                 }
 627                 return Status::newGood();
 628         }
 629
 630         /**
 631          * @return array
 632          */
 633         protected function doStoragePathsRead() {
 634                 return array( $this->params['src'] );
 635         }
 636
 637         /**
 638          * @return array
 639          */
 640         protected function doStoragePathsChanged() {
 641                 return array( $this->params['dst'] );
 642         }
 643 }
 644
 645 /**
 646  * Move a file from one storage path to another in the backend.
 647  * Parameters similar to FileBackendStore::moveInternal(), which include:
 648  *     src           : source storage path
 649  *     dst           : destination storage path
 650  *     overwrite     : do nothing and pass if an identical file exists at destination
 651  *     overwriteSame : override any existing file at destination
 652  */
 653 class MoveFileOp extends FileOp {
 654         /**
 655          * @return array
 656          */
 657         protected function allowedParams() {
 658                 return array( array( 'src', 'dst' ), array( 'overwrite', 'overwriteSame' ) );
 659         }
 660
 661         /**
 662          * @param $predicates array
 663          * @return Status
 664          */
 665         protected function doPrecheck( array &$predicates ) {
 666                 $status = Status::newGood();
 667                 // Check if the source file exists
 668                 if ( !$this->fileExists( $this->params['src'], $predicates ) ) {
 669                         $status->fatal( 'backend-fail-notexists', $this->params['src'] );
 670                         return $status;
 671                 // Check if a file can be placed at the destination
 672                 } elseif ( !$this->backend->isPathUsableInternal( $this->params['dst'] ) ) {
 673                         $status->fatal( 'backend-fail-usable', $this->params['dst'] );
 674                         $status->fatal( 'backend-fail-move', $this->params['src'], $this->params['dst'] );
 675                         return $status;
 676                 }
 677                 // Check if destination file exists
 678                 $status->merge( $this->precheckDestExistence( $predicates ) );
 679                 if ( $status->isOK() ) {
 680                         // Update file existence predicates
 681                         $predicates['exists'][$this->params['src']] = false;
 682                         $predicates['sha1'][$this->params['src']] = false;
 683                         $predicates['exists'][$this->params['dst']] = true;
 684                         $predicates['sha1'][$this->params['dst']] = $this->sourceSha1;
 685                 }
 686                 return $status; // safe to call attempt()
 687         }
 688
 689         /**
 690          * @return Status
 691          */
 692         protected function doAttempt() {
 693                 // Do nothing if the src/dst paths are the same
 694                 if ( $this->params['src'] !== $this->params['dst'] ) {
 695                         if ( !$this->destSameAsSource ) {
 696                                 // Move the file into the destination
 697                                 return $this->backend->moveInternal( $this->setFlags( $this->params ) );
 698                         } else {
 699                                 // Just delete source as the destination needs no changes
 700                                 $params = array( 'src' => $this->params['src'] );
 701                                 return $this->backend->deleteInternal( $this->setFlags( $params ) );
 702                         }
 703                 }
 704                 return Status::newGood();
 705         }
 706
 707         /**
 708          * @return array
 709          */
 710         protected function doStoragePathsRead() {
 711                 return array( $this->params['src'] );
 712         }
 713
 714         /**
 715          * @return array
 716          */
 717         protected function doStoragePathsChanged() {
 718                 return array( $this->params['src'], $this->params['dst'] );
 719         }
 720 }
 721
 722 /**
 723  * Delete a file at the given storage path from the backend.
 724  * Parameters similar to FileBackendStore::deleteInternal(), which include:
 725  *     src                 : source storage path
 726  *     ignoreMissingSource : don't return an error if the file does not exist
 727  */
 728 class DeleteFileOp extends FileOp {
 729         /**
 730          * @return array
 731          */
 732         protected function allowedParams() {
 733                 return array( array( 'src' ), array( 'ignoreMissingSource' ) );
 734         }
 735
 736         protected $needsDelete = true;
 737
 738         /**
 739          * @param array $predicates
 740          * @return Status
 741          */
 742         protected function doPrecheck( array &$predicates ) {
 743                 $status = Status::newGood();
 744                 // Check if the source file exists
 745                 if ( !$this->fileExists( $this->params['src'], $predicates ) ) {
 746                         if ( !$this->getParam( 'ignoreMissingSource' ) ) {
 747                                 $status->fatal( 'backend-fail-notexists', $this->params['src'] );
 748                                 return $status;
 749                         }
 750                         $this->needsDelete = false;
 751                 }
 752                 // Update file existence predicates
 753                 $predicates['exists'][$this->params['src']] = false;
 754                 $predicates['sha1'][$this->params['src']] = false;
 755                 return $status; // safe to call attempt()
 756         }
 757
 758         /**
 759          * @return Status
 760          */
 761         protected function doAttempt() {
 762                 if ( $this->needsDelete ) {
 763                         // Delete the source file
 764                         return $this->backend->deleteInternal( $this->setFlags( $this->params ) );
 765                 }
 766                 return Status::newGood();
 767         }
 768
 769         /**
 770          * @return array
 771          */
 772         protected function doStoragePathsChanged() {
 773                 return array( $this->params['src'] );
 774         }
 775 }
 776
 777 /**
 778  * Placeholder operation that has no params and does nothing
 779  */
 780 class NullFileOp extends FileOp {}