includes/filebackend/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
  40         /** @var FileBackendStore */
  41         protected $backend;
  42
  43         /** @var int */
  44         protected $state = self::STATE_NEW;
  45
  46         /** @var bool */
  47         protected $failed = false;
  48
  49         /** @var bool */
  50         protected $async = false;
  51
  52         /** @var string */
  53         protected $batchId;
  54
  55         /** @var bool Operation is not a no-op */
  56         protected $doOperation = true;
  57
  58         /** @var string */
  59         protected $sourceSha1;
  60
  61         /** @var bool */
  62         protected $overwriteSameCase;
  63
  64         /** @var bool */
  65         protected $destExists;
  66
  67         /* Object life-cycle */
  68         const STATE_NEW = 1;
  69         const STATE_CHECKED = 2;
  70         const STATE_ATTEMPTED = 3;
  71
  72         /**
  73          * Build a new batch file operation transaction
  74          *
  75          * @param FileBackendStore $backend
  76          * @param array $params
  77          * @throws FileBackendError
  78          */
  79         final public function __construct( FileBackendStore $backend, array $params ) {
  80                 $this->backend = $backend;
  81                 list( $required, $optional, $paths ) = $this->allowedParams();
  82                 foreach ( $required as $name ) {
  83                         if ( isset( $params[$name] ) ) {
  84                                 $this->params[$name] = $params[$name];
  85                         } else {
  86                                 throw new FileBackendError( "File operation missing parameter '$name'." );
  87                         }
  88                 }
  89                 foreach ( $optional as $name ) {
  90                         if ( isset( $params[$name] ) ) {
  91                                 $this->params[$name] = $params[$name];
  92                         }
  93                 }
  94                 foreach ( $paths as $name ) {
  95                         if ( isset( $this->params[$name] ) ) {
  96                                 // Normalize paths so the paths to the same file have the same string
  97                                 $this->params[$name] = self::normalizeIfValidStoragePath( $this->params[$name] );
  98                         }
  99                 }
 100         }
 101
 102         /**
 103          * Normalize a string if it is a valid storage path
 104          *
 105          * @param string $path
 106          * @return string
 107          */
 108         protected static function normalizeIfValidStoragePath( $path ) {
 109                 if ( FileBackend::isStoragePath( $path ) ) {
 110                         $res = FileBackend::normalizeStoragePath( $path );
 111
 112                         return ( $res !== null ) ? $res : $path;
 113                 }
 114
 115                 return $path;
 116         }
 117
 118         /**
 119          * Set the batch UUID this operation belongs to
 120          *
 121          * @param string $batchId
 122          */
 123         final public function setBatchId( $batchId ) {
 124                 $this->batchId = $batchId;
 125         }
 126
 127         /**
 128          * Get the value of the parameter with the given name
 129          *
 130          * @param string $name
 131          * @return mixed Returns null if the parameter is not set
 132          */
 133         final public function getParam( $name ) {
 134                 return isset( $this->params[$name] ) ? $this->params[$name] : null;
 135         }
 136
 137         /**
 138          * Check if this operation failed precheck() or attempt()
 139          *
 140          * @return bool
 141          */
 142         final public function failed() {
 143                 return $this->failed;
 144         }
 145
 146         /**
 147          * Get a new empty predicates array for precheck()
 148          *
 149          * @return array
 150          */
 151         final public static function newPredicates() {
 152                 return array( 'exists' => array(), 'sha1' => array() );
 153         }
 154
 155         /**
 156          * Get a new empty dependency tracking array for paths read/written to
 157          *
 158          * @return array
 159          */
 160         final public static function newDependencies() {
 161                 return array( 'read' => array(), 'write' => array() );
 162         }
 163
 164         /**
 165          * Update a dependency tracking array to account for this operation
 166          *
 167          * @param array $deps Prior path reads/writes; format of FileOp::newPredicates()
 168          * @return array
 169          */
 170         final public function applyDependencies( array $deps ) {
 171                 $deps['read'] += array_fill_keys( $this->storagePathsRead(), 1 );
 172                 $deps['write'] += array_fill_keys( $this->storagePathsChanged(), 1 );
 173
 174                 return $deps;
 175         }
 176
 177         /**
 178          * Check if this operation changes files listed in $paths
 179          *
 180          * @param array $deps Prior path reads/writes; format of FileOp::newPredicates()
 181          * @return bool
 182          */
 183         final public function dependsOn( array $deps ) {
 184                 foreach ( $this->storagePathsChanged() as $path ) {
 185                         if ( isset( $deps['read'][$path] ) || isset( $deps['write'][$path] ) ) {
 186                                 return true; // "output" or "anti" dependency
 187                         }
 188                 }
 189                 foreach ( $this->storagePathsRead() as $path ) {
 190                         if ( isset( $deps['write'][$path] ) ) {
 191                                 return true; // "flow" dependency
 192                         }
 193                 }
 194
 195                 return false;
 196         }
 197
 198         /**
 199          * Get the file journal entries for this file operation
 200          *
 201          * @param array $oPredicates Pre-op info about files (format of FileOp::newPredicates)
 202          * @param array $nPredicates Post-op info about files (format of FileOp::newPredicates)
 203          * @return array
 204          */
 205         final public function getJournalEntries( array $oPredicates, array $nPredicates ) {
 206                 if ( !$this->doOperation ) {
 207                         return array(); // this is a no-op
 208                 }
 209                 $nullEntries = array();
 210                 $updateEntries = array();
 211                 $deleteEntries = array();
 212                 $pathsUsed = array_merge( $this->storagePathsRead(), $this->storagePathsChanged() );
 213                 foreach ( array_unique( $pathsUsed ) as $path ) {
 214                         $nullEntries[] = array( // assertion for recovery
 215                                 'op' => 'null',
 216                                 'path' => $path,
 217                                 'newSha1' => $this->fileSha1( $path, $oPredicates )
 218                         );
 219                 }
 220                 foreach ( $this->storagePathsChanged() as $path ) {
 221                         if ( $nPredicates['sha1'][$path] === false ) { // deleted
 222                                 $deleteEntries[] = array(
 223                                         'op' => 'delete',
 224                                         'path' => $path,
 225                                         'newSha1' => ''
 226                                 );
 227                         } else { // created/updated
 228                                 $updateEntries[] = array(
 229                                         'op' => $this->fileExists( $path, $oPredicates ) ? 'update' : 'create',
 230                                         'path' => $path,
 231                                         'newSha1' => $nPredicates['sha1'][$path]
 232                                 );
 233                         }
 234                 }
 235
 236                 return array_merge( $nullEntries, $updateEntries, $deleteEntries );
 237         }
 238
 239         /**
 240          * Check preconditions of the operation without writing anything.
 241          * This must update $predicates for each path that the op can change
 242          * except when a failing status object is returned.
 243          *
 244          * @param array $predicates
 245          * @return Status
 246          */
 247         final public function precheck( array &$predicates ) {
 248                 if ( $this->state !== self::STATE_NEW ) {
 249                         return Status::newFatal( 'fileop-fail-state', self::STATE_NEW, $this->state );
 250                 }
 251                 $this->state = self::STATE_CHECKED;
 252                 $status = $this->doPrecheck( $predicates );
 253                 if ( !$status->isOK() ) {
 254                         $this->failed = true;
 255                 }
 256
 257                 return $status;
 258         }
 259
 260         /**
 261          * @param array $predicates
 262          * @return Status
 263          */
 264         protected function doPrecheck( array &$predicates ) {
 265                 return Status::newGood();
 266         }
 267
 268         /**
 269          * Attempt the operation
 270          *
 271          * @return Status
 272          */
 273         final public function attempt() {
 274                 if ( $this->state !== self::STATE_CHECKED ) {
 275                         return Status::newFatal( 'fileop-fail-state', self::STATE_CHECKED, $this->state );
 276                 } elseif ( $this->failed ) { // failed precheck
 277                         return Status::newFatal( 'fileop-fail-attempt-precheck' );
 278                 }
 279                 $this->state = self::STATE_ATTEMPTED;
 280                 if ( $this->doOperation ) {
 281                         $status = $this->doAttempt();
 282                         if ( !$status->isOK() ) {
 283                                 $this->failed = true;
 284                                 $this->logFailure( 'attempt' );
 285                         }
 286                 } else { // no-op
 287                         $status = Status::newGood();
 288                 }
 289
 290                 return $status;
 291         }
 292
 293         /**
 294          * @return Status
 295          */
 296         protected function doAttempt() {
 297                 return Status::newGood();
 298         }
 299
 300         /**
 301          * Attempt the operation in the background
 302          *
 303          * @return Status
 304          */
 305         final public function attemptAsync() {
 306                 $this->async = true;
 307                 $result = $this->attempt();
 308                 $this->async = false;
 309
 310                 return $result;
 311         }
 312
 313         /**
 314          * Get the file operation parameters
 315          *
 316          * @return array (required params list, optional params list, list of params that are paths)
 317          */
 318         protected function allowedParams() {
 319                 return array( array(), array(), array() );
 320         }
 321
 322         /**
 323          * Adjust params to FileBackendStore internal file calls
 324          *
 325          * @param array $params
 326          * @return array (required params list, optional params list)
 327          */
 328         protected function setFlags( array $params ) {
 329                 return array( 'async' => $this->async ) + $params;
 330         }
 331
 332         /**
 333          * Get a list of storage paths read from for this operation
 334          *
 335          * @return array
 336          */
 337         public function storagePathsRead() {
 338                 return array();
 339         }
 340
 341         /**
 342          * Get a list of storage paths written to for this operation
 343          *
 344          * @return array
 345          */
 346         public function storagePathsChanged() {
 347                 return array();
 348         }
 349
 350         /**
 351          * Check for errors with regards to the destination file already existing.
 352          * Also set the destExists, overwriteSameCase and sourceSha1 member variables.
 353          * A bad status will be returned if there is no chance it can be overwritten.
 354          *
 355          * @param array $predicates
 356          * @return Status
 357          */
 358         protected function precheckDestExistence( array $predicates ) {
 359                 $status = Status::newGood();
 360                 // Get hash of source file/string and the destination file
 361                 $this->sourceSha1 = $this->getSourceSha1Base36(); // FS file or data string
 362                 if ( $this->sourceSha1 === null ) { // file in storage?
 363                         $this->sourceSha1 = $this->fileSha1( $this->params['src'], $predicates );
 364                 }
 365                 $this->overwriteSameCase = false;
 366                 $this->destExists = $this->fileExists( $this->params['dst'], $predicates );
 367                 if ( $this->destExists ) {
 368                         if ( $this->getParam( 'overwrite' ) ) {
 369                                 return $status; // OK
 370                         } elseif ( $this->getParam( 'overwriteSame' ) ) {
 371                                 $dhash = $this->fileSha1( $this->params['dst'], $predicates );
 372                                 // Check if hashes are valid and match each other...
 373                                 if ( !strlen( $this->sourceSha1 ) || !strlen( $dhash ) ) {
 374                                         $status->fatal( 'backend-fail-hashes' );
 375                                 } elseif ( $this->sourceSha1 !== $dhash ) {
 376                                         // Give an error if the files are not identical
 377                                         $status->fatal( 'backend-fail-notsame', $this->params['dst'] );
 378                                 } else {
 379                                         $this->overwriteSameCase = true; // OK
 380                                 }
 381
 382                                 return $status; // do nothing; either OK or bad status
 383                         } else {
 384                                 $status->fatal( 'backend-fail-alreadyexists', $this->params['dst'] );
 385
 386                                 return $status;
 387                         }
 388                 }
 389
 390                 return $status;
 391         }
 392
 393         /**
 394          * precheckDestExistence() helper function to get the source file SHA-1.
 395          * Subclasses should overwride this if the source is not in storage.
 396          *
 397          * @return string|bool Returns false on failure
 398          */
 399         protected function getSourceSha1Base36() {
 400                 return null; // N/A
 401         }
 402
 403         /**
 404          * Check if a file will exist in storage when this operation is attempted
 405          *
 406          * @param string $source Storage path
 407          * @param array $predicates
 408          * @return bool
 409          */
 410         final protected function fileExists( $source, array $predicates ) {
 411                 if ( isset( $predicates['exists'][$source] ) ) {
 412                         return $predicates['exists'][$source]; // previous op assures this
 413                 } else {
 414                         $params = array( 'src' => $source, 'latest' => true );
 415
 416                         return $this->backend->fileExists( $params );
 417                 }
 418         }
 419
 420         /**
 421          * Get the SHA-1 of a file in storage when this operation is attempted
 422          *
 423          * @param string $source Storage path
 424          * @param array $predicates
 425          * @return string|bool False on failure
 426          */
 427         final protected function fileSha1( $source, array $predicates ) {
 428                 if ( isset( $predicates['sha1'][$source] ) ) {
 429                         return $predicates['sha1'][$source]; // previous op assures this
 430                 } elseif ( isset( $predicates['exists'][$source] ) && !$predicates['exists'][$source] ) {
 431                         return false; // previous op assures this
 432                 } else {
 433                         $params = array( 'src' => $source, 'latest' => true );
 434
 435                         return $this->backend->getFileSha1Base36( $params );
 436                 }
 437         }
 438
 439         /**
 440          * Get the backend this operation is for
 441          *
 442          * @return FileBackendStore
 443          */
 444         public function getBackend() {
 445                 return $this->backend;
 446         }
 447
 448         /**
 449          * Log a file operation failure and preserve any temp files
 450          *
 451          * @param string $action
 452          */
 453         final public function logFailure( $action ) {
 454                 $params = $this->params;
 455                 $params['failedAction'] = $action;
 456                 try {
 457                         wfDebugLog( 'FileOperation', get_class( $this ) .
 458                                 " failed (batch #{$this->batchId}): " . FormatJson::encode( $params ) );
 459                 } catch ( Exception $e ) {
 460                         // bad config? debug log error?
 461                 }
 462         }
 463 }
 464
 465 /**
 466  * Create a file in the backend with the given content.
 467  * Parameters for this operation are outlined in FileBackend::doOperations().
 468  */
 469 class CreateFileOp extends FileOp {
 470         protected function allowedParams() {
 471                 return array(
 472                         array( 'content', 'dst' ),
 473                         array( 'overwrite', 'overwriteSame', 'headers' ),
 474                         array( 'dst' )
 475                 );
 476         }
 477
 478         protected function doPrecheck( array &$predicates ) {
 479                 $status = Status::newGood();
 480                 // Check if the source data is too big
 481                 if ( strlen( $this->getParam( 'content' ) ) > $this->backend->maxFileSizeInternal() ) {
 482                         $status->fatal( 'backend-fail-maxsize',
 483                                 $this->params['dst'], $this->backend->maxFileSizeInternal() );
 484                         $status->fatal( 'backend-fail-create', $this->params['dst'] );
 485
 486                         return $status;
 487                 // Check if a file can be placed/changed at the destination
 488                 } elseif ( !$this->backend->isPathUsableInternal( $this->params['dst'] ) ) {
 489                         $status->fatal( 'backend-fail-usable', $this->params['dst'] );
 490                         $status->fatal( 'backend-fail-create', $this->params['dst'] );
 491
 492                         return $status;
 493                 }
 494                 // Check if destination file exists
 495                 $status->merge( $this->precheckDestExistence( $predicates ) );
 496                 $this->params['dstExists'] = $this->destExists; // see FileBackendStore::setFileCache()
 497                 if ( $status->isOK() ) {
 498                         // Update file existence predicates
 499                         $predicates['exists'][$this->params['dst']] = true;
 500                         $predicates['sha1'][$this->params['dst']] = $this->sourceSha1;
 501                 }
 502
 503                 return $status; // safe to call attempt()
 504         }
 505
 506         protected function doAttempt() {
 507                 if ( !$this->overwriteSameCase ) {
 508                         // Create the file at the destination
 509                         return $this->backend->createInternal( $this->setFlags( $this->params ) );
 510                 }
 511
 512                 return Status::newGood();
 513         }
 514
 515         protected function getSourceSha1Base36() {
 516                 return Wikimedia\base_convert( sha1( $this->params['content'] ), 16, 36, 31 );
 517         }
 518
 519         public function storagePathsChanged() {
 520                 return array( $this->params['dst'] );
 521         }
 522 }
 523
 524 /**
 525  * Store a file into the backend from a file on the file system.
 526  * Parameters for this operation are outlined in FileBackend::doOperations().
 527  */
 528 class StoreFileOp extends FileOp {
 529         protected function allowedParams() {
 530                 return array(
 531                         array( 'src', 'dst' ),
 532                         array( 'overwrite', 'overwriteSame', 'headers' ),
 533                         array( 'src', 'dst' )
 534                 );
 535         }
 536
 537         protected function doPrecheck( array &$predicates ) {
 538                 $status = Status::newGood();
 539                 // Check if the source file exists on the file system
 540                 if ( !is_file( $this->params['src'] ) ) {
 541                         $status->fatal( 'backend-fail-notexists', $this->params['src'] );
 542
 543                         return $status;
 544                 // Check if the source file is too big
 545                 } elseif ( filesize( $this->params['src'] ) > $this->backend->maxFileSizeInternal() ) {
 546                         $status->fatal( 'backend-fail-maxsize',
 547                                 $this->params['dst'], $this->backend->maxFileSizeInternal() );
 548                         $status->fatal( 'backend-fail-store', $this->params['src'], $this->params['dst'] );
 549
 550                         return $status;
 551                 // Check if a file can be placed/changed at the destination
 552                 } elseif ( !$this->backend->isPathUsableInternal( $this->params['dst'] ) ) {
 553                         $status->fatal( 'backend-fail-usable', $this->params['dst'] );
 554                         $status->fatal( 'backend-fail-store', $this->params['src'], $this->params['dst'] );
 555
 556                         return $status;
 557                 }
 558                 // Check if destination file exists
 559                 $status->merge( $this->precheckDestExistence( $predicates ) );
 560                 $this->params['dstExists'] = $this->destExists; // see FileBackendStore::setFileCache()
 561                 if ( $status->isOK() ) {
 562                         // Update file existence predicates
 563                         $predicates['exists'][$this->params['dst']] = true;
 564                         $predicates['sha1'][$this->params['dst']] = $this->sourceSha1;
 565                 }
 566
 567                 return $status; // safe to call attempt()
 568         }
 569
 570         protected function doAttempt() {
 571                 if ( !$this->overwriteSameCase ) {
 572                         // Store the file at the destination
 573                         return $this->backend->storeInternal( $this->setFlags( $this->params ) );
 574                 }
 575
 576                 return Status::newGood();
 577         }
 578
 579         protected function getSourceSha1Base36() {
 580                 MediaWiki\suppressWarnings();
 581                 $hash = sha1_file( $this->params['src'] );
 582                 MediaWiki\restoreWarnings();
 583                 if ( $hash !== false ) {
 584                         $hash = Wikimedia\base_convert( $hash, 16, 36, 31 );
 585                 }
 586
 587                 return $hash;
 588         }
 589
 590         public function storagePathsChanged() {
 591                 return array( $this->params['dst'] );
 592         }
 593 }
 594
 595 /**
 596  * Copy a file from one storage path to another in the backend.
 597  * Parameters for this operation are outlined in FileBackend::doOperations().
 598  */
 599 class CopyFileOp extends FileOp {
 600         protected function allowedParams() {
 601                 return array(
 602                         array( 'src', 'dst' ),
 603                         array( 'overwrite', 'overwriteSame', 'ignoreMissingSource', 'headers' ),
 604                         array( 'src', 'dst' )
 605                 );
 606         }
 607
 608         protected function doPrecheck( array &$predicates ) {
 609                 $status = Status::newGood();
 610                 // Check if the source file exists
 611                 if ( !$this->fileExists( $this->params['src'], $predicates ) ) {
 612                         if ( $this->getParam( 'ignoreMissingSource' ) ) {
 613                                 $this->doOperation = false; // no-op
 614                                 // Update file existence predicates (cache 404s)
 615                                 $predicates['exists'][$this->params['src']] = false;
 616                                 $predicates['sha1'][$this->params['src']] = false;
 617
 618                                 return $status; // nothing to do
 619                         } else {
 620                                 $status->fatal( 'backend-fail-notexists', $this->params['src'] );
 621
 622                                 return $status;
 623                         }
 624                         // Check if a file can be placed/changed at the destination
 625                 } elseif ( !$this->backend->isPathUsableInternal( $this->params['dst'] ) ) {
 626                         $status->fatal( 'backend-fail-usable', $this->params['dst'] );
 627                         $status->fatal( 'backend-fail-copy', $this->params['src'], $this->params['dst'] );
 628
 629                         return $status;
 630                 }
 631                 // Check if destination file exists
 632                 $status->merge( $this->precheckDestExistence( $predicates ) );
 633                 $this->params['dstExists'] = $this->destExists; // see FileBackendStore::setFileCache()
 634                 if ( $status->isOK() ) {
 635                         // Update file existence predicates
 636                         $predicates['exists'][$this->params['dst']] = true;
 637                         $predicates['sha1'][$this->params['dst']] = $this->sourceSha1;
 638                 }
 639
 640                 return $status; // safe to call attempt()
 641         }
 642
 643         protected function doAttempt() {
 644                 if ( $this->overwriteSameCase ) {
 645                         $status = Status::newGood(); // nothing to do
 646                 } elseif ( $this->params['src'] === $this->params['dst'] ) {
 647                         // Just update the destination file headers
 648                         $headers = $this->getParam( 'headers' ) ?: array();
 649                         $status = $this->backend->describeInternal( $this->setFlags( array(
 650                                 'src' => $this->params['dst'], 'headers' => $headers
 651                         ) ) );
 652                 } else {
 653                         // Copy the file to the destination
 654                         $status = $this->backend->copyInternal( $this->setFlags( $this->params ) );
 655                 }
 656
 657                 return $status;
 658         }
 659
 660         public function storagePathsRead() {
 661                 return array( $this->params['src'] );
 662         }
 663
 664         public function storagePathsChanged() {
 665                 return array( $this->params['dst'] );
 666         }
 667 }
 668
 669 /**
 670  * Move a file from one storage path to another in the backend.
 671  * Parameters for this operation are outlined in FileBackend::doOperations().
 672  */
 673 class MoveFileOp extends FileOp {
 674         protected function allowedParams() {
 675                 return array(
 676                         array( 'src', 'dst' ),
 677                         array( 'overwrite', 'overwriteSame', 'ignoreMissingSource', 'headers' ),
 678                         array( 'src', 'dst' )
 679                 );
 680         }
 681
 682         protected function doPrecheck( array &$predicates ) {
 683                 $status = Status::newGood();
 684                 // Check if the source file exists
 685                 if ( !$this->fileExists( $this->params['src'], $predicates ) ) {
 686                         if ( $this->getParam( 'ignoreMissingSource' ) ) {
 687                                 $this->doOperation = false; // no-op
 688                                 // Update file existence predicates (cache 404s)
 689                                 $predicates['exists'][$this->params['src']] = false;
 690                                 $predicates['sha1'][$this->params['src']] = false;
 691
 692                                 return $status; // nothing to do
 693                         } else {
 694                                 $status->fatal( 'backend-fail-notexists', $this->params['src'] );
 695
 696                                 return $status;
 697                         }
 698                 // Check if a file can be placed/changed at the destination
 699                 } elseif ( !$this->backend->isPathUsableInternal( $this->params['dst'] ) ) {
 700                         $status->fatal( 'backend-fail-usable', $this->params['dst'] );
 701                         $status->fatal( 'backend-fail-move', $this->params['src'], $this->params['dst'] );
 702
 703                         return $status;
 704                 }
 705                 // Check if destination file exists
 706                 $status->merge( $this->precheckDestExistence( $predicates ) );
 707                 $this->params['dstExists'] = $this->destExists; // see FileBackendStore::setFileCache()
 708                 if ( $status->isOK() ) {
 709                         // Update file existence predicates
 710                         $predicates['exists'][$this->params['src']] = false;
 711                         $predicates['sha1'][$this->params['src']] = false;
 712                         $predicates['exists'][$this->params['dst']] = true;
 713                         $predicates['sha1'][$this->params['dst']] = $this->sourceSha1;
 714                 }
 715
 716                 return $status; // safe to call attempt()
 717         }
 718
 719         protected function doAttempt() {
 720                 if ( $this->overwriteSameCase ) {
 721                         if ( $this->params['src'] === $this->params['dst'] ) {
 722                                 // Do nothing to the destination (which is also the source)
 723                                 $status = Status::newGood();
 724                         } else {
 725                                 // Just delete the source as the destination file needs no changes
 726                                 $status = $this->backend->deleteInternal( $this->setFlags(
 727                                         array( 'src' => $this->params['src'] )
 728                                 ) );
 729                         }
 730                 } elseif ( $this->params['src'] === $this->params['dst'] ) {
 731                         // Just update the destination file headers
 732                         $headers = $this->getParam( 'headers' ) ?: array();
 733                         $status = $this->backend->describeInternal( $this->setFlags(
 734                                 array( 'src' => $this->params['dst'], 'headers' => $headers )
 735                         ) );
 736                 } else {
 737                         // Move the file to the destination
 738                         $status = $this->backend->moveInternal( $this->setFlags( $this->params ) );
 739                 }
 740
 741                 return $status;
 742         }
 743
 744         public function storagePathsRead() {
 745                 return array( $this->params['src'] );
 746         }
 747
 748         public function storagePathsChanged() {
 749                 return array( $this->params['src'], $this->params['dst'] );
 750         }
 751 }
 752
 753 /**
 754  * Delete a file at the given storage path from the backend.
 755  * Parameters for this operation are outlined in FileBackend::doOperations().
 756  */
 757 class DeleteFileOp extends FileOp {
 758         protected function allowedParams() {
 759                 return array( array( 'src' ), array( 'ignoreMissingSource' ), array( 'src' ) );
 760         }
 761
 762         protected function doPrecheck( array &$predicates ) {
 763                 $status = Status::newGood();
 764                 // Check if the source file exists
 765                 if ( !$this->fileExists( $this->params['src'], $predicates ) ) {
 766                         if ( $this->getParam( 'ignoreMissingSource' ) ) {
 767                                 $this->doOperation = false; // no-op
 768                                 // Update file existence predicates (cache 404s)
 769                                 $predicates['exists'][$this->params['src']] = false;
 770                                 $predicates['sha1'][$this->params['src']] = false;
 771
 772                                 return $status; // nothing to do
 773                         } else {
 774                                 $status->fatal( 'backend-fail-notexists', $this->params['src'] );
 775
 776                                 return $status;
 777                         }
 778                 // Check if a file can be placed/changed at the source
 779                 } elseif ( !$this->backend->isPathUsableInternal( $this->params['src'] ) ) {
 780                         $status->fatal( 'backend-fail-usable', $this->params['src'] );
 781                         $status->fatal( 'backend-fail-delete', $this->params['src'] );
 782
 783                         return $status;
 784                 }
 785                 // Update file existence predicates
 786                 $predicates['exists'][$this->params['src']] = false;
 787                 $predicates['sha1'][$this->params['src']] = false;
 788
 789                 return $status; // safe to call attempt()
 790         }
 791
 792         protected function doAttempt() {
 793                 // Delete the source file
 794                 return $this->backend->deleteInternal( $this->setFlags( $this->params ) );
 795         }
 796
 797         public function storagePathsChanged() {
 798                 return array( $this->params['src'] );
 799         }
 800 }
 801
 802 /**
 803  * Change metadata for a file at the given storage path in the backend.
 804  * Parameters for this operation are outlined in FileBackend::doOperations().
 805  */
 806 class DescribeFileOp extends FileOp {
 807         protected function allowedParams() {
 808                 return array( array( 'src' ), array( 'headers' ), array( 'src' ) );
 809         }
 810
 811         protected function doPrecheck( array &$predicates ) {
 812                 $status = Status::newGood();
 813                 // Check if the source file exists
 814                 if ( !$this->fileExists( $this->params['src'], $predicates ) ) {
 815                         $status->fatal( 'backend-fail-notexists', $this->params['src'] );
 816
 817                         return $status;
 818                 // Check if a file can be placed/changed at the source
 819                 } elseif ( !$this->backend->isPathUsableInternal( $this->params['src'] ) ) {
 820                         $status->fatal( 'backend-fail-usable', $this->params['src'] );
 821                         $status->fatal( 'backend-fail-describe', $this->params['src'] );
 822
 823                         return $status;
 824                 }
 825                 // Update file existence predicates
 826                 $predicates['exists'][$this->params['src']] =
 827                         $this->fileExists( $this->params['src'], $predicates );
 828                 $predicates['sha1'][$this->params['src']] =
 829                         $this->fileSha1( $this->params['src'], $predicates );
 830
 831                 return $status; // safe to call attempt()
 832         }
 833
 834         protected function doAttempt() {
 835                 // Update the source file's metadata
 836                 return $this->backend->describeInternal( $this->setFlags( $this->params ) );
 837         }
 838
 839         public function storagePathsChanged() {
 840                 return array( $this->params['src'] );
 841         }
 842 }
 843
 844 /**
 845  * Placeholder operation that has no params and does nothing
 846  */
 847 class NullFileOp extends FileOp {
 848 }