includes/Revision.php

   1 <?php
   2 /**
   3  * Representation of a page version.
   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  */
  22
  23 /**
  24  * @todo document
  25  */
  26 class Revision implements IDBAccessObject {
  27         protected $mId;
  28         protected $mPage;
  29         protected $mUserText;
  30         protected $mOrigUserText;
  31         protected $mUser;
  32         protected $mMinorEdit;
  33         protected $mTimestamp;
  34         protected $mDeleted;
  35         protected $mSize;
  36         protected $mSha1;
  37         protected $mParentId;
  38         protected $mComment;
  39         protected $mText;
  40         protected $mTextRow;
  41         protected $mTitle;
  42         protected $mCurrent;
  43         protected $mContentModel;
  44         protected $mContentFormat;
  45         protected $mContent;
  46         protected $mContentHandler;
  47
  48         // Revision deletion constants
  49         const DELETED_TEXT = 1;
  50         const DELETED_COMMENT = 2;
  51         const DELETED_USER = 4;
  52         const DELETED_RESTRICTED = 8;
  53         const SUPPRESSED_USER = 12; // convenience
  54
  55         // Audience options for accessors
  56         const FOR_PUBLIC = 1;
  57         const FOR_THIS_USER = 2;
  58         const RAW = 3;
  59
  60         /**
  61          * Load a page revision from a given revision ID number.
  62          * Returns null if no such revision can be found.
  63          *
  64          * $flags include:
  65          *      Revision::READ_LATEST  : Select the data from the master
  66          *      Revision::READ_LOCKING : Select & lock the data from the master
  67          *
  68          * @param $id Integer
  69          * @param $flags Integer (optional)
  70          * @return Revision or null
  71          */
  72         public static function newFromId( $id, $flags = 0 ) {
  73                 return self::newFromConds( array( 'rev_id' => intval( $id ) ), $flags );
  74         }
  75
  76         /**
  77          * Load either the current, or a specified, revision
  78          * that's attached to a given title. If not attached
  79          * to that title, will return null.
  80          *
  81          * $flags include:
  82          *      Revision::READ_LATEST  : Select the data from the master
  83          *      Revision::READ_LOCKING : Select & lock the data from the master
  84          *
  85          * @param $title Title
  86          * @param $id Integer (optional)
  87          * @param $flags Integer Bitfield (optional)
  88          * @return Revision or null
  89          */
  90         public static function newFromTitle( $title, $id = 0, $flags = 0 ) {
  91                 $conds = array(
  92                         'page_namespace' => $title->getNamespace(),
  93                         'page_title'     => $title->getDBkey()
  94                 );
  95                 if ( $id ) {
  96                         // Use the specified ID
  97                         $conds['rev_id'] = $id;
  98                 } else {
  99                         // Use a join to get the latest revision
 100                         $conds[] = 'rev_id=page_latest';
 101                 }
 102                 return self::newFromConds( $conds, (int)$flags );
 103         }
 104
 105         /**
 106          * Load either the current, or a specified, revision
 107          * that's attached to a given page ID.
 108          * Returns null if no such revision can be found.
 109          *
 110          * $flags include:
 111          *      Revision::READ_LATEST  : Select the data from the master
 112          *      Revision::READ_LOCKING : Select & lock the data from the master
 113          *
 114          * @param $revId Integer
 115          * @param $pageId Integer (optional)
 116          * @param $flags Integer Bitfield (optional)
 117          * @return Revision or null
 118          */
 119         public static function newFromPageId( $pageId, $revId = 0, $flags = 0 ) {
 120                 $conds = array( 'page_id' => $pageId );
 121                 if ( $revId ) {
 122                         $conds['rev_id'] = $revId;
 123                 } else {
 124                         // Use a join to get the latest revision
 125                         $conds[] = 'rev_id = page_latest';
 126                 }
 127                 return self::newFromConds( $conds, (int)$flags );
 128         }
 129
 130         /**
 131          * Make a fake revision object from an archive table row. This is queried
 132          * for permissions or even inserted (as in Special:Undelete)
 133          * @todo FIXME: Should be a subclass for RevisionDelete. [TS]
 134          *
 135          * @param $row
 136          * @param $overrides array
 137          *
 138          * @throws MWException
 139          * @return Revision
 140          */
 141         public static function newFromArchiveRow( $row, $overrides = array() ) {
 142                 global $wgContentHandlerUseDB;
 143
 144                 $attribs = $overrides + array(
 145                         'page'       => isset( $row->ar_page_id ) ? $row->ar_page_id : null,
 146                         'id'         => isset( $row->ar_rev_id ) ? $row->ar_rev_id : null,
 147                         'comment'    => $row->ar_comment,
 148                         'user'       => $row->ar_user,
 149                         'user_text'  => $row->ar_user_text,
 150                         'timestamp'  => $row->ar_timestamp,
 151                         'minor_edit' => $row->ar_minor_edit,
 152                         'text_id'    => isset( $row->ar_text_id ) ? $row->ar_text_id : null,
 153                         'deleted'    => $row->ar_deleted,
 154                         'len'        => $row->ar_len,
 155                         'sha1'       => isset( $row->ar_sha1 ) ? $row->ar_sha1 : null,
 156                         'content_model'   => isset( $row->ar_content_model ) ? $row->ar_content_model : null,
 157                         'content_format'  => isset( $row->ar_content_format ) ? $row->ar_content_format : null,
 158                 );
 159
 160                 if ( !$wgContentHandlerUseDB ) {
 161                         unset( $attribs['content_model'] );
 162                         unset( $attribs['content_format'] );
 163                 }
 164
 165                 if ( isset( $row->ar_text ) && !$row->ar_text_id ) {
 166                         // Pre-1.5 ar_text row
 167                         $attribs['text'] = self::getRevisionText( $row, 'ar_' );
 168                         if ( $attribs['text'] === false ) {
 169                                 throw new MWException( 'Unable to load text from archive row (possibly bug 22624)' );
 170                         }
 171                 }
 172                 return new self( $attribs );
 173         }
 174
 175         /**
 176          * @since 1.19
 177          *
 178          * @param $row
 179          * @return Revision
 180          */
 181         public static function newFromRow( $row ) {
 182                 return new self( $row );
 183         }
 184
 185         /**
 186          * Load a page revision from a given revision ID number.
 187          * Returns null if no such revision can be found.
 188          *
 189          * @param $db DatabaseBase
 190          * @param $id Integer
 191          * @return Revision or null
 192          */
 193         public static function loadFromId( $db, $id ) {
 194                 return self::loadFromConds( $db, array( 'rev_id' => intval( $id ) ) );
 195         }
 196
 197         /**
 198          * Load either the current, or a specified, revision
 199          * that's attached to a given page. If not attached
 200          * to that page, will return null.
 201          *
 202          * @param $db DatabaseBase
 203          * @param $pageid Integer
 204          * @param $id Integer
 205          * @return Revision or null
 206          */
 207         public static function loadFromPageId( $db, $pageid, $id = 0 ) {
 208                 $conds = array( 'rev_page' => intval( $pageid ), 'page_id'  => intval( $pageid ) );
 209                 if( $id ) {
 210                         $conds['rev_id'] = intval( $id );
 211                 } else {
 212                         $conds[] = 'rev_id=page_latest';
 213                 }
 214                 return self::loadFromConds( $db, $conds );
 215         }
 216
 217         /**
 218          * Load either the current, or a specified, revision
 219          * that's attached to a given page. If not attached
 220          * to that page, will return null.
 221          *
 222          * @param $db DatabaseBase
 223          * @param $title Title
 224          * @param $id Integer
 225          * @return Revision or null
 226          */
 227         public static function loadFromTitle( $db, $title, $id = 0 ) {
 228                 if( $id ) {
 229                         $matchId = intval( $id );
 230                 } else {
 231                         $matchId = 'page_latest';
 232                 }
 233                 return self::loadFromConds( $db,
 234                         array( "rev_id=$matchId",
 235                                    'page_namespace' => $title->getNamespace(),
 236                                    'page_title'     => $title->getDBkey() )
 237                 );
 238         }
 239
 240         /**
 241          * Load the revision for the given title with the given timestamp.
 242          * WARNING: Timestamps may in some circumstances not be unique,
 243          * so this isn't the best key to use.
 244          *
 245          * @param $db DatabaseBase
 246          * @param $title Title
 247          * @param $timestamp String
 248          * @return Revision or null
 249          */
 250         public static function loadFromTimestamp( $db, $title, $timestamp ) {
 251                 return self::loadFromConds( $db,
 252                         array( 'rev_timestamp'  => $db->timestamp( $timestamp ),
 253                                    'page_namespace' => $title->getNamespace(),
 254                                    'page_title'     => $title->getDBkey() )
 255                 );
 256         }
 257
 258         /**
 259          * Given a set of conditions, fetch a revision.
 260          *
 261          * @param $conditions Array
 262          * @param $flags integer (optional)
 263          * @return Revision or null
 264          */
 265         private static function newFromConds( $conditions, $flags = 0 ) {
 266                 $db = wfGetDB( ( $flags & self::READ_LATEST ) ? DB_MASTER : DB_SLAVE );
 267                 $rev = self::loadFromConds( $db, $conditions, $flags );
 268                 if ( is_null( $rev ) && wfGetLB()->getServerCount() > 1 ) {
 269                         if ( !( $flags & self::READ_LATEST ) ) {
 270                                 $dbw = wfGetDB( DB_MASTER );
 271                                 $rev = self::loadFromConds( $dbw, $conditions, $flags );
 272                         }
 273                 }
 274                 return $rev;
 275         }
 276
 277         /**
 278          * Given a set of conditions, fetch a revision from
 279          * the given database connection.
 280          *
 281          * @param $db DatabaseBase
 282          * @param $conditions Array
 283          * @param $flags integer (optional)
 284          * @return Revision or null
 285          */
 286         private static function loadFromConds( $db, $conditions, $flags = 0 ) {
 287                 $res = self::fetchFromConds( $db, $conditions, $flags );
 288                 if( $res ) {
 289                         $row = $res->fetchObject();
 290                         if( $row ) {
 291                                 $ret = new Revision( $row );
 292                                 return $ret;
 293                         }
 294                 }
 295                 $ret = null;
 296                 return $ret;
 297         }
 298
 299         /**
 300          * Return a wrapper for a series of database rows to
 301          * fetch all of a given page's revisions in turn.
 302          * Each row can be fed to the constructor to get objects.
 303          *
 304          * @param $title Title
 305          * @return ResultWrapper
 306          */
 307         public static function fetchRevision( $title ) {
 308                 return self::fetchFromConds(
 309                         wfGetDB( DB_SLAVE ),
 310                         array( 'rev_id=page_latest',
 311                                    'page_namespace' => $title->getNamespace(),
 312                                    'page_title'     => $title->getDBkey() )
 313                 );
 314         }
 315
 316         /**
 317          * Given a set of conditions, return a ResultWrapper
 318          * which will return matching database rows with the
 319          * fields necessary to build Revision objects.
 320          *
 321          * @param $db DatabaseBase
 322          * @param $conditions Array
 323          * @param $flags integer (optional)
 324          * @return ResultWrapper
 325          */
 326         private static function fetchFromConds( $db, $conditions, $flags = 0 ) {
 327                 $fields = array_merge(
 328                         self::selectFields(),
 329                         self::selectPageFields(),
 330                         self::selectUserFields()
 331                 );
 332                 $options = array( 'LIMIT' => 1 );
 333                 if ( ( $flags & self::READ_LOCKING ) == self::READ_LOCKING ) {
 334                         $options[] = 'FOR UPDATE';
 335                 }
 336                 return $db->select(
 337                         array( 'revision', 'page', 'user' ),
 338                         $fields,
 339                         $conditions,
 340                         __METHOD__,
 341                         $options,
 342                         array( 'page' => self::pageJoinCond(), 'user' => self::userJoinCond() )
 343                 );
 344         }
 345
 346         /**
 347          * Return the value of a select() JOIN conds array for the user table.
 348          * This will get user table rows for logged-in users.
 349          * @since 1.19
 350          * @return Array
 351          */
 352         public static function userJoinCond() {
 353                 return array( 'LEFT JOIN', array( 'rev_user != 0', 'user_id = rev_user' ) );
 354         }
 355
 356         /**
 357          * Return the value of a select() page conds array for the paeg table.
 358          * This will assure that the revision(s) are not orphaned from live pages.
 359          * @since 1.19
 360          * @return Array
 361          */
 362         public static function pageJoinCond() {
 363                 return array( 'INNER JOIN', array( 'page_id = rev_page' ) );
 364         }
 365
 366         /**
 367          * Return the list of revision fields that should be selected to create
 368          * a new revision.
 369          * @return array
 370          */
 371         public static function selectFields() {
 372                 global $wgContentHandlerUseDB;
 373
 374                 $fields = array(
 375                         'rev_id',
 376                         'rev_page',
 377                         'rev_text_id',
 378                         'rev_timestamp',
 379                         'rev_comment',
 380                         'rev_user_text',
 381                         'rev_user',
 382                         'rev_minor_edit',
 383                         'rev_deleted',
 384                         'rev_len',
 385                         'rev_parent_id',
 386                         'rev_sha1',
 387                 );
 388
 389                 if ( $wgContentHandlerUseDB ) {
 390                         $fields[] = 'rev_content_format';
 391                         $fields[] = 'rev_content_model';
 392                 }
 393
 394                 return $fields;
 395         }
 396
 397         /**
 398          * Return the list of text fields that should be selected to read the
 399          * revision text
 400          * @return array
 401          */
 402         public static function selectTextFields() {
 403                 return array(
 404                         'old_text',
 405                         'old_flags'
 406                 );
 407         }
 408
 409         /**
 410          * Return the list of page fields that should be selected from page table
 411          * @return array
 412          */
 413         public static function selectPageFields() {
 414                 return array(
 415                         'page_namespace',
 416                         'page_title',
 417                         'page_id',
 418                         'page_latest',
 419                         'page_is_redirect',
 420                         'page_len',
 421                 );
 422         }
 423
 424         /**
 425          * Return the list of user fields that should be selected from user table
 426          * @return array
 427          */
 428         public static function selectUserFields() {
 429                 return array( 'user_name' );
 430         }
 431
 432         /**
 433          * Do a batched query to get the parent revision lengths
 434          * @param $db DatabaseBase
 435          * @param $revIds Array
 436          * @return array
 437          */
 438         public static function getParentLengths( $db, array $revIds ) {
 439                 $revLens = array();
 440                 if ( !$revIds ) {
 441                         return $revLens; // empty
 442                 }
 443                 wfProfileIn( __METHOD__ );
 444                 $res = $db->select( 'revision',
 445                         array( 'rev_id', 'rev_len' ),
 446                         array( 'rev_id' => $revIds ),
 447                         __METHOD__ );
 448                 foreach ( $res as $row ) {
 449                         $revLens[$row->rev_id] = $row->rev_len;
 450                 }
 451                 wfProfileOut( __METHOD__ );
 452                 return $revLens;
 453         }
 454
 455         /**
 456          * Constructor
 457          *
 458          * @param $row Mixed: either a database row or an array
 459          * @throws MWException
 460          * @access private
 461          */
 462         function __construct( $row ) {
 463                 if( is_object( $row ) ) {
 464                         $this->mId        = intval( $row->rev_id );
 465                         $this->mPage      = intval( $row->rev_page );
 466                         $this->mTextId    = intval( $row->rev_text_id );
 467                         $this->mComment   =         $row->rev_comment;
 468                         $this->mUser      = intval( $row->rev_user );
 469                         $this->mMinorEdit = intval( $row->rev_minor_edit );
 470                         $this->mTimestamp =         $row->rev_timestamp;
 471                         $this->mDeleted   = intval( $row->rev_deleted );
 472
 473                         if( !isset( $row->rev_parent_id ) ) {
 474                                 $this->mParentId = is_null( $row->rev_parent_id ) ? null : 0;
 475                         } else {
 476                                 $this->mParentId  = intval( $row->rev_parent_id );
 477                         }
 478
 479                         if( !isset( $row->rev_len ) || is_null( $row->rev_len ) ) {
 480                                 $this->mSize = null;
 481                         } else {
 482                                 $this->mSize = intval( $row->rev_len );
 483                         }
 484
 485                         if ( !isset( $row->rev_sha1 ) ) {
 486                                 $this->mSha1 = null;
 487                         } else {
 488                                 $this->mSha1 = $row->rev_sha1;
 489                         }
 490
 491                         if( isset( $row->page_latest ) ) {
 492                                 $this->mCurrent = ( $row->rev_id == $row->page_latest );
 493                                 $this->mTitle = Title::newFromRow( $row );
 494                         } else {
 495                                 $this->mCurrent = false;
 496                                 $this->mTitle = null;
 497                         }
 498
 499                         if( !isset( $row->rev_content_model ) || is_null( $row->rev_content_model ) ) {
 500                                 $this->mContentModel = null; # determine on demand if needed
 501                         } else {
 502                                 $this->mContentModel = strval( $row->rev_content_model );
 503                         }
 504
 505                         if( !isset( $row->rev_content_format ) || is_null( $row->rev_content_format ) ) {
 506                                 $this->mContentFormat = null; # determine on demand if needed
 507                         } else {
 508                                 $this->mContentFormat = strval( $row->rev_content_format );
 509                         }
 510
 511                         // Lazy extraction...
 512                         $this->mText      = null;
 513                         if( isset( $row->old_text ) ) {
 514                                 $this->mTextRow = $row;
 515                         } else {
 516                                 // 'text' table row entry will be lazy-loaded
 517                                 $this->mTextRow = null;
 518                         }
 519
 520                         // Use user_name for users and rev_user_text for IPs...
 521                         $this->mUserText = null; // lazy load if left null
 522                         if ( $this->mUser == 0 ) {
 523                                 $this->mUserText = $row->rev_user_text; // IP user
 524                         } elseif ( isset( $row->user_name ) ) {
 525                                 $this->mUserText = $row->user_name; // logged-in user
 526                         }
 527                         $this->mOrigUserText = $row->rev_user_text;
 528                 } elseif( is_array( $row ) ) {
 529                         // Build a new revision to be saved...
 530                         global $wgUser; // ugh
 531
 532
 533                         # if we have a content object, use it to set the model and type
 534                         if ( !empty( $row['content'] ) ) {
 535                                 //@todo: when is that set? test with external store setup! check out insertOn() [dk]
 536                                 if ( !empty( $row['text_id'] ) ) {
 537                                         throw new MWException( "Text already stored in external store (id {$row['text_id']}), "
 538                                                                                         . "can't serialize content object" );
 539                                 }
 540
 541                                 $row['content_model'] = $row['content']->getModel();
 542                                 # note: mContentFormat is initializes later accordingly
 543                                 # note: content is serialized later in this method!
 544                                 # also set text to null?
 545                         }
 546
 547                         $this->mId        = isset( $row['id']         ) ? intval( $row['id']         ) : null;
 548                         $this->mPage      = isset( $row['page']       ) ? intval( $row['page']       ) : null;
 549                         $this->mTextId    = isset( $row['text_id']    ) ? intval( $row['text_id']    ) : null;
 550                         $this->mUserText  = isset( $row['user_text']  ) ? strval( $row['user_text']  ) : $wgUser->getName();
 551                         $this->mUser      = isset( $row['user']       ) ? intval( $row['user']       ) : $wgUser->getId();
 552                         $this->mMinorEdit = isset( $row['minor_edit'] ) ? intval( $row['minor_edit'] ) : 0;
 553                         $this->mTimestamp = isset( $row['timestamp']  ) ? strval( $row['timestamp']  ) : wfTimestampNow();
 554                         $this->mDeleted   = isset( $row['deleted']    ) ? intval( $row['deleted']    ) : 0;
 555                         $this->mSize      = isset( $row['len']        ) ? intval( $row['len']        ) : null;
 556                         $this->mParentId  = isset( $row['parent_id']  ) ? intval( $row['parent_id']  ) : null;
 557                         $this->mSha1      = isset( $row['sha1']  )      ? strval( $row['sha1']  )      : null;
 558
 559                         $this->mContentModel   = isset( $row['content_model']  )  ? strval( $row['content_model'] )  : null;
 560                         $this->mContentFormat  = isset( $row['content_format']  ) ? strval( $row['content_format'] ) : null;
 561
 562                         // Enforce spacing trimming on supplied text
 563                         $this->mComment   = isset( $row['comment']    ) ?  trim( strval( $row['comment'] ) ) : null;
 564                         $this->mText      = isset( $row['text']       ) ? rtrim( strval( $row['text']    ) ) : null;
 565                         $this->mTextRow   = null;
 566
 567                         $this->mTitle     = isset( $row['title']      ) ? $row['title'] : null;
 568
 569                         // if we have a Content object, override mText and mContentModel
 570                         if ( !empty( $row['content'] ) ) {
 571                                 if ( !( $row['content'] instanceof Content ) ) {
 572                                         throw new MWException( '`content` field must contain a Content object.' );
 573                                 }
 574
 575                                 $handler = $this->getContentHandler();
 576                                 $this->mContent = $row['content'];
 577
 578                                 $this->mContentModel = $this->mContent->getModel();
 579                                 $this->mContentHandler = null;
 580
 581                                 $this->mText = $handler->serializeContent( $row['content'], $this->getContentFormat() );
 582                         } elseif ( !is_null( $this->mText ) ) {
 583                                 $handler = $this->getContentHandler();
 584                                 $this->mContent = $handler->unserializeContent( $this->mText );
 585                         }
 586
 587                         // if we have a Title object, override mPage. Useful for testing and convenience.
 588                         if ( isset( $row['title'] ) ) {
 589                                 $this->mTitle     = $row['title'];
 590                                 $this->mPage      = $this->mTitle->getArticleID();
 591                         } else {
 592                                 $this->mTitle     = null; // Load on demand if needed
 593                         }
 594
 595                         // @todo: XXX: really? we are about to create a revision. it will usually then be the current one.
 596                         $this->mCurrent   = false;
 597
 598                         // If we still have no length, see it we have the text to figure it out
 599                         if ( !$this->mSize ) {
 600                                 if ( !is_null( $this->mContent ) ) {
 601                                         $this->mSize = $this->mContent->getSize();
 602                                 } else {
 603                                         #NOTE: this should never happen if we have either text or content object!
 604                                         $this->mSize = null;
 605                                 }
 606                         }
 607
 608                         // Same for sha1
 609                         if ( $this->mSha1 === null ) {
 610                                 $this->mSha1 = is_null( $this->mText ) ? null : self::base36Sha1( $this->mText );
 611                         }
 612
 613                         // force lazy init
 614                         $this->getContentModel();
 615                         $this->getContentFormat();
 616                 } else {
 617                         throw new MWException( 'Revision constructor passed invalid row format.' );
 618                 }
 619                 $this->mUnpatrolled = null;
 620         }
 621
 622         /**
 623          * Get revision ID
 624          *
 625          * @return Integer|null
 626          */
 627         public function getId() {
 628                 return $this->mId;
 629         }
 630
 631         /**
 632          * Set the revision ID
 633          *
 634          * @since 1.19
 635          * @param $id Integer
 636          */
 637         public function setId( $id ) {
 638                 $this->mId = $id;
 639         }
 640
 641         /**
 642          * Get text row ID
 643          *
 644          * @return Integer|null
 645          */
 646         public function getTextId() {
 647                 return $this->mTextId;
 648         }
 649
 650         /**
 651          * Get parent revision ID (the original previous page revision)
 652          *
 653          * @return Integer|null
 654          */
 655         public function getParentId() {
 656                 return $this->mParentId;
 657         }
 658
 659         /**
 660          * Returns the length of the text in this revision, or null if unknown.
 661          *
 662          * @return Integer|null
 663          */
 664         public function getSize() {
 665                 return $this->mSize;
 666         }
 667
 668         /**
 669          * Returns the base36 sha1 of the text in this revision, or null if unknown.
 670          *
 671          * @return String|null
 672          */
 673         public function getSha1() {
 674                 return $this->mSha1;
 675         }
 676
 677         /**
 678          * Returns the title of the page associated with this entry or null.
 679          *
 680          * Will do a query, when title is not set and id is given.
 681          *
 682          * @return Title|null
 683          */
 684         public function getTitle() {
 685                 if( isset( $this->mTitle ) ) {
 686                         return $this->mTitle;
 687                 }
 688                 if( !is_null( $this->mId ) ) { //rev_id is defined as NOT NULL, but this revision may not yet have been inserted.
 689                         $dbr = wfGetDB( DB_SLAVE );
 690                         $row = $dbr->selectRow(
 691                                 array( 'page', 'revision' ),
 692                                 self::selectPageFields(),
 693                                 array( 'page_id=rev_page',
 694                                            'rev_id' => $this->mId ),
 695                                 __METHOD__ );
 696                         if ( $row ) {
 697                                 $this->mTitle = Title::newFromRow( $row );
 698                         }
 699                 }
 700
 701                 if ( !$this->mTitle && !is_null( $this->mPage ) && $this->mPage > 0 ) {
 702                         $this->mTitle = Title::newFromID( $this->mPage );
 703                 }
 704
 705                 return $this->mTitle;
 706         }
 707
 708         /**
 709          * Set the title of the revision
 710          *
 711          * @param $title Title
 712          */
 713         public function setTitle( $title ) {
 714                 $this->mTitle = $title;
 715         }
 716
 717         /**
 718          * Get the page ID
 719          *
 720          * @return Integer|null
 721          */
 722         public function getPage() {
 723                 return $this->mPage;
 724         }
 725
 726         /**
 727          * Fetch revision's user id if it's available to the specified audience.
 728          * If the specified audience does not have access to it, zero will be
 729          * returned.
 730          *
 731          * @param $audience Integer: one of:
 732          *      Revision::FOR_PUBLIC       to be displayed to all users
 733          *      Revision::FOR_THIS_USER    to be displayed to the given user
 734          *      Revision::RAW              get the ID regardless of permissions
 735          * @param $user User object to check for, only if FOR_THIS_USER is passed
 736          *              to the $audience parameter
 737          * @return Integer
 738          */
 739         public function getUser( $audience = self::FOR_PUBLIC, User $user = null ) {
 740                 if( $audience == self::FOR_PUBLIC && $this->isDeleted( self::DELETED_USER ) ) {
 741                         return 0;
 742                 } elseif( $audience == self::FOR_THIS_USER && !$this->userCan( self::DELETED_USER, $user ) ) {
 743                         return 0;
 744                 } else {
 745                         return $this->mUser;
 746                 }
 747         }
 748
 749         /**
 750          * Fetch revision's user id without regard for the current user's permissions
 751          *
 752          * @return String
 753          */
 754         public function getRawUser() {
 755                 return $this->mUser;
 756         }
 757
 758         /**
 759          * Fetch revision's username if it's available to the specified audience.
 760          * If the specified audience does not have access to the username, an
 761          * empty string will be returned.
 762          *
 763          * @param $audience Integer: one of:
 764          *      Revision::FOR_PUBLIC       to be displayed to all users
 765          *      Revision::FOR_THIS_USER    to be displayed to the given user
 766          *      Revision::RAW              get the text regardless of permissions
 767          * @param $user User object to check for, only if FOR_THIS_USER is passed
 768          *              to the $audience parameter
 769          * @return string
 770          */
 771         public function getUserText( $audience = self::FOR_PUBLIC, User $user = null ) {
 772                 if( $audience == self::FOR_PUBLIC && $this->isDeleted( self::DELETED_USER ) ) {
 773                         return '';
 774                 } elseif( $audience == self::FOR_THIS_USER && !$this->userCan( self::DELETED_USER, $user ) ) {
 775                         return '';
 776                 } else {
 777                         return $this->getRawUserText();
 778                 }
 779         }
 780
 781         /**
 782          * Fetch revision's username without regard for view restrictions
 783          *
 784          * @return String
 785          */
 786         public function getRawUserText() {
 787                 if ( $this->mUserText === null ) {
 788                         $this->mUserText = User::whoIs( $this->mUser ); // load on demand
 789                         if ( $this->mUserText === false ) {
 790                                 # This shouldn't happen, but it can if the wiki was recovered
 791                                 # via importing revs and there is no user table entry yet.
 792                                 $this->mUserText = $this->mOrigUserText;
 793                         }
 794                 }
 795                 return $this->mUserText;
 796         }
 797
 798         /**
 799          * Fetch revision comment if it's available to the specified audience.
 800          * If the specified audience does not have access to the comment, an
 801          * empty string will be returned.
 802          *
 803          * @param $audience Integer: one of:
 804          *      Revision::FOR_PUBLIC       to be displayed to all users
 805          *      Revision::FOR_THIS_USER    to be displayed to the given user
 806          *      Revision::RAW              get the text regardless of permissions
 807          * @param $user User object to check for, only if FOR_THIS_USER is passed
 808          *              to the $audience parameter
 809          * @return String
 810          */
 811         function getComment( $audience = self::FOR_PUBLIC, User $user = null ) {
 812                 if( $audience == self::FOR_PUBLIC && $this->isDeleted( self::DELETED_COMMENT ) ) {
 813                         return '';
 814                 } elseif( $audience == self::FOR_THIS_USER && !$this->userCan( self::DELETED_COMMENT, $user ) ) {
 815                         return '';
 816                 } else {
 817                         return $this->mComment;
 818                 }
 819         }
 820
 821         /**
 822          * Fetch revision comment without regard for the current user's permissions
 823          *
 824          * @return String
 825          */
 826         public function getRawComment() {
 827                 return $this->mComment;
 828         }
 829
 830         /**
 831          * @return Boolean
 832          */
 833         public function isMinor() {
 834                 return (bool)$this->mMinorEdit;
 835         }
 836
 837         /**
 838          * @return Integer rcid of the unpatrolled row, zero if there isn't one
 839          */
 840         public function isUnpatrolled() {
 841                 if( $this->mUnpatrolled !== null ) {
 842                         return $this->mUnpatrolled;
 843                 }
 844                 $dbr = wfGetDB( DB_SLAVE );
 845                 $this->mUnpatrolled = $dbr->selectField( 'recentchanges',
 846                         'rc_id',
 847                         array( // Add redundant user,timestamp condition so we can use the existing index
 848                                 'rc_user_text'  => $this->getRawUserText(),
 849                                 'rc_timestamp'  => $dbr->timestamp( $this->getTimestamp() ),
 850                                 'rc_this_oldid' => $this->getId(),
 851                                 'rc_patrolled'  => 0
 852                         ),
 853                         __METHOD__
 854                 );
 855                 return (int)$this->mUnpatrolled;
 856         }
 857
 858         /**
 859          * @param $field int one of DELETED_* bitfield constants
 860          *
 861          * @return Boolean
 862          */
 863         public function isDeleted( $field ) {
 864                 return ( $this->mDeleted & $field ) == $field;
 865         }
 866
 867         /**
 868          * Get the deletion bitfield of the revision
 869          *
 870          * @return int
 871          */
 872         public function getVisibility() {
 873                 return (int)$this->mDeleted;
 874         }
 875
 876         /**
 877          * Fetch revision text if it's available to the specified audience.
 878          * If the specified audience does not have the ability to view this
 879          * revision, an empty string will be returned.
 880          *
 881          * @param $audience Integer: one of:
 882          *      Revision::FOR_PUBLIC       to be displayed to all users
 883          *      Revision::FOR_THIS_USER    to be displayed to the given user
 884          *      Revision::RAW              get the text regardless of permissions
 885          * @param $user User object to check for, only if FOR_THIS_USER is passed
 886          *              to the $audience parameter
 887          *
 888          * @deprecated in 1.21, use getContent() instead
 889          * @todo: replace usage in core
 890          * @return String
 891          */
 892         public function getText( $audience = self::FOR_PUBLIC, User $user = null ) {
 893                 ContentHandler::deprecated( __METHOD__, '1.21' );
 894
 895                 $content = $this->getContent( $audience, $user );
 896                 return ContentHandler::getContentText( $content ); # returns the raw content text, if applicable
 897         }
 898
 899         /**
 900          * Fetch revision content if it's available to the specified audience.
 901          * If the specified audience does not have the ability to view this
 902          * revision, null will be returned.
 903          *
 904          * @param $audience Integer: one of:
 905          *      Revision::FOR_PUBLIC       to be displayed to all users
 906          *      Revision::FOR_THIS_USER    to be displayed to $wgUser
 907          *      Revision::RAW              get the text regardless of permissions
 908          * @param $user User object to check for, only if FOR_THIS_USER is passed
 909          *              to the $audience parameter
 910          * @since 1.21
 911          * @return Content
 912          */
 913         public function getContent( $audience = self::FOR_PUBLIC, User $user = null ) {
 914                 if( $audience == self::FOR_PUBLIC && $this->isDeleted( self::DELETED_TEXT ) ) {
 915                         return null;
 916                 } elseif( $audience == self::FOR_THIS_USER && !$this->userCan( self::DELETED_TEXT, $user ) ) {
 917                         return null;
 918                 } else {
 919                         return $this->getContentInternal();
 920                 }
 921         }
 922
 923         /**
 924          * Alias for getText(Revision::FOR_THIS_USER)
 925          *
 926          * @deprecated since 1.17
 927          * @return String
 928          */
 929         public function revText() {
 930                 wfDeprecated( __METHOD__, '1.17' );
 931                 return $this->getText( self::FOR_THIS_USER );
 932         }
 933
 934         /**
 935          * Fetch revision text without regard for view restrictions
 936          *
 937          * @return String
 938          *
 939          * @deprecated since 1.21. Instead, use Revision::getContent( Revision::RAW )
 940          *                         or Revision::getSerializedData() as appropriate.
 941          */
 942         public function getRawText() {
 943                 ContentHandler::deprecated( __METHOD__, "1.21" );
 944
 945                 return $this->getText( self::RAW );
 946         }
 947
 948         /**
 949          * Fetch original serialized data without regard for view restrictions
 950          *
 951          * @since 1.21
 952          * @return String
 953          */
 954         public function getSerializedData() {
 955                 return $this->mText;
 956         }
 957
 958         /**
 959          * Gets the content object for the revision
 960          *
 961          * @since 1.21
 962          * @return Content
 963          */
 964         protected function getContentInternal() {
 965                 if( is_null( $this->mContent ) ) {
 966                         // Revision is immutable. Load on demand:
 967
 968                         $handler = $this->getContentHandler();
 969                         $format = $this->getContentFormat();
 970                         $title = $this->getTitle();
 971
 972                         if( is_null( $this->mText ) ) {
 973                                 // Load text on demand:
 974                                 $this->mText = $this->loadText();
 975                         }
 976
 977                         $this->mContent = is_null( $this->mText ) ? null : $handler->unserializeContent( $this->mText, $format );
 978                 }
 979
 980                 return $this->mContent->copy(); // NOTE: copy() will return $this for immutable content objects
 981         }
 982
 983         /**
 984          * Returns the content model for this revision.
 985          *
 986          * If no content model was stored in the database, $this->getTitle()->getContentModel() is
 987          * used to determine the content model to use. If no title is know, CONTENT_MODEL_WIKITEXT
 988          * is used as a last resort.
 989          *
 990          * @return String the content model id associated with this revision, see the CONTENT_MODEL_XXX constants.
 991          **/
 992         public function getContentModel() {
 993                 if ( !$this->mContentModel ) {
 994                         $title = $this->getTitle();
 995                         $this->mContentModel = ( $title ? $title->getContentModel() : CONTENT_MODEL_WIKITEXT );
 996
 997                         assert( !empty( $this->mContentModel ) );
 998                 }
 999
1000                 return $this->mContentModel;
1001         }
1002
1003         /**
1004          * Returns the content format for this revision.
1005          *
1006          * If no content format was stored in the database, the default format for this
1007          * revision's content model is returned.
1008          *
1009          * @return String the content format id associated with this revision, see the CONTENT_FORMAT_XXX constants.
1010          **/
1011         public function getContentFormat() {
1012                 if ( !$this->mContentFormat ) {
1013                         $handler = $this->getContentHandler();
1014                         $this->mContentFormat = $handler->getDefaultFormat();
1015
1016                         assert( !empty( $this->mContentFormat ) );
1017                 }
1018
1019                 return $this->mContentFormat;
1020         }
1021
1022         /**
1023          * Returns the content handler appropriate for this revision's content model.
1024          *
1025          * @return ContentHandler
1026          */
1027         public function getContentHandler() {
1028                 if ( !$this->mContentHandler ) {
1029                         $model = $this->getContentModel();
1030                         $this->mContentHandler = ContentHandler::getForModelID( $model );
1031
1032                         $format = $this->getContentFormat();
1033
1034                         if ( !$this->mContentHandler->isSupportedFormat( $format ) ) {
1035                                 throw new MWException( "Oops, the content format $format is not supported for this content model, $model" );
1036                         }
1037                 }
1038
1039                 return $this->mContentHandler;
1040         }
1041
1042         /**
1043          * @return String
1044          */
1045         public function getTimestamp() {
1046                 return wfTimestamp( TS_MW, $this->mTimestamp );
1047         }
1048
1049         /**
1050          * @return Boolean
1051          */
1052         public function isCurrent() {
1053                 return $this->mCurrent;
1054         }
1055
1056         /**
1057          * Get previous revision for this title
1058          *
1059          * @return Revision or null
1060          */
1061         public function getPrevious() {
1062                 if( $this->getTitle() ) {
1063                         $prev = $this->getTitle()->getPreviousRevisionID( $this->getId() );
1064                         if( $prev ) {
1065                                 return self::newFromTitle( $this->getTitle(), $prev );
1066                         }
1067                 }
1068                 return null;
1069         }
1070
1071         /**
1072          * Get next revision for this title
1073          *
1074          * @return Revision or null
1075          */
1076         public function getNext() {
1077                 if( $this->getTitle() ) {
1078                         $next = $this->getTitle()->getNextRevisionID( $this->getId() );
1079                         if ( $next ) {
1080                                 return self::newFromTitle( $this->getTitle(), $next );
1081                         }
1082                 }
1083                 return null;
1084         }
1085
1086         /**
1087          * Get previous revision Id for this page_id
1088          * This is used to populate rev_parent_id on save
1089          *
1090          * @param $db DatabaseBase
1091          * @return Integer
1092          */
1093         private function getPreviousRevisionId( $db ) {
1094                 if( is_null( $this->mPage ) ) {
1095                         return 0;
1096                 }
1097                 # Use page_latest if ID is not given
1098                 if( !$this->mId ) {
1099                         $prevId = $db->selectField( 'page', 'page_latest',
1100                                 array( 'page_id' => $this->mPage ),
1101                                 __METHOD__ );
1102                 } else {
1103                         $prevId = $db->selectField( 'revision', 'rev_id',
1104                                 array( 'rev_page' => $this->mPage, 'rev_id < ' . $this->mId ),
1105                                 __METHOD__,
1106                                 array( 'ORDER BY' => 'rev_id DESC' ) );
1107                 }
1108                 return intval( $prevId );
1109         }
1110
1111         /**
1112           * Get revision text associated with an old or archive row
1113           * $row is usually an object from wfFetchRow(), both the flags and the text
1114           * field must be included
1115           *
1116           * @param $row Object: the text data
1117           * @param $prefix String: table prefix (default 'old_')
1118           * @return String: text the text requested or false on failure
1119           */
1120         public static function getRevisionText( $row, $prefix = 'old_' ) {
1121                 wfProfileIn( __METHOD__ );
1122
1123                 # Get data
1124                 $textField = $prefix . 'text';
1125                 $flagsField = $prefix . 'flags';
1126
1127                 if( isset( $row->$flagsField ) ) {
1128                         $flags = explode( ',', $row->$flagsField );
1129                 } else {
1130                         $flags = array();
1131                 }
1132
1133                 if( isset( $row->$textField ) ) {
1134                         $text = $row->$textField;
1135                 } else {
1136                         wfProfileOut( __METHOD__ );
1137                         return false;
1138                 }
1139
1140                 # Use external methods for external objects, text in table is URL-only then
1141                 if ( in_array( 'external', $flags ) ) {
1142                         $url = $text;
1143                         $parts = explode( '://', $url, 2 );
1144                         if( count( $parts ) == 1 || $parts[1] == '' ) {
1145                                 wfProfileOut( __METHOD__ );
1146                                 return false;
1147                         }
1148                         $text = ExternalStore::fetchFromURL( $url );
1149                 }
1150
1151                 // If the text was fetched without an error, convert it
1152                 if ( $text !== false ) {
1153                         if( in_array( 'gzip', $flags ) ) {
1154                                 # Deal with optional compression of archived pages.
1155                                 # This can be done periodically via maintenance/compressOld.php, and
1156                                 # as pages are saved if $wgCompressRevisions is set.
1157                                 $text = gzinflate( $text );
1158                         }
1159
1160                         if( in_array( 'object', $flags ) ) {
1161                                 # Generic compressed storage
1162                                 $obj = unserialize( $text );
1163                                 if ( !is_object( $obj ) ) {
1164                                         // Invalid object
1165                                         wfProfileOut( __METHOD__ );
1166                                         return false;
1167                                 }
1168                                 $text = $obj->getText();
1169                         }
1170
1171                         global $wgLegacyEncoding;
1172                         if( $text !== false && $wgLegacyEncoding
1173                                 && !in_array( 'utf-8', $flags ) && !in_array( 'utf8', $flags ) )
1174                         {
1175                                 # Old revisions kept around in a legacy encoding?
1176                                 # Upconvert on demand.
1177                                 # ("utf8" checked for compatibility with some broken
1178                                 #  conversion scripts 2008-12-30)
1179                                 global $wgContLang;
1180                                 $text = $wgContLang->iconv( $wgLegacyEncoding, 'UTF-8', $text );
1181                         }
1182                 }
1183                 wfProfileOut( __METHOD__ );
1184                 return $text;
1185         }
1186
1187         /**
1188          * If $wgCompressRevisions is enabled, we will compress data.
1189          * The input string is modified in place.
1190          * Return value is the flags field: contains 'gzip' if the
1191          * data is compressed, and 'utf-8' if we're saving in UTF-8
1192          * mode.
1193          *
1194          * @param $text Mixed: reference to a text
1195          * @return String
1196          */
1197         public static function compressRevisionText( &$text ) {
1198                 global $wgCompressRevisions;
1199                 $flags = array();
1200
1201                 # Revisions not marked this way will be converted
1202                 # on load if $wgLegacyCharset is set in the future.
1203                 $flags[] = 'utf-8';
1204
1205                 if( $wgCompressRevisions ) {
1206                         if( function_exists( 'gzdeflate' ) ) {
1207                                 $text = gzdeflate( $text );
1208                                 $flags[] = 'gzip';
1209                         } else {
1210                                 wfDebug( __METHOD__ . " -- no zlib support, not compressing\n" );
1211                         }
1212                 }
1213                 return implode( ',', $flags );
1214         }
1215
1216         /**
1217          * Insert a new revision into the database, returning the new revision ID
1218          * number on success and dies horribly on failure.
1219          *
1220          * @param $dbw DatabaseBase: (master connection)
1221          * @throws MWException
1222          * @return Integer
1223          */
1224         public function insertOn( $dbw ) {
1225                 global $wgDefaultExternalStore, $wgContentHandlerUseDB;
1226
1227                 wfProfileIn( __METHOD__ );
1228
1229                 $this->checkContentModel();
1230
1231                 $data = $this->mText;
1232                 $flags = self::compressRevisionText( $data );
1233
1234                 # Write to external storage if required
1235                 if( $wgDefaultExternalStore ) {
1236                         // Store and get the URL
1237                         $data = ExternalStore::insertToDefault( $data );
1238                         if( !$data ) {
1239                                 throw new MWException( "Unable to store text to external storage" );
1240                         }
1241                         if( $flags ) {
1242                                 $flags .= ',';
1243                         }
1244                         $flags .= 'external';
1245                 }
1246
1247                 # Record the text (or external storage URL) to the text table
1248                 if( !isset( $this->mTextId ) ) {
1249                         $old_id = $dbw->nextSequenceValue( 'text_old_id_seq' );
1250                         $dbw->insert( 'text',
1251                                 array(
1252                                         'old_id'    => $old_id,
1253                                         'old_text'  => $data,
1254                                         'old_flags' => $flags,
1255                                 ), __METHOD__
1256                         );
1257                         $this->mTextId = $dbw->insertId();
1258                 }
1259
1260                 if ( $this->mComment === null ) $this->mComment = "";
1261
1262                 # Record the edit in revisions
1263                 $rev_id = isset( $this->mId )
1264                         ? $this->mId
1265                         : $dbw->nextSequenceValue( 'revision_rev_id_seq' );
1266                 $row = array(
1267                         'rev_id'         => $rev_id,
1268                         'rev_page'       => $this->mPage,
1269                         'rev_text_id'    => $this->mTextId,
1270                         'rev_comment'    => $this->mComment,
1271                         'rev_minor_edit' => $this->mMinorEdit ? 1 : 0,
1272                         'rev_user'       => $this->mUser,
1273                         'rev_user_text'  => $this->mUserText,
1274                         'rev_timestamp'  => $dbw->timestamp( $this->mTimestamp ),
1275                         'rev_deleted'    => $this->mDeleted,
1276                         'rev_len'        => $this->mSize,
1277                         'rev_parent_id'  => is_null( $this->mParentId )
1278                                 ? $this->getPreviousRevisionId( $dbw )
1279                                 : $this->mParentId,
1280                         'rev_sha1'       => is_null( $this->mSha1 )
1281                                 ? Revision::base36Sha1( $this->mText )
1282                                 : $this->mSha1,
1283                 );
1284
1285                 if ( $wgContentHandlerUseDB ) {
1286                         //NOTE: Store null for the default model and format, to save space.
1287                         //XXX: Makes the DB sensitive to changed defaults. Make this behaviour optional? Only in miser mode?
1288
1289                         $model = $this->getContentModel();
1290                         $format = $this->getContentFormat();
1291
1292                         $title = $this->getTitle();
1293
1294                         if ( $title === null ) {
1295                                 throw new MWException( "Insufficient information to determine the title of the revision's page!" );
1296                         }
1297
1298                         $defaultModel = ContentHandler::getDefaultModelFor( $title );
1299                         $defaultFormat = ContentHandler::getForModelID( $defaultModel )->getDefaultFormat();
1300
1301                         $row[ 'rev_content_model' ] = ( $model === $defaultModel ) ? null : $model;
1302                         $row[ 'rev_content_format' ] = ( $format === $defaultFormat ) ? null : $format;
1303                 }
1304
1305                 $dbw->insert( 'revision', $row, __METHOD__ );
1306
1307                 $this->mId = !is_null( $rev_id ) ? $rev_id : $dbw->insertId();
1308
1309                 wfRunHooks( 'RevisionInsertComplete', array( &$this, $data, $flags ) );
1310
1311                 wfProfileOut( __METHOD__ );
1312                 return $this->mId;
1313         }
1314
1315         protected function checkContentModel() {
1316                 global $wgContentHandlerUseDB;
1317
1318                 $title = $this->getTitle(); //note: may return null for revisions that have not yet been inserted.
1319
1320                 $model = $this->getContentModel();
1321                 $format = $this->getContentFormat();
1322                 $handler = $this->getContentHandler();
1323
1324                 if ( !$handler->isSupportedFormat( $format ) ) {
1325                         $t = $title->getPrefixedDBkey();
1326
1327                         throw new MWException( "Can't use format $format with content model $model on $t" );
1328                 }
1329
1330                 if ( !$wgContentHandlerUseDB && $title ) {
1331                         // if $wgContentHandlerUseDB is not set, all revisions must use the default content model and format.
1332
1333                         $defaultModel = ContentHandler::getDefaultModelFor( $title );
1334                         $defaultHandler = ContentHandler::getForModelID( $defaultModel );
1335                         $defaultFormat = $defaultHandler->getDefaultFormat();
1336
1337                         if ( $this->getContentModel() != $defaultModel ) {
1338                                 $t = $title->getPrefixedDBkey();
1339
1340                                 throw new MWException( "Can't save non-default content model with \$wgContentHandlerUseDB disabled: "
1341                                                                                 . "model is $model , default for $t is $defaultModel" );
1342                         }
1343
1344                         if ( $this->getContentFormat() != $defaultFormat ) {
1345                                 $t = $title->getPrefixedDBkey();
1346
1347                                 throw new MWException( "Can't use non-default content format with \$wgContentHandlerUseDB disabled: "
1348                                                                                 . "format is $format, default for $t is $defaultFormat" );
1349                         }
1350                 }
1351
1352                 $content = $this->getContent( Revision::RAW );
1353
1354                 if ( !$content->isValid() ) {
1355                         $t = $title->getPrefixedDBkey();
1356
1357                         throw new MWException( "Content of $t is not valid! Content model is $model" );
1358                 }
1359         }
1360
1361         /**
1362          * Get the base 36 SHA-1 value for a string of text
1363          * @param $text String
1364          * @return String
1365          */
1366         public static function base36Sha1( $text ) {
1367                 return wfBaseConvert( sha1( $text ), 16, 36, 31 );
1368         }
1369
1370         /**
1371          * Lazy-load the revision's text.
1372          * Currently hardcoded to the 'text' table storage engine.
1373          *
1374          * @return String
1375          */
1376         protected function loadText() {
1377                 wfProfileIn( __METHOD__ );
1378
1379                 // Caching may be beneficial for massive use of external storage
1380                 global $wgRevisionCacheExpiry, $wgMemc;
1381                 $textId = $this->getTextId();
1382                 $key = wfMemcKey( 'revisiontext', 'textid', $textId );
1383                 if( $wgRevisionCacheExpiry ) {
1384                         $text = $wgMemc->get( $key );
1385                         if( is_string( $text ) ) {
1386                                 wfDebug( __METHOD__ . ": got id $textId from cache\n" );
1387                                 wfProfileOut( __METHOD__ );
1388                                 return $text;
1389                         }
1390                 }
1391
1392                 // If we kept data for lazy extraction, use it now...
1393                 if ( isset( $this->mTextRow ) ) {
1394                         $row = $this->mTextRow;
1395                         $this->mTextRow = null;
1396                 } else {
1397                         $row = null;
1398                 }
1399
1400                 if( !$row ) {
1401                         // Text data is immutable; check slaves first.
1402                         $dbr = wfGetDB( DB_SLAVE );
1403                         $row = $dbr->selectRow( 'text',
1404                                 array( 'old_text', 'old_flags' ),
1405                                 array( 'old_id' => $this->getTextId() ),
1406                                 __METHOD__ );
1407                 }
1408
1409                 if( !$row && wfGetLB()->getServerCount() > 1 ) {
1410                         // Possible slave lag!
1411                         $dbw = wfGetDB( DB_MASTER );
1412                         $row = $dbw->selectRow( 'text',
1413                                 array( 'old_text', 'old_flags' ),
1414                                 array( 'old_id' => $this->getTextId() ),
1415                                 __METHOD__ );
1416                 }
1417
1418                 $text = self::getRevisionText( $row );
1419
1420                 # No negative caching -- negative hits on text rows may be due to corrupted slave servers
1421                 if( $wgRevisionCacheExpiry && $text !== false ) {
1422                         $wgMemc->set( $key, $text, $wgRevisionCacheExpiry );
1423                 }
1424
1425                 wfProfileOut( __METHOD__ );
1426
1427                 return $text;
1428         }
1429
1430         /**
1431          * Create a new null-revision for insertion into a page's
1432          * history. This will not re-save the text, but simply refer
1433          * to the text from the previous version.
1434          *
1435          * Such revisions can for instance identify page rename
1436          * operations and other such meta-modifications.
1437          *
1438          * @param $dbw DatabaseBase
1439          * @param $pageId Integer: ID number of the page to read from
1440          * @param $summary String: revision's summary
1441          * @param $minor Boolean: whether the revision should be considered as minor
1442          * @return Revision|null on error
1443          */
1444         public static function newNullRevision( $dbw, $pageId, $summary, $minor ) {
1445                 global $wgContentHandlerUseDB;
1446
1447                 wfProfileIn( __METHOD__ );
1448
1449                 $fields = array( 'page_latest', 'page_namespace', 'page_title',
1450                                                 'rev_text_id', 'rev_len', 'rev_sha1' );
1451
1452                 if ( $wgContentHandlerUseDB ) {
1453                         $fields[] = 'rev_content_model';
1454                         $fields[] = 'rev_content_format';
1455                 }
1456
1457                 $current = $dbw->selectRow(
1458                         array( 'page', 'revision' ),
1459                         $fields,
1460                         array(
1461                                 'page_id' => $pageId,
1462                                 'page_latest=rev_id',
1463                                 ),
1464                         __METHOD__ );
1465
1466                 if( $current ) {
1467                         $row = array(
1468                                 'page'       => $pageId,
1469                                 'comment'    => $summary,
1470                                 'minor_edit' => $minor,
1471                                 'text_id'    => $current->rev_text_id,
1472                                 'parent_id'  => $current->page_latest,
1473                                 'len'        => $current->rev_len,
1474                                 'sha1'       => $current->rev_sha1
1475                         );
1476
1477                         if ( $wgContentHandlerUseDB ) {
1478                                 $row[ 'content_model' ] = $current->rev_content_model;
1479                                 $row[ 'content_format' ] = $current->rev_content_format;
1480                         }
1481
1482                         $revision = new Revision( $row );
1483                         $revision->setTitle( Title::makeTitle( $current->page_namespace, $current->page_title ) );
1484                 } else {
1485                         $revision = null;
1486                 }
1487
1488                 wfProfileOut( __METHOD__ );
1489                 return $revision;
1490         }
1491
1492         /**
1493          * Determine if the current user is allowed to view a particular
1494          * field of this revision, if it's marked as deleted.
1495          *
1496          * @param $field Integer:one of self::DELETED_TEXT,
1497          *                              self::DELETED_COMMENT,
1498          *                              self::DELETED_USER
1499          * @param $user User object to check, or null to use $wgUser
1500          * @return Boolean
1501          */
1502         public function userCan( $field, User $user = null ) {
1503                 return self::userCanBitfield( $this->mDeleted, $field, $user );
1504         }
1505
1506         /**
1507          * Determine if the current user is allowed to view a particular
1508          * field of this revision, if it's marked as deleted. This is used
1509          * by various classes to avoid duplication.
1510          *
1511          * @param $bitfield Integer: current field
1512          * @param $field Integer: one of self::DELETED_TEXT = File::DELETED_FILE,
1513          *                               self::DELETED_COMMENT = File::DELETED_COMMENT,
1514          *                               self::DELETED_USER = File::DELETED_USER
1515          * @param $user User object to check, or null to use $wgUser
1516          * @return Boolean
1517          */
1518         public static function userCanBitfield( $bitfield, $field, User $user = null ) {
1519                 if( $bitfield & $field ) { // aspect is deleted
1520                         if ( $bitfield & self::DELETED_RESTRICTED ) {
1521                                 $permission = 'suppressrevision';
1522                         } elseif ( $field & self::DELETED_TEXT ) {
1523                                 $permission = 'deletedtext';
1524                         } else {
1525                                 $permission = 'deletedhistory';
1526                         }
1527                         wfDebug( "Checking for $permission due to $field match on $bitfield\n" );
1528                         if ( $user === null ) {
1529                                 global $wgUser;
1530                                 $user = $wgUser;
1531                         }
1532                         return $user->isAllowed( $permission );
1533                 } else {
1534                         return true;
1535                 }
1536         }
1537
1538         /**
1539          * Get rev_timestamp from rev_id, without loading the rest of the row
1540          *
1541          * @param $title Title
1542          * @param $id Integer
1543          * @return String
1544          */
1545         static function getTimestampFromId( $title, $id ) {
1546                 $dbr = wfGetDB( DB_SLAVE );
1547                 // Casting fix for DB2
1548                 if ( $id == '' ) {
1549                         $id = 0;
1550                 }
1551                 $conds = array( 'rev_id' => $id );
1552                 $conds['rev_page'] = $title->getArticleID();
1553                 $timestamp = $dbr->selectField( 'revision', 'rev_timestamp', $conds, __METHOD__ );
1554                 if ( $timestamp === false && wfGetLB()->getServerCount() > 1 ) {
1555                         # Not in slave, try master
1556                         $dbw = wfGetDB( DB_MASTER );
1557                         $timestamp = $dbw->selectField( 'revision', 'rev_timestamp', $conds, __METHOD__ );
1558                 }
1559                 return wfTimestamp( TS_MW, $timestamp );
1560         }
1561
1562         /**
1563          * Get count of revisions per page...not very efficient
1564          *
1565          * @param $db DatabaseBase
1566          * @param $id Integer: page id
1567          * @return Integer
1568          */
1569         static function countByPageId( $db, $id ) {
1570                 $row = $db->selectRow( 'revision', array( 'revCount' => 'COUNT(*)' ),
1571                         array( 'rev_page' => $id ), __METHOD__ );
1572                 if( $row ) {
1573                         return $row->revCount;
1574                 }
1575                 return 0;
1576         }
1577
1578         /**
1579          * Get count of revisions per page...not very efficient
1580          *
1581          * @param $db DatabaseBase
1582          * @param $title Title
1583          * @return Integer
1584          */
1585         static function countByTitle( $db, $title ) {
1586                 $id = $title->getArticleID();
1587                 if( $id ) {
1588                         return self::countByPageId( $db, $id );
1589                 }
1590                 return 0;
1591         }
1592
1593         /**
1594          * Check if no edits were made by other users since
1595          * the time a user started editing the page. Limit to
1596          * 50 revisions for the sake of performance.
1597          *
1598          * @since 1.20
1599          *
1600          * @param DatabaseBase|int $db the Database to perform the check on. May be given as a Database object or
1601          *        a database identifier usable with wfGetDB.
1602          * @param int $pageId the ID of the page in question
1603          * @param int $userId the ID of the user in question
1604          * @param string $since look at edits since this time
1605          *
1606          * @return bool True if the given user was the only one to edit since the given timestamp
1607          */
1608         public static function userWasLastToEdit( $db, $pageId, $userId, $since ) {
1609                 if ( !$userId ) return false;
1610
1611                 if ( is_int( $db ) ) {
1612                         $db = wfGetDB( $db );
1613                 }
1614
1615                 $res = $db->select( 'revision',
1616                         'rev_user',
1617                         array(
1618                                 'rev_page' => $pageId,
1619                                 'rev_timestamp > ' . $db->addQuotes( $db->timestamp( $since ) )
1620                         ),
1621                         __METHOD__,
1622                         array( 'ORDER BY' => 'rev_timestamp ASC', 'LIMIT' => 50 ) );
1623                 foreach ( $res as $row ) {
1624                         if ( $row->rev_user != $userId ) {
1625                                 return false;
1626                         }
1627                 }
1628                 return true;
1629         }
1630 }