updated to MediaWiki 1.14.0

1 files changed, 2120 insertions, 0 deletions

diff --git a/includes/diff/DifferenceEngine.php b/includes/diff/DifferenceEngine.php
new file mode 100644
index 00000000..b30ff190
--- /dev/null
+++ b/includes/diff/DifferenceEngine.php
@@ -0,0 +1,2120 @@
+<?php
+/**
+ * @defgroup DifferenceEngine DifferenceEngine
+ */
+
+/**
+ * Constant to indicate diff cache compatibility.
+ * Bump this when changing the diff formatting in a way that
+ * fixes important bugs or such to force cached diff views to
+ * clear.
+ */
+define( 'MW_DIFF_VERSION', '1.11a' );
+
+/**
+ * @todo document
+ * @ingroup DifferenceEngine
+ */
+class DifferenceEngine {
+	/**#@+
+	 * @private
+	 */
+	var $mOldid, $mNewid, $mTitle;
+	var $mOldtitle, $mNewtitle, $mPagetitle;
+	var $mOldtext, $mNewtext;
+	var $mOldPage, $mNewPage;
+	var $mRcidMarkPatrolled;
+	var $mOldRev, $mNewRev;
+	var $mRevisionsLoaded = false; // Have the revisions been loaded
+	var $mTextLoaded = 0; // How many text blobs have been loaded, 0, 1 or 2?
+	var $htmldiff;
+	/**#@-*/
+
+	/**
+	 * Constructor
+	 * @param $titleObj Title object that the diff is associated with
+	 * @param $old Integer: old ID we want to show and diff with.
+	 * @param $new String: either 'prev' or 'next'.
+	 * @param $rcid Integer: ??? FIXME (default 0)
+	 * @param $refreshCache boolean If set, refreshes the diff cache
+	 * @param $htmldiff boolean If set, output using HTMLDiff instead of raw wikicode diff
+	 */
+	function __construct( $titleObj = null, $old = 0, $new = 0, $rcid = 0, $refreshCache = false , $htmldiff = false) {
+		$this->mTitle = $titleObj;
+		wfDebug("DifferenceEngine old '$old' new '$new' rcid '$rcid'\n");
+
+		if ( 'prev' === $new ) {
+			# Show diff between revision $old and the previous one.
+			# Get previous one from DB.
+			#
+			$this->mNewid = intval($old);
+
+			$this->mOldid = $this->mTitle->getPreviousRevisionID( $this->mNewid );
+
+		} elseif ( 'next' === $new ) {
+			# Show diff between revision $old and the previous one.
+			# Get previous one from DB.
+			#
+			$this->mOldid = intval($old);
+			$this->mNewid = $this->mTitle->getNextRevisionID( $this->mOldid );
+			if ( false === $this->mNewid ) {
+				# if no result, NewId points to the newest old revision. The only newer
+				# revision is cur, which is "0".
+				$this->mNewid = 0;
+			}
+
+		} else {
+			$this->mOldid = intval($old);
+			$this->mNewid = intval($new);
+		}
+		$this->mRcidMarkPatrolled = intval($rcid);  # force it to be an integer
+		$this->mRefreshCache = $refreshCache;
+		$this->htmldiff = $htmldiff;
+	}
+
+	function getTitle() {
+		return $this->mTitle;
+	}
+
+	function showDiffPage( $diffOnly = false ) {
+		global $wgUser, $wgOut, $wgUseExternalEditor, $wgUseRCPatrol, $wgEnableHtmlDiff;
+		wfProfileIn( __METHOD__ );
+
+
+		# If external diffs are enabled both globally and for the user,
+		# we'll use the application/x-external-editor interface to call
+		# an external diff tool like kompare, kdiff3, etc.
+		if($wgUseExternalEditor && $wgUser->getOption('externaldiff')) {
+			global $wgInputEncoding,$wgServer,$wgScript,$wgLang;
+			$wgOut->disable();
+			header ( "Content-type: application/x-external-editor; charset=".$wgInputEncoding );
+			$url1=$this->mTitle->getFullURL("action=raw&oldid=".$this->mOldid);
+			$url2=$this->mTitle->getFullURL("action=raw&oldid=".$this->mNewid);
+			$special=$wgLang->getNsText(NS_SPECIAL);
+			$control=<<<CONTROL
+			[Process]
+			Type=Diff text
+			Engine=MediaWiki
+			Script={$wgServer}{$wgScript}
+			Special namespace={$special}
+
+			[File]
+			Extension=wiki
+			URL=$url1
+
+			[File 2]
+			Extension=wiki
+			URL=$url2
+CONTROL;
+			echo($control);
+			return;
+		}
+
+		$wgOut->setArticleFlag( false );
+		if ( ! $this->loadRevisionData() ) {
+			$t = $this->mTitle->getPrefixedText();
+			$d = wfMsgExt( 'missingarticle-diff', array( 'escape' ), $this->mOldid, $this->mNewid );
+			$wgOut->setPagetitle( wfMsg( 'errorpagetitle' ) );
+			$wgOut->addWikiMsg( 'missing-article', "<nowiki>$t</nowiki>", $d );
+			wfProfileOut( __METHOD__ );
+			return;
+		}
+
+		wfRunHooks( 'DiffViewHeader', array( $this, $this->mOldRev, $this->mNewRev ) );
+
+		if ( $this->mNewRev->isCurrent() ) {
+			$wgOut->setArticleFlag( true );
+		}
+
+		# mOldid is false if the difference engine is called with a "vague" query for
+		# a diff between a version V and its previous version V' AND the version V
+		# is the first version of that article. In that case, V' does not exist.
+		if ( $this->mOldid === false ) {
+			$this->showFirstRevision();
+			$this->renderNewRevision();  // should we respect $diffOnly here or not?
+			wfProfileOut( __METHOD__ );
+			return;
+		}
+
+		$wgOut->suppressQuickbar();
+
+		$oldTitle = $this->mOldPage->getPrefixedText();
+		$newTitle = $this->mNewPage->getPrefixedText();
+		if( $oldTitle == $newTitle ) {
+			$wgOut->setPageTitle( $newTitle );
+		} else {
+			$wgOut->setPageTitle( $oldTitle . ', ' . $newTitle );
+		}
+		$wgOut->setSubtitle( wfMsgExt( 'difference', array( 'parseinline' ) ) );
+		$wgOut->setRobotPolicy( 'noindex,nofollow' );
+
+		if ( !$this->mOldPage->userCanRead() || !$this->mNewPage->userCanRead() ) {
+			$wgOut->loginToUse();
+			$wgOut->output();
+			$wgOut->disable();
+			wfProfileOut( __METHOD__ );
+			return;
+		}
+
+		$sk = $wgUser->getSkin();
+
+		// Check if page is editable
+		$editable = $this->mNewRev->getTitle()->userCan( 'edit' );
+		if ( $editable && $this->mNewRev->isCurrent() && $wgUser->isAllowed( 'rollback' ) ) {
+			$rollback = '&nbsp;&nbsp;&nbsp;' . $sk->generateRollback( $this->mNewRev );
+		} else {
+			$rollback = '';
+		}
+
+		// Prepare a change patrol link, if applicable
+		if( $wgUseRCPatrol && $this->mTitle->userCan('patrol') ) {
+			// If we've been given an explicit change identifier, use it; saves time
+			if( $this->mRcidMarkPatrolled ) {
+				$rcid = $this->mRcidMarkPatrolled;
+			} else {
+				// Look for an unpatrolled change corresponding to this diff
+				$db = wfGetDB( DB_SLAVE );
+				$change = RecentChange::newFromConds(
+				array(
+				// Add redundant user,timestamp condition so we can use the existing index
+						'rc_user_text'  => $this->mNewRev->getUserText( Revision::FOR_THIS_USER ),
+						'rc_timestamp'  => $db->timestamp( $this->mNewRev->getTimestamp() ),
+						'rc_this_oldid' => $this->mNewid,
+						'rc_last_oldid' => $this->mOldid,
+						'rc_patrolled'  => 0
+				),
+				__METHOD__
+				);
+				if( $change instanceof RecentChange ) {
+					$rcid = $change->mAttribs['rc_id'];
+				} else {
+					// None found
+					$rcid = 0;
+				}
+			}
+			// Build the link
+			if( $rcid ) {
+				$patrol = ' <span class="patrollink">[' . $sk->makeKnownLinkObj(
+					$this->mTitle,
+					wfMsgHtml( 'markaspatrolleddiff' ),
+						"action=markpatrolled&rcid={$rcid}"
+					) . ']</span>';
+			} else {
+				$patrol = '';
+			}
+		} else {
+			$patrol = '';
+		}
+
+		$htmldiffarg = $this->htmlDiffArgument();
+		$prevlink = $sk->makeKnownLinkObj( $this->mTitle, wfMsgHtml( 'previousdiff' ),
+			'diff=prev&oldid='.$this->mOldid.$htmldiffarg, '', '', 'id="differences-prevlink"' );
+		if ( $this->mNewRev->isCurrent() ) {
+			$nextlink = '&nbsp;';
+		} else {
+			$nextlink = $sk->makeKnownLinkObj( $this->mTitle, wfMsgHtml( 'nextdiff' ),
+				'diff=next&oldid='.$this->mNewid.$htmldiffarg, '', '', 'id="differences-nextlink"' );
+		}
+
+		$oldminor = '';
+		$newminor = '';
+
+		if ($this->mOldRev->mMinorEdit == 1) {
+			$oldminor = Xml::span( wfMsg( 'minoreditletter' ), 'minor' ) . ' ';
+		}
+
+		if ($this->mNewRev->mMinorEdit == 1) {
+			$newminor = Xml::span( wfMsg( 'minoreditletter' ), 'minor' ) . ' ';
+		}
+
+		$rdel = ''; $ldel = '';
+		if( $wgUser->isAllowed( 'deleterevision' ) ) {
+			$revdel = SpecialPage::getTitleFor( 'Revisiondelete' );
+			if( !$this->mOldRev->userCan( Revision::DELETED_RESTRICTED ) ) {
+				// If revision was hidden from sysops
+				$ldel = wfMsgHtml( 'rev-delundel' );
+			} else {
+				$ldel = $sk->makeKnownLinkObj( $revdel,
+				wfMsgHtml( 'rev-delundel' ),
+					'target=' . urlencode( $this->mOldRev->mTitle->getPrefixedDbkey() ) .
+					'&oldid=' . urlencode( $this->mOldRev->getId() ) );
+				// Bolden oversighted content
+				if( $this->mOldRev->isDeleted( Revision::DELETED_RESTRICTED ) )
+				$ldel = "<strong>$ldel</strong>";
+			}
+			$ldel = "&nbsp;&nbsp;&nbsp;<tt>(<small>$ldel</small>)</tt> ";
+			// We don't currently handle well changing the top revision's settings
+			if( $this->mNewRev->isCurrent() ) {
+				// If revision was hidden from sysops
+				$rdel = wfMsgHtml( 'rev-delundel' );
+			} else if( !$this->mNewRev->userCan( Revision::DELETED_RESTRICTED ) ) {
+				// If revision was hidden from sysops
+				$rdel = wfMsgHtml( 'rev-delundel' );
+			} else {
+				$rdel = $sk->makeKnownLinkObj( $revdel,
+				wfMsgHtml( 'rev-delundel' ),
+					'target=' . urlencode( $this->mNewRev->mTitle->getPrefixedDbkey() ) .
+					'&oldid=' . urlencode( $this->mNewRev->getId() ) );
+				// Bolden oversighted content
+				if( $this->mNewRev->isDeleted( Revision::DELETED_RESTRICTED ) )
+				$rdel = "<strong>$rdel</strong>";
+			}
+			$rdel = "&nbsp;&nbsp;&nbsp;<tt>(<small>$rdel</small>)</tt> ";
+		}
+
+		$oldHeader = '<div id="mw-diff-otitle1"><strong>'.$this->mOldtitle.'</strong></div>' .
+			'<div id="mw-diff-otitle2">' . $sk->revUserTools( $this->mOldRev, true ) . "</div>" .
+			'<div id="mw-diff-otitle3">' . $oldminor . $sk->revComment( $this->mOldRev, !$diffOnly, true ) . $ldel . "</div>" .
+			'<div id="mw-diff-otitle4">' . $prevlink .'</div>';
+		$newHeader = '<div id="mw-diff-ntitle1"><strong>'.$this->mNewtitle.'</strong></div>' .
+			'<div id="mw-diff-ntitle2">' . $sk->revUserTools( $this->mNewRev, true ) . " $rollback</div>" .
+			'<div id="mw-diff-ntitle3">' . $newminor . $sk->revComment( $this->mNewRev, !$diffOnly, true ) . $rdel . "</div>" .
+			'<div id="mw-diff-ntitle4">' . $nextlink . $patrol . '</div>';
+
+		if( $wgEnableHtmlDiff && $this->htmldiff) {
+			$multi = $this->getMultiNotice();
+			$wgOut->addHTML('<div class="diff-switchtype">'.$sk->makeKnownLinkObj( $this->mTitle, wfMsgHtml( 'wikicodecomparison' ),
+			'diff='.$this->mNewid.'&oldid='.$this->mOldid.'&htmldiff=0', '', '', 'id="differences-switchtype"' ).'</div>');
+			$wgOut->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
+			$this->renderHtmlDiff();
+		} else {
+			if($wgEnableHtmlDiff){
+				$wgOut->addHTML('<div class="diff-switchtype">'.$sk->makeKnownLinkObj( $this->mTitle, wfMsgHtml( 'visualcomparison' ),
+				'diff='.$this->mNewid.'&oldid='.$this->mOldid.'&htmldiff=1', '', '', 'id="differences-switchtype"' ).'</div>');
+			}
+			$this->showDiff( $oldHeader, $newHeader );
+			if( !$diffOnly ) {
+				$this->renderNewRevision();
+			}
+		}
+		wfProfileOut( __METHOD__ );
+	}
+
+	/**
+	 * Show the new revision of the page.
+	 */
+	function renderNewRevision() {
+		global $wgOut;
+		wfProfileIn( __METHOD__ );
+
+		$wgOut->addHTML( "<hr /><h2>{$this->mPagetitle}</h2>\n" );
+		#add deleted rev tag if needed
+		if( !$this->mNewRev->userCan(Revision::DELETED_TEXT) ) {
+			$wgOut->addWikiMsg( 'rev-deleted-text-permission' );
+		} else if( $this->mNewRev->isDeleted(Revision::DELETED_TEXT) ) {
+			$wgOut->addWikiMsg( 'rev-deleted-text-view' );
+		}
+
+		if( !$this->mNewRev->isCurrent() ) {
+			$oldEditSectionSetting = $wgOut->parserOptions()->setEditSection( false );
+		}
+
+		$this->loadNewText();
+		if( is_object( $this->mNewRev ) ) {
+			$wgOut->setRevisionId( $this->mNewRev->getId() );
+		}
+
+		if ($this->mTitle->isCssJsSubpage() || $this->mTitle->isCssOrJsPage()) {
+			// Stolen from Article::view --AG 2007-10-11
+
+			// Give hooks a chance to customise the output
+			if( wfRunHooks( 'ShowRawCssJs', array( $this->mNewtext, $this->mTitle, $wgOut ) ) ) {
+				// Wrap the whole lot in a <pre> and don't parse
+				$m = array();
+				preg_match( '!\.(css|js)$!u', $this->mTitle->getText(), $m );
+				$wgOut->addHTML( "<pre class=\"mw-code mw-{$m[1]}\" dir=\"ltr\">\n" );
+				$wgOut->addHTML( htmlspecialchars( $this->mNewtext ) );
+				$wgOut->addHTML( "\n</pre>\n" );
+			}
+		} else
+		$wgOut->addWikiTextTidy( $this->mNewtext );
+
+		if( !$this->mNewRev->isCurrent() ) {
+			$wgOut->parserOptions()->setEditSection( $oldEditSectionSetting );
+		}
+
+		wfProfileOut( __METHOD__ );
+	}
+
+
+	function renderHtmlDiff() {
+		global $wgOut, $wgTitle, $wgParser, $wgDebugComments;
+		wfProfileIn( __METHOD__ );
+
+		$this->showDiffStyle();
+
+		$wgOut->addHTML( '<h2>'.wfMsgHtml( 'visual-comparison' )."</h2>\n" );
+		#add deleted rev tag if needed
+		if( !$this->mNewRev->userCan(Revision::DELETED_TEXT) ) {
+			$wgOut->addWikiMsg( 'rev-deleted-text-permission' );
+		} else if( $this->mNewRev->isDeleted(Revision::DELETED_TEXT) ) {
+			$wgOut->addWikiMsg( 'rev-deleted-text-view' );
+		}
+
+		if( !$this->mNewRev->isCurrent() ) {
+			$oldEditSectionSetting = $wgOut->parserOptions()->setEditSection( false );
+		}
+
+		$this->loadText();
+
+		// Old revision
+		if( is_object( $this->mOldRev ) ) {
+			$wgOut->setRevisionId( $this->mOldRev->getId() );
+		}
+
+		$popts = $wgOut->parserOptions();
+		$oldTidy = $popts->setTidy( true );
+		$popts->setEditSection( false );
+
+		$parserOutput = $wgParser->parse( $this->mOldtext, $wgTitle, $popts, true, true, $wgOut->getRevisionId() );
+		$popts->setTidy( $oldTidy );
+
+		//only for new?
+		//$wgOut->addParserOutputNoText( $parserOutput );
+		$oldHtml = $parserOutput->getText();
+		wfRunHooks( 'OutputPageBeforeHTML', array( &$wgOut, &$oldHtml ) );
+
+		// New revision
+		if( is_object( $this->mNewRev ) ) {
+			$wgOut->setRevisionId( $this->mNewRev->getId() );
+		}
+
+		$popts = $wgOut->parserOptions();
+		$oldTidy = $popts->setTidy( true );
+
+		$parserOutput = $wgParser->parse( $this->mNewtext, $wgTitle, $popts, true, true, $wgOut->getRevisionId() );
+		$popts->setTidy( $oldTidy );
+
+		$wgOut->addParserOutputNoText( $parserOutput );
+		$newHtml = $parserOutput->getText();
+		wfRunHooks( 'OutputPageBeforeHTML', array( &$wgOut, &$newHtml ) );
+
+		unset($parserOutput, $popts);
+
+		$differ = new HTMLDiffer(new DelegatingContentHandler($wgOut));
+		$differ->htmlDiff($oldHtml, $newHtml);
+		if ( $wgDebugComments ) {
+			$wgOut->addHTML( "\n<!-- HtmlDiff Debug Output:\n" . HTMLDiffer::getDebugOutput() . " End Debug -->" );
+		}
+
+		wfProfileOut( __METHOD__ );
+	}
+
+	/**
+	 * Show the first revision of an article. Uses normal diff headers in
+	 * contrast to normal "old revision" display style.
+	 */
+	function showFirstRevision() {
+		global $wgOut, $wgUser;
+		wfProfileIn( __METHOD__ );
+
+		# Get article text from the DB
+		#
+		if ( ! $this->loadNewText() ) {
+			$t = $this->mTitle->getPrefixedText();
+			$d = wfMsgExt( 'missingarticle-diff', array( 'escape' ), $this->mOldid, $this->mNewid );
+			$wgOut->setPagetitle( wfMsg( 'errorpagetitle' ) );
+			$wgOut->addWikiMsg( 'missing-article', "<nowiki>$t</nowiki>", $d );
+			wfProfileOut( __METHOD__ );
+			return;
+		}
+		if ( $this->mNewRev->isCurrent() ) {
+			$wgOut->setArticleFlag( true );
+		}
+
+		# Check if user is allowed to look at this page. If not, bail out.
+		#
+		if ( !$this->mTitle->userCanRead() ) {
+			$wgOut->loginToUse();
+			$wgOut->output();
+			wfProfileOut( __METHOD__ );
+			throw new MWException("Permission Error: you do not have access to view this page");
+		}
+
+		# Prepare the header box
+		#
+		$sk = $wgUser->getSkin();
+
+		$nextlink = $sk->makeKnownLinkObj( $this->mTitle, wfMsgHtml( 'nextdiff' ), 'diff=next&oldid='.$this->mNewid.$this->htmlDiffArgument(), '', '', 'id="differences-nextlink"' );
+		$header = "<div class=\"firstrevisionheader\" style=\"text-align: center\"><strong>{$this->mOldtitle}</strong><br />" .
+		$sk->revUserTools( $this->mNewRev ) . "<br />" .
+		$sk->revComment( $this->mNewRev ) . "<br />" .
+		$nextlink . "</div>\n";
+
+		$wgOut->addHTML( $header );
+
+		$wgOut->setSubtitle( wfMsgExt( 'difference', array( 'parseinline' ) ) );
+		$wgOut->setRobotPolicy( 'noindex,nofollow' );
+
+		wfProfileOut( __METHOD__ );
+	}
+
+	function htmlDiffArgument(){
+		global $wgEnableHtmlDiff;
+		if($wgEnableHtmlDiff){
+			if($this->htmldiff){
+				return '&htmldiff=1';
+			}else{
+				return '&htmldiff=0';
+			}
+		}else{
+			return '';
+		}
+	}
+
+	/**
+	 * Get the diff text, send it to $wgOut
+	 * Returns false if the diff could not be generated, otherwise returns true
+	 */
+	function showDiff( $otitle, $ntitle ) {
+		global $wgOut;
+		$diff = $this->getDiff( $otitle, $ntitle );
+		if ( $diff === false ) {
+			$wgOut->addWikiMsg( 'missing-article', "<nowiki>(fixme, bug)</nowiki>", '' );
+			return false;
+		} else {
+			$this->showDiffStyle();
+			$wgOut->addHTML( $diff );
+			return true;
+		}
+	}
+
+	/**
+	 * Add style sheets and supporting JS for diff display.
+	 */
+	function showDiffStyle() {
+		global $wgStylePath, $wgStyleVersion, $wgOut;
+		$wgOut->addStyle( 'common/diff.css' );
+
+		// JS is needed to detect old versions of Mozilla to work around an annoyance bug.
+		$wgOut->addScript( "<script type=\"text/javascript\" src=\"$wgStylePath/common/diff.js?$wgStyleVersion\"></script>" );
+	}
+
+	/**
+	 * Get complete diff table, including header
+	 *
+	 * @param Title $otitle Old title
+	 * @param Title $ntitle New title
+	 * @return mixed
+	 */
+	function getDiff( $otitle, $ntitle ) {
+		$body = $this->getDiffBody();
+		if ( $body === false ) {
+			return false;
+		} else {
+			$multi = $this->getMultiNotice();
+			return $this->addHeader( $body, $otitle, $ntitle, $multi );
+		}
+	}
+
+	/**
+	 * Get the diff table body, without header
+	 *
+	 * @return mixed
+	 */
+	function getDiffBody() {
+		global $wgMemc;
+		wfProfileIn( __METHOD__ );
+		// Check if the diff should be hidden from this user
+		if ( $this->mOldRev && !$this->mOldRev->userCan(Revision::DELETED_TEXT) ) {
+			return '';
+		} else if ( $this->mNewRev && !$this->mNewRev->userCan(Revision::DELETED_TEXT) ) {
+			return '';
+		}
+		// Cacheable?
+		$key = false;
+		if ( $this->mOldid && $this->mNewid ) {
+			$key = wfMemcKey( 'diff', 'version', MW_DIFF_VERSION, 'oldid', $this->mOldid, 'newid', $this->mNewid );
+			// Try cache
+			if ( !$this->mRefreshCache ) {
+				$difftext = $wgMemc->get( $key );
+				if ( $difftext ) {
+					wfIncrStats( 'diff_cache_hit' );
+					$difftext = $this->localiseLineNumbers( $difftext );
+					$difftext .= "\n<!-- diff cache key $key -->\n";
+					wfProfileOut( __METHOD__ );
+					return $difftext;
+				}
+			} // don't try to load but save the result
+		}
+
+		// Loadtext is permission safe, this just clears out the diff
+		if ( !$this->loadText() ) {
+			wfProfileOut( __METHOD__ );
+			return false;
+		}
+
+		$difftext = $this->generateDiffBody( $this->mOldtext, $this->mNewtext );
+
+		// Save to cache for 7 days
+		if ( !wfRunHooks( 'AbortDiffCache', array( &$this ) ) ) {
+			wfIncrStats( 'diff_uncacheable' );
+		} else if ( $key !== false && $difftext !== false ) {
+			wfIncrStats( 'diff_cache_miss' );
+			$wgMemc->set( $key, $difftext, 7*86400 );
+		} else {
+			wfIncrStats( 'diff_uncacheable' );
+		}
+		// Replace line numbers with the text in the user's language
+		if ( $difftext !== false ) {
+			$difftext = $this->localiseLineNumbers( $difftext );
+		}
+		wfProfileOut( __METHOD__ );
+		return $difftext;
+	}
+
+	/**
+	 * Generate a diff, no caching
+	 * $otext and $ntext must be already segmented
+	 */
+	function generateDiffBody( $otext, $ntext ) {
+		global $wgExternalDiffEngine, $wgContLang;
+
+		$otext = str_replace( "\r\n", "\n", $otext );
+		$ntext = str_replace( "\r\n", "\n", $ntext );
+
+		if ( $wgExternalDiffEngine == 'wikidiff' ) {
+			# For historical reasons, external diff engine expects
+			# input text to be HTML-escaped already
+			$otext = htmlspecialchars ( $wgContLang->segmentForDiff( $otext ) );
+			$ntext = htmlspecialchars ( $wgContLang->segmentForDiff( $ntext ) );
+			if( !function_exists( 'wikidiff_do_diff' ) ) {
+				dl('php_wikidiff.so');
+			}
+			return $wgContLang->unsegementForDiff( wikidiff_do_diff( $otext, $ntext, 2 ) ) .
+			$this->debug( 'wikidiff1' );
+		}
+
+		if ( $wgExternalDiffEngine == 'wikidiff2' ) {
+			# Better external diff engine, the 2 may some day be dropped
+			# This one does the escaping and segmenting itself
+			if ( !function_exists( 'wikidiff2_do_diff' ) ) {
+				wfProfileIn( __METHOD__ . "-dl" );
+				@dl('php_wikidiff2.so');
+				wfProfileOut( __METHOD__ . "-dl" );
+			}
+			if ( function_exists( 'wikidiff2_do_diff' ) ) {
+				wfProfileIn( 'wikidiff2_do_diff' );
+				$text = wikidiff2_do_diff( $otext, $ntext, 2 );
+				$text .= $this->debug( 'wikidiff2' );
+				wfProfileOut( 'wikidiff2_do_diff' );
+				return $text;
+			}
+		}
+		if ( $wgExternalDiffEngine != 'wikidiff3' && $wgExternalDiffEngine !== false ) {
+			# Diff via the shell
+			global $wgTmpDirectory;
+			$tempName1 = tempnam( $wgTmpDirectory, 'diff_' );
+			$tempName2 = tempnam( $wgTmpDirectory, 'diff_' );
+
+			$tempFile1 = fopen( $tempName1, "w" );
+			if ( !$tempFile1 ) {
+				wfProfileOut( __METHOD__ );
+				return false;
+			}
+			$tempFile2 = fopen( $tempName2, "w" );
+			if ( !$tempFile2 ) {
+				wfProfileOut( __METHOD__ );
+				return false;
+			}
+			fwrite( $tempFile1, $otext );
+			fwrite( $tempFile2, $ntext );
+			fclose( $tempFile1 );
+			fclose( $tempFile2 );
+			$cmd = wfEscapeShellArg( $wgExternalDiffEngine, $tempName1, $tempName2 );
+			wfProfileIn( __METHOD__ . "-shellexec" );
+			$difftext = wfShellExec( $cmd );
+			$difftext .= $this->debug( "external $wgExternalDiffEngine" );
+			wfProfileOut( __METHOD__ . "-shellexec" );
+			unlink( $tempName1 );
+			unlink( $tempName2 );
+			return $difftext;
+		}
+
+		# Native PHP diff
+		$ota = explode( "\n", $wgContLang->segmentForDiff( $otext ) );
+		$nta = explode( "\n", $wgContLang->segmentForDiff( $ntext ) );
+		$diffs = new Diff( $ota, $nta );
+		$formatter = new TableDiffFormatter();
+		return $wgContLang->unsegmentForDiff( $formatter->format( $diffs ) ) .
+		$this->debug();
+	}
+
+	/**
+	 * Generate a debug comment indicating diff generating time,
+	 * server node, and generator backend.
+	 */
+	protected function debug( $generator="internal" ) {
+		global $wgShowHostnames;
+		$data = array( $generator );
+		if( $wgShowHostnames ) {
+			$data[] = wfHostname();
+		}
+		$data[] = wfTimestamp( TS_DB );
+		return "<!-- diff generator: " .
+		implode( " ",
+		array_map(
+					"htmlspecialchars",
+		$data ) ) .
+			" -->\n";
+	}
+
+	/**
+	 * Replace line numbers with the text in the user's language
+	 */
+	function localiseLineNumbers( $text ) {
+		return preg_replace_callback( '/<!--LINE (\d+)-->/',
+		array( &$this, 'localiseLineNumbersCb' ), $text );
+	}
+
+	function localiseLineNumbersCb( $matches ) {
+		global $wgLang;
+		return wfMsgExt( 'lineno', array( 'parseinline' ), $wgLang->formatNum( $matches[1] ) );
+	}
+
+
+	/**
+	 * If there are revisions between the ones being compared, return a note saying so.
+	 */
+	function getMultiNotice() {
+		if ( !is_object($this->mOldRev) || !is_object($this->mNewRev) )
+		return '';
+
+		if( !$this->mOldPage->equals( $this->mNewPage ) ) {
+			// Comparing two different pages? Count would be meaningless.
+			return '';
+		}
+
+		$oldid = $this->mOldRev->getId();
+		$newid = $this->mNewRev->getId();
+		if ( $oldid > $newid ) {
+			$tmp = $oldid; $oldid = $newid; $newid = $tmp;
+		}
+
+		$n = $this->mTitle->countRevisionsBetween( $oldid, $newid );
+		if ( !$n )
+		return '';
+
+		return wfMsgExt( 'diff-multi', array( 'parseinline' ), $n );
+	}
+
+
+	/**
+	 * Add the header to a diff body
+	 */
+	static function addHeader( $diff, $otitle, $ntitle, $multi = '' ) {
+		$header = "
+		<table class='diff'>
+		<col class='diff-marker' />
+		<col class='diff-content' />
+		<col class='diff-marker' />
+		<col class='diff-content' />
+		<tr valign='top'>
+		<td colspan='2' class='diff-otitle'>{$otitle}</td>
+		<td colspan='2' class='diff-ntitle'>{$ntitle}</td>
+		</tr>
+		";
+
+		if ( $multi != '' )
+		$header .= "<tr><td colspan='4' align='center' class='diff-multi'>{$multi}</td></tr>";
+
+		return $header . $diff . "</table>";
+	}
+
+	/**
+	 * Use specified text instead of loading from the database
+	 */
+	function setText( $oldText, $newText ) {
+		$this->mOldtext = $oldText;
+		$this->mNewtext = $newText;
+		$this->mTextLoaded = 2;
+	}
+
+	/**
+	 * Load revision metadata for the specified articles. If newid is 0, then compare
+	 * the old article in oldid to the current article; if oldid is 0, then
+	 * compare the current article to the immediately previous one (ignoring the
+	 * value of newid).
+	 *
+	 * If oldid is false, leave the corresponding revision object set
+	 * to false. This is impossible via ordinary user input, and is provided for
+	 * API convenience.
+	 */
+	function loadRevisionData() {
+		global $wgLang, $wgUser;
+		if ( $this->mRevisionsLoaded ) {
+			return true;
+		} else {
+			// Whether it succeeds or fails, we don't want to try again
+			$this->mRevisionsLoaded = true;
+		}
+
+		// Load the new revision object
+		$this->mNewRev = $this->mNewid
+		? Revision::newFromId( $this->mNewid )
+		: Revision::newFromTitle( $this->mTitle );
+		if( !$this->mNewRev instanceof Revision )
+		return false;
+
+		// Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
+		$this->mNewid = $this->mNewRev->getId();
+
+		// Check if page is editable
+		$editable = $this->mNewRev->getTitle()->userCan( 'edit' );
+
+		// Set assorted variables
+		$timestamp = $wgLang->timeanddate( $this->mNewRev->getTimestamp(), true );
+		$this->mNewPage = $this->mNewRev->getTitle();
+		if( $this->mNewRev->isCurrent() ) {
+			$newLink = $this->mNewPage->escapeLocalUrl( 'oldid=' . $this->mNewid );
+			$this->mPagetitle = wfMsgHTML( 'currentrev-asof', $timestamp );
+			$newEdit = $this->mNewPage->escapeLocalUrl( 'action=edit' );
+
+			$this->mNewtitle = "<a href='$newLink'>{$this->mPagetitle}</a>";
+			$this->mNewtitle .= " (<a href='$newEdit'>" . wfMsgHtml( $editable ? 'editold' : 'viewsourceold' ) . "</a>)";
+
+		} else {
+			$newLink = $this->mNewPage->escapeLocalUrl( 'oldid=' . $this->mNewid );
+			$newEdit = $this->mNewPage->escapeLocalUrl( 'action=edit&oldid=' . $this->mNewid );
+			$this->mPagetitle = wfMsgHTML( 'revisionasof', $timestamp );
+
+			$this->mNewtitle = "<a href='$newLink'>{$this->mPagetitle}</a>";
+			$this->mNewtitle .= " (<a href='$newEdit'>" . wfMsgHtml( $editable ? 'editold' : 'viewsourceold' ) . "</a>)";
+		}
+		if ( !$this->mNewRev->userCan(Revision::DELETED_TEXT) ) {
+			$this->mNewtitle = "<span class='history-deleted'>{$this->mPagetitle}</span>";
+		} else if ( $this->mNewRev->isDeleted(Revision::DELETED_TEXT) ) {
+			$this->mNewtitle = '<span class="history-deleted">'.$this->mNewtitle.'</span>';
+		}
+
+		// Load the old revision object
+		$this->mOldRev = false;
+		if( $this->mOldid ) {
+			$this->mOldRev = Revision::newFromId( $this->mOldid );
+		} elseif ( $this->mOldid === 0 ) {
+			$rev = $this->mNewRev->getPrevious();
+			if( $rev ) {
+				$this->mOldid = $rev->getId();
+				$this->mOldRev = $rev;
+			} else {
+				// No previous revision; mark to show as first-version only.
+				$this->mOldid = false;
+				$this->mOldRev = false;
+			}
+		}/* elseif ( $this->mOldid === false ) leave mOldRev false; */
+
+		if( is_null( $this->mOldRev ) ) {
+			return false;
+		}
+
+		if ( $this->mOldRev ) {
+			$this->mOldPage = $this->mOldRev->getTitle();
+
+			$t = $wgLang->timeanddate( $this->mOldRev->getTimestamp(), true );
+			$oldLink = $this->mOldPage->escapeLocalUrl( 'oldid=' . $this->mOldid );
+			$oldEdit = $this->mOldPage->escapeLocalUrl( 'action=edit&oldid=' . $this->mOldid );
+			$this->mOldPagetitle = htmlspecialchars( wfMsg( 'revisionasof', $t ) );
+
+			$this->mOldtitle = "<a href='$oldLink'>{$this->mOldPagetitle}</a>"
+			. " (<a href='$oldEdit'>" . wfMsgHtml( $editable ? 'editold' : 'viewsourceold' ) . "</a>)";
+			// Add an "undo" link
+			$newUndo = $this->mNewPage->escapeLocalUrl( 'action=edit&undoafter=' . $this->mOldid . '&undo=' . $this->mNewid);
+			$htmlLink = htmlspecialchars( wfMsg( 'editundo' ) );
+			$htmlTitle = $wgUser->getSkin()->tooltip( 'undo' );
+			if( $editable && !$this->mOldRev->isDeleted( Revision::DELETED_TEXT ) && !$this->mNewRev->isDeleted( Revision::DELETED_TEXT ) ) {
+				$this->mNewtitle .= " (<a href='$newUndo' $htmlTitle>" . $htmlLink . "</a>)";
+			}
+
+			if( !$this->mOldRev->userCan( Revision::DELETED_TEXT ) ) {
+				$this->mOldtitle = '<span class="history-deleted">' . $this->mOldPagetitle . '</span>';
+			} else if( $this->mOldRev->isDeleted( Revision::DELETED_TEXT ) ) {
+				$this->mOldtitle = '<span class="history-deleted">' . $this->mOldtitle . '</span>';
+			}
+		}
+
+		return true;
+	}
+
+	/**
+	 * Load the text of the revisions, as well as revision data.
+	 */
+	function loadText() {
+		if ( $this->mTextLoaded == 2 ) {
+			return true;
+		} else {
+			// Whether it succeeds or fails, we don't want to try again
+			$this->mTextLoaded = 2;
+		}
+
+		if ( !$this->loadRevisionData() ) {
+			return false;
+		}
+		if ( $this->mOldRev ) {
+			$this->mOldtext = $this->mOldRev->getText( Revision::FOR_THIS_USER );
+			if ( $this->mOldtext === false ) {
+				return false;
+			}
+		}
+		if ( $this->mNewRev ) {
+			$this->mNewtext = $this->mNewRev->getText( Revision::FOR_THIS_USER );
+			if ( $this->mNewtext === false ) {
+				return false;
+			}
+		}
+		return true;
+	}
+
+	/**
+	 * Load the text of the new revision, not the old one
+	 */
+	function loadNewText() {
+		if ( $this->mTextLoaded >= 1 ) {
+			return true;
+		} else {
+			$this->mTextLoaded = 1;
+		}
+		if ( !$this->loadRevisionData() ) {
+			return false;
+		}
+		$this->mNewtext = $this->mNewRev->getText();
+		return true;
+	}
+
+
+}
+
+// A PHP diff engine for phpwiki. (Taken from phpwiki-1.3.3)
+//
+// Copyright (C) 2000, 2001 Geoffrey T. Dairiki <dairiki@dairiki.org>
+// You may copy this code freely under the conditions of the GPL.
+//
+
+define('USE_ASSERTS', function_exists('assert'));
+
+/**
+ * @todo document
+ * @private
+ * @ingroup DifferenceEngine
+ */
+class _DiffOp {
+	var $type;
+	var $orig;
+	var $closing;
+
+	function reverse() {
+		trigger_error('pure virtual', E_USER_ERROR);
+	}
+
+	function norig() {
+		return $this->orig ? sizeof($this->orig) : 0;
+	}
+
+	function nclosing() {
+		return $this->closing ? sizeof($this->closing) : 0;
+	}
+}
+
+/**
+ * @todo document
+ * @private
+ * @ingroup DifferenceEngine
+ */
+class _DiffOp_Copy extends _DiffOp {
+	var $type = 'copy';
+
+	function _DiffOp_Copy ($orig, $closing = false) {
+		if (!is_array($closing))
+		$closing = $orig;
+		$this->orig = $orig;
+		$this->closing = $closing;
+	}
+
+	function reverse() {
+		return new _DiffOp_Copy($this->closing, $this->orig);
+	}
+}
+
+/**
+ * @todo document
+ * @private
+ * @ingroup DifferenceEngine
+ */
+class _DiffOp_Delete extends _DiffOp {
+	var $type = 'delete';
+
+	function _DiffOp_Delete ($lines) {
+		$this->orig = $lines;
+		$this->closing = false;
+	}
+
+	function reverse() {
+		return new _DiffOp_Add($this->orig);
+	}
+}
+
+/**
+ * @todo document
+ * @private
+ * @ingroup DifferenceEngine
+ */
+class _DiffOp_Add extends _DiffOp {
+	var $type = 'add';
+
+	function _DiffOp_Add ($lines) {
+		$this->closing = $lines;
+		$this->orig = false;
+	}
+
+	function reverse() {
+		return new _DiffOp_Delete($this->closing);
+	}
+}
+
+/**
+ * @todo document
+ * @private
+ * @ingroup DifferenceEngine
+ */
+class _DiffOp_Change extends _DiffOp {
+	var $type = 'change';
+
+	function _DiffOp_Change ($orig, $closing) {
+		$this->orig = $orig;
+		$this->closing = $closing;
+	}
+
+	function reverse() {
+		return new _DiffOp_Change($this->closing, $this->orig);
+	}
+}
+
+/**
+ * Class used internally by Diff to actually compute the diffs.
+ *
+ * The algorithm used here is mostly lifted from the perl module
+ * Algorithm::Diff (version 1.06) by Ned Konz, which is available at:
+ *	 http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
+ *
+ * More ideas are taken from:
+ *	 http://www.ics.uci.edu/~eppstein/161/960229.html
+ *
+ * Some ideas are (and a bit of code) are from from analyze.c, from GNU
+ * diffutils-2.7, which can be found at:
+ *	 ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz
+ *
+ * closingly, some ideas (subdivision by NCHUNKS > 2, and some optimizations)
+ * are my own.
+ *
+ * Line length limits for robustness added by Tim Starling, 2005-08-31
+ * Alternative implementation added by Guy Van den Broeck, 2008-07-30
+ *
+ * @author Geoffrey T. Dairiki, Tim Starling, Guy Van den Broeck
+ * @private
+ * @ingroup DifferenceEngine
+ */
+class _DiffEngine {
+
+	const MAX_XREF_LENGTH =  10000;
+
+	function diff ($from_lines, $to_lines){
+		wfProfileIn( __METHOD__ );
+
+		// Diff and store locally
+		$this->diff_local($from_lines, $to_lines);
+
+		// Merge edits when possible
+		$this->_shift_boundaries($from_lines, $this->xchanged, $this->ychanged);
+		$this->_shift_boundaries($to_lines, $this->ychanged, $this->xchanged);
+
+		// Compute the edit operations.
+		$n_from = sizeof($from_lines);
+		$n_to = sizeof($to_lines);
+
+		$edits = array();
+		$xi = $yi = 0;
+		while ($xi < $n_from || $yi < $n_to) {
+			USE_ASSERTS && assert($yi < $n_to || $this->xchanged[$xi]);
+			USE_ASSERTS && assert($xi < $n_from || $this->ychanged[$yi]);
+
+			// Skip matching "snake".
+			$copy = array();
+			while ( $xi < $n_from && $yi < $n_to
+			&& !$this->xchanged[$xi] && !$this->ychanged[$yi]) {
+				$copy[] = $from_lines[$xi++];
+				++$yi;
+			}
+			if ($copy)
+			$edits[] = new _DiffOp_Copy($copy);
+
+			// Find deletes & adds.
+			$delete = array();
+			while ($xi < $n_from && $this->xchanged[$xi])
+			$delete[] = $from_lines[$xi++];
+
+			$add = array();
+			while ($yi < $n_to && $this->ychanged[$yi])
+			$add[] = $to_lines[$yi++];
+
+			if ($delete && $add)
+			$edits[] = new _DiffOp_Change($delete, $add);
+			elseif ($delete)
+			$edits[] = new _DiffOp_Delete($delete);
+			elseif ($add)
+			$edits[] = new _DiffOp_Add($add);
+		}
+		wfProfileOut( __METHOD__ );
+		return $edits;
+	}
+
+	function diff_local ($from_lines, $to_lines) {
+		global $wgExternalDiffEngine;
+		wfProfileIn( __METHOD__);
+
+		if($wgExternalDiffEngine == 'wikidiff3'){
+			// wikidiff3
+			$wikidiff3 = new WikiDiff3();
+			$wikidiff3->diff($from_lines, $to_lines);
+			$this->xchanged = $wikidiff3->removed;
+			$this->ychanged = $wikidiff3->added;
+			unset($wikidiff3);
+		}else{
+			// old diff
+			$n_from = sizeof($from_lines);
+			$n_to = sizeof($to_lines);
+			$this->xchanged = $this->ychanged = array();
+			$this->xv = $this->yv = array();
+			$this->xind = $this->yind = array();
+			unset($this->seq);
+			unset($this->in_seq);
+			unset($this->lcs);
+
+			// Skip leading common lines.
+			for ($skip = 0; $skip < $n_from && $skip < $n_to; $skip++) {
+				if ($from_lines[$skip] !== $to_lines[$skip])
+				break;
+				$this->xchanged[$skip] = $this->ychanged[$skip] = false;
+			}
+			// Skip trailing common lines.
+			$xi = $n_from; $yi = $n_to;
+			for ($endskip = 0; --$xi > $skip && --$yi > $skip; $endskip++) {
+				if ($from_lines[$xi] !== $to_lines[$yi])
+				break;
+				$this->xchanged[$xi] = $this->ychanged[$yi] = false;
+			}
+
+			// Ignore lines which do not exist in both files.
+			for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
+				$xhash[$this->_line_hash($from_lines[$xi])] = 1;
+			}
+
+			for ($yi = $skip; $yi < $n_to - $endskip; $yi++) {
+				$line = $to_lines[$yi];
+				if ( ($this->ychanged[$yi] = empty($xhash[$this->_line_hash($line)])) )
+				continue;
+				$yhash[$this->_line_hash($line)] = 1;
+				$this->yv[] = $line;
+				$this->yind[] = $yi;
+			}
+			for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
+				$line = $from_lines[$xi];
+				if ( ($this->xchanged[$xi] = empty($yhash[$this->_line_hash($line)])) )
+				continue;
+				$this->xv[] = $line;
+				$this->xind[] = $xi;
+			}
+
+			// Find the LCS.
+			$this->_compareseq(0, sizeof($this->xv), 0, sizeof($this->yv));
+		}
+		wfProfileOut( __METHOD__ );
+	}
+
+	/**
+	 * Returns the whole line if it's small enough, or the MD5 hash otherwise
+	 */
+	function _line_hash( $line ) {
+		if ( strlen( $line ) > self::MAX_XREF_LENGTH ) {
+			return md5( $line );
+		} else {
+			return $line;
+		}
+	}
+
+	/* Divide the Largest Common Subsequence (LCS) of the sequences
+	 * [XOFF, XLIM) and [YOFF, YLIM) into NCHUNKS approximately equally
+	 * sized segments.
+	 *
+	 * Returns (LCS, PTS).	LCS is the length of the LCS. PTS is an
+	 * array of NCHUNKS+1 (X, Y) indexes giving the diving points between
+	 * sub sequences.  The first sub-sequence is contained in [X0, X1),
+	 * [Y0, Y1), the second in [X1, X2), [Y1, Y2) and so on.  Note
+	 * that (X0, Y0) == (XOFF, YOFF) and
+	 * (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
+	 *
+	 * This function assumes that the first lines of the specified portions
+	 * of the two files do not match, and likewise that the last lines do not
+	 * match.  The caller must trim matching lines from the beginning and end
+	 * of the portions it is going to specify.
+	 */
+	function _diag ($xoff, $xlim, $yoff, $ylim, $nchunks) {
+		$flip = false;
+
+		if ($xlim - $xoff > $ylim - $yoff) {
+			// Things seems faster (I'm not sure I understand why)
+			// when the shortest sequence in X.
+			$flip = true;
+			list ($xoff, $xlim, $yoff, $ylim)
+			= array( $yoff, $ylim, $xoff, $xlim);
+		}
+
+		if ($flip)
+		for ($i = $ylim - 1; $i >= $yoff; $i--)
+		$ymatches[$this->xv[$i]][] = $i;
+		else
+		for ($i = $ylim - 1; $i >= $yoff; $i--)
+		$ymatches[$this->yv[$i]][] = $i;
+
+		$this->lcs = 0;
+		$this->seq[0]= $yoff - 1;
+		$this->in_seq = array();
+		$ymids[0] = array();
+
+		$numer = $xlim - $xoff + $nchunks - 1;
+		$x = $xoff;
+		for ($chunk = 0; $chunk < $nchunks; $chunk++) {
+			if ($chunk > 0)
+			for ($i = 0; $i <= $this->lcs; $i++)
+			$ymids[$i][$chunk-1] = $this->seq[$i];
+
+			$x1 = $xoff + (int)(($numer + ($xlim-$xoff)*$chunk) / $nchunks);
+			for ( ; $x < $x1; $x++) {
+				$line = $flip ? $this->yv[$x] : $this->xv[$x];
+				if (empty($ymatches[$line]))
+				continue;
+				$matches = $ymatches[$line];
+				reset($matches);
+				while (list ($junk, $y) = each($matches))
+				if (empty($this->in_seq[$y])) {
+					$k = $this->_lcs_pos($y);
+					USE_ASSERTS && assert($k > 0);
+					$ymids[$k] = $ymids[$k-1];
+					break;
+				}
+				while (list ( /* $junk */, $y) = each($matches)) {
+					if ($y > $this->seq[$k-1]) {
+						USE_ASSERTS && assert($y < $this->seq[$k]);
+						// Optimization: this is a common case:
+						//	next match is just replacing previous match.
+						$this->in_seq[$this->seq[$k]] = false;
+						$this->seq[$k] = $y;
+						$this->in_seq[$y] = 1;
+					} else if (empty($this->in_seq[$y])) {
+						$k = $this->_lcs_pos($y);
+						USE_ASSERTS && assert($k > 0);
+						$ymids[$k] = $ymids[$k-1];
+					}
+				}
+			}
+		}
+
+		$seps[] = $flip ? array($yoff, $xoff) : array($xoff, $yoff);
+		$ymid = $ymids[$this->lcs];
+		for ($n = 0; $n < $nchunks - 1; $n++) {
+			$x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $n) / $nchunks);
+			$y1 = $ymid[$n] + 1;
+			$seps[] = $flip ? array($y1, $x1) : array($x1, $y1);
+		}
+		$seps[] = $flip ? array($ylim, $xlim) : array($xlim, $ylim);
+
+		return array($this->lcs, $seps);
+	}
+
+	function _lcs_pos ($ypos) {
+		$end = $this->lcs;
+		if ($end == 0 || $ypos > $this->seq[$end]) {
+			$this->seq[++$this->lcs] = $ypos;
+			$this->in_seq[$ypos] = 1;
+			return $this->lcs;
+		}
+
+		$beg = 1;
+		while ($beg < $end) {
+			$mid = (int)(($beg + $end) / 2);
+			if ( $ypos > $this->seq[$mid] )
+			$beg = $mid + 1;
+			else
+			$end = $mid;
+		}
+
+		USE_ASSERTS && assert($ypos != $this->seq[$end]);
+
+		$this->in_seq[$this->seq[$end]] = false;
+		$this->seq[$end] = $ypos;
+		$this->in_seq[$ypos] = 1;
+		return $end;
+	}
+
+	/* Find LCS of two sequences.
+	 *
+	 * The results are recorded in the vectors $this->{x,y}changed[], by
+	 * storing a 1 in the element for each line that is an insertion
+	 * or deletion (ie. is not in the LCS).
+	 *
+	 * The subsequence of file 0 is [XOFF, XLIM) and likewise for file 1.
+	 *
+	 * Note that XLIM, YLIM are exclusive bounds.
+	 * All line numbers are origin-0 and discarded lines are not counted.
+	 */
+	function _compareseq ($xoff, $xlim, $yoff, $ylim) {
+		// Slide down the bottom initial diagonal.
+		while ($xoff < $xlim && $yoff < $ylim
+		&& $this->xv[$xoff] == $this->yv[$yoff]) {
+			++$xoff;
+			++$yoff;
+		}
+
+		// Slide up the top initial diagonal.
+		while ($xlim > $xoff && $ylim > $yoff
+		&& $this->xv[$xlim - 1] == $this->yv[$ylim - 1]) {
+			--$xlim;
+			--$ylim;
+		}
+
+		if ($xoff == $xlim || $yoff == $ylim)
+		$lcs = 0;
+		else {
+			// This is ad hoc but seems to work well.
+			//$nchunks = sqrt(min($xlim - $xoff, $ylim - $yoff) / 2.5);
+			//$nchunks = max(2,min(8,(int)$nchunks));
+			$nchunks = min(7, $xlim - $xoff, $ylim - $yoff) + 1;
+			list ($lcs, $seps)
+			= $this->_diag($xoff,$xlim,$yoff, $ylim,$nchunks);
+		}
+
+		if ($lcs == 0) {
+			// X and Y sequences have no common subsequence:
+			// mark all changed.
+			while ($yoff < $ylim)
+			$this->ychanged[$this->yind[$yoff++]] = 1;
+			while ($xoff < $xlim)
+			$this->xchanged[$this->xind[$xoff++]] = 1;
+		} else {
+			// Use the partitions to split this problem into subproblems.
+			reset($seps);
+			$pt1 = $seps[0];
+			while ($pt2 = next($seps)) {
+				$this->_compareseq ($pt1[0], $pt2[0], $pt1[1], $pt2[1]);
+				$pt1 = $pt2;
+			}
+		}
+	}
+
+	/* Adjust inserts/deletes of identical lines to join changes
+	 * as much as possible.
+	 *
+	 * We do something when a run of changed lines include a
+	 * line at one end and has an excluded, identical line at the other.
+	 * We are free to choose which identical line is included.
+	 * `compareseq' usually chooses the one at the beginning,
+	 * but usually it is cleaner to consider the following identical line
+	 * to be the "change".
+	 *
+	 * This is extracted verbatim from analyze.c (GNU diffutils-2.7).
+	 */
+	function _shift_boundaries ($lines, &$changed, $other_changed) {
+		wfProfileIn( __METHOD__ );
+		$i = 0;
+		$j = 0;
+
+		USE_ASSERTS && assert('sizeof($lines) == sizeof($changed)');
+		$len = sizeof($lines);
+		$other_len = sizeof($other_changed);
+
+		while (1) {
+			/*
+			 * Scan forwards to find beginning of another run of changes.
+			 * Also keep track of the corresponding point in the other file.
+			 *
+			 * Throughout this code, $i and $j are adjusted together so that
+			 * the first $i elements of $changed and the first $j elements
+			 * of $other_changed both contain the same number of zeros
+			 * (unchanged lines).
+			 * Furthermore, $j is always kept so that $j == $other_len or
+			 * $other_changed[$j] == false.
+			 */
+			while ($j < $other_len && $other_changed[$j])
+			$j++;
+
+			while ($i < $len && ! $changed[$i]) {
+				USE_ASSERTS && assert('$j < $other_len && ! $other_changed[$j]');
+				$i++; $j++;
+				while ($j < $other_len && $other_changed[$j])
+				$j++;
+			}
+
+			if ($i == $len)
+			break;
+
+			$start = $i;
+
+			// Find the end of this run of changes.
+			while (++$i < $len && $changed[$i])
+			continue;
+
+			do {
+				/*
+				 * Record the length of this run of changes, so that
+				 * we can later determine whether the run has grown.
+				 */
+				$runlength = $i - $start;
+
+				/*
+				 * Move the changed region back, so long as the
+				 * previous unchanged line matches the last changed one.
+				 * This merges with previous changed regions.
+				 */
+				while ($start > 0 && $lines[$start - 1] == $lines[$i - 1]) {
+					$changed[--$start] = 1;
+					$changed[--$i] = false;
+					while ($start > 0 && $changed[$start - 1])
+					$start--;
+					USE_ASSERTS && assert('$j > 0');
+					while ($other_changed[--$j])
+					continue;
+					USE_ASSERTS && assert('$j >= 0 && !$other_changed[$j]');
+				}
+
+				/*
+				 * Set CORRESPONDING to the end of the changed run, at the last
+				 * point where it corresponds to a changed run in the other file.
+				 * CORRESPONDING == LEN means no such point has been found.
+				 */
+				$corresponding = $j < $other_len ? $i : $len;
+
+				/*
+				 * Move the changed region forward, so long as the
+				 * first changed line matches the following unchanged one.
+				 * This merges with following changed regions.
+				 * Do this second, so that if there are no merges,
+				 * the changed region is moved forward as far as possible.
+				 */
+				while ($i < $len && $lines[$start] == $lines[$i]) {
+					$changed[$start++] = false;
+					$changed[$i++] = 1;
+					while ($i < $len && $changed[$i])
+					$i++;
+
+					USE_ASSERTS && assert('$j < $other_len && ! $other_changed[$j]');
+					$j++;
+					if ($j < $other_len && $other_changed[$j]) {
+						$corresponding = $i;
+						while ($j < $other_len && $other_changed[$j])
+						$j++;
+					}
+				}
+			} while ($runlength != $i - $start);
+
+			/*
+			 * If possible, move the fully-merged run of changes
+			 * back to a corresponding run in the other file.
+			 */
+			while ($corresponding < $i) {
+				$changed[--$start] = 1;
+				$changed[--$i] = 0;
+				USE_ASSERTS && assert('$j > 0');
+				while ($other_changed[--$j])
+				continue;
+				USE_ASSERTS && assert('$j >= 0 && !$other_changed[$j]');
+			}
+		}
+		wfProfileOut( __METHOD__ );
+	}
+}
+
+/**
+ * Class representing a 'diff' between two sequences of strings.
+ * @todo document
+ * @private
+ * @ingroup DifferenceEngine
+ */
+class Diff
+{
+	var $edits;
+
+	/**
+	 * Constructor.
+	 * Computes diff between sequences of strings.
+	 *
+	 * @param $from_lines array An array of strings.
+	 *		  (Typically these are lines from a file.)
+	 * @param $to_lines array An array of strings.
+	 */
+	function Diff($from_lines, $to_lines) {
+		$eng = new _DiffEngine;
+		$this->edits = $eng->diff($from_lines, $to_lines);
+		//$this->_check($from_lines, $to_lines);
+	}
+
+	/**
+	 * Compute reversed Diff.
+	 *
+	 * SYNOPSIS:
+	 *
+	 *	$diff = new Diff($lines1, $lines2);
+	 *	$rev = $diff->reverse();
+	 * @return object A Diff object representing the inverse of the
+	 *				  original diff.
+	 */
+	function reverse () {
+		$rev = $this;
+		$rev->edits = array();
+		foreach ($this->edits as $edit) {
+			$rev->edits[] = $edit->reverse();
+		}
+		return $rev;
+	}
+
+	/**
+	 * Check for empty diff.
+	 *
+	 * @return bool True iff two sequences were identical.
+	 */
+	function isEmpty () {
+		foreach ($this->edits as $edit) {
+			if ($edit->type != 'copy')
+			return false;
+		}
+		return true;
+	}
+
+	/**
+	 * Compute the length of the Longest Common Subsequence (LCS).
+	 *
+	 * This is mostly for diagnostic purposed.
+	 *
+	 * @return int The length of the LCS.
+	 */
+	function lcs () {
+		$lcs = 0;
+		foreach ($this->edits as $edit) {
+			if ($edit->type == 'copy')
+			$lcs += sizeof($edit->orig);
+		}
+		return $lcs;
+	}
+
+	/**
+	 * Get the original set of lines.
+	 *
+	 * This reconstructs the $from_lines parameter passed to the
+	 * constructor.
+	 *
+	 * @return array The original sequence of strings.
+	 */
+	function orig() {
+		$lines = array();
+
+		foreach ($this->edits as $edit) {
+			if ($edit->orig)
+			array_splice($lines, sizeof($lines), 0, $edit->orig);
+		}
+		return $lines;
+	}
+
+	/**
+	 * Get the closing set of lines.
+	 *
+	 * This reconstructs the $to_lines parameter passed to the
+	 * constructor.
+	 *
+	 * @return array The sequence of strings.
+	 */
+	function closing() {
+		$lines = array();
+
+		foreach ($this->edits as $edit) {
+			if ($edit->closing)
+			array_splice($lines, sizeof($lines), 0, $edit->closing);
+		}
+		return $lines;
+	}
+
+	/**
+	 * Check a Diff for validity.
+	 *
+	 * This is here only for debugging purposes.
+	 */
+	function _check ($from_lines, $to_lines) {
+		wfProfileIn( __METHOD__ );
+		if (serialize($from_lines) != serialize($this->orig()))
+		trigger_error("Reconstructed original doesn't match", E_USER_ERROR);
+		if (serialize($to_lines) != serialize($this->closing()))
+		trigger_error("Reconstructed closing doesn't match", E_USER_ERROR);
+
+		$rev = $this->reverse();
+		if (serialize($to_lines) != serialize($rev->orig()))
+		trigger_error("Reversed original doesn't match", E_USER_ERROR);
+		if (serialize($from_lines) != serialize($rev->closing()))
+		trigger_error("Reversed closing doesn't match", E_USER_ERROR);
+
+
+		$prevtype = 'none';
+		foreach ($this->edits as $edit) {
+			if ( $prevtype == $edit->type )
+			trigger_error("Edit sequence is non-optimal", E_USER_ERROR);
+			$prevtype = $edit->type;
+		}
+
+		$lcs = $this->lcs();
+		trigger_error('Diff okay: LCS = '.$lcs, E_USER_NOTICE);
+		wfProfileOut( __METHOD__ );
+	}
+}
+
+/**
+ * @todo document, bad name.
+ * @private
+ * @ingroup DifferenceEngine
+ */
+class MappedDiff extends Diff
+{
+	/**
+	 * Constructor.
+	 *
+	 * Computes diff between sequences of strings.
+	 *
+	 * This can be used to compute things like
+	 * case-insensitve diffs, or diffs which ignore
+	 * changes in white-space.
+	 *
+	 * @param $from_lines array An array of strings.
+	 *	(Typically these are lines from a file.)
+	 *
+	 * @param $to_lines array An array of strings.
+	 *
+	 * @param $mapped_from_lines array This array should
+	 *	have the same size number of elements as $from_lines.
+	 *	The elements in $mapped_from_lines and
+	 *	$mapped_to_lines are what is actually compared
+	 *	when computing the diff.
+	 *
+	 * @param $mapped_to_lines array This array should
+	 *	have the same number of elements as $to_lines.
+	 */
+	function MappedDiff($from_lines, $to_lines,
+	$mapped_from_lines, $mapped_to_lines) {
+		wfProfileIn( __METHOD__ );
+
+		assert(sizeof($from_lines) == sizeof($mapped_from_lines));
+		assert(sizeof($to_lines) == sizeof($mapped_to_lines));
+
+		$this->Diff($mapped_from_lines, $mapped_to_lines);
+
+		$xi = $yi = 0;
+		for ($i = 0; $i < sizeof($this->edits); $i++) {
+			$orig = &$this->edits[$i]->orig;
+			if (is_array($orig)) {
+				$orig = array_slice($from_lines, $xi, sizeof($orig));
+				$xi += sizeof($orig);
+			}
+
+			$closing = &$this->edits[$i]->closing;
+			if (is_array($closing)) {
+				$closing = array_slice($to_lines, $yi, sizeof($closing));
+				$yi += sizeof($closing);
+			}
+		}
+		wfProfileOut( __METHOD__ );
+	}
+}
+
+/**
+ * A class to format Diffs
+ *
+ * This class formats the diff in classic diff format.
+ * It is intended that this class be customized via inheritance,
+ * to obtain fancier outputs.
+ * @todo document
+ * @private
+ * @ingroup DifferenceEngine
+ */
+class DiffFormatter {
+	/**
+	 * Number of leading context "lines" to preserve.
+	 *
+	 * This should be left at zero for this class, but subclasses
+	 * may want to set this to other values.
+	 */
+	var $leading_context_lines = 0;
+
+	/**
+	 * Number of trailing context "lines" to preserve.
+	 *
+	 * This should be left at zero for this class, but subclasses
+	 * may want to set this to other values.
+	 */
+	var $trailing_context_lines = 0;
+
+	/**
+	 * Format a diff.
+	 *
+	 * @param $diff object A Diff object.
+	 * @return string The formatted output.
+	 */
+	function format($diff) {
+		wfProfileIn( __METHOD__ );
+
+		$xi = $yi = 1;
+		$block = false;
+		$context = array();
+
+		$nlead = $this->leading_context_lines;
+		$ntrail = $this->trailing_context_lines;
+
+		$this->_start_diff();
+
+		foreach ($diff->edits as $edit) {
+			if ($edit->type == 'copy') {
+				if (is_array($block)) {
+					if (sizeof($edit->orig) <= $nlead + $ntrail) {
+						$block[] = $edit;
+					}
+					else{
+						if ($ntrail) {
+							$context = array_slice($edit->orig, 0, $ntrail);
+							$block[] = new _DiffOp_Copy($context);
+						}
+						$this->_block($x0, $ntrail + $xi - $x0,
+						$y0, $ntrail + $yi - $y0,
+						$block);
+						$block = false;
+					}
+				}
+				$context = $edit->orig;
+			}
+			else {
+				if (! is_array($block)) {
+					$context = array_slice($context, sizeof($context) - $nlead);
+					$x0 = $xi - sizeof($context);
+					$y0 = $yi - sizeof($context);
+					$block = array();
+					if ($context)
+					$block[] = new _DiffOp_Copy($context);
+				}
+				$block[] = $edit;
+			}
+
+			if ($edit->orig)
+			$xi += sizeof($edit->orig);
+			if ($edit->closing)
+			$yi += sizeof($edit->closing);
+		}
+
+		if (is_array($block))
+		$this->_block($x0, $xi - $x0,
+		$y0, $yi - $y0,
+		$block);
+
+		$end = $this->_end_diff();
+		wfProfileOut( __METHOD__ );
+		return $end;
+	}
+
+	function _block($xbeg, $xlen, $ybeg, $ylen, &$edits) {
+		wfProfileIn( __METHOD__ );
+		$this->_start_block($this->_block_header($xbeg, $xlen, $ybeg, $ylen));
+		foreach ($edits as $edit) {
+			if ($edit->type == 'copy')
+			$this->_context($edit->orig);
+			elseif ($edit->type == 'add')
+			$this->_added($edit->closing);
+			elseif ($edit->type == 'delete')
+			$this->_deleted($edit->orig);
+			elseif ($edit->type == 'change')
+			$this->_changed($edit->orig, $edit->closing);
+			else
+			trigger_error('Unknown edit type', E_USER_ERROR);
+		}
+		$this->_end_block();
+		wfProfileOut( __METHOD__ );
+	}
+
+	function _start_diff() {
+		ob_start();
+	}
+
+	function _end_diff() {
+		$val = ob_get_contents();
+		ob_end_clean();
+		return $val;
+	}
+
+	function _block_header($xbeg, $xlen, $ybeg, $ylen) {
+		if ($xlen > 1)
+		$xbeg .= "," . ($xbeg + $xlen - 1);
+		if ($ylen > 1)
+		$ybeg .= "," . ($ybeg + $ylen - 1);
+
+		return $xbeg . ($xlen ? ($ylen ? 'c' : 'd') : 'a') . $ybeg;
+	}
+
+	function _start_block($header) {
+		echo $header . "\n";
+	}
+
+	function _end_block() {
+	}
+
+	function _lines($lines, $prefix = ' ') {
+		foreach ($lines as $line)
+		echo "$prefix $line\n";
+	}
+
+	function _context($lines) {
+		$this->_lines($lines);
+	}
+
+	function _added($lines) {
+		$this->_lines($lines, '>');
+	}
+	function _deleted($lines) {
+		$this->_lines($lines, '<');
+	}
+
+	function _changed($orig, $closing) {
+		$this->_deleted($orig);
+		echo "---\n";
+		$this->_added($closing);
+	}
+}
+
+/**
+ * A formatter that outputs unified diffs
+ * @ingroup DifferenceEngine
+ */
+
+class UnifiedDiffFormatter extends DiffFormatter {
+	var $leading_context_lines = 2;
+	var $trailing_context_lines = 2;
+
+	function _added($lines) {
+		$this->_lines($lines, '+');
+	}
+	function _deleted($lines) {
+		$this->_lines($lines, '-');
+	}
+	function _changed($orig, $closing) {
+		$this->_deleted($orig);
+		$this->_added($closing);
+	}
+	function _block_header($xbeg, $xlen, $ybeg, $ylen) {
+		return "@@ -$xbeg,$xlen +$ybeg,$ylen @@";
+	}
+}
+
+/**
+ * A pseudo-formatter that just passes along the Diff::$edits array
+ * @ingroup DifferenceEngine
+ */
+class ArrayDiffFormatter extends DiffFormatter {
+	function format($diff) {
+		$oldline = 1;
+		$newline = 1;
+		$retval = array();
+		foreach($diff->edits as $edit)
+		switch($edit->type) {
+			case 'add':
+				foreach($edit->closing as $l) {
+					$retval[] = array(
+							'action' => 'add',
+							'new'=> $l,
+							'newline' => $newline++
+					);
+				}
+				break;
+			case 'delete':
+				foreach($edit->orig as $l) {
+					$retval[] = array(
+							'action' => 'delete',
+							'old' => $l,
+							'oldline' => $oldline++,
+					);
+				}
+				break;
+			case 'change':
+				foreach($edit->orig as $i => $l) {
+					$retval[] = array(
+							'action' => 'change',
+							'old' => $l,
+							'new' => @$edit->closing[$i],
+							'oldline' => $oldline++,
+							'newline' => $newline++,
+					);
+				}
+				break;
+			case 'copy':
+				$oldline += count($edit->orig);
+				$newline += count($edit->orig);
+		}
+		return $retval;
+	}
+}
+
+/**
+ *	Additions by Axel Boldt follow, partly taken from diff.php, phpwiki-1.3.3
+ *
+ */
+
+define('NBSP', '&#160;'); // iso-8859-x non-breaking space.
+
+/**
+ * @todo document
+ * @private
+ * @ingroup DifferenceEngine
+ */
+class _HWLDF_WordAccumulator {
+	function _HWLDF_WordAccumulator () {
+		$this->_lines = array();
+		$this->_line = '';
+		$this->_group = '';
+		$this->_tag = '';
+	}
+
+	function _flushGroup ($new_tag) {
+		if ($this->_group !== '') {
+			if ($this->_tag == 'ins')
+			$this->_line .= '<ins class="diffchange diffchange-inline">' .
+			htmlspecialchars ( $this->_group ) . '</ins>';
+			elseif ($this->_tag == 'del')
+			$this->_line .= '<del class="diffchange diffchange-inline">' .
+			htmlspecialchars ( $this->_group ) . '</del>';
+			else
+			$this->_line .= htmlspecialchars ( $this->_group );
+		}
+		$this->_group = '';
+		$this->_tag = $new_tag;
+	}
+
+	function _flushLine ($new_tag) {
+		$this->_flushGroup($new_tag);
+		if ($this->_line != '')
+		array_push ( $this->_lines, $this->_line );
+		else
+		# make empty lines visible by inserting an NBSP
+		array_push ( $this->_lines, NBSP );
+		$this->_line = '';
+	}
+
+	function addWords ($words, $tag = '') {
+		if ($tag != $this->_tag)
+		$this->_flushGroup($tag);
+
+		foreach ($words as $word) {
+			// new-line should only come as first char of word.
+			if ($word == '')
+			continue;
+			if ($word[0] == "\n") {
+				$this->_flushLine($tag);
+				$word = substr($word, 1);
+			}
+			assert(!strstr($word, "\n"));
+			$this->_group .= $word;
+		}
+	}
+
+	function getLines() {
+		$this->_flushLine('~done');
+		return $this->_lines;
+	}
+}
+
+/**
+ * @todo document
+ * @private
+ * @ingroup DifferenceEngine
+ */
+class WordLevelDiff extends MappedDiff {
+	const MAX_LINE_LENGTH = 10000;
+
+	function WordLevelDiff ($orig_lines, $closing_lines) {
+		wfProfileIn( __METHOD__ );
+
+		list ($orig_words, $orig_stripped) = $this->_split($orig_lines);
+		list ($closing_words, $closing_stripped) = $this->_split($closing_lines);
+
+		$this->MappedDiff($orig_words, $closing_words,
+		$orig_stripped, $closing_stripped);
+		wfProfileOut( __METHOD__ );
+	}
+
+	function _split($lines) {
+		wfProfileIn( __METHOD__ );
+
+		$words = array();
+		$stripped = array();
+		$first = true;
+		foreach ( $lines as $line ) {
+			# If the line is too long, just pretend the entire line is one big word
+			# This prevents resource exhaustion problems
+			if ( $first ) {
+				$first = false;
+			} else {
+				$words[] = "\n";
+				$stripped[] = "\n";
+			}
+			if ( strlen( $line ) > self::MAX_LINE_LENGTH ) {
+				$words[] = $line;
+				$stripped[] = $line;
+			} else {
+				$m = array();
+				if (preg_match_all('/ ( [^\S\n]+ | [0-9_A-Za-z\x80-\xff]+ | . ) (?: (?!< \n) [^\S\n])? /xs',
+				$line, $m))
+				{
+					$words = array_merge( $words, $m[0] );
+					$stripped = array_merge( $stripped, $m[1] );
+				}
+			}
+		}
+		wfProfileOut( __METHOD__ );
+		return array($words, $stripped);
+	}
+
+	function orig () {
+		wfProfileIn( __METHOD__ );
+		$orig = new _HWLDF_WordAccumulator;
+
+		foreach ($this->edits as $edit) {
+			if ($edit->type == 'copy')
+			$orig->addWords($edit->orig);
+			elseif ($edit->orig)
+			$orig->addWords($edit->orig, 'del');
+		}
+		$lines = $orig->getLines();
+		wfProfileOut( __METHOD__ );
+		return $lines;
+	}
+
+	function closing () {
+		wfProfileIn( __METHOD__ );
+		$closing = new _HWLDF_WordAccumulator;
+
+		foreach ($this->edits as $edit) {
+			if ($edit->type == 'copy')
+			$closing->addWords($edit->closing);
+			elseif ($edit->closing)
+			$closing->addWords($edit->closing, 'ins');
+		}
+		$lines = $closing->getLines();
+		wfProfileOut( __METHOD__ );
+		return $lines;
+	}
+}
+
+/**
+ * Wikipedia Table style diff formatter.
+ * @todo document
+ * @private
+ * @ingroup DifferenceEngine
+ */
+class TableDiffFormatter extends DiffFormatter {
+	function TableDiffFormatter() {
+		$this->leading_context_lines = 2;
+		$this->trailing_context_lines = 2;
+	}
+
+	public static function escapeWhiteSpace( $msg ) {
+		$msg = preg_replace( '/^ /m', '&nbsp; ', $msg );
+		$msg = preg_replace( '/ $/m', ' &nbsp;', $msg );
+		$msg = preg_replace( '/  /', '&nbsp; ', $msg );
+		return $msg;
+	}
+
+	function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
+		$r = '<tr><td colspan="2" class="diff-lineno"><!--LINE '.$xbeg."--></td>\n" .
+		  '<td colspan="2" class="diff-lineno"><!--LINE '.$ybeg."--></td></tr>\n";
+		return $r;
+	}
+
+	function _start_block( $header ) {
+		echo $header;
+	}
+
+	function _end_block() {
+	}
+
+	function _lines( $lines, $prefix=' ', $color='white' ) {
+	}
+
+	# HTML-escape parameter before calling this
+	function addedLine( $line ) {
+		return $this->wrapLine( '+', 'diff-addedline', $line );
+	}
+
+	# HTML-escape parameter before calling this
+	function deletedLine( $line ) {
+		return $this->wrapLine( '-', 'diff-deletedline', $line );
+	}
+
+	# HTML-escape parameter before calling this
+	function contextLine( $line ) {
+		return $this->wrapLine( ' ', 'diff-context', $line );
+	}
+
+	private function wrapLine( $marker, $class, $line ) {
+		if( $line !== '' ) {
+			// The <div> wrapper is needed for 'overflow: auto' style to scroll properly
+			$line = Xml::tags( 'div', null, $this->escapeWhiteSpace( $line ) );
+		}
+		return "<td class='diff-marker'>$marker</td><td class='$class'>$line</td>";
+	}
+
+	function emptyLine() {
+		return '<td colspan="2">&nbsp;</td>';
+	}
+
+	function _added( $lines ) {
+		foreach ($lines as $line) {
+			echo '<tr>' . $this->emptyLine() .
+			$this->addedLine( '<ins class="diffchange">' .
+			htmlspecialchars ( $line ) . '</ins>' ) . "</tr>\n";
+		}
+	}
+
+	function _deleted($lines) {
+		foreach ($lines as $line) {
+			echo '<tr>' . $this->deletedLine( '<del class="diffchange">' .
+			htmlspecialchars ( $line ) . '</del>' ) .
+			$this->emptyLine() . "</tr>\n";
+		}
+	}
+
+	function _context( $lines ) {
+		foreach ($lines as $line) {
+			echo '<tr>' .
+			$this->contextLine( htmlspecialchars ( $line ) ) .
+			$this->contextLine( htmlspecialchars ( $line ) ) . "</tr>\n";
+		}
+	}
+
+	function _changed( $orig, $closing ) {
+		wfProfileIn( __METHOD__ );
+
+		$diff = new WordLevelDiff( $orig, $closing );
+		$del = $diff->orig();
+		$add = $diff->closing();
+
+		# Notice that WordLevelDiff returns HTML-escaped output.
+		# Hence, we will be calling addedLine/deletedLine without HTML-escaping.
+
+		while ( $line = array_shift( $del ) ) {
+			$aline = array_shift( $add );
+			echo '<tr>' . $this->deletedLine( $line ) .
+			$this->addedLine( $aline ) . "</tr>\n";
+		}
+		foreach ($add as $line) {	# If any leftovers
+			echo '<tr>' . $this->emptyLine() .
+			$this->addedLine( $line ) . "</tr>\n";
+		}
+		wfProfileOut( __METHOD__ );
+	}
+}