From d1e81fec8bc718930ce4b040decfefcadaffe7b6 Mon Sep 17 00:00:00 2001
From: Andrew Garrett <werdna@users.mediawiki.org>
Date: Thu, 17 Jul 2008 12:19:51 +0000
Subject: [PATCH] Add wfDiff function, similar to wfMerge (some copied), used
 in AbuseFilter extension to generate a line-by-line machine-readable diff
 between two texts. Shells out to diff utility.

---
 includes/DefaultSettings.php |  5 +++
 includes/GlobalFunctions.php | 60 ++++++++++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+)

diff --git a/includes/DefaultSettings.php b/includes/DefaultSettings.php
index 29e52321fa..058cbce8a0 100644
--- a/includes/DefaultSettings.php
+++ b/includes/DefaultSettings.php
@@ -1738,6 +1738,11 @@ $wgAntiLockFlags = 0;
  */
 $wgDiff3 = '/usr/bin/diff3';
 
+/**
+ * Path to the GNU diff utility.
+ */
+$wgDiff = '/usr/bin/diff';
+
 /**
  * We can also compress text stored in the 'text' table. If this is set on, new
  * revisions will be compressed on page save if zlib support is available. Any
diff --git a/includes/GlobalFunctions.php b/includes/GlobalFunctions.php
index 8185a7fa5f..7dbe0dd337 100644
--- a/includes/GlobalFunctions.php
+++ b/includes/GlobalFunctions.php
@@ -1178,6 +1178,66 @@ function wfMerge( $old, $mine, $yours, &$result ){
 	return ! $conflict;
 }
 
+/**
+ * Returns unified plain-text diff of two texts.
+ * Useful for machine processing of diffs.
+ * @param $before string The text before the changes.
+ * @param $after string The text after the changes.
+ * @param $params string Command-line options for the diff command.
+ * @return string Unified diff of $before and $after
+ */
+function wfDiff( $before, $after, $params = '-u' ) {
+	global $wgDiff;
+
+	# This check may also protect against code injection in
+	# case of broken installations.
+	if(! file_exists( $wgDiff ) ){
+		wfDebug( "diff3 not found\n" );
+		return false;
+	}
+
+	# Make temporary files
+	$td = wfTempDir();
+	$oldtextFile = fopen( $oldtextName = tempnam( $td, 'merge-old-' ), 'w' );
+	$newtextFile = fopen( $newtextName = tempnam( $td, 'merge-your-' ), 'w' );
+
+	fwrite( $oldtextFile, $before ); fclose( $oldtextFile );
+	fwrite( $newtextFile, $after ); fclose( $newtextFile );
+	
+	// Get the diff of the two files
+	$cmd = "$wgDiff " . $params . ' ' .wfEscapeShellArg( $oldtextName, $newtextName );
+	
+	$h = popen( $cmd, 'r' );
+	
+	$diff = '';
+	
+	do {
+		$data = fread( $h, 8192 );
+		if ( strlen( $data ) == 0 ) {
+			break;
+		}
+		$diff .= $data;
+	} while ( true );
+	
+	// Clean up
+	pclose( $h );
+	unlink( $oldtextName );
+	unlink( $newtextName );
+	
+	// Kill the --- and +++ lines. They're not useful.
+	$diff_lines = explode( "\n", $diff );
+	if (strpos( '---', $diff_lines[0] ) == 0) {
+		unset($diff_lines[0]);
+	}
+	if (strpos( '+++', $diff_lines[1] ) == 0) {
+		unset($diff_lines[1]);
+	}
+	
+	$diff = implode( "\n", $diff_lines );
+	
+	return $diff;
+}
+
 /**
  * @todo document
  */
-- 
2.20.1