Implemented xdiff_string_bpatch() in pure PHP, allowing DiffHistoryBlob objects to...

diff --git a/includes/HistoryBlob.php b/includes/HistoryBlob.php
index 7489399..323d107 100644 (file)
--- a/includes/HistoryBlob.php
+++ b/includes/HistoryBlob.php
@@ -319,11 +319,13 @@ class DiffHistoryBlob implements HistoryBlob {
         * The maximum number of text items before the object becomes sad
         */
        var $mMaxCount = 100;
+       
+       /** Constants from xdiff.h */
+       const XDL_BDOP_INS = 1;
+       const XDL_BDOP_CPY = 2;
+       const XDL_BDOP_INSB = 3;
 
        function __construct() {
-               if ( !function_exists( 'xdiff_string_bdiff' ) ){ 
-                       throw new MWException( "Need xdiff 1.5+ support to read or write DiffHistoryBlob\n" );
-               }
                if ( !function_exists( 'gzdeflate' ) ) {
                        throw new MWException( "Need zlib support to read or write DiffHistoryBlob\n" );
                }
@@ -353,6 +355,9 @@ class DiffHistoryBlob implements HistoryBlob {
        }
 
        function compress() {
+               if ( !function_exists( 'xdiff_string_bdiff' ) ){ 
+                       throw new MWException( "Need xdiff 1.5+ support to write DiffHistoryBlob\n" );
+               }
                if ( isset( $this->mDiffs ) ) {
                        // Already compressed
                        return;
@@ -431,10 +436,60 @@ class DiffHistoryBlob implements HistoryBlob {
        }
 
        function patch( $base, $diff ) {
-               wfSuppressWarnings();
-               $text = xdiff_string_bpatch( $base, $diff ) . '';
-               wfRestoreWarnings();
-               return $text;
+               if ( function_exists( 'xdiff_string_bpatch' ) ) {
+                       wfSuppressWarnings();
+                       $text = xdiff_string_bpatch( $base, $diff ) . '';
+                       wfRestoreWarnings();
+                       return $text;
+               }
+
+               # Pure PHP implementation
+
+               $header = unpack( 'Vofp/Vcsize', substr( $diff, 0, 8 ) );
+               
+               # Check the checksum if mhash is available
+               if ( extension_loaded( 'mhash' ) ) {
+                       $ofp = mhash( MHASH_ADLER32, $base );
+                       if ( $ofp !== substr( $diff, 0, 4 ) ) {
+                               wfDebug( __METHOD__. ": incorrect base checksum\n" );
+                               return false;
+                       }
+               }
+               if ( $header['csize'] != strlen( $base ) ) {
+                       wfDebug( __METHOD__. ": incorrect base length {$header['csize']} -> {strlen($base)}\n" );
+                       return false;
+               }
+               
+               $p = 8;
+               $out = '';
+               while ( $p < strlen( $diff ) ) {
+                       $x = unpack( 'Cop', substr( $diff, $p, 1 ) );
+                       $op = $x['op'];
+                       ++$p;
+                       switch ( $op ) {
+                       case self::XDL_BDOP_INS:
+                               $x = unpack( 'Csize', substr( $diff, $p, 1 ) );
+                               $p++;
+                               $out .= substr( $diff, $p, $x['size'] );
+                               $p += $x['size'];
+                               break;
+                       case self::XDL_BDOP_INSB:
+                               $x = unpack( 'Vcsize', substr( $diff, $p, 4 ) );
+                               $p += 4;
+                               $out .= substr( $diff, $p, $x['csize'] );
+                               $p += $x['csize'];
+                               break;
+                       case self::XDL_BDOP_CPY:
+                               $x = unpack( 'Voff/Vcsize', substr( $diff, $p, 8 ) );
+                               $p += 8;
+                               $out .= substr( $base, $x['off'], $x['csize'] );
+                               break;
+                       default:
+                               wfDebug( __METHOD__.": invalid op\n" );
+                               return false;
+                       }
+               }
+               return $out;
        }
 
        function uncompress() {