Merge "Remove extra unneeded whitespace"

[lhc/web/wiklou.git] / includes / HistoryBlob.php

diff --git a/includes/HistoryBlob.php b/includes/HistoryBlob.php
index cece3ec..bb8ec5e 100644 (file)
--- a/includes/HistoryBlob.php
+++ b/includes/HistoryBlob.php
@@ -1,5 +1,25 @@
 <?php
-
+/**
+ * Efficient concatenated text storage.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ */
+ 
 /**
  * Base class for general text storage via the "object" flag in old_flags, or 
  * two-part external storage URLs. Used for represent efficient concatenated 
@@ -515,14 +535,11 @@ class DiffHistoryBlob implements HistoryBlob {
 
                $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" );
-                               // Temp patch for bug 34428: don't return false
-                               //return false;
-                       }
+               # Check the checksum if hash/mhash is available
+               $ofp = $this->xdiffAdler32( $base );
+               if ( $ofp !== false && $ofp !== substr( $diff, 0, 4 ) ) {
+                       wfDebug( __METHOD__. ": incorrect base checksum\n" );
+                       return false;
                }
                if ( $header['csize'] != strlen( $base ) ) {
                        wfDebug( __METHOD__. ": incorrect base length\n" );
@@ -561,6 +578,30 @@ class DiffHistoryBlob implements HistoryBlob {
                return $out;
        }
 
+       /**
+        * Compute a binary "Adler-32" checksum as defined by LibXDiff, i.e. with 
+        * the bytes backwards and initialised with 0 instead of 1. See bug 34428.
+        *
+        * Returns false if no hashing library is available
+        */
+       function xdiffAdler32( $s ) {
+               static $init;
+               if ( $init === null ) {
+                       $init = str_repeat( "\xf0", 205 ) . "\xee" . str_repeat( "\xf0", 67 ) . "\x02";
+               }
+               // The real Adler-32 checksum of $init is zero, so it initialises the 
+               // state to zero, as it is at the start of LibXDiff's checksum 
+               // algorithm. Appending the subject string then simulates LibXDiff.
+               if ( function_exists( 'hash' ) ) {
+                       $hash = hash( 'adler32', $init . $s, true );
+               } elseif ( function_exists( 'mhash' ) ) {
+                       $hash = mhash( MHASH_ADLER32, $init . $s );
+               } else {
+                       return false;
+               }
+               return strrev( $hash );
+       }
+
        function uncompress() {
                if ( !$this->mDiffs ) {
                        return;