Ensure that hash directory computation is the same on both 32 and 64 bit architectures (#2596879) (Thanks to Mike Sweetser)

ChangeLog

@@ -270,6 +270,8 @@ Version 1.5.2 - SVN
   - Make all submit button names unique on compose screen
   - Make address book file permissions 0600 - same as preference files
   - Added compatibility with Dovecot's bigint UIDs
+  - Ensure that hash directory computation is the same on both 32 and
+    64 bit architectures (#2596879).
 
 Version 1.5.1 (branched on 2006-02-12)
 --------------------------------------

functions/prefs.php

@@ -117,8 +117,15 @@ function getHashedDir($username, $dir, $hash_dirs = '') {
  * @since 1.2.0
  */
 function computeHashDirs($username) {
-    /* Compute the hash for this user and extract the hash directories. */
-    $hash = base_convert(crc32($username), 10, 16);
+    /* Compute the hash for this user and extract the hash directories.  */ 
+    /* Note that the crc32() function result will be different on 32 and */ 
+    /* 64 bit systems, thus the hack below.                              */
+    $crc = crc32($username);
+    if ($crc & 0x80000000) {
+        $crc ^= 0xffffffff;
+        $crc += 1;
+    }
+    $hash = base_convert($crc, 10, 16);
     $hash_dirs = array();
     for ($h = 0; $h < 4; ++ $h) {
         $hash_dirs[] = substr($hash, $h, 1);