-added encoding detection for attachment names when message part hasn't got charset definition (#1484969)

program/include/rcube_imap.php

@@ -1162,7 +1162,10 @@ class rcube_imap
 
     // normalize filename property
     if ($filename_mime = $struct->d_parameters['filename'] ? $struct->d_parameters['filename'] : $struct->ctype_parameters['name'])
-      $struct->filename = rcube_imap::decode_mime_string($filename_mime, $this->default_charset);
+    {
+      $struct->filename = rcube_imap::decode_mime_string($filename_mime, 
+    	    $struct->charset ? $struct->charset : rc_detect_encoding($filename_mime, $this->default_charset));
+    }
     else if ($filename_encoded = $struct->d_parameters['filename*'] ? $struct->d_parameters['filename*'] : $struct->ctype_parameters['name*'])
     {
       // decode filename according to RFC 2231, Section 4
@@ -1170,7 +1173,8 @@ class rcube_imap
       $struct->filename = rcube_charset_convert(urldecode($filename_urlencoded), $filename_charset);
     }
     else if (!empty($struct->headers['content-description']))
-      $struct->filename = rcube_imap::decode_mime_string($struct->headers['content-description'], $this->default_charset);
+      $struct->filename = rcube_imap::decode_mime_string($struct->headers['content-description'],
+    	    $struct->charset ? $struct->charset : rc_detect_encoding($struct->headers['content-description'],$this->default_charset));
       
     return $struct;
     }

program/include/rcube_shared.inc

@@ -581,4 +581,33 @@ function rc_mime_content_type($path, $failover = 'unknown/unknown')
     return $mime_type;
 }
 
+
+/**
+ * A method to guess encoding of a string.
+ *
+ * @param string $string     	String.
+ * @param string $failover 	Default result for failover.
+ *
+ * @return string
+ */
+function rc_detect_encoding($string, $failover='')
+{
+    if (!function_exists('mb_detect_encoding')) {
+        return $failover;
+    }
+
+    // FIXME: the order is important, because sometimes 
+    // iso string is detected as euc-jp and etc.
+    $enc = array(
+	'UTF-8', 'ISO-8859-1', 'ISO-8859-2', 'ISO-8859-3', 'ISO-8859-4',
+	'ISO-8859-5', 'ISO-8859-6', 'ISO-8859-7', 'ISO-8859-8', 'ISO-8859-9',
+	'ISO-8859-10', 'ISO-8859-13', 'ISO-8859-14', 'ISO-8859-15', 'ISO-8859-16',
+	'WINDOWS-1252', 'WINDOWS-1251', 'EUC-JP', 'EUC-TW', 'KOI8-R'
+    );
+
+    $result = mb_detect_encoding($string, join(',', $enc));
+
+    return $result ? $result : $failover;
+}
+
 ?>