Parser: use (slower?) pure-JS fallback for encodings that iconv-lite does not support

lib/Parser.js

@@ -3,7 +3,8 @@ var EventEmitter = require('events').EventEmitter,
     inherits = require('util').inherits,
     inspect = require('util').inspect,
     utf7 = require('utf7').imap,
-    iconv = require('iconv-lite');
+    iconv = require('iconv-lite'),
+    jsencoding/*lazy-loaded*/;
 
 var CH_LF = 10,
     LITPLACEHOLDER = String.fromCharCode(0),
@@ -674,13 +675,26 @@ function convStr(str, literals) {
   return str;
 }
 
+function decodeBytes(buf, encoding) {
+  if (iconv.encodingExists(encoding))
+    return iconv.decode(buf, encoding);
+  else {
+    if (!jsencoding)
+      jsencoding = require('../deps/encoding/encoding');
+    if (jsencoding.encodingExists(encoding))
+      return jsencoding.TextDecoder(encoding).decode(buf);
+    else
+      return buf.toString('binary');
+  }
+}
+
 function decodeWords(str) {
   return str.replace(RE_ENCWORD,
     function(match, charset, encoding, word) {
       encoding = encoding.toLowerCase();
       if (encoding === 'q') {
         // q-encoding, similar to quoted-printable
-        return iconv.decode(new Buffer(word.replace(RE_QENC,
+        return decodeBytes(new Buffer(word.replace(RE_QENC,
           function(match2, byte) {
             if (match2 === '_')
               return ' ';
@@ -690,7 +704,7 @@ function decodeWords(str) {
         ), 'binary'), charset);
       } else {
         // base64
-        return iconv.decode(new Buffer(word, 'base64'), charset);
+        return decodeBytes(new Buffer(word, 'base64'), charset);
       }
   });
 }