buffer,string_decoder: consolidate encoding validation logic

Buffer.isEncoding and string_decoder.normalizeEncoding shared
quite a bit of logic. This moves the primary logic into
internal/util. The userland modules that monkey patch Buffer.isEncoding
should still work.

PR-URL: https://github.com/nodejs/node/pull/7207
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/lib/internal/util.js b/lib/internal/util.js
index a0c2412dce..8e7e51aab9 100644
--- a/lib/internal/util.js
+++ b/lib/internal/util.js
@@ -92,3 +92,32 @@ exports.assertCrypto = function(exports) {
   if (noCrypto)
     throw new Error('Node.js is not compiled with openssl crypto support');
 };
+
+exports.kIsEncodingSymbol = Symbol('node.isEncoding');
+exports.normalizeEncoding = function normalizeEncoding(enc) {
+  if (!enc) return 'utf8';
+  var low;
+  for (;;) {
+    switch (enc) {
+      case 'utf8':
+      case 'utf-8':
+        return 'utf8';
+      case 'ucs2':
+      case 'utf16le':
+      case 'ucs-2':
+      case 'utf-16le':
+        return 'utf16le';
+      case 'binary':
+        return 'latin1';
+      case 'base64':
+      case 'ascii':
+      case 'latin1':
+      case 'hex':
+        return enc;
+      default:
+        if (low) return; // undefined
+        enc = ('' + enc).toLowerCase();
+        low = true;
+    }
+  }
+};