buffer: make byteLength work with Buffer correctly

JacksonTian · jasnell · commit 8d0ca1075203 · 2016-01-18T08:54:38.000-08:00
Make the byteLength work correctly when input is Buffer. e.g: ```js // The incomplete unicode string Buffer.byteLength(new Buffer([0xe4, 0xb8, 0xad, 0xe6, 0x96])) ``` The old output: 9 The new output: 5 PR-URL: #4738 Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Brian White <mscdex@mscdex.net> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
diff --git a/lib/buffer.js b/lib/buffer.js
@@ -262,6 +262,9 @@ function base64ByteLength(str, bytes) {
 
 
 function byteLength(string, encoding) {
+  if (string instanceof Buffer)
+    return string.length;
+
   if (typeof string !== 'string')
     string = '' + string;
 
diff --git a/test/parallel/test-buffer-bytelength.js b/test/parallel/test-buffer-bytelength.js
@@ -10,6 +10,12 @@ assert.equal(Buffer.byteLength(NaN, 'utf8'), 3);
 assert.equal(Buffer.byteLength({}, 'binary'), 15);
 assert.equal(Buffer.byteLength(), 9);
 
+// buffer
+var incomplete = new Buffer([0xe4, 0xb8, 0xad, 0xe6, 0x96]);
+assert.equal(Buffer.byteLength(incomplete), 5);
+var ascii = new Buffer('abc');
+assert.equal(Buffer.byteLength(ascii), 3);
+
 // special case: zero length string
 assert.equal(Buffer.byteLength('', 'ascii'), 0);
 assert.equal(Buffer.byteLength('', 'HeX'), 0);
