buffer: faster case for create buffer from empty string

When create Buffer from empty string will touch
C++ binding also.

This patch can improve edge case ~70% faster.

PR-URL: https://github.com/nodejs/node/pull/4414
Reviewed-By: Trevor Norris <trev.norris@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/lib/buffer.js b/lib/buffer.js
index 2fe13303f6..a83361cc9b 100644
--- a/lib/buffer.js
+++ b/lib/buffer.js
@@ -212,6 +212,10 @@ function fromString(string, encoding) {
     throw new TypeError('"encoding" must be a valid string encoding');
 
   var length = byteLength(string, encoding);
+
+  if (length === 0)
+    return Buffer.alloc(0);
+
   if (length >= (Buffer.poolSize >>> 1))
     return binding.createFromString(string, encoding);