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, 10 insertions, 5 deletions

diff --git a/benchmark/buffers/buffer_zero.js b/benchmark/buffers/buffer_zero.js
index 4a63695657..e624bbbcd4 100644
--- a/benchmark/buffers/buffer_zero.js
+++ b/benchmark/buffers/buffer_zero.js
@@ -3,16 +3,21 @@
 const common = require('../common.js');
 
 const bench = common.createBenchmark(main, {
-  n: [1024]
+  n: [1024],
+  type: ['buffer', 'string']
 });
 
-const zero = Buffer.alloc(0);
+const zeroBuffer = Buffer.alloc(0);
+const zeroString = '';
 
 function main(conf) {
   var n = +conf.n;
   bench.start();
-  for (let i = 0; i < n * 1024; i++) {
-    Buffer.from(zero);
-  }
+
+  if (conf.type === 'buffer')
+    for (let i = 0; i < n * 1024; i++) Buffer.from(zeroBuffer);
+  else if (conf.type === 'string')
+    for (let i = 0; i < n * 1024; i++) Buffer.from(zeroString);
+
   bench.end(n);
 }