tls: avoid calling Buffer.byteLength multiple times

There's no reason to be calling Buffer.byteLength() twice.
Small perf improvement

Run 1:
tls/convertprotocols.js n=1     v6.2.1 = 11852,  new = 12204 ......  -2.89%
tls/convertprotocols.js n=50000 v6.2.1 = 515660, new = 570610 .....  -9.63%

Run 2:
tls/convertprotocols.js n=1     v6.2.1 = 11729,  new = 12045 ......  -2.62%
tls/convertprotocols.js n=50000 v6.2.1 = 512080, new = 637730 ..... -19.70%

PR-URL: https://github.com/nodejs/node/pull/7236
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/benchmark/tls/convertprotocols.js b/benchmark/tls/convertprotocols.js
new file mode 100644
index 0000000000..32da0fe6fd
--- /dev/null
+++ b/benchmark/tls/convertprotocols.js
@@ -0,0 +1,20 @@
+'use strict';
+
+const common = require('../common.js');
+const tls = require('tls');
+
+const bench = common.createBenchmark(main, {
+  n: [1, 50000]
+});
+
+function main(conf) {
+  const n = +conf.n;
+
+  var i = 0;
+  var m = {};
+  common.v8ForceOptimization(
+    tls.convertNPNProtocols, ['ABC', 'XYZ123', 'FOO'], m);
+  bench.start();
+  for (; i < n; i++) tls.convertNPNProtocols(['ABC', 'XYZ123', 'FOO'], m);
+  bench.end(n);
+}