benchmark: refactor buffer benchmarks

Add configuration object createBenchmark object for buffer size &
iteration in buffer-base64-encode & buffer-base64-decode.js.

PR-URL: https://github.com/nodejs/node/pull/10175
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>

benchmark/buffers/buffer-base64-decode.js

@@ -2,15 +2,18 @@
 const assert = require('assert');
 const common = require('../common.js');
 
-const bench = common.createBenchmark(main, {});
+const bench = common.createBenchmark(main, {
+  n: [32],
+});
 
 function main(conf) {
+  const n = +conf.n;
   const s = 'abcd'.repeat(8 << 20);
   s.match(/./);  // Flatten string.
   assert.strictEqual(s.length % 4, 0);
   const b = Buffer.allocUnsafe(s.length / 4 * 3);
   b.write(s, 0, s.length, 'base64');
   bench.start();
-  for (var i = 0; i < 32; i += 1) b.base64Write(s, 0, s.length);
+  for (var i = 0; i < n; i += 1) b.base64Write(s, 0, s.length);
-  bench.end(32);
+  bench.end(n);
 }

benchmark/buffers/buffer-base64-encode.js

@@ -1,16 +1,20 @@
 'use strict';
 var common = require('../common.js');
 
-var bench = common.createBenchmark(main, {});
+const bench = common.createBenchmark(main, {
+  len: [64 * 1024 * 1024],
+  n: [32]
+});
 
 function main(conf) {
-  var N = 64 * 1024 * 1024;
+  const n = +conf.n;
-  var b = Buffer.allocUnsafe(N);
+  const len = +conf.len;
-  var s = '';
+  const b = Buffer.allocUnsafe(len);
-  var i;
+  let s = '';
+  let i;
   for (i = 0; i < 256; ++i) s += String.fromCharCode(i);
-  for (i = 0; i < N; i += 256) b.write(s, i, 256, 'ascii');
+  for (i = 0; i < len; i += 256) b.write(s, i, 256, 'ascii');
   bench.start();
-  for (i = 0; i < 32; ++i) b.toString('base64');
+  for (i = 0; i < n; ++i) b.toString('base64');
-  bench.end(64);
+  bench.end(n);
 }