benchmark: add Buffer.isBuffer

benchmark/buffers/buffer-isbuffer.js

@@ -0,0 +1,39 @@
+'use strict';
+const common = require('../common');
+const { Buffer } = require('buffer');
+
+function FakeBuffer() {}
+FakeBuffer.prototype = Object.create(Buffer.prototype);
+
+// Refs: https://github.com/nodejs/node/issues/9531#issuecomment-265611061
+class ExtensibleBuffer extends Buffer {
+  constructor() {
+    super(new ArrayBuffer(0), 0, 0);
+    Object.setPrototypeOf(this, new.target.prototype);
+  }
+}
+
+const inputs = {
+  primitive: false,
+  object: {},
+  fake: new FakeBuffer(),
+  subclassed: new ExtensibleBuffer(),
+  fastbuffer: Buffer.alloc(1),
+  slowbuffer: Buffer.allocUnsafeSlow(0),
+  uint8array: new Uint8Array(1)
+};
+
+const bench = common.createBenchmark(main, {
+  type: Object.keys(inputs),
+  n: [1e7]
+});
+
+function main(conf) {
+  const n = conf.n | 0;
+  const input = inputs[conf.type];
+
+  bench.start();
+  for (var i = 0; i < n; i++)
+    Buffer.isBuffer(input);
+  bench.end(n);
+}