Add first benchmark

Summary: Implement some very basic benchmarking infra. We need benchmarks in css-layout and I want to add something now so that others have the option to follow an example when implementing a benchmark.

Reviewed By: lucasr

Differential Revision: D3648889

fbshipit-source-id: 60b93c6e5ed027a37195a9a5d86e681e3e79a5b9

benchmarks/CSSBenchmark.h

@@ -0,0 +1,43 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#ifndef __CSS_BENCHMARK_H
+#define __CSS_BENCHMARK_H
+
+#include <time.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#define NUM_REPETITIONS 100000
+
+#define CSS_BENCHMARKS(BLOCK) \
+int main(int argc, char const *argv[]) { \
+  clock_t __start; \
+  clock_t __end; \
+  { \
+    BLOCK \
+  } \
+  return 0; \
+}
+
+#define CSS_BENCHMARK(NAME, BLOCK) \
+__start = clock(); \
+for (int __i = 0; __i < NUM_REPETITIONS; __i++) { BLOCK } \
+__end = clock(); \
+__printBenchmarkResult(NAME, __start, __end);
+
+void __printBenchmarkResult(char *name, clock_t start, clock_t end) {
+  float total = (end - start) / (double) CLOCKS_PER_SEC * 1000;
+  float mean = total / NUM_REPETITIONS;
+  printf("%s: ", name);
+  printf("%lf ms", mean);
+  printf("\n");
+}
+
+#endif