compare android::Vector and std::vector

Have been wondering for a while.

Test: libutils_benchmark
--------------------------------------------------------------------
Benchmark                          Time             CPU   Iterations
--------------------------------------------------------------------
BM_fill_android_vector          24.6 ns         24.5 ns     28207074
BM_fill_std_vector              5.24 ns         5.21 ns    130675479
BM_prepend_android_vector       5783 ns         5770 ns       100000
BM_prepend_std_vector           5731 ns         5717 ns       100000

Change-Id: Ie296ce2c4395121b6a456d57421f820909418afe

libutils/Android.bp

@@ -289,3 +289,9 @@ cc_test_library {
     ],
     shared_libs: ["libutils_test_singleton1"],
 }
+
+cc_benchmark {
+    name: "libutils_benchmark",
+    srcs: ["Vector_benchmark.cpp"],
+    shared_libs: ["libutils"],
+}

libutils/Vector_benchmark.cpp

@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <benchmark/benchmark.h>
+#include <utils/Vector.h>
+#include <vector>
+
+void BM_fill_android_vector(benchmark::State& state) {
+    android::Vector<char> v;
+    while (state.KeepRunning()) {
+        v.push('A');
+    }
+}
+BENCHMARK(BM_fill_android_vector);
+
+void BM_fill_std_vector(benchmark::State& state) {
+    std::vector<char> v;
+    while (state.KeepRunning()) {
+        v.push_back('A');
+    }
+}
+BENCHMARK(BM_fill_std_vector);
+
+void BM_prepend_android_vector(benchmark::State& state) {
+    android::Vector<char> v;
+    while (state.KeepRunning()) {
+        v.insertAt('A', 0);
+    }
+}
+BENCHMARK(BM_prepend_android_vector);
+
+void BM_prepend_std_vector(benchmark::State& state) {
+    std::vector<char> v;
+    while (state.KeepRunning()) {
+        v.insert(v.begin(), 'A');
+    }
+}
+BENCHMARK(BM_prepend_std_vector);
+
+BENCHMARK_MAIN();