add a performance benchmark for libziparchive

This patch adds two benchmarks that measure the performance of some
operations of libziparchive.

Both benchmarks are creating a temporary zip file containing file
names of uniformly distributed lengths.  The creation of the zip
file is not timed in the benchmarks.

- FindEntry_no_match tries to find an inexisting entry in the files
  of the zip archive, in order to force the code to examine all the
  files in the archive.

- Iterate_all_files uses the iterate function to list all the files
  in the archive.

Bug: N/A
Test: adb shell /data/ziparchive-benchmarks
Change-Id: Ibdb524ba1c5ae55caddf0416ebbc09f8b6df0021

libziparchive/.clang-format

@@ -0,0 +1 @@
+../.clang-format-2

libziparchive/Android.bp

@@ -122,3 +122,29 @@ cc_test {
         },
     },
 }
+
+// Performance benchmarks.
+cc_benchmark {
+    name: "ziparchive-benchmarks",
+    defaults: ["libziparchive_flags"],
+
+    srcs: [
+        "zip_archive_benchmark.cpp",
+    ],
+    shared_libs: [
+        "libbase",
+        "liblog",
+    ],
+
+    static_libs: [
+        "libziparchive",
+        "libz",
+        "libutils",
+    ],
+
+    target: {
+        host: {
+            cppflags: ["-Wno-unnamed-type-template-args"],
+        },
+    },
+}

libziparchive/zip_archive_benchmark.cpp

@@ -0,0 +1,87 @@
+/*
+ * Copyright (C) 2017 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 <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <iostream>
+#include <string>
+#include <tuple>
+#include <vector>
+
+#include <android-base/test_utils.h>
+#include <benchmark/benchmark.h>
+#include <ziparchive/zip_archive.h>
+#include <ziparchive/zip_archive_stream_entry.h>
+#include <ziparchive/zip_writer.h>
+
+static TemporaryFile* CreateZip() {
+  TemporaryFile* result = new TemporaryFile;
+  FILE* fp = fdopen(result->fd, "w");
+
+  ZipWriter writer(fp);
+  std::string lastName = "file";
+  for (size_t i = 0; i < 1000; i++) {
+    // Make file names longer and longer.
+    lastName = lastName + std::to_string(i);
+    writer.StartEntry(lastName.c_str(), ZipWriter::kCompress);
+    writer.WriteBytes("helo", 4);
+    writer.FinishEntry();
+  }
+  writer.Finish();
+  fclose(fp);
+
+  return result;
+}
+
+static void FindEntry_no_match(benchmark::State& state) {
+  // Create a temporary zip archive.
+  std::unique_ptr<TemporaryFile> temp_file(CreateZip());
+  ZipArchiveHandle handle;
+  ZipEntry data;
+
+  // In order to walk through all file names in the archive, look for a name
+  // that does not exist in the archive.
+  ZipString name("thisFileNameDoesNotExist");
+
+  // Start the benchmark.
+  while (state.KeepRunning()) {
+    OpenArchive(temp_file->path, &handle);
+    FindEntry(handle, name, &data);
+    CloseArchive(handle);
+  }
+}
+BENCHMARK(FindEntry_no_match);
+
+static void Iterate_all_files(benchmark::State& state) {
+  std::unique_ptr<TemporaryFile> temp_file(CreateZip());
+  ZipArchiveHandle handle;
+  void* iteration_cookie;
+  ZipEntry data;
+  ZipString name;
+
+  while (state.KeepRunning()) {
+    OpenArchive(temp_file->path, &handle);
+    StartIteration(handle, &iteration_cookie, nullptr, nullptr);
+    while (Next(iteration_cookie, &data, &name) == 0) {
+    }
+    EndIteration(iteration_cookie);
+    CloseArchive(handle);
+  }
+}
+BENCHMARK(Iterate_all_files);
+
+BENCHMARK_MAIN()