text: // Copyright 2020 The gVisor Authors.
  //
  // 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 <fcntl.h>
  #include <stdlib.h>
  #include <sys/stat.h>
  #include <unistd.h>
  
  #include "gtest/gtest.h"
  #include "benchmark/benchmark.h"
  #include "test/util/logging.h"
  #include "test/util/temp_path.h"
  #include "test/util/test_util.h"
  
  namespace gvisor {
  namespace testing {
  
  namespace {
  
  void BM_Write(benchmark::State& state) {
    auto f = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
    FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(f.path(), O_WRONLY));
  
    const int size = state.range(0);
    std::vector<char> buf(size);
    RandomizeBuffer(buf.data(), size);
  
    for (auto _ : state) {
      TEST_CHECK(PwriteFd(fd.get(), buf.data(), size, 0) == size);
    }
  
    state.SetBytesProcessed(static_cast<int64_t>(size) *
                            static_cast<int64_t>(state.iterations()));
  }
  
  BENCHMARK(BM_Write)->Range(1, 1 << 26)->UseRealTime();
  
  void BM_Append(benchmark::State& state) {
    auto file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
    auto fd = ASSERT_NO_ERRNO_AND_VALUE(Open(file.path(), O_WRONLY | O_APPEND));
  
    const char data = 'a';
    for (auto _ : state) {
      TEST_CHECK(WriteFd(fd.get(), &data, 1) == 1);
    }
  }
  
  BENCHMARK(BM_Append);
  
  }  // namespace
  
  }  // namespace testing
  }  // namespace gvisor
  