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Commit a6633d77 authored by Yurii Zubrytskyi's avatar Yurii Zubrytskyi
Browse files

[zip] Save 1 malloc and memset for each added file in ZipWriter 

+ add a benchmark for the function.

This change speeds up the function by about 3%: 910ns->880ns

Change-Id: I33c8c31de18d10eb38f109917ecbcbdda45b4034
parent 2b283118

libziparchive/zip_archive_benchmark.cpp

+25 −2
Original line number Diff line number Diff line
@@ -58,7 +58,7 @@ static void FindEntry_no_match(benchmark::State& state) { 
  std::string_view name("thisFileNameDoesNotExist");



  // Start the benchmark.

  while (state.KeepRunning()) {

  for (auto _ : state) {

    OpenArchive(temp_file->path, &handle);

    FindEntry(handle, name, &data);

    CloseArchive(handle);
@@ -73,7 +73,7 @@ static void Iterate_all_files(benchmark::State& state) { 
  ZipEntry data;

  std::string name;



  while (state.KeepRunning()) {

  for (auto _ : state) {

    OpenArchive(temp_file->path, &handle);

    StartIteration(handle, &iteration_cookie);

    while (Next(iteration_cookie, &data, &name) == 0) {
@@ -84,4 +84,27 @@ static void Iterate_all_files(benchmark::State& state) { 
}

BENCHMARK(Iterate_all_files);



static void StartAlignedEntry(benchmark::State& state) {

  TemporaryFile file;

  FILE* fp = fdopen(file.fd, "w");



  ZipWriter writer(fp);



  auto alignment = uint32_t(state.range(0));

  std::string name = "name";

  int counter = 0;

  for (auto _ : state) {

    writer.StartAlignedEntry(name + std::to_string(counter++), 0, alignment);

    state.PauseTiming();

    writer.WriteBytes("hola", 4);

    writer.FinishEntry();

    state.ResumeTiming();

  }



  writer.Finish();

  fclose(fp);

}

BENCHMARK(StartAlignedEntry)->Arg(2)->Arg(16)->Arg(1024)->Arg(4096);





BENCHMARK_MAIN();

libziparchive/zip_writer.cc

+14 −3
Original line number Diff line number Diff line
@@ -247,13 +247,24 @@ int32_t ZipWriter::StartAlignedEntryWithTime(std::string_view path, size_t flags 
  ExtractTimeAndDate(time, &file_entry.last_mod_time, &file_entry.last_mod_date);



  off_t offset = current_offset_ + sizeof(LocalFileHeader) + file_entry.path.size();

  std::vector<char> zero_padding;

  // prepare a pre-zeroed memory page in case when we need to pad some aligned data.

  static constexpr auto kPageSize = 4096;

  static constexpr char kSmallZeroPadding[kPageSize] = {};

  // use this buffer if our preallocated one is too small

  std::vector<char> zero_padding_big;

  const char* zero_padding = nullptr;



  if (alignment != 0 && (offset & (alignment - 1))) {

    // Pad the extra field so the data will be aligned.

    uint16_t padding = static_cast<uint16_t>(alignment - (offset % alignment));

    file_entry.padding_length = padding;

    offset += padding;

    zero_padding.resize(padding, 0);

    if (padding <= std::size(kSmallZeroPadding)) {

        zero_padding = kSmallZeroPadding;

    } else {

        zero_padding_big.resize(padding, 0);

        zero_padding = zero_padding_big.data();

    }

  }



  LocalFileHeader header = {};
@@ -269,7 +280,7 @@ int32_t ZipWriter::StartAlignedEntryWithTime(std::string_view path, size_t flags 
    return HandleError(kIoError);

  }



  if (file_entry.padding_length != 0 && fwrite(zero_padding.data(), 1, file_entry.padding_length,

  if (file_entry.padding_length != 0 && fwrite(zero_padding, 1, file_entry.padding_length,

                                               file_) != file_entry.padding_length) {

    return HandleError(kIoError);

  }