Status NewRandomAccessFile()

in util/env_windows.cc [390:435]
44 lines of code
6 McCabe index (conditional complexity)

  Status NewRandomAccessFile(const std::string& filename,
                             RandomAccessFile** result) override {
    *result = nullptr;
    DWORD desired_access = GENERIC_READ;
    DWORD share_mode = FILE_SHARE_READ;
    ScopedHandle handle =
        ::CreateFileA(filename.c_str(), desired_access, share_mode,
                      /*lpSecurityAttributes=*/nullptr, OPEN_EXISTING,
                      FILE_ATTRIBUTE_READONLY,
                      /*hTemplateFile=*/nullptr);
    if (!handle.is_valid()) {
      return WindowsError(filename, ::GetLastError());
    }
    if (!mmap_limiter_.Acquire()) {
      *result = new WindowsRandomAccessFile(filename, std::move(handle));
      return Status::OK();
    }

    LARGE_INTEGER file_size;
    Status status;
    if (!::GetFileSizeEx(handle.get(), &file_size)) {
      mmap_limiter_.Release();
      return WindowsError(filename, ::GetLastError());
    }

    ScopedHandle mapping =
        ::CreateFileMappingA(handle.get(),
                             /*security attributes=*/nullptr, PAGE_READONLY,
                             /*dwMaximumSizeHigh=*/0,
                             /*dwMaximumSizeLow=*/0,
                             /*lpName=*/nullptr);
    if (mapping.is_valid()) {
      void* mmap_base = ::MapViewOfFile(mapping.get(), FILE_MAP_READ,
                                        /*dwFileOffsetHigh=*/0,
                                        /*dwFileOffsetLow=*/0,
                                        /*dwNumberOfBytesToMap=*/0);
      if (mmap_base) {
        *result = new WindowsMmapReadableFile(
            filename, reinterpret_cast<char*>(mmap_base),
            static_cast<size_t>(file_size.QuadPart), &mmap_limiter_);
        return Status::OK();
      }
    }
    mmap_limiter_.Release();
    return WindowsError(filename, ::GetLastError());
  }