bool CopyFile()

in tools/common/file_system.cc [58:92]

• 27 lines of code
• 4 McCabe index (conditional complexity)

bool CopyFile(const std::string &src, const std::string &dest) {
#ifdef __APPLE__
  // The `copyfile` function with `COPYFILE_ALL` mode preserves permissions and
  // modification time.
  return copyfile(src.c_str(), dest.c_str(), nullptr,
                  COPYFILE_ALL | COPYFILE_CLONE) == 0;
#elif __unix__
  // On Linux, we can use `sendfile` to copy it more easily than calling
  // `read`/`write` in a loop.
  struct stat stat_buf;
  bool success = false;

  int src_fd = open(src.c_str(), O_RDONLY);
  if (src_fd) {
    fstat(src_fd, &stat_buf);

    int dest_fd = open(dest.c_str(), O_WRONLY | O_CREAT, stat_buf.st_mode);
    if (dest_fd) {
      off_t offset = 0;
      if (sendfile(dest_fd, src_fd, &offset, stat_buf.st_size) != -1) {
        struct timespec timespecs[2] = {stat_buf.st_atim, stat_buf.st_mtim};
        futimens(dest_fd, timespecs);
        success = true;
      }
      close(dest_fd);
    }
    close(src_fd);
  }
  return success;
#else
// TODO(allevato): If we want to support Windows in the future, we'll need to
// use something like `CopyFileA`.
#error Only macOS and Unix are supported at this time.
#endif
}