std::optional StatsClient::msgSocket()

in src/oomd/StatsClient.cpp [127:177]
51 lines of code
8 McCabe index (conditional complexity)

std::optional<std::string> StatsClient::msgSocket(std::string msg) {
  std::array<char, 64> err_buf = {};
  int sockfd = ::socket(AF_UNIX, SOCK_STREAM, 0);
  if (sockfd < 0) {
    std::cerr << "Error: creating client socket: "
              << ::strerror_r(errno, err_buf.data(), err_buf.size())
              << std::endl;
    return std::nullopt;
  }
  OOMD_SCOPE_EXIT {
    if (::close(sockfd) < 0) {
      std::cerr << "Error: shutting down client socket: "
                << ::strerror_r(errno, err_buf.data(), err_buf.size())
                << std::endl;
    }
  };
  const timeval io_timeout{.tv_sec = 2, .tv_usec = 0};
  const void* time_ptr = static_cast<const void*>(&io_timeout);
  ::setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, time_ptr, sizeof io_timeout);
  ::setsockopt(sockfd, SOL_SOCKET, SO_SNDTIMEO, time_ptr, sizeof io_timeout);
  if (::connect(sockfd, (struct sockaddr*)&serv_addr_, sizeof(serv_addr_)) <
      0) {
    std::cerr << "Error: connecting to stats socket: "
              << ::strerror_r(errno, err_buf.data(), err_buf.size())
              << "\nSocket path: " << serv_addr_.sun_path << std::endl;
    return std::nullopt;
  }
  msg += '\n';
  if (Util::writeFull(sockfd, msg.c_str(), strlen(msg.c_str())) < 0) {
    std::cerr << "Error: writing to stats socket: "
              << ::strerror_r(errno, err_buf.data(), err_buf.size())
              << std::endl;
    return std::nullopt;
  }
  std::string ret = "";
  std::array<char, 512> msg_buf = {};
  while (true) {
    int n = Util::readFull(sockfd, msg_buf.data(), msg_buf.size() - 1);
    if (n < 0) {
      std::cerr << "Error: reading from stats socket: "
                << ::strerror_r(errno, err_buf.data(), err_buf.size())
                << std::endl;
      return std::nullopt;
    } else if (n == 0) {
      break;
    }
    msg_buf[n] = '\0';
    ret += std::string(msg_buf.data());
  }
  return ret;
}