Method readBandwidthUsage

src/modules/network.cpp:29–83

std::ifstream does not take std::string_view as param

constexpr const char* NETDEV_FILE =
    "/proc/net/dev";  // std::ifstream does not take std::string_view as param
std::optional<std::pair<unsigned long long, unsigned long long>>
waybar::modules::Network::readBandwidthUsage() {
  std::ifstream netdev(NETDEV_FILE);
  if (!netdev) {
    spdlog::warn("Failed to open netdev file {}", NETDEV_FILE);
    return {};
  }

  std::string line;
  // skip the headers (first two lines)
  std::getline(netdev, line);
  std::getline(netdev, line);

  unsigned long long receivedBytes = 0ull;
  unsigned long long transmittedBytes = 0ull;
  while (std::getline(netdev, line)) {
    std::istringstream iss(line);

    std::string ifacename;
    iss >> ifacename;      // ifacename contains "eth0:"
    ifacename.pop_back();  // remove trailing ':'
    if (ifacename != ifname_) {
      continue;
    }

    // The rest of the line consists of whitespace separated counts divided
    // into two groups (receive and transmit). Each group has the following
    // columns: bytes, packets, errs, drop, fifo, frame, compressed, multicast
    //
    // We only care about the bytes count, so we'll just ignore the 7 other
    // columns.
    unsigned long long r = 0ull;
    unsigned long long t = 0ull;
    // Read received bytes
    iss >> r;
    // Skip all the other columns in the received group
    for (int colsToSkip = 7; colsToSkip > 0; colsToSkip--) {
      // skip whitespace between columns
      while (iss.peek() == ' ') {
        iss.ignore();
      }
      // skip the irrelevant column
      while (iss.peek() != ' ') {
        iss.ignore();
      }
    }
    // Read transmit bytes
    iss >> t;

    receivedBytes += r;
    transmittedBytes += t;
  }

  return {{receivedBytes, transmittedBytes}};
}

waybar::modules::Network::Network(const std::string& id, const Json::Value& config)
    : ALabel(config, "network", id, DEFAULT_FORMAT, 60) {