serial_port.cpp

#include "serial_port.h"
#include "serial_exc.h"

#include <map>
#include <string.h>
#include <fcntl.h>
#include <iostream>

namespace {
    int ConvertBaudRate(int rate)
    {
        switch (rate) {
        case 110:   return B110;
        case 300:   return B300;
        case 600:   return B600;
        case 1200:  return B1200;
        case 2400:  return B2400;
        case 4800:  return B4800;
        case 9600:  return B9600;
        case 19200: return B19200;
        case 38400: return B38400;
        case 57600: return B57600;
        case 115200: return B115200;
        default:
            std::cerr << "Warning: unsupported baud rate " << rate << " defaulting to 9600" << std::endl;
            return B9600;
        }
    }

    int ConvertDataBits(int data_bits)
    {
        switch (data_bits) {
        case 5: return CS5;
        case 6: return CS6;
        case 7: return CS7;
        case 8: return CS8;
        default:
            std::cerr << "Warning: unsupported data bits count " << data_bits << " defaulting to 8" << std::endl;
            return CS8;
        }
    }
};

TSerialPort::TSerialPort(const PSerialPortSettings & settings)
    : TFileDescriptorPort(settings)
    , Settings(settings)
{
    memset(&OldTermios, 0, sizeof(termios));
}

void TSerialPort::Open()
{
    if (IsOpen())
        throw TSerialDeviceException("port already open");

    Fd = open(Settings->Device.c_str(), O_RDWR | O_NOCTTY | O_EXCL | O_NDELAY);
    if (Fd < 0)
        throw TSerialDeviceException("cannot open serial port");

    termios dev;
    memset(&dev, 0, sizeof(termios));

    auto baud_rate = ConvertBaudRate(Settings->BaudRate);
    if (cfsetospeed(&dev, baud_rate) != 0 || cfsetispeed(&dev, baud_rate) != 0) {
        auto error_code = errno;
        Close();
        throw TSerialDeviceException("cannot open serial port: error " + std::to_string(error_code) + " from cfsetospeed / cfsetispeed; baud rate is " + std::to_string(Settings->BaudRate));
    }

    if (Settings->StopBits == 1) {
        dev.c_cflag &= ~CSTOPB;
    } else {
        dev.c_cflag |= CSTOPB;
    }

    switch (Settings->Parity) {
    case 'N':
        dev.c_cflag &= ~PARENB;
        dev.c_iflag &= ~INPCK;
        break;
    case 'E':
        dev.c_cflag |= PARENB;
        dev.c_cflag &= ~PARODD;
        dev.c_iflag |= INPCK;
        break;
    case 'O':
        dev.c_cflag |= PARENB;
        dev.c_cflag |= PARODD;
        dev.c_iflag |= INPCK;
        break;
    default:
        Close();
        throw TSerialDeviceException("cannot open serial port: invalid parity value: '" + std::string(1, Settings->Parity) + "'");
    }

    dev.c_cflag = (dev.c_cflag & ~CSIZE) | ConvertDataBits(Settings->DataBits) | CREAD | CLOCAL;
    dev.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
    dev.c_iflag &= ~(IXON | IXOFF | IXANY);
    dev.c_oflag &=~ OPOST;
    dev.c_cc[VMIN] = 0;
    dev.c_cc[VTIME] = 0;

    if (tcgetattr(Fd, &OldTermios) != 0) {
        auto error_code = errno;
        Close();
        throw TSerialDeviceException("cannot open serial port: error " + std::to_string(error_code) + " from tcgetattr");
    }

    if (tcsetattr (Fd, TCSANOW, &dev) != 0) {
        auto error_code = errno;
        Close();
        throw TSerialDeviceException("cannot open serial port: error " + std::to_string(error_code) + " from tcsetattr");
    }

    SkipNoise();    // flush data from previous instance if any
}

void TSerialPort::Close()
{
    if (Base::IsOpen()) {
        tcsetattr(Fd, TCSANOW, &OldTermios);
    }
    Base::Close();
}