nBus-app-driver-for-esp32/nbus_app_driver.cpp

#include "nbus_app_driver.h"

NbusAppDriver::NbusAppDriver(Stream *stream_obj, uint8_t *data, int16_t size, int32_t timeout)
: _stream_obj{stream_obj}, _data{data}, _size{size}, _timeout{timeout}
{

}

void NbusAppDriver::setData(uint8_t *data, int16_t size)
{
    _data = data;
    _size = size;
}

int16_t NbusAppDriver::receiveFromMaster()
{     
    // check if timeout elapsed
    if (_checkTimeout() == 1)
    {
        _resetRxState();
        return 0;
    }

    // get incoming bytes
    int32_t in_bytes = _stream_obj->available();

    // check if empty
    if (in_bytes == 0)
    {
        return 0;
    }

    // read length
    if (_rx_size == 0)
    {
        _rx_size = _stream_obj->read();

        // check length size
        if (_rx_size < NBUS_APP_DRIVER_PAYLOAD_MIN || _rx_size > NBUS_APP_DRIVER_PAYLOAD_MAX)
        {
            _resetRxState();
            return 0;
        }

        _time0 = millis();
        in_bytes--;
    }
    
    // read payload
    if (in_bytes > 0 && _rx_index < _rx_size)
    {
        // handle overflow
        if (in_bytes + _rx_index > _size)
        {
            _resetRxState(); 
            return 0;
        }

        _rx_index += _stream_obj->readBytes(_data + _rx_index, in_bytes);
    }

    if (_rx_index >= _rx_size)
    { 
        int16_t length = _rx_index;
        _resetRxState();
        return length;
    }
    else
    {
        return 0;
    }
}

bool NbusAppDriver::_checkTimeout()
{
    if (_time0 == INT64_MAX)
    {
        return 0;
    }
    
    return millis() - _time0 > _timeout;
}

void NbusAppDriver::_resetRxState()
{
    _rx_index = 0;
    _rx_size = 0;
    _time0 = INT64_MAX;
}