RailcomBroadcastDecoder.cxx

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#include "dcc/RailcomBroadcastDecoder.hxx"
 
#include "dcc/RailCom.hxx"
 
namespace dcc
{
 
bool RailcomBroadcastDecoder::process_packet(const dcc::Feedback &packet)
{
    if (packet.ch1Size)
    {
        return process_data(packet.ch1Data, packet.ch1Size) &&
            (packet.ch2Size == 0);
    }
    else
    {
        // No channel1 data.
        notify_empty();
        if (!packet.ch2Size)
        {
            return true; // empty packet.
        }
        return false;
    }
}
 
bool RailcomBroadcastDecoder::process_data(const uint8_t *data, unsigned size)
{
    for (unsigned i = 0; i < size; ++i)
    {
        if (railcom_decode[data[i]] == RailcomDefs::INV)
        {
            return true; // garbage.
        }
    }
    if (size < 2)
    {
        return true; // Dunno what this is.
    }
    uint8_t type = (dcc::railcom_decode[data[0]] >> 2);
    if (size == 2)
    {
        uint8_t payload = dcc::railcom_decode[data[0]] & 0x3;
        payload <<= 6;
        payload |= dcc::railcom_decode[data[1]];
        switch (type)
        {
            case dcc::RMOB_ADRLOW:
                if (currentL_ == payload)
                {
                    if (countL_ < MIN_EMPTY_COUNT)
                    {
                        countL_ += 2;
                    }
                }
                else
                {
                    currentL_ = payload;
                    countL_ = 0;
                }
                break;
            case dcc::RMOB_ADRHIGH:
                if (currentH_ == payload)
                {
                    if (countH_ < MIN_EMPTY_COUNT)
                    {
                        countH_ += 2;
                    }
                }
                else
                {
                    currentH_ = payload;
                    countH_ = 0;
                }
                break;
            default:
                return false; // This is something we don't know about.
        }
        if (countL_ >= (MIN_REPEAT_COUNT * 2) &&
            countH_ >= (MIN_REPEAT_COUNT * 2))
        {
            currentAddress_ = (uint16_t(currentH_) << 8) | currentL_;
        }
        return true;
    }
    else
    {
        return false;
    }
}
 
void RailcomBroadcastDecoder::set_occupancy(bool value)
{
    if (value)
    {
        return;
    }
    notify_empty();
}
 
void RailcomBroadcastDecoder::notify_empty()
{
    if (countH_)
    {
        --countH_;
    }
    if (countL_)
    {
        --countL_;
    }
    if ((!countH_) || (!countL_))
    {
        currentAddress_ = 0;
    }
}
 
} // namespace dcc