boo/lib/audiodev/MIDIDecoder.cpp

#include "boo/audiodev/MIDIDecoder.hpp"
#include "MIDICommon.hpp"
#include <memory>
#include <algorithm>

namespace boo
{

static inline uint8_t clamp7(uint8_t val) {return std::max(0, std::min(127, int(val)));}

bool MIDIDecoder::_readContinuedValue(std::vector<uint8_t>::const_iterator& it,
                                      std::vector<uint8_t>::const_iterator end,
                                      uint32_t& valOut)
{
    uint8_t a = *it++;
    valOut = a & 0x7f;

    if (a & 0x80)
    {
        if (it == end)
            return false;
        valOut <<= 7;
        a = *it++;
        valOut |= a & 0x7f;

        if (a & 0x80)
        {
            if (it == end)
                return false;
            valOut <<= 7;
            a = *it++;
            valOut |= a & 0x7f;
        }
    }

    return true;
}

std::vector<uint8_t>::const_iterator
MIDIDecoder::receiveBytes(std::vector<uint8_t>::const_iterator begin,
                          std::vector<uint8_t>::const_iterator end)
{
    std::vector<uint8_t>::const_iterator it = begin;
    while (it != end)
    {
        uint8_t a = *it++;
        uint8_t b;
        if (a & 0x80)
            m_status = a;
        else
            it--;

        if (m_status == 0xff)
        {
            /* Meta events (ignored for now) */
            if (it == end)
                return begin;
            a = *it++;

            uint32_t length;
            _readContinuedValue(it, end, length);
            it += length;
        } else
        {
            uint8_t chan = m_status & 0xf;
            switch (Status(m_status & 0xf0))
            {
            case Status::NoteOff:
            {
                if (it == end)
                    return begin;
                a = *it++;
                if (it == end)
                    return begin;
                b = *it++;
                m_out.noteOff(chan, clamp7(a), clamp7(b));
                break;
            }
            case Status::NoteOn:
            {
                if (it == end)
                    return begin;
                a = *it++;
                if (it == end)
                    return begin;
                b = *it++;
                m_out.noteOn(chan, clamp7(a), clamp7(b));
                break;
            }
            case Status::NotePressure:
            {
                if (it == end)
                    return begin;
                a = *it++;
                if (it == end)
                    return begin;
                b = *it++;
                m_out.notePressure(chan, clamp7(a), clamp7(b));
                break;
            }
            case Status::ControlChange:
            {
                if (it == end)
                    return begin;
                a = *it++;
                if (it == end)
                    return begin;
                b = *it++;
                m_out.controlChange(chan, clamp7(a), clamp7(b));
                break;
            }
            case Status::ProgramChange:
            {
                if (it == end)
                    return begin;
                a = *it++;
                m_out.programChange(chan, clamp7(a));
                break;
            }
            case Status::ChannelPressure:
            {
                if (it == end)
                    return begin;
                a = *it++;
                m_out.channelPressure(chan, clamp7(a));
                break;
            }
            case Status::PitchBend:
            {
                if (it == end)
                    return begin;
                a = *it++;
                if (it == end)
                    return begin;
                b = *it++;
                m_out.pitchBend(chan, clamp7(b) * 128 + clamp7(a));
                break;
            }
            case Status::SysEx:
            {
                switch (Status(m_status & 0xff))
                {
                case Status::SysEx:
                {
                    uint32_t len;
                    if (!_readContinuedValue(it, end, len) || end - it < len)
                        return begin;
                    m_out.sysex(&*it, len);
                    break;
                }
                case Status::TimecodeQuarterFrame:
                {
                    if (it == end)
                        return begin;
                    a = *it++;
                    m_out.timeCodeQuarterFrame(a >> 4 & 0x7, a & 0xf);
                    break;
                }
                case Status::SongPositionPointer:
                {
                    if (it == end)
                        return begin;
                    a = *it++;
                    if (it == end)
                        return begin;
                    b = *it++;
                    m_out.songPositionPointer(clamp7(b) * 128 + clamp7(a));
                    break;
                }
                case Status::SongSelect:
                {
                    if (it == end)
                        return begin;
                    a = *it++;
                    m_out.songSelect(clamp7(a));
                    break;
                }
                case Status::TuneRequest:
                    m_out.tuneRequest();
                    break;
                case Status::Start:
                    m_out.startSeq();
                    break;
                case Status::Continue:
                    m_out.continueSeq();
                    break;
                case Status::Stop:
                    m_out.stopSeq();
                    break;
                case Status::Reset:
                    m_out.reset();
                    break;
                case Status::SysExTerm:
                case Status::TimingClock:
                case Status::ActiveSensing:
                default:
                    break;
                }
                break;
            }
            default:
                break;
            }
        }
    }
    return it;
}

}