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;
    if (it == end)
        return begin;

    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;
}

}