juce_UMPMidi1ToBytestreamTranslator.h

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 /*
  ==============================================================================
 
   This file is part of the JUCE library.
   Copyright (c) 2022 - Raw Material Software Limited
 
   JUCE is an open source library subject to commercial or open-source
   licensing.
 
   The code included in this file is provided under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license. Permission
   To use, copy, modify, and/or distribute this software for any purpose with or
   without fee is hereby granted provided that the above copyright notice and
   this permission notice appear in all copies.
 
   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.
 
  ==============================================================================
*/
 
#ifndef DOXYGEN
 
namespace juce::universal_midi_packets
{
 
class Midi1ToBytestreamTranslator
{
public:
    explicit Midi1ToBytestreamTranslator (int initialBufferSize)
    {
        pendingSysExData.reserve (size_t (initialBufferSize));
    }
 
    void reset()
    {
        pendingSysExData.clear();
        pendingSysExTime = 0.0;
    }
 
    template <typename MessageCallback>
    void dispatch (const View& packet, double time, MessageCallback&& callback)
    {
        const auto firstWord = *packet.data();
 
        if (! pendingSysExData.empty() && shouldPacketTerminateSysExEarly (firstWord))
            pendingSysExData.clear();
 
        switch (packet.size())
        {
            case 1:
            {
                // Utility messages don't translate to bytestream format
                if (Utils::getMessageType (firstWord) != 0x00)
                {
                    const auto message = fromUmp (PacketX1 { firstWord }, time);
                    callback (BytestreamMidiView (&message));
                }
 
                break;
            }
 
            case 2:
            {
                if (Utils::getMessageType (firstWord) == 0x3)
                    processSysEx (PacketX2 { packet[0], packet[1] }, time, callback);
 
                break;
            }
 
            case 3:  // no 3-word packets in the current spec
            case 4:  // no 4-word packets translate to bytestream format
            default:
                break;
        }
    }
 
    static MidiMessage fromUmp (const PacketX1& m, double time = 0)
    {
        const auto word = m.front();
        jassert (Utils::getNumWordsForMessageType (word) == 1);
 
        const std::array<uint8_t, 3> bytes { { uint8_t ((word >> 0x10) & 0xff),
                                               uint8_t ((word >> 0x08) & 0xff),
                                               uint8_t ((word >> 0x00) & 0xff) } };
        const auto numBytes = MidiMessage::getMessageLengthFromFirstByte (bytes.front());
        return MidiMessage (bytes.data(), numBytes, time);
    }
 
private:
    template <typename MessageCallback>
    void processSysEx (const PacketX2& packet,
                       double time,
                       MessageCallback&& callback)
    {
        switch (getSysEx7Kind (packet[0]))
        {
            case SysEx7::Kind::complete:
                startSysExMessage (time);
                pushBytes (packet);
                terminateSysExMessage (callback);
                break;
 
            case SysEx7::Kind::begin:
                startSysExMessage (time);
                pushBytes (packet);
                break;
 
            case SysEx7::Kind::continuation:
                if (pendingSysExData.empty())
                    break;
 
                pushBytes (packet);
                break;
 
            case SysEx7::Kind::end:
                if (pendingSysExData.empty())
                    break;
 
                pushBytes (packet);
                terminateSysExMessage (callback);
                break;
        }
    }
 
    void pushBytes (const PacketX2& packet)
    {
        const auto bytes = SysEx7::getDataBytes (packet);
        pendingSysExData.insert (pendingSysExData.end(),
                                 bytes.data.begin(),
                                 bytes.data.begin() + bytes.size);
    }
 
    void startSysExMessage (double time)
    {
        pendingSysExTime = time;
        pendingSysExData.push_back (std::byte { 0xf0 });
    }
 
    template <typename MessageCallback>
    void terminateSysExMessage (MessageCallback&& callback)
    {
        pendingSysExData.push_back (std::byte { 0xf7 });
        callback (BytestreamMidiView (pendingSysExData, pendingSysExTime));
        pendingSysExData.clear();
    }
 
    static bool shouldPacketTerminateSysExEarly (uint32_t firstWord)
    {
        return ! (isSysExContinuation (firstWord)
                  || isSystemRealTime (firstWord)
                  || isJROrNOP (firstWord));
    }
 
    static SysEx7::Kind getSysEx7Kind (uint32_t word)
    {
        return SysEx7::Kind ((word >> 0x14) & 0xf);
    }
 
    static bool isJROrNOP (uint32_t word)
    {
        return Utils::getMessageType (word) == 0x0;
    }
 
    static bool isSysExContinuation (uint32_t word)
    {
        if (Utils::getMessageType (word) != 0x3)
            return false;
 
        const auto kind = getSysEx7Kind (word);
        return kind == SysEx7::Kind::continuation || kind == SysEx7::Kind::end;
    }
 
    static bool isSystemRealTime (uint32_t word)
    {
        return Utils::getMessageType (word) == 0x1 && ((word >> 0x10) & 0xff) >= 0xf8;
    }
 
    std::vector<std::byte> pendingSysExData;
 
    double pendingSysExTime = 0.0;
};
 
} // namespace juce::universal_midi_packets
 
#endif