MidiFile.h

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/*
 * MidiFile.h - support for exporting MIDI files
 *
 * Copyright (c) 2009 Mark Conway Wirt <emergentmusics) at (gmail . com>
 * Copyright (c) 2015 Mohamed Abdel Maksoud <mohamed at amaksoud.com>
 * Copyright (c) 2020 EmoonX
 * Copyright (c) 2026 Dalton Messmer <messmer.dalton/at/gmail.com>
 *
 * This file was originally based on the Python module MidiFile.py from MIDIUtil
 * by Mark Conway Wirt, which was later rewritten in C++ by Mohamed Abdel Maksoud.
 *
 * --------------------------------------------------------------------------
 * MIDUTIL, Copyright (c) 2009, Mark Conway Wirt
 *                        <emergentmusics) at (gmail . com>
 *
 * This software is distributed under an Open Source license, the
 * details of which follow.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 * --------------------------------------------------------------------------
 *
 */
 
#ifndef LMMS_MIDI_FILE_H
#define LMMS_MIDI_FILE_H
 
#include <cstddef>
#include <filesystem>
#include <fstream>
#include <initializer_list>
#include <span>
#include <string>
#include <vector>
 
#include "LmmsTypes.h"
#include "MidiPatch.h"
 
namespace lmms
{

class MidiFile
{
public:
    static constexpr tick_t TicksPerBeat = 128;

    static constexpr std::size_t BufferSize = 50 * 1024;
 
private:
    class Section
    {
    public:
        std::vector<std::uint8_t> m_buffer;
 
    protected:
        Section();

        void writeBytes(std::span<const std::uint8_t> bytes);

        void writeBytes(std::initializer_list<std::uint8_t> bytes);

        void writeVarLength(std::uint32_t val);

        void writeBigEndian4(std::uint32_t val);

        void writeBigEndian2(std::uint16_t val);

        virtual void writeToBuffer() {}
    };
 
public:
    class Header : public Section
    {
    public:
        explicit Header(std::size_t numTracks, tick_t ticksPerBeat = TicksPerBeat);

        void writeToBuffer() override;
 
    private:
        const std::size_t m_numTracks;

        const tick_t m_ticksPerBeat;
    };
 
private:
    struct Event
    {
        enum class Type
        {
            NoteOn, NoteOff, Tempo, BankSelectMSB, BankSelectLSB, ProgramChange, TrackName
        };
        using enum Type;
 
        Type type = Type::NoteOn;

        tick_t time = 0;

        std::uint8_t channel = 0;

        union
        {
            struct
            {
                std::uint8_t pitch;

                std::uint8_t volume;
            }
            note;

            std::uint32_t tempo = 0;

            MidiPatch patch;
        };

        // (too much trouble putting it inside union...)
        std::string trackName;

        bool operator<(const Event& b) const noexcept
        {
            if (time < b.time) { return true; }
            return (time == b.time && type > b.type);
        }
    };
 
public:
    class Track : public Section
    {
    public:
        void setChannel(std::uint8_t channel) { m_channel = channel; }

        void addNote(std::uint8_t pitch, std::uint8_t volume,
            double realTime, double duration);

        void addTempo(std::uint32_t tempo, tick_t time);

        void addPatch(MidiPatch patch, tick_t time);

        void addName(std::string name, tick_t time);

        void writeToBuffer();
 
    private:
        void addEvent(Event&& event, tick_t time);

        void writeMIDIToBuffer();

        void writeEventsToBuffer();

        void writeSingleEventToBuffer(Event& event);

        std::vector<Event> m_events;

        std::uint8_t m_channel = 0;
    };

    Header m_header;

    std::vector<Track> m_tracks;

    MidiFile(const std::filesystem::path& file, std::size_t numTracks);

    void writeAllToStream();
 
private:
    std::ofstream m_stream;
};
 
} // namespace lmms
 
#endif // LMMS_MIDI_FILE_H