MMAPIAudioStore.cs

using System;
using System.IO;
using System.Reflection;
using ManagedBass;
using ManagedBass.Midi;
using osu.Framework.Audio;
using osu.Framework.Audio.Mixing;
using osu.Framework.Audio.Track;
using osu.Framework.Logging;

public class MMAPIAudioStore : AudioCollectionManager<AdjustableAudioComponent>
{
    private readonly AudioMixer mixer;
    private int counter;

    #region Reflection

    private readonly ConstructorInfo constructor;
    private readonly FieldInfo handleField;

    #endregion

    private static int midiFont;
    private static bool midiInitialized;

    public MMAPIAudioStore(AudioManager manager, AudioMixer mixer)
    {
        this.mixer = mixer;
        constructor = typeof(TrackBass).GetConstructor(BindingFlags.NonPublic | BindingFlags.CreateInstance | BindingFlags.Instance, new[] { typeof(Stream), typeof(string), typeof(bool) })!;
        handleField = typeof(TrackBass).GetField("activeStream", BindingFlags.Instance | BindingFlags.NonPublic)!;

        if (!midiInitialized)
        {
            // midi is not initialized yet
            int result = Bass.PluginLoad("bassmidi");
            if (result == 0)
                throw new DllNotFoundException("Failed to load bassmidi plugin.");

            midiInitialized = true;
        }

        if (midiFont == 0)
        {
            // bank is not loaded yet
            midiFont = BassMidi.FontInit("S40v5.1.sf2", FontInitFlags.Unicode);
            if (midiFont == 0)
                throw new FileNotFoundException("Failed to load SF2 font.");
        }

        manager.AddItem(this);
    }

    public Track Get(Memory<sbyte> data, string contentType)
    {
        if (IsDisposed) throw new ObjectDisposedException($"Cannot use disposed {nameof(MMAPIAudioStore)}.");

        counter++;
        var stream = new MemoryStream(data.ToArray().ToUnsigned());

        var track = (TrackBass)constructor.Invoke(new object[] { stream, $"player {counter}".ToString(), false });

        mixer.Add(track);
        AddItem(track);

        bindMidiBank(track);
        return track;
    }

    private void bindMidiBank(TrackBass track)
    {
        var trackHandle = (int)handleField.GetValue(track)!;
        MidiFont mf = new MidiFont { Handle = midiFont, Preset = -1, Bank = 0 };
        var fontSet = BassMidi.StreamSetFonts(trackHandle, new[] { mf }, 1);
        if (fontSet == 0)
            Logger.Log($"Failed to set font at {track.Name}", LoggingTarget.Runtime, LogLevel.Error);
    }
}