voice-cat/clients/apple/VoiceCat.Mac/CoreAudioDevices.cs

using System.Runtime.InteropServices;
using Foundation;
using ObjCRuntime;
using VoiceCat.Audio;

namespace VoiceCat.Mac;

internal static class CoreAudioDevices
{
    private const string CoreAudio = "/System/Library/Frameworks/CoreAudio.framework/CoreAudio";
    private const uint SystemObject = 1;
    private const uint Devices = 0x64657623;                 // 'dev#'
    private const uint DefaultInput = 0x64496e20;            // 'dIn '
    private const uint DefaultOutput = 0x644f7574;           // 'dOut'
    private const uint StreamConfiguration = 0x736c6179;     // 'slay'
    private const uint ObjectName = 0x6c6e616d;              // 'lnam'
    private const uint ScopeGlobal = 0x676c6f62;             // 'glob'
    private const uint ScopeInput = 0x696e7074;              // 'inpt'
    private const uint ScopeOutput = 0x6f757470;             // 'outp'

    [StructLayout(LayoutKind.Sequential)]
    private struct PropertyAddress(uint selector, uint scope)
    {
        public uint Selector = selector;
        public uint Scope = scope;
        public uint Element;
    }

    [DllImport(CoreAudio)]
    private static extern int AudioObjectGetPropertyDataSize(uint objectId, ref PropertyAddress address,
        uint qualifierDataSize, nint qualifierData, out uint dataSize);

    [DllImport(CoreAudio)]
    private static extern int AudioObjectGetPropertyData(uint objectId, ref PropertyAddress address,
        uint qualifierDataSize, nint qualifierData, ref uint dataSize, nint data);

    internal static IReadOnlyList<AudioDeviceInfo> List(bool input)
    {
        uint defaultId = ReadUInt(SystemObject, input ? DefaultInput : DefaultOutput, ScopeGlobal);
        var devices = new List<AudioDeviceInfo>();
        foreach (uint id in ReadUIntArray(SystemObject, Devices, ScopeGlobal))
        {
            if (ChannelCount(id, input ? ScopeInput : ScopeOutput) == 0) continue;
            string name = ReadString(id, ObjectName, ScopeGlobal) ?? $"Core Audio device {id}";
            devices.Add(new(id.ToString(System.Globalization.CultureInfo.InvariantCulture), name, id == defaultId));
        }
        return devices.OrderByDescending(device => device.IsDefault).ThenBy(device => device.Name, StringComparer.CurrentCultureIgnoreCase).ToArray();
    }

    internal static uint ParseId(string? value)
    {
        if (!uint.TryParse(value, System.Globalization.NumberStyles.None, System.Globalization.CultureInfo.InvariantCulture, out uint id) || id == 0)
            throw new ArgumentException("The selected Core Audio device is no longer available.", nameof(value));
        return id;
    }

    private static uint ReadUInt(uint objectId, uint selector, uint scope)
    {
        var address = new PropertyAddress(selector, scope);
        uint size = sizeof(uint);
        nint memory = Marshal.AllocHGlobal(sizeof(uint));
        try { return AudioObjectGetPropertyData(objectId, ref address, 0, 0, ref size, memory) == 0 ? unchecked((uint)Marshal.ReadInt32(memory)) : 0; }
        finally { Marshal.FreeHGlobal(memory); }
    }

    private static uint[] ReadUIntArray(uint objectId, uint selector, uint scope)
    {
        var address = new PropertyAddress(selector, scope);
        if (AudioObjectGetPropertyDataSize(objectId, ref address, 0, 0, out uint size) != 0 || size < sizeof(uint)) return [];
        nint memory = Marshal.AllocHGlobal(checked((int)size));
        try
        {
            if (AudioObjectGetPropertyData(objectId, ref address, 0, 0, ref size, memory) != 0) return [];
            var result = new uint[size / sizeof(uint)];
            for (int i = 0; i < result.Length; i++) result[i] = unchecked((uint)Marshal.ReadInt32(memory, i * sizeof(uint)));
            return result;
        }
        finally { Marshal.FreeHGlobal(memory); }
    }

    private static int ChannelCount(uint deviceId, uint scope)
    {
        var address = new PropertyAddress(StreamConfiguration, scope);
        if (AudioObjectGetPropertyDataSize(deviceId, ref address, 0, 0, out uint size) != 0 || size < 8) return 0;
        nint memory = Marshal.AllocHGlobal(checked((int)size));
        try
        {
            if (AudioObjectGetPropertyData(deviceId, ref address, 0, 0, ref size, memory) != 0) return 0;
            int count = Marshal.ReadInt32(memory);
            int first = IntPtr.Size == 8 ? 8 : 4;
            int stride = IntPtr.Size == 8 ? 16 : 12;
            int channels = 0;
            for (int i = 0; i < count && first + i * stride + sizeof(uint) <= size; i++)
                channels += Marshal.ReadInt32(memory, first + i * stride);
            return channels;
        }
        finally { Marshal.FreeHGlobal(memory); }
    }

    private static string? ReadString(uint objectId, uint selector, uint scope)
    {
        var address = new PropertyAddress(selector, scope);
        uint size = checked((uint)IntPtr.Size);
        nint memory = Marshal.AllocHGlobal(IntPtr.Size);
        try
        {
            if (AudioObjectGetPropertyData(objectId, ref address, 0, 0, ref size, memory) != 0) return null;
            nint handle = Marshal.ReadIntPtr(memory);
            return handle == 0 ? null : Runtime.GetNSObject<NSString>(handle, owns: false)?.ToString();
        }
        finally { Marshal.FreeHGlobal(memory); }
    }
}