GlobalBufferManager.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using DX11 = SlimDX.Direct3D11;
using System.Runtime.InteropServices;

namespace Rendering.HLSL
{
    public class GlobalBufferManager
    {
        public GlobalBufferManager(GXDevice dstDevice)
        {
            mDevice = dstDevice as D3D11.GXDevice11;
        }

        public T GetGlobalBuffer<T>() where T : struct
        {
            if (mGlobalBuffers.ContainsKey(typeof(T)))
                return (T)mGlobalBuffers[typeof(T)].BufferObject;

            return CreateNewBuffer<T>();
        }

        public void UpdateGlobalBuffer<T>(T newValue) where T : struct
        {
            if (mGlobalBuffers.ContainsKey(newValue.GetType()) == false)
                throw new ArgumentException("Attempted to update a buffer that does not exist. Type: " + newValue.GetType());

            mGlobalBuffers[newValue.GetType()].BufferObject = newValue;
            SlimDX.DataStream stream = new SlimDX.DataStream(Marshal.SizeOf(newValue), true, true);
            stream.Write(newValue);
            SlimDX.DataBox box = new SlimDX.DataBox(0, 0, stream);
            mDevice.ImmediateContext.UpdateSubresource(box, mGlobalBuffers[newValue.GetType()].ConstBuffer, 0);
            if (BufferChanged != null)
                BufferChanged(typeof(T), mGlobalBuffers[newValue.GetType()]);
        }

        private T CreateNewBuffer<T>() where T : struct
        {
            var layoutAttribs = (StructLayoutAttribute[])typeof(T).GetCustomAttributes(typeof(StructLayoutAttribute), false);
            if (layoutAttribs.Length == 0 || layoutAttribs[0].Value != LayoutKind.Sequential)
                throw new ArgumentException("Attempted to create a global buffer on a struct that has not the StructLayout attribute with LayoutKind.Sequential.");

            GlobalBufferEntry entry = new GlobalBufferEntry()
            {
                BufferObject = new T(),
                ConstBuffer = new DX11.Buffer(mDevice.Device, new DX11.BufferDescription()
                {
                    BindFlags = DX11.BindFlags.ConstantBuffer,
                    CpuAccessFlags = DX11.CpuAccessFlags.None,
                    OptionFlags = DX11.ResourceOptionFlags.None,
                    SizeInBytes = Marshal.SizeOf(typeof(T)),
                    StructureByteStride = 0,
                    Usage = DX11.ResourceUsage.Default
                })
            };

            mGlobalBuffers.Add(typeof(T), entry);
            return (T)entry.BufferObject;
        }

        internal event Action<Type, GlobalBufferEntry> BufferChanged;

        private class GlobalBufferEntry
        {
            public object BufferObject { get; set; }
            public DX11.Buffer ConstBuffer { get; set; }
        }

        private Dictionary<Type, GlobalBufferEntry> mGlobalBuffers = new Dictionary<Type, GlobalBufferEntry>();
        private D3D11.GXDevice11 mDevice;
    }
}