7 files changed, 243 insertions, 0 deletions
diff --git a/Ryujinx.Graphics.Device/AccessControl.cs b/Ryujinx.Graphics.Device/AccessControl.cs
new file mode 100644
index 00000000..02203783
--- /dev/null
+++ b/Ryujinx.Graphics.Device/AccessControl.cs
@@ -0,0 +1,10 @@
+namespace Ryujinx.Graphics.Device
+{
+    public enum AccessControl
+    {
+        None      = 0,
+        ReadOnly  = 1 << 0,
+        WriteOnly = 1 << 1,
+        ReadWrite = ReadOnly | WriteOnly
+    }
+}
diff --git a/Ryujinx.Graphics.Device/DeviceState.cs b/Ryujinx.Graphics.Device/DeviceState.cs
new file mode 100644
index 00000000..ea6942ec
--- /dev/null
+++ b/Ryujinx.Graphics.Device/DeviceState.cs
@@ -0,0 +1,124 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Reflection;
+using System.Runtime.CompilerServices;
+
+namespace Ryujinx.Graphics.Device
+{
+    public class DeviceState<TState> : IDeviceState where TState : unmanaged
+    {
+        private const int RegisterSize = sizeof(int);
+
+        public TState State;
+
+        private readonly BitArray _readableRegisters;
+        private readonly BitArray _writableRegisters;
+
+        private readonly Dictionary<int, Func<int>> _readCallbacks;
+        private readonly Dictionary<int, Action<int>> _writeCallbacks;
+
+        public DeviceState(IReadOnlyDictionary<string, RwCallback> callbacks = null)
+        {
+            int size = (Unsafe.SizeOf<TState>() + RegisterSize - 1) / RegisterSize;
+
+            _readableRegisters = new BitArray(size);
+            _writableRegisters = new BitArray(size);
+
+            _readCallbacks = new Dictionary<int, Func<int>>();
+            _writeCallbacks = new Dictionary<int, Action<int>>();
+
+            var fields = typeof(TState).GetFields();
+            int offset = 0;
+
+            for (int fieldIndex = 0; fieldIndex < fields.Length; fieldIndex++)
+            {
+                var field = fields[fieldIndex];
+                var regAttr = field.GetCustomAttributes<RegisterAttribute>(false).FirstOrDefault();
+
+                int sizeOfField = SizeCalculator.SizeOf(field.FieldType);
+
+                for (int i = 0; i < ((sizeOfField + 3) & ~3); i += 4)
+                {
+                    _readableRegisters[(offset + i) / RegisterSize] = regAttr?.AccessControl.HasFlag(AccessControl.ReadOnly)  ?? true;
+                    _writableRegisters[(offset + i) / RegisterSize] = regAttr?.AccessControl.HasFlag(AccessControl.WriteOnly) ?? true;
+                }
+
+                if (callbacks != null && callbacks.TryGetValue(field.Name, out var cb))
+                {
+                    if (cb.Read != null)
+                    {
+                        _readCallbacks.Add(offset, cb.Read);
+                    }
+
+                    if (cb.Write != null)
+                    {
+                        _writeCallbacks.Add(offset, cb.Write);
+                    }
+                }
+
+                offset += sizeOfField;
+            }
+
+            Debug.Assert(offset == Unsafe.SizeOf<TState>());
+        }
+
+        public virtual int Read(int offset)
+        {
+            if (Check(offset) && _readableRegisters[offset / RegisterSize])
+            {
+                int alignedOffset = Align(offset);
+
+                if (_readCallbacks.TryGetValue(alignedOffset, out Func<int> read))
+                {
+                    return read();
+                }
+                else
+                {
+                    return GetRef<int>(alignedOffset);
+                }
+            }
+
+            return 0;
+        }
+
+        public virtual void Write(int offset, int data)
+        {
+            if (Check(offset) && _writableRegisters[offset / RegisterSize])
+            {
+                int alignedOffset = Align(offset);
+
+                if (_writeCallbacks.TryGetValue(alignedOffset, out Action<int> write))
+                {
+                    write(data);
+                }
+                else
+                {
+                    GetRef<int>(alignedOffset) = data;
+                }
+            }
+        }
+
+        private bool Check(int offset)
+        {
+            return (uint)Align(offset) < Unsafe.SizeOf<TState>();
+        }
+
+        public ref T GetRef<T>(int offset) where T : unmanaged
+        {
+            if ((uint)(offset + Unsafe.SizeOf<T>()) > Unsafe.SizeOf<TState>())
+            {
+                throw new ArgumentOutOfRangeException(nameof(offset));
+            }
+
+            return ref Unsafe.As<TState, T>(ref Unsafe.AddByteOffset(ref State, (IntPtr)offset));
+        }
+
+        private static int Align(int offset)
+        {
+            return offset & ~(RegisterSize - 1);
+        }
+    }
+}
diff --git a/Ryujinx.Graphics.Device/IDeviceState.cs b/Ryujinx.Graphics.Device/IDeviceState.cs
new file mode 100644
index 00000000..077d69f2
--- /dev/null
+++ b/Ryujinx.Graphics.Device/IDeviceState.cs
@@ -0,0 +1,8 @@
+namespace Ryujinx.Graphics.Device
+{
+    public interface IDeviceState
+    {
+        int Read(int offset);
+        void Write(int offset, int data);
+    }
+}
diff --git a/Ryujinx.Graphics.Device/RegisterAttribute.cs b/Ryujinx.Graphics.Device/RegisterAttribute.cs
new file mode 100644
index 00000000..6e198963
--- /dev/null
+++ b/Ryujinx.Graphics.Device/RegisterAttribute.cs
@@ -0,0 +1,15 @@
+using System;
+
+namespace Ryujinx.Graphics.Device
+{
+    [AttributeUsage(AttributeTargets.Field, AllowMultiple = false)]
+    public sealed class RegisterAttribute : Attribute
+    {
+        public AccessControl AccessControl { get; }
+
+        public RegisterAttribute(AccessControl ac)
+        {
+            AccessControl = ac;
+        }
+    }
+}
diff --git a/Ryujinx.Graphics.Device/RwCallback.cs b/Ryujinx.Graphics.Device/RwCallback.cs
new file mode 100644
index 00000000..6f1c8898
--- /dev/null
+++ b/Ryujinx.Graphics.Device/RwCallback.cs
@@ -0,0 +1,16 @@
+using System;
+
+namespace Ryujinx.Graphics.Device
+{
+    public struct RwCallback
+    {
+        public Action<int> Write { get; }
+        public Func<int> Read { get; }
+
+        public RwCallback(Action<int> write, Func<int> read)
+        {
+            Write = write;
+            Read = read;
+        }
+    }
+}
diff --git a/Ryujinx.Graphics.Device/Ryujinx.Graphics.Device.csproj b/Ryujinx.Graphics.Device/Ryujinx.Graphics.Device.csproj
new file mode 100644
index 00000000..7c4ae4ca
--- /dev/null
+++ b/Ryujinx.Graphics.Device/Ryujinx.Graphics.Device.csproj
@@ -0,0 +1,7 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
+  </PropertyGroup>
+
+</Project>
diff --git a/Ryujinx.Graphics.Device/SizeCalculator.cs b/Ryujinx.Graphics.Device/SizeCalculator.cs
new file mode 100644
index 00000000..7cc48915
--- /dev/null
+++ b/Ryujinx.Graphics.Device/SizeCalculator.cs
@@ -0,0 +1,63 @@
+using System;
+using System.Reflection;
+
+namespace Ryujinx.Graphics.Device
+{
+    static class SizeCalculator
+    {
+        public static int SizeOf(Type type)
+        {
+            // Is type a enum type?
+            if (type.IsEnum)
+            {
+                type = type.GetEnumUnderlyingType();
+            }
+
+            // Is type a pointer type?
+            if (type.IsPointer || type == typeof(IntPtr) || type == typeof(UIntPtr))
+            {
+                return IntPtr.Size;
+            }
+
+            // Is type a struct type?
+            if (type.IsValueType && !type.IsPrimitive)
+            {
+                // Check if the struct has a explicit size, if so, return that.
+                if (type.StructLayoutAttribute.Size != 0)
+                {
+                    return type.StructLayoutAttribute.Size;
+                }
+
+                // Otherwise we calculate the sum of the sizes of all fields.
+                int size = 0;
+                var fields = type.GetFields(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);
+
+                for (int fieldIndex = 0; fieldIndex < fields.Length; fieldIndex++)
+                {
+                    size += SizeOf(fields[fieldIndex].FieldType);
+                }
+
+                return size;
+            }
+
+            // Primitive types.
+            return (Type.GetTypeCode(type)) switch
+            {
+                TypeCode.SByte => sizeof(sbyte),
+                TypeCode.Byte => sizeof(byte),
+                TypeCode.Int16 => sizeof(short),
+                TypeCode.UInt16 => sizeof(ushort),
+                TypeCode.Int32 => sizeof(int),
+                TypeCode.UInt32 => sizeof(uint),
+                TypeCode.Int64 => sizeof(long),
+                TypeCode.UInt64 => sizeof(ulong),
+                TypeCode.Char => sizeof(char),
+                TypeCode.Single => sizeof(float),
+                TypeCode.Double => sizeof(double),
+                TypeCode.Decimal => sizeof(decimal),
+                TypeCode.Boolean => sizeof(bool),
+                _ => throw new ArgumentException($"Length for type \"{type.Name}\" is unknown.")
+            };
+        }
+    }
+}