Create DelegateHelpers.cs

ARMeilleure/Translation/DelegateHelpers.cs

@@ -0,0 +1,141 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using System.Reflection.Emit;
+
+namespace ARMeilleure.Translation
+{
+    static class DelegateHelpers
+    {
+        private const string DelegateTypesAssemblyName = "JitDelegateTypes";
+
+        private static readonly ModuleBuilder _modBuilder;
+
+        private static readonly Dictionary<string, Type> _delegateTypesCache;
+
+        static DelegateHelpers()
+        {
+            AssemblyBuilder asmBuilder = AssemblyBuilder.DefineDynamicAssembly(new AssemblyName(DelegateTypesAssemblyName), AssemblyBuilderAccess.Run);
+
+            _modBuilder = asmBuilder.DefineDynamicModule(DelegateTypesAssemblyName);
+
+            _delegateTypesCache = new Dictionary<string, Type>();
+        }
+
+        public static Delegate GetDelegate(Type type, string name)
+        {
+            if (type == null)
+            {
+                throw new ArgumentNullException();
+            }
+
+            if (name == null)
+            {
+                throw new ArgumentNullException();
+            }
+
+            MethodInfo methodInfo = type.GetMethod(name);
+
+            return GetDelegate(methodInfo);
+        }
+
+        public static Delegate GetDelegate(Type type, string name, Type[] types)
+        {
+            if (type == null)
+            {
+                throw new ArgumentNullException();
+            }
+
+            if (name == null)
+            {
+                throw new ArgumentNullException();
+            }
+
+            if (types == null)
+            {
+                throw new ArgumentNullException();
+            }
+
+            MethodInfo methodInfo = type.GetMethod(name, types);
+
+            return GetDelegate(methodInfo);
+        }
+
+        private static Delegate GetDelegate(MethodInfo methodInfo)
+        {
+            Type[] parameters = methodInfo.GetParameters().Select(pI => pI.ParameterType).ToArray();
+            Type   returnType = methodInfo.ReturnType;
+
+            Type delegateType = GetDelegateType(parameters, returnType);
+
+            return Delegate.CreateDelegate(delegateType, methodInfo);
+        }
+
+        private static Type GetDelegateType(Type[] parameters, Type returnType)
+        {
+            string key = GetFunctionSignatureKey(parameters, returnType);
+
+            if (!_delegateTypesCache.TryGetValue(key, out Type delegateType))
+            {
+                delegateType = MakeDelegateType(parameters, returnType, key);
+
+                _delegateTypesCache.TryAdd(key, delegateType);
+            }
+
+            return delegateType;
+        }
+
+        private static string GetFunctionSignatureKey(Type[] parameters, Type returnType)
+        {
+            string sig = GetTypeName(returnType);
+
+            foreach (Type type in parameters)
+            {
+                sig += '_' + GetTypeName(type);
+            }
+
+            return sig;
+        }
+
+        private static string GetTypeName(Type type)
+        {
+            return type.FullName.Replace(".", string.Empty);
+        }
+
+        private const MethodAttributes CtorAttributes =
+            MethodAttributes.RTSpecialName |
+            MethodAttributes.HideBySig     |
+            MethodAttributes.Public;
+
+        private const TypeAttributes DelegateTypeAttributes =
+            TypeAttributes.Class     |
+            TypeAttributes.Public    |
+            TypeAttributes.Sealed    |
+            TypeAttributes.AnsiClass |
+            TypeAttributes.AutoClass;
+
+        private const MethodImplAttributes ImplAttributes =
+            MethodImplAttributes.Runtime |
+            MethodImplAttributes.Managed;
+
+        private const MethodAttributes InvokeAttributes =
+            MethodAttributes.Public    |
+            MethodAttributes.HideBySig |
+            MethodAttributes.NewSlot   |
+            MethodAttributes.Virtual;
+
+        private static readonly Type[] _delegateCtorSignature = { typeof(object), typeof(IntPtr) };
+
+        private static Type MakeDelegateType(Type[] parameters, Type returnType, string name)
+        {
+            TypeBuilder builder = _modBuilder.DefineType(name, DelegateTypeAttributes, typeof(MulticastDelegate));
+
+            builder.DefineConstructor(CtorAttributes, CallingConventions.Standard, _delegateCtorSignature).SetImplementationFlags(ImplAttributes);
+
+            builder.DefineMethod("Invoke", InvokeAttributes, returnType, parameters).SetImplementationFlags(ImplAttributes);
+
+            return builder.CreateTypeInfo();
+        }
+    }
+}