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//------------------------------------------------------------------------------
// <copyright file="FastDelegateCreator.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//------------------------------------------------------------------------------
namespace System.Web.Util {
using System;
using System.Reflection;
using System.Reflection.Emit;
using System.Security.Permissions;
// Helper utility to quickly create a Delegate by calling its unmanaged ctor
[SecurityPermission(SecurityAction.LinkDemand, Unrestricted = true)]
internal static class FastDelegateCreator<TDelegate> where TDelegate : class {
private static readonly Func<object, IntPtr, TDelegate> _factory = GetFactory();
// obj is the 'this' pointer (potentially null)
// method is RuntimeMethodHandle.GetFunctionPointer()
internal static TDelegate BindTo(object obj, IntPtr method) {
return _factory(obj, method);
}
// obj is the 'this' pointer (potentially null)
// method is the MethodInfo to bind to
internal static TDelegate BindTo(object obj, MethodInfo method) {
return BindTo(obj, method.MethodHandle.GetFunctionPointer());
}
// Assert needed since we'll be asked to create delegates to potentially private / protected methods
[ReflectionPermission(SecurityAction.Assert, MemberAccess = true)]
private static Func<object, IntPtr, TDelegate> GetFactory() {
// All delegates have a .ctor(object @object, IntPtr method), but since we can't call this
// directly from C# we just need to LCG it.
ConstructorInfo delegateCtor = typeof(TDelegate).GetConstructor(new Type[] { typeof(object), typeof(IntPtr) });
// Define method FastCreateDelegate_X: (object, IntPtr) -> TDelegate
DynamicMethod dynamicMethod = new DynamicMethod(
name: "FastCreateDelegate_" + typeof(TDelegate).Name,
returnType: typeof(TDelegate),
parameterTypes: new Type[] { typeof(object), typeof(IntPtr) },
owner: typeof(FastDelegateCreator<TDelegate>),
skipVisibility: true);
// return new TDelegate(obj, method);
ILGenerator ilGen = dynamicMethod.GetILGenerator();
ilGen.Emit(OpCodes.Ldarg_0); // Stack contains ('this')
ilGen.Emit(OpCodes.Ldarg_1); // Stack contains ('this', 'method')
ilGen.Emit(OpCodes.Newobj, delegateCtor); // Stack contains (delegate)
ilGen.Emit(OpCodes.Ret);
return (Func<object, IntPtr, TDelegate>)dynamicMethod.CreateDelegate(typeof(Func<object, IntPtr, TDelegate>));
}
}
}
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