// Protocol Buffers - Google's data interchange format // Copyright 2008 Google Inc. All rights reserved. // http://github.com/jskeet/dotnet-protobufs/ // Original C++/Java/Python code: // http://code.google.com/p/protobuf/ // // Redistribution and use in source and binary forms, with or without // modification, are permitted provided that the following conditions are // met: // // * Redistributions of source code must retain the above copyright // notice, this list of conditions and the following disclaimer. // * Redistributions in binary form must reproduce the above // copyright notice, this list of conditions and the following disclaimer // in the documentation and/or other materials provided with the // distribution. // * Neither the name of Google Inc. nor the names of its // contributors may be used to endorse or promote products derived from // this software without specific prior written permission. // // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. using System; using System.Reflection; namespace Google.ProtocolBuffers.FieldAccess { /// <summary> /// The methods in this class are somewhat evil, and should not be tampered with lightly. /// Basically they allow the creation of relatively weakly typed delegates from MethodInfos /// which are more strongly typed. They do this by creating an appropriate strongly typed /// delegate from the MethodInfo, and then calling that within an anonymous method. /// Mind-bending stuff (at least to your humble narrator) but the resulting delegates are /// very fast compared with calling Invoke later on. /// </summary> internal static class ReflectionUtil { /// <summary> /// Creates a delegate which will execute the given method and then return /// the result as an object. /// </summary> public static Func<T, object> CreateUpcastDelegate<T>(MethodInfo method) { // The tricky bit is invoking CreateCreateUpcastDelegateImpl with the right type parameters MethodInfo openImpl = typeof(ReflectionUtil).GetMethod("CreateUpcastDelegateImpl"); MethodInfo closedImpl = openImpl.MakeGenericMethod(typeof(T), method.ReturnType); return (Func<T, object>) closedImpl.Invoke(null, new object[] { method }); } /// <summary> /// Method used solely for implementing CreateUpcastDelegate. Public to avoid trust issues /// in low-trust scenarios, e.g. Silverlight. /// TODO(jonskeet): Check any of this actually works in Silverlight... /// </summary> public static Func<TSource, object> CreateUpcastDelegateImpl<TSource, TResult>(MethodInfo method) { // Convert the reflection call into an open delegate, i.e. instead of calling x.Method() // we'll call getter(x). Func<TSource, TResult> getter = (Func<TSource, TResult>)Delegate.CreateDelegate(typeof(Func<TSource, TResult>), null, method); // Implicit upcast to object (within the delegate) return delegate(TSource source) { return getter(source); }; } /// <summary> /// Creates a delegate which will execute the given method after casting the parameter /// down from object to the required parameter type. /// </summary> public static Action<T, object> CreateDowncastDelegate<T>(MethodInfo method) { MethodInfo openImpl = typeof(ReflectionUtil).GetMethod("CreateDowncastDelegateImpl"); MethodInfo closedImpl = openImpl.MakeGenericMethod(typeof(T), method.GetParameters()[0].ParameterType); return (Action<T, object>) closedImpl.Invoke(null, new object[] { method }); } public static Action<TSource, object> CreateDowncastDelegateImpl<TSource, TParam>(MethodInfo method) { // Convert the reflection call into an open delegate, i.e. instead of calling x.Method(y) we'll // call Method(x, y) Action<TSource, TParam> call = (Action<TSource, TParam>) Delegate.CreateDelegate(typeof(Action<TSource, TParam>), null, method); return delegate(TSource source, object parameter) { call(source, (TParam)parameter); }; } /// <summary> /// Creates a delegate which will execute the given method after casting the parameter /// down from object to the required parameter type. /// </summary> public static Action<T, object> CreateDowncastDelegateIgnoringReturn<T>(MethodInfo method) { MethodInfo openImpl = typeof(ReflectionUtil).GetMethod("CreateDowncastDelegateIgnoringReturnImpl"); MethodInfo closedImpl = openImpl.MakeGenericMethod(typeof(T), method.GetParameters()[0].ParameterType, method.ReturnType); return (Action<T, object>)closedImpl.Invoke(null, new object[] { method }); } public static Action<TSource, object> CreateDowncastDelegateIgnoringReturnImpl<TSource, TParam, TReturn>(MethodInfo method) { // Convert the reflection call into an open delegate, i.e. instead of calling x.Method(y) we'll // call Method(x, y) Func<TSource, TParam, TReturn> call = (Func<TSource, TParam, TReturn>) Delegate.CreateDelegate(typeof(Func<TSource, TParam, TReturn>), null, method); return delegate(TSource source, object parameter) { call(source, (TParam)parameter); }; } /// <summary> /// Creates a delegate which will execute the given static method and cast the result up to IBuilder. /// </summary> public static Func<IBuilder> CreateStaticUpcastDelegate(MethodInfo method) { MethodInfo openImpl = typeof(ReflectionUtil).GetMethod("CreateStaticUpcastDelegateImpl"); MethodInfo closedImpl = openImpl.MakeGenericMethod(method.ReturnType); return (Func<IBuilder>)closedImpl.Invoke(null, new object[] { method }); } public static Func<IBuilder> CreateStaticUpcastDelegateImpl<T>(MethodInfo method) { Func<T> call = (Func<T>)Delegate.CreateDelegate(typeof(Func<T>), null, method); return delegate { return (IBuilder)call(); }; } } }