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#region Copyright notice and license
// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// 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.
#endregion
using System;
using System.Reflection;
namespace Google.Protobuf.Reflection
{
/// <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>
/// Empty Type[] used when calling GetProperty to force property instead of indexer fetching.
/// </summary>
internal static readonly Type[] EmptyTypes = new Type[0];
/// <summary>
/// Creates a delegate which will cast the argument to the appropriate method target type,
/// call the method on it, then convert the result to object.
/// </summary>
internal static Func<IMessage, object> CreateFuncIMessageObject(MethodInfo method) =>
GetReflectionHelper(method.DeclaringType, method.ReturnType).CreateFuncIMessageObject(method);
/// <summary>
/// Creates a delegate which will cast the argument to the appropriate method target type,
/// call the method on it, then convert the result to the specified type.
/// </summary>
internal static Func<IMessage, int> CreateFuncIMessageInt32(MethodInfo method) =>
GetReflectionHelper(method.DeclaringType, typeof(object)).CreateFuncIMessageInt32(method);
/// <summary>
/// Creates a delegate which will execute the given method after casting the first argument to
/// the target type of the method, and the second argument to the first parameter type of the method.
/// </summary>
internal static Action<IMessage, object> CreateActionIMessageObject(MethodInfo method) =>
GetReflectionHelper(method.DeclaringType, method.GetParameters()[0].ParameterType).CreateActionIMessageObject(method);
/// <summary>
/// Creates a delegate which will execute the given method after casting the first argument to
/// the target type of the method.
/// </summary>
internal static Action<IMessage> CreateActionIMessage(MethodInfo method) =>
GetReflectionHelper(method.DeclaringType, typeof(object)).CreateActionIMessage(method);
/// <summary>
/// Creates a reflection helper for the given type arguments. Currently these are created on demand
/// rather than cached; this will be "busy" when initially loading a message's descriptor, but after that
/// they can be garbage collected. We could cache them by type if that proves to be important, but creating
/// an object is pretty cheap.
/// </summary>
private static IReflectionHelper GetReflectionHelper(Type t1, Type t2) =>
(IReflectionHelper) Activator.CreateInstance(typeof(ReflectionHelper<,>).MakeGenericType(t1, t2));
// Non-generic interface allowing us to use an instance of ReflectionHelper<T1, T2> without statically
// knowing the types involved.
private interface IReflectionHelper
{
Func<IMessage, int> CreateFuncIMessageInt32(MethodInfo method);
Action<IMessage> CreateActionIMessage(MethodInfo method);
Func<IMessage, object> CreateFuncIMessageObject(MethodInfo method);
Action<IMessage, object> CreateActionIMessageObject(MethodInfo method);
}
private class ReflectionHelper<T1, T2> : IReflectionHelper
{
public Func<IMessage, int> CreateFuncIMessageInt32(MethodInfo method)
{
var del = (Func<T1, int>) method.CreateDelegate(typeof(Func<T1, int>));
return message => del((T1) message);
}
public Action<IMessage> CreateActionIMessage(MethodInfo method)
{
var del = (Action<T1>) method.CreateDelegate(typeof(Action<T1>));
return message => del((T1) message);
}
public Func<IMessage, object> CreateFuncIMessageObject(MethodInfo method)
{
var del = (Func<T1, T2>) method.CreateDelegate(typeof(Func<T1, T2>));
return message => del((T1) message);
}
public Action<IMessage, object> CreateActionIMessageObject(MethodInfo method)
{
var del = (Action<T1, T2>) method.CreateDelegate(typeof(Action<T1, T2>));
return (message, arg) => del((T1) message, (T2) arg);
}
}
}
}
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