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// 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(); };
}
}
}
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