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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.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>
/// 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 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.
/// </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 = ReflectionUtil.CreateDelegateFunc<TSource, TResult>(method);
// Implicit upcast to object (within the delegate)
return source => 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 = ReflectionUtil.CreateDelegateAction<TSource, TParam>(method);
return (source, 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 = ReflectionUtil.CreateDelegateFunc<TSource, TParam, TReturn>(method);
return delegate(TSource source, object parameter) { call(source, (TParam) parameter); };
}
internal static Func<TResult> CreateDelegateFunc<TResult>(MethodInfo method)
{
object tdelegate = Delegate.CreateDelegate(typeof(Func<TResult>), null, method);
return (Func<TResult>)tdelegate;
}
internal static Func<T, TResult> CreateDelegateFunc<T, TResult>(MethodInfo method)
{
object tdelegate = Delegate.CreateDelegate(typeof(Func<T, TResult>), null, method);
return (Func<T, TResult>)tdelegate;
}
internal static Func<T1, T2, TResult> CreateDelegateFunc<T1, T2, TResult>(MethodInfo method)
{
object tdelegate = Delegate.CreateDelegate(typeof(Func<T1, T2, TResult>), null, method);
return (Func<T1, T2, TResult>)tdelegate;
}
internal static Action<T> CreateDelegateAction<T>(MethodInfo method)
{
object tdelegate = Delegate.CreateDelegate(typeof(Action<T>), null, method);
return (Action<T>)tdelegate;
}
internal static Action<T1, T2> CreateDelegateAction<T1, T2>(MethodInfo method)
{
object tdelegate = Delegate.CreateDelegate(typeof(Action<T1, T2>), null, method);
return (Action<T1, T2>)tdelegate;
}
}
}
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