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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.Collections.Generic;
using System.Linq.Expressions;
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)
{
ParameterExpression parameter = Expression.Parameter(typeof(IMessage), "p");
Expression downcast = Expression.Convert(parameter, method.DeclaringType);
Expression call = Expression.Call(downcast, method);
Expression upcast = Expression.Convert(call, typeof(object));
return Expression.Lambda<Func<IMessage, object>>(upcast, parameter).Compile();
}
/// <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, T> CreateFuncIMessageT<T>(MethodInfo method)
{
ParameterExpression parameter = Expression.Parameter(typeof(IMessage), "p");
Expression downcast = Expression.Convert(parameter, method.DeclaringType);
Expression call = Expression.Call(downcast, method);
Expression upcast = Expression.Convert(call, typeof(T));
return Expression.Lambda<Func<IMessage, T>>(upcast, parameter).Compile();
}
/// <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)
{
ParameterExpression targetParameter = Expression.Parameter(typeof(IMessage), "target");
ParameterExpression argParameter = Expression.Parameter(typeof(object), "arg");
Expression castTarget = Expression.Convert(targetParameter, method.DeclaringType);
Expression castArgument = Expression.Convert(argParameter, method.GetParameters()[0].ParameterType);
Expression call = Expression.Call(castTarget, method, castArgument);
return Expression.Lambda<Action<IMessage, object>>(call, targetParameter, argParameter).Compile();
}
/// <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)
{
ParameterExpression targetParameter = Expression.Parameter(typeof(IMessage), "target");
Expression castTarget = Expression.Convert(targetParameter, method.DeclaringType);
Expression call = Expression.Call(castTarget, method);
return Expression.Lambda<Action<IMessage>>(call, targetParameter).Compile();
}
}
}
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