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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 Google.Protobuf.Compatibility;
using System;
using System.Reflection;
#if NET35
using Google.Protobuf.Compatibility;
#endif
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
{
static ReflectionUtil()
{
ForceInitialize<string>(); // Handles all reference types
ForceInitialize<int>();
ForceInitialize<long>();
ForceInitialize<uint>();
ForceInitialize<ulong>();
ForceInitialize<float>();
ForceInitialize<double>();
ForceInitialize<bool>();
ForceInitialize<int?>();
ForceInitialize<long?>();
ForceInitialize<uint?>();
ForceInitialize<ulong?>();
ForceInitialize<float?>();
ForceInitialize<double?>();
ForceInitialize<bool?>();
ForceInitialize<SampleEnum>();
SampleEnumMethod();
}
internal static void ForceInitialize<T>() => new ReflectionHelper<IMessage, T>();
/// <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 type that declares the method,
/// call the method on it, then convert the result to object.
/// </summary>
/// <param name="method">The method to create a delegate for, which must be declared in an IMessage
/// implementation.</param>
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 type that declares the method,
/// call the method on it, then convert the result to the specified type. The method is expected
/// to actually return an enum (because of where we're calling it - for oneof cases). Sometimes that
/// means we need some extra work to perform conversions.
/// </summary>
/// <param name="method">The method to create a delegate for, which must be declared in an IMessage
/// implementation.</param>
internal static Func<IMessage, int> CreateFuncIMessageInt32(MethodInfo method) =>
GetReflectionHelper(method.DeclaringType, method.ReturnType).CreateFuncIMessageInt32(method);
/// <summary>
/// Creates a delegate which will execute the given method after casting the first argument to
/// the type that declares the method, and the second argument to the first parameter type of the method.
/// </summary>
/// <param name="method">The method to create a delegate for, which must be declared in an IMessage
/// implementation.</param>
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
/// type that declares the method.
/// </summary>
/// <param name="method">The method to create a delegate for, which must be declared in an IMessage
/// implementation.</param>
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)
{
// On pleasant runtimes, we can create a Func<int> from a method returning
// an enum based on an int. That's the fast path.
if (CanConvertEnumFuncToInt32Func)
{
var del = (Func<T1, int>) method.CreateDelegate(typeof(Func<T1, int>));
return message => del((T1) message);
}
else
{
// On some runtimes (e.g. old Mono) the return type has to be exactly correct,
// so we go via boxing. Reflection is already fairly inefficient, and this is
// only used for one-of case checking, fortunately.
var del = (Func<T1, T2>) method.CreateDelegate(typeof(Func<T1, T2>));
return message => (int) (object) 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);
}
}
// Runtime compatibility checking code - see ReflectionHelper<T1, T2>.CreateFuncIMessageInt32 for
// details about why we're doing this.
// Deliberately not inside the generic type. We only want to check this once.
private static bool CanConvertEnumFuncToInt32Func { get; } = CheckCanConvertEnumFuncToInt32Func();
private static bool CheckCanConvertEnumFuncToInt32Func()
{
try
{
// Try to do the conversion using reflection, so we can see whether it's supported.
MethodInfo method = typeof(ReflectionUtil).GetMethod(nameof(SampleEnumMethod));
// If this passes, we're in a reasonable runtime.
method.CreateDelegate(typeof(Func<int>));
return true;
}
catch (ArgumentException)
{
return false;
}
}
public enum SampleEnum
{
X
}
// Public to make the reflection simpler.
public static SampleEnum SampleEnumMethod() => SampleEnum.X;
}
}
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