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author | Jon Skeet <skeet@pobox.com> | 2008-08-14 20:38:07 +0100 |
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committer | Jon Skeet <skeet@pobox.com> | 2008-08-14 20:38:07 +0100 |
commit | 0980982095e5fc99a20b627c188d52a8b63248c7 (patch) | |
tree | 1952fd5258f2e548211e6bfb826c2579727bf509 /csharp/ProtocolBuffers/FieldAccess/ReflectionUtil.cs | |
parent | 38da52d3490a329be0407438eeddff6da65e5085 (diff) | |
download | protobuf-0980982095e5fc99a20b627c188d52a8b63248c7.tar.gz protobuf-0980982095e5fc99a20b627c188d52a8b63248c7.tar.bz2 protobuf-0980982095e5fc99a20b627c188d52a8b63248c7.zip |
Evil reflection optimisation.
Diffstat (limited to 'csharp/ProtocolBuffers/FieldAccess/ReflectionUtil.cs')
-rw-r--r-- | csharp/ProtocolBuffers/FieldAccess/ReflectionUtil.cs | 118 |
1 files changed, 118 insertions, 0 deletions
diff --git a/csharp/ProtocolBuffers/FieldAccess/ReflectionUtil.cs b/csharp/ProtocolBuffers/FieldAccess/ReflectionUtil.cs new file mode 100644 index 00000000..ca768a76 --- /dev/null +++ b/csharp/ProtocolBuffers/FieldAccess/ReflectionUtil.cs @@ -0,0 +1,118 @@ +// Protocol Buffers - Google's data interchange format +// Copyright 2008 Google Inc. +// http://code.google.com/p/protobuf/ +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. +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 GetValueDelegate<T> 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 (GetValueDelegate<T>) closedImpl.Invoke(null, new object[] { method }); + } + + delegate TResult Getter<TSource, TResult>(TSource source); + + /// <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 GetValueDelegate<TSource> 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). + Getter<TSource, TResult> getter = (Getter<TSource, TResult>)Delegate.CreateDelegate(typeof(Getter<TSource, TResult>), 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 SingleValueDelegate<T> CreateDowncastDelegate<T>(MethodInfo method) { + MethodInfo openImpl = typeof(ReflectionUtil).GetMethod("CreateDowncastDelegateImpl"); + MethodInfo closedImpl = openImpl.MakeGenericMethod(typeof(T), method.GetParameters()[0].ParameterType); + return (SingleValueDelegate<T>)closedImpl.Invoke(null, new object[] { method }); + } + + delegate void OpenSingleValueDelegate<TSource, TParam>(TSource source, TParam parameter); + + public static SingleValueDelegate<TSource> 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) + OpenSingleValueDelegate<TSource, TParam> call = (OpenSingleValueDelegate<TSource, TParam>) + Delegate.CreateDelegate(typeof(OpenSingleValueDelegate<TSource, TParam>), 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 SingleValueDelegate<T> CreateDowncastDelegateIgnoringReturn<T>(MethodInfo method) { + MethodInfo openImpl = typeof(ReflectionUtil).GetMethod("CreateDowncastDelegateIgnoringReturnImpl"); + MethodInfo closedImpl = openImpl.MakeGenericMethod(typeof(T), method.GetParameters()[0].ParameterType, method.ReturnType); + return (SingleValueDelegate<T>)closedImpl.Invoke(null, new object[] { method }); + } + + delegate TReturn OpenSingleValueDelegate<TSource, TParam, TReturn>(TSource source, TParam parameter); + + public static SingleValueDelegate<TSource> 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) + OpenSingleValueDelegate<TSource, TParam, TReturn> call = (OpenSingleValueDelegate<TSource, TParam, TReturn>) + Delegate.CreateDelegate(typeof(OpenSingleValueDelegate<TSource, TParam, TReturn>), method); + + return delegate(TSource source, object parameter) { call(source, (TParam)parameter); }; + } + + delegate T OpenCreateBuilderDelegate<T>(); + + /// <summary> + /// Creates a delegate which will execute the given static method and cast the result up to IBuilder. + /// </summary> + public static CreateBuilderDelegate CreateStaticUpcastDelegate(MethodInfo method) { + MethodInfo openImpl = typeof(ReflectionUtil).GetMethod("CreateStaticUpcastDelegateImpl"); + MethodInfo closedImpl = openImpl.MakeGenericMethod(method.ReturnType); + return (CreateBuilderDelegate) closedImpl.Invoke(null, new object[] { method }); + } + + public static CreateBuilderDelegate CreateStaticUpcastDelegateImpl<T>(MethodInfo method) { + OpenCreateBuilderDelegate<T> call = (OpenCreateBuilderDelegate<T>)Delegate.CreateDelegate(typeof(OpenCreateBuilderDelegate<T>), method); + return delegate { return (IBuilder)call(); }; + } + } +} |