From 21fd2d1e39a6a94758f6298c2da52cd46cffdfcd Mon Sep 17 00:00:00 2001 From: Jesse Plamondon-Willard Date: Fri, 15 Dec 2017 21:37:08 -0500 Subject: emit proxy classes directly to simplify crossplatform compatibility (#409) --- .../Framework/Reflection/InterfaceProxyBuilder.cs | 138 +++++++++++++++++++++ 1 file changed, 138 insertions(+) create mode 100644 src/SMAPI/Framework/Reflection/InterfaceProxyBuilder.cs (limited to 'src/SMAPI/Framework/Reflection/InterfaceProxyBuilder.cs') diff --git a/src/SMAPI/Framework/Reflection/InterfaceProxyBuilder.cs b/src/SMAPI/Framework/Reflection/InterfaceProxyBuilder.cs new file mode 100644 index 00000000..5abebc18 --- /dev/null +++ b/src/SMAPI/Framework/Reflection/InterfaceProxyBuilder.cs @@ -0,0 +1,138 @@ +using System; +using System.Collections.Generic; +using System.Linq; +using System.Reflection; +using System.Reflection.Emit; + +namespace StardewModdingAPI.Framework.Reflection +{ + /// Generates proxy classes to access mod APIs through an arbitrary interface. + internal class InterfaceProxyBuilder + { + /********* + ** Properties + *********/ + /// The CLR module in which to create proxy classes. + private readonly ModuleBuilder ModuleBuilder; + + /// The generated proxy types. + private readonly IDictionary GeneratedTypes = new Dictionary(); + + + /********* + ** Public methods + *********/ + /// Construct an instance. + public InterfaceProxyBuilder() + { + AssemblyBuilder assemblyBuilder = AppDomain.CurrentDomain.DefineDynamicAssembly(new AssemblyName($"StardewModdingAPI.Proxies, Version={this.GetType().Assembly.GetName().Version}, Culture=neutral"), AssemblyBuilderAccess.Run); + this.ModuleBuilder = assemblyBuilder.DefineDynamicModule("StardewModdingAPI.Proxies"); + } + + /// Create an API proxy. + /// The interface through which to access the API. + /// The API instance to access. + /// The unique ID of the mod consuming the API. + /// The unique ID of the mod providing the API. + public TInterface CreateProxy(object instance, string sourceModID, string targetModID) + where TInterface : class + { + // validate + if (instance == null) + throw new InvalidOperationException("Can't proxy access to a null API."); + if (!typeof(TInterface).IsInterface) + throw new InvalidOperationException("The proxy type must be an interface, not a class."); + + // get proxy type + Type targetType = instance.GetType(); + string proxyTypeName = $"StardewModdingAPI.Proxies.From<{sourceModID}_{typeof(TInterface).FullName}>_To<{targetModID}_{targetType.FullName}>"; + if (!this.GeneratedTypes.TryGetValue(proxyTypeName, out Type type)) + { + type = this.CreateProxyType(proxyTypeName, typeof(TInterface), targetType); + this.GeneratedTypes[proxyTypeName] = type; + } + + // create instance + ConstructorInfo constructor = type.GetConstructor(new[] { targetType }); + if (constructor == null) + throw new InvalidOperationException($"Couldn't find the constructor for generated proxy type '{proxyTypeName}'."); // should never happen + return (TInterface)constructor.Invoke(new[] { instance }); + } + + + /********* + ** Private methods + *********/ + /// Define a class which proxies access to a target type through an interface. + /// The name of the proxy type to generate. + /// The interface type through which to access the target. + /// The target type to access. + private Type CreateProxyType(string proxyTypeName, Type interfaceType, Type targetType) + { + // define proxy type + TypeBuilder proxyBuilder = this.ModuleBuilder.DefineType(proxyTypeName, TypeAttributes.Public | TypeAttributes.Class); + proxyBuilder.AddInterfaceImplementation(interfaceType); + + // create field to store target instance + FieldBuilder field = proxyBuilder.DefineField("__Target", targetType, FieldAttributes.Private); + + // create constructor which accepts target instance + { + ConstructorBuilder constructor = proxyBuilder.DefineConstructor(MethodAttributes.Public, CallingConventions.Standard | CallingConventions.HasThis, new[] { targetType }); + ILGenerator il = constructor.GetILGenerator(); + + il.Emit(OpCodes.Ldarg_0); // this + // ReSharper disable once AssignNullToNotNullAttribute -- never null + il.Emit(OpCodes.Call, typeof(object).GetConstructor(new Type[0])); // call base constructor + il.Emit(OpCodes.Ldarg_0); // this + il.Emit(OpCodes.Ldarg_1); // load argument + il.Emit(OpCodes.Stfld, field); // set field to loaded argument + il.Emit(OpCodes.Ret); + } + + // proxy methods + foreach (MethodInfo proxyMethod in interfaceType.GetMethods()) + { + var targetMethod = targetType.GetMethod(proxyMethod.Name, proxyMethod.GetParameters().Select(a => a.ParameterType).ToArray()); + if (targetMethod == null) + throw new InvalidOperationException($"The {interfaceType.FullName} interface defines method {proxyMethod.Name} which doesn't exist in the API."); + + this.ProxyMethod(proxyBuilder, targetMethod, field); + } + + // create type + return proxyBuilder.CreateType(); + } + + /// Define a method which proxies access to a method on the target. + /// The proxy type being generated. + /// The target method. + /// The proxy field containing the API instance. + private void ProxyMethod(TypeBuilder proxyBuilder, MethodInfo target, FieldBuilder instanceField) + { + Type[] argTypes = target.GetParameters().Select(a => a.ParameterType).ToArray(); + + // create method + MethodBuilder methodBuilder = proxyBuilder.DefineMethod(target.Name, MethodAttributes.Public | MethodAttributes.Final | MethodAttributes.Virtual); + methodBuilder.SetParameters(argTypes); + methodBuilder.SetReturnType(target.ReturnType); + + // create method body + { + ILGenerator il = methodBuilder.GetILGenerator(); + + // load target instance + il.Emit(OpCodes.Ldarg_0); + il.Emit(OpCodes.Ldfld, instanceField); + + // invoke target method on instance + for (int i = 0; i < argTypes.Length; i++) + il.Emit(OpCodes.Ldarg, i + 1); + il.Emit(OpCodes.Call, target); + + // return result + il.Emit(OpCodes.Ret); + } + } + } +} -- cgit