Umbraco-CMS/src/Umbraco.Core/Dynamics/ClassFactory.cs

using System;
using System.Collections.Generic;
using System.Reflection;
using System.Reflection.Emit;
using System.Threading;

namespace Umbraco.Core.Dynamics
{
	internal class ClassFactory
	{
		public static readonly ClassFactory Instance = new ClassFactory();

		static ClassFactory() { }  // Trigger lazy initialization of static fields

		ModuleBuilder module;
		Dictionary<Signature, Type> classes;
		int classCount;
		ReaderWriterLock rwLock;

		protected ClassFactory()
		{
			AssemblyName name = new AssemblyName("DynamicClasses");
			AssemblyBuilder assembly = AppDomain.CurrentDomain.DefineDynamicAssembly(name, AssemblyBuilderAccess.Run);
#if ENABLE_LINQ_PARTIAL_TRUST
            new ReflectionPermission(PermissionState.Unrestricted).Assert();
#endif
			try
			{
				module = assembly.DefineDynamicModule("Module");
			}
			finally
			{
#if ENABLE_LINQ_PARTIAL_TRUST
                PermissionSet.RevertAssert();
#endif
			}
			classes = new Dictionary<Signature, Type>();
			rwLock = new ReaderWriterLock();
		}

		public Type GetDynamicClass(IEnumerable<DynamicProperty> properties)
		{
			rwLock.AcquireReaderLock(Timeout.Infinite);
			try
			{
				Signature signature = new Signature(properties);
				Type type;
				if (!classes.TryGetValue(signature, out type))
				{
					type = CreateDynamicClass(signature.Properties);
					classes.Add(signature, type);
				}
				return type;
			}
			finally
			{
				rwLock.ReleaseReaderLock();
			}
		}

		Type CreateDynamicClass(DynamicProperty[] properties)
		{
			LockCookie cookie = rwLock.UpgradeToWriterLock(Timeout.Infinite);
			try
			{
				string typeName = "DynamicClass" + (classCount + 1);
#if ENABLE_LINQ_PARTIAL_TRUST
                new ReflectionPermission(PermissionState.Unrestricted).Assert();
#endif
				try
				{
					TypeBuilder tb = this.module.DefineType(typeName, TypeAttributes.Class |
					                                                  TypeAttributes.Public, typeof(DynamicClass));
					FieldInfo[] fields = GenerateProperties(tb, properties);
					GenerateEquals(tb, fields);
					GenerateGetHashCode(tb, fields);
					Type result = tb.CreateType();
					classCount++;
					return result;
				}
				finally
				{
#if ENABLE_LINQ_PARTIAL_TRUST
                    PermissionSet.RevertAssert();
#endif
				}
			}
			finally
			{
				rwLock.DowngradeFromWriterLock(ref cookie);
			}
		}

		FieldInfo[] GenerateProperties(TypeBuilder tb, DynamicProperty[] properties)
		{
			FieldInfo[] fields = new FieldBuilder[properties.Length];
			for (int i = 0; i < properties.Length; i++)
			{
				DynamicProperty dp = properties[i];
				FieldBuilder fb = tb.DefineField("_" + dp.Name, dp.Type, FieldAttributes.Private);
				PropertyBuilder pb = tb.DefineProperty(dp.Name, PropertyAttributes.HasDefault, dp.Type, null);
				MethodBuilder mbGet = tb.DefineMethod("get_" + dp.Name,
				                                      MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig,
				                                      dp.Type, Type.EmptyTypes);
				ILGenerator genGet = mbGet.GetILGenerator();
				genGet.Emit(OpCodes.Ldarg_0);
				genGet.Emit(OpCodes.Ldfld, fb);
				genGet.Emit(OpCodes.Ret);
				MethodBuilder mbSet = tb.DefineMethod("set_" + dp.Name,
				                                      MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig,
				                                      null, new Type[] { dp.Type });
				ILGenerator genSet = mbSet.GetILGenerator();
				genSet.Emit(OpCodes.Ldarg_0);
				genSet.Emit(OpCodes.Ldarg_1);
				genSet.Emit(OpCodes.Stfld, fb);
				genSet.Emit(OpCodes.Ret);
				pb.SetGetMethod(mbGet);
				pb.SetSetMethod(mbSet);
				fields[i] = fb;
			}
			return fields;
		}

		void GenerateEquals(TypeBuilder tb, FieldInfo[] fields)
		{
			MethodBuilder mb = tb.DefineMethod("Equals",
			                                   MethodAttributes.Public | MethodAttributes.ReuseSlot |
			                                   MethodAttributes.Virtual | MethodAttributes.HideBySig,
			                                   typeof(bool), new Type[] { typeof(object) });
			ILGenerator gen = mb.GetILGenerator();
			LocalBuilder other = gen.DeclareLocal(tb);
			Label next = gen.DefineLabel();
			gen.Emit(OpCodes.Ldarg_1);
			gen.Emit(OpCodes.Isinst, tb);
			gen.Emit(OpCodes.Stloc, other);
			gen.Emit(OpCodes.Ldloc, other);
			gen.Emit(OpCodes.Brtrue_S, next);
			gen.Emit(OpCodes.Ldc_I4_0);
			gen.Emit(OpCodes.Ret);
			gen.MarkLabel(next);
			foreach (FieldInfo field in fields)
			{
				Type ft = field.FieldType;
				Type ct = typeof(EqualityComparer<>).MakeGenericType(ft);
				next = gen.DefineLabel();
				gen.EmitCall(OpCodes.Call, ct.GetMethod("get_Default"), null);
				gen.Emit(OpCodes.Ldarg_0);
				gen.Emit(OpCodes.Ldfld, field);
				gen.Emit(OpCodes.Ldloc, other);
				gen.Emit(OpCodes.Ldfld, field);
				gen.EmitCall(OpCodes.Callvirt, ct.GetMethod("Equals", new Type[] { ft, ft }), null);
				gen.Emit(OpCodes.Brtrue_S, next);
				gen.Emit(OpCodes.Ldc_I4_0);
				gen.Emit(OpCodes.Ret);
				gen.MarkLabel(next);
			}
			gen.Emit(OpCodes.Ldc_I4_1);
			gen.Emit(OpCodes.Ret);
		}

		void GenerateGetHashCode(TypeBuilder tb, FieldInfo[] fields)
		{
			MethodBuilder mb = tb.DefineMethod("GetHashCode",
			                                   MethodAttributes.Public | MethodAttributes.ReuseSlot |
			                                   MethodAttributes.Virtual | MethodAttributes.HideBySig,
			                                   typeof(int), Type.EmptyTypes);
			ILGenerator gen = mb.GetILGenerator();
			gen.Emit(OpCodes.Ldc_I4_0);
			foreach (FieldInfo field in fields)
			{
				Type ft = field.FieldType;
				Type ct = typeof(EqualityComparer<>).MakeGenericType(ft);
				gen.EmitCall(OpCodes.Call, ct.GetMethod("get_Default"), null);
				gen.Emit(OpCodes.Ldarg_0);
				gen.Emit(OpCodes.Ldfld, field);
				gen.EmitCall(OpCodes.Callvirt, ct.GetMethod("GetHashCode", new Type[] { ft }), null);
				gen.Emit(OpCodes.Xor);
			}
			gen.Emit(OpCodes.Ret);
		}
	}
}