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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
#if NETFRAMEWORK || NET
using System.Collections.Generic;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Reflection;
using System.Reflection.Emit;
namespace System.Text.Json.Serialization.Metadata
{
[RequiresDynamicCode(JsonSerializer.SerializationRequiresDynamicCodeMessage)]
[RequiresUnreferencedCode(JsonSerializer.SerializationRequiresDynamicCodeMessage)]
internal sealed class ReflectionEmitMemberAccessor : MemberAccessor
{
public ReflectionEmitMemberAccessor()
{
}
public override Func<object>? CreateParameterlessConstructor(Type type, ConstructorInfo? constructorInfo)
{
Debug.Assert(type != null);
Debug.Assert(constructorInfo is null || constructorInfo.GetParameters().Length == 0);
if (type.IsAbstract)
{
return null;
}
if (constructorInfo is null && !type.IsValueType)
{
return null;
}
var dynamicMethod = new DynamicMethod(
ConstructorInfo.ConstructorName,
JsonTypeInfo.ObjectType,
Type.EmptyTypes,
typeof(ReflectionEmitMemberAccessor).Module,
skipVisibility: true);
ILGenerator generator = dynamicMethod.GetILGenerator();
if (constructorInfo is null)
{
Debug.Assert(type.IsValueType);
LocalBuilder local = generator.DeclareLocal(type);
generator.Emit(OpCodes.Ldloca_S, local);
generator.Emit(OpCodes.Initobj, type);
generator.Emit(OpCodes.Ldloc, local);
generator.Emit(OpCodes.Box, type);
}
else
{
generator.Emit(OpCodes.Newobj, constructorInfo);
if (type.IsValueType)
{
// Since C# 10 it's now possible to have parameterless constructors in structs
generator.Emit(OpCodes.Box, type);
}
}
generator.Emit(OpCodes.Ret);
return CreateDelegate<Func<object>>(dynamicMethod);
}
public override Func<object[], T> CreateParameterizedConstructor<T>(ConstructorInfo constructor) =>
CreateDelegate<Func<object[], T>>(CreateParameterizedConstructor(constructor));
private static DynamicMethod CreateParameterizedConstructor(ConstructorInfo constructor)
{
Type? type = constructor.DeclaringType;
Debug.Assert(type != null);
Debug.Assert(!type.IsAbstract);
Debug.Assert(constructor.IsPublic && !constructor.IsStatic);
ParameterInfo[] parameters = constructor.GetParameters();
int parameterCount = parameters.Length;
var dynamicMethod = new DynamicMethod(
ConstructorInfo.ConstructorName,
type,
new[] { typeof(object[]) },
typeof(ReflectionEmitMemberAccessor).Module,
skipVisibility: true);
ILGenerator generator = dynamicMethod.GetILGenerator();
// For byref parameters, we need to store values in local variables and pass addresses.
// For out parameters, we just need a default-initialized local to pass by address.
LocalBuilder?[] locals = new LocalBuilder?[parameterCount];
// Track the mapping from constructor parameter index to args[] index.
// out parameters don't have entries in args[].
int argsIndex = 0;
int[] argsIndices = new int[parameterCount];
for (int i = 0; i < parameterCount; i++)
{
if (parameters[i].IsOut)
{
argsIndices[i] = -1; // out parameters don't have an args entry
}
else
{
argsIndices[i] = argsIndex++;
}
}
for (int i = 0; i < parameterCount; i++)
{
Type paramType = parameters[i].ParameterType;
if (paramType.IsByRef)
{
// Declare a local for the underlying type.
Type elementType = paramType.GetElementType()!;
locals[i] = generator.DeclareLocal(elementType);
if (parameters[i].IsOut)
{
// For out parameters, just initialize the local to default.
// We don't load from args[] since out params aren't in the metadata.
if (elementType.IsValueType)
{
generator.Emit(OpCodes.Ldloca, locals[i]!);
generator.Emit(OpCodes.Initobj, elementType);
}
else
{
generator.Emit(OpCodes.Ldnull);
generator.Emit(OpCodes.Stloc, locals[i]!);
}
}
else
{
// Load value from object array, unbox it, and store in the local.
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Ldc_I4, argsIndices[i]);
generator.Emit(OpCodes.Ldelem_Ref);
generator.Emit(OpCodes.Unbox_Any, elementType);
generator.Emit(OpCodes.Stloc, locals[i]!);
}
}
}
// Now push all arguments onto the stack.
for (int i = 0; i < parameterCount; i++)
{
Type paramType = parameters[i].ParameterType;
if (paramType.IsByRef)
{
// Load address of the local variable.
generator.Emit(OpCodes.Ldloca, locals[i]!);
}
else
{
// Load value from object array and unbox.
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Ldc_I4, argsIndices[i]);
generator.Emit(OpCodes.Ldelem_Ref);
generator.Emit(OpCodes.Unbox_Any, paramType);
}
}
generator.Emit(OpCodes.Newobj, constructor);
generator.Emit(OpCodes.Ret);
return dynamicMethod;
}
public override JsonTypeInfo.ParameterizedConstructorDelegate<T, TArg0, TArg1, TArg2, TArg3>?
CreateParameterizedConstructor<T, TArg0, TArg1, TArg2, TArg3>(ConstructorInfo constructor) =>
CreateDelegate<JsonTypeInfo.ParameterizedConstructorDelegate<T, TArg0, TArg1, TArg2, TArg3>>(
CreateParameterizedConstructor(constructor, typeof(TArg0), typeof(TArg1), typeof(TArg2), typeof(TArg3)));
private static DynamicMethod? CreateParameterizedConstructor(ConstructorInfo constructor, Type parameterType1, Type parameterType2, Type parameterType3, Type parameterType4)
{
Type? type = constructor.DeclaringType;
Debug.Assert(type != null);
Debug.Assert(!type.IsAbstract);
Debug.Assert(!constructor.IsStatic);
ParameterInfo[] parameters = constructor.GetParameters();
int parameterCount = parameters.Length;
var dynamicMethod = new DynamicMethod(
ConstructorInfo.ConstructorName,
type,
new[] { parameterType1, parameterType2, parameterType3, parameterType4 },
typeof(ReflectionEmitMemberAccessor).Module,
skipVisibility: true);
ILGenerator generator = dynamicMethod.GetILGenerator();
// For byref parameters, we need locals because we receive values but need to pass addresses.
LocalBuilder?[] locals = new LocalBuilder?[parameterCount];
for (int index = 0; index < parameterCount; index++)
{
if (parameters[index].ParameterType.IsByRef)
{
Type elementType = parameters[index].ParameterType.GetElementType()!;
locals[index] = generator.DeclareLocal(elementType);
if (parameters[index].IsOut)
{
// For out parameters, initialize to default (the caller passes placeholder values).
if (elementType.IsValueType)
{
generator.Emit(OpCodes.Ldloca, locals[index]!);
generator.Emit(OpCodes.Initobj, elementType);
}
else
{
generator.Emit(OpCodes.Ldnull);
generator.Emit(OpCodes.Stloc, locals[index]!);
}
}
else
{
// For in/ref parameters, copy the argument value to the local.
generator.Emit(
index switch
{
0 => OpCodes.Ldarg_0,
1 => OpCodes.Ldarg_1,
2 => OpCodes.Ldarg_2,
3 => OpCodes.Ldarg_3,
_ => throw new InvalidOperationException()
});
generator.Emit(OpCodes.Stloc, locals[index]!);
}
}
}
// Now push all arguments onto the stack.
for (int index = 0; index < parameterCount; index++)
{
Debug.Assert(index <= JsonConstants.UnboxedParameterCountThreshold);
if (parameters[index].ParameterType.IsByRef)
{
// Load address of the local variable.
generator.Emit(OpCodes.Ldloca, locals[index]!);
}
else
{
// Load the argument value directly.
generator.Emit(
index switch
{
0 => OpCodes.Ldarg_0,
1 => OpCodes.Ldarg_1,
2 => OpCodes.Ldarg_2,
3 => OpCodes.Ldarg_3,
_ => throw new InvalidOperationException()
});
}
}
generator.Emit(OpCodes.Newobj, constructor);
generator.Emit(OpCodes.Ret);
return dynamicMethod;
}
public override Action<TCollection, object?> CreateAddMethodDelegate<[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods)] TCollection>() =>
CreateDelegate<Action<TCollection, object?>>(CreateAddMethodDelegate(typeof(TCollection)));
private static DynamicMethod CreateAddMethodDelegate(
[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods)] Type collectionType)
{
// We verified this won't be null when we created the converter that calls this method.
MethodInfo realMethod = (collectionType.GetMethod("Push") ?? collectionType.GetMethod("Enqueue"))!;
var dynamicMethod = new DynamicMethod(
realMethod.Name,
typeof(void),
new[] { collectionType, JsonTypeInfo.ObjectType },
typeof(ReflectionEmitMemberAccessor).Module,
skipVisibility: true);
ILGenerator generator = dynamicMethod.GetILGenerator();
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Ldarg_1);
generator.Emit(OpCodes.Callvirt, realMethod);
generator.Emit(OpCodes.Ret);
return dynamicMethod;
}
public override Func<IEnumerable<TElement>, TCollection> CreateImmutableEnumerableCreateRangeDelegate<TCollection, TElement>() =>
CreateDelegate<Func<IEnumerable<TElement>, TCollection>>(
CreateImmutableEnumerableCreateRangeDelegate(typeof(TCollection), typeof(TElement), typeof(IEnumerable<TElement>)));
private static DynamicMethod CreateImmutableEnumerableCreateRangeDelegate(Type collectionType, Type elementType, Type enumerableType)
{
MethodInfo realMethod = collectionType.GetImmutableEnumerableCreateRangeMethod(elementType);
var dynamicMethod = new DynamicMethod(
realMethod.Name,
collectionType,
new[] { enumerableType },
typeof(ReflectionEmitMemberAccessor).Module,
skipVisibility: true);
ILGenerator generator = dynamicMethod.GetILGenerator();
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Call, realMethod);
generator.Emit(OpCodes.Ret);
return dynamicMethod;
}
public override Func<IEnumerable<KeyValuePair<TKey, TValue>>, TCollection> CreateImmutableDictionaryCreateRangeDelegate<TCollection, TKey, TValue>() =>
CreateDelegate<Func<IEnumerable<KeyValuePair<TKey, TValue>>, TCollection>>(
CreateImmutableDictionaryCreateRangeDelegate(typeof(TCollection), typeof(TKey), typeof(TValue), typeof(IEnumerable<KeyValuePair<TKey, TValue>>)));
private static DynamicMethod CreateImmutableDictionaryCreateRangeDelegate(Type collectionType, Type keyType, Type valueType, Type enumerableType)
{
MethodInfo realMethod = collectionType.GetImmutableDictionaryCreateRangeMethod(keyType, valueType);
var dynamicMethod = new DynamicMethod(
realMethod.Name,
collectionType,
new[] { enumerableType },
typeof(ReflectionEmitMemberAccessor).Module,
skipVisibility: true);
ILGenerator generator = dynamicMethod.GetILGenerator();
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Call, realMethod);
generator.Emit(OpCodes.Ret);
return dynamicMethod;
}
public override Func<object, TProperty> CreatePropertyGetter<TProperty>(PropertyInfo propertyInfo) =>
CreateDelegate<Func<object, TProperty>>(CreatePropertyGetter(propertyInfo, typeof(TProperty)));
private static DynamicMethod CreatePropertyGetter(PropertyInfo propertyInfo, Type runtimePropertyType)
{
MethodInfo? realMethod = propertyInfo.GetMethod;
Debug.Assert(realMethod != null);
Type? declaringType = propertyInfo.DeclaringType;
Debug.Assert(declaringType != null);
Type declaredPropertyType = propertyInfo.PropertyType;
DynamicMethod dynamicMethod = CreateGetterMethod(propertyInfo.Name, runtimePropertyType);
ILGenerator generator = dynamicMethod.GetILGenerator();
generator.Emit(OpCodes.Ldarg_0);
if (declaringType.IsValueType)
{
generator.Emit(OpCodes.Unbox, declaringType);
generator.Emit(OpCodes.Call, realMethod);
}
else
{
generator.Emit(OpCodes.Castclass, declaringType);
generator.Emit(OpCodes.Callvirt, realMethod);
}
// declaredPropertyType: Type of the property
// runtimePropertyType: <T> of JsonConverter / JsonPropertyInfo
if (declaredPropertyType != runtimePropertyType && declaredPropertyType.IsValueType)
{
// Not supported scenario: possible if declaredPropertyType == int? and runtimePropertyType == int
// We should catch that particular case earlier in converter generation.
Debug.Assert(!runtimePropertyType.IsValueType);
generator.Emit(OpCodes.Box, declaredPropertyType);
}
generator.Emit(OpCodes.Ret);
return dynamicMethod;
}
public override Action<object, TProperty> CreatePropertySetter<TProperty>(PropertyInfo propertyInfo) =>
CreateDelegate<Action<object, TProperty>>(CreatePropertySetter(propertyInfo, typeof(TProperty)));
private static DynamicMethod CreatePropertySetter(PropertyInfo propertyInfo, Type runtimePropertyType)
{
MethodInfo? realMethod = propertyInfo.SetMethod;
Debug.Assert(realMethod != null);
Type? declaringType = propertyInfo.DeclaringType;
Debug.Assert(declaringType != null);
Type declaredPropertyType = propertyInfo.PropertyType;
DynamicMethod dynamicMethod = CreateSetterMethod(propertyInfo.Name, runtimePropertyType);
ILGenerator generator = dynamicMethod.GetILGenerator();
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(declaringType.IsValueType ? OpCodes.Unbox : OpCodes.Castclass, declaringType);
generator.Emit(OpCodes.Ldarg_1);
// declaredPropertyType: Type of the property
// runtimePropertyType: <T> of JsonConverter / JsonPropertyInfo
if (declaredPropertyType != runtimePropertyType && declaredPropertyType.IsValueType)
{
// Not supported scenario: possible if e.g. declaredPropertyType == int? and runtimePropertyType == int
// We should catch that particular case earlier in converter generation.
Debug.Assert(!runtimePropertyType.IsValueType);
generator.Emit(OpCodes.Unbox_Any, declaredPropertyType);
}
generator.Emit(declaringType.IsValueType ? OpCodes.Call : OpCodes.Callvirt, realMethod);
generator.Emit(OpCodes.Ret);
return dynamicMethod;
}
public override Func<object, TProperty> CreateFieldGetter<TProperty>(FieldInfo fieldInfo) =>
CreateDelegate<Func<object, TProperty>>(CreateFieldGetter(fieldInfo, typeof(TProperty)));
private static DynamicMethod CreateFieldGetter(FieldInfo fieldInfo, Type runtimeFieldType)
{
Type? declaringType = fieldInfo.DeclaringType;
Debug.Assert(declaringType != null);
Type declaredFieldType = fieldInfo.FieldType;
DynamicMethod dynamicMethod = CreateGetterMethod(fieldInfo.Name, runtimeFieldType);
ILGenerator generator = dynamicMethod.GetILGenerator();
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(
declaringType.IsValueType
? OpCodes.Unbox
: OpCodes.Castclass,
declaringType);
generator.Emit(OpCodes.Ldfld, fieldInfo);
// declaredFieldType: Type of the field
// runtimeFieldType: <T> of JsonConverter / JsonPropertyInfo
if (declaredFieldType.IsValueType && declaredFieldType != runtimeFieldType)
{
generator.Emit(OpCodes.Box, declaredFieldType);
}
generator.Emit(OpCodes.Ret);
return dynamicMethod;
}
public override Action<object, TProperty> CreateFieldSetter<TProperty>(FieldInfo fieldInfo) =>
CreateDelegate<Action<object, TProperty>>(CreateFieldSetter(fieldInfo, typeof(TProperty)));
private static DynamicMethod CreateFieldSetter(FieldInfo fieldInfo, Type runtimeFieldType)
{
Type? declaringType = fieldInfo.DeclaringType;
Debug.Assert(declaringType != null);
Type declaredFieldType = fieldInfo.FieldType;
DynamicMethod dynamicMethod = CreateSetterMethod(fieldInfo.Name, runtimeFieldType);
ILGenerator generator = dynamicMethod.GetILGenerator();
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(declaringType.IsValueType ? OpCodes.Unbox : OpCodes.Castclass, declaringType);
generator.Emit(OpCodes.Ldarg_1);
// declaredFieldType: Type of the field
// runtimeFieldType: <T> of JsonConverter / JsonPropertyInfo
if (declaredFieldType != runtimeFieldType && declaredFieldType.IsValueType)
{
generator.Emit(OpCodes.Unbox_Any, declaredFieldType);
}
generator.Emit(OpCodes.Stfld, fieldInfo);
generator.Emit(OpCodes.Ret);
return dynamicMethod;
}
private static DynamicMethod CreateGetterMethod(string memberName, Type memberType) =>
new DynamicMethod(
memberName + "Getter",
memberType,
new[] { JsonTypeInfo.ObjectType },
typeof(ReflectionEmitMemberAccessor).Module,
skipVisibility: true);
private static DynamicMethod CreateSetterMethod(string memberName, Type memberType) =>
new DynamicMethod(
memberName + "Setter",
typeof(void),
new[] { JsonTypeInfo.ObjectType, memberType },
typeof(ReflectionEmitMemberAccessor).Module,
skipVisibility: true);
[return: NotNullIfNotNull(nameof(method))]
private static T? CreateDelegate<T>(DynamicMethod? method) where T : Delegate =>
(T?)method?.CreateDelegate(typeof(T));
}
}
#endif
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