SmallObjectWithParameterizedConstructorConverter.cs

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using System.Collections.Generic;
using System.Text.Json.Serialization.Metadata;
 
namespace System.Text.Json.Serialization.Converters;
 
internal class SmallObjectWithParameterizedConstructorConverter<T, TArg0, TArg1, TArg2, TArg3> : ObjectWithParameterizedConstructorConverter<T>
{
    protected override object CreateObject(ref ReadStackFrame frame)
    {
        JsonTypeInfo.ParameterizedConstructorDelegate<T, TArg0, TArg1, TArg2, TArg3> parameterizedConstructorDelegate = (JsonTypeInfo.ParameterizedConstructorDelegate<T, TArg0, TArg1, TArg2, TArg3>)frame.JsonTypeInfo.CreateObjectWithArgs;
        Arguments<TArg0, TArg1, TArg2, TArg3> arguments = (Arguments<TArg0, TArg1, TArg2, TArg3>)frame.CtorArgumentState.Arguments;
        return parameterizedConstructorDelegate(arguments.Arg0, arguments.Arg1, arguments.Arg2, arguments.Arg3);
    }
 
    protected override bool ReadAndCacheConstructorArgument(ref ReadStack state, ref Utf8JsonReader reader, JsonParameterInfo jsonParameterInfo)
    {
        Arguments<TArg0, TArg1, TArg2, TArg3> arguments = (Arguments<TArg0, TArg1, TArg2, TArg3>)state.Current.CtorArgumentState.Arguments;
        return jsonParameterInfo.ClrInfo.Position switch
        {
            0 => TryRead<TArg0>(ref state, ref reader, jsonParameterInfo, out arguments.Arg0), 
            1 => TryRead<TArg1>(ref state, ref reader, jsonParameterInfo, out arguments.Arg1), 
            2 => TryRead<TArg2>(ref state, ref reader, jsonParameterInfo, out arguments.Arg2), 
            3 => TryRead<TArg3>(ref state, ref reader, jsonParameterInfo, out arguments.Arg3), 
            _ => throw new InvalidOperationException(), 
        };
    }
 
    private bool TryRead<TArg>(ref ReadStack state, ref Utf8JsonReader reader, JsonParameterInfo jsonParameterInfo, out TArg arg)
    {
        JsonParameterInfo<TArg> jsonParameterInfo2 = (JsonParameterInfo<TArg>)jsonParameterInfo;
        JsonConverter<TArg> jsonConverter = (JsonConverter<TArg>)jsonParameterInfo.ConverterBase;
        TArg value;
        bool result = jsonConverter.TryRead(ref reader, jsonParameterInfo2.RuntimePropertyType, jsonParameterInfo2.Options, ref state, out value);
        arg = ((value == null && jsonParameterInfo.IgnoreDefaultValuesOnRead) ? ((TArg)jsonParameterInfo2.DefaultValue) : value);
        return result;
    }
 
    protected override void InitializeConstructorArgumentCaches(ref ReadStack state, JsonSerializerOptions options)
    {
        JsonTypeInfo jsonTypeInfo = state.Current.JsonTypeInfo;
        if (jsonTypeInfo.CreateObjectWithArgs == null)
        {
            jsonTypeInfo.CreateObjectWithArgs = options.MemberAccessorStrategy.CreateParameterizedConstructor<T, TArg0, TArg1, TArg2, TArg3>(base.ConstructorInfo);
        }
        Arguments<TArg0, TArg1, TArg2, TArg3> arguments = new Arguments<TArg0, TArg1, TArg2, TArg3>();
        List<KeyValuePair<string, JsonParameterInfo>> list = jsonTypeInfo.ParameterCache.List;
        for (int i = 0; i < jsonTypeInfo.ParameterCount; i++)
        {
            JsonParameterInfo value = list[i].Value;
            if (value.ShouldDeserialize)
            {
                switch (value.ClrInfo.Position)
                {
                case 0:
                    arguments.Arg0 = ((JsonParameterInfo<TArg0>)value).TypedDefaultValue;
                    break;
                case 1:
                    arguments.Arg1 = ((JsonParameterInfo<TArg1>)value).TypedDefaultValue;
                    break;
                case 2:
                    arguments.Arg2 = ((JsonParameterInfo<TArg2>)value).TypedDefaultValue;
                    break;
                case 3:
                    arguments.Arg3 = ((JsonParameterInfo<TArg3>)value).TypedDefaultValue;
                    break;
                default:
                    throw new InvalidOperationException();
                }
            }
        }
        state.Current.CtorArgumentState.Arguments = arguments;
    }
}