IListConverter.cs

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using System.Collections;
using System.Collections.Generic;
using System.Text.Json.Serialization.Metadata;
 
namespace System.Text.Json.Serialization.Converters;
 
internal sealed class IListConverter<TCollection> : JsonCollectionConverter<TCollection, object> where TCollection : IList
{
    internal override Type RuntimeType
    {
        get
        {
            if (TypeToConvert.IsAbstract || TypeToConvert.IsInterface)
            {
                return typeof(List<object>);
            }
            return TypeToConvert;
        }
    }
 
    protected override void Add(in object value, ref ReadStack state)
    {
        TCollection val = (TCollection)state.Current.ReturnValue;
        val.Add(value);
        if (base.IsValueType)
        {
            state.Current.ReturnValue = val;
        }
    }
 
    protected override void CreateCollection(ref Utf8JsonReader reader, ref ReadStack state, JsonSerializerOptions options)
    {
        JsonTypeInfo jsonTypeInfo = state.Current.JsonTypeInfo;
        if (TypeToConvert.IsInterface || TypeToConvert.IsAbstract)
        {
            if (!TypeToConvert.IsAssignableFrom(RuntimeType))
            {
                ThrowHelper.ThrowNotSupportedException_CannotPopulateCollection(TypeToConvert, ref reader, ref state);
            }
            state.Current.ReturnValue = new List<object>();
            return;
        }
        if (jsonTypeInfo.CreateObject == null)
        {
            ThrowHelper.ThrowNotSupportedException_DeserializeNoConstructor(TypeToConvert, ref reader, ref state);
        }
        TCollection val = (TCollection)jsonTypeInfo.CreateObject();
        if (val.IsReadOnly)
        {
            ThrowHelper.ThrowNotSupportedException_CannotPopulateCollection(TypeToConvert, ref reader, ref state);
        }
        state.Current.ReturnValue = val;
    }
 
    protected override bool OnWriteResume(Utf8JsonWriter writer, TCollection value, JsonSerializerOptions options, ref WriteStack state)
    {
        IList list = value;
        int i = state.Current.EnumeratorIndex;
        JsonConverter<object> elementConverter = JsonCollectionConverter<TCollection, object>.GetElementConverter(ref state);
        if (elementConverter.CanUseDirectReadOrWrite && !state.Current.NumberHandling.HasValue)
        {
            for (; i < list.Count; i++)
            {
                elementConverter.Write(writer, list[i], options);
            }
        }
        else
        {
            for (; i < list.Count; i++)
            {
                object value2 = list[i];
                if (!elementConverter.TryWrite(writer, in value2, options, ref state))
                {
                    state.Current.EnumeratorIndex = i;
                    return false;
                }
                if (ShouldFlush(writer, ref state))
                {
                    i = (state.Current.EnumeratorIndex = i + 1);
                    return false;
                }
            }
        }
        return true;
    }
}