JSONPListParser.cs

using System;
using System.IO;
using System.Text.Json;

namespace TextMateSharp.Internal.Parser.Json
{
    public class JSONPListParser<T>
    {

        private bool theme;

        public JSONPListParser(bool theme)
        {
            this.theme = theme;
        }

        public T Parse(StreamReader contents)
        {
            PList<T> pList = new PList<T>(theme);

            var buffer = new byte[4096];

            contents.BaseStream.Read(buffer);

            JsonReaderOptions options = new JsonReaderOptions()
            {
                AllowTrailingCommas = true,
                CommentHandling = JsonCommentHandling.Skip
            };

            // We set isFinalBlock to false since we expect more data in a subsequent read from the stream.
            var reader = new Utf8JsonReader(buffer, isFinalBlock: false, state: new JsonReaderState(options));

            while (true)
            {
                if (!reader.Read())
                {
                    // Not enough of the JSON is in the buffer to complete a read.
                    if (GetMoreBytesFromStream(contents.BaseStream, buffer, ref reader) == 0)
                        break;
                }

                var nextToken = reader.TokenType;
                switch (nextToken)
                {
                    case JsonTokenType.StartArray:
                        pList.StartElement("array");
                        break;
                    case JsonTokenType.EndArray:
                        pList.EndElement("array");
                        break;
                    case JsonTokenType.StartObject:
                        pList.StartElement("dict");
                        break;
                    case JsonTokenType.EndObject:
                        pList.EndElement("dict");
                        break;
                    case JsonTokenType.PropertyName:
                        pList.StartElement("key");
                        pList.AddString(reader.GetString());
                        pList.EndElement("key");
                        break;
                    case JsonTokenType.String:
                        pList.StartElement("string");
                        pList.AddString(reader.GetString());
                        pList.EndElement("string");
                        break;
                }
            }
            return pList.GetResult();
        }

        static int GetMoreBytesFromStream(Stream stream, byte[] buffer, ref Utf8JsonReader reader)
        {
            int bytesRead;
            if (reader.BytesConsumed < buffer.Length)
            {
                ReadOnlySpan<byte> leftover = buffer.AsSpan((int)reader.BytesConsumed);

                if (leftover.Length == buffer.Length)
                {
                    Array.Resize(ref buffer, buffer.Length * 2);
                }

                leftover.CopyTo(buffer);
                bytesRead = stream.Read(buffer.AsSpan(leftover.Length));
            }
            else
            {
                bytesRead = stream.Read(buffer);
            }

            reader = new Utf8JsonReader(buffer, isFinalBlock: bytesRead == 0, reader.CurrentState);

            return bytesRead;
        }
    }
}