ln.types/text/TokenReader.cs

using System;
using System.IO;
using System.Text;
using System.Linq;
namespace ln.types.text
{
    public class TokenReader
    {
        public TextReader Reader { get; }

        public TokenReader(Stream stream)
            : this(new UnbufferedStreamReader(stream)) { }
        public TokenReader(TextReader textReader)
        {
            Reader = textReader;
        }

        public String Read(Func<char, bool> criteria)
        {
            StringBuilder stringBuilder = new StringBuilder();
            int ch;
            while (((ch = Reader.Peek()) != -1) && criteria((char)ch))
                stringBuilder.Append((char)Reader.Read());

            return stringBuilder.ToString();
        }

        public bool EndOfStream => Reader.Peek() == -1;

        public String Read(char validChar) => Read((ch) => ch == validChar);
        public String Read(char[] validChars) => Read((ch) => validChars.Contains(ch));

        public String ReadWhiteSpace() => Read((ch) => char.IsWhiteSpace(ch));
        public String ReadToken() => Read((ch) => char.IsLetterOrDigit(ch) || (ch == '_'));

        public String ReadValue() => Reader.Peek() == '"' ? ReadQuotedString() : ReadToken();

        public String ReadQuotedString()
        {
            StringBuilder stringBuilder = new StringBuilder();

            int nextCh = Reader.Peek();
            if (nextCh != -1)
            {
                if (nextCh != '"')
                    throw new FormatException("expected double quotes");
                Reader.Read();

                while (((nextCh = Reader.Read()) != -1) && (nextCh != '"'))
                {
                    if (nextCh == '\\')
                        nextCh = Reader.Read();
                    stringBuilder.Append((char)nextCh);
                }
            }

            return stringBuilder.ToString();
        }

        public String ReadPath()
        {
            StringBuilder stringBuilder = new StringBuilder();
            string token;

            if (Reader.Peek() == '/')
                stringBuilder.Append((char)Reader.Read());

            while ((token = ReadToken()).Length > 0)
            {
                stringBuilder.Append(token);

                if (Reader.Peek() == '/')
                    stringBuilder.Append((char)Reader.Read());
                else
                    break;
            }

            return stringBuilder.ToString();
        }

        class UnbufferedStreamReader : TextReader
        {
            public Stream BaseStream { get; }

            public UnbufferedStreamReader(Stream stream)
            {
                BaseStream = stream;
            }
            public override int Read() => BaseStream.ReadByte();
        }
    }
}