rfidreader.cp

using System;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using RescueRobotsCar.Driver.RFID;

namespace RescueRobotsCar.Services
{
    public class RfidReader
    {
        private readonly IMfRc522 _reader;
        private static readonly byte[] DefaultKeyA = new byte[] { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };

        public static RfidReader? Instance { get; private set; }

        public RfidReader(IMfRc522 reader)
        {
            _reader = reader;
        }

        internal static void SetInstance(RfidReader reader) => Instance = reader;

        public async Task<string?> ReadBlock4Async(TimeSpan timeout)
        {
            using var cts = new CancellationTokenSource(timeout);
            try
            {
                while (!cts.IsCancellationRequested)
                {
                    if (!_reader.ListenToCardIso14443TypeA(out var card, TimeSpan.FromMilliseconds(200)))
                    {
                        await Task.Delay(50, cts.Token).ConfigureAwait(false);
                        continue;
                    }

                    if (_reader.AuthenticateMifareA(4, DefaultKeyA, card.NfcId) < 0)
                    {
                        _reader.ReselectCard();
                        continue;
                    }

                    if (_reader.Read16Bytes(4, out var data) >= 0 && data != null)
                    {
                        _reader.ReselectCard();
                        int len = 16; while (len > 0 && data[len - 1] == 0) len--;
                        var s = len > 0 ? Encoding.UTF8.GetString(data, 0, len) : string.Empty;
                        if (s.Length > 5) s = s.Substring(0, 5);
                        return s;
                    }

                    _reader.ReselectCard();
                }
            }
            catch (OperationCanceledException) { }

            return null;
        }
    }
}