/// <summary>
/// Returns the number of bytes to read from the stream.
/// </summary>
/// <param name="state">Instance of <see cref="T:NavtelecomProtocol.SessionState" />.</param>
/// <param name="reader"><see cref="T:SharpStructures.BinaryListReader" /> linked to a FLEX message body.</param>
/// <param name="writer"><see cref="T:SharpStructures.MemoryBufferWriter" /> with data to be sent to the client.</param>
/// <param name="token">The token to monitor for cancellation requests.</param>
/// <returns>A task that represents the asynchronous operation. Contains the total number of bytes to read from the socket. Zero bytes to stop reading and send the response.</returns>
public async Task <int> GetPendingBytesAsync(SessionState state, BinaryListReader reader, MemoryBufferWriter writer, CancellationToken token)
{
switch (reader.ByteList.Count)
{
case 2:
return(13);
case 15:
reader.SetPosition(13);
return(reader.ReadUInt16() + 1);
default:
if (reader.ByteList.Last() != BinaryUtilities.GetCrc8(reader.ByteList.Take(reader.ByteList.Count - 1)))
{
throw new ArgumentException("Invalid FLEX message CRC.");
}
reader.SetPosition(4);
var result = reader.ReadByte();
var crashTime = reader.ReadUInt32();
var offset = reader.ReadUInt32();
var sizeRead = reader.ReadUInt16();
if (state.CrashInfo != null && result == 0x00 && state.CrashInfo.Timestamp == crashTime)
{
for (var i = 0; i < sizeRead; ++i)
{
state.CrashInfo.Data[offset + i] = reader.ByteList[15 + i];
}
state.CrashInfo.Offset = offset + sizeRead;
var bytesLeft = state.CrashInfo.Data.Length - state.CrashInfo.Offset;
writer.Write(CrashInformation.CrashDataQuery);
writer.Write(crashTime);
writer.Write(state.CrashInfo.Offset);
writer.Write(bytesLeft > ushort.MaxValue ? ushort.MaxValue : (ushort)bytesLeft);
writer.Write(BinaryUtilities.GetCrc8(writer.Buffer));
if (bytesLeft == 0)
{
if (_onReadyCrash != null)
{
await _onReadyCrash(state, token).ConfigureAwait(false);
}
state.CrashInfo = null;
}
}
return(0);
}
}
/// <summary>
/// Returns the number of bytes to read from the stream.
/// </summary>
/// <param name="sessionState">Instance of <see cref="T:NavtelecomProtocol.SessionState" />.</param>
/// <param name="receiveBuffer">A read-only collection of bytes received from a stream.</param>
/// <param name="sendBuffer"><see cref="T:SharpStructures.MemoryBuffer" /> with data to be sent to the client.</param>
/// <param name="token">The token to monitor for cancellation requests.</param>
/// <returns>A task that represents the asynchronous operation. Contains the total number of bytes to read from the socket. Zero bytes to stop reading and send the response.</returns>
public Task <int> GetPendingBytesAsync(SessionState sessionState, IReadOnlyList <byte> receiveBuffer, MemoryBuffer sendBuffer, CancellationToken token)
{
switch (receiveBuffer.Count)
{
case 1:
return(Task.FromResult(HeaderLength - 1));
case HeaderLength:
var reader = new BinaryListReader(receiveBuffer, true);
if (!reader.ReadBytes(HeaderPreamble.Length).Select(x => (char)x).SequenceEqual(HeaderPreamble))
{
throw new ArgumentException("NTCB header preamble does not match.");
}
sessionState.ReceiverId = reader.ReadUInt32();
sessionState.SenderId = reader.ReadUInt32();
var payloadLength = reader.ReadUInt16();
reader.ReadByte();
var headerChecksum = reader.ReadByte();
if (BinaryUtilities.GetXorSum(receiveBuffer.Take(HeaderLength - 1)) != headerChecksum)
{
throw new ArgumentException("NTCB header checksum does not match.");
}
return(Task.FromResult((int)payloadLength));
default:
if (BinaryUtilities.GetXorSum(receiveBuffer.Skip(HeaderLength)) != receiveBuffer[14])
{
throw new ArgumentException("NTCB body checksum does not match.");
}
var bodyProcessor =
_bodyProcessors.GetValueOrDefault(receiveBuffer.Skip(HeaderLength).Select(x => (char)x));
if (bodyProcessor == null)
{
throw new ArgumentException("Unknown NTCB message type.");
}
var bodyReader = new BinaryListReader(receiveBuffer, true);
bodyReader.SetPosition(HeaderLength);
sendBuffer.AllocateSpace(HeaderLength);
var writer = new MemoryBufferWriter(sendBuffer, true);
bodyProcessor.ProcessBody(sessionState, bodyReader, writer);
var responseLength = sendBuffer.Position - HeaderLength;
sendBuffer.SetPosition(0);
writer.Write(HeaderPreamble.Select(x => (byte)x).ToArray());
writer.Write(sessionState.SenderId);
writer.Write(sessionState.ReceiverId);
writer.Write((ushort)responseLength);
writer.Write(BinaryUtilities.GetXorSum(sendBuffer.Array.Skip(HeaderLength).Take(responseLength)));
writer.Write(BinaryUtilities.GetXorSum(sendBuffer.Array.Take(HeaderLength - 1)));
sendBuffer.SetPosition(responseLength + HeaderLength);
return(Task.FromResult(0));
}
}
/// <summary>
/// Processes the established client-server socket connection.
/// </summary>
/// <param name="socket">Socket connected to a client device.</param>
/// <param name="token">The token to monitor for cancellation requests.</param>
/// <returns>A task that represents the asynchronous operation.</returns>
public async Task WorkAsync(Socket socket, CancellationToken token)
{
using (var stream = new AsyncBufferedSocketStream(socket, token))
{
stream.ReadTimeout = stream.WriteTimeout = _readWriteTimeoutMs;
try
{
var state = new SessionState();
for (;;)
{
stream.ClearReceiveBuffer();
await stream.ReadToBufferAsync(1, token).ConfigureAwait(false);
var processor = _primaryOperators[stream.ReceiveBuffer[0]];
if (processor == null)
{
throw new ArgumentException($"Unknown message prefix '0x{stream.ReceiveBuffer[0]:X2}'.");
}
stream.SendBuffer.SetPosition(0);
for (;;)
{
var pendingBytes =
await
processor.GetPendingBytesAsync(state, stream.ReceiveBuffer, stream.SendBuffer, token)
.ConfigureAwait(false);
if (pendingBytes == 0)
{
break;
}
await stream.ReadToBufferAsync(pendingBytes, token).ConfigureAwait(false);
}
if (OnReadyMessage != null)
{
await OnReadyMessage(state, stream.ReceiveBuffer.ToArray(), token).ConfigureAwait(false);
}
await stream.WriteBufferToSocketAsync(token).ConfigureAwait(false);
// Workaround until crashes are implemented correctly by the devices
var crashDetected = false;
if (processor.MessageTypeIdentifier == 0x40 && stream.ReceiveBuffer.Count >= 22 &&
stream.ReceiveBuffer.Skip(16).Take(6).Select(x => (char)x).SequenceEqual("*>FLEX"))
{
crashDetected = true;
}
else if (processor.MessageTypeIdentifier == 0x7E && stream.ReceiveBuffer.Count >= 2)
{
var reader = new BinaryListReader(stream.ReceiveBuffer, true);
const int detectEvent = 0xA03B;
switch ((char)stream.ReceiveBuffer[1])
{
case 'T':
if (stream.ReceiveBuffer.Count < 12)
{
break;
}
reader.SetPosition(10);
var numType = reader.ReadUInt16();
if (numType == detectEvent)
{
crashDetected = true;
}
break;
case 'A':
if (stream.ReceiveBuffer.Count < 4)
{
break;
}
var eventCount = stream.ReceiveBuffer[2];
if (eventCount <= 0)
{
break;
}
var eventLength = (stream.ReceiveBuffer.Count - 4) / eventCount;
if (eventLength < 6)
{
break;
}
for (var i = 0; i < eventCount; ++i)
{
reader.SetPosition(7 + i * eventLength);
var eventType = reader.ReadUInt16();
if (eventType != detectEvent)
{
continue;
}
crashDetected = true;
break;
}
break;
}
}
if (crashDetected)
{
stream.SendBuffer.SetPosition(0);
new MemoryBufferWriter(stream.SendBuffer, true).Write(CrashInformation.CrashInfoQuery);
await stream.WriteBufferToSocketAsync(token).ConfigureAwait(false);
}
}
}
catch (SocketStreamException)
{
}
catch (OperationCanceledException)
{
throw;
}
catch (Exception ex)
{
string receivedBytes = null;
if (await stream.TryReadAvailableBytesAsync().ConfigureAwait(false))
{
var hex = new StringBuilder(stream.ReceiveBuffer.Count * 2);
foreach (var b in stream.ReceiveBuffer)
{
hex.Append(b.ToString("X2"));
}
receivedBytes = hex.ToString();
}
var exceptionMessage = $"Error: {ex.Message}. Receive buffer: {receivedBytes ?? "NA"}.";
throw new Exception(exceptionMessage, ex);
}
}
}