public void Read(CallbackRegister register, out UInt32 topic, out UInt16 revision)
{
#if DEBUG
if (null == register)
{
throw new ArgumentNullException(nameof(register));
}
#endif
lock (Sync) { // TODO: Is lock required here?
if (!IsStarted)
{
throw new InvalidOperationException("Not yet started.");
}
// Receive packet
var buffer = new Byte[Mtu];
var endpoint = Server;
var len = Socket.ReceiveFrom(buffer, ref endpoint);
Trace.WriteLineIf(len < 1, $"Strange byte count {len}.", "client-receive-warning");
// Read header
var typeCode = BitConverter.ToUInt32(buffer, 0);
topic = BitConverter.ToUInt32(buffer, 4);
revision = BitConverter.ToUInt16(buffer, 8);
// Get the head revision for the topic
if (!TopicRevisions.TryGetValue(topic, out var headRevision))
{
headRevision = UInt16.MaxValue;
}
// If the update isn't stale...
if (revision > headRevision || headRevision > UInt16.MaxValue / 4 * 3 && revision < UInt16.MaxValue / 4)
{
// Note topic head
TopicRevisions[topic] = revision;
// Read payload
var payload = new ArraySegment <Byte>(buffer, 10, len - Constants.SERVERTXHEADER_LENGTH);
// Queue acknowledgement
AcknowledgementsPending.Enqueue(new KeyValuePair <UInt32, UInt16>(topic, revision));
SendLock.Set();
// Invoke callback
register.Invoke(typeCode, payload);
}
else
{
Trace.WriteLine($"Stale update {topic}#{revision} received (head is {headRevision}). Discarded.", "client-receive"); // This occurs when packets arrive out of order
Read(register, out topic, out revision); // Read again
}
}
}
/// <summary>
/// Read a message when the type is unknown.
/// </summary>
/// <param name="register">Register of all possible message types, and a callback for each one.</param>
public void Read(CallbackRegister register)
{
Read(register, out var topic, out var revision);
}
