private async Task WriteBlocksAsync()
{
var token = CancellationTokenSource.Token;
try
{
while (!token.IsCancellationRequested)
{
await _writerEvent.WaitAsync(token);
while (_writer.Length > BlockSize || (EndOfStream && _writer.Length > 0))
{
var message = Context.Request.Clone();
// Reset the message Id so it's set by CoapClient
message.Id = 0;
message.Options.Add(new Options.Block1(_writeBlockNumber, BlockSizeInternal, _writer.Length > BlockSizeInternal));
message.Payload = new byte[_writer.Length < BlockSizeInternal ? _writer.Length : BlockSizeInternal];
_writer.Peek(message.Payload, 0, BlockSizeInternal);
Context.MessageId = await Context.Client.SendAsync(message, token);
// Keep the response in the queue in case the Applciation needs it.
var result = await Context.Client.GetResponseAsync(Context.MessageId, token);
if (EndOfStream)
{
Context.Response = result;
}
if (result.Code.IsSuccess())
{
_writer.AdvanceQueue(message.Payload.Length);
_writeBlockNumber++;
var block = result.Options.Get <Options.Block1>();
var blockDelta = block.BlockSize - BlockSizeInternal;
// Only update the size if it's smaller
if (blockDelta < 0)
{
BlockSizeInternal += blockDelta;
_writeBlockNumber -= blockDelta / BlockSizeInternal;
}
else if (blockDelta > 0)
{
throw new CoapBlockException($"Remote endpoint requested to increase blocksize from {BlockSizeInternal} to {BlockSizeInternal + blockDelta}");
}
}
else if (result.Code.IsClientError() || result.Code.IsServerError())
{
if (_writeBlockNumber == 0 && result.Code == CoapMessageCode.RequestEntityTooLarge && BlockSizeInternal > 16)
{
// Try again and attempt at sending a smaller block size.
_writeBlockNumber = 0;
BlockSizeInternal /= 2;
continue;
}
Context.Response = result;
throw new CoapBlockException($"Failed to send block ({_writeBlockNumber}) to remote endpoint", CoapException.FromCoapMessage(result), result.Code);
}
}
// flag the mot recent flush has been performed
if (_writer.Length <= BlockSize)
{
FlushFinishedEvent.Set();
}
if (EndOfStream)
{
break;
}
}
}
catch (Exception ex)
{
// Hold onto the exception to throw it from a synchronous call.
CaughtException = ex;
}
finally
{
EndOfStream = true;
FlushFinishedEvent.Set();
}
}