public async Task Listen(IByteReceiver byteReceiver,
IStreamFactory streamFactory,
IScheduler scheduler,
string destinationPath = "",
CancellationToken cancellationToken = default)
{
var basePath = string.IsNullOrWhiteSpace(destinationPath)
? ""
: destinationPath;
if (basePath != "")
{
Directory.CreateDirectory(basePath); //does not throw an exception if it does not exist
}
var cancellationTokenSource = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
var token = cancellationTokenSource.Token;
var packetBufferObservable = new Subject <byte[]>();
var protoMessageObservable = packetBufferObservable
.ObserveOn(scheduler)
.Select(bytes =>
{
ProtoMessage message;
using (var memoryStream = new MemoryStream(bytes))
{
var protoMessage = Serializer.Deserialize <ProtoMessage>(memoryStream);
message = protoMessage;
}
return(message);
});
var headerCache = new ConcurrentDictionary <Guid, Header>();
var payloadCache = new ConcurrentDictionary <Guid, List <ProtoMessage> >();
var fileWriteRequestSubject = new Subject <FileWriteWrapper>();
var headerObservable = protoMessageObservable
.Where(message => !string.IsNullOrWhiteSpace(message.FileName) && message.PayloadCount.HasValue);
var payloadObservable = protoMessageObservable
.Where(message => message.PayloadIndex.HasValue && message.Payload != null);
string GetFileName(ProtoMessage header)
{
return($"{System.DateTime.Now:HH-mm-ss-ffff}.{header.FileName}");
}
Header ConvertToHeader(ProtoMessage header)
{
return(new Header
{
BroadcastId = header.GetBroadcastId(), FileName = GetFileName(header),
PayloadCount = header.PayloadCount.Value, PayloadMaxBytes = header.PayloadMaxSize.Value
});
}
void HandleCachedPayloads(Guid guid, Header header1)
{
if (payloadCache.TryRemove(guid, out var payloads))
{
var p = payloads.ToArray(); //todo:figure out why this bombed - List changed exception
payloads.Clear();
foreach (var payload in p)
{
fileWriteRequestSubject.OnNext(new FileWriteWrapper()
{
Header = header1, Payload = payload
});
}
}
}
headerObservable
.ObserveOn(scheduler)
.Subscribe(protoHeader => headerCache.AddOrUpdate(protoHeader.GetBroadcastId(),
bcid =>
{
//todo: decide if header.payloadCount X headerMaxPayloadSize is too much
var header = ConvertToHeader(protoHeader);
HandleCachedPayloads(bcid, header);
return(header);
},
(bcid, header) =>
{
HandleCachedPayloads(bcid, header);
return(header);
})
);
var md5 = MD5.Create();
bool CheckHash(ProtoMessage payload)
{
var expected = payload.Hash;
if (expected == null || expected.Length == 0)
{
return(false);
}
var actual = md5.ComputeHash(payload.Payload);
if (actual.Length == 0 || expected.Length != actual.Length)
{
return(false);
}
for (var index = 0; index < expected.Length; index++)
{
var expectedByte = expected[index];
var actualByte = actual[index];
if (expectedByte != actualByte)
{
return(false);
}
}
return(true);
}
payloadObservable
.ObserveOn(scheduler)
.Subscribe(payload =>
{
if (!CheckHash(payload))
{
throw new InvalidDataException("Hash check failed");
//todo: return error statistics to the caller
}
if (headerCache.TryGetValue(payload.GetBroadcastId(), out var header))
{
fileWriteRequestSubject.OnNext(new FileWriteWrapper()
{
Header = header, Payload = payload
});
}
else
{
payloadCache.AddOrUpdate(payload.GetBroadcastId(),
bcid =>
{
var list = new List <ProtoMessage>();
list.Add(payload);
return(list);
},
(bcid, list) =>
{
list.Add(payload);
return(list);
});
}
});
var writeCompleteObservable = fileWriteRequestSubject
//.ObserveOn(observableScheduler)
.Select(writeRequest =>
{
if (writeRequest.Payload.Payload.Length > writeRequest.Header.PayloadMaxBytes)
{
throw new ArgumentException("Payload exceeds max byte length");
}
return(Observable.FromAsync(async() =>
{
var fullPath = Path.Combine(basePath, writeRequest.Header.FileName);
using var writer = streamFactory.CreateWriter(fullPath);
var writeIndex = writeRequest.Payload.PayloadIndex.Value *
writeRequest.Header.PayloadMaxBytes;
await writer.Write(writeIndex, writeRequest.Payload.Payload, token).ConfigureAwait(false);
return writeRequest.Header;
}));
}).Merge(1);
var fileWriteObservable = writeCompleteObservable
.ObserveOn(scheduler)
.GroupBy(w => w.BroadcastId);
const int fileCompleteTimeout = 10;
var fileTimeout = TimeSpan.FromSeconds(fileCompleteTimeout);
var fileStoppedObservable = CreateTimeoutObservable(fileTimeout, fileWriteObservable, scheduler);
var fileStoppedSub = fileStoppedObservable.Subscribe(header =>
{
OnBroadcastEnded(new BroadcastResult(header.BroadcastId, header.FileName));
});
token.Register(() => fileStoppedSub.Dispose());
void OnBytesReceived(object sender, IBytesReceived bytesReceived)
{
packetBufferObservable.OnNext(bytesReceived.Bytes);
}
byteReceiver.BytesReceived += OnBytesReceived;
cancellationToken.Register(() => { byteReceiver.BytesReceived -= OnBytesReceived; });
await byteReceiver.Listen(cancellationToken);
}