/// <summary>
/// Process provided <paramref name="baseBandFrame"/>. Decapsulate frames from <see cref="GsePacket"/>s in <paramref name="baseBandFrame"/>. In case of GSE fragmentation,
/// add <see cref="GsePacket"/>s to corresponding <see cref="GseReassemblyBuffer"/>s and perform one step of thr GSE reassembly procedure. Successfully reassembled GSE is
/// then decapsulated, too.
/// </summary>
/// <param name="baseBandFrame">Base-Band frame from which the <see cref="GsePacket"/>s (<see cref="BaseBandFrame.UserPackets"/>) should be decapsulated.</param>
/// <param name="encapsulatingFrames">Frames carrying provided <paramref name="baseBandFrame"/>.</param>
/// <returns>Decapsualted frames, which were eventually reassembled if it was required.</returns>
public IEnumerable <PmFrameBase> Process([Required] BaseBandFrame baseBandFrame, [Required] ICollection <PmFrameBase> encapsulatingFrames)
{
var decapsulatedFrames = new List <PmFrameBase>();
// key for identification of a stream used in this._reassemblyBuffers
var si = baseBandFrame.BaseBandHeader.InputStreamIdentifier ?? SingleInputStreamReservedIdentifier;
// lazy instantiation of reassembling structures for given stream (si)
if (!this._reassemblyBuffers.ContainsKey(si))
{
this._reassemblyBuffers.Add(si, new Dictionary <byte, GseReassemblyBuffer>());
}
var stop = false;
foreach (var gsePacket in baseBandFrame.UserPackets)
{
if (stop)
{
break;
}
switch (gsePacket.Type)
{
case PacketType.Complete:
// complete packet is here considered one fragment itself
var completeFrame = PmFrameEncapsulated.Create(new List <IFragment>(1)
{
gsePacket
});
completeFrame.DecapsulatedFromFrames.AddRange(encapsulatingFrames);
foreach (var encapsulatingFrame in encapsulatingFrames)
{
encapsulatingFrame.EncapsulatedFrames.Add(completeFrame);
}
decapsulatedFrames.Add(completeFrame);
continue;
case PacketType.Padding:
// "(...) padding is detected and the Receiver shall discard all the following bytes until the end of the Base
// Band frame." http://www.etsi.org/deliver/etsi_ts/102600_102699/10260601/01.02.01_60/ts_10260601v010201p.pdf#page=22
stop = true;
break;
case PacketType.Start:
if (!gsePacket.Header.FragmentID.HasValue)
{
throw new ArgumentException("Fragmented packet does not contain FragmentID.");
}
// lazy instantiation of GseReassemblyBuffer for given FragmentID
if (!this._reassemblyBuffers[si].ContainsKey(gsePacket.Header.FragmentID.Value))
{
this._reassemblyBuffers[si].Add(gsePacket.Header.FragmentID.Value, new GseReassemblyBuffer());
}
if (this._reassemblyBuffers[si][gsePacket.Header.FragmentID.Value].Count > 0)
{
// "(...) the receiver has fragments for that Frag ID in a reassembly buffer. If the Frag ID is already in use,
// the receiver shall first discard the already buffered fragments corresponding to this Frag ID;"
// http://www.etsi.org/deliver/etsi_ts/102600_102699/10260601/01.02.01_60/ts_10260601v010201p.pdf#page=21
this._reassemblyBuffers[si][gsePacket.Header.FragmentID.Value].Clear();
// Buffered GSE fragments were discarded.
}
this._reassemblyBuffers[si][gsePacket.Header.FragmentID.Value].Add(gsePacket, encapsulatingFrames);
break;
case PacketType.Intermediate:
if (!gsePacket.Header.FragmentID.HasValue)
{
throw new ArgumentException("Fragmented packet does not contain FragmentID.");
}
if (this._reassemblyBuffers[si].ContainsKey(gsePacket.Header.FragmentID.Value))
{
this._reassemblyBuffers[si][gsePacket.Header.FragmentID.Value].Add(gsePacket, encapsulatingFrames);
}
// else: Intermediate GSE fragment was discarded because there was not Start GSE fragment before.
break;
case PacketType.End:
if (!gsePacket.Header.FragmentID.HasValue)
{
throw new ArgumentException("Fragmented packet does not contain FragmentID.");
}
if (this._reassemblyBuffers[si].ContainsKey(gsePacket.Header.FragmentID.Value))
{
this._reassemblyBuffers[si][gsePacket.Header.FragmentID.Value].Add(gsePacket, encapsulatingFrames);
var decapsulated = this._reassemblyBuffers[si][gsePacket.Header.FragmentID.Value].Retrieve();
decapsulatedFrames.Add(decapsulated);
}
// else: End GSE fragment was discarded because there was not Start GSE fragment before.
break;
default:
throw new ArgumentOutOfRangeException($"Unexpected PacketType ({gsePacket.Type}).");
}
}
foreach (var buffer in this._reassemblyBuffers[si])
{
buffer.Value.BaseBandProcessed();
}
return(decapsulatedFrames);
}
public L7DvbS2GseDecapsulatorBlock()
{
this._outputBuffer = new BufferBlock <PmFrameBase>();
this._decapsulator = new ActionBlock <L7Conversation>(async l7Conversation =>
{
var stream = new PDUStreamBasedProvider(l7Conversation, EfcPDUProviderType.ContinueInterlay);
var reader = new PDUStreamReader(stream, Encoding.GetEncoding(437), true)
{
ReadBigEndian = true
};
var gseReassembler = new GseReassemblingDecapsulator();
while (!reader.EndOfStream)
{
try
{
var bb = BaseBandFrame.Parse(reader);
// It's important to get `reader.PDUStreamBasedProvider.GetCurrentPDU()` after parsing Base-Band frame.
// During reading, its value is set to the last read PDU. If we would call it before Base-Band parsing,
// retrieved value would not be current PDU, but the previous one.
// frames encapsulating parsed Base-Band
var pdu = reader.PDUStreamBasedProvider.GetCurrentPDU();
if (pdu == null)
{
break;
}
var frames = ImmutableList.CreateRange(pdu.FrameList);
// Reassemble any fragmented GSE packets and obtain decapsulated frames, if any of them have been just finished.
var decapsulatedFrames = gseReassembler.Process(bb, frames);
foreach (var f in decapsulatedFrames)
{
this._outputBuffer.Post(f);
}
}
catch (InvalidPacketFormatException)
{
// Current PDU of l7Conversation does not contain DVB-S2 Base Band Frame.
}
catch (NotImplementedException)
{
// NOTE: Only Generic Continuous Stream Input is supported at this moment.
}
// move to the next message
if (!reader.NewMessage())
{
break;
}
}
});
this._decapsulator.Completion.ContinueWith(t =>
{
if (t.IsFaulted)
{
((IDataflowBlock)this._outputBuffer).Fault(t.Exception);
}
else
{
this._outputBuffer.Complete();
}
});
}
