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package rtcp
// Packet represents an RTCP packet, a protocol used for out-of-band statistics and control information for an RTP session
type Packet interface {
// DestinationSSRC returns an array of SSRC values that this packet refers to.
DestinationSSRC() []uint32
Marshal() ([]byte, error)
Unmarshal(rawPacket []byte) error
}
// Unmarshal takes an entire udp datagram (which may consist of multiple RTCP packets) and
// returns the unmarshaled packets it contains.
//
// If this is a reduced-size RTCP packet a feedback packet (Goodbye, SliceLossIndication, etc)
// will be returned. Otherwise, the underlying type of the returned packet will be
// CompoundPacket.
func Unmarshal(rawData []byte) ([]Packet, error) {
var packets []Packet
for len(rawData) != 0 {
p, processed, err := unmarshal(rawData)
if err != nil {
return nil, err
}
packets = append(packets, p)
rawData = rawData[processed:]
}
switch len(packets) {
// Empty packet
case 0:
return nil, errInvalidHeader
// Multiple Packets
default:
return packets, nil
}
}
// Marshal takes an array of Packets and serializes them to a single buffer
func Marshal(packets []Packet) ([]byte, error) {
out := make([]byte, 0)
for _, p := range packets {
data, err := p.Marshal()
if err != nil {
return nil, err
}
out = append(out, data...)
}
return out, nil
}
// unmarshal is a factory which pulls the first RTCP packet from a bytestream,
// and returns it's parsed representation, and the amount of data that was processed.
func unmarshal(rawData []byte) (packet Packet, bytesprocessed int, err error) {
var h Header
err = h.Unmarshal(rawData)
if err != nil {
return nil, 0, err
}
bytesprocessed = int(h.Length+1) * 4
if bytesprocessed > len(rawData) {
return nil, 0, errPacketTooShort
}
inPacket := rawData[:bytesprocessed]
switch h.Type {
case TypeSenderReport:
packet = new(SenderReport)
case TypeReceiverReport:
packet = new(ReceiverReport)
case TypeSourceDescription:
packet = new(SourceDescription)
case TypeGoodbye:
packet = new(Goodbye)
case TypeTransportSpecificFeedback:
switch h.Count {
case FormatTLN:
packet = new(TransportLayerNack)
case FormatRRR:
packet = new(RapidResynchronizationRequest)
case FormatTCC:
packet = new(TransportLayerCC)
default:
packet = new(RawPacket)
}
case TypePayloadSpecificFeedback:
switch h.Count {
case FormatPLI:
packet = new(PictureLossIndication)
case FormatSLI:
packet = new(SliceLossIndication)
case FormatREMB:
packet = new(ReceiverEstimatedMaximumBitrate)
case FormatFIR:
packet = new(FullIntraRequest)
default:
packet = new(RawPacket)
}
default:
packet = new(RawPacket)
}
err = packet.Unmarshal(inPacket)
return packet, bytesprocessed, err
}
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