Add Header() method to Packet

Simplifies the API. Unmarshal can now return one Packet value instead
of both a packet and a header.

Relates to #119

pkg/rtcp/goodbye.go

@@ -30,14 +30,15 @@ func (g Goodbye) Marshal() ([]byte, error) {
 	 *       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 	 */
 
-	rawPacket := make([]byte, len(g.Sources)*ssrcLength)
+	rawPacket := make([]byte, g.len())
+	packetBody := rawPacket[headerLength:]
 
 	if len(g.Sources) > countMax {
 		return nil, errTooManySources
 	}
 
 	for i, s := range g.Sources {
-		binary.BigEndian.PutUint32(rawPacket[i*ssrcLength:], s)
+		binary.BigEndian.PutUint32(packetBody[i*ssrcLength:], s)
 	}
 
 	if g.Reason != "" {
@@ -47,25 +48,16 @@ func (g Goodbye) Marshal() ([]byte, error) {
 			return nil, errReasonTooLong
 		}
 
-		rawPacket = append(rawPacket, uint8(len(reason)))
-		rawPacket = append(rawPacket, reason...)
-
-		// align to 32-bit boundary
-		rawPacket = append(rawPacket, make([]byte, util.GetPadding(len(rawPacket)))...)
+		reasonOffset := len(g.Sources) * ssrcLength
+		packetBody[reasonOffset] = uint8(len(reason))
+		copy(packetBody[reasonOffset+1:], reason)
 	}
 
-	h := Header{
-		Padding: false,
-		Count:   uint8(len(g.Sources)),
-		Type:    TypeGoodbye,
-		Length:  uint16(((headerLength + len(rawPacket)) / 4) - 1),
-	}
-	hData, err := h.Marshal()
+	hData, err := g.Header().Marshal()
 	if err != nil {
 		return nil, err
 	}
-
-	rawPacket = append(hData, rawPacket...)
+	copy(rawPacket, hData)
 
 	return rawPacket, nil
 }
@@ -126,3 +118,23 @@ func (g *Goodbye) Unmarshal(rawPacket []byte) error {
 
 	return nil
 }
+
+// Header returns the Header associated with this packet.
+func (g *Goodbye) Header() Header {
+	return Header{
+		Padding: false,
+		Count:   uint8(len(g.Sources)),
+		Type:    TypeGoodbye,
+		Length:  uint16((g.len() / 4) - 1),
+	}
+}
+
+func (g *Goodbye) len() int {
+	srcsLength := len(g.Sources) * ssrcLength
+	reasonLength := len(g.Reason) + 1
+
+	l := headerLength + srcsLength + reasonLength
+
+	// align to 32-bit boundary
+	return l + util.GetPadding(l)
+}

pkg/rtcp/packet.go

@@ -2,6 +2,8 @@ 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 {
+	Header() Header
+
 	Marshal() ([]byte, error)
 	Unmarshal(rawPacket []byte) error
 }

pkg/rtcp/picture_loss_indication.go

@@ -11,6 +11,8 @@ type PictureLossIndication struct {
 
 	// SSRC where the loss was experienced
 	MediaSSRC uint32
+
+	header Header
 }
 
 const (
@@ -26,9 +28,11 @@ func (p PictureLossIndication) Marshal() ([]byte, error) {
 	 *
 	 * The semantics of this FB message is independent of the payload type.
 	 */
-	rawPacket := make([]byte, 8)
-	binary.BigEndian.PutUint32(rawPacket, p.SenderSSRC)
-	binary.BigEndian.PutUint32(rawPacket[4:], p.MediaSSRC)
+	rawPacket := make([]byte, p.len())
+	packetBody := rawPacket[headerLength:]
+
+	binary.BigEndian.PutUint32(packetBody, p.SenderSSRC)
+	binary.BigEndian.PutUint32(packetBody[4:], p.MediaSSRC)
 
 	h := Header{
 		Count:  pliFMT,
@@ -39,8 +43,9 @@ func (p PictureLossIndication) Marshal() ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
+	copy(rawPacket, hData)
 
-	return append(hData, rawPacket...), nil
+	return rawPacket, nil
 }
 
 // Unmarshal decodes the PictureLossIndication from binary
@@ -62,3 +67,12 @@ func (p *PictureLossIndication) Unmarshal(rawPacket []byte) error {
 	p.MediaSSRC = binary.BigEndian.Uint32(rawPacket[headerLength+ssrcLength:])
 	return nil
 }
+
+// Header returns the Header associated with this packet.
+func (p *PictureLossIndication) Header() Header {
+	return p.header
+}
+
+func (p *PictureLossIndication) len() int {
+	return headerLength + ssrcLength*2
+}

pkg/rtcp/rapid_resynchronization_request.go

@@ -16,6 +16,8 @@ type RapidResynchronizationRequest struct {
 const (
 	rrrFMT          = 5
 	rrrLength       = 2
+	rrrHeaderLength = ssrcLength * 2
+	rrrMediaOffset  = 4
 )
 
 // Marshal encodes the RapidResynchronizationRequest in binary
@@ -26,21 +28,19 @@ func (p RapidResynchronizationRequest) Marshal() ([]byte, error) {
 	 *
 	 * The semantics of this FB message is independent of the payload type.
 	 */
-	rawPacket := make([]byte, 8)
-	binary.BigEndian.PutUint32(rawPacket, p.SenderSSRC)
-	binary.BigEndian.PutUint32(rawPacket[4:], p.MediaSSRC)
+	rawPacket := make([]byte, p.len())
+	packetBody := rawPacket[headerLength:]
 
-	h := Header{
-		Count:  rrrFMT,
-		Type:   TypeTransportSpecificFeedback,
-		Length: rrrLength,
-	}
-	hData, err := h.Marshal()
+	binary.BigEndian.PutUint32(packetBody, p.SenderSSRC)
+	binary.BigEndian.PutUint32(packetBody[rrrMediaOffset:], p.MediaSSRC)
+
+	hData, err := p.Header().Marshal()
 	if err != nil {
 		return nil, err
 	}
+	copy(rawPacket, hData)
 
-	return append(hData, rawPacket...), nil
+	return rawPacket, nil
 }
 
 // Unmarshal decodes the RapidResynchronizationRequest from binary
@@ -63,3 +63,16 @@ func (p *RapidResynchronizationRequest) Unmarshal(rawPacket []byte) error {
 	p.MediaSSRC = binary.BigEndian.Uint32(rawPacket[headerLength+ssrcLength:])
 	return nil
 }
+
+func (p *RapidResynchronizationRequest) len() int {
+	return headerLength + rrrHeaderLength
+}
+
+// Header returns the Header associated with this packet.
+func (p *RapidResynchronizationRequest) Header() Header {
+	return Header{
+		Count:  rrrFMT,
+		Type:   TypeTransportSpecificFeedback,
+		Length: rrrLength,
+	}
+}

pkg/rtcp/raw_packet.go

@@ -23,3 +23,12 @@ func (r *RawPacket) Unmarshal(b []byte) error {
 
 	return nil
 }
+
+// Header returns the Header associated with this packet.
+func (r RawPacket) Header() Header {
+	var h Header
+	if err := h.Unmarshal(r); err != nil {
+		return Header{}
+	}
+	return h
+}

pkg/rtcp/receiver_report.go

@@ -49,33 +49,29 @@ func (r ReceiverReport) Marshal() ([]byte, error) {
 	 *        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 	 */
 
-	rawPacket := make([]byte, ssrcLength)
+	rawPacket := make([]byte, r.len())
+	packetBody := rawPacket[headerLength:]
 
-	binary.BigEndian.PutUint32(rawPacket, r.SSRC)
+	binary.BigEndian.PutUint32(packetBody, r.SSRC)
 
-	for _, rp := range r.Reports {
+	for i, rp := range r.Reports {
 		data, err := rp.Marshal()
 		if err != nil {
 			return nil, err
 		}
-		rawPacket = append(rawPacket, data...)
+		offset := ssrcLength + receptionReportLength*i
+		copy(packetBody[offset:], data)
 	}
 
 	if len(r.Reports) > countMax {
 		return nil, errTooManyReports
 	}
 
-	h := Header{
-		Count:  uint8(len(r.Reports)),
-		Type:   TypeReceiverReport,
-		Length: uint16(((headerLength + len(rawPacket)) / 4) - 1),
-	}
-	hData, err := h.Marshal()
+	hData, err := r.Header().Marshal()
 	if err != nil {
 		return nil, err
 	}
-
-	rawPacket = append(hData, rawPacket...)
+	copy(rawPacket, hData)
 
 	return rawPacket, nil
 }
@@ -139,3 +135,20 @@ func (r *ReceiverReport) Unmarshal(rawPacket []byte) error {
 
 	return nil
 }
+
+func (r *ReceiverReport) len() int {
+	repsLength := 0
+	for _, rep := range r.Reports {
+		repsLength += rep.len()
+	}
+	return headerLength + ssrcLength + repsLength
+}
+
+// Header returns the Header associated with this packet.
+func (r *ReceiverReport) Header() Header {
+	return Header{
+		Count:  uint8(len(r.Reports)),
+		Type:   TypeReceiverReport,
+		Length: uint16((r.len() / 4) - 1),
+	}
+}

pkg/rtcp/reception_report.go

@@ -124,3 +124,7 @@ func (r *ReceptionReport) Unmarshal(rawPacket []byte) error {
 
 	return nil
 }
+
+func (r *ReceptionReport) len() int {
+	return receptionReportLength
+}

pkg/rtcp/sender_report.go

@@ -31,6 +31,8 @@ type SenderReport struct {
 	// block conveys statistics on the reception of RTP packets from a
 	// single synchronization source.
 	Reports []ReceptionReport
+
+	header Header
 }
 
 var (
@@ -87,37 +89,33 @@ func (r SenderReport) Marshal() ([]byte, error) {
 	 *        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 	 */
 
-	rawPacket := make([]byte, srHeaderLength)
+	rawPacket := make([]byte, r.len())
+	packetBody := rawPacket[headerLength:]
 
-	binary.BigEndian.PutUint32(rawPacket[srSSRCOffset:], r.SSRC)
-	binary.BigEndian.PutUint64(rawPacket[srNTPOffset:], r.NTPTime)
-	binary.BigEndian.PutUint32(rawPacket[srRTPOffset:], r.RTPTime)
-	binary.BigEndian.PutUint32(rawPacket[srPacketCountOffset:], r.PacketCount)
-	binary.BigEndian.PutUint32(rawPacket[srOctetCountOffset:], r.OctetCount)
+	binary.BigEndian.PutUint32(packetBody[srSSRCOffset:], r.SSRC)
+	binary.BigEndian.PutUint64(packetBody[srNTPOffset:], r.NTPTime)
+	binary.BigEndian.PutUint32(packetBody[srRTPOffset:], r.RTPTime)
+	binary.BigEndian.PutUint32(packetBody[srPacketCountOffset:], r.PacketCount)
+	binary.BigEndian.PutUint32(packetBody[srOctetCountOffset:], r.OctetCount)
 
-	for _, rp := range r.Reports {
+	for i, rp := range r.Reports {
 		data, err := rp.Marshal()
 		if err != nil {
 			return nil, err
 		}
-		rawPacket = append(rawPacket, data...)
+		offset := srHeaderLength + receptionReportLength*i
+		copy(packetBody[offset:], data)
 	}
 
 	if len(r.Reports) > countMax {
 		return nil, errTooManyReports
 	}
 
-	h := Header{
-		Count:  uint8(len(r.Reports)),
-		Type:   TypeSenderReport,
-		Length: uint16(((headerLength + len(rawPacket)) / 4) - 1),
-	}
-	hData, err := h.Marshal()
+	hData, err := r.Header().Marshal()
 	if err != nil {
 		return nil, err
 	}
-
-	rawPacket = append(hData, rawPacket...)
+	copy(rawPacket, hData)
 
 	return rawPacket, nil
 }
@@ -197,3 +195,20 @@ func (r *SenderReport) Unmarshal(rawPacket []byte) error {
 
 	return nil
 }
+
+func (r *SenderReport) len() int {
+	repsLength := 0
+	for _, rep := range r.Reports {
+		repsLength += rep.len()
+	}
+	return headerLength + srHeaderLength + repsLength
+}
+
+// Header returns the Header associated with this packet.
+func (r *SenderReport) Header() Header {
+	return Header{
+		Count:  uint8(len(r.Reports)),
+		Type:   TypeSenderReport,
+		Length: uint16((r.len() / 4) - 1),
+	}
+}

pkg/rtcp/source_description.go

@@ -82,30 +82,28 @@ func (s SourceDescription) Marshal() ([]byte, error) {
 	 *        +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
 	 */
 
-	rawPacket := make([]byte, 0)
+	rawPacket := make([]byte, s.len())
+	packetBody := rawPacket[headerLength:]
+
+	chunkOffset := 0
 	for _, c := range s.Chunks {
 		data, err := c.Marshal()
 		if err != nil {
 			return nil, err
 		}
-		rawPacket = append(rawPacket, data...)
+		copy(packetBody[chunkOffset:], data)
+		chunkOffset += len(data)
 	}
 
 	if len(s.Chunks) > countMax {
 		return nil, errTooManyChunks
 	}
 
-	h := Header{
-		Count:  uint8(len(s.Chunks)),
-		Type:   TypeSourceDescription,
-		Length: uint16(((headerLength + len(rawPacket)) / 4) - 1),
-	}
-	hData, err := h.Marshal()
+	hData, err := s.Header().Marshal()
 	if err != nil {
 		return nil, err
 	}
-
-	rawPacket = append(hData, rawPacket...)
+	copy(rawPacket, hData)
 
 	return rawPacket, nil
 }
@@ -156,6 +154,23 @@ func (s *SourceDescription) Unmarshal(rawPacket []byte) error {
 	return nil
 }
 
+func (s *SourceDescription) len() int {
+	chunksLength := 0
+	for _, c := range s.Chunks {
+		chunksLength += c.len()
+	}
+	return headerLength + chunksLength
+}
+
+// Header returns the Header associated with this packet.
+func (s *SourceDescription) Header() Header {
+	return Header{
+		Count:  uint8(len(s.Chunks)),
+		Type:   TypeSourceDescription,
+		Length: uint16((s.len() / 4) - 1),
+	}
+}
+
 // A SourceDescriptionChunk contains items describing a single RTP source
 type SourceDescriptionChunk struct {
 	// The source (ssrc) or contributing source (csrc) identifier this packet describes