1 files changed, 174 insertions, 0 deletions
diff --git a/vendor/github.com/pion/rtcp/transport_layer_nack.go b/vendor/github.com/pion/rtcp/transport_layer_nack.go
new file mode 100644
index 0000000..f7ab803
--- /dev/null
+++ b/vendor/github.com/pion/rtcp/transport_layer_nack.go
@@ -0,0 +1,174 @@
+package rtcp
+
+import (
+	"encoding/binary"
+	"fmt"
+	"math"
+)
+
+// PacketBitmap shouldn't be used like a normal integral,
+// so it's type is masked here. Access it with PacketList().
+type PacketBitmap uint16
+
+// NackPair is a wire-representation of a collection of
+// Lost RTP packets
+type NackPair struct {
+	// ID of lost packets
+	PacketID uint16
+
+	// Bitmask of following lost packets
+	LostPackets PacketBitmap
+}
+
+// The TransportLayerNack packet informs the encoder about the loss of a transport packet
+// IETF RFC 4585, Section 6.2.1
+// https://tools.ietf.org/html/rfc4585#section-6.2.1
+type TransportLayerNack struct {
+	// SSRC of sender
+	SenderSSRC uint32
+
+	// SSRC of the media source
+	MediaSSRC uint32
+
+	Nacks []NackPair
+}
+
+var _ Packet = (*TransportLayerNack)(nil) // assert is a Packet
+
+// NackPairsFromSequenceNumbers generates a slice of NackPair from a list of SequenceNumbers
+// This handles generating the proper values for PacketID/LostPackets
+func NackPairsFromSequenceNumbers(sequenceNumbers []uint16) (pairs []NackPair) {
+	if len(sequenceNumbers) == 0 {
+		return []NackPair{}
+	}
+
+	nackPair := &NackPair{PacketID: sequenceNumbers[0]}
+	for i := 1; i < len(sequenceNumbers); i++ {
+		m := sequenceNumbers[i]
+
+		if m-nackPair.PacketID > 16 {
+			pairs = append(pairs, *nackPair)
+			nackPair = &NackPair{PacketID: m}
+			continue
+		}
+
+		nackPair.LostPackets |= 1 << (m - nackPair.PacketID - 1)
+	}
+	pairs = append(pairs, *nackPair)
+	return
+}
+
+// Range calls f sequentially for each sequence number covered by n.
+// If f returns false, Range stops the iteration.
+func (n *NackPair) Range(f func(seqno uint16) bool) {
+	more := f(n.PacketID)
+	if !more {
+		return
+	}
+
+	b := n.LostPackets
+	for i := uint16(0); b != 0; i++ {
+		if (b & (1 << i)) != 0 {
+			b &^= (1 << i)
+			more = f(n.PacketID + i + 1)
+			if !more {
+				return
+			}
+		}
+	}
+}
+
+// PacketList returns a list of Nack'd packets that's referenced by a NackPair
+func (n *NackPair) PacketList() []uint16 {
+	out := make([]uint16, 0, 17)
+	n.Range(func(seqno uint16) bool {
+		out = append(out, seqno)
+		return true
+	})
+	return out
+}
+
+const (
+	tlnLength  = 2
+	nackOffset = 8
+)
+
+// Marshal encodes the TransportLayerNack in binary
+func (p TransportLayerNack) Marshal() ([]byte, error) {
+	if len(p.Nacks)+tlnLength > math.MaxUint8 {
+		return nil, errTooManyReports
+	}
+
+	rawPacket := make([]byte, nackOffset+(len(p.Nacks)*4))
+	binary.BigEndian.PutUint32(rawPacket, p.SenderSSRC)
+	binary.BigEndian.PutUint32(rawPacket[4:], p.MediaSSRC)
+	for i := 0; i < len(p.Nacks); i++ {
+		binary.BigEndian.PutUint16(rawPacket[nackOffset+(4*i):], p.Nacks[i].PacketID)
+		binary.BigEndian.PutUint16(rawPacket[nackOffset+(4*i)+2:], uint16(p.Nacks[i].LostPackets))
+	}
+	h := p.Header()
+	hData, err := h.Marshal()
+	if err != nil {
+		return nil, err
+	}
+
+	return append(hData, rawPacket...), nil
+}
+
+// Unmarshal decodes the TransportLayerNack from binary
+func (p *TransportLayerNack) Unmarshal(rawPacket []byte) error {
+	if len(rawPacket) < (headerLength + ssrcLength) {
+		return errPacketTooShort
+	}
+
+	var h Header
+	if err := h.Unmarshal(rawPacket); err != nil {
+		return err
+	}
+
+	if len(rawPacket) < (headerLength + int(4*h.Length)) {
+		return errPacketTooShort
+	}
+
+	if h.Type != TypeTransportSpecificFeedback || h.Count != FormatTLN {
+		return errWrongType
+	}
+
+	p.SenderSSRC = binary.BigEndian.Uint32(rawPacket[headerLength:])
+	p.MediaSSRC = binary.BigEndian.Uint32(rawPacket[headerLength+ssrcLength:])
+	for i := headerLength + nackOffset; i < (headerLength + int(h.Length*4)); i += 4 {
+		p.Nacks = append(p.Nacks, NackPair{
+			binary.BigEndian.Uint16(rawPacket[i:]),
+			PacketBitmap(binary.BigEndian.Uint16(rawPacket[i+2:])),
+		})
+	}
+	return nil
+}
+
+func (p *TransportLayerNack) len() int {
+	return headerLength + nackOffset + (len(p.Nacks) * 4)
+}
+
+// Header returns the Header associated with this packet.
+func (p *TransportLayerNack) Header() Header {
+	return Header{
+		Count:  FormatTLN,
+		Type:   TypeTransportSpecificFeedback,
+		Length: uint16((p.len() / 4) - 1),
+	}
+}
+
+func (p TransportLayerNack) String() string {
+	out := fmt.Sprintf("TransportLayerNack from %x\n", p.SenderSSRC)
+	out += fmt.Sprintf("\tMedia Ssrc %x\n", p.MediaSSRC)
+	out += "\tID\tLostPackets\n"
+	for _, i := range p.Nacks {
+		out += fmt.Sprintf("\t%d\t%b\n", i.PacketID, i.LostPackets)
+	}
+	return out
+}
+
+// DestinationSSRC returns an array of SSRC values that this packet refers to.
+func (p *TransportLayerNack) DestinationSSRC() []uint32 {
+	return []uint32{p.MediaSSRC}
+}