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|
package rtcp
import (
"encoding/binary"
"fmt"
)
// The Goodbye packet indicates that one or more sources are no longer active.
type Goodbye struct {
// The SSRC/CSRC identifiers that are no longer active
Sources []uint32
// Optional text indicating the reason for leaving, e.g., "camera malfunction" or "RTP loop detected"
Reason string
}
// Marshal encodes the Goodbye packet in binary
func (g Goodbye) Marshal() ([]byte, error) {
/*
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |V=2|P| SC | PT=BYE=203 | length |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | SSRC/CSRC |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* : ... :
* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
* (opt) | length | reason for leaving ...
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
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(packetBody[i*ssrcLength:], s)
}
if g.Reason != "" {
reason := []byte(g.Reason)
if len(reason) > sdesMaxOctetCount {
return nil, errReasonTooLong
}
reasonOffset := len(g.Sources) * ssrcLength
packetBody[reasonOffset] = uint8(len(reason))
copy(packetBody[reasonOffset+1:], reason)
}
hData, err := g.Header().Marshal()
if err != nil {
return nil, err
}
copy(rawPacket, hData)
return rawPacket, nil
}
// Unmarshal decodes the Goodbye packet from binary
func (g *Goodbye) Unmarshal(rawPacket []byte) error {
/*
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |V=2|P| SC | PT=BYE=203 | length |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | SSRC/CSRC |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* : ... :
* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
* (opt) | length | reason for leaving ...
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
var header Header
if err := header.Unmarshal(rawPacket); err != nil {
return err
}
if header.Type != TypeGoodbye {
return errWrongType
}
if getPadding(len(rawPacket)) != 0 {
return errPacketTooShort
}
g.Sources = make([]uint32, header.Count)
reasonOffset := int(headerLength + header.Count*ssrcLength)
if reasonOffset > len(rawPacket) {
return errPacketTooShort
}
for i := 0; i < int(header.Count); i++ {
offset := headerLength + i*ssrcLength
g.Sources[i] = binary.BigEndian.Uint32(rawPacket[offset:])
}
if reasonOffset < len(rawPacket) {
reasonLen := int(rawPacket[reasonOffset])
reasonEnd := reasonOffset + 1 + reasonLen
if reasonEnd > len(rawPacket) {
return errPacketTooShort
}
g.Reason = string(rawPacket[reasonOffset+1 : reasonEnd])
}
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 + getPadding(l)
}
// DestinationSSRC returns an array of SSRC values that this packet refers to.
func (g *Goodbye) DestinationSSRC() []uint32 {
out := make([]uint32, len(g.Sources))
copy(out, g.Sources)
return out
}
func (g Goodbye) String() string {
out := "Goodbye\n"
for i, s := range g.Sources {
out += fmt.Sprintf("\tSource %d: %x\n", i, s)
}
out += fmt.Sprintf("\tReason: %s\n", g.Reason)
return out
}
|
