156 lines
4.4 KiB
Go
156 lines
4.4 KiB
Go
package rtcp
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import (
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"encoding/binary"
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"fmt"
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)
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// The Goodbye packet indicates that one or more sources are no longer active.
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type Goodbye struct {
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// The SSRC/CSRC identifiers that are no longer active
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Sources []uint32
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// Optional text indicating the reason for leaving, e.g., "camera malfunction" or "RTP loop detected"
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Reason string
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}
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// Marshal encodes the Goodbye packet in binary
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func (g Goodbye) Marshal() ([]byte, error) {
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/*
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* 0 1 2 3
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* 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
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* |V=2|P| SC | PT=BYE=203 | length |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | SSRC/CSRC |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* : ... :
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* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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* (opt) | length | reason for leaving ...
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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*/
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rawPacket := make([]byte, g.len())
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packetBody := rawPacket[headerLength:]
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if len(g.Sources) > countMax {
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return nil, errTooManySources
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}
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for i, s := range g.Sources {
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binary.BigEndian.PutUint32(packetBody[i*ssrcLength:], s)
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}
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if g.Reason != "" {
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reason := []byte(g.Reason)
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if len(reason) > sdesMaxOctetCount {
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return nil, errReasonTooLong
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}
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reasonOffset := len(g.Sources) * ssrcLength
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packetBody[reasonOffset] = uint8(len(reason))
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copy(packetBody[reasonOffset+1:], reason)
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}
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hData, err := g.Header().Marshal()
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if err != nil {
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return nil, err
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}
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copy(rawPacket, hData)
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return rawPacket, nil
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}
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// Unmarshal decodes the Goodbye packet from binary
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func (g *Goodbye) Unmarshal(rawPacket []byte) error {
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/*
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* 0 1 2 3
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* 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
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* |V=2|P| SC | PT=BYE=203 | length |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | SSRC/CSRC |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* : ... :
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* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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* (opt) | length | reason for leaving ...
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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*/
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var header Header
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if err := header.Unmarshal(rawPacket); err != nil {
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return err
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}
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if header.Type != TypeGoodbye {
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return errWrongType
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}
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if getPadding(len(rawPacket)) != 0 {
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return errPacketTooShort
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}
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g.Sources = make([]uint32, header.Count)
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reasonOffset := int(headerLength + header.Count*ssrcLength)
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if reasonOffset > len(rawPacket) {
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return errPacketTooShort
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}
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for i := 0; i < int(header.Count); i++ {
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offset := headerLength + i*ssrcLength
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g.Sources[i] = binary.BigEndian.Uint32(rawPacket[offset:])
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}
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if reasonOffset < len(rawPacket) {
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reasonLen := int(rawPacket[reasonOffset])
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reasonEnd := reasonOffset + 1 + reasonLen
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if reasonEnd > len(rawPacket) {
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return errPacketTooShort
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}
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g.Reason = string(rawPacket[reasonOffset+1 : reasonEnd])
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}
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return nil
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}
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// Header returns the Header associated with this packet.
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func (g *Goodbye) Header() Header {
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return Header{
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Padding: false,
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Count: uint8(len(g.Sources)),
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Type: TypeGoodbye,
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Length: uint16((g.len() / 4) - 1),
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}
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}
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func (g *Goodbye) len() int {
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srcsLength := len(g.Sources) * ssrcLength
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reasonLength := len(g.Reason) + 1
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l := headerLength + srcsLength + reasonLength
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// align to 32-bit boundary
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return l + getPadding(l)
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}
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// DestinationSSRC returns an array of SSRC values that this packet refers to.
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func (g *Goodbye) DestinationSSRC() []uint32 {
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out := make([]uint32, len(g.Sources))
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copy(out, g.Sources)
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return out
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}
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func (g Goodbye) String() string {
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out := "Goodbye\n"
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for i, s := range g.Sources {
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out += fmt.Sprintf("\tSource %d: %x\n", i, s)
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}
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out += fmt.Sprintf("\tReason: %s\n", g.Reason)
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return out
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}
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