351 lines
11 KiB
Go
351 lines
11 KiB
Go
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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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// SDESType is the item type used in the RTCP SDES control packet.
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type SDESType uint8
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// RTP SDES item types registered with IANA. See: https://www.iana.org/assignments/rtp-parameters/rtp-parameters.xhtml#rtp-parameters-5
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const (
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SDESEnd SDESType = iota // end of SDES list RFC 3550, 6.5
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SDESCNAME // canonical name RFC 3550, 6.5.1
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SDESName // user name RFC 3550, 6.5.2
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SDESEmail // user's electronic mail address RFC 3550, 6.5.3
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SDESPhone // user's phone number RFC 3550, 6.5.4
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SDESLocation // geographic user location RFC 3550, 6.5.5
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SDESTool // name of application or tool RFC 3550, 6.5.6
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SDESNote // notice about the source RFC 3550, 6.5.7
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SDESPrivate // private extensions RFC 3550, 6.5.8 (not implemented)
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)
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func (s SDESType) String() string {
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switch s {
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case SDESEnd:
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return "END"
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case SDESCNAME:
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return "CNAME"
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case SDESName:
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return "NAME"
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case SDESEmail:
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return "EMAIL"
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case SDESPhone:
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return "PHONE"
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case SDESLocation:
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return "LOC"
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case SDESTool:
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return "TOOL"
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case SDESNote:
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return "NOTE"
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case SDESPrivate:
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return "PRIV"
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default:
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return string(s)
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}
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}
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const (
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sdesSourceLen = 4
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sdesTypeLen = 1
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sdesTypeOffset = 0
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sdesOctetCountLen = 1
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sdesOctetCountOffset = 1
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sdesMaxOctetCount = (1 << 8) - 1
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sdesTextOffset = 2
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)
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// A SourceDescription (SDES) packet describes the sources in an RTP stream.
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type SourceDescription struct {
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Chunks []SourceDescriptionChunk
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}
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// Marshal encodes the SourceDescription in binary
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func (s SourceDescription) 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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* header |V=2|P| SC | PT=SDES=202 | length |
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* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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* chunk | SSRC/CSRC_1 |
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* 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | SDES items |
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* | ... |
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* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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* chunk | SSRC/CSRC_2 |
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* 2 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | SDES items |
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* | ... |
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* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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*/
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rawPacket := make([]byte, s.len())
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packetBody := rawPacket[headerLength:]
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chunkOffset := 0
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for _, c := range s.Chunks {
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data, err := c.Marshal()
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if err != nil {
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return nil, err
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}
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copy(packetBody[chunkOffset:], data)
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chunkOffset += len(data)
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}
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if len(s.Chunks) > countMax {
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return nil, errTooManyChunks
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}
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hData, err := s.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 SourceDescription from binary
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func (s *SourceDescription) 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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* header |V=2|P| SC | PT=SDES=202 | length |
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* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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* chunk | SSRC/CSRC_1 |
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* 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | SDES items |
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* | ... |
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* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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* chunk | SSRC/CSRC_2 |
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* 2 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | SDES items |
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* | ... |
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* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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*/
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var h Header
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if err := h.Unmarshal(rawPacket); err != nil {
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return err
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}
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if h.Type != TypeSourceDescription {
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return errWrongType
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}
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for i := headerLength; i < len(rawPacket); {
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var chunk SourceDescriptionChunk
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if err := chunk.Unmarshal(rawPacket[i:]); err != nil {
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return err
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}
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s.Chunks = append(s.Chunks, chunk)
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i += chunk.len()
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}
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if len(s.Chunks) != int(h.Count) {
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return errInvalidHeader
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}
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return nil
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}
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func (s *SourceDescription) len() int {
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chunksLength := 0
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for _, c := range s.Chunks {
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chunksLength += c.len()
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}
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return headerLength + chunksLength
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}
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// Header returns the Header associated with this packet.
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func (s *SourceDescription) Header() Header {
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return Header{
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Count: uint8(len(s.Chunks)),
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Type: TypeSourceDescription,
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Length: uint16((s.len() / 4) - 1),
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}
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}
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// A SourceDescriptionChunk contains items describing a single RTP source
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type SourceDescriptionChunk struct {
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// The source (ssrc) or contributing source (csrc) identifier this packet describes
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Source uint32
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Items []SourceDescriptionItem
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}
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// Marshal encodes the SourceDescriptionChunk in binary
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func (s SourceDescriptionChunk) Marshal() ([]byte, error) {
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/*
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* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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* | SSRC/CSRC_1 |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | SDES items |
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* | ... |
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* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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*/
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rawPacket := make([]byte, sdesSourceLen)
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binary.BigEndian.PutUint32(rawPacket, s.Source)
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for _, it := range s.Items {
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data, err := it.Marshal()
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if err != nil {
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return nil, err
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}
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rawPacket = append(rawPacket, data...)
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}
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// The list of items in each chunk MUST be terminated by one or more null octets
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rawPacket = append(rawPacket, uint8(SDESEnd))
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// additional null octets MUST be included if needed to pad until the next 32-bit boundary
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rawPacket = append(rawPacket, make([]byte, getPadding(len(rawPacket)))...)
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return rawPacket, nil
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}
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// Unmarshal decodes the SourceDescriptionChunk from binary
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func (s *SourceDescriptionChunk) Unmarshal(rawPacket []byte) error {
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/*
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* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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* | SSRC/CSRC_1 |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | SDES items |
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* | ... |
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* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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*/
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if len(rawPacket) < (sdesSourceLen + sdesTypeLen) {
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return errPacketTooShort
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}
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s.Source = binary.BigEndian.Uint32(rawPacket)
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for i := 4; i < len(rawPacket); {
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if pktType := SDESType(rawPacket[i]); pktType == SDESEnd {
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return nil
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}
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var it SourceDescriptionItem
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if err := it.Unmarshal(rawPacket[i:]); err != nil {
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return err
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}
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s.Items = append(s.Items, it)
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i += it.len()
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}
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return errPacketTooShort
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}
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func (s SourceDescriptionChunk) len() int {
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len := sdesSourceLen
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for _, it := range s.Items {
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len += it.len()
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}
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len += sdesTypeLen // for terminating null octet
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// align to 32-bit boundary
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len += getPadding(len)
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return len
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}
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// A SourceDescriptionItem is a part of a SourceDescription that describes a stream.
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type SourceDescriptionItem struct {
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// The type identifier for this item. eg, SDESCNAME for canonical name description.
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//
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// Type zero or SDESEnd is interpreted as the end of an item list and cannot be used.
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Type SDESType
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// Text is a unicode text blob associated with the item. Its meaning varies based on the item's Type.
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Text string
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}
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func (s SourceDescriptionItem) len() int {
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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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* | CNAME=1 | length | user and domain name ...
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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*/
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return sdesTypeLen + sdesOctetCountLen + len([]byte(s.Text))
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}
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// Marshal encodes the SourceDescriptionItem in binary
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func (s SourceDescriptionItem) 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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* | CNAME=1 | length | user and domain name ...
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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*/
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if s.Type == SDESEnd {
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return nil, errSDESMissingType
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}
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rawPacket := make([]byte, sdesTypeLen+sdesOctetCountLen)
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rawPacket[sdesTypeOffset] = uint8(s.Type)
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txtBytes := []byte(s.Text)
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octetCount := len(txtBytes)
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if octetCount > sdesMaxOctetCount {
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return nil, errSDESTextTooLong
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}
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rawPacket[sdesOctetCountOffset] = uint8(octetCount)
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rawPacket = append(rawPacket, txtBytes...)
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return rawPacket, nil
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}
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// Unmarshal decodes the SourceDescriptionItem from binary
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func (s *SourceDescriptionItem) 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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* | CNAME=1 | length | user and domain name ...
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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*/
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if len(rawPacket) < (sdesTypeLen + sdesOctetCountLen) {
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return errPacketTooShort
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}
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s.Type = SDESType(rawPacket[sdesTypeOffset])
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octetCount := int(rawPacket[sdesOctetCountOffset])
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if sdesTextOffset+octetCount > len(rawPacket) {
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return errPacketTooShort
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}
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txtBytes := rawPacket[sdesTextOffset : sdesTextOffset+octetCount]
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s.Text = string(txtBytes)
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return nil
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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 (s *SourceDescription) DestinationSSRC() []uint32 {
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out := make([]uint32, len(s.Chunks))
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for i, v := range s.Chunks {
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out[i] = v.Source
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}
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return out
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}
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func (s *SourceDescription) String() string {
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out := "Source Description:\n"
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for _, c := range s.Chunks {
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out += fmt.Sprintf("\t%x: %s\n", c.Source, c.Items)
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}
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return out
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}
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