154 lines
3.5 KiB
Go
154 lines
3.5 KiB
Go
package rtcp
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import (
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"fmt"
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"strings"
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)
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// A CompoundPacket is a collection of RTCP packets transmitted as a single packet with
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// the underlying protocol (for example UDP).
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//
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// To maximize the resolution of receiption statistics, the first Packet in a CompoundPacket
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// must always be either a SenderReport or a ReceiverReport. This is true even if no data
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// has been sent or received, in which case an empty ReceiverReport must be sent, and even
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// if the only other RTCP packet in the compound packet is a Goodbye.
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//
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// Next, a SourceDescription containing a CNAME item must be included in each CompoundPacket
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// to identify the source and to begin associating media for purposes such as lip-sync.
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//
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// Other RTCP packet types may follow in any order. Packet types may appear more than once.
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type CompoundPacket []Packet
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// Validate returns an error if this is not an RFC-compliant CompoundPacket.
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func (c CompoundPacket) Validate() error {
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if len(c) == 0 {
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return errEmptyCompound
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}
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// SenderReport and ReceiverReport are the only types that
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// are allowed to be the first packet in a compound datagram
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switch c[0].(type) {
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case *SenderReport, *ReceiverReport:
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// ok
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default:
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return errBadFirstPacket
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}
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for _, pkt := range c[1:] {
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switch p := pkt.(type) {
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// If the number of RecetpionReports exceeds 31 additional ReceiverReports
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// can be included here.
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case *ReceiverReport:
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continue
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// A SourceDescription containing a CNAME must be included in every
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// CompoundPacket.
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case *SourceDescription:
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var hasCNAME bool
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for _, c := range p.Chunks {
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for _, it := range c.Items {
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if it.Type == SDESCNAME {
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hasCNAME = true
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}
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}
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}
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if !hasCNAME {
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return errMissingCNAME
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}
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return nil
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// Other packets are not permitted before the CNAME
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default:
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return errPacketBeforeCNAME
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}
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}
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// CNAME never reached
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return errMissingCNAME
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}
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// CNAME returns the CNAME that *must* be present in every CompoundPacket
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func (c CompoundPacket) CNAME() (string, error) {
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var err error
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if len(c) < 1 {
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return "", errEmptyCompound
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}
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for _, pkt := range c[1:] {
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sdes, ok := pkt.(*SourceDescription)
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if ok {
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for _, c := range sdes.Chunks {
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for _, it := range c.Items {
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if it.Type == SDESCNAME {
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return it.Text, err
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}
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}
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}
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} else {
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_, ok := pkt.(*ReceiverReport)
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if !ok {
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err = errPacketBeforeCNAME
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}
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}
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}
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return "", errMissingCNAME
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}
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// Marshal encodes the CompoundPacket as binary.
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func (c CompoundPacket) Marshal() ([]byte, error) {
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if err := c.Validate(); err != nil {
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return nil, err
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}
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p := []Packet(c)
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return Marshal(p)
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}
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// Unmarshal decodes a CompoundPacket from binary.
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func (c *CompoundPacket) Unmarshal(rawData []byte) error {
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out := make(CompoundPacket, 0)
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for len(rawData) != 0 {
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p, processed, err := unmarshal(rawData)
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if err != nil {
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return err
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}
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out = append(out, p)
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rawData = rawData[processed:]
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}
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*c = out
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if err := c.Validate(); err != nil {
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return err
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}
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return nil
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}
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// DestinationSSRC returns the synchronization sources associated with this
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// CompoundPacket's reception report.
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func (c CompoundPacket) DestinationSSRC() []uint32 {
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if len(c) == 0 {
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return nil
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}
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return c[0].DestinationSSRC()
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}
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func (c CompoundPacket) String() string {
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out := "CompoundPacket\n"
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for _, p := range c {
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stringer, canString := p.(fmt.Stringer)
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if canString {
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out += stringer.String()
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} else {
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out += stringify(p)
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}
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}
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out = strings.TrimSuffix(strings.ReplaceAll(out, "\n", "\n\t"), "\t")
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return out
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}
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