192 lines
7.2 KiB
Go
192 lines
7.2 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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// A ReceiverReport (RR) packet provides reception quality feedback for an RTP stream
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type ReceiverReport struct {
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// The synchronization source identifier for the originator of this RR packet.
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SSRC uint32
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// Zero or more reception report blocks depending on the number of other
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// sources heard by this sender since the last report. Each reception report
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// block conveys statistics on the reception of RTP packets from a
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// single synchronization source.
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Reports []ReceptionReport
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// Extension contains additional, payload-specific information that needs to
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// be reported regularly about the receiver.
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ProfileExtensions []byte
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}
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const (
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ssrcLength = 4
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rrSSRCOffset = headerLength
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rrReportOffset = rrSSRCOffset + ssrcLength
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)
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// Marshal encodes the ReceiverReport in binary
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func (r ReceiverReport) 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| RC | PT=RR=201 | length |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | SSRC of packet sender |
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* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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* report | SSRC_1 (SSRC of first source) |
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* block +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* 1 | fraction lost | cumulative number of packets lost |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | extended highest sequence number received |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | interarrival jitter |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | last SR (LSR) |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | delay since last SR (DLSR) |
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* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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* report | SSRC_2 (SSRC of second source) |
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* block +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* 2 : ... :
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* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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* | profile-specific extensions |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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*/
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rawPacket := make([]byte, r.len())
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packetBody := rawPacket[headerLength:]
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binary.BigEndian.PutUint32(packetBody, r.SSRC)
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for i, rp := range r.Reports {
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data, err := rp.Marshal()
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if err != nil {
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return nil, err
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}
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offset := ssrcLength + receptionReportLength*i
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copy(packetBody[offset:], data)
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}
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if len(r.Reports) > countMax {
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return nil, errTooManyReports
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}
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pe := make([]byte, len(r.ProfileExtensions))
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copy(pe, r.ProfileExtensions)
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// if the length of the profile extensions isn't devisible
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// by 4, we need to pad the end.
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for (len(pe) & 0x3) != 0 {
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pe = append(pe, 0)
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}
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rawPacket = append(rawPacket, pe...)
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hData, err := r.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 ReceiverReport from binary
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func (r *ReceiverReport) 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| RC | PT=RR=201 | length |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | SSRC of packet sender |
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* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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* report | SSRC_1 (SSRC of first source) |
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* block +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* 1 | fraction lost | cumulative number of packets lost |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | extended highest sequence number received |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | interarrival jitter |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | last SR (LSR) |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | delay since last SR (DLSR) |
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* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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* report | SSRC_2 (SSRC of second source) |
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* block +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* 2 : ... :
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* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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* | profile-specific extensions |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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*/
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if len(rawPacket) < (headerLength + ssrcLength) {
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return errPacketTooShort
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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 != TypeReceiverReport {
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return errWrongType
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}
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r.SSRC = binary.BigEndian.Uint32(rawPacket[rrSSRCOffset:])
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for i := rrReportOffset; i < len(rawPacket) && len(r.Reports) < int(h.Count); i += receptionReportLength {
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var rr ReceptionReport
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if err := rr.Unmarshal(rawPacket[i:]); err != nil {
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return err
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}
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r.Reports = append(r.Reports, rr)
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}
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r.ProfileExtensions = rawPacket[rrReportOffset+(len(r.Reports)*receptionReportLength):]
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if uint8(len(r.Reports)) != 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 (r *ReceiverReport) len() int {
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repsLength := 0
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for _, rep := range r.Reports {
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repsLength += rep.len()
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}
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return headerLength + ssrcLength + repsLength
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}
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// Header returns the Header associated with this packet.
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func (r *ReceiverReport) Header() Header {
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return Header{
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Count: uint8(len(r.Reports)),
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Type: TypeReceiverReport,
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Length: uint16((r.len()/4)-1) + uint16(getPadding(len(r.ProfileExtensions))),
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}
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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 (r *ReceiverReport) DestinationSSRC() []uint32 {
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out := make([]uint32, len(r.Reports))
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for i, v := range r.Reports {
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out[i] = v.SSRC
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}
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return out
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}
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func (r ReceiverReport) String() string {
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out := fmt.Sprintf("ReceiverReport from %x\n", r.SSRC)
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out += "\tSSRC \tLost\tLastSequence\n"
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for _, i := range r.Reports {
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out += fmt.Sprintf("\t%x\t%d/%d\t%d\n", i.SSRC, i.FractionLost, i.TotalLost, i.LastSequenceNumber)
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}
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out += fmt.Sprintf("\tProfile Extension Data: %v\n", r.ProfileExtensions)
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return out
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}
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