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server/vendor/github.com/pion/rtcp/reception_report.go

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+// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
+// SPDX-License-Identifier: MIT
+
+package rtcp
+
+import "encoding/binary"
+
+// A ReceptionReport block conveys statistics on the reception of RTP packets
+// from a single synchronization source.
+type ReceptionReport struct {
+	// The SSRC identifier of the source to which the information in this
+	// reception report block pertains.
+	SSRC uint32
+	// The fraction of RTP data packets from source SSRC lost since the
+	// previous SR or RR packet was sent, expressed as a fixed point
+	// number with the binary point at the left edge of the field.
+	FractionLost uint8
+	// The total number of RTP data packets from source SSRC that have
+	// been lost since the beginning of reception.
+	TotalLost uint32
+	// The low 16 bits contain the highest sequence number received in an
+	// RTP data packet from source SSRC, and the most significant 16
+	// bits extend that sequence number with the corresponding count of
+	// sequence number cycles.
+	LastSequenceNumber uint32
+	// An estimate of the statistical variance of the RTP data packet
+	// interarrival time, measured in timestamp units and expressed as an
+	// unsigned integer.
+	Jitter uint32
+	// The middle 32 bits out of 64 in the NTP timestamp received as part of
+	// the most recent RTCP sender report (SR) packet from source SSRC. If no
+	// SR has been received yet, the field is set to zero.
+	LastSenderReport uint32
+	// The delay, expressed in units of 1/65536 seconds, between receiving the
+	// last SR packet from source SSRC and sending this reception report block.
+	// If no SR packet has been received yet from SSRC, the field is set to zero.
+	Delay uint32
+}
+
+const (
+	receptionReportLength = 24
+	fractionLostOffset    = 4
+	totalLostOffset       = 5
+	lastSeqOffset         = 8
+	jitterOffset          = 12
+	lastSROffset          = 16
+	delayOffset           = 20
+)
+
+// Marshal encodes the ReceptionReport in binary
+func (r ReceptionReport) 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
+	 * +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+	 * |                              SSRC                             |
+	 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	 * | fraction lost |       cumulative number of packets lost       |
+	 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	 * |           extended highest sequence number received           |
+	 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	 * |                      interarrival jitter                      |
+	 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	 * |                         last SR (LSR)                         |
+	 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	 * |                   delay since last SR (DLSR)                  |
+	 * +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+	 */
+
+	rawPacket := make([]byte, receptionReportLength)
+
+	binary.BigEndian.PutUint32(rawPacket, r.SSRC)
+
+	rawPacket[fractionLostOffset] = r.FractionLost
+
+	// pack TotalLost into 24 bits
+	if r.TotalLost >= (1 << 25) {
+		return nil, errInvalidTotalLost
+	}
+	tlBytes := rawPacket[totalLostOffset:]
+	tlBytes[0] = byte(r.TotalLost >> 16)
+	tlBytes[1] = byte(r.TotalLost >> 8)
+	tlBytes[2] = byte(r.TotalLost)
+
+	binary.BigEndian.PutUint32(rawPacket[lastSeqOffset:], r.LastSequenceNumber)
+	binary.BigEndian.PutUint32(rawPacket[jitterOffset:], r.Jitter)
+	binary.BigEndian.PutUint32(rawPacket[lastSROffset:], r.LastSenderReport)
+	binary.BigEndian.PutUint32(rawPacket[delayOffset:], r.Delay)
+
+	return rawPacket, nil
+}
+
+// Unmarshal decodes the ReceptionReport from binary
+func (r *ReceptionReport) Unmarshal(rawPacket []byte) error {
+	if len(rawPacket) < receptionReportLength {
+		return errPacketTooShort
+	}
+
+	/*
+	 *  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
+	 * +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+	 * |                              SSRC                             |
+	 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	 * | fraction lost |       cumulative number of packets lost       |
+	 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	 * |           extended highest sequence number received           |
+	 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	 * |                      interarrival jitter                      |
+	 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	 * |                         last SR (LSR)                         |
+	 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	 * |                   delay since last SR (DLSR)                  |
+	 * +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+	 */
+
+	r.SSRC = binary.BigEndian.Uint32(rawPacket)
+	r.FractionLost = rawPacket[fractionLostOffset]
+
+	tlBytes := rawPacket[totalLostOffset:]
+	r.TotalLost = uint32(tlBytes[2]) | uint32(tlBytes[1])<<8 | uint32(tlBytes[0])<<16
+
+	r.LastSequenceNumber = binary.BigEndian.Uint32(rawPacket[lastSeqOffset:])
+	r.Jitter = binary.BigEndian.Uint32(rawPacket[jitterOffset:])
+	r.LastSenderReport = binary.BigEndian.Uint32(rawPacket[lastSROffset:])
+	r.Delay = binary.BigEndian.Uint32(rawPacket[delayOffset:])
+
+	return nil
+}
+
+func (r *ReceptionReport) len() int {
+	return receptionReportLength
+}