mirror of https://bitbucket.org/ausocean/av.git
77 lines
1.9 KiB
Go
77 lines
1.9 KiB
Go
/*
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NAME
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parse.go
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DESCRIPTION
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parse.go contains functionality for parsing RTCP packets.
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AUTHORS
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Saxon A. Nelson-Milton <saxon@ausocean.org>
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LICENSE
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This is Copyright (C) 2019 the Australian Ocean Lab (AusOcean)
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It is free software: you can redistribute it and/or modify them
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under the terms of the GNU General Public License as published by the
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Free Software Foundation, either version 3 of the License, or (at your
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option) any later version.
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It is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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in gpl.txt. If not, see http://www.gnu.org/licenses.
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*/
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package rtcp
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import (
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"encoding/binary"
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"errors"
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)
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// Timestamp describes an NTP timestamp, see https://tools.ietf.org/html/rfc1305
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type Timestamp struct {
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Seconds uint32
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Fraction uint32
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}
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// ParseTimestamp gets the timestamp from a receiver report and returns it as
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// a Timestamp as defined above. If the given bytes do not represent a valid
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// receiver report, an error is returned.
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func ParseTimestamp(buf []byte) (Timestamp, error) {
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err := checkPacket(buf)
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if err != nil {
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return Timestamp{}, err
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}
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return Timestamp{
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Seconds: binary.BigEndian.Uint32(buf[8:]),
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Fraction: binary.BigEndian.Uint32(buf[12:]),
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}, nil
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}
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func ParseSSRC(buf []byte) (uint32, error) {
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err := checkPacket(buf)
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if err != nil {
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return 0, err
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}
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return binary.BigEndian.Uint32(buf[4:]), nil
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}
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func checkPacket(buf []byte) error {
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if len(buf) < 4 {
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return errors.New("bad RTCP packet, not of sufficient length")
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}
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if (buf[0]&0xc0)>>6 != rtcpVer {
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return errors.New("incompatible RTCP version")
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}
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if buf[1] != typeSenderReport {
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return errors.New("RTCP packet is not of sender report type")
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}
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return nil
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}
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