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use super::{FeedbackMessageType, ReportList, RtcpHeader, RtcpPacket, RtcpType, Ssrc};
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/// RTCP packet BY
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#[derive(Debug, Clone, PartialEq, Eq)]
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pub struct Goodbye {
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    /// The SSRC that are no longer in use.
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    pub reports: ReportList<Ssrc>,
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}
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impl RtcpPacket for Goodbye {
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    fn header(&self) -> RtcpHeader {
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        RtcpHeader {
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            rtcp_type: RtcpType::Goodbye,
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            feedback_message_type: FeedbackMessageType::SourceCount(self.reports.len() as u8),
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            words_less_one: (self.length_words() - 1) as u16,
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        }
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    }
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    fn length_words(&self) -> usize {
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        // each ssrc is one word
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        1 + self.reports.len()
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    }
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    fn write_to(&self, buf: &mut [u8]) -> usize {
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        self.header().write_to(&mut buf[..4]);
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        let buf = &mut buf[4..];
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        for (i, s) in self.reports.iter().enumerate() {
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            buf[i * 4..(i + 1) * 4].copy_from_slice(&s.to_be_bytes());
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        }
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        self.length_words() * 4
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    }
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}
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impl<'a> TryFrom<(usize, &'a [u8])> for Goodbye {
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    type Error = &'static str;
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    fn try_from((count, buf): (usize, &'a [u8])) -> Result<Self, Self::Error> {
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        if buf.len() < 4 {
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            return Err("Less than 4 bytes for Goodbye");
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        }
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        let mut reports = ReportList::new();
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        let mut buf = buf;
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        if buf.len() < count * 4 {
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            return Err("Less than count * 4 bytes for Goodbye");
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        }
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        let max = count.min(31);
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        for _ in 0..max {
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            let ssrc = u32::from_be_bytes([buf[0], buf[1], buf[2], buf[3]]).into();
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            reports.push(ssrc);
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            buf = &buf[4..];
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        }
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        // TODO parse the optional reason string here.
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        Ok(Goodbye { reports })
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    }
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}