dvb_subtitle/segments/
end_of_display_set.rs

1//! End of Display Set Segment — ETSI EN 300 743 §7.2.6, Table 28 (segment_type 0x80).
2
3use crate::error::{Error, Result};
4use broadcast_common::{Parse, Serialize};
5
6/// The end_of_display_set_segment segment_type.
7pub const SEGMENT_TYPE: u8 = 0x80;
8/// Header: sync_byte(1) + segment_type(1) + page_id(2) + segment_length(2) = 6 bytes. segment_length must be 0.
9pub const HEADER_LEN: usize = 6;
10
11/// End of Display Set Segment.
12#[derive(Debug, Clone, PartialEq, Eq)]
13#[cfg_attr(feature = "serde", derive(serde::Serialize))]
14pub struct EndOfDisplaySetSegment {
15    /// The page_id (from generic segment header).
16    pub page_id: u16,
17}
18
19impl<'a> Parse<'a> for EndOfDisplaySetSegment {
20    type Error = Error;
21
22    fn parse(bytes: &'a [u8]) -> Result<Self> {
23        if bytes.len() < HEADER_LEN {
24            return Err(Error::BufferTooShort {
25                need: HEADER_LEN,
26                have: bytes.len(),
27                what: "end_of_display_set_segment",
28            });
29        }
30        if bytes[1] != SEGMENT_TYPE {
31            return Err(Error::UnknownSegmentType(bytes[1]));
32        }
33        let page_id = u16::from_be_bytes([bytes[2], bytes[3]]);
34        let segment_length = u16::from_be_bytes([bytes[4], bytes[5]]);
35        if segment_length != 0 {
36            return Err(Error::SegmentTooLarge);
37        }
38        Ok(EndOfDisplaySetSegment { page_id })
39    }
40}
41
42impl Serialize for EndOfDisplaySetSegment {
43    type Error = Error;
44
45    fn serialized_len(&self) -> usize {
46        HEADER_LEN
47    }
48
49    fn serialize_into(&self, buf: &mut [u8]) -> core::result::Result<usize, Self::Error> {
50        let len = self.serialized_len();
51        if buf.len() < len {
52            return Err(Error::BufferTooShort {
53                need: len,
54                have: buf.len(),
55                what: "end_of_display_set_segment serialize",
56            });
57        }
58        buf[0] = 0x0F;
59        buf[1] = SEGMENT_TYPE;
60        buf[2..4].copy_from_slice(&self.page_id.to_be_bytes());
61        buf[4..6].copy_from_slice(&0u16.to_be_bytes()); // segment_length = 0
62        Ok(len)
63    }
64}
65
66#[cfg(test)]
67mod tests {
68    use super::*;
69    use broadcast_common::{Parse, Serialize};
70
71    #[test]
72    fn round_trip() {
73        let bytes = [0x0F, 0x80, 0x00, 0x01, 0x00, 0x00];
74        let seg = EndOfDisplaySetSegment::parse(&bytes).unwrap();
75        assert_eq!(seg.page_id, 1);
76        let out = seg.to_bytes();
77        assert_eq!(out, bytes);
78
79        // Biting test: mutation changes output
80        let mut seg2 = seg.clone();
81        seg2.page_id = 5;
82        let out2 = seg2.to_bytes();
83        assert_ne!(out2, bytes);
84        let reparse = EndOfDisplaySetSegment::parse(&out2).unwrap();
85        assert_eq!(reparse.page_id, 5);
86    }
87}
dvb_subtitle/segments/end_of_display_set.rs

dvb_subtitle/segments/
end_of_display_set.rs
