dvb_si/descriptors/
enhanced_ac3.rs

1//! Enhanced AC-3 Descriptor — ETSI EN 300 468 Annex D (tag 0x7A).
2//!
3//! Same flags-and-fields layout as AC-3 plus two extra bits
4//! (mixinfoexists, substream ids). A simpler subset is modelled here; the
5//! descriptor body beyond the documented flags is retained as raw bytes.
6
7use crate::error::{Error, Result};
8use crate::traits::Descriptor;
9use dvb_common::{Parse, Serialize};
10
11/// Descriptor tag for Enhanced AC-3 (E-AC-3, Dolby Digital Plus).
12pub const TAG: u8 = 0x7A;
13const HEADER_LEN: usize = 2;
14
15/// Enhanced AC-3 Descriptor. Body is opaque for this subset — full Annex D
16/// parsing is deferred; we preserve the bytes verbatim.
17#[derive(Debug, Clone, PartialEq, Eq)]
18#[cfg_attr(feature = "serde", derive(serde::Serialize))]
19#[cfg_attr(feature = "yoke", derive(yoke::Yokeable))]
20pub struct EnhancedAc3Descriptor<'a> {
21    /// Raw payload (everything after the 2-byte header).
22    pub body: &'a [u8],
23}
24
25impl<'a> Parse<'a> for EnhancedAc3Descriptor<'a> {
26    type Error = crate::error::Error;
27    fn parse(bytes: &'a [u8]) -> Result<Self> {
28        if bytes.len() < HEADER_LEN {
29            return Err(Error::BufferTooShort {
30                need: HEADER_LEN,
31                have: bytes.len(),
32                what: "EnhancedAc3Descriptor header",
33            });
34        }
35        if bytes[0] != TAG {
36            return Err(Error::InvalidDescriptor {
37                tag: bytes[0],
38                reason: "unexpected tag for EAC-3 descriptor",
39            });
40        }
41        let length = bytes[1] as usize;
42        let end = HEADER_LEN + length;
43        if bytes.len() < end {
44            return Err(Error::BufferTooShort {
45                need: end,
46                have: bytes.len(),
47                what: "EnhancedAc3Descriptor body",
48            });
49        }
50        Ok(Self {
51            body: &bytes[HEADER_LEN..end],
52        })
53    }
54}
55
56impl Serialize for EnhancedAc3Descriptor<'_> {
57    type Error = crate::error::Error;
58    fn serialized_len(&self) -> usize {
59        HEADER_LEN + self.body.len()
60    }
61
62    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
63        let len = self.serialized_len();
64        if buf.len() < len {
65            return Err(Error::OutputBufferTooSmall {
66                need: len,
67                have: buf.len(),
68            });
69        }
70        buf[0] = TAG;
71        buf[1] = self.body.len() as u8;
72        buf[HEADER_LEN..len].copy_from_slice(self.body);
73        Ok(len)
74    }
75}
76
77impl<'a> Descriptor<'a> for EnhancedAc3Descriptor<'a> {
78    const TAG: u8 = TAG;
79    fn descriptor_length(&self) -> u8 {
80        self.body.len() as u8
81    }
82}
83
84impl<'a> crate::traits::DescriptorDef<'a> for EnhancedAc3Descriptor<'a> {
85    const TAG: u8 = TAG;
86    const NAME: &'static str = "ENHANCED_AC3";
87}
88
89#[cfg(test)]
90mod tests {
91    use super::*;
92
93    #[test]
94    fn parse_extracts_body() {
95        let bytes = [TAG, 3, 0xAA, 0xBB, 0xCC];
96        let d = EnhancedAc3Descriptor::parse(&bytes).unwrap();
97        assert_eq!(d.body, &[0xAA, 0xBB, 0xCC]);
98    }
99
100    #[test]
101    fn parse_rejects_wrong_tag() {
102        assert!(matches!(
103            EnhancedAc3Descriptor::parse(&[0x6A, 0]).unwrap_err(),
104            Error::InvalidDescriptor { tag: 0x6A, .. }
105        ));
106    }
107
108    #[test]
109    fn parse_rejects_short_buffer() {
110        assert!(matches!(
111            EnhancedAc3Descriptor::parse(&[TAG]).unwrap_err(),
112            Error::BufferTooShort { .. }
113        ));
114    }
115
116    #[test]
117    fn serialize_round_trip() {
118        let d = EnhancedAc3Descriptor {
119            body: &[0x01, 0x02, 0x03],
120        };
121        let mut buf = vec![0u8; d.serialized_len()];
122        d.serialize_into(&mut buf).unwrap();
123        assert_eq!(EnhancedAc3Descriptor::parse(&buf).unwrap(), d);
124    }
125
126    #[test]
127    fn empty_body_valid() {
128        let d = EnhancedAc3Descriptor::parse(&[TAG, 0]).unwrap();
129        assert_eq!(d.body, &[] as &[u8]);
130    }
131}
dvb_si/descriptors/enhanced_ac3.rs

dvb_si/descriptors/
enhanced_ac3.rs
