dvb_si/descriptors/
iso_639_language.rs

1//! ISO 639 Language Descriptor — MPEG-2 ISO/IEC 13818-1 §2.6.19 (tag 0x0A).
2
3use super::descriptor_body;
4use crate::error::{Error, Result};
5use crate::text::LangCode;
6use dvb_common::{Parse, Serialize};
7
8/// Descriptor tag for iso_639_language_descriptor.
9pub const TAG: u8 = 0x0A;
10const HEADER_LEN: usize = 2;
11const ENTRY_LEN: usize = 4;
12
13/// One (language code, audio type) pair.
14#[derive(Debug, Clone, PartialEq, Eq)]
15#[cfg_attr(feature = "serde", derive(serde::Serialize))]
16pub struct LanguageEntry {
17    /// Three-character ISO 639-2 language code (e.g. `LangCode(*b"eng")`).
18    pub language_code: LangCode,
19    /// Audio type (ETSI EN 300 468 §6.2.22): 0 = undefined, 1 = clean effects,
20    /// 2 = hearing impaired, 3 = visual impaired commentary.
21    pub audio_type: u8,
22}
23
24/// ISO 639 Language Descriptor.
25#[derive(Debug, Clone, PartialEq, Eq)]
26#[cfg_attr(feature = "serde", derive(serde::Serialize))]
27pub struct Iso639LanguageDescriptor {
28    /// One or more language entries.
29    pub entries: Vec<LanguageEntry>,
30}
31
32impl<'a> Parse<'a> for Iso639LanguageDescriptor {
33    type Error = crate::error::Error;
34    fn parse(bytes: &'a [u8]) -> Result<Self> {
35        let body = descriptor_body(
36            bytes,
37            TAG,
38            "Iso639LanguageDescriptor",
39            "unexpected tag for iso_639_language_descriptor",
40        )?;
41        if body.len() % ENTRY_LEN != 0 {
42            return Err(Error::InvalidDescriptor {
43                tag: TAG,
44                reason: "iso_639_language_descriptor length not a multiple of 4",
45            });
46        }
47        let mut entries = Vec::with_capacity(body.len() / ENTRY_LEN);
48        for chunk in body.chunks_exact(ENTRY_LEN) {
49            entries.push(LanguageEntry {
50                language_code: LangCode([chunk[0], chunk[1], chunk[2]]),
51                audio_type: chunk[3],
52            });
53        }
54        Ok(Self { entries })
55    }
56}
57
58impl Serialize for Iso639LanguageDescriptor {
59    type Error = crate::error::Error;
60    fn serialized_len(&self) -> usize {
61        HEADER_LEN + self.entries.len() * ENTRY_LEN
62    }
63
64    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
65        let len = self.serialized_len();
66        if buf.len() < len {
67            return Err(Error::OutputBufferTooSmall {
68                need: len,
69                have: buf.len(),
70            });
71        }
72        buf[0] = TAG;
73        buf[1] = (self.entries.len() * ENTRY_LEN) as u8;
74        let mut pos = HEADER_LEN;
75        for e in &self.entries {
76            buf[pos..pos + 3].copy_from_slice(&e.language_code.0);
77            buf[pos + 3] = e.audio_type;
78            pos += ENTRY_LEN;
79        }
80        Ok(len)
81    }
82}
83impl<'a> crate::traits::DescriptorDef<'a> for Iso639LanguageDescriptor {
84    const TAG: u8 = TAG;
85    const NAME: &'static str = "ISO_639_LANGUAGE";
86}
87
88#[cfg(test)]
89mod tests {
90    use super::*;
91
92    #[test]
93    fn parse_single_language_entry() {
94        let bytes = [TAG, 4, b'e', b'n', b'g', 0x00];
95        let d = Iso639LanguageDescriptor::parse(&bytes).unwrap();
96        assert_eq!(d.entries.len(), 1);
97        assert_eq!(d.entries[0].language_code, LangCode(*b"eng"));
98        assert_eq!(d.entries[0].audio_type, 0);
99    }
100
101    #[test]
102    fn parse_multiple_entries() {
103        let bytes = [TAG, 8, b'e', b'n', b'g', 1, b'f', b'r', b'a', 2];
104        let d = Iso639LanguageDescriptor::parse(&bytes).unwrap();
105        assert_eq!(d.entries.len(), 2);
106        assert_eq!(d.entries[1].language_code, LangCode(*b"fra"));
107        assert_eq!(d.entries[1].audio_type, 2);
108    }
109
110    #[test]
111    fn parse_rejects_wrong_tag() {
112        let err = Iso639LanguageDescriptor::parse(&[0x0B, 0]).unwrap_err();
113        assert!(matches!(err, Error::InvalidDescriptor { tag: 0x0B, .. }));
114    }
115
116    #[test]
117    fn parse_rejects_short_header() {
118        let err = Iso639LanguageDescriptor::parse(&[TAG]).unwrap_err();
119        assert!(matches!(err, Error::BufferTooShort { .. }));
120    }
121
122    #[test]
123    fn parse_rejects_length_not_multiple_of_4() {
124        let bytes = [TAG, 5, b'e', b'n', b'g', 0, 0];
125        let err = Iso639LanguageDescriptor::parse(&bytes).unwrap_err();
126        assert!(matches!(err, Error::InvalidDescriptor { .. }));
127    }
128
129    #[test]
130    fn serialize_round_trip() {
131        let d = Iso639LanguageDescriptor {
132            entries: vec![
133                LanguageEntry {
134                    language_code: LangCode(*b"eng"),
135                    audio_type: 0,
136                },
137                LanguageEntry {
138                    language_code: LangCode(*b"fra"),
139                    audio_type: 1,
140                },
141            ],
142        };
143        let mut buf = vec![0u8; d.serialized_len()];
144        d.serialize_into(&mut buf).unwrap();
145        let re = Iso639LanguageDescriptor::parse(&buf).unwrap();
146        assert_eq!(d, re);
147    }
148
149    #[test]
150    fn descriptor_length_matches_payload() {
151        let d = Iso639LanguageDescriptor {
152            entries: vec![LanguageEntry {
153                language_code: LangCode(*b"eng"),
154                audio_type: 0,
155            }],
156        };
157        assert_eq!(d.serialized_len() - 2, 4);
158    }
159}
dvb_si/descriptors/iso_639_language.rs

dvb_si/descriptors/
iso_639_language.rs
