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 crate::error::{Error, Result};
4use crate::text::LangCode;
5use crate::traits::Descriptor;
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        if bytes.len() < HEADER_LEN {
36            return Err(Error::BufferTooShort {
37                need: HEADER_LEN,
38                have: bytes.len(),
39                what: "Iso639LanguageDescriptor header",
40            });
41        }
42        if bytes[0] != TAG {
43            return Err(Error::InvalidDescriptor {
44                tag: bytes[0],
45                reason: "unexpected tag for iso_639_language_descriptor",
46            });
47        }
48        let length = bytes[1] as usize;
49        if bytes.len() < HEADER_LEN + length {
50            return Err(Error::BufferTooShort {
51                need: HEADER_LEN + length,
52                have: bytes.len(),
53                what: "Iso639LanguageDescriptor body",
54            });
55        }
56        let body = &bytes[HEADER_LEN..HEADER_LEN + length];
57        if body.len() % ENTRY_LEN != 0 {
58            return Err(Error::InvalidDescriptor {
59                tag: TAG,
60                reason: "iso_639_language_descriptor length not a multiple of 4",
61            });
62        }
63        let mut entries = Vec::with_capacity(body.len() / ENTRY_LEN);
64        for chunk in body.chunks_exact(ENTRY_LEN) {
65            entries.push(LanguageEntry {
66                language_code: LangCode([chunk[0], chunk[1], chunk[2]]),
67                audio_type: chunk[3],
68            });
69        }
70        Ok(Self { entries })
71    }
72}
73
74impl Serialize for Iso639LanguageDescriptor {
75    type Error = crate::error::Error;
76    fn serialized_len(&self) -> usize {
77        HEADER_LEN + self.entries.len() * ENTRY_LEN
78    }
79
80    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
81        let len = self.serialized_len();
82        if buf.len() < len {
83            return Err(Error::OutputBufferTooSmall {
84                need: len,
85                have: buf.len(),
86            });
87        }
88        buf[0] = TAG;
89        buf[1] = (self.entries.len() * ENTRY_LEN) as u8;
90        let mut pos = HEADER_LEN;
91        for e in &self.entries {
92            buf[pos..pos + 3].copy_from_slice(&e.language_code.0);
93            buf[pos + 3] = e.audio_type;
94            pos += ENTRY_LEN;
95        }
96        Ok(len)
97    }
98}
99
100impl<'a> Descriptor<'a> for Iso639LanguageDescriptor {
101    const TAG: u8 = TAG;
102    fn descriptor_length(&self) -> u8 {
103        (self.entries.len() * ENTRY_LEN) as u8
104    }
105}
106
107impl<'a> crate::traits::DescriptorDef<'a> for Iso639LanguageDescriptor {
108    const TAG: u8 = TAG;
109    const NAME: &'static str = "ISO_639_LANGUAGE";
110}
111
112#[cfg(test)]
113mod tests {
114    use super::*;
115
116    #[test]
117    fn parse_single_language_entry() {
118        let bytes = [TAG, 4, b'e', b'n', b'g', 0x00];
119        let d = Iso639LanguageDescriptor::parse(&bytes).unwrap();
120        assert_eq!(d.entries.len(), 1);
121        assert_eq!(d.entries[0].language_code, LangCode(*b"eng"));
122        assert_eq!(d.entries[0].audio_type, 0);
123    }
124
125    #[test]
126    fn parse_multiple_entries() {
127        let bytes = [TAG, 8, b'e', b'n', b'g', 1, b'f', b'r', b'a', 2];
128        let d = Iso639LanguageDescriptor::parse(&bytes).unwrap();
129        assert_eq!(d.entries.len(), 2);
130        assert_eq!(d.entries[1].language_code, LangCode(*b"fra"));
131        assert_eq!(d.entries[1].audio_type, 2);
132    }
133
134    #[test]
135    fn parse_rejects_wrong_tag() {
136        let err = Iso639LanguageDescriptor::parse(&[0x0B, 0]).unwrap_err();
137        assert!(matches!(err, Error::InvalidDescriptor { tag: 0x0B, .. }));
138    }
139
140    #[test]
141    fn parse_rejects_short_header() {
142        let err = Iso639LanguageDescriptor::parse(&[TAG]).unwrap_err();
143        assert!(matches!(err, Error::BufferTooShort { .. }));
144    }
145
146    #[test]
147    fn parse_rejects_length_not_multiple_of_4() {
148        let bytes = [TAG, 5, b'e', b'n', b'g', 0, 0];
149        let err = Iso639LanguageDescriptor::parse(&bytes).unwrap_err();
150        assert!(matches!(err, Error::InvalidDescriptor { .. }));
151    }
152
153    #[test]
154    fn serialize_round_trip() {
155        let d = Iso639LanguageDescriptor {
156            entries: vec![
157                LanguageEntry {
158                    language_code: LangCode(*b"eng"),
159                    audio_type: 0,
160                },
161                LanguageEntry {
162                    language_code: LangCode(*b"fra"),
163                    audio_type: 1,
164                },
165            ],
166        };
167        let mut buf = vec![0u8; d.serialized_len()];
168        d.serialize_into(&mut buf).unwrap();
169        let re = Iso639LanguageDescriptor::parse(&buf).unwrap();
170        assert_eq!(d, re);
171    }
172
173    #[test]
174    fn descriptor_length_matches_payload() {
175        let d = Iso639LanguageDescriptor {
176            entries: vec![LanguageEntry {
177                language_code: LangCode(*b"eng"),
178                audio_type: 0,
179            }],
180        };
181        assert_eq!(d.descriptor_length(), 4);
182    }
183}
dvb_si/descriptors/iso_639_language.rs

dvb_si/descriptors/
iso_639_language.rs
