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 alloc::vec::Vec;
7use dvb_common::{Parse, Serialize};
8
9/// Descriptor tag for iso_639_language_descriptor.
10pub const TAG: u8 = 0x0A;
11const HEADER_LEN: usize = 2;
12const ENTRY_LEN: usize = 4;
13
14/// Audio type — ISO/IEC 13818-1 §2.6.19 Table 2-63.
15#[derive(Debug, Clone, Copy, PartialEq, Eq)]
16#[cfg_attr(feature = "serde", derive(serde::Serialize))]
17#[non_exhaustive]
18pub enum AudioType {
19    /// 0x00 — undefined.
20    Undefined,
21    /// 0x01 — clean effects.
22    CleanEffects,
23    /// 0x02 — hearing impaired.
24    HearingImpaired,
25    /// 0x03 — visual impaired commentary.
26    VisualImpairedCommentary,
27    /// 0x04–0x7F — user private.
28    UserPrivate(u8),
29    /// 0x80 — primary.
30    Primary,
31    /// 0x81 — native.
32    Native,
33    /// 0x82 — emergency.
34    Emergency,
35    /// 0x83 — primary commentary.
36    PrimaryCommentary,
37    /// 0x84 — alternate commentary.
38    AlternateCommentary,
39    /// 0x85–0xFF — reserved.
40    Reserved(u8),
41}
42
43impl AudioType {
44    #[must_use]
45    /// Creates a value from a wire byte, preserving every possible
46    /// byte value for lossless round-trip.
47    pub fn from_u8(v: u8) -> Self {
48        match v {
49            0x00 => Self::Undefined,
50            0x01 => Self::CleanEffects,
51            0x02 => Self::HearingImpaired,
52            0x03 => Self::VisualImpairedCommentary,
53            0x04..=0x7F => Self::UserPrivate(v),
54            0x80 => Self::Primary,
55            0x81 => Self::Native,
56            0x82 => Self::Emergency,
57            0x83 => Self::PrimaryCommentary,
58            0x84 => Self::AlternateCommentary,
59            v => Self::Reserved(v),
60        }
61    }
62
63    #[must_use]
64    /// Returns the wire byte for this value.
65    pub fn to_u8(self) -> u8 {
66        match self {
67            Self::Undefined => 0x00,
68            Self::CleanEffects => 0x01,
69            Self::HearingImpaired => 0x02,
70            Self::VisualImpairedCommentary => 0x03,
71            Self::UserPrivate(v) => v,
72            Self::Primary => 0x80,
73            Self::Native => 0x81,
74            Self::Emergency => 0x82,
75            Self::PrimaryCommentary => 0x83,
76            Self::AlternateCommentary => 0x84,
77            Self::Reserved(v) => v,
78        }
79    }
80
81    #[must_use]
82    /// Returns a human-readable spec name for this value.
83    pub fn name(self) -> &'static str {
84        match self {
85            Self::Undefined => "undefined",
86            Self::CleanEffects => "clean effects",
87            Self::HearingImpaired => "hearing impaired",
88            Self::VisualImpairedCommentary => "visual impaired commentary",
89            Self::UserPrivate(_) => "user private",
90            Self::Primary => "primary",
91            Self::Native => "native",
92            Self::Emergency => "emergency",
93            Self::PrimaryCommentary => "primary commentary",
94            Self::AlternateCommentary => "alternate commentary",
95            Self::Reserved(_) => "reserved",
96        }
97    }
98}
99dvb_common::impl_spec_display!(AudioType, UserPrivate, Reserved);
100
101/// One (language code, audio type) pair.
102#[derive(Debug, Clone, PartialEq, Eq)]
103#[cfg_attr(feature = "serde", derive(serde::Serialize))]
104pub struct LanguageEntry {
105    /// Three-character ISO 639-2 language code (e.g. `LangCode(*b"eng")`).
106    pub language_code: LangCode,
107    /// Audio type (ETSI EN 300 468 §6.2.22).
108    pub audio_type: AudioType,
109}
110
111/// ISO 639 Language Descriptor.
112#[derive(Debug, Clone, PartialEq, Eq)]
113#[cfg_attr(feature = "serde", derive(serde::Serialize))]
114pub struct Iso639LanguageDescriptor {
115    /// One or more language entries.
116    pub entries: Vec<LanguageEntry>,
117}
118
119impl<'a> Parse<'a> for Iso639LanguageDescriptor {
120    type Error = crate::error::Error;
121    fn parse(bytes: &'a [u8]) -> Result<Self> {
122        let body = descriptor_body(
123            bytes,
124            TAG,
125            "Iso639LanguageDescriptor",
126            "unexpected tag for iso_639_language_descriptor",
127        )?;
128        if body.len() % ENTRY_LEN != 0 {
129            return Err(Error::InvalidDescriptor {
130                tag: TAG,
131                reason: "iso_639_language_descriptor length not a multiple of 4",
132            });
133        }
134        let mut entries = Vec::with_capacity(body.len() / ENTRY_LEN);
135        for chunk in body.chunks_exact(ENTRY_LEN) {
136            entries.push(LanguageEntry {
137                language_code: LangCode([chunk[0], chunk[1], chunk[2]]),
138                audio_type: AudioType::from_u8(chunk[3]),
139            });
140        }
141        Ok(Self { entries })
142    }
143}
144
145impl Serialize for Iso639LanguageDescriptor {
146    type Error = crate::error::Error;
147    fn serialized_len(&self) -> usize {
148        HEADER_LEN + self.entries.len() * ENTRY_LEN
149    }
150
151    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
152        let len = self.serialized_len();
153        if buf.len() < len {
154            return Err(Error::OutputBufferTooSmall {
155                need: len,
156                have: buf.len(),
157            });
158        }
159        buf[0] = TAG;
160        buf[1] = (self.entries.len() * ENTRY_LEN) as u8;
161        let mut pos = HEADER_LEN;
162        for e in &self.entries {
163            buf[pos..pos + 3].copy_from_slice(&e.language_code.0);
164            buf[pos + 3] = e.audio_type.to_u8();
165            pos += ENTRY_LEN;
166        }
167        Ok(len)
168    }
169}
170impl<'a> crate::traits::DescriptorDef<'a> for Iso639LanguageDescriptor {
171    const TAG: u8 = TAG;
172    const NAME: &'static str = "ISO_639_LANGUAGE";
173}
174
175#[cfg(test)]
176mod tests {
177    use super::*;
178
179    #[test]
180    fn parse_single_language_entry() {
181        let bytes = [TAG, 4, b'e', b'n', b'g', 0x00];
182        let d = Iso639LanguageDescriptor::parse(&bytes).unwrap();
183        assert_eq!(d.entries.len(), 1);
184        assert_eq!(d.entries[0].language_code, LangCode(*b"eng"));
185        assert_eq!(d.entries[0].audio_type, AudioType::Undefined);
186    }
187
188    #[test]
189    fn parse_multiple_entries() {
190        let bytes = [TAG, 8, b'e', b'n', b'g', 1, b'f', b'r', b'a', 2];
191        let d = Iso639LanguageDescriptor::parse(&bytes).unwrap();
192        assert_eq!(d.entries.len(), 2);
193        assert_eq!(d.entries[1].language_code, LangCode(*b"fra"));
194        assert_eq!(d.entries[1].audio_type, AudioType::HearingImpaired);
195    }
196
197    #[test]
198    fn parse_rejects_wrong_tag() {
199        let err = Iso639LanguageDescriptor::parse(&[0x0B, 0]).unwrap_err();
200        assert!(matches!(err, Error::InvalidDescriptor { tag: 0x0B, .. }));
201    }
202
203    #[test]
204    fn parse_rejects_short_header() {
205        let err = Iso639LanguageDescriptor::parse(&[TAG]).unwrap_err();
206        assert!(matches!(err, Error::BufferTooShort { .. }));
207    }
208
209    #[test]
210    fn parse_rejects_length_not_multiple_of_4() {
211        let bytes = [TAG, 5, b'e', b'n', b'g', 0, 0];
212        let err = Iso639LanguageDescriptor::parse(&bytes).unwrap_err();
213        assert!(matches!(err, Error::InvalidDescriptor { .. }));
214    }
215
216    #[test]
217    fn serialize_round_trip() {
218        let d = Iso639LanguageDescriptor {
219            entries: vec![
220                LanguageEntry {
221                    language_code: LangCode(*b"eng"),
222                    audio_type: AudioType::Undefined,
223                },
224                LanguageEntry {
225                    language_code: LangCode(*b"fra"),
226                    audio_type: AudioType::CleanEffects,
227                },
228            ],
229        };
230        let mut buf = vec![0u8; d.serialized_len()];
231        d.serialize_into(&mut buf).unwrap();
232        let re = Iso639LanguageDescriptor::parse(&buf).unwrap();
233        assert_eq!(d, re);
234    }
235
236    #[test]
237    fn descriptor_length_matches_payload() {
238        let d = Iso639LanguageDescriptor {
239            entries: vec![LanguageEntry {
240                language_code: LangCode(*b"eng"),
241                audio_type: AudioType::Undefined,
242            }],
243        };
244        assert_eq!(d.serialized_len() - 2, 4);
245    }
246
247    #[test]
248    fn audio_type_full_range_round_trip() {
249        for b in 0..=0xFF_u8 {
250            let at = AudioType::from_u8(b);
251            assert_eq!(at.to_u8(), b, "round-trip failed for byte 0x{b:02X}");
252        }
253    }
254
255    #[test]
256    fn audio_type_name_for_known() {
257        assert_eq!(AudioType::Undefined.name(), "undefined");
258        assert_eq!(AudioType::CleanEffects.name(), "clean effects");
259        assert_eq!(AudioType::HearingImpaired.name(), "hearing impaired");
260        assert_eq!(
261            AudioType::VisualImpairedCommentary.name(),
262            "visual impaired commentary"
263        );
264        assert_eq!(AudioType::Reserved(0x55).name(), "reserved");
265    }
266
267    #[test]
268    fn audio_type_round_trip_known_values() {
269        for b in [0x00u8, 0x03, 0x40, 0x80, 0x84, 0x85, 0xFF] {
270            assert_eq!(
271                AudioType::from_u8(b).to_u8(),
272                b,
273                "round-trip failed for byte 0x{b:02X}"
274            );
275        }
276    }
277
278    #[test]
279    fn audio_type_primary_name() {
280        assert_eq!(AudioType::from_u8(0x80).name(), "primary");
281    }
282}
dvb_si/descriptors/iso_639_language.rs

dvb_si/descriptors/
iso_639_language.rs
