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

dvb_si/descriptors/
iso_639_language.rs
