dvb_si/descriptors/
service_identifier.rs

1//! Service Identifier Descriptor — ETSI TS 102 809 §7.2, Table 39 (tag 0x71).
2//!
3//! Carried in the SDT/service loop to give a service a stable textual
4//! identifier. The body is a run of `textual_service_identifier_bytes`
5//! (ASCII), per ts_102_809_apps.md "Table 39 — Service identifier descriptor"
6//! (PDF p. 62).
7
8use super::descriptor_body;
9use crate::error::{Error, Result};
10use dvb_common::{Parse, Serialize};
11
12/// Descriptor tag for service_identifier_descriptor.
13pub const TAG: u8 = 0x71;
14const HEADER_LEN: usize = 2;
15
16/// Service Identifier Descriptor.
17#[derive(Debug, Clone, PartialEq, Eq)]
18#[cfg_attr(feature = "serde", derive(serde::Serialize))]
19#[cfg_attr(feature = "yoke", derive(yoke::Yokeable))]
20pub struct ServiceIdentifierDescriptor<'a> {
21    /// Raw textual_service_identifier bytes (ASCII).
22    pub textual_service_identifier: &'a [u8],
23}
24
25impl<'a> Parse<'a> for ServiceIdentifierDescriptor<'a> {
26    type Error = crate::error::Error;
27    fn parse(bytes: &'a [u8]) -> Result<Self> {
28        let body = descriptor_body(
29            bytes,
30            TAG,
31            "ServiceIdentifierDescriptor",
32            "unexpected tag for service_identifier_descriptor",
33        )?;
34        Ok(Self {
35            textual_service_identifier: body,
36        })
37    }
38}
39
40impl Serialize for ServiceIdentifierDescriptor<'_> {
41    type Error = crate::error::Error;
42    fn serialized_len(&self) -> usize {
43        HEADER_LEN + self.textual_service_identifier.len()
44    }
45
46    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
47        if self.textual_service_identifier.len() > u8::MAX as usize {
48            return Err(Error::InvalidDescriptor {
49                tag: TAG,
50                reason: "textual_service_identifier exceeds 255 bytes",
51            });
52        }
53        let len = self.serialized_len();
54        if buf.len() < len {
55            return Err(Error::OutputBufferTooSmall {
56                need: len,
57                have: buf.len(),
58            });
59        }
60        buf[0] = TAG;
61        buf[1] = self.textual_service_identifier.len() as u8;
62        buf[HEADER_LEN..len].copy_from_slice(self.textual_service_identifier);
63        Ok(len)
64    }
65}
66impl<'a> crate::traits::DescriptorDef<'a> for ServiceIdentifierDescriptor<'a> {
67    const TAG: u8 = TAG;
68    const NAME: &'static str = "SERVICE_IDENTIFIER";
69}
70
71#[cfg(test)]
72mod tests {
73    use super::*;
74
75    #[test]
76    fn parse_extracts_identifier_bytes() {
77        let bytes = [TAG, 6, b'B', b'B', b'C', b'O', b'N', b'E'];
78        let d = ServiceIdentifierDescriptor::parse(&bytes).unwrap();
79        assert_eq!(d.textual_service_identifier, b"BBCONE");
80    }
81
82    #[test]
83    fn parse_rejects_wrong_tag() {
84        assert!(matches!(
85            ServiceIdentifierDescriptor::parse(&[0x70, 1, 0]).unwrap_err(),
86            Error::InvalidDescriptor { tag: 0x70, .. }
87        ));
88    }
89
90    #[test]
91    fn parse_rejects_short_header() {
92        assert!(matches!(
93            ServiceIdentifierDescriptor::parse(&[TAG]).unwrap_err(),
94            Error::BufferTooShort { .. }
95        ));
96    }
97
98    #[test]
99    fn parse_rejects_length_overrunning_buffer() {
100        let bytes = [TAG, 5, 1, 2, 3];
101        assert!(matches!(
102            ServiceIdentifierDescriptor::parse(&bytes).unwrap_err(),
103            Error::BufferTooShort { .. }
104        ));
105    }
106
107    #[test]
108    fn empty_identifier_is_valid() {
109        let bytes = [TAG, 0];
110        let d = ServiceIdentifierDescriptor::parse(&bytes).unwrap();
111        assert!(d.textual_service_identifier.is_empty());
112    }
113
114    #[test]
115    fn serialize_round_trip() {
116        let d = ServiceIdentifierDescriptor {
117            textual_service_identifier: b"CH4-HD",
118        };
119        let mut buf = vec![0u8; d.serialized_len()];
120        d.serialize_into(&mut buf).unwrap();
121        assert_eq!(ServiceIdentifierDescriptor::parse(&buf).unwrap(), d);
122    }
123
124    #[test]
125    fn serialize_rejects_too_small_buffer() {
126        let d = ServiceIdentifierDescriptor {
127            textual_service_identifier: b"test",
128        };
129        let mut buf = vec![0u8; 1];
130        assert!(matches!(
131            d.serialize_into(&mut buf).unwrap_err(),
132            Error::OutputBufferTooSmall { .. }
133        ));
134    }
135
136    #[cfg(feature = "serde")]
137    #[test]
138    fn serde_serializes_to_stable_json() {
139        // Borrowed `&[u8]` cannot deserialize from a JSON number array (serde
140        // has no JSON byte type), so we assert the Serialize impl is wired and
141        // emits stable, re-parseable JSON rather than attempting a borrow
142        // round-trip through JSON.
143        let d = ServiceIdentifierDescriptor {
144            textual_service_identifier: b"ITV1",
145        };
146        let j = serde_json::to_string(&d).unwrap();
147        // Valid, re-parseable JSON (key order is map-defined, so we do not
148        // assert byte-for-byte string stability).
149        let _v: serde_json::Value = serde_json::from_str(&j).unwrap();
150        assert!(j.contains("textual_service_identifier"));
151    }
152}
dvb_si/descriptors/service_identifier.rs

dvb_si/descriptors/
service_identifier.rs
