dvb_si/descriptors/
data_broadcast_id.rs

1//! Data Broadcast Id Descriptor — ETSI EN 300 468 §6.2.13 (tag 0x66).
2//!
3//! Table 32 (PDF p. 72). Identifies the data broadcast specification used by a
4//! data component, plus a raw `id_selector_byte` tail whose interpretation
5//! depends on the `data_broadcast_id` (see ETSI TS 101 162).
6
7use crate::error::{Error, Result};
8use crate::traits::Descriptor;
9use dvb_common::{Parse, Serialize};
10
11/// Descriptor tag for data_broadcast_id_descriptor.
12pub const TAG: u8 = 0x66;
13const HEADER_LEN: usize = 2;
14/// Fixed prefix length: the 16-bit data_broadcast_id (EN 300 468 Table 32).
15const ID_LEN: usize = 2;
16
17/// Data Broadcast Id Descriptor (tag 0x66).
18#[derive(Debug, Clone, PartialEq, Eq)]
19#[cfg_attr(feature = "serde", derive(serde::Serialize))]
20pub struct DataBroadcastIdDescriptor<'a> {
21    /// 16-bit data_broadcast_id (ETSI TS 101 162 registration).
22    pub data_broadcast_id: u16,
23    /// Raw id_selector_byte tail — interpretation depends on data_broadcast_id.
24    pub id_selector: &'a [u8],
25}
26
27impl<'a> Parse<'a> for DataBroadcastIdDescriptor<'a> {
28    type Error = crate::error::Error;
29    fn parse(bytes: &'a [u8]) -> Result<Self> {
30        if bytes.len() < HEADER_LEN {
31            return Err(Error::BufferTooShort {
32                need: HEADER_LEN,
33                have: bytes.len(),
34                what: "DataBroadcastIdDescriptor header",
35            });
36        }
37        if bytes[0] != TAG {
38            return Err(Error::InvalidDescriptor {
39                tag: bytes[0],
40                reason: "unexpected tag for data_broadcast_id_descriptor",
41            });
42        }
43        let length = bytes[1] as usize;
44        let end = HEADER_LEN + length;
45        if bytes.len() < end {
46            return Err(Error::BufferTooShort {
47                need: end,
48                have: bytes.len(),
49                what: "DataBroadcastIdDescriptor body",
50            });
51        }
52        if length < ID_LEN {
53            return Err(Error::InvalidDescriptor {
54                tag: TAG,
55                reason: "data_broadcast_id_descriptor body shorter than 2 bytes",
56            });
57        }
58        let data_broadcast_id = u16::from_be_bytes([bytes[HEADER_LEN], bytes[HEADER_LEN + 1]]);
59        let id_selector = &bytes[HEADER_LEN + ID_LEN..end];
60        Ok(Self {
61            data_broadcast_id,
62            id_selector,
63        })
64    }
65}
66
67impl Serialize for DataBroadcastIdDescriptor<'_> {
68    type Error = crate::error::Error;
69    fn serialized_len(&self) -> usize {
70        HEADER_LEN + ID_LEN + self.id_selector.len()
71    }
72
73    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
74        let len = self.serialized_len();
75        let body = ID_LEN + self.id_selector.len();
76        if body > u8::MAX as usize {
77            return Err(Error::InvalidDescriptor {
78                tag: TAG,
79                reason: "data_broadcast_id_descriptor body exceeds 255 bytes",
80            });
81        }
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] = body as u8;
90        buf[HEADER_LEN..HEADER_LEN + ID_LEN].copy_from_slice(&self.data_broadcast_id.to_be_bytes());
91        let sel_start = HEADER_LEN + ID_LEN;
92        buf[sel_start..sel_start + self.id_selector.len()].copy_from_slice(self.id_selector);
93        Ok(len)
94    }
95}
96
97impl<'a> Descriptor<'a> for DataBroadcastIdDescriptor<'a> {
98    const TAG: u8 = TAG;
99    fn descriptor_length(&self) -> u8 {
100        (ID_LEN + self.id_selector.len()) as u8
101    }
102}
103
104impl<'a> crate::traits::DescriptorDef<'a> for DataBroadcastIdDescriptor<'a> {
105    const TAG: u8 = TAG;
106    const NAME: &'static str = "DATA_BROADCAST_ID";
107}
108
109#[cfg(test)]
110mod tests {
111    use super::*;
112
113    #[test]
114    fn parse_extracts_id_and_selector() {
115        let bytes = [TAG, 0x05, 0x00, 0x0B, 0xAA, 0xBB, 0xCC];
116        let d = DataBroadcastIdDescriptor::parse(&bytes).unwrap();
117        assert_eq!(d.data_broadcast_id, 0x000B);
118        assert_eq!(d.id_selector, &[0xAA, 0xBB, 0xCC]);
119    }
120
121    #[test]
122    fn parse_accepts_empty_selector() {
123        let bytes = [TAG, 0x02, 0x00, 0x0A];
124        let d = DataBroadcastIdDescriptor::parse(&bytes).unwrap();
125        assert_eq!(d.data_broadcast_id, 0x000A);
126        assert!(d.id_selector.is_empty());
127    }
128
129    #[test]
130    fn parse_rejects_wrong_tag() {
131        let err = DataBroadcastIdDescriptor::parse(&[0x65, 0x02, 0x00, 0x0A]).unwrap_err();
132        assert!(matches!(err, Error::InvalidDescriptor { tag: 0x65, .. }));
133    }
134
135    #[test]
136    fn parse_rejects_short_buffer() {
137        let err = DataBroadcastIdDescriptor::parse(&[TAG]).unwrap_err();
138        assert!(matches!(err, Error::BufferTooShort { .. }));
139    }
140
141    #[test]
142    fn parse_rejects_body_too_short() {
143        // length=1: not even the 16-bit id fits.
144        let err = DataBroadcastIdDescriptor::parse(&[TAG, 0x01, 0x00]).unwrap_err();
145        assert!(matches!(err, Error::InvalidDescriptor { .. }));
146    }
147
148    #[test]
149    fn parse_rejects_length_overrun() {
150        // length=5 but only 3 payload bytes available.
151        let err = DataBroadcastIdDescriptor::parse(&[TAG, 0x05, 0x00, 0x0B, 0xAA]).unwrap_err();
152        assert!(matches!(err, Error::BufferTooShort { .. }));
153    }
154
155    #[test]
156    fn serialize_round_trip() {
157        let d = DataBroadcastIdDescriptor {
158            data_broadcast_id: 0x0123,
159            id_selector: &[0xDE, 0xAD, 0xBE, 0xEF],
160        };
161        let mut buf = vec![0u8; d.serialized_len()];
162        d.serialize_into(&mut buf).unwrap();
163        let re = DataBroadcastIdDescriptor::parse(&buf).unwrap();
164        assert_eq!(d, re);
165    }
166
167    #[test]
168    fn serialize_rejects_too_small_buffer() {
169        let d = DataBroadcastIdDescriptor {
170            data_broadcast_id: 0x0001,
171            id_selector: &[0x01],
172        };
173        let mut tiny = [0u8; 2];
174        let err = d.serialize_into(&mut tiny).unwrap_err();
175        assert!(matches!(err, Error::OutputBufferTooSmall { .. }));
176    }
177
178    #[test]
179    fn serialize_rejects_over_range_body() {
180        // 254 selector bytes + 2 id bytes = 256 > 255.
181        let sel = vec![0u8; 254];
182        let d = DataBroadcastIdDescriptor {
183            data_broadcast_id: 0x0001,
184            id_selector: &sel,
185        };
186        let mut buf = vec![0u8; d.serialized_len()];
187        let err = d.serialize_into(&mut buf).unwrap_err();
188        assert!(matches!(err, Error::InvalidDescriptor { tag: TAG, .. }));
189    }
190
191    #[cfg(feature = "serde")]
192    #[test]
193    fn serde_serialize_is_stable() {
194        // Borrowed `&[u8]` cannot be deserialized from a JSON array by
195        // serde_json; matching the borrowed-bytes descriptors in this crate we
196        // exercise the serialize path and assert it is deterministic.
197        let d = DataBroadcastIdDescriptor {
198            data_broadcast_id: 0x000B,
199            id_selector: &[0x01, 0x02],
200        };
201        let json = serde_json::to_string(&d).unwrap();
202        assert_eq!(json, serde_json::to_string(&d.clone()).unwrap());
203    }
204}
dvb_si/descriptors/data_broadcast_id.rs

dvb_si/descriptors/
data_broadcast_id.rs
