dvb_si/descriptors/
ca_identifier.rs

1//! CA Identifier Descriptor — ETSI EN 300 468 §6.2.6 (tag 0x53).
2//!
3//! Table 22 (PDF p. 57). Carried in SDT/BAT/EIT descriptor loops; lists the
4//! `CA_system_id`s whose conditional-access systems are available for the
5//! associated service/bouquet/event. Body is simply `N` × 16-bit CAIDs.
6
7pub use super::ca::ca_system_name;
8use super::descriptor_body;
9use crate::error::{Error, Result};
10use alloc::vec::Vec;
11use dvb_common::{Parse, Serialize};
12
13/// Descriptor tag for CA_identifier_descriptor.
14pub const TAG: u8 = 0x53;
15const HEADER_LEN: usize = 2;
16const ENTRY_LEN: usize = 2;
17/// Maximum body length expressible in the 8-bit `descriptor_length` field.
18const MAX_BODY_LEN: usize = u8::MAX as usize;
19
20/// CA Identifier Descriptor.
21#[derive(Debug, Clone, PartialEq, Eq)]
22#[cfg_attr(feature = "serde", derive(serde::Serialize))]
23pub struct CaIdentifierDescriptor {
24    /// CA_system_id values in wire order.
25    pub ca_system_ids: Vec<u16>,
26}
27
28impl<'a> Parse<'a> for CaIdentifierDescriptor {
29    type Error = crate::error::Error;
30    fn parse(bytes: &'a [u8]) -> Result<Self> {
31        let body = descriptor_body(
32            bytes,
33            TAG,
34            "CaIdentifierDescriptor",
35            "unexpected tag for CA_identifier_descriptor",
36        )?;
37        if body.len() % ENTRY_LEN != 0 {
38            return Err(Error::InvalidDescriptor {
39                tag: TAG,
40                reason: "descriptor_length must be a multiple of 2",
41            });
42        }
43        let mut ca_system_ids = Vec::with_capacity(body.len() / ENTRY_LEN);
44        for chunk in body.chunks_exact(ENTRY_LEN) {
45            ca_system_ids.push(u16::from_be_bytes([chunk[0], chunk[1]]));
46        }
47        Ok(Self { ca_system_ids })
48    }
49}
50
51impl Serialize for CaIdentifierDescriptor {
52    type Error = crate::error::Error;
53    fn serialized_len(&self) -> usize {
54        HEADER_LEN + ENTRY_LEN * self.ca_system_ids.len()
55    }
56
57    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
58        let len = self.serialized_len();
59        if buf.len() < len {
60            return Err(Error::OutputBufferTooSmall {
61                need: len,
62                have: buf.len(),
63            });
64        }
65        let body_len = ENTRY_LEN * self.ca_system_ids.len();
66        // 8-bit descriptor_length field: error rather than silently truncate.
67        if body_len > MAX_BODY_LEN {
68            return Err(Error::InvalidDescriptor {
69                tag: TAG,
70                reason: "CA_identifier_descriptor body exceeds 255 bytes",
71            });
72        }
73        buf[0] = TAG;
74        buf[1] = body_len as u8;
75        let mut pos = HEADER_LEN;
76        for caid in &self.ca_system_ids {
77            buf[pos..pos + ENTRY_LEN].copy_from_slice(&caid.to_be_bytes());
78            pos += ENTRY_LEN;
79        }
80        Ok(len)
81    }
82}
83impl<'a> crate::traits::DescriptorDef<'a> for CaIdentifierDescriptor {
84    const TAG: u8 = TAG;
85    const NAME: &'static str = "CA_IDENTIFIER";
86}
87
88#[cfg(test)]
89mod tests {
90    use super::*;
91
92    #[test]
93    fn parse_single_caid() {
94        let bytes = [TAG, 2, 0x06, 0x50];
95        let d = CaIdentifierDescriptor::parse(&bytes).unwrap();
96        assert_eq!(d.ca_system_ids, vec![0x0650]);
97    }
98
99    #[test]
100    fn parse_multiple_caids_preserves_order() {
101        let bytes = [TAG, 6, 0x05, 0x00, 0x06, 0x50, 0x0B, 0x00];
102        let d = CaIdentifierDescriptor::parse(&bytes).unwrap();
103        assert_eq!(d.ca_system_ids, vec![0x0500, 0x0650, 0x0B00]);
104    }
105
106    #[test]
107    fn parse_rejects_wrong_tag() {
108        assert!(matches!(
109            CaIdentifierDescriptor::parse(&[0x54, 2, 0x06, 0x50]).unwrap_err(),
110            Error::InvalidDescriptor { tag: 0x54, .. }
111        ));
112    }
113
114    #[test]
115    fn parse_rejects_short_buffer() {
116        // declares 4 body bytes, only 2 present
117        let bytes = [TAG, 4, 0x06, 0x50];
118        assert!(matches!(
119            CaIdentifierDescriptor::parse(&bytes).unwrap_err(),
120            Error::BufferTooShort { .. }
121        ));
122    }
123
124    #[test]
125    fn parse_rejects_odd_length() {
126        let bytes = [TAG, 3, 0x06, 0x50, 0x00];
127        assert!(matches!(
128            CaIdentifierDescriptor::parse(&bytes).unwrap_err(),
129            Error::InvalidDescriptor { tag: TAG, .. }
130        ));
131    }
132
133    #[test]
134    fn empty_descriptor_valid() {
135        let d = CaIdentifierDescriptor::parse(&[TAG, 0]).unwrap();
136        assert!(d.ca_system_ids.is_empty());
137    }
138
139    #[test]
140    fn serialize_round_trip() {
141        let d = CaIdentifierDescriptor {
142            ca_system_ids: vec![0x0100, 0x1800, 0x2600],
143        };
144        let mut buf = vec![0u8; d.serialized_len()];
145        d.serialize_into(&mut buf).unwrap();
146        assert_eq!(CaIdentifierDescriptor::parse(&buf).unwrap(), d);
147    }
148
149    #[test]
150    fn serialize_rejects_over_range_body() {
151        // 128 CAIDs = 256 body bytes, one past the u8 length field.
152        let d = CaIdentifierDescriptor {
153            ca_system_ids: vec![0x0500; 128],
154        };
155        let mut buf = vec![0u8; d.serialized_len()];
156        assert!(matches!(
157            d.serialize_into(&mut buf).unwrap_err(),
158            Error::InvalidDescriptor { tag: TAG, .. }
159        ));
160    }
161
162    #[cfg(feature = "serde")]
163    #[test]
164    fn serde_round_trip() {
165        let d = CaIdentifierDescriptor {
166            ca_system_ids: vec![0x0500, 0x0650],
167        };
168        let json = serde_json::to_string(&d).unwrap();
169        // Serialize-only: assert the emitted JSON re-parses (serialize-stable).
170        let _v: serde_json::Value = serde_json::from_str(&json).unwrap();
171    }
172}
dvb_si/descriptors/ca_identifier.rs

dvb_si/descriptors/
ca_identifier.rs
