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

dvb_si/descriptors/
ca_identifier.rs
