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

dvb_si/descriptors/
ca_identifier.rs
