dvb_si/descriptors/ait/
external_application_authorisation.rs

1//! External Application Authorisation Descriptor — ETSI TS 102 809 §5.3.5.7, Table 26
2//! (AIT tag 0x05).
3//!
4//! Carried in the AIT common descriptor loop. Authorises external applications
5//! by their application identifier + priority.
6
7use crate::descriptors::descriptor_body;
8use crate::error::{Error, Result};
9use crate::tables::ait::ApplicationIdentifier;
10use alloc::vec::Vec;
11use dvb_common::{Parse, Serialize};
12
13/// Descriptor tag for external_application_authorisation_descriptor (AIT namespace).
14pub const TAG: u8 = 0x05;
15const HEADER_LEN: usize = 2;
16const ENTRY_LEN: usize = 7;
17
18/// One external application authorisation entry.
19#[derive(Debug, Clone, PartialEq, Eq)]
20#[cfg_attr(feature = "serde", derive(serde::Serialize))]
21pub struct ExternalAppEntry {
22    /// Application identifier (organisation_id + application_id).
23    pub identifier: ApplicationIdentifier,
24    /// Application priority.
25    pub application_priority: u8,
26}
27
28/// External Application Authorisation Descriptor (AIT tag 0x05).
29#[derive(Debug, Clone, PartialEq, Eq)]
30#[cfg_attr(feature = "serde", derive(serde::Serialize))]
31pub struct ExternalApplicationAuthorisationDescriptor {
32    /// Authorised external applications in wire order.
33    pub entries: Vec<ExternalAppEntry>,
34}
35
36impl<'a> Parse<'a> for ExternalApplicationAuthorisationDescriptor {
37    type Error = crate::error::Error;
38    fn parse(bytes: &'a [u8]) -> Result<Self> {
39        let body = descriptor_body(
40            bytes,
41            TAG,
42            "ExternalApplicationAuthorisationDescriptor",
43            "unexpected tag for external_application_authorisation_descriptor",
44        )?;
45        if body.len() % ENTRY_LEN != 0 {
46            return Err(Error::InvalidDescriptor {
47                tag: TAG,
48                reason:
49                    "external_application_authorisation_descriptor length must be a multiple of 7",
50            });
51        }
52        let mut entries = Vec::with_capacity(body.len() / ENTRY_LEN);
53        for chunk in body.chunks_exact(ENTRY_LEN) {
54            let (org_bytes, rest) = chunk.split_first_chunk::<4>().unwrap();
55            let organisation_id = u32::from_be_bytes(*org_bytes);
56            let (app_bytes, priority_slice) = rest.split_first_chunk::<2>().unwrap();
57            let application_id = u16::from_be_bytes(*app_bytes);
58            let application_priority = priority_slice[0];
59            entries.push(ExternalAppEntry {
60                identifier: ApplicationIdentifier {
61                    organisation_id,
62                    application_id,
63                },
64                application_priority,
65            });
66        }
67        Ok(Self { entries })
68    }
69}
70
71impl Serialize for ExternalApplicationAuthorisationDescriptor {
72    type Error = crate::error::Error;
73    fn serialized_len(&self) -> usize {
74        HEADER_LEN + self.entries.len() * ENTRY_LEN
75    }
76
77    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
78        if self.entries.len() * ENTRY_LEN > u8::MAX as usize {
79            return Err(Error::InvalidDescriptor {
80                tag: TAG,
81                reason: "external_application_authorisation_descriptor body exceeds 255 bytes",
82            });
83        }
84        let len = self.serialized_len();
85        if buf.len() < len {
86            return Err(Error::OutputBufferTooSmall {
87                need: len,
88                have: buf.len(),
89            });
90        }
91        buf[0] = TAG;
92        buf[1] = (self.entries.len() * ENTRY_LEN) as u8;
93        let mut pos = HEADER_LEN;
94        for e in &self.entries {
95            buf[pos..pos + 4].copy_from_slice(&e.identifier.organisation_id.to_be_bytes());
96            buf[pos + 4..pos + 6].copy_from_slice(&e.identifier.application_id.to_be_bytes());
97            buf[pos + 6] = e.application_priority;
98            pos += ENTRY_LEN;
99        }
100        Ok(len)
101    }
102}
103
104impl<'a> crate::traits::DescriptorDef<'a> for ExternalApplicationAuthorisationDescriptor {
105    const TAG: u8 = TAG;
106    const NAME: &'static str = "EXTERNAL_APPLICATION_AUTHORISATION";
107}
108
109#[cfg(test)]
110mod tests {
111    use super::*;
112
113    #[test]
114    fn parse_single_entry() {
115        let bytes = [
116            TAG, 7, 0x00, 0x00, 0x00, 0x01, // organisation_id=1
117            0x00, 0x0A, // application_id=10
118            0x05, // priority=5
119        ];
120        let d = ExternalApplicationAuthorisationDescriptor::parse(&bytes).unwrap();
121        assert_eq!(d.entries.len(), 1);
122        assert_eq!(d.entries[0].identifier.organisation_id, 1);
123        assert_eq!(d.entries[0].identifier.application_id, 10);
124        assert_eq!(d.entries[0].application_priority, 5);
125    }
126
127    #[test]
128    fn parse_multiple_entries() {
129        let bytes = [
130            TAG, 14, 0x00, 0x00, 0x00, 0x01, 0x00, 0x0A, 0x05, 0x00, 0x00, 0x00, 0x02, 0x00, 0x14,
131            0x0A,
132        ];
133        let d = ExternalApplicationAuthorisationDescriptor::parse(&bytes).unwrap();
134        assert_eq!(d.entries.len(), 2);
135        assert_eq!(d.entries[1].identifier.organisation_id, 2);
136    }
137
138    #[test]
139    fn parse_rejects_bad_length() {
140        let bytes = [TAG, 8, 0, 0, 0, 1, 0, 5, 0, 0]; // body not a multiple of 7
141        assert!(ExternalApplicationAuthorisationDescriptor::parse(&bytes).is_err());
142    }
143
144    #[test]
145    fn serialize_round_trip() {
146        let d = ExternalApplicationAuthorisationDescriptor {
147            entries: alloc::vec![ExternalAppEntry {
148                identifier: ApplicationIdentifier {
149                    organisation_id: 0xDEAD,
150                    application_id: 0xBEEF,
151                },
152                application_priority: 42,
153            }],
154        };
155        let mut buf = vec![0u8; d.serialized_len()];
156        d.serialize_into(&mut buf).unwrap();
157        let re = ExternalApplicationAuthorisationDescriptor::parse(&buf).unwrap();
158        assert_eq!(d, re);
159    }
160
161    #[test]
162    fn serialize_byte_identical() {
163        let bytes = [TAG, 7, 0x00, 0x00, 0x10, 0x00, 0x00, 0x01, 0xFF];
164        let d = ExternalApplicationAuthorisationDescriptor::parse(&bytes).unwrap();
165        let mut buf = vec![0u8; d.serialized_len()];
166        d.serialize_into(&mut buf).unwrap();
167        assert_eq!(buf.as_slice(), &bytes[..]);
168    }
169}
dvb_si/descriptors/ait/external_application_authorisation.rs

dvb_si/descriptors/ait/
external_application_authorisation.rs
