dvb_si/descriptors/ait/
dvb_j_application.rs

1//! DVB-J Application Descriptor — ETSI TS 102 727 §10.9.1, Table 84
2//! (AIT tag 0x03).
3//!
4//! Carried in the AIT per-application descriptor loop. The body is a run of
5//! length-prefixed parameter strings consumed until `descriptor_length` is exhausted.
6
7use crate::descriptors::descriptor_body;
8use crate::error::{Error, Result};
9use alloc::vec::Vec;
10use dvb_common::{Parse, Serialize};
11
12/// Descriptor tag for dvb_j_application_descriptor (AIT namespace).
13pub const TAG: u8 = 0x03;
14const HEADER_LEN: usize = 2;
15
16/// DVB-J Application Descriptor (AIT tag 0x03).
17#[derive(Debug, Clone, PartialEq, Eq)]
18#[cfg_attr(feature = "serde", derive(serde::Serialize))]
19pub struct DvbJApplicationDescriptor<'a> {
20    /// Length-prefixed parameter strings in wire order.
21    #[cfg_attr(feature = "serde", serde(borrow))]
22    pub parameters: Vec<&'a [u8]>,
23}
24
25impl<'a> Parse<'a> for DvbJApplicationDescriptor<'a> {
26    type Error = crate::error::Error;
27    fn parse(bytes: &'a [u8]) -> Result<Self> {
28        let body = descriptor_body(
29            bytes,
30            TAG,
31            "DvbJApplicationDescriptor",
32            "unexpected tag for dvb_j_application_descriptor",
33        )?;
34        let mut parameters = Vec::new();
35        let mut pos = 0;
36        while pos < body.len() {
37            let param_len = body[pos] as usize;
38            pos += 1;
39            if pos + param_len > body.len() {
40                return Err(Error::InvalidDescriptor {
41                    tag: TAG,
42                    reason: "dvb_j_application_descriptor parameter overruns body",
43                });
44            }
45            parameters.push(&body[pos..pos + param_len]);
46            pos += param_len;
47        }
48        Ok(Self { parameters })
49    }
50}
51
52impl Serialize for DvbJApplicationDescriptor<'_> {
53    type Error = crate::error::Error;
54    fn serialized_len(&self) -> usize {
55        HEADER_LEN + self.parameters.iter().map(|p| 1 + p.len()).sum::<usize>()
56    }
57
58    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
59        // Check each parameter fits in one length byte.
60        for p in &self.parameters {
61            if p.len() > u8::MAX as usize {
62                return Err(Error::InvalidDescriptor {
63                    tag: TAG,
64                    reason: "dvb_j_application_descriptor parameter exceeds 255 bytes",
65                });
66            }
67        }
68        let body_len = self.serialized_len() - HEADER_LEN;
69        if body_len > u8::MAX as usize {
70            return Err(Error::InvalidDescriptor {
71                tag: TAG,
72                reason: "dvb_j_application_descriptor body exceeds 255 bytes",
73            });
74        }
75        let len = self.serialized_len();
76        if buf.len() < len {
77            return Err(Error::OutputBufferTooSmall {
78                need: len,
79                have: buf.len(),
80            });
81        }
82        buf[0] = TAG;
83        buf[1] = body_len as u8;
84        let mut pos = HEADER_LEN;
85        for p in &self.parameters {
86            buf[pos] = p.len() as u8;
87            pos += 1;
88            buf[pos..pos + p.len()].copy_from_slice(p);
89            pos += p.len();
90        }
91        Ok(len)
92    }
93}
94
95impl<'a> crate::traits::DescriptorDef<'a> for DvbJApplicationDescriptor<'a> {
96    const TAG: u8 = TAG;
97    const NAME: &'static str = "DVB_J_APPLICATION";
98}
99
100#[cfg(test)]
101mod tests {
102    use super::*;
103
104    #[test]
105    fn parse_empty() {
106        let bytes = [TAG, 0];
107        let d = DvbJApplicationDescriptor::parse(&bytes).unwrap();
108        assert!(d.parameters.is_empty());
109    }
110
111    #[test]
112    fn parse_two_params() {
113        let bytes = [
114            TAG, 6, // descriptor_length = 6
115            2, b'a', b'b', // param_len=2, "ab"
116            2, b'c', b'd', // param_len=2, "cd"
117        ];
118        let d = DvbJApplicationDescriptor::parse(&bytes).unwrap();
119        assert_eq!(d.parameters.len(), 2);
120        assert_eq!(d.parameters[0], b"ab");
121        assert_eq!(d.parameters[1], b"cd");
122    }
123
124    #[test]
125    fn parse_truncated_param_value() {
126        let bytes = [
127            TAG, 3, // descriptor_length = 3
128            4, b'a',
129            b'b', // param_len=4, but only 2 bytes remain after length
130                  // (body is only 3 bytes: [4, a, b])
131        ];
132        assert!(DvbJApplicationDescriptor::parse(&bytes).is_err());
133    }
134
135    #[test]
136    fn serialize_round_trip() {
137        let d = DvbJApplicationDescriptor {
138            parameters: vec![&b"hello"[..], &b"world"[..]],
139        };
140        let mut buf = vec![0u8; d.serialized_len()];
141        d.serialize_into(&mut buf).unwrap();
142        let re = DvbJApplicationDescriptor::parse(&buf).unwrap();
143        assert_eq!(d, re);
144    }
145
146    #[test]
147    fn serialize_byte_identical() {
148        let bytes = [
149            TAG, 4, // descriptor_length = 4
150            1, b'a', // param1
151            1, b'b', // param2
152        ];
153        let d = DvbJApplicationDescriptor::parse(&bytes).unwrap();
154        let mut buf = vec![0u8; d.serialized_len()];
155        d.serialize_into(&mut buf).unwrap();
156        assert_eq!(buf.as_slice(), &bytes[..]);
157    }
158}
dvb_si/descriptors/ait/dvb_j_application.rs

dvb_si/descriptors/ait/
dvb_j_application.rs
