dvb_si/descriptors/
adaptation_field_data.rs

1//! Adaptation Field Data Descriptor — ETSI EN 300 468 §6.2.1 (tag 0x70, Table 13, PDF p. 54).
2//!
3//! Carried inside the PMT ES_info loop. Fixed 1-byte body: a bit-flag field
4//! `adaptation_field_data_identifier` signalling which data fields are carried
5//! in the adaptation field private_data (Table 14: announcement_switching_data,
6//! AU_information, PVR_assist_information). We carry the raw flag byte.
7
8use super::descriptor_body;
9use crate::error::{Error, Result};
10use dvb_common::{Parse, Serialize};
11
12/// Descriptor tag for adaptation_field_data_descriptor.
13pub const TAG: u8 = 0x70;
14/// Length of the header (tag byte + length byte).
15pub const HEADER_LEN: usize = 2;
16/// Fixed body length: one identifier flag byte.
17pub const BODY_LEN: usize = 1;
18
19/// Adaptation Field Data Descriptor.
20#[derive(Debug, Clone, Copy, PartialEq, Eq)]
21#[cfg_attr(feature = "serde", derive(serde::Serialize))]
22pub struct AdaptationFieldDataDescriptor {
23    /// 8-bit adaptation_field_data_identifier flag field (Table 14).
24    pub adaptation_field_data_identifier: u8,
25}
26
27impl<'a> Parse<'a> for AdaptationFieldDataDescriptor {
28    type Error = crate::error::Error;
29    fn parse(bytes: &'a [u8]) -> Result<Self> {
30        let body = descriptor_body(
31            bytes,
32            TAG,
33            "AdaptationFieldDataDescriptor",
34            "unexpected tag for adaptation_field_data_descriptor",
35        )?;
36        if body.len() != BODY_LEN {
37            return Err(Error::InvalidDescriptor {
38                tag: TAG,
39                reason: "adaptation_field_data_descriptor length must be exactly 1",
40            });
41        }
42        Ok(Self {
43            adaptation_field_data_identifier: body[0],
44        })
45    }
46}
47
48impl Serialize for AdaptationFieldDataDescriptor {
49    type Error = crate::error::Error;
50    fn serialized_len(&self) -> usize {
51        HEADER_LEN + BODY_LEN
52    }
53
54    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
55        let len = self.serialized_len();
56        if buf.len() < len {
57            return Err(Error::OutputBufferTooSmall {
58                need: len,
59                have: buf.len(),
60            });
61        }
62        buf[0] = TAG;
63        buf[1] = BODY_LEN as u8;
64        buf[HEADER_LEN] = self.adaptation_field_data_identifier;
65        Ok(len)
66    }
67}
68impl<'a> crate::traits::DescriptorDef<'a> for AdaptationFieldDataDescriptor {
69    const TAG: u8 = TAG;
70    const NAME: &'static str = "ADAPTATION_FIELD_DATA";
71}
72
73#[cfg(test)]
74mod tests {
75    use super::*;
76
77    #[test]
78    fn parse_extracts_identifier() {
79        let bytes = [TAG, 1, 0x07];
80        let d = AdaptationFieldDataDescriptor::parse(&bytes).unwrap();
81        assert_eq!(d.adaptation_field_data_identifier, 0x07);
82    }
83
84    #[test]
85    fn parse_rejects_wrong_tag() {
86        assert!(matches!(
87            AdaptationFieldDataDescriptor::parse(&[0x71, 1, 0]).unwrap_err(),
88            Error::InvalidDescriptor { tag: 0x71, .. }
89        ));
90    }
91
92    #[test]
93    fn parse_rejects_wrong_length() {
94        assert!(matches!(
95            AdaptationFieldDataDescriptor::parse(&[TAG, 0]).unwrap_err(),
96            Error::InvalidDescriptor { tag: TAG, .. }
97        ));
98    }
99
100    #[test]
101    fn parse_rejects_short_body() {
102        assert!(matches!(
103            AdaptationFieldDataDescriptor::parse(&[TAG, 1]).unwrap_err(),
104            Error::BufferTooShort { .. }
105        ));
106    }
107
108    #[test]
109    fn serialize_round_trip() {
110        let d = AdaptationFieldDataDescriptor {
111            adaptation_field_data_identifier: 0x05,
112        };
113        let mut buf = vec![0u8; d.serialized_len()];
114        d.serialize_into(&mut buf).unwrap();
115        assert_eq!(buf, [TAG, 1, 0x05]);
116        assert_eq!(AdaptationFieldDataDescriptor::parse(&buf).unwrap(), d);
117    }
118
119    #[test]
120    fn serialize_rejects_too_small_buffer() {
121        let d = AdaptationFieldDataDescriptor {
122            adaptation_field_data_identifier: 0,
123        };
124        let mut buf = vec![0u8; 2];
125        assert!(matches!(
126            d.serialize_into(&mut buf).unwrap_err(),
127            Error::OutputBufferTooSmall { .. }
128        ));
129    }
130
131    #[cfg(feature = "serde")]
132    #[test]
133    fn serde_round_trip() {
134        let d = AdaptationFieldDataDescriptor {
135            adaptation_field_data_identifier: 0x05,
136        };
137        let json = serde_json::to_string(&d).unwrap();
138        // Serialize-only: assert the emitted JSON re-parses (serialize-stable).
139        let _v: serde_json::Value = serde_json::from_str(&json).unwrap();
140    }
141}
dvb_si/descriptors/adaptation_field_data.rs

dvb_si/descriptors/
adaptation_field_data.rs
