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 crate::error::{Error, Result};
9use crate::traits::Descriptor;
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, serde::Deserialize))]
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        if bytes.len() < HEADER_LEN {
31            return Err(Error::BufferTooShort {
32                need: HEADER_LEN,
33                have: bytes.len(),
34                what: "AdaptationFieldDataDescriptor header",
35            });
36        }
37        if bytes[0] != TAG {
38            return Err(Error::InvalidDescriptor {
39                tag: bytes[0],
40                reason: "unexpected tag for adaptation_field_data_descriptor",
41            });
42        }
43        let length = bytes[1] as usize;
44        if length != BODY_LEN {
45            return Err(Error::InvalidDescriptor {
46                tag: TAG,
47                reason: "adaptation_field_data_descriptor length must be exactly 1",
48            });
49        }
50        let end = HEADER_LEN + length;
51        if bytes.len() < end {
52            return Err(Error::BufferTooShort {
53                need: end,
54                have: bytes.len(),
55                what: "AdaptationFieldDataDescriptor body",
56            });
57        }
58        Ok(Self {
59            adaptation_field_data_identifier: bytes[HEADER_LEN],
60        })
61    }
62}
63
64impl Serialize for AdaptationFieldDataDescriptor {
65    type Error = crate::error::Error;
66    fn serialized_len(&self) -> usize {
67        HEADER_LEN + BODY_LEN
68    }
69
70    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
71        let len = self.serialized_len();
72        if buf.len() < len {
73            return Err(Error::OutputBufferTooSmall {
74                need: len,
75                have: buf.len(),
76            });
77        }
78        buf[0] = TAG;
79        buf[1] = BODY_LEN as u8;
80        buf[HEADER_LEN] = self.adaptation_field_data_identifier;
81        Ok(len)
82    }
83}
84
85impl<'a> Descriptor<'a> for AdaptationFieldDataDescriptor {
86    const TAG: u8 = TAG;
87    fn descriptor_length(&self) -> u8 {
88        BODY_LEN as u8
89    }
90}
91
92#[cfg(test)]
93mod tests {
94    use super::*;
95
96    #[test]
97    fn parse_extracts_identifier() {
98        let bytes = [TAG, 1, 0x07];
99        let d = AdaptationFieldDataDescriptor::parse(&bytes).unwrap();
100        assert_eq!(d.adaptation_field_data_identifier, 0x07);
101    }
102
103    #[test]
104    fn parse_rejects_wrong_tag() {
105        assert!(matches!(
106            AdaptationFieldDataDescriptor::parse(&[0x71, 1, 0]).unwrap_err(),
107            Error::InvalidDescriptor { tag: 0x71, .. }
108        ));
109    }
110
111    #[test]
112    fn parse_rejects_wrong_length() {
113        assert!(matches!(
114            AdaptationFieldDataDescriptor::parse(&[TAG, 0]).unwrap_err(),
115            Error::InvalidDescriptor { tag: TAG, .. }
116        ));
117    }
118
119    #[test]
120    fn parse_rejects_short_body() {
121        assert!(matches!(
122            AdaptationFieldDataDescriptor::parse(&[TAG, 1]).unwrap_err(),
123            Error::BufferTooShort { .. }
124        ));
125    }
126
127    #[test]
128    fn serialize_round_trip() {
129        let d = AdaptationFieldDataDescriptor {
130            adaptation_field_data_identifier: 0x05,
131        };
132        let mut buf = vec![0u8; d.serialized_len()];
133        d.serialize_into(&mut buf).unwrap();
134        assert_eq!(buf, [TAG, 1, 0x05]);
135        assert_eq!(AdaptationFieldDataDescriptor::parse(&buf).unwrap(), d);
136    }
137
138    #[test]
139    fn serialize_rejects_too_small_buffer() {
140        let d = AdaptationFieldDataDescriptor {
141            adaptation_field_data_identifier: 0,
142        };
143        let mut buf = vec![0u8; 2];
144        assert!(matches!(
145            d.serialize_into(&mut buf).unwrap_err(),
146            Error::OutputBufferTooSmall { .. }
147        ));
148    }
149
150    #[cfg(feature = "serde")]
151    #[test]
152    fn serde_round_trip() {
153        let d = AdaptationFieldDataDescriptor {
154            adaptation_field_data_identifier: 0x05,
155        };
156        let json = serde_json::to_string(&d).unwrap();
157        let back: AdaptationFieldDataDescriptor = serde_json::from_str(&json).unwrap();
158        assert_eq!(back, d);
159    }
160}
dvb_si/descriptors/adaptation_field_data.rs

dvb_si/descriptors/
adaptation_field_data.rs
