dvb_si/descriptors/
time_shifted_service.rs

1//! Time Shifted Service Descriptor — ETSI EN 300 468 §6.2.45 (tag 0x4C).
2//!
3//! Table 104 (PDF p. 109). Carried in the SDT for an NVOD time-shifted
4//! service; points at the reference service whose schedule it shifts. Body is
5//! a single 16-bit `reference_service_id`.
6
7use super::descriptor_body;
8use crate::error::{Error, Result};
9use dvb_common::{Parse, Serialize};
10
11/// Descriptor tag for time_shifted_service_descriptor.
12pub const TAG: u8 = 0x4C;
13const HEADER_LEN: usize = 2;
14const BODY_LEN: usize = 2;
15
16/// Time Shifted Service Descriptor.
17#[derive(Debug, Clone, Copy, PartialEq, Eq)]
18#[cfg_attr(feature = "serde", derive(serde::Serialize))]
19pub struct TimeShiftedServiceDescriptor {
20    /// service_id of the reference (NVOD reference) service.
21    pub reference_service_id: u16,
22}
23
24impl<'a> Parse<'a> for TimeShiftedServiceDescriptor {
25    type Error = crate::error::Error;
26    fn parse(bytes: &'a [u8]) -> Result<Self> {
27        let body = descriptor_body(
28            bytes,
29            TAG,
30            "TimeShiftedServiceDescriptor",
31            "unexpected tag for time_shifted_service_descriptor",
32        )?;
33        if body.len() != BODY_LEN {
34            return Err(Error::InvalidDescriptor {
35                tag: TAG,
36                reason: "time_shifted_service_descriptor length must be 2",
37            });
38        }
39        let (hdr, _) = body
40            .split_first_chunk::<2>()
41            .ok_or(Error::InvalidDescriptor {
42                tag: TAG,
43                reason: "time_shifted_service_descriptor length must be 2",
44            })?;
45        Ok(Self {
46            reference_service_id: u16::from_be_bytes(*hdr),
47        })
48    }
49}
50
51impl Serialize for TimeShiftedServiceDescriptor {
52    type Error = crate::error::Error;
53    fn serialized_len(&self) -> usize {
54        HEADER_LEN + BODY_LEN
55    }
56
57    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
58        let len = self.serialized_len();
59        if buf.len() < len {
60            return Err(Error::OutputBufferTooSmall {
61                need: len,
62                have: buf.len(),
63            });
64        }
65        buf[0] = TAG;
66        buf[1] = BODY_LEN as u8;
67        buf[2..4].copy_from_slice(&self.reference_service_id.to_be_bytes());
68        Ok(len)
69    }
70}
71impl<'a> crate::traits::DescriptorDef<'a> for TimeShiftedServiceDescriptor {
72    const TAG: u8 = TAG;
73    const NAME: &'static str = "TIME_SHIFTED_SERVICE";
74}
75
76#[cfg(test)]
77mod tests {
78    use super::*;
79
80    #[test]
81    fn parse_reference_service_id() {
82        let bytes = [TAG, 2, 0x12, 0x34];
83        let d = TimeShiftedServiceDescriptor::parse(&bytes).unwrap();
84        assert_eq!(d.reference_service_id, 0x1234);
85    }
86
87    #[test]
88    fn parse_rejects_wrong_tag() {
89        assert!(matches!(
90            TimeShiftedServiceDescriptor::parse(&[0x4D, 2, 0x12, 0x34]).unwrap_err(),
91            Error::InvalidDescriptor { tag: 0x4D, .. }
92        ));
93    }
94
95    #[test]
96    fn parse_rejects_short_buffer() {
97        // declares length 2 but only 1 body byte present
98        let bytes = [TAG, 2, 0x12];
99        assert!(matches!(
100            TimeShiftedServiceDescriptor::parse(&bytes).unwrap_err(),
101            Error::BufferTooShort { .. }
102        ));
103    }
104
105    #[test]
106    fn parse_rejects_wrong_length() {
107        let bytes = [TAG, 3, 0x12, 0x34, 0x00];
108        assert!(matches!(
109            TimeShiftedServiceDescriptor::parse(&bytes).unwrap_err(),
110            Error::InvalidDescriptor { tag: TAG, .. }
111        ));
112    }
113
114    #[test]
115    fn serialize_round_trip() {
116        let d = TimeShiftedServiceDescriptor {
117            reference_service_id: 0xABCD,
118        };
119        let mut buf = vec![0u8; d.serialized_len()];
120        d.serialize_into(&mut buf).unwrap();
121        assert_eq!(TimeShiftedServiceDescriptor::parse(&buf).unwrap(), d);
122    }
123
124    #[test]
125    fn serialize_rejects_small_buffer() {
126        let d = TimeShiftedServiceDescriptor {
127            reference_service_id: 1,
128        };
129        let mut tiny = [0u8; 3];
130        assert!(matches!(
131            d.serialize_into(&mut tiny).unwrap_err(),
132            Error::OutputBufferTooSmall { .. }
133        ));
134    }
135
136    #[cfg(feature = "serde")]
137    #[test]
138    fn serde_round_trip() {
139        let d = TimeShiftedServiceDescriptor {
140            reference_service_id: 0x1234,
141        };
142        let json = serde_json::to_string(&d).unwrap();
143        // Serialize-only: assert the emitted JSON re-parses (serialize-stable).
144        let _v: serde_json::Value = serde_json::from_str(&json).unwrap();
145    }
146}
dvb_si/descriptors/time_shifted_service.rs

dvb_si/descriptors/
time_shifted_service.rs
