dvb_si/descriptors/
time_shifted_event.rs

1//! Time Shifted Event Descriptor — ETSI EN 300 468 §6.2.44 (tag 0x4F).
2//!
3//! Table 103 (PDF p. 109). Carried in the EIT for an NVOD time-shifted
4//! event; points at the reference service + event it shifts. Body is a 16-bit
5//! `reference_service_id` followed by a 16-bit `reference_event_id`.
6
7use super::descriptor_body;
8use crate::error::{Error, Result};
9use dvb_common::{Parse, Serialize};
10
11/// Descriptor tag for time_shifted_event_descriptor.
12pub const TAG: u8 = 0x4F;
13const HEADER_LEN: usize = 2;
14const BODY_LEN: usize = 4;
15
16/// Time Shifted Event Descriptor.
17#[derive(Debug, Clone, Copy, PartialEq, Eq)]
18#[cfg_attr(feature = "serde", derive(serde::Serialize))]
19pub struct TimeShiftedEventDescriptor {
20    /// service_id of the reference (NVOD reference) service.
21    pub reference_service_id: u16,
22    /// event_id of the reference event within that service.
23    pub reference_event_id: u16,
24}
25
26impl<'a> Parse<'a> for TimeShiftedEventDescriptor {
27    type Error = crate::error::Error;
28    fn parse(bytes: &'a [u8]) -> Result<Self> {
29        let body = descriptor_body(
30            bytes,
31            TAG,
32            "TimeShiftedEventDescriptor",
33            "unexpected tag for time_shifted_event_descriptor",
34        )?;
35        if body.len() != BODY_LEN {
36            return Err(Error::InvalidDescriptor {
37                tag: TAG,
38                reason: "time_shifted_event_descriptor length must be 4",
39            });
40        }
41        Ok(Self {
42            reference_service_id: u16::from_be_bytes([body[0], body[1]]),
43            reference_event_id: u16::from_be_bytes([body[2], body[3]]),
44        })
45    }
46}
47
48impl Serialize for TimeShiftedEventDescriptor {
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[2..4].copy_from_slice(&self.reference_service_id.to_be_bytes());
65        buf[4..6].copy_from_slice(&self.reference_event_id.to_be_bytes());
66        Ok(len)
67    }
68}
69impl<'a> crate::traits::DescriptorDef<'a> for TimeShiftedEventDescriptor {
70    const TAG: u8 = TAG;
71    const NAME: &'static str = "TIME_SHIFTED_EVENT";
72}
73
74#[cfg(test)]
75mod tests {
76    use super::*;
77
78    #[test]
79    fn parse_reference_ids() {
80        let bytes = [TAG, 4, 0x12, 0x34, 0x56, 0x78];
81        let d = TimeShiftedEventDescriptor::parse(&bytes).unwrap();
82        assert_eq!(d.reference_service_id, 0x1234);
83        assert_eq!(d.reference_event_id, 0x5678);
84    }
85
86    #[test]
87    fn parse_rejects_wrong_tag() {
88        assert!(matches!(
89            TimeShiftedEventDescriptor::parse(&[0x50, 4, 0, 0, 0, 0]).unwrap_err(),
90            Error::InvalidDescriptor { tag: 0x50, .. }
91        ));
92    }
93
94    #[test]
95    fn parse_rejects_short_buffer() {
96        // declares length 4 but only 3 body bytes present
97        let bytes = [TAG, 4, 0x12, 0x34, 0x56];
98        assert!(matches!(
99            TimeShiftedEventDescriptor::parse(&bytes).unwrap_err(),
100            Error::BufferTooShort { .. }
101        ));
102    }
103
104    #[test]
105    fn parse_rejects_wrong_length() {
106        let bytes = [TAG, 5, 0x12, 0x34, 0x56, 0x78, 0x00];
107        assert!(matches!(
108            TimeShiftedEventDescriptor::parse(&bytes).unwrap_err(),
109            Error::InvalidDescriptor { tag: TAG, .. }
110        ));
111    }
112
113    #[test]
114    fn serialize_round_trip() {
115        let d = TimeShiftedEventDescriptor {
116            reference_service_id: 0xABCD,
117            reference_event_id: 0x0102,
118        };
119        let mut buf = vec![0u8; d.serialized_len()];
120        d.serialize_into(&mut buf).unwrap();
121        assert_eq!(TimeShiftedEventDescriptor::parse(&buf).unwrap(), d);
122    }
123
124    #[test]
125    fn serialize_rejects_small_buffer() {
126        let d = TimeShiftedEventDescriptor {
127            reference_service_id: 1,
128            reference_event_id: 2,
129        };
130        let mut tiny = [0u8; 5];
131        assert!(matches!(
132            d.serialize_into(&mut tiny).unwrap_err(),
133            Error::OutputBufferTooSmall { .. }
134        ));
135    }
136
137    #[cfg(feature = "serde")]
138    #[test]
139    fn serde_round_trip() {
140        let d = TimeShiftedEventDescriptor {
141            reference_service_id: 0x1234,
142            reference_event_id: 0x5678,
143        };
144        let json = serde_json::to_string(&d).unwrap();
145        // Serialize-only: assert the emitted JSON re-parses (serialize-stable).
146        let _v: serde_json::Value = serde_json::from_str(&json).unwrap();
147    }
148}
dvb_si/descriptors/time_shifted_event.rs

dvb_si/descriptors/
time_shifted_event.rs
