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 crate::error::{Error, Result};
8use crate::traits::Descriptor;
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        if bytes.len() < HEADER_LEN {
30            return Err(Error::BufferTooShort {
31                need: HEADER_LEN,
32                have: bytes.len(),
33                what: "TimeShiftedEventDescriptor header",
34            });
35        }
36        if bytes[0] != TAG {
37            return Err(Error::InvalidDescriptor {
38                tag: bytes[0],
39                reason: "unexpected tag for time_shifted_event_descriptor",
40            });
41        }
42        let length = bytes[1] as usize;
43        if length != BODY_LEN {
44            return Err(Error::InvalidDescriptor {
45                tag: TAG,
46                reason: "time_shifted_event_descriptor length must be 4",
47            });
48        }
49        let end = HEADER_LEN + BODY_LEN;
50        if bytes.len() < end {
51            return Err(Error::BufferTooShort {
52                need: end,
53                have: bytes.len(),
54                what: "TimeShiftedEventDescriptor body",
55            });
56        }
57        Ok(Self {
58            reference_service_id: u16::from_be_bytes([bytes[2], bytes[3]]),
59            reference_event_id: u16::from_be_bytes([bytes[4], bytes[5]]),
60        })
61    }
62}
63
64impl Serialize for TimeShiftedEventDescriptor {
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[2..4].copy_from_slice(&self.reference_service_id.to_be_bytes());
81        buf[4..6].copy_from_slice(&self.reference_event_id.to_be_bytes());
82        Ok(len)
83    }
84}
85
86impl<'a> Descriptor<'a> for TimeShiftedEventDescriptor {
87    const TAG: u8 = TAG;
88    fn descriptor_length(&self) -> u8 {
89        BODY_LEN as u8
90    }
91}
92
93impl<'a> crate::traits::DescriptorDef<'a> for TimeShiftedEventDescriptor {
94    const TAG: u8 = TAG;
95    const NAME: &'static str = "TIME_SHIFTED_EVENT";
96}
97
98#[cfg(test)]
99mod tests {
100    use super::*;
101
102    #[test]
103    fn parse_reference_ids() {
104        let bytes = [TAG, 4, 0x12, 0x34, 0x56, 0x78];
105        let d = TimeShiftedEventDescriptor::parse(&bytes).unwrap();
106        assert_eq!(d.reference_service_id, 0x1234);
107        assert_eq!(d.reference_event_id, 0x5678);
108    }
109
110    #[test]
111    fn parse_rejects_wrong_tag() {
112        assert!(matches!(
113            TimeShiftedEventDescriptor::parse(&[0x50, 4, 0, 0, 0, 0]).unwrap_err(),
114            Error::InvalidDescriptor { tag: 0x50, .. }
115        ));
116    }
117
118    #[test]
119    fn parse_rejects_short_buffer() {
120        // declares length 4 but only 3 body bytes present
121        let bytes = [TAG, 4, 0x12, 0x34, 0x56];
122        assert!(matches!(
123            TimeShiftedEventDescriptor::parse(&bytes).unwrap_err(),
124            Error::BufferTooShort { .. }
125        ));
126    }
127
128    #[test]
129    fn parse_rejects_wrong_length() {
130        let bytes = [TAG, 5, 0x12, 0x34, 0x56, 0x78, 0x00];
131        assert!(matches!(
132            TimeShiftedEventDescriptor::parse(&bytes).unwrap_err(),
133            Error::InvalidDescriptor { tag: TAG, .. }
134        ));
135    }
136
137    #[test]
138    fn serialize_round_trip() {
139        let d = TimeShiftedEventDescriptor {
140            reference_service_id: 0xABCD,
141            reference_event_id: 0x0102,
142        };
143        let mut buf = vec![0u8; d.serialized_len()];
144        d.serialize_into(&mut buf).unwrap();
145        assert_eq!(TimeShiftedEventDescriptor::parse(&buf).unwrap(), d);
146    }
147
148    #[test]
149    fn serialize_rejects_small_buffer() {
150        let d = TimeShiftedEventDescriptor {
151            reference_service_id: 1,
152            reference_event_id: 2,
153        };
154        let mut tiny = [0u8; 5];
155        assert!(matches!(
156            d.serialize_into(&mut tiny).unwrap_err(),
157            Error::OutputBufferTooSmall { .. }
158        ));
159    }
160
161    #[cfg(feature = "serde")]
162    #[test]
163    fn serde_round_trip() {
164        let d = TimeShiftedEventDescriptor {
165            reference_service_id: 0x1234,
166            reference_event_id: 0x5678,
167        };
168        let json = serde_json::to_string(&d).unwrap();
169        // Serialize-only: assert the emitted JSON re-parses (serialize-stable).
170        let _v: serde_json::Value = serde_json::from_str(&json).unwrap();
171    }
172}
dvb_si/descriptors/time_shifted_event.rs

dvb_si/descriptors/
time_shifted_event.rs
