dvb_si/tables/
tdt.rs

1//! Time and Date Table — ETSI EN 300 468 §5.2.5.
2//!
3//! Short-form section on PID 0x0014 with table_id 0x70. Body is exactly
4//! 5 bytes of UTC time (16-bit MJD + 24-bit BCD HHMMSS). No CRC.
5
6use crate::error::{Error, Result};
7use crate::traits::Table;
8use dvb_common::{Parse, Serialize};
9
10/// table_id for Time and Date Table.
11pub const TABLE_ID: u8 = 0x70;
12/// Well-known PID on which TDT is carried.
13pub const PID: u16 = 0x0014;
14
15const HEADER_LEN: usize = 3;
16const UTC_TIME_LEN: usize = 5;
17
18/// Time and Date Table.
19#[derive(Debug, Clone, Copy, PartialEq, Eq)]
20#[cfg_attr(feature = "serde", derive(serde::Serialize))]
21pub struct TdtSection {
22    /// Raw 5-byte UTC time (16-bit MJD + 24-bit BCD HHMMSS) per
23    /// EN 300 468 Annex C.
24    pub utc_time_raw: [u8; 5],
25}
26
27#[cfg(feature = "chrono")]
28impl TdtSection {
29    /// Decode the UTC time to a chrono DateTime when the `chrono` feature is on.
30    ///
31    /// MJD→calendar conversion per ETSI EN 300 468 Annex C.
32    #[must_use]
33    pub fn utc_time(&self) -> Option<chrono::DateTime<chrono::Utc>> {
34        dvb_common::time::decode_mjd_bcd_utc(self.utc_time_raw)
35    }
36
37    /// Set the UTC time, encoding it into the 40-bit `utc_time` field.
38    ///
39    /// # Errors
40    /// [`ValueOutOfRange`](crate::Error::ValueOutOfRange) if the date is
41    /// outside the representable 16-bit MJD range.
42    pub fn set_utc_time(&mut self, utc_time: chrono::DateTime<chrono::Utc>) -> Result<()> {
43        self.utc_time_raw =
44            dvb_common::time::encode_mjd_bcd_utc(utc_time).ok_or(Error::ValueOutOfRange {
45                field: "TdtSection::utc_time",
46                reason: "date not representable in 16-bit MJD",
47            })?;
48        Ok(())
49    }
50}
51
52impl<'a> Parse<'a> for TdtSection {
53    type Error = crate::error::Error;
54    fn parse(bytes: &'a [u8]) -> Result<Self> {
55        let min_len = HEADER_LEN + UTC_TIME_LEN;
56        if bytes.len() < min_len {
57            return Err(Error::BufferTooShort {
58                need: min_len,
59                have: bytes.len(),
60                what: "TdtSection",
61            });
62        }
63        if bytes[0] != TABLE_ID {
64            return Err(Error::UnexpectedTableId {
65                table_id: bytes[0],
66                what: "TdtSection",
67                expected: &[TABLE_ID],
68            });
69        }
70        let section_length = ((bytes[1] & 0x0F) as u16) << 8 | bytes[2] as u16;
71        if section_length as usize != UTC_TIME_LEN {
72            return Err(Error::SectionLengthOverflow {
73                declared: section_length as usize,
74                available: UTC_TIME_LEN,
75            });
76        }
77        let utc_time_raw = [bytes[3], bytes[4], bytes[5], bytes[6], bytes[7]];
78        Ok(TdtSection { utc_time_raw })
79    }
80}
81
82impl Serialize for TdtSection {
83    type Error = crate::error::Error;
84    fn serialized_len(&self) -> usize {
85        HEADER_LEN + UTC_TIME_LEN
86    }
87    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
88        let len = self.serialized_len();
89        if buf.len() < len {
90            return Err(Error::OutputBufferTooSmall {
91                need: len,
92                have: buf.len(),
93            });
94        }
95        buf[0] = TABLE_ID;
96        buf[1] = 0x70 | ((UTC_TIME_LEN as u16 >> 8) as u8 & 0x0F);
97        buf[2] = UTC_TIME_LEN as u8;
98        buf[3..8].copy_from_slice(&self.utc_time_raw);
99        Ok(len)
100    }
101}
102
103impl<'a> Table<'a> for TdtSection {
104    const TABLE_ID: u8 = TABLE_ID;
105    const PID: u16 = PID;
106}
107
108impl<'a> crate::traits::TableDef<'a> for TdtSection {
109    const TABLE_ID_RANGES: &'static [(u8, u8)] = &[(TABLE_ID, TABLE_ID)];
110    const NAME: &'static str = "TIME_AND_DATE";
111}
112
113#[cfg(test)]
114mod tests {
115    use super::*;
116
117    #[test]
118    fn parse_extracts_utc_time_raw() {
119        let bytes = [TABLE_ID, 0x70, 0x05, 0xE4, 0x09, 0x12, 0x34, 0x56];
120        let tdt = TdtSection::parse(&bytes).unwrap();
121        assert_eq!(tdt.utc_time_raw, [0xE4, 0x09, 0x12, 0x34, 0x56]);
122    }
123
124    #[test]
125    fn parse_rejects_wrong_tag() {
126        let bytes = [0x71, 0x70, 0x05, 0, 0, 0, 0, 0];
127        assert!(matches!(
128            TdtSection::parse(&bytes).unwrap_err(),
129            Error::UnexpectedTableId { table_id: 0x71, .. }
130        ));
131    }
132
133    #[test]
134    fn parse_rejects_wrong_section_length() {
135        let bytes = [TABLE_ID, 0x70, 0x04, 0, 0, 0, 0, 0];
136        assert!(matches!(
137            TdtSection::parse(&bytes).unwrap_err(),
138            Error::SectionLengthOverflow { .. }
139        ));
140    }
141
142    #[test]
143    fn serialize_round_trip() {
144        let tdt = TdtSection {
145            utc_time_raw: [0xE4, 0x09, 0x12, 0x34, 0x56],
146        };
147        let mut buf = vec![0u8; tdt.serialized_len()];
148        tdt.serialize_into(&mut buf).unwrap();
149        let re = TdtSection::parse(&buf).unwrap();
150        assert_eq!(tdt, re);
151    }
152
153    #[test]
154    fn utc_time_decodes_to_chrono() {
155        let tdt = TdtSection {
156            utc_time_raw: [0xEA, 0x19, 0x12, 0x34, 0x56],
157        };
158        let dt = tdt.utc_time();
159        assert!(dt.is_some());
160    }
161}
dvb_si/tables/tdt.rs

dvb_si/tables/
tdt.rs
