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 dvb_common::{Parse, Serialize};
8
9/// table_id for Time and Date Table.
10pub const TABLE_ID: u8 = 0x70;
11/// Well-known PID on which TDT is carried.
12pub const PID: u16 = 0x0014;
13
14const HEADER_LEN: usize = 3;
15const UTC_TIME_LEN: usize = 5;
16
17/// Time and Date Table.
18#[derive(Debug, Clone, Copy, PartialEq, Eq)]
19#[cfg_attr(feature = "serde", derive(serde::Serialize))]
20pub struct TdtSection {
21    /// Raw 5-byte UTC time (16-bit MJD + 24-bit BCD HHMMSS) per
22    /// EN 300 468 Annex C. Private — use [`utc_time_decoded`](Self::utc_time_decoded)
23    /// for decoded access.
24    pub(crate) utc_time_raw: [u8; 5],
25}
26
27impl TdtSection {
28    /// Decode the UTC time to a plain date-time struct (no `chrono` feature
29    /// required).
30    ///
31    /// Returns `None` if the date/time fields are out of range. MJD→calendar
32    /// conversion per ETSI EN 300 468 Annex C.
33    #[must_use]
34    pub fn utc_time_decoded(&self) -> Option<dvb_common::time::MjdBcdDateTime> {
35        dvb_common::time::decode_mjd_bcd(self.utc_time_raw)
36    }
37
38    /// Set the UTC time, encoding it from a [`dvb_common::time::MjdBcdDateTime`].
39    ///
40    /// # Errors
41    /// [`ValueOutOfRange`](crate::Error::ValueOutOfRange) if the date is
42    /// outside the representable 16-bit MJD range.
43    pub fn set_utc_time_decoded(&mut self, dt: dvb_common::time::MjdBcdDateTime) -> Result<()> {
44        self.utc_time_raw = dvb_common::time::encode_mjd_bcd(dt).ok_or(Error::ValueOutOfRange {
45            field: "TdtSection::utc_time",
46            reason: "date not representable in 16-bit MJD",
47        })?;
48        Ok(())
49    }
50
51    /// Raw 5-byte UTC time field (for round-trip / serialization).
52    #[must_use]
53    pub fn utc_time_raw(&self) -> [u8; 5] {
54        self.utc_time_raw
55    }
56
57    /// Construct a `TdtSection` from raw wire fields.
58    #[must_use]
59    pub fn new(utc_time_raw: [u8; 5]) -> Self {
60        Self { utc_time_raw }
61    }
62}
63
64#[cfg(feature = "chrono")]
65impl TdtSection {
66    /// Decode the UTC time to a chrono DateTime when the `chrono` feature is on.
67    ///
68    /// MJD→calendar conversion per ETSI EN 300 468 Annex C.
69    #[must_use]
70    pub fn utc_time(&self) -> Option<chrono::DateTime<chrono::Utc>> {
71        dvb_common::time::decode_mjd_bcd_utc(self.utc_time_raw)
72    }
73
74    /// Set the UTC time, encoding it into the 40-bit `utc_time` field.
75    ///
76    /// # Errors
77    /// [`ValueOutOfRange`](crate::Error::ValueOutOfRange) if the date is
78    /// outside the representable 16-bit MJD range.
79    pub fn set_utc_time(&mut self, utc_time: chrono::DateTime<chrono::Utc>) -> Result<()> {
80        self.utc_time_raw =
81            dvb_common::time::encode_mjd_bcd_utc(utc_time).ok_or(Error::ValueOutOfRange {
82                field: "TdtSection::utc_time",
83                reason: "date not representable in 16-bit MJD",
84            })?;
85        Ok(())
86    }
87}
88
89impl<'a> Parse<'a> for TdtSection {
90    type Error = crate::error::Error;
91    fn parse(bytes: &'a [u8]) -> Result<Self> {
92        let min_len = HEADER_LEN + UTC_TIME_LEN;
93        if bytes.len() < min_len {
94            return Err(Error::BufferTooShort {
95                need: min_len,
96                have: bytes.len(),
97                what: "TdtSection",
98            });
99        }
100        if bytes[0] != TABLE_ID {
101            return Err(Error::UnexpectedTableId {
102                table_id: bytes[0],
103                what: "TdtSection",
104                expected: &[TABLE_ID],
105            });
106        }
107        let section_length = ((bytes[1] & 0x0F) as u16) << 8 | bytes[2] as u16;
108        if section_length as usize != UTC_TIME_LEN {
109            return Err(Error::SectionLengthOverflow {
110                declared: section_length as usize,
111                available: UTC_TIME_LEN,
112            });
113        }
114        let utc_time_raw = [bytes[3], bytes[4], bytes[5], bytes[6], bytes[7]];
115        Ok(TdtSection { utc_time_raw })
116    }
117}
118
119impl Serialize for TdtSection {
120    type Error = crate::error::Error;
121    fn serialized_len(&self) -> usize {
122        HEADER_LEN + UTC_TIME_LEN
123    }
124    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
125        let len = self.serialized_len();
126        if buf.len() < len {
127            return Err(Error::OutputBufferTooSmall {
128                need: len,
129                have: buf.len(),
130            });
131        }
132        buf[0] = TABLE_ID;
133        buf[1] = super::SECTION_B1_FLAGS_SHORT | ((UTC_TIME_LEN as u16 >> 8) as u8 & 0x0F);
134        buf[2] = UTC_TIME_LEN as u8;
135        buf[3..8].copy_from_slice(&self.utc_time_raw);
136        Ok(len)
137    }
138}
139impl<'a> crate::traits::TableDef<'a> for TdtSection {
140    const TABLE_ID_RANGES: &'static [(u8, u8)] = &[(TABLE_ID, TABLE_ID)];
141    const NAME: &'static str = "TIME_AND_DATE";
142}
143
144#[cfg(test)]
145mod tests {
146    use super::*;
147
148    #[test]
149    fn parse_extracts_utc_time_raw() {
150        let bytes = [TABLE_ID, 0x70, 0x05, 0xE4, 0x09, 0x12, 0x34, 0x56];
151        let tdt = TdtSection::parse(&bytes).unwrap();
152        assert_eq!(tdt.utc_time_raw(), [0xE4, 0x09, 0x12, 0x34, 0x56]);
153    }
154
155    #[test]
156    fn parse_rejects_wrong_tag() {
157        let bytes = [0x71, 0x70, 0x05, 0, 0, 0, 0, 0];
158        assert!(matches!(
159            TdtSection::parse(&bytes).unwrap_err(),
160            Error::UnexpectedTableId { table_id: 0x71, .. }
161        ));
162    }
163
164    #[test]
165    fn parse_rejects_wrong_section_length() {
166        let bytes = [TABLE_ID, 0x70, 0x04, 0, 0, 0, 0, 0];
167        assert!(matches!(
168            TdtSection::parse(&bytes).unwrap_err(),
169            Error::SectionLengthOverflow { .. }
170        ));
171    }
172
173    #[test]
174    fn serialize_round_trip() {
175        let tdt = TdtSection {
176            utc_time_raw: [0xE4, 0x09, 0x12, 0x34, 0x56],
177        };
178        let mut buf = vec![0u8; tdt.serialized_len()];
179        tdt.serialize_into(&mut buf).unwrap();
180        let re = TdtSection::parse(&buf).unwrap();
181        assert_eq!(tdt, re);
182    }
183
184    #[cfg(feature = "chrono")]
185    #[test]
186    fn utc_time_decodes_to_chrono() {
187        let tdt = TdtSection {
188            utc_time_raw: [0xEA, 0x19, 0x12, 0x34, 0x56],
189        };
190        let dt = tdt.utc_time();
191        assert!(dt.is_some());
192    }
193
194    #[test]
195    fn utc_time_decodes_without_chrono() {
196        let tdt = TdtSection {
197            utc_time_raw: [0xE4, 0x09, 0x12, 0x34, 0x56],
198        };
199        let dt = tdt.utc_time_decoded().unwrap();
200        assert_eq!(dt.year, 2018);
201        assert_eq!(dt.month, 9);
202        assert_eq!(dt.day, 16);
203        assert_eq!(dt.hour, 12);
204        assert_eq!(dt.minute, 34);
205        assert_eq!(dt.second, 56);
206    }
207}
dvb_si/tables/tdt.rs

dvb_si/tables/
tdt.rs
