dvb_si/descriptors/
pdc.rs

1//! PDC Descriptor — ETSI EN 300 468 §6.2.30 (tag 0x69, Table 84, PDF p. 97).
2//!
3//! Programme Delivery Control. Carried inside EIT. Fixed 3-byte body:
4//! `reserved_future_use` (4 bits) + `programme_identification_label` (20 bits).
5//! The PIL encodes a "day month hour minute" stamp used by VCRs to trigger
6//! recording independent of schedule slippage.
7
8use crate::error::{Error, Result};
9use crate::traits::Descriptor;
10use dvb_common::{Parse, Serialize};
11
12/// Descriptor tag for PDC_descriptor.
13pub const TAG: u8 = 0x69;
14/// Length of the header (tag byte + length byte).
15pub const HEADER_LEN: usize = 2;
16/// Fixed body length: 4 reserved bits + 20-bit PIL = 24 bits = 3 bytes.
17pub const BODY_LEN: usize = 3;
18/// The programme_identification_label occupies the low 20 bits.
19pub const PIL_MASK: u32 = 0x000F_FFFF;
20/// Reserved bits occupy the top 4 of the 24-bit body. Ignored on parse,
21/// emitted as 1s on serialize (EN 300 468 §5.1).
22pub const RESERVED_BITS: u32 = 0x00F0_0000;
23
24/// PDC Descriptor.
25#[derive(Debug, Clone, Copy, PartialEq, Eq)]
26#[cfg_attr(feature = "serde", derive(serde::Serialize))]
27pub struct PdcDescriptor {
28    /// 20-bit programme_identification_label (day/month/hour/minute packed).
29    pub programme_identification_label: u32,
30}
31
32impl PdcDescriptor {
33    /// Day-of-month component of the `programme_identification_label`
34    /// (5 bits `[19:15]`, EN 300 468 §6.2.29).
35    #[must_use]
36    pub fn pil_day(&self) -> u8 {
37        ((self.programme_identification_label >> 15) & 0x1F) as u8
38    }
39
40    /// Month component (4 bits `[14:11]`).
41    #[must_use]
42    pub fn pil_month(&self) -> u8 {
43        ((self.programme_identification_label >> 11) & 0x0F) as u8
44    }
45
46    /// Hour component (5 bits `[10:6]`).
47    #[must_use]
48    pub fn pil_hour(&self) -> u8 {
49        ((self.programme_identification_label >> 6) & 0x1F) as u8
50    }
51
52    /// Minute component (6 bits `[5:0]`).
53    #[must_use]
54    pub fn pil_minute(&self) -> u8 {
55        (self.programme_identification_label & 0x3F) as u8
56    }
57
58    /// Set the `programme_identification_label` from its day/month/hour/minute
59    /// components.
60    ///
61    /// # Errors
62    /// [`ValueOutOfRange`](crate::Error::ValueOutOfRange) if any
63    /// component exceeds its bit field (`day` ≤ 31, `month` ≤ 15, `hour` ≤ 31,
64    /// `minute` ≤ 63).
65    pub fn set_pil(&mut self, day: u8, month: u8, hour: u8, minute: u8) -> crate::Result<()> {
66        if day > 0x1F || month > 0x0F || hour > 0x1F || minute > 0x3F {
67            return Err(crate::Error::ValueOutOfRange {
68                field: "PdcDescriptor::programme_identification_label",
69                reason: "a day/month/hour/minute component exceeds its bit field",
70            });
71        }
72        self.programme_identification_label = (u32::from(day) << 15)
73            | (u32::from(month) << 11)
74            | (u32::from(hour) << 6)
75            | u32::from(minute);
76        Ok(())
77    }
78}
79
80impl<'a> Parse<'a> for PdcDescriptor {
81    type Error = crate::error::Error;
82    fn parse(bytes: &'a [u8]) -> Result<Self> {
83        if bytes.len() < HEADER_LEN {
84            return Err(Error::BufferTooShort {
85                need: HEADER_LEN,
86                have: bytes.len(),
87                what: "PdcDescriptor header",
88            });
89        }
90        if bytes[0] != TAG {
91            return Err(Error::InvalidDescriptor {
92                tag: bytes[0],
93                reason: "unexpected tag for PDC_descriptor",
94            });
95        }
96        let length = bytes[1] as usize;
97        if length != BODY_LEN {
98            return Err(Error::InvalidDescriptor {
99                tag: TAG,
100                reason: "PDC_descriptor length must be exactly 3",
101            });
102        }
103        let end = HEADER_LEN + length;
104        if bytes.len() < end {
105            return Err(Error::BufferTooShort {
106                need: end,
107                have: bytes.len(),
108                what: "PdcDescriptor body",
109            });
110        }
111        // 24-bit big-endian field; top 4 bits reserved (ignored on parse).
112        let raw = (u32::from(bytes[HEADER_LEN]) << 16)
113            | (u32::from(bytes[HEADER_LEN + 1]) << 8)
114            | u32::from(bytes[HEADER_LEN + 2]);
115        Ok(Self {
116            programme_identification_label: raw & PIL_MASK,
117        })
118    }
119}
120
121impl Serialize for PdcDescriptor {
122    type Error = crate::error::Error;
123    fn serialized_len(&self) -> usize {
124        HEADER_LEN + BODY_LEN
125    }
126
127    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
128        if self.programme_identification_label > PIL_MASK {
129            return Err(Error::InvalidDescriptor {
130                tag: TAG,
131                reason: "programme_identification_label exceeds 20 bits",
132            });
133        }
134        let len = self.serialized_len();
135        if buf.len() < len {
136            return Err(Error::OutputBufferTooSmall {
137                need: len,
138                have: buf.len(),
139            });
140        }
141        buf[0] = TAG;
142        buf[1] = BODY_LEN as u8;
143        // Reserved 4 bits emitted as 1s.
144        let raw = RESERVED_BITS | (self.programme_identification_label & PIL_MASK);
145        buf[HEADER_LEN] = (raw >> 16) as u8;
146        buf[HEADER_LEN + 1] = (raw >> 8) as u8;
147        buf[HEADER_LEN + 2] = raw as u8;
148        Ok(len)
149    }
150}
151
152impl<'a> Descriptor<'a> for PdcDescriptor {
153    const TAG: u8 = TAG;
154    fn descriptor_length(&self) -> u8 {
155        BODY_LEN as u8
156    }
157}
158
159impl<'a> crate::traits::DescriptorDef<'a> for PdcDescriptor {
160    const TAG: u8 = TAG;
161    const NAME: &'static str = "PDC";
162}
163
164#[cfg(test)]
165mod tests {
166    use super::*;
167
168    #[test]
169    fn parse_extracts_pil() {
170        // body 0x0A_BCDE: top nibble reserved (0), PIL = 0x0ABCDE.
171        let bytes = [TAG, 3, 0x0A, 0xBC, 0xDE];
172        let d = PdcDescriptor::parse(&bytes).unwrap();
173        assert_eq!(d.programme_identification_label, 0x0A_BCDE);
174    }
175
176    #[test]
177    fn parse_ignores_reserved_bits() {
178        // Top nibble set (reserved) must be masked off, not rejected (§5.1).
179        let bytes = [TAG, 3, 0xFA, 0xBC, 0xDE];
180        let d = PdcDescriptor::parse(&bytes).unwrap();
181        assert_eq!(d.programme_identification_label, 0x0A_BCDE);
182    }
183
184    #[test]
185    fn parse_rejects_wrong_tag() {
186        assert!(matches!(
187            PdcDescriptor::parse(&[0x6A, 3, 0, 0, 0]).unwrap_err(),
188            Error::InvalidDescriptor { tag: 0x6A, .. }
189        ));
190    }
191
192    #[test]
193    fn parse_rejects_wrong_length() {
194        assert!(matches!(
195            PdcDescriptor::parse(&[TAG, 2, 0, 0]).unwrap_err(),
196            Error::InvalidDescriptor { tag: TAG, .. }
197        ));
198    }
199
200    #[test]
201    fn parse_rejects_short_body() {
202        assert!(matches!(
203            PdcDescriptor::parse(&[TAG, 3, 0, 0]).unwrap_err(),
204            Error::BufferTooShort { .. }
205        ));
206    }
207
208    #[test]
209    fn serialize_round_trip() {
210        let d = PdcDescriptor {
211            programme_identification_label: 0x0A_BCDE,
212        };
213        let mut buf = vec![0u8; d.serialized_len()];
214        d.serialize_into(&mut buf).unwrap();
215        // Reserved nibble emitted as 1s.
216        assert_eq!(buf, [TAG, 3, 0xFA, 0xBC, 0xDE]);
217        assert_eq!(PdcDescriptor::parse(&buf).unwrap(), d);
218    }
219
220    #[test]
221    fn serialize_rejects_too_small_buffer() {
222        let d = PdcDescriptor {
223            programme_identification_label: 0,
224        };
225        let mut buf = vec![0u8; 2];
226        assert!(matches!(
227            d.serialize_into(&mut buf).unwrap_err(),
228            Error::OutputBufferTooSmall { .. }
229        ));
230    }
231
232    #[test]
233    fn serialize_rejects_over_range_pil() {
234        let d = PdcDescriptor {
235            programme_identification_label: 0x10_0000, // 21 bits
236        };
237        let mut buf = vec![0u8; d.serialized_len()];
238        assert!(matches!(
239            d.serialize_into(&mut buf).unwrap_err(),
240            Error::InvalidDescriptor { tag: TAG, .. }
241        ));
242    }
243
244    #[cfg(feature = "serde")]
245    #[test]
246    fn serde_round_trip() {
247        let d = PdcDescriptor {
248            programme_identification_label: 0x0A_BCDE,
249        };
250        let json = serde_json::to_string(&d).unwrap();
251        // Serialize-only: assert the emitted JSON re-parses (serialize-stable).
252        let _v: serde_json::Value = serde_json::from_str(&json).unwrap();
253    }
254}
dvb_si/descriptors/pdc.rs

dvb_si/descriptors/
pdc.rs
