dvb_si/descriptors/
tva_id.rs

1//! TVA_id Descriptor — ETSI TS 102 323 §11.2.4, Table 114 (tag 0x75).
2//!
3//! Lists one or more TV-Anytime identifiers, each with a running_status that
4//! a receiver uses to drive its recording strategy. Per the TVA PDF
5//! (etsi_ts_102_323_v01.04.01, p. 101, Table 114) each loop entry is 3 bytes:
6//! TVA_id(16) + Reserved(5) + running_status(3). running_status values are
7//! defined in Table 115 (0=reserved, 1=not yet running, 2=starts shortly,
8//! 3=paused, 4=running, 5=cancelled, 6=completed, 7=reserved).
9
10use super::descriptor_body;
11use crate::error::{Error, Result};
12use dvb_common::{Parse, Serialize};
13
14/// Descriptor tag for TVA_id_descriptor.
15pub const TAG: u8 = 0x75;
16const HEADER_LEN: usize = 2;
17const ENTRY_LEN: usize = 3;
18
19/// Largest representable 3-bit running_status.
20const RUNNING_STATUS_MAX: u8 = 0x07;
21
22/// One TVA_id loop entry.
23#[derive(Debug, Clone, PartialEq, Eq)]
24#[cfg_attr(feature = "serde", derive(serde::Serialize))]
25pub struct TvaIdEntry {
26    /// 16-bit TVA_id referencing the item of content.
27    pub tva_id: u16,
28    /// 3-bit running_status (Table 115).
29    pub running_status: u8,
30}
31
32/// TVA_id Descriptor.
33#[derive(Debug, Clone, PartialEq, Eq)]
34#[cfg_attr(feature = "serde", derive(serde::Serialize))]
35pub struct TvaIdDescriptor {
36    /// Entries in wire order.
37    pub entries: Vec<TvaIdEntry>,
38}
39
40impl<'a> Parse<'a> for TvaIdDescriptor {
41    type Error = crate::error::Error;
42    fn parse(bytes: &'a [u8]) -> Result<Self> {
43        let body = descriptor_body(
44            bytes,
45            TAG,
46            "TvaIdDescriptor",
47            "unexpected tag for TVA_id_descriptor",
48        )?;
49        if body.len() % ENTRY_LEN != 0 {
50            return Err(Error::InvalidDescriptor {
51                tag: TAG,
52                reason: "TVA_id_descriptor length must be a multiple of 3",
53            });
54        }
55        let mut entries = Vec::with_capacity(body.len() / ENTRY_LEN);
56        for chunk in body.chunks_exact(ENTRY_LEN) {
57            let tva_id = u16::from_be_bytes([chunk[0], chunk[1]]);
58            // Reserved(5) ignored on parse.
59            let running_status = chunk[2] & RUNNING_STATUS_MAX;
60            entries.push(TvaIdEntry {
61                tva_id,
62                running_status,
63            });
64        }
65        Ok(Self { entries })
66    }
67}
68
69impl Serialize for TvaIdDescriptor {
70    type Error = crate::error::Error;
71    fn serialized_len(&self) -> usize {
72        HEADER_LEN + self.entries.len() * ENTRY_LEN
73    }
74
75    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
76        for e in &self.entries {
77            if e.running_status > RUNNING_STATUS_MAX {
78                return Err(Error::InvalidDescriptor {
79                    tag: TAG,
80                    reason: "running_status exceeds 3 bits",
81                });
82            }
83        }
84        if self.entries.len() * ENTRY_LEN > u8::MAX as usize {
85            return Err(Error::InvalidDescriptor {
86                tag: TAG,
87                reason: "TVA_id_descriptor body exceeds 255 bytes",
88            });
89        }
90        let len = self.serialized_len();
91        if buf.len() < len {
92            return Err(Error::OutputBufferTooSmall {
93                need: len,
94                have: buf.len(),
95            });
96        }
97        buf[0] = TAG;
98        buf[1] = (self.entries.len() * ENTRY_LEN) as u8;
99        let mut pos = HEADER_LEN;
100        for e in &self.entries {
101            buf[pos..pos + 2].copy_from_slice(&e.tva_id.to_be_bytes());
102            // Reserved(5) emitted as 1s.
103            buf[pos + 2] = 0xF8 | (e.running_status & RUNNING_STATUS_MAX);
104            pos += ENTRY_LEN;
105        }
106        Ok(len)
107    }
108}
109impl<'a> crate::traits::DescriptorDef<'a> for TvaIdDescriptor {
110    const TAG: u8 = TAG;
111    const NAME: &'static str = "TVA_ID";
112}
113
114#[cfg(test)]
115mod tests {
116    use super::*;
117
118    #[test]
119    fn parse_single_entry() {
120        // TVA_id=0x1234, running_status=4 (running), reserved bits set.
121        let bytes = [TAG, 3, 0x12, 0x34, 0xFC];
122        let d = TvaIdDescriptor::parse(&bytes).unwrap();
123        assert_eq!(d.entries.len(), 1);
124        assert_eq!(d.entries[0].tva_id, 0x1234);
125        assert_eq!(d.entries[0].running_status, 4);
126    }
127
128    #[test]
129    fn parse_multiple_entries() {
130        let bytes = [TAG, 6, 0x00, 0x01, 0x01, 0xAB, 0xCD, 0x06];
131        let d = TvaIdDescriptor::parse(&bytes).unwrap();
132        assert_eq!(d.entries.len(), 2);
133        assert_eq!(d.entries[0].tva_id, 0x0001);
134        assert_eq!(d.entries[0].running_status, 1);
135        assert_eq!(d.entries[1].tva_id, 0xABCD);
136        assert_eq!(d.entries[1].running_status, 6);
137    }
138
139    #[test]
140    fn parse_ignores_reserved_bits() {
141        let bytes = [TAG, 3, 0x00, 0x00, 0xFF];
142        let d = TvaIdDescriptor::parse(&bytes).unwrap();
143        assert_eq!(d.entries[0].running_status, 0x07);
144    }
145
146    #[test]
147    fn parse_rejects_wrong_tag() {
148        assert!(matches!(
149            TvaIdDescriptor::parse(&[0x74, 0]).unwrap_err(),
150            Error::InvalidDescriptor { tag: 0x74, .. }
151        ));
152    }
153
154    #[test]
155    fn parse_rejects_length_not_multiple_of_3() {
156        let bytes = [TAG, 2, 0, 0];
157        assert!(matches!(
158            TvaIdDescriptor::parse(&bytes).unwrap_err(),
159            Error::InvalidDescriptor { .. }
160        ));
161    }
162
163    #[test]
164    fn empty_descriptor_valid() {
165        let bytes = [TAG, 0];
166        let d = TvaIdDescriptor::parse(&bytes).unwrap();
167        assert!(d.entries.is_empty());
168    }
169
170    #[test]
171    fn serialize_round_trip() {
172        let d = TvaIdDescriptor {
173            entries: vec![
174                TvaIdEntry {
175                    tva_id: 0x1000,
176                    running_status: 2,
177                },
178                TvaIdEntry {
179                    tva_id: 0xFFFF,
180                    running_status: 0,
181                },
182            ],
183        };
184        let mut buf = vec![0u8; d.serialized_len()];
185        d.serialize_into(&mut buf).unwrap();
186        assert_eq!(TvaIdDescriptor::parse(&buf).unwrap(), d);
187    }
188
189    #[test]
190    fn serialize_rejects_running_status_over_range() {
191        let d = TvaIdDescriptor {
192            entries: vec![TvaIdEntry {
193                tva_id: 0,
194                running_status: 0x08,
195            }],
196        };
197        let mut buf = vec![0u8; d.serialized_len()];
198        assert!(matches!(
199            d.serialize_into(&mut buf).unwrap_err(),
200            Error::InvalidDescriptor { .. }
201        ));
202    }
203
204    #[cfg(feature = "serde")]
205    #[test]
206    fn serde_round_trip() {
207        let d = TvaIdDescriptor {
208            entries: vec![TvaIdEntry {
209                tva_id: 0x4242,
210                running_status: 4,
211            }],
212        };
213        let j = serde_json::to_string(&d).unwrap();
214        // Serialize-only: assert the emitted JSON re-parses (serialize-stable).
215        let _v: serde_json::Value = serde_json::from_str(&j).unwrap();
216    }
217}
dvb_si/descriptors/tva_id.rs

dvb_si/descriptors/
tva_id.rs
