dvb_si/descriptors/
service_list.rs

1//! Service List Descriptor — ETSI EN 300 468 §6.2.36 (tag 0x41).
2//!
3//! Carried inside NIT/BAT transport_stream_loop second descriptor loop.
4//! Enumerates the service_id/service_type pairs available on the TS.
5
6use super::descriptor_body;
7use super::service::ServiceType;
8use crate::error::{Error, Result};
9use dvb_common::{Parse, Serialize};
10
11/// Descriptor tag for service_list_descriptor.
12pub const TAG: u8 = 0x41;
13const HEADER_LEN: usize = 2;
14const ENTRY_LEN: usize = 3;
15
16/// One (service_id, service_type) pair.
17#[derive(Debug, Clone, Copy, PartialEq, Eq)]
18#[cfg_attr(feature = "serde", derive(serde::Serialize))]
19pub struct ServiceListEntry {
20    /// DVB service_id (matches program_number in PAT).
21    pub service_id: u16,
22    /// service_type (ETSI Table 89).
23    pub service_type: ServiceType,
24}
25
26/// Service List Descriptor.
27#[derive(Debug, Clone, PartialEq, Eq)]
28#[cfg_attr(feature = "serde", derive(serde::Serialize))]
29pub struct ServiceListDescriptor {
30    /// Entries in wire order.
31    pub entries: Vec<ServiceListEntry>,
32}
33
34impl<'a> Parse<'a> for ServiceListDescriptor {
35    type Error = crate::error::Error;
36    fn parse(bytes: &'a [u8]) -> Result<Self> {
37        let body = descriptor_body(
38            bytes,
39            TAG,
40            "ServiceListDescriptor",
41            "unexpected tag for service_list_descriptor",
42        )?;
43        if body.len() % 3 != 0 {
44            return Err(Error::InvalidDescriptor {
45                tag: TAG,
46                reason: "descriptor_length must be a multiple of 3",
47            });
48        }
49        let mut entries = Vec::with_capacity(body.len() / ENTRY_LEN);
50        let mut offset = 0;
51        while offset < body.len() {
52            let service_id = u16::from_be_bytes([body[offset], body[offset + 1]]);
53            let service_type = ServiceType::from_u8(body[offset + 2]);
54            entries.push(ServiceListEntry {
55                service_id,
56                service_type,
57            });
58            offset += ENTRY_LEN;
59        }
60        Ok(Self { entries })
61    }
62}
63
64impl Serialize for ServiceListDescriptor {
65    type Error = crate::error::Error;
66    fn serialized_len(&self) -> usize {
67        HEADER_LEN + ENTRY_LEN * self.entries.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] = (len - HEADER_LEN) as u8;
80        let mut offset = HEADER_LEN;
81        for entry in &self.entries {
82            buf[offset..offset + 2].copy_from_slice(&entry.service_id.to_be_bytes());
83            buf[offset + 2] = entry.service_type.to_u8();
84            offset += ENTRY_LEN;
85        }
86        Ok(len)
87    }
88}
89impl<'a> crate::traits::DescriptorDef<'a> for ServiceListDescriptor {
90    const TAG: u8 = TAG;
91    const NAME: &'static str = "SERVICE_LIST";
92}
93
94#[cfg(test)]
95mod tests {
96    use super::*;
97
98    #[test]
99    fn parse_single_entry() {
100        let bytes = [TAG, 3, 0x00, 0x01, 0x01];
101        let d = ServiceListDescriptor::parse(&bytes).unwrap();
102        assert_eq!(d.entries.len(), 1);
103        assert_eq!(d.entries[0].service_id, 1);
104        assert_eq!(d.entries[0].service_type, ServiceType::DigitalTelevision);
105    }
106
107    #[test]
108    fn parse_multiple_entries_preserves_order() {
109        let bytes = [TAG, 9, 0x00, 0x01, 0x01, 0x00, 0x02, 0x02, 0x00, 0x03, 0x03];
110        let d = ServiceListDescriptor::parse(&bytes).unwrap();
111        assert_eq!(d.entries.len(), 3);
112        assert_eq!(d.entries[0].service_id, 1);
113        assert_eq!(d.entries[0].service_type, ServiceType::DigitalTelevision);
114        assert_eq!(d.entries[1].service_id, 2);
115        assert_eq!(d.entries[1].service_type, ServiceType::DigitalRadioSound);
116        assert_eq!(d.entries[2].service_id, 3);
117        assert_eq!(d.entries[2].service_type, ServiceType::Teletext);
118    }
119
120    #[test]
121    fn parse_rejects_wrong_tag() {
122        let err = ServiceListDescriptor::parse(&[0x42, 3, 0x00, 0x01, 0x01]).unwrap_err();
123        assert!(matches!(err, Error::InvalidDescriptor { tag: 0x42, .. }));
124    }
125
126    #[test]
127    fn parse_rejects_length_not_multiple_of_3() {
128        let bytes = [TAG, 4, 0x00, 0x01, 0x01, 0xFF];
129        let err = ServiceListDescriptor::parse(&bytes).unwrap_err();
130        assert!(matches!(err, Error::InvalidDescriptor { tag: TAG, .. }));
131    }
132
133    #[test]
134    fn parse_rejects_truncated_body() {
135        let bytes = [TAG, 6, 0x00, 0x01];
136        let err = ServiceListDescriptor::parse(&bytes).unwrap_err();
137        assert!(matches!(err, Error::BufferTooShort { .. }));
138    }
139
140    #[test]
141    fn empty_descriptor_valid() {
142        let bytes = [TAG, 0];
143        let d = ServiceListDescriptor::parse(&bytes).unwrap();
144        assert!(d.entries.is_empty());
145    }
146
147    #[test]
148    fn serialize_round_trip() {
149        let d = ServiceListDescriptor {
150            entries: vec![
151                ServiceListEntry {
152                    service_id: 1,
153                    service_type: ServiceType::DigitalTelevision,
154                },
155                ServiceListEntry {
156                    service_id: 0x0102,
157                    service_type: ServiceType::NvodReference,
158                },
159            ],
160        };
161        let mut buf = vec![0u8; d.serialized_len()];
162        d.serialize_into(&mut buf).unwrap();
163        let re = ServiceListDescriptor::parse(&buf).unwrap();
164        assert_eq!(d, re);
165    }
166}
dvb_si/descriptors/service_list.rs

dvb_si/descriptors/
service_list.rs
