dvb_si/descriptors/
country_availability.rs

1//! Country Availability Descriptor — ETSI EN 300 468 §6.2.10 (tag 0x49).
2//!
3//! Table 30 (PDF p. 70). Carried in SDT/BAT descriptor loops. A flag byte
4//! (`country_availability_flag` MSB + 7 reserved bits) followed by a loop of
5//! 3-byte ISO 3166 country codes. When the flag is set, the service is
6//! intended for reception in the listed countries; when clear, in all
7//! countries EXCEPT those listed.
8
9use crate::error::{Error, Result};
10use crate::text::LangCode;
11use crate::traits::Descriptor;
12use dvb_common::{Parse, Serialize};
13
14/// Descriptor tag for country_availability_descriptor.
15pub const TAG: u8 = 0x49;
16const HEADER_LEN: usize = 2;
17const FLAG_LEN: usize = 1;
18const COUNTRY_CODE_LEN: usize = 3;
19const MIN_BODY_LEN: usize = FLAG_LEN;
20/// Maximum body length expressible in the 8-bit `descriptor_length` field.
21const MAX_BODY_LEN: usize = u8::MAX as usize;
22/// country_availability_flag occupies bit 7 (MSB) of the flag byte.
23const AVAILABILITY_FLAG_MASK: u8 = 0x80;
24/// Lower 7 bits are reserved_future_use — emitted as 1s on serialize.
25const RESERVED_MASK: u8 = 0x7F;
26
27/// Country Availability Descriptor.
28#[derive(Debug, Clone, PartialEq, Eq)]
29#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
30pub struct CountryAvailabilityDescriptor {
31    /// true = available in the listed countries; false = available everywhere
32    /// EXCEPT the listed countries.
33    pub country_availability_flag: bool,
34    /// ISO 3166 alpha-3 country codes in wire order.
35    pub country_codes: Vec<LangCode>,
36}
37
38impl<'a> Parse<'a> for CountryAvailabilityDescriptor {
39    type Error = crate::error::Error;
40    fn parse(bytes: &'a [u8]) -> Result<Self> {
41        if bytes.len() < HEADER_LEN {
42            return Err(Error::BufferTooShort {
43                need: HEADER_LEN,
44                have: bytes.len(),
45                what: "CountryAvailabilityDescriptor header",
46            });
47        }
48        if bytes[0] != TAG {
49            return Err(Error::InvalidDescriptor {
50                tag: bytes[0],
51                reason: "unexpected tag for country_availability_descriptor",
52            });
53        }
54        let length = bytes[1] as usize;
55        if length < MIN_BODY_LEN {
56            return Err(Error::InvalidDescriptor {
57                tag: TAG,
58                reason: "country_availability_descriptor missing flag byte",
59            });
60        }
61        if (length - FLAG_LEN) % COUNTRY_CODE_LEN != 0 {
62            return Err(Error::InvalidDescriptor {
63                tag: TAG,
64                reason: "country_code loop length must be a multiple of 3",
65            });
66        }
67        let end = HEADER_LEN + length;
68        if bytes.len() < end {
69            return Err(Error::BufferTooShort {
70                need: end,
71                have: bytes.len(),
72                what: "CountryAvailabilityDescriptor body",
73            });
74        }
75        let flags = bytes[HEADER_LEN];
76        // reserved_future_use bits ignored on parse (EN 300 468 §5.1).
77        let country_availability_flag = flags & AVAILABILITY_FLAG_MASK != 0;
78        let loop_body = &bytes[HEADER_LEN + FLAG_LEN..end];
79        let mut country_codes = Vec::with_capacity(loop_body.len() / COUNTRY_CODE_LEN);
80        for chunk in loop_body.chunks_exact(COUNTRY_CODE_LEN) {
81            country_codes.push(LangCode([chunk[0], chunk[1], chunk[2]]));
82        }
83        Ok(Self {
84            country_availability_flag,
85            country_codes,
86        })
87    }
88}
89
90impl Serialize for CountryAvailabilityDescriptor {
91    type Error = crate::error::Error;
92    fn serialized_len(&self) -> usize {
93        HEADER_LEN + FLAG_LEN + COUNTRY_CODE_LEN * self.country_codes.len()
94    }
95
96    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
97        let len = self.serialized_len();
98        if buf.len() < len {
99            return Err(Error::OutputBufferTooSmall {
100                need: len,
101                have: buf.len(),
102            });
103        }
104        let body_len = FLAG_LEN + COUNTRY_CODE_LEN * self.country_codes.len();
105        // 8-bit descriptor_length field: error rather than silently truncate.
106        if body_len > MAX_BODY_LEN {
107            return Err(Error::SectionLengthOverflow {
108                declared: body_len,
109                available: MAX_BODY_LEN,
110            });
111        }
112        buf[0] = TAG;
113        buf[1] = body_len as u8;
114        // reserved_future_use bits emitted as 1s (EN 300 468 §5.1).
115        let flag_bit = if self.country_availability_flag {
116            AVAILABILITY_FLAG_MASK
117        } else {
118            0
119        };
120        buf[HEADER_LEN] = flag_bit | RESERVED_MASK;
121        let mut pos = HEADER_LEN + FLAG_LEN;
122        for code in &self.country_codes {
123            buf[pos..pos + COUNTRY_CODE_LEN].copy_from_slice(&code.0);
124            pos += COUNTRY_CODE_LEN;
125        }
126        Ok(len)
127    }
128}
129
130impl<'a> Descriptor<'a> for CountryAvailabilityDescriptor {
131    const TAG: u8 = TAG;
132    fn descriptor_length(&self) -> u8 {
133        (FLAG_LEN + COUNTRY_CODE_LEN * self.country_codes.len()) as u8
134    }
135}
136
137impl<'a> crate::traits::DescriptorDef<'a> for CountryAvailabilityDescriptor {
138    const TAG: u8 = TAG;
139    const NAME: &'static str = "COUNTRY_AVAILABILITY";
140}
141
142#[cfg(test)]
143mod tests {
144    use super::*;
145
146    #[test]
147    fn parse_available_with_countries() {
148        // flag=1 (0x80) + reserved 1s ignored, two country codes
149        let bytes = [TAG, 7, 0xFF, b'G', b'B', b'R', b'F', b'R', b'A'];
150        let d = CountryAvailabilityDescriptor::parse(&bytes).unwrap();
151        assert!(d.country_availability_flag);
152        assert_eq!(d.country_codes, vec![LangCode(*b"GBR"), LangCode(*b"FRA")]);
153    }
154
155    #[test]
156    fn parse_flag_clear() {
157        let bytes = [TAG, 4, 0x7F, b'D', b'E', b'U'];
158        let d = CountryAvailabilityDescriptor::parse(&bytes).unwrap();
159        assert!(!d.country_availability_flag);
160        assert_eq!(d.country_codes, vec![LangCode(*b"DEU")]);
161    }
162
163    #[test]
164    fn parse_flag_only_no_countries() {
165        let bytes = [TAG, 1, 0x80];
166        let d = CountryAvailabilityDescriptor::parse(&bytes).unwrap();
167        assert!(d.country_availability_flag);
168        assert!(d.country_codes.is_empty());
169    }
170
171    #[test]
172    fn parse_rejects_wrong_tag() {
173        assert!(matches!(
174            CountryAvailabilityDescriptor::parse(&[0x4A, 1, 0x80]).unwrap_err(),
175            Error::InvalidDescriptor { tag: 0x4A, .. }
176        ));
177    }
178
179    #[test]
180    fn parse_rejects_short_buffer() {
181        // declares 7 body bytes, only 4 present
182        let bytes = [TAG, 7, 0x80, b'G', b'B'];
183        assert!(matches!(
184            CountryAvailabilityDescriptor::parse(&bytes).unwrap_err(),
185            Error::BufferTooShort { .. }
186        ));
187    }
188
189    #[test]
190    fn parse_rejects_loop_not_multiple_of_3() {
191        // 1 flag byte + 2 loop bytes — loop not a multiple of 3
192        let bytes = [TAG, 3, 0x80, b'G', b'B'];
193        assert!(matches!(
194            CountryAvailabilityDescriptor::parse(&bytes).unwrap_err(),
195            Error::InvalidDescriptor { tag: TAG, .. }
196        ));
197    }
198
199    #[test]
200    fn parse_rejects_zero_length() {
201        let bytes = [TAG, 0];
202        assert!(matches!(
203            CountryAvailabilityDescriptor::parse(&bytes).unwrap_err(),
204            Error::InvalidDescriptor { tag: TAG, .. }
205        ));
206    }
207
208    #[test]
209    fn serialize_round_trip() {
210        let d = CountryAvailabilityDescriptor {
211            country_availability_flag: true,
212            country_codes: vec![LangCode(*b"GBR"), LangCode(*b"IRL")],
213        };
214        let mut buf = vec![0u8; d.serialized_len()];
215        d.serialize_into(&mut buf).unwrap();
216        assert_eq!(CountryAvailabilityDescriptor::parse(&buf).unwrap(), d);
217    }
218
219    #[test]
220    fn serialize_emits_reserved_ones() {
221        let d = CountryAvailabilityDescriptor {
222            country_availability_flag: false,
223            country_codes: vec![],
224        };
225        let mut buf = vec![0u8; d.serialized_len()];
226        d.serialize_into(&mut buf).unwrap();
227        // flag clear, reserved bits all 1 -> 0x7F
228        assert_eq!(buf[HEADER_LEN], 0x7F);
229    }
230
231    #[cfg(feature = "serde")]
232    #[test]
233    fn serde_round_trip() {
234        let d = CountryAvailabilityDescriptor {
235            country_availability_flag: true,
236            country_codes: vec![LangCode(*b"FRA")],
237        };
238        let json = serde_json::to_string(&d).unwrap();
239        let back: CountryAvailabilityDescriptor = serde_json::from_str(&json).unwrap();
240        assert_eq!(d, back);
241    }
242}
dvb_si/descriptors/country_availability.rs

dvb_si/descriptors/
country_availability.rs
