dvb_si/descriptors/
std.rs

1//! STD Descriptor — ISO/IEC 13818-1 §2.6.32 (tag 0x11).
2//!
3//! Indicates whether the leak method of buffer management is valid.
4
5use super::descriptor_body;
6use crate::error::{Error, Result};
7use dvb_common::{Parse, Serialize};
8
9/// Descriptor tag for STD_descriptor.
10pub const TAG: u8 = 0x11;
11const HEADER_LEN: usize = 2;
12const BODY_LEN: u8 = 1;
13
14/// STD Descriptor.
15#[derive(Debug, Clone, PartialEq, Eq)]
16#[cfg_attr(feature = "serde", derive(serde::Serialize))]
17#[cfg_attr(feature = "yoke", derive(yoke::Yokeable))]
18pub struct StdDescriptor {
19    /// Leak valid flag — 1 means the leak method is applicable.
20    pub leak_valid_flag: bool,
21}
22
23impl<'a> Parse<'a> for StdDescriptor {
24    type Error = crate::error::Error;
25
26    fn parse(bytes: &'a [u8]) -> Result<Self> {
27        let body = descriptor_body(
28            bytes,
29            TAG,
30            "StdDescriptor",
31            "unexpected tag for STD_descriptor",
32        )?;
33        if body.len() != BODY_LEN as usize {
34            return Err(Error::InvalidDescriptor {
35                tag: TAG,
36                reason: "STD_descriptor length must equal 1",
37            });
38        }
39        let leak_valid_flag = (body[0] & 0x01) != 0;
40        Ok(Self { leak_valid_flag })
41    }
42}
43
44impl Serialize for StdDescriptor {
45    type Error = crate::error::Error;
46
47    fn serialized_len(&self) -> usize {
48        HEADER_LEN + (BODY_LEN as usize)
49    }
50
51    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
52        let len = self.serialized_len();
53        if buf.len() < len {
54            return Err(Error::OutputBufferTooSmall {
55                need: len,
56                have: buf.len(),
57            });
58        }
59        buf[0] = TAG;
60        buf[1] = BODY_LEN;
61        buf[HEADER_LEN] = self.leak_valid_flag as u8;
62        Ok(len)
63    }
64}
65impl<'a> crate::traits::DescriptorDef<'a> for StdDescriptor {
66    const TAG: u8 = TAG;
67    const NAME: &'static str = "STD";
68}
69
70#[cfg(test)]
71mod tests {
72    use super::*;
73
74    #[test]
75    fn parse_leak_valid() {
76        let bytes = [TAG, 1, 0b0000_0001];
77        let d = StdDescriptor::parse(&bytes).unwrap();
78        assert!(d.leak_valid_flag);
79    }
80
81    #[test]
82    fn parse_leak_not_valid() {
83        let bytes = [TAG, 1, 0b0000_0000];
84        let d = StdDescriptor::parse(&bytes).unwrap();
85        assert!(!d.leak_valid_flag);
86    }
87
88    #[test]
89    fn serialize_round_trip() {
90        let d = StdDescriptor {
91            leak_valid_flag: true,
92        };
93        let mut buf = vec![0u8; d.serialized_len()];
94        d.serialize_into(&mut buf).unwrap();
95        let reparsed = StdDescriptor::parse(&buf).unwrap();
96        assert_eq!(d, reparsed);
97    }
98
99    #[test]
100    fn parse_rejects_wrong_tag() {
101        let err = StdDescriptor::parse(&[0x12, 1, 0]).unwrap_err();
102        assert!(matches!(err, Error::InvalidDescriptor { tag: 0x12, .. }));
103    }
104
105    #[test]
106    fn parse_rejects_wrong_length() {
107        let err = StdDescriptor::parse(&[TAG, 0]).unwrap_err();
108        assert!(matches!(err, Error::InvalidDescriptor { tag: TAG, .. }));
109    }
110
111    #[test]
112    fn serialize_rejects_small_buffer() {
113        let d = StdDescriptor {
114            leak_valid_flag: false,
115        };
116        let mut tiny = vec![0u8; 2];
117        let err = d.serialize_into(&mut tiny).unwrap_err();
118        assert!(matches!(err, Error::OutputBufferTooSmall { .. }));
119    }
120}
dvb_si/descriptors/std.rs

dvb_si/descriptors/
std.rs
