dvb-si 7.6.0

ETSI EN 300 468 DVB Service Information parser + builder. MPEG-2 PSI included.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140

//! Audio Stream Descriptor — ISO/IEC 13818-1 §2.6.4 (tag 0x03).
//!
//! Describes the elementary stream as an MPEG audio stream.

use super::descriptor_body;
use crate::error::{Error, Result};
use dvb_common::{Parse, Serialize};

/// Descriptor tag for audio_stream_descriptor.
pub const TAG: u8 = 0x03;
const HEADER_LEN: usize = 2;
const BODY_LEN: u8 = 1;

/// Audio Stream Descriptor.
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize))]
#[cfg_attr(feature = "yoke", derive(yoke::Yokeable))]
pub struct AudioStreamDescriptor {
    /// Free format flag.
    pub free_format_flag: bool,
    /// MPEG audio ID.
    pub id: bool,
    /// Layer (0=reserved).
    pub layer: u8,
    /// Variable rate audio indicator.
    pub variable_rate_audio_indicator: bool,
}

impl<'a> Parse<'a> for AudioStreamDescriptor {
    type Error = crate::error::Error;

    fn parse(bytes: &'a [u8]) -> Result<Self> {
        let body = descriptor_body(
            bytes,
            TAG,
            "AudioStreamDescriptor",
            "unexpected tag for audio_stream_descriptor",
        )?;
        if body.len() != BODY_LEN as usize {
            return Err(Error::InvalidDescriptor {
                tag: TAG,
                reason: "audio_stream_descriptor length must equal 1",
            });
        }
        let b = body[0];
        Ok(Self {
            free_format_flag: (b & 0x80) != 0,
            id: (b & 0x40) != 0,
            layer: (b >> 4) & 0x03,
            variable_rate_audio_indicator: (b & 0x08) != 0,
        })
    }
}

impl Serialize for AudioStreamDescriptor {
    type Error = crate::error::Error;

    fn serialized_len(&self) -> usize {
        HEADER_LEN + (BODY_LEN as usize)
    }

    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
        let len = self.serialized_len();
        if buf.len() < len {
            return Err(Error::OutputBufferTooSmall {
                need: len,
                have: buf.len(),
            });
        }
        buf[0] = TAG;
        buf[1] = BODY_LEN;
        buf[HEADER_LEN] = ((self.free_format_flag as u8) << 7)
            | ((self.id as u8) << 6)
            | ((self.layer & 0x03) << 4)
            | ((self.variable_rate_audio_indicator as u8) << 3);
        Ok(len)
    }
}
impl<'a> crate::traits::DescriptorDef<'a> for AudioStreamDescriptor {
    const TAG: u8 = TAG;
    const NAME: &'static str = "AUDIO_STREAM";
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn parse() {
        let bytes = [
            TAG,
            1,
            0b1110_1000, // free=1, id=1, layer=2, variable=1, reserved=0
        ];
        let d = AudioStreamDescriptor::parse(&bytes).unwrap();
        assert!(d.free_format_flag);
        assert!(d.id);
        assert_eq!(d.layer, 2);
        assert!(d.variable_rate_audio_indicator);
    }

    #[test]
    fn serialize_round_trip() {
        let d = AudioStreamDescriptor {
            free_format_flag: false,
            id: true,
            layer: 3,
            variable_rate_audio_indicator: false,
        };
        let mut buf = vec![0u8; d.serialized_len()];
        d.serialize_into(&mut buf).unwrap();
        let reparsed = AudioStreamDescriptor::parse(&buf).unwrap();
        assert_eq!(d, reparsed);
    }

    #[test]
    fn parse_rejects_wrong_length() {
        let err = AudioStreamDescriptor::parse(&[TAG, 0]).unwrap_err();
        assert!(matches!(err, Error::InvalidDescriptor { tag: TAG, .. }));
    }

    #[test]
    fn parse_rejects_wrong_tag() {
        let err = AudioStreamDescriptor::parse(&[0x04, 1, 0x00]).unwrap_err();
        assert!(matches!(err, Error::InvalidDescriptor { tag: 0x04, .. }));
    }

    #[test]
    fn serialize_rejects_small_buffer() {
        let d = AudioStreamDescriptor {
            free_format_flag: false,
            id: false,
            layer: 0,
            variable_rate_audio_indicator: false,
        };
        let mut tiny = vec![0u8; 2];
        let err = d.serialize_into(&mut tiny).unwrap_err();
        assert!(matches!(err, Error::OutputBufferTooSmall { .. }));
    }
}