dvb_si/descriptors/
iod.rs

1//! IOD Descriptor — ISO/IEC 13818-1 §2.6.40, Table 2-75 (tag 0x1D).
2//!
3//! Carries an InitialObjectDescriptor() from ISO/IEC 14496-1 §8.6.3.1 as
4//! opaque bytes after the Scope_of_IOD_label and IOD_label fields.
5
6use super::descriptor_body;
7use crate::error::{Error, Result};
8use dvb_common::{Parse, Serialize};
9
10/// Descriptor tag for IOD_descriptor.
11pub const TAG: u8 = 0x1D;
12const HEADER_LEN: usize = 2;
13const FIXED_LEN: usize = 2;
14
15/// IOD Descriptor.
16#[derive(Debug, Clone, PartialEq, Eq)]
17#[cfg_attr(feature = "serde", derive(serde::Serialize))]
18#[cfg_attr(feature = "yoke", derive(yoke::Yokeable))]
19pub struct IodDescriptor<'a> {
20    /// Scope of the IOD label.
21    pub scope_of_iod_label: u8,
22    /// IOD label.
23    pub iod_label: u8,
24    /// InitialObjectDescriptor() carried as opaque bytes.
25    #[cfg_attr(feature = "serde", serde(borrow))]
26    pub initial_object_descriptor: &'a [u8],
27}
28
29impl<'a> Parse<'a> for IodDescriptor<'a> {
30    type Error = crate::error::Error;
31
32    fn parse(bytes: &'a [u8]) -> Result<Self> {
33        let body = descriptor_body(
34            bytes,
35            TAG,
36            "IodDescriptor",
37            "unexpected tag for IOD_descriptor",
38        )?;
39        if body.len() < FIXED_LEN {
40            return Err(Error::InvalidDescriptor {
41                tag: TAG,
42                reason: "IOD_descriptor length too short (need >= 2)",
43            });
44        }
45        Ok(Self {
46            scope_of_iod_label: body[0],
47            iod_label: body[1],
48            initial_object_descriptor: &body[FIXED_LEN..],
49        })
50    }
51}
52
53impl Serialize for IodDescriptor<'_> {
54    type Error = crate::error::Error;
55
56    fn serialized_len(&self) -> usize {
57        HEADER_LEN + FIXED_LEN + self.initial_object_descriptor.len()
58    }
59
60    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
61        let len = self.serialized_len();
62        if buf.len() < len {
63            return Err(Error::OutputBufferTooSmall {
64                need: len,
65                have: buf.len(),
66            });
67        }
68        buf[0] = TAG;
69        buf[1] = (len - HEADER_LEN) as u8;
70        buf[HEADER_LEN] = self.scope_of_iod_label;
71        buf[HEADER_LEN + 1] = self.iod_label;
72        buf[HEADER_LEN + FIXED_LEN..len].copy_from_slice(self.initial_object_descriptor);
73        Ok(len)
74    }
75}
76impl<'a> crate::traits::DescriptorDef<'a> for IodDescriptor<'a> {
77    const TAG: u8 = TAG;
78    const NAME: &'static str = "IOD";
79}
80
81#[cfg(test)]
82mod tests {
83    use super::*;
84
85    #[test]
86    fn parse_minimal() {
87        let bytes = [TAG, 2, 0x01, 0x02];
88        let d = IodDescriptor::parse(&bytes).unwrap();
89        assert_eq!(d.scope_of_iod_label, 0x01);
90        assert_eq!(d.iod_label, 0x02);
91        assert!(d.initial_object_descriptor.is_empty());
92    }
93
94    #[test]
95    fn parse_with_opaque() {
96        let bytes = [TAG, 5, 0x0A, 0x0B, 0xCC, 0xDD, 0xEE];
97        let d = IodDescriptor::parse(&bytes).unwrap();
98        assert_eq!(d.scope_of_iod_label, 0x0A);
99        assert_eq!(d.iod_label, 0x0B);
100        assert_eq!(d.initial_object_descriptor, &[0xCC, 0xDD, 0xEE]);
101    }
102
103    #[test]
104    fn serialize_round_trip() {
105        let d = IodDescriptor {
106            scope_of_iod_label: 0x03,
107            iod_label: 0x04,
108            initial_object_descriptor: &[0xAA, 0xBB],
109        };
110        let mut buf = vec![0u8; d.serialized_len()];
111        d.serialize_into(&mut buf).unwrap();
112        let reparsed = IodDescriptor::parse(&buf).unwrap();
113        assert_eq!(d, reparsed);
114    }
115
116    #[test]
117    fn parse_rejects_wrong_tag() {
118        let err = IodDescriptor::parse(&[0x02, 2, 0, 0]).unwrap_err();
119        assert!(matches!(err, Error::InvalidDescriptor { tag: 0x02, .. }));
120    }
121
122    #[test]
123    fn parse_rejects_too_short() {
124        let err = IodDescriptor::parse(&[TAG, 1, 0]).unwrap_err();
125        assert!(matches!(err, Error::InvalidDescriptor { tag: TAG, .. }));
126    }
127
128    #[test]
129    fn serialize_rejects_small_buffer() {
130        let d = IodDescriptor {
131            scope_of_iod_label: 0,
132            iod_label: 0,
133            initial_object_descriptor: &[],
134        };
135        let mut tiny = vec![0u8; 3];
136        let err = d.serialize_into(&mut tiny).unwrap_err();
137        assert!(matches!(err, Error::OutputBufferTooSmall { .. }));
138    }
139}
dvb_si/descriptors/iod.rs

dvb_si/descriptors/
iod.rs
