dvb_si/descriptors/
external_es_id.rs

1//! External_ES_ID Descriptor — ISO/IEC 13818-1 §2.6.46, Table 2-78 (tag 0x20).
2//!
3//! Carries a single 16-bit External_ES_ID.
4
5use super::descriptor_body;
6use crate::error::{Error, Result};
7use dvb_common::{Parse, Serialize};
8
9/// Descriptor tag for External_ES_ID_descriptor.
10pub const TAG: u8 = 0x20;
11const HEADER_LEN: usize = 2;
12const BODY_LEN: u8 = 2;
13
14/// External_ES_ID Descriptor.
15#[derive(Debug, Clone, Copy, PartialEq, Eq)]
16#[cfg_attr(feature = "serde", derive(serde::Serialize))]
17pub struct ExternalEsIdDescriptor {
18    /// External elementary stream ID.
19    pub external_es_id: u16,
20}
21
22impl<'a> Parse<'a> for ExternalEsIdDescriptor {
23    type Error = crate::error::Error;
24
25    fn parse(bytes: &'a [u8]) -> Result<Self> {
26        let body = descriptor_body(
27            bytes,
28            TAG,
29            "ExternalEsIdDescriptor",
30            "unexpected tag for External_ES_ID_descriptor",
31        )?;
32        if body.len() != BODY_LEN as usize {
33            return Err(Error::InvalidDescriptor {
34                tag: TAG,
35                reason: "External_ES_ID_descriptor length must equal 2",
36            });
37        }
38        Ok(Self {
39            external_es_id: u16::from_be_bytes([body[0], body[1]]),
40        })
41    }
42}
43
44impl Serialize for ExternalEsIdDescriptor {
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..HEADER_LEN + 2].copy_from_slice(&self.external_es_id.to_be_bytes());
62        Ok(len)
63    }
64}
65impl<'a> crate::traits::DescriptorDef<'a> for ExternalEsIdDescriptor {
66    const TAG: u8 = TAG;
67    const NAME: &'static str = "EXTERNAL_ES_ID";
68}
69
70#[cfg(test)]
71mod tests {
72    use super::*;
73
74    #[test]
75    fn parse_extracts_es_id() {
76        let d = ExternalEsIdDescriptor::parse(&[TAG, 2, 0xAB, 0xCD]).unwrap();
77        assert_eq!(d.external_es_id, 0xABCD);
78    }
79
80    #[test]
81    fn parse_rejects_wrong_tag() {
82        let err = ExternalEsIdDescriptor::parse(&[0x02, 2, 0, 0]).unwrap_err();
83        assert!(matches!(err, Error::InvalidDescriptor { tag: 0x02, .. }));
84    }
85
86    #[test]
87    fn parse_rejects_wrong_length() {
88        let err = ExternalEsIdDescriptor::parse(&[TAG, 3, 0, 0, 0]).unwrap_err();
89        assert!(matches!(err, Error::InvalidDescriptor { .. }));
90    }
91
92    #[test]
93    fn parse_rejects_short_buffer() {
94        let err = ExternalEsIdDescriptor::parse(&[TAG]).unwrap_err();
95        assert!(matches!(err, Error::BufferTooShort { .. }));
96    }
97
98    #[test]
99    fn serialize_round_trip() {
100        let d = ExternalEsIdDescriptor {
101            external_es_id: 0xDEAD,
102        };
103        let mut buf = vec![0u8; d.serialized_len()];
104        d.serialize_into(&mut buf).unwrap();
105        assert_eq!(ExternalEsIdDescriptor::parse(&buf).unwrap(), d);
106    }
107}
dvb_si/descriptors/external_es_id.rs

dvb_si/descriptors/
external_es_id.rs
