dvb_si/descriptors/
private_data_specifier.rs

1//! Private Data Specifier Descriptor — ETSI EN 300 468 §6.2.31 (tag 0x5F).
2//!
3//! Table 85 (PDF p. 98). A single 32-bit `private_data_specifier` value
4//! (registered in EN 300 468 Annex/TR 101 162) that scopes the interpretation
5//! of any subsequent private (user-defined) descriptors in the same loop.
6
7use crate::error::{Error, Result};
8use crate::traits::Descriptor;
9use dvb_common::{Parse, Serialize};
10
11/// Descriptor tag for private_data_specifier_descriptor.
12pub const TAG: u8 = 0x5F;
13const HEADER_LEN: usize = 2;
14/// Fixed payload length: a single 32-bit specifier (EN 300 468 Table 85).
15const BODY_LEN: u8 = 4;
16
17/// Private Data Specifier Descriptor (tag 0x5F).
18#[derive(Debug, Clone, PartialEq, Eq)]
19#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
20pub struct PrivateDataSpecifierDescriptor {
21    /// 32-bit registered private_data_specifier (ETSI Table 85, PDF p. 98).
22    pub private_data_specifier: u32,
23}
24
25impl<'a> Parse<'a> for PrivateDataSpecifierDescriptor {
26    type Error = crate::error::Error;
27    fn parse(bytes: &'a [u8]) -> Result<Self> {
28        if bytes.len() < HEADER_LEN {
29            return Err(Error::BufferTooShort {
30                need: HEADER_LEN,
31                have: bytes.len(),
32                what: "PrivateDataSpecifierDescriptor header",
33            });
34        }
35        if bytes[0] != TAG {
36            return Err(Error::InvalidDescriptor {
37                tag: bytes[0],
38                reason: "unexpected tag for private_data_specifier_descriptor",
39            });
40        }
41        let length = bytes[1] as usize;
42        let total = HEADER_LEN + length;
43        if bytes.len() < total {
44            return Err(Error::BufferTooShort {
45                need: total,
46                have: bytes.len(),
47                what: "PrivateDataSpecifierDescriptor body",
48            });
49        }
50        if length != BODY_LEN as usize {
51            return Err(Error::InvalidDescriptor {
52                tag: TAG,
53                reason: "private_data_specifier_descriptor length must equal 4",
54            });
55        }
56        let private_data_specifier = u32::from_be_bytes([
57            bytes[HEADER_LEN],
58            bytes[HEADER_LEN + 1],
59            bytes[HEADER_LEN + 2],
60            bytes[HEADER_LEN + 3],
61        ]);
62        Ok(Self {
63            private_data_specifier,
64        })
65    }
66}
67
68impl Serialize for PrivateDataSpecifierDescriptor {
69    type Error = crate::error::Error;
70    fn serialized_len(&self) -> usize {
71        HEADER_LEN + BODY_LEN as usize
72    }
73
74    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
75        let len = self.serialized_len();
76        if buf.len() < len {
77            return Err(Error::OutputBufferTooSmall {
78                need: len,
79                have: buf.len(),
80            });
81        }
82        buf[0] = TAG;
83        buf[1] = BODY_LEN;
84        buf[HEADER_LEN..HEADER_LEN + 4].copy_from_slice(&self.private_data_specifier.to_be_bytes());
85        Ok(len)
86    }
87}
88
89impl<'a> Descriptor<'a> for PrivateDataSpecifierDescriptor {
90    const TAG: u8 = TAG;
91    fn descriptor_length(&self) -> u8 {
92        BODY_LEN
93    }
94}
95
96#[cfg(test)]
97mod tests {
98    use super::*;
99
100    #[test]
101    fn parse_extracts_specifier() {
102        let bytes = [TAG, 4, 0x00, 0x00, 0x00, 0x28];
103        let d = PrivateDataSpecifierDescriptor::parse(&bytes).unwrap();
104        assert_eq!(d.private_data_specifier, 0x0000_0028);
105    }
106
107    #[test]
108    fn parse_rejects_wrong_tag() {
109        let err = PrivateDataSpecifierDescriptor::parse(&[0x60, 4, 0, 0, 0, 0]).unwrap_err();
110        assert!(matches!(err, Error::InvalidDescriptor { tag: 0x60, .. }));
111    }
112
113    #[test]
114    fn parse_rejects_short_buffer() {
115        let err = PrivateDataSpecifierDescriptor::parse(&[TAG]).unwrap_err();
116        assert!(matches!(err, Error::BufferTooShort { .. }));
117    }
118
119    #[test]
120    fn parse_rejects_truncated_body() {
121        // length=4 but only 2 payload bytes present.
122        let err = PrivateDataSpecifierDescriptor::parse(&[TAG, 4, 0, 0]).unwrap_err();
123        assert!(matches!(err, Error::BufferTooShort { .. }));
124    }
125
126    #[test]
127    fn parse_rejects_wrong_length() {
128        let err = PrivateDataSpecifierDescriptor::parse(&[TAG, 3, 0, 0, 0]).unwrap_err();
129        assert!(matches!(err, Error::InvalidDescriptor { .. }));
130    }
131
132    #[test]
133    fn serialize_round_trip() {
134        let d = PrivateDataSpecifierDescriptor {
135            private_data_specifier: 0xDEAD_BEEF,
136        };
137        let mut buf = vec![0u8; d.serialized_len()];
138        d.serialize_into(&mut buf).unwrap();
139        let re = PrivateDataSpecifierDescriptor::parse(&buf).unwrap();
140        assert_eq!(d, re);
141    }
142
143    #[test]
144    fn serialize_rejects_too_small_buffer() {
145        let d = PrivateDataSpecifierDescriptor {
146            private_data_specifier: 1,
147        };
148        let mut tiny = [0u8; 3];
149        let err = d.serialize_into(&mut tiny).unwrap_err();
150        assert!(matches!(err, Error::OutputBufferTooSmall { .. }));
151    }
152
153    #[test]
154    fn descriptor_length_matches_payload() {
155        let d = PrivateDataSpecifierDescriptor {
156            private_data_specifier: 0,
157        };
158        assert_eq!(d.descriptor_length(), 4);
159    }
160
161    #[cfg(feature = "serde")]
162    #[test]
163    fn serde_round_trip() {
164        let d = PrivateDataSpecifierDescriptor {
165            private_data_specifier: 0x0000_233A,
166        };
167        let json = serde_json::to_string(&d).unwrap();
168        let back: PrivateDataSpecifierDescriptor = serde_json::from_str(&json).unwrap();
169        assert_eq!(d, back);
170    }
171}
dvb_si/descriptors/private_data_specifier.rs

dvb_si/descriptors/
private_data_specifier.rs
