der/asn1/
null.rs

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1//! ASN.1 `NULL` support.
2
3use crate::{
4    asn1::Any, ByteSlice, DecodeValue, Decoder, Encodable, EncodeValue, Encoder, Error, ErrorKind,
5    FixedTag, Length, OrdIsValueOrd, Result, Tag,
6};
7
8/// ASN.1 `NULL` type.
9#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
10pub struct Null;
11
12impl DecodeValue<'_> for Null {
13    fn decode_value(decoder: &mut Decoder<'_>, length: Length) -> Result<Self> {
14        if length.is_zero() {
15            Ok(Null)
16        } else {
17            Err(decoder.error(ErrorKind::Length { tag: Self::TAG }))
18        }
19    }
20}
21
22impl EncodeValue for Null {
23    fn value_len(&self) -> Result<Length> {
24        Ok(Length::ZERO)
25    }
26
27    fn encode_value(&self, _encoder: &mut Encoder<'_>) -> Result<()> {
28        Ok(())
29    }
30}
31
32impl FixedTag for Null {
33    const TAG: Tag = Tag::Null;
34}
35
36impl OrdIsValueOrd for Null {}
37
38impl<'a> From<Null> for Any<'a> {
39    fn from(_: Null) -> Any<'a> {
40        Any::from_tag_and_value(Tag::Null, ByteSlice::default())
41    }
42}
43
44impl TryFrom<Any<'_>> for Null {
45    type Error = Error;
46
47    fn try_from(any: Any<'_>) -> Result<Null> {
48        any.decode_into()
49    }
50}
51
52impl TryFrom<Any<'_>> for () {
53    type Error = Error;
54
55    fn try_from(any: Any<'_>) -> Result<()> {
56        Null::try_from(any).map(|_| ())
57    }
58}
59
60impl<'a> From<()> for Any<'a> {
61    fn from(_: ()) -> Any<'a> {
62        Null.into()
63    }
64}
65
66impl DecodeValue<'_> for () {
67    fn decode_value(decoder: &mut Decoder<'_>, length: Length) -> Result<Self> {
68        Null::decode_value(decoder, length)?;
69        Ok(())
70    }
71}
72
73impl Encodable for () {
74    fn encoded_len(&self) -> Result<Length> {
75        Null.encoded_len()
76    }
77
78    fn encode(&self, encoder: &mut Encoder<'_>) -> Result<()> {
79        Null.encode(encoder)
80    }
81}
82
83impl FixedTag for () {
84    const TAG: Tag = Tag::Null;
85}
86
87#[cfg(test)]
88mod tests {
89    use super::Null;
90    use crate::{Decodable, Encodable};
91
92    #[test]
93    fn decode() {
94        Null::from_der(&[0x05, 0x00]).unwrap();
95    }
96
97    #[test]
98    fn encode() {
99        let mut buffer = [0u8; 2];
100        assert_eq!(&[0x05, 0x00], Null.encode_to_slice(&mut buffer).unwrap());
101        assert_eq!(&[0x05, 0x00], ().encode_to_slice(&mut buffer).unwrap());
102    }
103
104    #[test]
105    fn reject_non_canonical() {
106        assert!(Null::from_der(&[0x05, 0x81, 0x00]).is_err());
107    }
108}
der/asn1/null.rs

der/asn1/
null.rs
