der/asn1/
null.rs

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

der/asn1/
null.rs
