der/asn1/
null.rs

1//! ASN.1 `NULL` support.
2
3use crate::{
4    asn1::AnyRef, ord::OrdIsValueOrd, ByteSlice, 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<'a> DecodeValue<'a> for Null {
13    fn decode_value<R: Reader<'a>>(reader: &mut R, header: Header) -> Result<Self> {
14        if header.length.is_zero() {
15            Ok(Null)
16        } else {
17            Err(reader.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, _writer: &mut dyn Writer) -> 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 AnyRef<'a> {
39    fn from(_: Null) -> AnyRef<'a> {
40        AnyRef::from_tag_and_value(Tag::Null, ByteSlice::default())
41    }
42}
43
44impl TryFrom<AnyRef<'_>> for Null {
45    type Error = Error;
46
47    fn try_from(any: AnyRef<'_>) -> Result<Null> {
48        any.decode_into()
49    }
50}
51
52impl TryFrom<AnyRef<'_>> for () {
53    type Error = Error;
54
55    fn try_from(any: AnyRef<'_>) -> Result<()> {
56        Null::try_from(any).map(|_| ())
57    }
58}
59
60impl<'a> From<()> for AnyRef<'a> {
61    fn from(_: ()) -> AnyRef<'a> {
62        Null.into()
63    }
64}
65
66impl<'a> DecodeValue<'a> for () {
67    fn decode_value<R: Reader<'a>>(reader: &mut R, header: Header) -> Result<Self> {
68        Null::decode_value(reader, header)?;
69        Ok(())
70    }
71}
72
73impl EncodeValue for () {
74    fn value_len(&self) -> Result<Length> {
75        Ok(Length::ZERO)
76    }
77
78    fn encode_value(&self, _writer: &mut dyn Writer) -> Result<()> {
79        Ok(())
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::{Decode, Encode};
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
