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use crate::{
asn1::Any, ByteSlice, DecodeValue, Decoder, Encodable, EncodeValue, Encoder, Error, ErrorKind,
FixedTag, Length, OrdIsValueOrd, Result, Tag,
};
#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
pub struct Null;
impl DecodeValue<'_> for Null {
fn decode_value(decoder: &mut Decoder<'_>, length: Length) -> Result<Self> {
if length.is_zero() {
Ok(Null)
} else {
Err(decoder.error(ErrorKind::Length { tag: Self::TAG }))
}
}
}
impl EncodeValue for Null {
fn value_len(&self) -> Result<Length> {
Ok(Length::ZERO)
}
fn encode_value(&self, _encoder: &mut Encoder<'_>) -> Result<()> {
Ok(())
}
}
impl FixedTag for Null {
const TAG: Tag = Tag::Null;
}
impl OrdIsValueOrd for Null {}
impl<'a> From<Null> for Any<'a> {
fn from(_: Null) -> Any<'a> {
Any::from_tag_and_value(Tag::Null, ByteSlice::default())
}
}
impl TryFrom<Any<'_>> for Null {
type Error = Error;
fn try_from(any: Any<'_>) -> Result<Null> {
any.decode_into()
}
}
impl TryFrom<Any<'_>> for () {
type Error = Error;
fn try_from(any: Any<'_>) -> Result<()> {
Null::try_from(any).map(|_| ())
}
}
impl<'a> From<()> for Any<'a> {
fn from(_: ()) -> Any<'a> {
Null.into()
}
}
impl DecodeValue<'_> for () {
fn decode_value(decoder: &mut Decoder<'_>, length: Length) -> Result<Self> {
Null::decode_value(decoder, length)?;
Ok(())
}
}
impl Encodable for () {
fn encoded_len(&self) -> Result<Length> {
Null.encoded_len()
}
fn encode(&self, encoder: &mut Encoder<'_>) -> Result<()> {
Null.encode(encoder)
}
}
impl FixedTag for () {
const TAG: Tag = Tag::Null;
}
#[cfg(test)]
mod tests {
use super::Null;
use crate::{Decodable, Encodable};
#[test]
fn decode() {
Null::from_der(&[0x05, 0x00]).unwrap();
}
#[test]
fn encode() {
let mut buffer = [0u8; 2];
assert_eq!(&[0x05, 0x00], Null.encode_to_slice(&mut buffer).unwrap());
assert_eq!(&[0x05, 0x00], ().encode_to_slice(&mut buffer).unwrap());
}
#[test]
fn reject_non_canonical() {
assert!(Null::from_der(&[0x05, 0x81, 0x00]).is_err());
}
}
