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use crate::{Any, Encodable, Encoder, Error, ErrorKind, Length, Result, Tag, Tagged};
use core::convert::TryFrom;
#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
pub struct Null;
impl TryFrom<Any<'_>> for Null {
type Error = Error;
fn try_from(any: Any<'_>) -> Result<Null> {
let tag = any.tag().assert_eq(Tag::Null)?;
if any.is_empty() {
Ok(Null)
} else {
Err(ErrorKind::Length { tag }.into())
}
}
}
impl<'a> From<Null> for Any<'a> {
fn from(_: Null) -> Any<'a> {
Any::new(Tag::Null, &[]).unwrap()
}
}
impl Encodable for Null {
fn encoded_len(&self) -> Result<Length> {
Any::from(*self).encoded_len()
}
fn encode(&self, encoder: &mut Encoder<'_>) -> Result<()> {
Any::from(*self).encode(encoder)
}
}
impl Tagged for Null {
const TAG: Tag = Tag::Integer;
}
impl TryFrom<Any<'_>> for () {
type Error = Error;
fn try_from(any: Any<'_>) -> Result<()> {
let tag = any.tag().assert_eq(Tag::Null)?;
if any.is_empty() {
Ok(())
} else {
Err(ErrorKind::Length { tag }.into())
}
}
}
impl<'a> From<()> for Any<'a> {
fn from(_: ()) -> Any<'a> {
Any::new(Tag::Null, &[]).unwrap()
}
}
impl Encodable for () {
fn encoded_len(&self) -> Result<Length> {
Any::from(()).encoded_len()
}
fn encode(&self, encoder: &mut Encoder<'_>) -> Result<()> {
Any::from(()).encode(encoder)
}
}
impl Tagged for () {
const TAG: Tag = Tag::Null;
}
#[cfg(test)]
mod tests {
use super::Null;
use crate::{Decodable, Encodable};
#[test]
fn decode() {
assert!(Null::from_der(&[0x05, 0x00]).is_ok());
}
#[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());
}
}