Trait asn1_rs::FromDer

pub trait FromDer<'a, E = Error>: Sized {
    fn from_der(bytes: &'a [u8]) -> ParseResult<'_, Self, E>;
}

Base trait for DER object parsers

Library authors should usually not directly implement this trait, but should prefer implementing the TryFrom<Any> + CheckDerConstraints traits, which offers greater flexibility and provides an equivalent FromDer implementation for free (in fact, it provides both FromBer and FromDer).

Note: if you already implemented TryFrom<Any> and CheckDerConstraints, you can get a free FromDer implementation by implementing the DerAutoDerive trait. This is not automatic, so it is also possible to manually implement FromDer if preferred.

Examples

use asn1_rs::{Any, CheckDerConstraints, DerAutoDerive, Result, Tag};
use std::convert::TryFrom;

// The type to be decoded
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct MyType(pub u32);

impl<'a> TryFrom<Any<'a>> for MyType {
    type Error = asn1_rs::Error;

    fn try_from(any: Any<'a>) -> Result<MyType> {
        any.tag().assert_eq(Tag::Integer)?;
        // for this fictive example, the type contains the number of characters
        let n = any.data.len() as u32;
        Ok(MyType(n))
    }
}

impl CheckDerConstraints for MyType {
    fn check_constraints(any: &Any) -> Result<()> {
        any.header.assert_primitive()?;
        Ok(())
    }
}

impl DerAutoDerive for MyType {}

// The above code provides a `FromDer` implementation for free.

// Example of parsing code:
use asn1_rs::FromDer;

let input = &[2, 1, 2];
// Objects can be parsed using `from_der`, which returns the remaining bytes
// and the parsed object:
let (rem, my_type) = MyType::from_der(input).expect("parsing failed");

Required Methods

fn from_der(bytes: &'a [u8]) -> ParseResult<'_, Self, E>

Attempt to parse input bytes into a DER object (enforcing constraints)

Implementations on Foreign Types

impl<'a, T> FromDer<'a, Error> for Option<T> where
    T: FromDer<'a>, 

fn from_der(bytes: &'a [u8]) -> ParseResult<'_, Self>

impl<'a, T, E> FromDer<'a, E> for Vec<T> where
    T: FromDer<'a, E>,
    E: From<Error>, 

manual impl of FromDer, so we do not need to require TryFrom + CheckDerConstraints

fn from_der(bytes: &'a [u8]) -> ParseResult<'_, Self, E>

impl<'a, T, E> FromDer<'a, E> for BTreeSet<T> where
    T: FromDer<'a, E>,
    T: Ord,
    E: From<Error>, 

manual impl of FromDer, so we do not need to require TryFrom + CheckDerConstraints

fn from_der(bytes: &'a [u8]) -> ParseResult<'a, Self, E>

impl<'a, T, E> FromDer<'a, E> for HashSet<T> where
    T: FromDer<'a, E>,
    T: Hash + Eq,
    E: From<Error>, 

manual impl of FromDer, so we do not need to require TryFrom + CheckDerConstraints

fn from_der(bytes: &'a [u8]) -> ParseResult<'a, Self, E>

Implementors

impl<'a> FromDer<'a, Error> for Any<'a>

impl<'a> FromDer<'a, Error> for Header<'a>

impl<'a, T, E> FromDer<'a, E> for TaggedParser<'a, Explicit, T, E> where
    T: FromDer<'a, E>,
    E: From<Error>, 

impl<'a, T, E> FromDer<'a, E> for TaggedParser<'a, Implicit, T, E> where
    T: TryFrom<Any<'a>, Error = E>,
    T: CheckDerConstraints,
    T: Tagged,
    E: From<Error>, 

impl<'a, T, E> FromDer<'a, E> for T where
    T: TryFrom<Any<'a>, Error = E>,
    T: CheckDerConstraints,
    T: DerAutoDerive,
    E: From<Error>, 

impl<'a, T, E, const CLASS: u8, const TAG: u32> FromDer<'a, E> for TaggedValue<T, E, Explicit, CLASS, TAG> where
    T: FromDer<'a, E>,
    E: From<Error>, 

impl<'a, T, E, const CLASS: u8, const TAG: u32> FromDer<'a, E> for TaggedValue<T, E, Implicit, CLASS, TAG> where
    T: TryFrom<Any<'a>, Error = E>,
    T: Tagged,
    E: From<Error>,