Trait FromDer

pub trait FromDer<'a, E = Error>: Sized {
    // Required method
    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)

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl<'a, T> FromDer<'a> for Option<T>

where T: FromDer<'a>,

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

impl<'a, T, E> FromDer<'a, E> for BTreeSet<T>

where T: FromDer<'a, E> + Ord, E: From<Error>,

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

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

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<Any> + CheckDerConstraints

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

impl<'a, T, E> FromDer<'a, E> for HashSet<T>

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

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

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

Implementors

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

impl<'a> FromDer<'a> 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> + CheckDerConstraints + Tagged, E: From<Error>,

impl<'a, T, E> FromDer<'a, E> for T

where T: TryFrom<Any<'a>, Error = E> + CheckDerConstraints + 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> + Tagged, E: From<Error>,