vendor/der/src/asn1/choice.rs

   1 //! ASN.1 `CHOICE` support.
   2
   3 use crate::{Decode, FixedTag, Tag, Tagged};
   4
   5 /// ASN.1 `CHOICE` denotes a union of one or more possible alternatives.
   6 ///
   7 /// The types MUST have distinct tags.
   8 ///
   9 /// This crate models choice as a trait, with a blanket impl for all types
  10 /// which impl `Decode + FixedTag` (i.e. they are modeled as a `CHOICE`
  11 /// with only one possible variant)
  12 pub trait Choice<'a>: Decode<'a> + Tagged {
  13     /// Is the provided [`Tag`] decodable as a variant of this `CHOICE`?
  14     fn can_decode(tag: Tag) -> bool;
  15 }
  16
  17 /// This blanket impl allows any [`Tagged`] type to function as a [`Choice`]
  18 /// with a single alternative.
  19 impl<'a, T> Choice<'a> for T
  20 where
  21     T: Decode<'a> + FixedTag,
  22 {
  23     fn can_decode(tag: Tag) -> bool {
  24         T::TAG == tag
  25     }
  26 }