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`?
can_decode(tag: Tag) -> bool14     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 {
can_decode(tag: Tag) -> bool23     fn can_decode(tag: Tag) -> bool {
24         T::TAG == tag
25     }
26 }
27