der/tag/
class.rs

1//! Class of an ASN.1 tag.
2
3use super::{TagNumber, CONSTRUCTED_FLAG};
4use core::fmt;
5
6/// Class of an ASN.1 tag.
7#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
8#[repr(u8)]
9pub enum Class {
10    /// `UNIVERSAL`: built-in types whose meaning is the same in all
11    /// applications.
12    Universal = 0b00000000,
13
14    /// `APPLICATION`: types whose meaning is specific to an application,
15    ///
16    /// Types in two different applications may have the same
17    /// application-specific tag and different meanings.
18    Application = 0b01000000,
19
20    /// `CONTEXT-SPECIFIC`: types whose meaning is specific to a given
21    /// structured type.
22    ///
23    /// Context-specific tags are used to distinguish between component types
24    /// with the same underlying tag within the context of a given structured
25    /// type, and component types in two different structured types may have
26    /// the same tag and different meanings.
27    ContextSpecific = 0b10000000,
28
29    /// `PRIVATE`: types whose meaning is specific to a given enterprise.
30    Private = 0b11000000,
31}
32
33impl Class {
34    /// Compute the identifier octet for a tag number of this class.
35    pub(super) fn octet(self, constructed: bool, number: TagNumber) -> u8 {
36        self as u8 | number.value() | (constructed as u8 * CONSTRUCTED_FLAG)
37    }
38}
39
40impl fmt::Display for Class {
41    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
42        f.write_str(match self {
43            Class::Universal => "UNIVERSAL",
44            Class::Application => "APPLICATION",
45            Class::ContextSpecific => "CONTEXT-SPECIFIC",
46            Class::Private => "PRIVATE",
47        })
48    }
49}