bcder/
mode.rs

1//! The BER mode.
2//!
3//! This is a private module. It’s public items are re-exported by the parent.
4
5use crate::decode;
6use crate::decode::DecodeError;
7
8
9//------------ Mode ----------------------------------------------------------
10
11/// The BER Mode.
12///
13/// X.680 defines not one but three sets of related encoding rules. All three
14/// follow the same basic ideas but implement them in slightly different
15/// ways.
16///
17/// This type represents these rules. The [`decode`] method provides a way to
18/// decode a source using the specific decoding mode. You can also change
19/// the decoding mode later on through the `set_mode` methods of [`Primitive`]
20/// and [`Constructed`].
21///
22/// [`decode´]: #method.decode
23/// [`Primitive`]: decode/struct.Primitive.html
24/// [`Constructed`]: decode/struct.Constructed.html
25#[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
26pub enum Mode {
27    /// Basic Encoding Rules.
28    ///
29    /// These are the most flexible rules, allowing alternative encodings for
30    /// some types as well as indefinite length values.
31    #[default]
32    Ber,
33
34    /// Canonical Encoding Rules.
35    ///
36    /// These rules always employ indefinite length encoding for constructed
37    /// values and the shortest possible form for primitive values.  There
38    /// are additional restrictions for certain types.
39    Cer,
40
41    /// Distinguished Encoding Rules.
42    ///
43    /// These rules always employ definite length values and require the
44    /// shortest possible encoding. Additional rules apply to some types.
45    Der,
46}
47
48impl Mode {
49    /// Decode a source using a specific mode.
50    ///
51    /// The method will attempt to decode `source` using the rules represented
52    /// by this value. The closure `op` will be given the content of the
53    /// source as a sequence of values. The closure does not need to process
54    /// all values in the source.
55    pub fn decode<S, F, T>(
56        self, source: S, op: F,
57    ) -> Result<T, DecodeError<<S::Source as decode::Source>::Error>>
58    where
59        S: decode::IntoSource,
60        F: FnOnce(
61            &mut decode::Constructed<S::Source>
62        ) -> Result<T, DecodeError<<S::Source as decode::Source>::Error>>,
63    {
64        decode::Constructed::decode(source, self, op)
65    }
66
67    /// Returns whether the mode is `Mode::Ber`.
68    pub fn is_ber(self) -> bool {
69        matches!(self, Mode::Ber)
70    }
71
72    /// Returns whether the mode is `Mode::Cer`.
73    pub fn is_cer(self) -> bool {
74        matches!(self, Mode::Cer)
75    }
76
77    /// Returns whether the mode is `Mode::Der`.
78    pub fn is_der(self) -> bool {
79        matches!(self, Mode::Der)
80    }
81}
82
bcder/mode.rs

bcder/
mode.rs
