der 0.6.1

Pure Rust embedded-friendly implementation of the Distinguished Encoding Rules (DER) for Abstract Syntax Notation One (ASN.1) as described in ITU X.690 with full support for heapless no_std targets
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133

//! Trait definition for [`Encode`].

use crate::{Header, Length, Result, SliceWriter, Tagged, Writer};

#[cfg(feature = "alloc")]
use {alloc::vec::Vec, core::iter};

#[cfg(feature = "pem")]
use {
    crate::PemWriter,
    alloc::string::String,
    pem_rfc7468::{self as pem, LineEnding, PemLabel},
};

#[cfg(any(feature = "alloc", feature = "pem"))]
use crate::ErrorKind;

#[cfg(doc)]
use crate::Tag;

/// Encoding trait.
pub trait Encode {
    /// Compute the length of this value in bytes when encoded as ASN.1 DER.
    fn encoded_len(&self) -> Result<Length>;

    /// Encode this value as ASN.1 DER using the provided [`Writer`].
    fn encode(&self, encoder: &mut dyn Writer) -> Result<()>;

    /// Encode this value to the provided byte slice, returning a sub-slice
    /// containing the encoded message.
    fn encode_to_slice<'a>(&self, buf: &'a mut [u8]) -> Result<&'a [u8]> {
        let mut writer = SliceWriter::new(buf);
        self.encode(&mut writer)?;
        writer.finish()
    }

    /// Encode this message as ASN.1 DER, appending it to the provided
    /// byte vector.
    #[cfg(feature = "alloc")]
    #[cfg_attr(docsrs, doc(cfg(feature = "alloc")))]
    fn encode_to_vec(&self, buf: &mut Vec<u8>) -> Result<Length> {
        let expected_len = usize::try_from(self.encoded_len()?)?;
        buf.reserve(expected_len);
        buf.extend(iter::repeat(0).take(expected_len));

        let mut writer = SliceWriter::new(buf);
        self.encode(&mut writer)?;
        let actual_len = writer.finish()?.len();

        if expected_len != actual_len {
            return Err(ErrorKind::Incomplete {
                expected_len: expected_len.try_into()?,
                actual_len: actual_len.try_into()?,
            }
            .into());
        }

        actual_len.try_into()
    }

    /// Serialize this message as a byte vector.
    #[cfg(feature = "alloc")]
    #[cfg_attr(docsrs, doc(cfg(feature = "alloc")))]
    fn to_vec(&self) -> Result<Vec<u8>> {
        let mut buf = Vec::new();
        self.encode_to_vec(&mut buf)?;
        Ok(buf)
    }
}

impl<T> Encode for T
where
    T: EncodeValue + Tagged,
{
    /// Compute the length of this value in bytes when encoded as ASN.1 DER.
    fn encoded_len(&self) -> Result<Length> {
        self.value_len().and_then(|len| len.for_tlv())
    }

    /// Encode this value as ASN.1 DER using the provided [`Writer`].
    fn encode(&self, writer: &mut dyn Writer) -> Result<()> {
        self.header()?.encode(writer)?;
        self.encode_value(writer)
    }
}

/// PEM encoding trait.
///
/// This trait is automatically impl'd for any type which impls both
/// [`Encode`] and [`PemLabel`].
#[cfg(feature = "pem")]
#[cfg_attr(docsrs, doc(cfg(feature = "pem")))]
pub trait EncodePem: Encode + PemLabel {
    /// Try to encode this type as PEM.
    fn to_pem(&self, line_ending: LineEnding) -> Result<String>;
}

#[cfg(feature = "pem")]
#[cfg_attr(docsrs, doc(cfg(feature = "pem")))]
impl<T: Encode + PemLabel> EncodePem for T {
    fn to_pem(&self, line_ending: LineEnding) -> Result<String> {
        let der_len = usize::try_from(self.encoded_len()?)?;
        let pem_len = pem::encapsulated_len(Self::PEM_LABEL, line_ending, der_len)?;

        let mut buf = vec![0u8; pem_len];
        let mut writer = PemWriter::new(Self::PEM_LABEL, line_ending, &mut buf)?;
        self.encode(&mut writer)?;

        let actual_len = writer.finish()?;
        buf.truncate(actual_len);
        Ok(String::from_utf8(buf)?)
    }
}

/// Encode the value part of a Tag-Length-Value encoded field, sans the [`Tag`]
/// and [`Length`].
pub trait EncodeValue {
    /// Get the [`Header`] used to encode this value.
    fn header(&self) -> Result<Header>
    where
        Self: Tagged,
    {
        Header::new(self.tag(), self.value_len()?)
    }

    /// Compute the length of this value (sans [`Tag`]+[`Length`] header) when
    /// encoded as ASN.1 DER.
    fn value_len(&self) -> Result<Length>;

    /// Encode value (sans [`Tag`]+[`Length`] header) as ASN.1 DER using the
    /// provided [`Writer`].
    fn encode_value(&self, encoder: &mut dyn Writer) -> Result<()>;
}