der/
encode.rs

1//! Trait definition for [`Encode`].
2
3use crate::{Header, Length, Result, SliceWriter, Tagged, Writer};
4use core::marker::PhantomData;
5
6#[cfg(feature = "alloc")]
7use {alloc::boxed::Box, alloc::vec::Vec};
8
9#[cfg(feature = "pem")]
10use {
11    crate::PemWriter,
12    alloc::string::String,
13    pem_rfc7468::{self as pem, LineEnding, PemLabel},
14};
15
16#[cfg(any(feature = "alloc", feature = "pem"))]
17use crate::ErrorKind;
18
19#[cfg(doc)]
20use crate::Tag;
21
22/// Encoding trait.
23pub trait Encode {
24    /// Compute the length of this value in bytes when encoded as ASN.1 DER.
25    fn encoded_len(&self) -> Result<Length>;
26
27    /// Encode this value as ASN.1 DER using the provided [`Writer`].
28    fn encode(&self, encoder: &mut impl Writer) -> Result<()>;
29
30    /// Encode this value to the provided byte slice, returning a sub-slice
31    /// containing the encoded message.
32    fn encode_to_slice<'a>(&self, buf: &'a mut [u8]) -> Result<&'a [u8]> {
33        let mut writer = SliceWriter::new(buf);
34        self.encode(&mut writer)?;
35        writer.finish()
36    }
37
38    /// Encode this message as ASN.1 DER, appending it to the provided
39    /// byte vector.
40    #[cfg(feature = "alloc")]
41    fn encode_to_vec(&self, buf: &mut Vec<u8>) -> Result<Length> {
42        let expected_len = usize::try_from(self.encoded_len()?)?;
43        let initial_len = buf.len();
44        buf.resize(initial_len + expected_len, 0u8);
45
46        let buf_slice = &mut buf[initial_len..];
47        let actual_len = self.encode_to_slice(buf_slice)?.len();
48
49        if expected_len != actual_len {
50            return Err(ErrorKind::Incomplete {
51                expected_len: expected_len.try_into()?,
52                actual_len: actual_len.try_into()?,
53            }
54            .into());
55        }
56
57        actual_len.try_into()
58    }
59
60    /// Encode this type as DER, returning a byte vector.
61    #[cfg(feature = "alloc")]
62    fn to_der(&self) -> Result<Vec<u8>> {
63        let mut buf = Vec::new();
64        self.encode_to_vec(&mut buf)?;
65        Ok(buf)
66    }
67}
68
69impl<T> Encode for T
70where
71    T: EncodeValue + Tagged,
72{
73    /// Compute the length of this value in bytes when encoded as ASN.1 DER.
74    fn encoded_len(&self) -> Result<Length> {
75        self.value_len().and_then(|len| len.for_tlv())
76    }
77
78    /// Encode this value as ASN.1 DER using the provided [`Writer`].
79    fn encode(&self, writer: &mut impl Writer) -> Result<()> {
80        self.header()?.encode(writer)?;
81        self.encode_value(writer)
82    }
83}
84
85/// Dummy implementation for [`PhantomData`] which allows deriving
86/// implementations on structs with phantom fields.
87impl<T> Encode for PhantomData<T>
88where
89    T: ?Sized,
90{
91    fn encoded_len(&self) -> Result<Length> {
92        Ok(Length::ZERO)
93    }
94
95    fn encode(&self, _writer: &mut impl Writer) -> Result<()> {
96        Ok(())
97    }
98}
99
100/// PEM encoding trait.
101///
102/// This trait is automatically impl'd for any type which impls both
103/// [`Encode`] and [`PemLabel`].
104#[cfg(feature = "pem")]
105pub trait EncodePem: Encode + PemLabel {
106    /// Try to encode this type as PEM.
107    fn to_pem(&self, line_ending: LineEnding) -> Result<String>;
108}
109
110#[cfg(feature = "pem")]
111impl<T: Encode + PemLabel> EncodePem for T {
112    fn to_pem(&self, line_ending: LineEnding) -> Result<String> {
113        let der_len = usize::try_from(self.encoded_len()?)?;
114        let pem_len = pem::encapsulated_len(Self::PEM_LABEL, line_ending, der_len)?;
115
116        let mut buf = vec![0u8; pem_len];
117        let mut writer = PemWriter::new(Self::PEM_LABEL, line_ending, &mut buf)?;
118        self.encode(&mut writer)?;
119
120        let actual_len = writer.finish()?;
121        buf.truncate(actual_len);
122        Ok(String::from_utf8(buf)?)
123    }
124}
125
126/// Encode the value part of a Tag-Length-Value encoded field, sans the [`Tag`]
127/// and [`Length`].
128pub trait EncodeValue {
129    /// Get the [`Header`] used to encode this value.
130    fn header(&self) -> Result<Header>
131    where
132        Self: Tagged,
133    {
134        Header::new(self.tag(), self.value_len()?)
135    }
136
137    /// Compute the length of this value (sans [`Tag`]+[`Length`] header) when
138    /// encoded as ASN.1 DER.
139    fn value_len(&self) -> Result<Length>;
140
141    /// Encode value (sans [`Tag`]+[`Length`] header) as ASN.1 DER using the
142    /// provided [`Writer`].
143    fn encode_value(&self, encoder: &mut impl Writer) -> Result<()>;
144}
145
146#[cfg(feature = "alloc")]
147impl<T> EncodeValue for Box<T>
148where
149    T: EncodeValue,
150{
151    fn value_len(&self) -> Result<Length> {
152        T::value_len(self)
153    }
154    fn encode_value(&self, writer: &mut impl Writer) -> Result<()> {
155        T::encode_value(self, writer)
156    }
157}
der/encode.rs

der/
encode.rs
