blob: a9fe4389042ddd04e8d9c36f1315fe20237cac2e (
plain)
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
|
//! Support for encoding negative integers
use super::is_highest_bit_set;
use crate::{ErrorKind, Length, Result, Writer};
/// Decode an unsigned integer of the specified size.
///
/// Returns a byte array of the requested size containing a big endian integer.
pub(super) fn decode_to_array<const N: usize>(bytes: &[u8]) -> Result<[u8; N]> {
match N.checked_sub(bytes.len()) {
Some(offset) => {
let mut output = [0xFFu8; N];
output[offset..].copy_from_slice(bytes);
Ok(output)
}
None => {
let expected_len = Length::try_from(N)?;
let actual_len = Length::try_from(bytes.len())?;
Err(ErrorKind::Incomplete {
expected_len,
actual_len,
}
.into())
}
}
}
/// Encode the given big endian bytes representing an integer as ASN.1 DER.
pub(super) fn encode_bytes<W>(writer: &mut W, bytes: &[u8]) -> Result<()>
where
W: Writer + ?Sized,
{
writer.write(strip_leading_ones(bytes))
}
/// Get the encoded length for the given unsigned integer serialized as bytes.
#[inline]
pub(super) fn encoded_len(bytes: &[u8]) -> Result<Length> {
Length::try_from(strip_leading_ones(bytes).len())
}
/// Strip the leading all-ones bytes from the given byte slice.
fn strip_leading_ones(mut bytes: &[u8]) -> &[u8] {
while let Some((byte, rest)) = bytes.split_first() {
if *byte == 0xFF && is_highest_bit_set(rest) {
bytes = rest;
continue;
}
break;
}
bytes
}
|
