ring/io/
der_writer.rs

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1// Copyright 2018 Brian Smith.
2//
3// Permission to use, copy, modify, and/or distribute this software for any
4// purpose with or without fee is hereby granted, provided that the above
5// copyright notice and this permission notice appear in all copies.
6//
7// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
8// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
10// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
14
15use super::{der::*, writer::*, *};
16use alloc::boxed::Box;
17
18pub(crate) fn write_positive_integer(
19    output: &mut dyn Accumulator,
20    value: &Positive,
21) -> Result<(), TooLongError> {
22    let first_byte = value.first_byte();
23    let value = value.big_endian_without_leading_zero_as_input();
24    write_tlv(output, Tag::Integer, |output| {
25        if (first_byte & 0x80) != 0 {
26            output.write_byte(0)?; // Disambiguate negative number.
27        }
28        write_copy(output, value)
29    })
30}
31
32pub(crate) fn write_all(
33    tag: Tag,
34    write_value: &dyn Fn(&mut dyn Accumulator) -> Result<(), TooLongError>,
35) -> Result<Box<[u8]>, TooLongError> {
36    let length = {
37        let mut length = LengthMeasurement::zero();
38        write_tlv(&mut length, tag, write_value)?;
39        length
40    };
41
42    let mut output = Writer::with_capacity(length);
43    write_tlv(&mut output, tag, write_value)?;
44
45    Ok(output.into())
46}
47
48fn write_tlv<F>(output: &mut dyn Accumulator, tag: Tag, write_value: F) -> Result<(), TooLongError>
49where
50    F: Fn(&mut dyn Accumulator) -> Result<(), TooLongError>,
51{
52    let length: usize = {
53        let mut length = LengthMeasurement::zero();
54        write_value(&mut length)?;
55        length.into()
56    };
57    let length: u16 = length.try_into().map_err(|_| TooLongError::new())?;
58
59    output.write_byte(tag.into())?;
60
61    let [lo, hi] = length.to_le_bytes();
62    if length >= 0x1_00 {
63        output.write_byte(0x82)?;
64        output.write_byte(hi)?;
65    } else if length >= 0x80 {
66        output.write_byte(0x81)?;
67    }
68    output.write_byte(lo)?;
69
70    write_value(output)
71}
ring/io/der_writer.rs

ring/io/
der_writer.rs
