ring/io/positive.rs
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// Copyright 2018 Brian Smith.
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
//! Serialization and deserialization.
use crate::error;
/// A serialized positive integer.
#[derive(Copy, Clone)]
pub struct Positive<'a>(untrusted::Input<'a>);
impl<'a> Positive<'a> {
#[inline]
pub(crate) fn from_be_bytes(input: untrusted::Input<'a>) -> Result<Self, error::Unspecified> {
// Empty inputs are not allowed.
let &first_byte = input
.as_slice_less_safe()
.first()
.ok_or(error::Unspecified)?;
// Zero isn't allowed and leading zeros aren't allowed.
if first_byte == 0 {
return Err(error::Unspecified);
}
Ok(Self(input))
}
/// Returns the value, ordered from significant byte to least significant
/// byte, without any leading zeros. The result is guaranteed to be
/// non-empty.
#[inline]
pub fn big_endian_without_leading_zero(&self) -> &'a [u8] {
self.big_endian_without_leading_zero_as_input()
.as_slice_less_safe()
}
#[inline]
pub(crate) fn big_endian_without_leading_zero_as_input(&self) -> untrusted::Input<'a> {
self.0
}
}
impl Positive<'_> {
/// Returns the first byte.
///
/// Will not panic because the value is guaranteed to have at least one
/// byte.
pub fn first_byte(&self) -> u8 {
// This won't panic because
self.0.as_slice_less_safe()[0]
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_from_be_bytes() {
static TEST_CASES: &[(&[u8], Result<&[u8], error::Unspecified>)] = &[
// An empty input isn't a number.
(&[], Err(error::Unspecified)),
// Zero is not positive.
(&[0x00], Err(error::Unspecified)),
// Minimum value. No leading zero required or allowed.
(&[0x00, 0x01], Err(error::Unspecified)),
(&[0x01], Ok(&[0x01])),
// Maximum first byte. No leading zero required or allowed.
(&[0xff], Ok(&[0xff])),
(&[0x00, 0xff], Err(error::Unspecified)),
// The last byte can be zero.
(&[0x01, 0x00], Ok(&[0x01, 0x00])),
(&[0x01, 0x00, 0x00], Ok(&[0x01, 0x00, 0x00])),
// Having no zero bytes are also allowed.
(&[0x01, 0x01], Ok(&[0x01, 0x01])),
// A middle byte can be zero.
(&[0x01, 0x00, 0x01], Ok(&[0x01, 0x00, 0x01])),
(&[0x01, 0x01, 0x01], Ok(&[0x01, 0x01, 0x01])),
];
for &(input, result) in TEST_CASES {
let input = untrusted::Input::from(input);
assert_eq!(
Positive::from_be_bytes(input).map(|p| p.big_endian_without_leading_zero()),
result
);
}
}
}