ring/aead/overlapping/partial_block.rs
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// Copyright 2024 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 AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR 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.
use super::Overlapping;
use crate::error::InputTooLongError;
pub struct PartialBlock<'i, T, const BLOCK_LEN: usize> {
// invariant: `self.in_out.len() < BLOCK_LEN`.
in_out: Overlapping<'i, T>,
}
impl<'i, T, const BLOCK_LEN: usize> PartialBlock<'i, T, BLOCK_LEN> {
pub fn new(in_out: Overlapping<'i, T>) -> Result<Self, InputTooLongError> {
let len = in_out.len();
if len >= BLOCK_LEN {
return Err(InputTooLongError::new(len));
}
Ok(Self { in_out })
}
pub fn overwrite_at_start(self, padded: [T; BLOCK_LEN])
where
T: Copy,
{
let len = self.len();
let output = self.in_out.into_unwritten_output();
assert!(output.len() <= padded.len());
output.copy_from_slice(&padded[..len]);
}
}
impl<T, const BLOCK_LEN: usize> PartialBlock<'_, T, BLOCK_LEN> {
#[inline(always)]
pub fn input(&self) -> &[T] {
let r = self.in_out.input();
// Help the optimizer optimize the caller using the invariant.
// TODO: Does this actually help?
if r.len() >= BLOCK_LEN {
unreachable!()
}
r
}
#[inline(always)]
pub fn len(&self) -> usize {
self.input().len()
}
}