1// Copyright 2024 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 AUTHORS DISCLAIM ALL WARRANTIES
8// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS 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::Overlapping;
16use crate::error::InputTooLongError;
17
18pub struct PartialBlock<'i, T, const BLOCK_LEN: usize> {
19 // invariant: `self.in_out.len() < BLOCK_LEN`.
20 in_out: Overlapping<'i, T>,
21}
22
23impl<'i, T, const BLOCK_LEN: usize> PartialBlock<'i, T, BLOCK_LEN> {
24 pub fn new(in_out: Overlapping<'i, T>) -> Result<Self, InputTooLongError> {
25 let len: usize = in_out.len();
26 if len >= BLOCK_LEN {
27 return Err(InputTooLongError::new(imprecise_input_length:len));
28 }
29 Ok(Self { in_out })
30 }
31
32 pub fn overwrite_at_start(self, padded: [T; BLOCK_LEN])
33 where
34 T: Copy,
35 {
36 let len: usize = self.len();
37 let output: &mut [T] = self.in_out.into_unwritten_output();
38 assert!(output.len() <= padded.len());
39 output.copy_from_slice(&padded[..len]);
40 }
41}
42
43impl<T, const BLOCK_LEN: usize> PartialBlock<'_, T, BLOCK_LEN> {
44 #[inline(always)]
45 pub fn input(&self) -> &[T] {
46 let r: &[T] = self.in_out.input();
47 // Help the optimizer optimize the caller using the invariant.
48 // TODO: Does this actually help?
49 if r.len() >= BLOCK_LEN {
50 unreachable!()
51 }
52 r
53 }
54
55 #[inline(always)]
56 pub fn len(&self) -> usize {
57 self.input().len()
58 }
59}
60