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block-buffer: improve split_blocks implementations #1220

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Merged
merged 1 commit into from
Sep 21, 2025
Merged

block-buffer: improve split_blocks implementations #1220

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37 changes: 7 additions & 30 deletions block-buffer/src/sealed.rs
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
use hybrid_array::sizes::{U0, U1};

use super::{Array, ArraySize};
use core::{mem::MaybeUninit, ptr, slice};
use core::{mem::MaybeUninit, ptr};

type Block<N> = MaybeUninit<Array<u8, N>>;

Expand Down Expand Up @@ -60,18 +60,7 @@ impl Sealed for super::Eager {

#[inline(always)]
fn split_blocks<N: ArraySize>(data: &[u8]) -> (&[Array<u8, N>], &[u8]) {
let nb = data.len() / N::USIZE;
let blocks_len = nb * N::USIZE;
let tail_len = data.len() - blocks_len;
// SAFETY: we guarantee that created slices do not point outside of `data`
unsafe {
let blocks_ptr = data.as_ptr() as *const Array<u8, N>;
let tail_ptr = data.as_ptr().add(blocks_len);
(
slice::from_raw_parts(blocks_ptr, nb),
slice::from_raw_parts(tail_ptr, tail_len),
)
}
Array::slice_as_chunks(data)
}
}

Expand All @@ -96,24 +85,12 @@ impl Sealed for super::Lazy {

#[inline(always)]
fn split_blocks<N: ArraySize>(data: &[u8]) -> (&[Array<u8, N>], &[u8]) {
if data.is_empty() {
return (&[], &[]);
}
let (nb, tail_len) = if data.len() % N::USIZE == 0 {
(data.len() / N::USIZE - 1, N::USIZE)
let (blocks, tail) = Array::slice_as_chunks(data);
if data.is_empty() || !tail.is_empty() {
(blocks, tail)
} else {
let nb = data.len() / N::USIZE;
(nb, data.len() - nb * N::USIZE)
};
let blocks_len = nb * N::USIZE;
// SAFETY: we guarantee that created slices do not point outside of `data`
unsafe {
let blocks_ptr = data.as_ptr() as *const Array<u8, N>;
let tail_ptr = data.as_ptr().add(blocks_len);
(
slice::from_raw_parts(blocks_ptr, nb),
slice::from_raw_parts(tail_ptr, tail_len),
)
let (tail, blocks) = blocks.split_last().expect("`blocks` can not be empty");
(blocks, tail)
}
}
}