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Remove bounds checks from extend_from_within_overlapping #186

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Shnatsel wants to merge 3 commits into from
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Remove bounds checks from extend_from_within_overlapping #186

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4be27bc
Remove bounds checks from the safe version of extend_from_within_over…
Shnatsel Jun 16, 2025
dd23da8
Use a different formulation for 1 more slice check but shorter assembly
Shnatsel Jun 16, 2025
777ec72
replace std with core
Shnatsel Jun 21, 2025
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8 changes: 6 additions & 2 deletions src/sink.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -189,9 +189,13 @@ impl Sink for SliceSink<'_> {
#[cfg(feature = "safe-decode")]
#[cfg_attr(feature = "nightly", optimize(size))] // to avoid loop unrolling
fn extend_from_within_overlapping(&mut self, start: usize, num_bytes: usize) {
use core::cell::Cell;
let offset = self.pos - start;
for i in start + offset..start + offset + num_bytes {
self.output[i] = self.output[i - offset];
let slice_of_cells: &[Cell<u8>] = Cell::from_mut(self.output).as_slice_of_cells();
let input = &slice_of_cells[start..];
let output = &input[offset..][..num_bytes];
for (in_byte, out_byte) in input.iter().zip(output.iter()) {
out_byte.set(in_byte.get());
}
self.pos += num_bytes;
}
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