Dandandan commented on code in PR #9229:
URL: https://github.com/apache/arrow-rs/pull/9229#discussion_r2708247266
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parquet/src/arrow/buffer/bit_util.rs:
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@@ -36,14 +36,15 @@ pub fn iter_set_bits_rev(bytes: &[u8]) -> impl
Iterator<Item = usize> + '_ {
.chain(unaligned.chunks().iter().cloned())
.chain(unaligned.suffix());
- iter.rev().flat_map(move |mut chunk| {
+ iter.rev().flat_map(move |chunk| {
let chunk_idx = chunk_end_idx - 64;
chunk_end_idx = chunk_idx;
+ let mut rev_chunk = chunk.reverse_bits();
std::iter::from_fn(move || {
- if chunk != 0 {
- let bit_pos = 63 - chunk.leading_zeros();
- chunk ^= 1 << bit_pos;
- return Some(chunk_idx + (bit_pos as usize));
+ if rev_chunk != 0 {
+ let bit_pos = rev_chunk.trailing_zeros();
+ rev_chunk &= rev_chunk - 1;
Review Comment:
Applying the same optimization here
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