alamb commented on code in PR #9229:
URL: https://github.com/apache/arrow-rs/pull/9229#discussion_r2708452569
##########
arrow-select/src/filter.rs:
##########
@@ -91,6 +91,24 @@ impl<'a> IndexIterator<'a> {
let iter = filter.values().set_indices();
Self { remaining, iter }
}
+
+ /// Collect this iterator as a [`Vec`]
+ pub fn collect(mut self) -> Vec<usize> {
+ let len = self.remaining;
+ let mut result = Vec::with_capacity(len);
+ let ptr: *mut usize = result.as_mut_ptr();
+ for i in 0..len {
+ // SAFETY: we have allocated enough space in `result`
Review Comment:
I think it also relies on self.iter.next() being correctly synchronized with
self.remaining.
Maybe we can add a debug assert to validate that assertion ?
##########
arrow-buffer/src/util/bit_iterator.rs:
##########
@@ -305,12 +305,12 @@ impl<'a> BitIndexIterator<'a> {
impl Iterator for BitIndexIterator<'_> {
type Item = usize;
- #[inline]
+ #[inline(always)]
fn next(&mut self) -> Option<Self::Item> {
loop {
if self.current_chunk != 0 {
let bit_pos = self.current_chunk.trailing_zeros();
- self.current_chunk ^= 1 << bit_pos;
+ self.current_chunk &= self.current_chunk - 1;
Review Comment:
fascinating
##########
arrow-select/src/filter.rs:
##########
@@ -91,6 +91,24 @@ impl<'a> IndexIterator<'a> {
let iter = filter.values().set_indices();
Self { remaining, iter }
}
+
+ /// Collect this iterator as a [`Vec`]
+ pub fn collect(mut self) -> Vec<usize> {
Review Comment:
Maybe it is worth a comment explaining that we can avoid this code when
TrustedLengh is stable
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