alamb commented on code in PR #7962:
URL: https://github.com/apache/arrow-rs/pull/7962#discussion_r2228777149
##########
arrow-buffer/src/util/bit_iterator.rs:
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@@ -231,6 +231,63 @@ impl Iterator for BitIndexIterator<'_> {
}
}
+/// An iterator of u32 whose index in a provided bitmask is true
+/// Respects arbitrary offsets and slice lead/trail padding exactly like
BitIndexIterator
+#[derive(Debug)]
+pub struct BitIndexU32Iterator<'a> {
+ curr: u64,
+ chunk_offset: i64,
+ iter: UnalignedBitChunkIterator<'a>,
+}
+
+impl<'a> BitIndexU32Iterator<'a> {
+ /// Create a new [BitIndexU32Iterator] from the provided buffer,
+ /// offset and len in bits.
+ pub fn new(buffer: &'a [u8], offset: usize, len: usize) -> Self {
+ // Build the aligned chunks (including prefix/suffix masked)
+ let chunks = UnalignedBitChunk::new(buffer, offset, len);
+ let mut iter = chunks.iter();
+
+ // First 64-bit word (masked for lead padding), or 0 if empty
+ let curr = iter.next().unwrap_or(0);
+ // Negative lead padding ensures the first bit in curr maps to index 0
+ let chunk_offset = -(chunks.lead_padding() as i64);
+
+ Self {
+ curr,
+ chunk_offset,
+ iter,
+ }
+ }
+}
+
+impl<'a> Iterator for BitIndexU32Iterator<'a> {
Review Comment:
Conclusion from https://github.com/apache/arrow-rs/pull/7979 is that the u32
specific iterator is worth a 3-5% improvement:
https://github.com/apache/arrow-rs/pull/7979#issuecomment-3109047271
Given that I think this PR makes sense to me
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