tustvold commented on a change in pull request #1228:
URL: https://github.com/apache/arrow-rs/pull/1228#discussion_r796687039
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File path: arrow/src/util/bit_chunk_iterator.rs
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@@ -272,4 +462,149 @@ mod tests {
assert_eq!(u64::MAX, bitchunks.iter().last().unwrap());
assert_eq!(0x7F, bitchunks.remainder_bits());
}
+
+ #[test]
+ #[allow(clippy::assertions_on_constants)]
+ fn test_unaligned_bit_chunk_iterator() {
+ // This test exploits the fact Buffer is at least 64-byte aligned
+ assert!(ALIGNMENT > 64);
+
+ let buffer = Buffer::from(&[0xFF; 5]);
+ let unaligned = UnalignedBitChunk::new(buffer.as_slice(), 0, 40);
+
+ assert_eq!(unaligned.prefix(), Some((1 << 40) - 1));
+ assert_eq!(unaligned.suffix(), None);
+ assert!(unaligned.chunks().is_empty());
+ assert_eq!(unaligned.lead_padding(), 0);
+ assert_eq!(unaligned.trailing_padding(), 24);
+
+ let buffer = buffer.slice(1);
+ let unaligned = UnalignedBitChunk::new(buffer.as_slice(), 0, 32);
+
+ assert_eq!(unaligned.prefix(), Some((1 << 32) - 1));
+ assert_eq!(unaligned.suffix(), None);
+ assert!(unaligned.chunks().is_empty());
+ assert_eq!(unaligned.lead_padding(), 0);
+ assert_eq!(unaligned.trailing_padding(), 32);
+
+ let unaligned = UnalignedBitChunk::new(buffer.as_slice(), 5, 27);
+
+ assert_eq!(unaligned.prefix(), Some(((1 << 32) - 1) - ((1 << 5) - 1)));
Review comment:
Yeah I agree that UnalignedBitChunkIterator isn't the easiest
construction to use, although this is sort of by design. It is not intended as
a replacement for BitChunkIterator, but rather something for where you are
willing to pay the cost of more complex start and termination logic, for
simpler logic within the main loop itself...
Would it allay your concerns if I made it pub(crate) so that we can continue
to iterate on it without introducing breaking changes?
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