Rich-T-kid commented on code in PR #10813:
URL: https://github.com/apache/arrow-rs/pull/10813#discussion_r3890088894
##########
arrow-select/src/take.rs:
##########
@@ -456,43 +456,229 @@ fn take_native<T: ArrowNativeType, I:
ArrowPrimitiveType>(
}
}
+/// Read the bit at `src_bit_idx` from `src` and, if it is set, write a `1` to
`dst_bit_idx`
+/// in `dst`. Leaves `dst_bit_idx` unchanged (zero) when the source bit is
unset.
+///
+/// ```text
+/// src = 0b00100000 (bit 5 is set)
+/// copy_bit_if_set(src, 5, dst, 2) → dst bit 2 becomes 1
+/// ```
+///
+/// # Safety
+/// - `src` must be valid for reads up to byte `src_bit_idx / 8`.
+/// - `dst` must be valid for writes up to byte `dst_bit_idx / 8`.
+#[inline(always)]
+unsafe fn copy_bit_if_set(src: *const u8, src_bit_idx: usize, dst: *mut u8,
dst_bit_idx: usize) {
Review Comment:
I tried this & compared the benchmarks to what already existed and the
results were within noise. Since the functions are always inlined I think what
ever compiler optimization may exist will be applied. I may be wrong as i'm not
super familiar with bitwise operations & all the neat tricks.
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