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perf(BitField): optimize len #2258

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perf(BitField): optimize len #2258

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bd00400
optimize bitfield len
wjmelements Feb 5, 2026
3d53748
cargo fmt
wjmelements Feb 5, 2026
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11 changes: 10 additions & 1 deletion ipld/bitfield/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -322,7 +322,16 @@ impl BitField {

/// Returns the number of set bits in the bit field.
pub fn len(&self) -> u64 {
self.ranges().map(|range| range.size()).sum()
(self.set.len() as u64)
+ self
.ranges
.iter()
.map(|range| {
range.size()
- (self.unset.range(range.clone()).count() as u64)
- (self.set.range(range.clone()).count() as u64)
Comment on lines +330 to +332
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@LesnyRumcajs LesnyRumcajs Feb 10, 2026

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Not sure about the correctness of the implementation per se, probably some more (fuzz?) tests would do.

In this particular case, I see a potential danger of integer underflow, i.e., if range.size() < ((self.unset.range(range.clone()).count() as u64) + (self.set.range(range.clone()).count() as u64)) then some absurd values could get produced. Given we have overflow-checks = true for wasm profile, it'd probably panic (bad). Can we guarantee the condition above doesn't happen? Is it already guaranteed from some internal logic? If so, some comment to reassure the reader would help.

})
.sum::<u64>()
}

/// Returns a new bit field containing the bits in `self` that remain
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