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bounded: make sure lap does not overflow into index #12

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bounded: make sure lap does not overflow into index 
.wrapping_add() is not enuough to ensure this, it is possible to end
up with index=1 if usize overflows. This is unlikely on 64-bit
systems, but possible on 32-bit systems.
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@link2xt
link2xt committed May 15, 2021
commit c8db484640bbfe662db3ea3a6e35ae5e65d186f8
4 changes: 2 additions & 2 deletions src/bounded.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -106,7 +106,7 @@ impl<T> Bounded<T> {
} else {
// One lap forward, index wraps around to zero.
// Set to `{ lap: lap.wrapping_add(1), mark: 0, index: 0 }`.
lap.wrapping_add(self.one_lap)
lap.wrapping_add(self.one_lap) & !(self.one_lap - 1)
};

// Try moving the tail.
Expand Down Expand Up @@ -169,7 +169,7 @@ impl<T> Bounded<T> {
} else {
// One lap forward, index wraps around to zero.
// Set to `{ lap: lap.wrapping_add(1), mark: 0, index: 0 }`.
lap.wrapping_add(self.one_lap)
lap.wrapping_add(self.one_lap) & !(self.one_lap - 1)
};

// Try moving the head.
Expand Down