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Resolve arith overflow on with_capacity #628

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Merged
merged 3 commits into from
Nov 10, 2023
Merged

Resolve arith overflow on with_capacity #628

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663043a
resolve arith overflow on with_capacity
HeeillWang Sep 19, 2023
c6e5d4f
enhance panic message
HeeillWang Sep 20, 2023
f1f4c6f
add panic condition on doc of with_capacity()
HeeillWang Sep 24, 2023
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20 changes: 18 additions & 2 deletions src/header/map.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -452,6 +452,10 @@ impl<T> HeaderMap<T> {
/// allocations before `capacity` headers are stored in the map.
///
/// More capacity than requested may be allocated.
///
/// # Panics
///
/// Requested capacity too large: would overflow `usize`.
///
/// # Examples
///
Expand All @@ -472,7 +476,13 @@ impl<T> HeaderMap<T> {
danger: Danger::Green,
}
} else {
let raw_cap = to_raw_capacity(capacity).next_power_of_two();
let raw_cap = match to_raw_capacity(capacity).checked_next_power_of_two() {
Some(c) => c,
None => panic!(
"requested capacity {} too large: next power of two would overflow `usize`",
capacity
),
};
assert!(raw_cap <= MAX_SIZE, "requested capacity too large");
debug_assert!(raw_cap > 0);

Expand Down Expand Up @@ -3218,7 +3228,13 @@ fn usable_capacity(cap: usize) -> usize {

#[inline]
fn to_raw_capacity(n: usize) -> usize {
n + n / 3
match n.checked_add(n / 3) {
Some(n) => n,
None => panic!(
"requested capacity {} too large: overflow while converting to raw capacity",
n
),
}
Comment on lines +3231 to +3237
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@WhyNotHugo WhyNotHugo Sep 24, 2023 •
edited
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TBH, this could just be:

n.checked_add(n / 3).expect("requested capacity must fit usize without overflow")

The only downside if that the requested capacity is not shown in the error, so maybe you'll want to hear what the maintainers think before applying any changes.

(the same applies to the above match that basically hand-rolls an expect).

}

#[inline]
Expand Down