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fix: Prevent panic in try_reserve/try_with_capacity on capacity overflow #787

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merged 1 commit into from
Oct 27, 2025
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fix: Prevent panic in try_reserve/try_with_capacity on capacity overflow #787

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15 changes: 5 additions & 10 deletions src/header/map.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -552,7 +552,8 @@ impl<T> HeaderMap<T> {
if capacity == 0 {
Ok(Self::default())
} else {
let raw_cap = match to_raw_capacity(capacity).checked_next_power_of_two() {
let raw_cap = to_raw_capacity(capacity)?;
let raw_cap = match raw_cap.checked_next_power_of_two() {
Some(c) => c,
None => return Err(MaxSizeReached { _priv: () }),
};
Expand Down Expand Up @@ -750,7 +751,7 @@ impl<T> HeaderMap<T> {
.checked_add(additional)
.ok_or_else(MaxSizeReached::new)?;

let raw_cap = to_raw_capacity(cap);
let raw_cap = to_raw_capacity(cap)?;

if raw_cap > self.indices.len() {
let raw_cap = raw_cap
Expand Down Expand Up @@ -3621,14 +3622,8 @@ fn usable_capacity(cap: usize) -> usize {
}

#[inline]
fn to_raw_capacity(n: usize) -> usize {
match n.checked_add(n / 3) {
Some(n) => n,
None => panic!(
"requested capacity {} too large: overflow while converting to raw capacity",
n
),
}
fn to_raw_capacity(n: usize) -> Result<usize, MaxSizeReached> {
n.checked_add(n / 3).ok_or_else(MaxSizeReached::new)
}

#[inline]
Expand Down