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Avoid overflow check in HashMap::reserve's fast path.

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This commit is contained in:
Nicholas Nethercote 2016-10-03 14:31:30 +11:00
parent 6a9b5e4c51
commit 607d2973da
1 changed files with 3 additions and 2 deletions
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5
src/libstd/collections/hash/map.rs
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@ -667,8 +667,9 @@ impl<K, V, S> HashMap<K, V, S>
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn reserve(&mut self, additional: usize) {
let min_cap = self.len().checked_add(additional).expect("reserve overflow");
if self.capacity() < min_cap {
let remaining = self.capacity() - self.len(); // this can't overflow
if remaining < additional {
let min_cap = self.len().checked_add(additional).expect("reserve overflow");
let raw_cap = self.resize_policy.raw_capacity(min_cap);
self.resize(raw_cap);
}