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binary_heap: Unify Extend implementation.

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Previously the bulk rebuild specialization was only available with Vec, and
for general iterators Extend only provided pre-allocation through reserve().

By using a drop guard, we can safely bulk rebuild even if the iterator may
panic. This allows benefiting from the bulk rebuild optimization without
collecting iterator elements into a Vec beforehand, which would nullify any
performance gains from bulk rebuild.
This commit is contained in:
Tatsuyuki Ishi 2023-02-25 17:03:03 +09:00
parent 11c589c046
commit 116bb4dfb2
1 changed files with 2 additions and 34 deletions
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36
library/alloc/src/collections/binary_heap/mod.rs
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@ -154,8 +154,6 @@ use crate::collections::TryReserveError;
use crate::slice;
use crate::vec::{self, AsVecIntoIter, Vec};
use super::SpecExtend;
#[cfg(test)]
mod tests;
@ -1715,7 +1713,8 @@ impl<'a, T> IntoIterator for &'a BinaryHeap<T> {
impl<T: Ord> Extend<T> for BinaryHeap<T> {
#[inline]
fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
<Self as SpecExtend<I>>::spec_extend(self, iter);
let guard = RebuildOnDrop { rebuild_from: self.len(), heap: self };
guard.heap.data.extend(iter);
}
#[inline]
@ -1729,37 +1728,6 @@ impl<T: Ord> Extend<T> for BinaryHeap<T> {
}
}
impl<T: Ord, I: IntoIterator<Item = T>> SpecExtend<I> for BinaryHeap<T> {
default fn spec_extend(&mut self, iter: I) {
self.extend_desugared(iter.into_iter());
}
}
impl<T: Ord> SpecExtend<Vec<T>> for BinaryHeap<T> {
fn spec_extend(&mut self, ref mut other: Vec<T>) {
let start = self.data.len();
self.data.append(other);
self.rebuild_tail(start);
}
}
impl<T: Ord> SpecExtend<BinaryHeap<T>> for BinaryHeap<T> {
fn spec_extend(&mut self, ref mut other: BinaryHeap<T>) {
self.append(other);
}
}
impl<T: Ord> BinaryHeap<T> {
fn extend_desugared<I: IntoIterator<Item = T>>(&mut self, iter: I) {
let iterator = iter.into_iter();
let (lower, _) = iterator.size_hint();
self.reserve(lower);
iterator.for_each(move |elem| self.push(elem));
}
}
#[stable(feature = "extend_ref", since = "1.2.0")]
impl<'a, T: 'a + Ord + Copy> Extend<&'a T> for BinaryHeap<T> {
fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {