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Auto merge of rust-lang#85980 - ssomers:btree_cleanup_LeafRange, r=Ma…
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…rk-Simulacrum

BTree: encapsulate LeafRange better & some debug asserts

Looking at iterators again, I think rust-lang#81937 didn't house enough code in `LeafRange`. Moving the API boundary a little makes things more local in navigate.rs and less complicated in map.rs.

r? `@Mark-Simulacrum`
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@bors
bors committed Jun 20, 2021
2 parents e82b650 + b9d43c6 commit 03b845a
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Showing 6 changed files with 291 additions and 93 deletions.
39 changes: 32 additions & 7 deletions library/alloc/benches/btree/map.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -177,7 +177,7 @@ pub fn iteration_mut_100000(b: &mut Bencher) {
bench_iteration_mut(b, 100000);
}

fn bench_first_and_last(b: &mut Bencher, size: i32) {
fn bench_first_and_last_nightly(b: &mut Bencher, size: i32) {
let map: BTreeMap<_, _> = (0..size).map(|i| (i, i)).collect();
b.iter(|| {
for _ in 0..10 {
Expand All @@ -187,19 +187,44 @@ fn bench_first_and_last(b: &mut Bencher, size: i32) {
});
}

fn bench_first_and_last_stable(b: &mut Bencher, size: i32) {
let map: BTreeMap<_, _> = (0..size).map(|i| (i, i)).collect();
b.iter(|| {
for _ in 0..10 {
black_box(map.iter().next());
black_box(map.iter().next_back());
}
});
}

#[bench]
pub fn first_and_last_0_nightly(b: &mut Bencher) {
bench_first_and_last_nightly(b, 0);
}

#[bench]
pub fn first_and_last_0_stable(b: &mut Bencher) {
bench_first_and_last_stable(b, 0);
}

#[bench]
pub fn first_and_last_100_nightly(b: &mut Bencher) {
bench_first_and_last_nightly(b, 100);
}

#[bench]
pub fn first_and_last_0(b: &mut Bencher) {
bench_first_and_last(b, 0);
pub fn first_and_last_100_stable(b: &mut Bencher) {
bench_first_and_last_stable(b, 100);
}

#[bench]
pub fn first_and_last_100(b: &mut Bencher) {
bench_first_and_last(b, 100);
pub fn first_and_last_10k_nightly(b: &mut Bencher) {
bench_first_and_last_nightly(b, 10_000);
}

#[bench]
pub fn first_and_last_10k(b: &mut Bencher) {
bench_first_and_last(b, 10_000);
pub fn first_and_last_10k_stable(b: &mut Bencher) {
bench_first_and_last_stable(b, 10_000);
}

const BENCH_RANGE_SIZE: i32 = 145;
Expand Down
48 changes: 12 additions & 36 deletions library/alloc/src/collections/btree/map.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1299,7 +1299,7 @@ impl<'a, K: 'a, V: 'a> Iterator for Iter<'a, K, V> {
None
} else {
self.length -= 1;
Some(unsafe { self.range.next_unchecked() })
Some(unsafe { self.range.inner.next_unchecked() })
}
}

Expand Down Expand Up @@ -1330,7 +1330,7 @@ impl<'a, K: 'a, V: 'a> DoubleEndedIterator for Iter<'a, K, V> {
None
} else {
self.length -= 1;
Some(unsafe { self.range.next_back_unchecked() })
Some(unsafe { self.range.inner.next_back_unchecked() })
}
}
}
Expand Down Expand Up @@ -1368,7 +1368,7 @@ impl<'a, K: 'a, V: 'a> Iterator for IterMut<'a, K, V> {
None
} else {
self.length -= 1;
Some(unsafe { self.range.next_unchecked() })
Some(unsafe { self.range.inner.next_unchecked() })
}
}

Expand Down Expand Up @@ -1396,7 +1396,7 @@ impl<'a, K: 'a, V: 'a> DoubleEndedIterator for IterMut<'a, K, V> {
None
} else {
self.length -= 1;
Some(unsafe { self.range.next_back_unchecked() })
Some(unsafe { self.range.inner.next_back_unchecked() })
}
}
}
Expand Down Expand Up @@ -1475,7 +1475,7 @@ impl<K, V> Drop for Dropper<K, V> {
#[stable(feature = "btree_drop", since = "1.7.0")]
impl<K, V> Drop for IntoIter<K, V> {
fn drop(&mut self) {
if let Some(front) = self.range.front.take() {
if let Some(front) = self.range.take_front() {
Dropper { front, remaining_length: self.length };
}
}
Expand All @@ -1490,8 +1490,7 @@ impl<K, V> Iterator for IntoIter<K, V> {
None
} else {
self.length -= 1;
let front = self.range.front.as_mut().unwrap();
let kv = unsafe { front.deallocating_next_unchecked() };
let kv = unsafe { self.range.deallocating_next_unchecked() };
Some(kv.into_key_val())
}
}
Expand All @@ -1508,8 +1507,7 @@ impl<K, V> DoubleEndedIterator for IntoIter<K, V> {
None
} else {
self.length -= 1;
let back = self.range.back.as_mut().unwrap();
let kv = unsafe { back.deallocating_next_back_unchecked() };
let kv = unsafe { self.range.deallocating_next_back_unchecked() };
Some(kv.into_key_val())
}
}
Expand Down Expand Up @@ -1727,7 +1725,7 @@ impl<'a, K, V> Iterator for Range<'a, K, V> {
type Item = (&'a K, &'a V);

fn next(&mut self) -> Option<(&'a K, &'a V)> {
if self.inner.is_empty() { None } else { Some(unsafe { self.next_unchecked() }) }
self.inner.next_checked()
}

fn last(mut self) -> Option<(&'a K, &'a V)> {
Expand Down Expand Up @@ -1777,12 +1775,6 @@ impl<K, V> ExactSizeIterator for ValuesMut<'_, K, V> {
#[stable(feature = "fused", since = "1.26.0")]
impl<K, V> FusedIterator for ValuesMut<'_, K, V> {}

impl<'a, K, V> Range<'a, K, V> {
unsafe fn next_unchecked(&mut self) -> (&'a K, &'a V) {
unsafe { self.inner.front.as_mut().unwrap_unchecked().next_unchecked() }
}
}

#[stable(feature = "map_into_keys_values", since = "1.54.0")]
impl<K, V> Iterator for IntoKeys<K, V> {
type Item = K;
Expand Down Expand Up @@ -1862,13 +1854,7 @@ impl<K, V> FusedIterator for IntoValues<K, V> {}
#[stable(feature = "btree_range", since = "1.17.0")]
impl<'a, K, V> DoubleEndedIterator for Range<'a, K, V> {
fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
if self.inner.is_empty() { None } else { Some(unsafe { self.next_back_unchecked() }) }
}
}

impl<'a, K, V> Range<'a, K, V> {
unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a V) {
unsafe { self.inner.back.as_mut().unwrap_unchecked().next_back_unchecked() }
self.inner.next_back_checked()
}
}

Expand All @@ -1878,7 +1864,7 @@ impl<K, V> FusedIterator for Range<'_, K, V> {}
#[stable(feature = "btree_range", since = "1.17.0")]
impl<K, V> Clone for Range<'_, K, V> {
fn clone(&self) -> Self {
Range { inner: LeafRange { front: self.inner.front, back: self.inner.back } }
Range { inner: self.inner.clone() }
}
}

Expand All @@ -1887,7 +1873,7 @@ impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
type Item = (&'a K, &'a mut V);

fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
if self.inner.is_empty() { None } else { Some(unsafe { self.next_unchecked() }) }
self.inner.next_checked()
}

fn last(mut self) -> Option<(&'a K, &'a mut V)> {
Expand All @@ -1904,10 +1890,6 @@ impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
}

impl<'a, K, V> RangeMut<'a, K, V> {
unsafe fn next_unchecked(&mut self) -> (&'a K, &'a mut V) {
unsafe { self.inner.front.as_mut().unwrap_unchecked().next_unchecked() }
}

/// Returns an iterator of references over the remaining items.
#[inline]
pub(super) fn iter(&self) -> Range<'_, K, V> {
Expand All @@ -1918,19 +1900,13 @@ impl<'a, K, V> RangeMut<'a, K, V> {
#[stable(feature = "btree_range", since = "1.17.0")]
impl<'a, K, V> DoubleEndedIterator for RangeMut<'a, K, V> {
fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> {
if self.inner.is_empty() { None } else { Some(unsafe { self.next_back_unchecked() }) }
self.inner.next_back_checked()
}
}

#[stable(feature = "fused", since = "1.26.0")]
impl<K, V> FusedIterator for RangeMut<'_, K, V> {}

impl<'a, K, V> RangeMut<'a, K, V> {
unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a mut V) {
unsafe { self.inner.back.as_mut().unwrap_unchecked().next_back_unchecked() }
}
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<K: Ord, V> FromIterator<(K, V)> for BTreeMap<K, V> {
fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> BTreeMap<K, V> {
Expand Down
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