diff options
| -rw-r--r-- | library/alloc/benches/vec.rs | 6 | ||||
| -rw-r--r-- | library/core/src/array/iter.rs | 16 |
2 files changed, 22 insertions, 0 deletions
diff --git a/library/alloc/benches/vec.rs b/library/alloc/benches/vec.rs index 91eec10d575..c93a493cadb 100644 --- a/library/alloc/benches/vec.rs +++ b/library/alloc/benches/vec.rs @@ -726,3 +726,9 @@ fn bench_dedup_old_100000(b: &mut Bencher) { fn bench_dedup_new_100000(b: &mut Bencher) { bench_vec_dedup_new(b, 100000); } + +#[bench] +fn bench_flat_map_collect(b: &mut Bencher) { + let v = vec![777u32; 500000]; + b.iter(|| v.iter().flat_map(|color| color.rotate_left(8).to_be_bytes()).collect::<Vec<_>>()); +} diff --git a/library/core/src/array/iter.rs b/library/core/src/array/iter.rs index 61ab1b1faff..004d1736b0f 100644 --- a/library/core/src/array/iter.rs +++ b/library/core/src/array/iter.rs @@ -123,6 +123,22 @@ impl<T, const N: usize> Iterator for IntoIter<T, N> { (len, Some(len)) } + #[inline] + fn fold<Acc, Fold>(mut self, init: Acc, mut fold: Fold) -> Acc + where + Fold: FnMut(Acc, Self::Item) -> Acc, + { + let data = &mut self.data; + (&mut self.alive) + .try_fold::<_, _, Result<_, !>>(init, |acc, idx| { + // SAFETY: idx is obtained by folding over the `alive` range, which implies the + // value is currently considered alive but as the range is being consumed each value + // we read here will only be read once and then considered dead. + Ok(fold(acc, unsafe { data.get_unchecked(idx).assume_init_read() })) + }) + .unwrap() + } + fn count(self) -> usize { self.len() } |