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Tune RepeatWith::try_fold and Take::for_each and Vec::extend_trusted

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This commit is contained in:
Scott McMurray 2022-11-24 19:14:19 -08:00
parent a8954f1f6a
commit 9d68a1a74c
6 changed files with 73 additions and 6 deletions
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9
library/alloc/src/vec/mod.rs
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@ -2874,13 +2874,12 @@ impl<T, A: Allocator> Vec<T, A> {
);
self.reserve(additional);
unsafe {
let mut ptr = self.as_mut_ptr().add(self.len());
let ptr = self.as_mut_ptr();
let mut local_len = SetLenOnDrop::new(&mut self.len);
iterator.for_each(move |element| {
ptr::write(ptr, element);
ptr = ptr.add(1);
// Since the loop executes user code which can panic we have to bump the pointer
// after each step.
ptr::write(ptr.add(local_len.current_len()), element);
// Since the loop executes user code which can panic we have to update
// the length every step to correctly drop what we've written.
// NB can't overflow since we would have had to alloc the address space
local_len.increment_len(1);
});