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Liballoc intoiter refactor #73951

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Merged
merged 3 commits into from
Sep 12, 2020
Merged

Liballoc intoiter refactor #73951

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2b7f87b
Liballoc tweak use *const T instead of *const i8
pickfire Jul 2, 2020
cc0d634
Liballoc IntoIter limit unsafe to pointer arithmethic
pickfire Jul 2, 2020
5031523
Liballoc DoubleEndedIterator limit unsafe to pointer arithmethic
pickfire Jul 5, 2020
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58 changes: 25 additions & 33 deletions library/alloc/src/vec.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2697,25 +2697,21 @@ impl<T> Iterator for IntoIter<T> {

#[inline]
fn next(&mut self) -> Option<T> {
unsafe {
if self.ptr as *const _ == self.end {
None
} else {
if mem::size_of::<T>() == 0 {
// purposefully don't use 'ptr.offset' because for
// vectors with 0-size elements this would return the
// same pointer.
self.ptr = arith_offset(self.ptr as *const i8, 1) as *mut T;

// Make up a value of this ZST.
Some(mem::zeroed())
} else {
let old = self.ptr;
self.ptr = self.ptr.offset(1);

Some(ptr::read(old))
}
}
if self.ptr as *const _ == self.end {
None
} else if mem::size_of::<T>() == 0 {
// purposefully don't use 'ptr.offset' because for
// vectors with 0-size elements this would return the
// same pointer.
self.ptr = unsafe { arith_offset(self.ptr as *const i8, 1) as *mut T };

// Make up a value of this ZST.
Some(unsafe { mem::zeroed() })
} else {
let old = self.ptr;
self.ptr = unsafe { self.ptr.offset(1) };

Some(unsafe { ptr::read(old) })
}
}

Expand All @@ -2739,22 +2735,18 @@ impl<T> Iterator for IntoIter<T> {
impl<T> DoubleEndedIterator for IntoIter<T> {
#[inline]
fn next_back(&mut self) -> Option<T> {
unsafe {
if self.end == self.ptr {
None
} else {
if mem::size_of::<T>() == 0 {
// See above for why 'ptr.offset' isn't used
self.end = arith_offset(self.end as *const i8, -1) as *mut T;
if self.end == self.ptr {
None
} else if mem::size_of::<T>() == 0 {
// See above for why 'ptr.offset' isn't used
self.end = unsafe { arith_offset(self.end as *const i8, -1) as *mut T };

// Make up a value of this ZST.
Some(mem::zeroed())
} else {
self.end = self.end.offset(-1);
// Make up a value of this ZST.
Some(unsafe { mem::zeroed() })
} else {
self.end = unsafe { self.end.offset(-1) };

Some(ptr::read(self.end))
}
}
Some(unsafe { ptr::read(self.end) })
}
}
}
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