bjoernager/rust
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extract IntoIter drop/forget used by specialization into separate methods

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This commit is contained in:
The8472 2020-01-26 20:50:05 +01:00
parent 6ad133443a
commit 771b8ecc83
1 changed files with 25 additions and 15 deletions
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40
library/alloc/src/vec.rs
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@ -2226,9 +2226,9 @@ where
return SpecFromNested::from_iter(iterator); return SpecFromNested::from_iter(iterator);
} }
let (src_buf, src_end) = { let (src_buf, src_end, cap) = {
let inner = unsafe { iterator.as_inner().as_into_iter() }; let inner = unsafe { iterator.as_inner().as_into_iter() };
(inner.buf.as_ptr(), inner.end) (inner.buf.as_ptr(), inner.end, inner.cap)
}; };
let dst = src_buf; let dst = src_buf;
@ -2278,23 +2278,15 @@ where
debug_assert_eq!(src_buf, src.buf.as_ptr()); debug_assert_eq!(src_buf, src.buf.as_ptr());
debug_assert!(dst as *const _ <= src.ptr, "InPlaceIterable contract violation"); debug_assert!(dst as *const _ <= src.ptr, "InPlaceIterable contract violation");
if mem::needs_drop::<T>() { // drop any remaining values at the tail of the source
// drop tail if iterator was only partially exhausted src.drop_in_place();
unsafe { // but prevent drop of the allocation itself once IntoIter goes out of scope
ptr::drop_in_place(src.as_mut_slice()); src.forget_in_place();
}
}
let vec = unsafe { let vec = unsafe {
let len = dst.offset_from(src_buf) as usize; let len = dst.offset_from(src_buf) as usize;
Vec::from_raw_parts(src.buf.as_ptr(), len, src.cap) Vec::from_raw_parts(src_buf, len, cap)
}; };
// prevent drop of the underlying storage by turning the IntoIter into
// the equivalent of Vec::new().into_iter()
src.cap = 0;
src.buf = unsafe { NonNull::new_unchecked(RawVec::NEW.ptr()) };
src.ptr = src.buf.as_ptr();
src.end = src.buf.as_ptr();
vec vec
} }
@ -2839,6 +2831,24 @@ impl<T> IntoIter<T> {
fn as_raw_mut_slice(&mut self) -> *mut [T] { fn as_raw_mut_slice(&mut self) -> *mut [T] {
ptr::slice_from_raw_parts_mut(self.ptr as *mut T, self.len()) ptr::slice_from_raw_parts_mut(self.ptr as *mut T, self.len())
} }
fn drop_in_place(&mut self) {
if mem::needs_drop::<T>() {
unsafe {
ptr::drop_in_place(self.as_mut_slice());
}
}
self.ptr = self.end;
}
/// Relinquishes the backing allocation, equivalent to
/// `ptr::write(&mut self, Vec::new().into_iter())`
fn forget_in_place(&mut self) {
self.cap = 0;
self.buf = unsafe { NonNull::new_unchecked(RawVec::NEW.ptr()) };
self.ptr = self.buf.as_ptr();
self.end = self.buf.as_ptr();
}
} }
#[stable(feature = "vec_intoiter_as_ref", since = "1.46.0")] #[stable(feature = "vec_intoiter_as_ref", since = "1.46.0")]