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Arc: refactor data_offset{_sized}.

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This commit is contained in:
Mazdak Farrokhzad 2019-06-19 10:00:24 +02:00
parent 27f5d0f208
commit 59ecff915c
1 changed files with 9 additions and 8 deletions
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17
src/liballoc/sync.rs
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@ -2298,20 +2298,21 @@ impl<T: ?Sized> AsRef<T> for Arc<T> {
#[stable(feature = "pin", since = "1.33.0")]
impl<T: ?Sized> Unpin for Arc<T> { }
/// Computes the offset of the data field within ArcInner.
/// Computes the offset of the data field within `ArcInner`.
unsafe fn data_offset<T: ?Sized>(ptr: *const T) -> isize {
// Align the unsized value to the end of the ArcInner.
// Because it is ?Sized, it will always be the last field in memory.
let align = align_of_val(&*ptr);
let layout = Layout::new::<ArcInner<()>>();
(layout.size() + layout.padding_needed_for(align)) as isize
// Align the unsized value to the end of the `ArcInner`.
// Because it is `?Sized`, it will always be the last field in memory.
data_offset_align(align_of_val(&*ptr))
}
/// Computes the offset of the data field within ArcInner.
/// Computes the offset of the data field within `ArcInner`.
///
/// Unlike [`data_offset`], this doesn't need the pointer, but it works only on `T: Sized`.
fn data_offset_sized<T>() -> isize {
let align = align_of::<T>();
data_offset_align(align_of::<T>())
}
fn data_offset_align(align: usize) -> isize {
let layout = Layout::new::<ArcInner<()>>();
(layout.size() + layout.padding_needed_for(align)) as isize
}