Make Arc
support DSTs
This commit is contained in:
parent
d332aead90
commit
e840393625
@ -77,11 +77,12 @@ use core::atomic;
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use core::atomic::Ordering::{Relaxed, Release, Acquire, SeqCst};
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use core::fmt;
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use core::cmp::Ordering;
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use core::mem::{min_align_of, size_of};
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use core::mem::{min_align_of_val, size_of_val};
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use core::intrinsics::drop_in_place;
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use core::mem;
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use core::nonzero::NonZero;
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use core::ops::Deref;
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use core::ptr;
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use core::ops::{Deref, CoerceUnsized};
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use core::marker::Unsize;
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use core::hash::{Hash, Hasher};
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use heap::deallocate;
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@ -118,15 +119,16 @@ use heap::deallocate;
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/// ```
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#[unsafe_no_drop_flag]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub struct Arc<T> {
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pub struct Arc<T: ?Sized> {
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// FIXME #12808: strange name to try to avoid interfering with
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// field accesses of the contained type via Deref
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_ptr: NonZero<*mut ArcInner<T>>,
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}
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unsafe impl<T: Sync + Send> Send for Arc<T> { }
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unsafe impl<T: Sync + Send> Sync for Arc<T> { }
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unsafe impl<T: ?Sized + Sync + Send> Send for Arc<T> { }
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unsafe impl<T: ?Sized + Sync + Send> Sync for Arc<T> { }
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impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Arc<U>> for Arc<T> {}
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/// A weak pointer to an `Arc`.
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///
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@ -135,30 +137,30 @@ unsafe impl<T: Sync + Send> Sync for Arc<T> { }
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#[unsafe_no_drop_flag]
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#[unstable(feature = "alloc",
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reason = "Weak pointers may not belong in this module.")]
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pub struct Weak<T> {
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pub struct Weak<T: ?Sized> {
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// FIXME #12808: strange name to try to avoid interfering with
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// field accesses of the contained type via Deref
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_ptr: NonZero<*mut ArcInner<T>>,
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}
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unsafe impl<T: Sync + Send> Send for Weak<T> { }
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unsafe impl<T: Sync + Send> Sync for Weak<T> { }
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unsafe impl<T: ?Sized + Sync + Send> Send for Weak<T> { }
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unsafe impl<T: ?Sized + Sync + Send> Sync for Weak<T> { }
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: fmt::Debug> fmt::Debug for Weak<T> {
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impl<T: ?Sized + fmt::Debug> fmt::Debug for Weak<T> {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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write!(f, "(Weak)")
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}
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}
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struct ArcInner<T> {
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struct ArcInner<T: ?Sized> {
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strong: atomic::AtomicUsize,
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weak: atomic::AtomicUsize,
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data: T,
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}
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unsafe impl<T: Sync + Send> Send for ArcInner<T> {}
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unsafe impl<T: Sync + Send> Sync for ArcInner<T> {}
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unsafe impl<T: ?Sized + Sync + Send> Send for ArcInner<T> {}
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unsafe impl<T: ?Sized + Sync + Send> Sync for ArcInner<T> {}
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impl<T> Arc<T> {
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/// Constructs a new `Arc<T>`.
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@ -182,7 +184,9 @@ impl<T> Arc<T> {
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};
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Arc { _ptr: unsafe { NonZero::new(mem::transmute(x)) } }
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}
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}
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impl<T: ?Sized> Arc<T> {
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/// Downgrades the `Arc<T>` to a `Weak<T>` reference.
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///
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/// # Examples
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@ -204,7 +208,7 @@ impl<T> Arc<T> {
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}
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}
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impl<T> Arc<T> {
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impl<T: ?Sized> Arc<T> {
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#[inline]
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fn inner(&self) -> &ArcInner<T> {
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// This unsafety is ok because while this arc is alive we're guaranteed
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@ -222,11 +226,11 @@ impl<T> Arc<T> {
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// Destroy the data at this time, even though we may not free the box
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// allocation itself (there may still be weak pointers lying around).
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drop(ptr::read(&self.inner().data));
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drop_in_place(&mut (*ptr).data);
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if self.inner().weak.fetch_sub(1, Release) == 1 {
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atomic::fence(Acquire);
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deallocate(ptr as *mut u8, size_of::<ArcInner<T>>(), min_align_of::<ArcInner<T>>())
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deallocate(ptr as *mut u8, size_of_val(&*ptr), min_align_of_val(&*ptr))
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}
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}
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}
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@ -234,12 +238,12 @@ impl<T> Arc<T> {
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/// Get the number of weak references to this value.
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#[inline]
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#[unstable(feature = "alloc")]
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pub fn weak_count<T>(this: &Arc<T>) -> usize { this.inner().weak.load(SeqCst) - 1 }
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pub fn weak_count<T: ?Sized>(this: &Arc<T>) -> usize { this.inner().weak.load(SeqCst) - 1 }
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/// Get the number of strong references to this value.
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#[inline]
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#[unstable(feature = "alloc")]
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pub fn strong_count<T>(this: &Arc<T>) -> usize { this.inner().strong.load(SeqCst) }
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pub fn strong_count<T: ?Sized>(this: &Arc<T>) -> usize { this.inner().strong.load(SeqCst) }
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/// Returns a mutable reference to the contained value if the `Arc<T>` is unique.
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@ -264,7 +268,7 @@ pub fn strong_count<T>(this: &Arc<T>) -> usize { this.inner().strong.load(SeqCst
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/// ```
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#[inline]
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#[unstable(feature = "alloc")]
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pub fn get_mut<T>(this: &mut Arc<T>) -> Option<&mut T> {
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pub fn get_mut<T: ?Sized>(this: &mut Arc<T>) -> Option<&mut T> {
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if strong_count(this) == 1 && weak_count(this) == 0 {
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// This unsafety is ok because we're guaranteed that the pointer
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// returned is the *only* pointer that will ever be returned to T. Our
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@ -279,7 +283,7 @@ pub fn get_mut<T>(this: &mut Arc<T>) -> Option<&mut T> {
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T> Clone for Arc<T> {
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impl<T: ?Sized> Clone for Arc<T> {
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/// Makes a clone of the `Arc<T>`.
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///
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/// This increases the strong reference count.
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@ -313,7 +317,7 @@ impl<T> Clone for Arc<T> {
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T> Deref for Arc<T> {
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impl<T: ?Sized> Deref for Arc<T> {
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type Target = T;
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#[inline]
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@ -356,7 +360,7 @@ impl<T: Clone> Arc<T> {
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T> Drop for Arc<T> {
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impl<T: ?Sized> Drop for Arc<T> {
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/// Drops the `Arc<T>`.
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///
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/// This will decrement the strong reference count. If the strong reference
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@ -390,7 +394,7 @@ impl<T> Drop for Arc<T> {
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// it's run more than once)
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let ptr = *self._ptr;
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// if ptr.is_null() { return }
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if ptr.is_null() || ptr as usize == mem::POST_DROP_USIZE { return }
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if ptr as usize == 0 || ptr as usize == mem::POST_DROP_USIZE { return }
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// Because `fetch_sub` is already atomic, we do not need to synchronize
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// with other threads unless we are going to delete the object. This
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@ -424,7 +428,7 @@ impl<T> Drop for Arc<T> {
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#[unstable(feature = "alloc",
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reason = "Weak pointers may not belong in this module.")]
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impl<T> Weak<T> {
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impl<T: ?Sized> Weak<T> {
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/// Upgrades a weak reference to a strong reference.
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///
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/// Upgrades the `Weak<T>` reference to an `Arc<T>`, if possible.
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@ -465,7 +469,7 @@ impl<T> Weak<T> {
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#[unstable(feature = "alloc",
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reason = "Weak pointers may not belong in this module.")]
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impl<T> Clone for Weak<T> {
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impl<T: ?Sized> Clone for Weak<T> {
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/// Makes a clone of the `Weak<T>`.
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///
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/// This increases the weak reference count.
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@ -489,7 +493,7 @@ impl<T> Clone for Weak<T> {
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T> Drop for Weak<T> {
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impl<T: ?Sized> Drop for Weak<T> {
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/// Drops the `Weak<T>`.
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///
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/// This will decrement the weak reference count.
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@ -520,21 +524,22 @@ impl<T> Drop for Weak<T> {
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let ptr = *self._ptr;
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// see comments above for why this check is here
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if ptr.is_null() || ptr as usize == mem::POST_DROP_USIZE { return }
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if ptr as usize == 0 || ptr as usize == mem::POST_DROP_USIZE { return }
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// If we find out that we were the last weak pointer, then its time to
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// deallocate the data entirely. See the discussion in Arc::drop() about
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// the memory orderings
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if self.inner().weak.fetch_sub(1, Release) == 1 {
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atomic::fence(Acquire);
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unsafe { deallocate(ptr as *mut u8, size_of::<ArcInner<T>>(),
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min_align_of::<ArcInner<T>>()) }
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unsafe { deallocate(ptr as *mut u8,
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size_of_val(&*ptr),
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min_align_of_val(&*ptr)) }
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}
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: PartialEq> PartialEq for Arc<T> {
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impl<T: ?Sized + PartialEq> PartialEq for Arc<T> {
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/// Equality for two `Arc<T>`s.
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///
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/// Two `Arc<T>`s are equal if their inner value are equal.
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@ -566,7 +571,7 @@ impl<T: PartialEq> PartialEq for Arc<T> {
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fn ne(&self, other: &Arc<T>) -> bool { *(*self) != *(*other) }
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: PartialOrd> PartialOrd for Arc<T> {
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impl<T: ?Sized + PartialOrd> PartialOrd for Arc<T> {
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/// Partial comparison for two `Arc<T>`s.
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///
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/// The two are compared by calling `partial_cmp()` on their inner values.
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@ -645,21 +650,21 @@ impl<T: PartialOrd> PartialOrd for Arc<T> {
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fn ge(&self, other: &Arc<T>) -> bool { *(*self) >= *(*other) }
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: Ord> Ord for Arc<T> {
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impl<T: ?Sized + Ord> Ord for Arc<T> {
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fn cmp(&self, other: &Arc<T>) -> Ordering { (**self).cmp(&**other) }
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: Eq> Eq for Arc<T> {}
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impl<T: ?Sized + Eq> Eq for Arc<T> {}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: fmt::Display> fmt::Display for Arc<T> {
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impl<T: ?Sized + fmt::Display> fmt::Display for Arc<T> {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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fmt::Display::fmt(&**self, f)
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: fmt::Debug> fmt::Debug for Arc<T> {
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impl<T: ?Sized + fmt::Debug> fmt::Debug for Arc<T> {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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fmt::Debug::fmt(&**self, f)
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}
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@ -679,7 +684,7 @@ impl<T: Default> Default for Arc<T> {
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: Hash> Hash for Arc<T> {
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impl<T: ?Sized + Hash> Hash for Arc<T> {
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fn hash<H: Hasher>(&self, state: &mut H) {
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(**self).hash(state)
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}
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@ -906,4 +911,13 @@ mod tests {
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// Make sure deriving works with Arc<T>
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#[derive(Eq, Ord, PartialEq, PartialOrd, Clone, Debug, Default)]
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struct Foo { inner: Arc<i32> }
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#[test]
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fn test_unsized() {
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let x: Arc<[i32]> = Arc::new([1, 2, 3]);
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assert_eq!(format!("{:?}", x), "[1, 2, 3]");
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let y = x.clone().downgrade();
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drop(x);
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assert!(y.upgrade().is_none());
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}
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}
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src/liballoc/arc_stage0.rs
Normal file
686
src/liballoc/arc_stage0.rs
Normal file
@ -0,0 +1,686 @@
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// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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#![stable(feature = "rust1", since = "1.0.0")]
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//! Threadsafe reference-counted boxes (the `Arc<T>` type).
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//!
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//! The `Arc<T>` type provides shared ownership of an immutable value.
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//! Destruction is deterministic, and will occur as soon as the last owner is
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//! gone. It is marked as `Send` because it uses atomic reference counting.
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//!
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//! If you do not need thread-safety, and just need shared ownership, consider
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//! the [`Rc<T>` type](../rc/struct.Rc.html). It is the same as `Arc<T>`, but
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//! does not use atomics, making it both thread-unsafe as well as significantly
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//! faster when updating the reference count.
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//!
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//! The `downgrade` method can be used to create a non-owning `Weak<T>` pointer
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//! to the box. A `Weak<T>` pointer can be upgraded to an `Arc<T>` pointer, but
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//! will return `None` if the value has already been dropped.
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//!
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//! For example, a tree with parent pointers can be represented by putting the
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//! nodes behind strong `Arc<T>` pointers, and then storing the parent pointers
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//! as `Weak<T>` pointers.
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//!
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//! # Examples
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//!
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//! Sharing some immutable data between threads:
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//!
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//! ```no_run
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//! use std::sync::Arc;
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//! use std::thread;
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//!
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//! let five = Arc::new(5);
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//!
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//! for _ in 0..10 {
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//! let five = five.clone();
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//!
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//! thread::spawn(move || {
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//! println!("{:?}", five);
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//! });
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//! }
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//! ```
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//!
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//! Sharing mutable data safely between threads with a `Mutex`:
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//!
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//! ```no_run
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//! use std::sync::{Arc, Mutex};
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//! use std::thread;
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//!
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//! let five = Arc::new(Mutex::new(5));
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//!
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//! for _ in 0..10 {
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//! let five = five.clone();
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//!
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//! thread::spawn(move || {
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//! let mut number = five.lock().unwrap();
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//!
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//! *number += 1;
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//!
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//! println!("{}", *number); // prints 6
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//! });
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//! }
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//! ```
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use boxed::Box;
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use core::prelude::*;
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use core::atomic;
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use core::atomic::Ordering::{Relaxed, Release, Acquire, SeqCst};
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use core::fmt;
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use core::cmp::Ordering;
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use core::mem::{min_align_of, size_of};
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use core::mem;
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use core::nonzero::NonZero;
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use core::ops::Deref;
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use core::ptr;
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use core::hash::{Hash, Hasher};
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use heap::deallocate;
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/// An atomically reference counted wrapper for shared state.
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///
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/// # Examples
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///
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/// In this example, a large vector of floats is shared between several threads.
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/// With simple pipes, without `Arc`, a copy would have to be made for each
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/// thread.
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///
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/// When you clone an `Arc<T>`, it will create another pointer to the data and
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/// increase the reference counter.
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///
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/// ```
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/// # #![feature(alloc, core)]
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/// use std::sync::Arc;
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/// use std::thread;
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///
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/// fn main() {
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/// let numbers: Vec<_> = (0..100u32).collect();
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/// let shared_numbers = Arc::new(numbers);
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///
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/// for _ in 0..10 {
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/// let child_numbers = shared_numbers.clone();
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///
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/// thread::spawn(move || {
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/// let local_numbers = &child_numbers[..];
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///
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/// // Work with the local numbers
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/// });
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/// }
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/// }
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/// ```
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#[unsafe_no_drop_flag]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub struct Arc<T> {
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// FIXME #12808: strange name to try to avoid interfering with
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// field accesses of the contained type via Deref
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_ptr: NonZero<*mut ArcInner<T>>,
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}
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unsafe impl<T: Sync + Send> Send for Arc<T> { }
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unsafe impl<T: Sync + Send> Sync for Arc<T> { }
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/// A weak pointer to an `Arc`.
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///
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/// Weak pointers will not keep the data inside of the `Arc` alive, and can be
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/// used to break cycles between `Arc` pointers.
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#[unsafe_no_drop_flag]
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#[unstable(feature = "alloc",
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reason = "Weak pointers may not belong in this module.")]
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pub struct Weak<T> {
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// FIXME #12808: strange name to try to avoid interfering with
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// field accesses of the contained type via Deref
|
||||
_ptr: NonZero<*mut ArcInner<T>>,
|
||||
}
|
||||
|
||||
unsafe impl<T: Sync + Send> Send for Weak<T> { }
|
||||
unsafe impl<T: Sync + Send> Sync for Weak<T> { }
|
||||
|
||||
#[stable(feature = "rust1", since = "1.0.0")]
|
||||
impl<T: fmt::Debug> fmt::Debug for Weak<T> {
|
||||
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
||||
write!(f, "(Weak)")
|
||||
}
|
||||
}
|
||||
|
||||
struct ArcInner<T> {
|
||||
strong: atomic::AtomicUsize,
|
||||
weak: atomic::AtomicUsize,
|
||||
data: T,
|
||||
}
|
||||
|
||||
unsafe impl<T: Sync + Send> Send for ArcInner<T> {}
|
||||
unsafe impl<T: Sync + Send> Sync for ArcInner<T> {}
|
||||
|
||||
impl<T> Arc<T> {
|
||||
/// Constructs a new `Arc<T>`.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// use std::sync::Arc;
|
||||
///
|
||||
/// let five = Arc::new(5);
|
||||
/// ```
|
||||
#[inline]
|
||||
#[stable(feature = "rust1", since = "1.0.0")]
|
||||
pub fn new(data: T) -> Arc<T> {
|
||||
// Start the weak pointer count as 1 which is the weak pointer that's
|
||||
// held by all the strong pointers (kinda), see std/rc.rs for more info
|
||||
let x: Box<_> = box ArcInner {
|
||||
strong: atomic::AtomicUsize::new(1),
|
||||
weak: atomic::AtomicUsize::new(1),
|
||||
data: data,
|
||||
};
|
||||
Arc { _ptr: unsafe { NonZero::new(mem::transmute(x)) } }
|
||||
}
|
||||
|
||||
/// Downgrades the `Arc<T>` to a `Weak<T>` reference.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// # #![feature(alloc)]
|
||||
/// use std::sync::Arc;
|
||||
///
|
||||
/// let five = Arc::new(5);
|
||||
///
|
||||
/// let weak_five = five.downgrade();
|
||||
/// ```
|
||||
#[unstable(feature = "alloc",
|
||||
reason = "Weak pointers may not belong in this module.")]
|
||||
pub fn downgrade(&self) -> Weak<T> {
|
||||
// See the clone() impl for why this is relaxed
|
||||
self.inner().weak.fetch_add(1, Relaxed);
|
||||
Weak { _ptr: self._ptr }
|
||||
}
|
||||
}
|
||||
|
||||
impl<T> Arc<T> {
|
||||
#[inline]
|
||||
fn inner(&self) -> &ArcInner<T> {
|
||||
// This unsafety is ok because while this arc is alive we're guaranteed
|
||||
// that the inner pointer is valid. Furthermore, we know that the
|
||||
// `ArcInner` structure itself is `Sync` because the inner data is
|
||||
// `Sync` as well, so we're ok loaning out an immutable pointer to these
|
||||
// contents.
|
||||
unsafe { &**self._ptr }
|
||||
}
|
||||
|
||||
// Non-inlined part of `drop`.
|
||||
#[inline(never)]
|
||||
unsafe fn drop_slow(&mut self) {
|
||||
let ptr = *self._ptr;
|
||||
|
||||
// Destroy the data at this time, even though we may not free the box
|
||||
// allocation itself (there may still be weak pointers lying around).
|
||||
drop(ptr::read(&self.inner().data));
|
||||
|
||||
if self.inner().weak.fetch_sub(1, Release) == 1 {
|
||||
atomic::fence(Acquire);
|
||||
deallocate(ptr as *mut u8, size_of::<ArcInner<T>>(), min_align_of::<ArcInner<T>>())
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/// Get the number of weak references to this value.
|
||||
#[inline]
|
||||
#[unstable(feature = "alloc")]
|
||||
pub fn weak_count<T>(this: &Arc<T>) -> usize { this.inner().weak.load(SeqCst) - 1 }
|
||||
|
||||
/// Get the number of strong references to this value.
|
||||
#[inline]
|
||||
#[unstable(feature = "alloc")]
|
||||
pub fn strong_count<T>(this: &Arc<T>) -> usize { this.inner().strong.load(SeqCst) }
|
||||
|
||||
|
||||
/// Returns a mutable reference to the contained value if the `Arc<T>` is unique.
|
||||
///
|
||||
/// Returns `None` if the `Arc<T>` is not unique.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// # #![feature(alloc)]
|
||||
/// extern crate alloc;
|
||||
/// # fn main() {
|
||||
/// use alloc::arc::{Arc, get_mut};
|
||||
///
|
||||
/// let mut x = Arc::new(3);
|
||||
/// *get_mut(&mut x).unwrap() = 4;
|
||||
/// assert_eq!(*x, 4);
|
||||
///
|
||||
/// let _y = x.clone();
|
||||
/// assert!(get_mut(&mut x).is_none());
|
||||
/// # }
|
||||
/// ```
|
||||
#[inline]
|
||||
#[unstable(feature = "alloc")]
|
||||
pub fn get_mut<T>(this: &mut Arc<T>) -> Option<&mut T> {
|
||||
if strong_count(this) == 1 && weak_count(this) == 0 {
|
||||
// This unsafety is ok because we're guaranteed that the pointer
|
||||
// returned is the *only* pointer that will ever be returned to T. Our
|
||||
// reference count is guaranteed to be 1 at this point, and we required
|
||||
// the Arc itself to be `mut`, so we're returning the only possible
|
||||
// reference to the inner data.
|
||||
let inner = unsafe { &mut **this._ptr };
|
||||
Some(&mut inner.data)
|
||||
} else {
|
||||
None
|
||||
}
|
||||
}
|
||||
|
||||
#[stable(feature = "rust1", since = "1.0.0")]
|
||||
impl<T> Clone for Arc<T> {
|
||||
/// Makes a clone of the `Arc<T>`.
|
||||
///
|
||||
/// This increases the strong reference count.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// # #![feature(alloc)]
|
||||
/// use std::sync::Arc;
|
||||
///
|
||||
/// let five = Arc::new(5);
|
||||
///
|
||||
/// five.clone();
|
||||
/// ```
|
||||
#[inline]
|
||||
fn clone(&self) -> Arc<T> {
|
||||
// Using a relaxed ordering is alright here, as knowledge of the
|
||||
// original reference prevents other threads from erroneously deleting
|
||||
// the object.
|
||||
//
|
||||
// As explained in the [Boost documentation][1], Increasing the
|
||||
// reference counter can always be done with memory_order_relaxed: New
|
||||
// references to an object can only be formed from an existing
|
||||
// reference, and passing an existing reference from one thread to
|
||||
// another must already provide any required synchronization.
|
||||
//
|
||||
// [1]: (www.boost.org/doc/libs/1_55_0/doc/html/atomic/usage_examples.html)
|
||||
self.inner().strong.fetch_add(1, Relaxed);
|
||||
Arc { _ptr: self._ptr }
|
||||
}
|
||||
}
|
||||
|
||||
#[stable(feature = "rust1", since = "1.0.0")]
|
||||
impl<T> Deref for Arc<T> {
|
||||
type Target = T;
|
||||
|
||||
#[inline]
|
||||
fn deref(&self) -> &T {
|
||||
&self.inner().data
|
||||
}
|
||||
}
|
||||
|
||||
impl<T: Clone> Arc<T> {
|
||||
/// Make a mutable reference from the given `Arc<T>`.
|
||||
///
|
||||
/// This is also referred to as a copy-on-write operation because the inner
|
||||
/// data is cloned if the reference count is greater than one.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// # #![feature(alloc)]
|
||||
/// use std::sync::Arc;
|
||||
///
|
||||
/// let mut five = Arc::new(5);
|
||||
///
|
||||
/// let mut_five = five.make_unique();
|
||||
/// ```
|
||||
#[inline]
|
||||
#[unstable(feature = "alloc")]
|
||||
pub fn make_unique(&mut self) -> &mut T {
|
||||
// Note that we hold a strong reference, which also counts as a weak
|
||||
// reference, so we only clone if there is an additional reference of
|
||||
// either kind.
|
||||
if self.inner().strong.load(SeqCst) != 1 ||
|
||||
self.inner().weak.load(SeqCst) != 1 {
|
||||
*self = Arc::new((**self).clone())
|
||||
}
|
||||
// As with `get_mut()`, the unsafety is ok because our reference was
|
||||
// either unique to begin with, or became one upon cloning the contents.
|
||||
let inner = unsafe { &mut **self._ptr };
|
||||
&mut inner.data
|
||||
}
|
||||
}
|
||||
|
||||
#[stable(feature = "rust1", since = "1.0.0")]
|
||||
impl<T> Drop for Arc<T> {
|
||||
/// Drops the `Arc<T>`.
|
||||
///
|
||||
/// This will decrement the strong reference count. If the strong reference
|
||||
/// count becomes zero and the only other references are `Weak<T>` ones,
|
||||
/// `drop`s the inner value.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// # #![feature(alloc)]
|
||||
/// use std::sync::Arc;
|
||||
///
|
||||
/// {
|
||||
/// let five = Arc::new(5);
|
||||
///
|
||||
/// // stuff
|
||||
///
|
||||
/// drop(five); // explicit drop
|
||||
/// }
|
||||
/// {
|
||||
/// let five = Arc::new(5);
|
||||
///
|
||||
/// // stuff
|
||||
///
|
||||
/// } // implicit drop
|
||||
/// ```
|
||||
#[inline]
|
||||
fn drop(&mut self) {
|
||||
// This structure has #[unsafe_no_drop_flag], so this drop glue may run
|
||||
// more than once (but it is guaranteed to be zeroed after the first if
|
||||
// it's run more than once)
|
||||
let ptr = *self._ptr;
|
||||
// if ptr.is_null() { return }
|
||||
if ptr.is_null() || ptr as usize == mem::POST_DROP_USIZE { return }
|
||||
|
||||
// Because `fetch_sub` is already atomic, we do not need to synchronize
|
||||
// with other threads unless we are going to delete the object. This
|
||||
// same logic applies to the below `fetch_sub` to the `weak` count.
|
||||
if self.inner().strong.fetch_sub(1, Release) != 1 { return }
|
||||
|
||||
// This fence is needed to prevent reordering of use of the data and
|
||||
// deletion of the data. Because it is marked `Release`, the decreasing
|
||||
// of the reference count synchronizes with this `Acquire` fence. This
|
||||
// means that use of the data happens before decreasing the reference
|
||||
// count, which happens before this fence, which happens before the
|
||||
// deletion of the data.
|
||||
//
|
||||
// As explained in the [Boost documentation][1],
|
||||
//
|
||||
// > It is important to enforce any possible access to the object in one
|
||||
// > thread (through an existing reference) to *happen before* deleting
|
||||
// > the object in a different thread. This is achieved by a "release"
|
||||
// > operation after dropping a reference (any access to the object
|
||||
// > through this reference must obviously happened before), and an
|
||||
// > "acquire" operation before deleting the object.
|
||||
//
|
||||
// [1]: (www.boost.org/doc/libs/1_55_0/doc/html/atomic/usage_examples.html)
|
||||
atomic::fence(Acquire);
|
||||
|
||||
unsafe {
|
||||
self.drop_slow()
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
#[unstable(feature = "alloc",
|
||||
reason = "Weak pointers may not belong in this module.")]
|
||||
impl<T> Weak<T> {
|
||||
/// Upgrades a weak reference to a strong reference.
|
||||
///
|
||||
/// Upgrades the `Weak<T>` reference to an `Arc<T>`, if possible.
|
||||
///
|
||||
/// Returns `None` if there were no strong references and the data was
|
||||
/// destroyed.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// # #![feature(alloc)]
|
||||
/// use std::sync::Arc;
|
||||
///
|
||||
/// let five = Arc::new(5);
|
||||
///
|
||||
/// let weak_five = five.downgrade();
|
||||
///
|
||||
/// let strong_five: Option<Arc<_>> = weak_five.upgrade();
|
||||
/// ```
|
||||
pub fn upgrade(&self) -> Option<Arc<T>> {
|
||||
// We use a CAS loop to increment the strong count instead of a
|
||||
// fetch_add because once the count hits 0 it must never be above 0.
|
||||
let inner = self.inner();
|
||||
loop {
|
||||
let n = inner.strong.load(SeqCst);
|
||||
if n == 0 { return None }
|
||||
let old = inner.strong.compare_and_swap(n, n + 1, SeqCst);
|
||||
if old == n { return Some(Arc { _ptr: self._ptr }) }
|
||||
}
|
||||
}
|
||||
|
||||
#[inline]
|
||||
fn inner(&self) -> &ArcInner<T> {
|
||||
// See comments above for why this is "safe"
|
||||
unsafe { &**self._ptr }
|
||||
}
|
||||
}
|
||||
|
||||
#[unstable(feature = "alloc",
|
||||
reason = "Weak pointers may not belong in this module.")]
|
||||
impl<T> Clone for Weak<T> {
|
||||
/// Makes a clone of the `Weak<T>`.
|
||||
///
|
||||
/// This increases the weak reference count.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// # #![feature(alloc)]
|
||||
/// use std::sync::Arc;
|
||||
///
|
||||
/// let weak_five = Arc::new(5).downgrade();
|
||||
///
|
||||
/// weak_five.clone();
|
||||
/// ```
|
||||
#[inline]
|
||||
fn clone(&self) -> Weak<T> {
|
||||
// See comments in Arc::clone() for why this is relaxed
|
||||
self.inner().weak.fetch_add(1, Relaxed);
|
||||
Weak { _ptr: self._ptr }
|
||||
}
|
||||
}
|
||||
|
||||
#[stable(feature = "rust1", since = "1.0.0")]
|
||||
impl<T> Drop for Weak<T> {
|
||||
/// Drops the `Weak<T>`.
|
||||
///
|
||||
/// This will decrement the weak reference count.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// # #![feature(alloc)]
|
||||
/// use std::sync::Arc;
|
||||
///
|
||||
/// {
|
||||
/// let five = Arc::new(5);
|
||||
/// let weak_five = five.downgrade();
|
||||
///
|
||||
/// // stuff
|
||||
///
|
||||
/// drop(weak_five); // explicit drop
|
||||
/// }
|
||||
/// {
|
||||
/// let five = Arc::new(5);
|
||||
/// let weak_five = five.downgrade();
|
||||
///
|
||||
/// // stuff
|
||||
///
|
||||
/// } // implicit drop
|
||||
/// ```
|
||||
fn drop(&mut self) {
|
||||
let ptr = *self._ptr;
|
||||
|
||||
// see comments above for why this check is here
|
||||
if ptr.is_null() || ptr as usize == mem::POST_DROP_USIZE { return }
|
||||
|
||||
// If we find out that we were the last weak pointer, then its time to
|
||||
// deallocate the data entirely. See the discussion in Arc::drop() about
|
||||
// the memory orderings
|
||||
if self.inner().weak.fetch_sub(1, Release) == 1 {
|
||||
atomic::fence(Acquire);
|
||||
unsafe { deallocate(ptr as *mut u8, size_of::<ArcInner<T>>(),
|
||||
min_align_of::<ArcInner<T>>()) }
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
#[stable(feature = "rust1", since = "1.0.0")]
|
||||
impl<T: PartialEq> PartialEq for Arc<T> {
|
||||
/// Equality for two `Arc<T>`s.
|
||||
///
|
||||
/// Two `Arc<T>`s are equal if their inner value are equal.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// use std::sync::Arc;
|
||||
///
|
||||
/// let five = Arc::new(5);
|
||||
///
|
||||
/// five == Arc::new(5);
|
||||
/// ```
|
||||
fn eq(&self, other: &Arc<T>) -> bool { *(*self) == *(*other) }
|
||||
|
||||
/// Inequality for two `Arc<T>`s.
|
||||
///
|
||||
/// Two `Arc<T>`s are unequal if their inner value are unequal.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// use std::sync::Arc;
|
||||
///
|
||||
/// let five = Arc::new(5);
|
||||
///
|
||||
/// five != Arc::new(5);
|
||||
/// ```
|
||||
fn ne(&self, other: &Arc<T>) -> bool { *(*self) != *(*other) }
|
||||
}
|
||||
#[stable(feature = "rust1", since = "1.0.0")]
|
||||
impl<T: PartialOrd> PartialOrd for Arc<T> {
|
||||
/// Partial comparison for two `Arc<T>`s.
|
||||
///
|
||||
/// The two are compared by calling `partial_cmp()` on their inner values.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// use std::sync::Arc;
|
||||
///
|
||||
/// let five = Arc::new(5);
|
||||
///
|
||||
/// five.partial_cmp(&Arc::new(5));
|
||||
/// ```
|
||||
fn partial_cmp(&self, other: &Arc<T>) -> Option<Ordering> {
|
||||
(**self).partial_cmp(&**other)
|
||||
}
|
||||
|
||||
/// Less-than comparison for two `Arc<T>`s.
|
||||
///
|
||||
/// The two are compared by calling `<` on their inner values.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// use std::sync::Arc;
|
||||
///
|
||||
/// let five = Arc::new(5);
|
||||
///
|
||||
/// five < Arc::new(5);
|
||||
/// ```
|
||||
fn lt(&self, other: &Arc<T>) -> bool { *(*self) < *(*other) }
|
||||
|
||||
/// 'Less-than or equal to' comparison for two `Arc<T>`s.
|
||||
///
|
||||
/// The two are compared by calling `<=` on their inner values.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// use std::sync::Arc;
|
||||
///
|
||||
/// let five = Arc::new(5);
|
||||
///
|
||||
/// five <= Arc::new(5);
|
||||
/// ```
|
||||
fn le(&self, other: &Arc<T>) -> bool { *(*self) <= *(*other) }
|
||||
|
||||
/// Greater-than comparison for two `Arc<T>`s.
|
||||
///
|
||||
/// The two are compared by calling `>` on their inner values.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// use std::sync::Arc;
|
||||
///
|
||||
/// let five = Arc::new(5);
|
||||
///
|
||||
/// five > Arc::new(5);
|
||||
/// ```
|
||||
fn gt(&self, other: &Arc<T>) -> bool { *(*self) > *(*other) }
|
||||
|
||||
/// 'Greater-than or equal to' comparison for two `Arc<T>`s.
|
||||
///
|
||||
/// The two are compared by calling `>=` on their inner values.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// use std::sync::Arc;
|
||||
///
|
||||
/// let five = Arc::new(5);
|
||||
///
|
||||
/// five >= Arc::new(5);
|
||||
/// ```
|
||||
fn ge(&self, other: &Arc<T>) -> bool { *(*self) >= *(*other) }
|
||||
}
|
||||
#[stable(feature = "rust1", since = "1.0.0")]
|
||||
impl<T: Ord> Ord for Arc<T> {
|
||||
fn cmp(&self, other: &Arc<T>) -> Ordering { (**self).cmp(&**other) }
|
||||
}
|
||||
#[stable(feature = "rust1", since = "1.0.0")]
|
||||
impl<T: Eq> Eq for Arc<T> {}
|
||||
|
||||
#[stable(feature = "rust1", since = "1.0.0")]
|
||||
impl<T: fmt::Display> fmt::Display for Arc<T> {
|
||||
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
||||
fmt::Display::fmt(&**self, f)
|
||||
}
|
||||
}
|
||||
|
||||
#[stable(feature = "rust1", since = "1.0.0")]
|
||||
impl<T: fmt::Debug> fmt::Debug for Arc<T> {
|
||||
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
||||
fmt::Debug::fmt(&**self, f)
|
||||
}
|
||||
}
|
||||
|
||||
#[stable(feature = "rust1", since = "1.0.0")]
|
||||
impl<T> fmt::Pointer for Arc<T> {
|
||||
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
||||
fmt::Pointer::fmt(&*self._ptr, f)
|
||||
}
|
||||
}
|
||||
|
||||
#[stable(feature = "rust1", since = "1.0.0")]
|
||||
impl<T: Default> Default for Arc<T> {
|
||||
#[stable(feature = "rust1", since = "1.0.0")]
|
||||
fn default() -> Arc<T> { Arc::new(Default::default()) }
|
||||
}
|
||||
|
||||
#[stable(feature = "rust1", since = "1.0.0")]
|
||||
impl<T: Hash> Hash for Arc<T> {
|
||||
fn hash<H: Hasher>(&self, state: &mut H) {
|
||||
(**self).hash(state)
|
||||
}
|
||||
}
|
@ -112,7 +112,14 @@ pub mod boxed;
|
||||
mod boxed { pub use std::boxed::{Box, HEAP}; }
|
||||
#[cfg(test)]
|
||||
mod boxed_test;
|
||||
#[cfg(not(stage0))]
|
||||
pub mod arc;
|
||||
#[cfg(stage0)]
|
||||
mod arc_stage0;
|
||||
#[cfg(stage0)]
|
||||
pub mod arc {
|
||||
pub use arc_stage0::*;
|
||||
}
|
||||
pub mod rc;
|
||||
|
||||
/// Common out-of-memory routine
|
||||
|
Loading…
Reference in New Issue
Block a user