use core::atomic::Ordering::{Relaxed, Release, Acquire, SeqCst};
use core::fmt;
use core::cmp::Ordering;
-use core::mem::{min_align_of, size_of};
+use core::mem::{min_align_of_val, size_of_val};
+use core::intrinsics::drop_in_place;
use core::mem;
use core::nonzero::NonZero;
-use core::ops::Deref;
-use core::ptr;
+use core::ops::{Deref, CoerceUnsized};
+use core::marker::Unsize;
use core::hash::{Hash, Hasher};
use heap::deallocate;
/// ```
#[unsafe_no_drop_flag]
#[stable(feature = "rust1", since = "1.0.0")]
-pub struct Arc<T> {
+pub struct Arc<T: ?Sized> {
// FIXME #12808: strange name to try to avoid interfering with
// field accesses of the contained type via Deref
_ptr: NonZero<*mut ArcInner<T>>,
}
-unsafe impl<T: Sync + Send> Send for Arc<T> { }
-unsafe impl<T: Sync + Send> Sync for Arc<T> { }
+unsafe impl<T: ?Sized + Sync + Send> Send for Arc<T> { }
+unsafe impl<T: ?Sized + Sync + Send> Sync for Arc<T> { }
+impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Arc<U>> for Arc<T> {}
/// A weak pointer to an `Arc`.
///
#[unsafe_no_drop_flag]
#[unstable(feature = "alloc",
reason = "Weak pointers may not belong in this module.")]
-pub struct Weak<T> {
+pub struct Weak<T: ?Sized> {
// FIXME #12808: strange name to try to avoid interfering with
// 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> { }
+unsafe impl<T: ?Sized + Sync + Send> Send for Weak<T> { }
+unsafe impl<T: ?Sized + Sync + Send> Sync for Weak<T> { }
#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: fmt::Debug> fmt::Debug for Weak<T> {
+impl<T: ?Sized + fmt::Debug> fmt::Debug for Weak<T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "(Weak)")
}
}
-struct ArcInner<T> {
+struct ArcInner<T: ?Sized> {
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> {}
+unsafe impl<T: ?Sized + Sync + Send> Send for ArcInner<T> {}
+unsafe impl<T: ?Sized + Sync + Send> Sync for ArcInner<T> {}
impl<T> Arc<T> {
/// Constructs a new `Arc<T>`.
};
Arc { _ptr: unsafe { NonZero::new(mem::transmute(x)) } }
}
+}
+impl<T: ?Sized> Arc<T> {
/// Downgrades the `Arc<T>` to a `Weak<T>` reference.
///
/// # Examples
}
}
-impl<T> Arc<T> {
+impl<T: ?Sized> Arc<T> {
#[inline]
fn inner(&self) -> &ArcInner<T> {
// This unsafety is ok because while this arc is alive we're guaranteed
// 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));
+ drop_in_place(&mut (*ptr).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>>())
+ deallocate(ptr as *mut u8, size_of_val(&*ptr), min_align_of_val(&*ptr))
}
}
}
/// 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 }
+pub fn weak_count<T: ?Sized>(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) }
+pub fn strong_count<T: ?Sized>(this: &Arc<T>) -> usize { this.inner().strong.load(SeqCst) }
/// Returns a mutable reference to the contained value if the `Arc<T>` is unique.
/// ```
#[inline]
#[unstable(feature = "alloc")]
-pub fn get_mut<T>(this: &mut Arc<T>) -> Option<&mut T> {
+pub fn get_mut<T: ?Sized>(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
}
#[stable(feature = "rust1", since = "1.0.0")]
-impl<T> Clone for Arc<T> {
+impl<T: ?Sized> Clone for Arc<T> {
/// Makes a clone of the `Arc<T>`.
///
/// This increases the strong reference count.
}
#[stable(feature = "rust1", since = "1.0.0")]
-impl<T> Deref for Arc<T> {
+impl<T: ?Sized> Deref for Arc<T> {
type Target = T;
#[inline]
}
#[stable(feature = "rust1", since = "1.0.0")]
-impl<T> Drop for Arc<T> {
+impl<T: ?Sized> Drop for Arc<T> {
/// Drops the `Arc<T>`.
///
/// This will decrement the strong reference count. If the strong reference
// 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 }
+ if ptr as usize == 0 || 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
#[unstable(feature = "alloc",
reason = "Weak pointers may not belong in this module.")]
-impl<T> Weak<T> {
+impl<T: ?Sized> Weak<T> {
/// Upgrades a weak reference to a strong reference.
///
/// Upgrades the `Weak<T>` reference to an `Arc<T>`, if possible.
#[unstable(feature = "alloc",
reason = "Weak pointers may not belong in this module.")]
-impl<T> Clone for Weak<T> {
+impl<T: ?Sized> Clone for Weak<T> {
/// Makes a clone of the `Weak<T>`.
///
/// This increases the weak reference count.
}
#[stable(feature = "rust1", since = "1.0.0")]
-impl<T> Drop for Weak<T> {
+impl<T: ?Sized> Drop for Weak<T> {
/// Drops the `Weak<T>`.
///
/// This will decrement the weak reference count.
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 ptr as usize == 0 || 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>>()) }
+ unsafe { deallocate(ptr as *mut u8,
+ size_of_val(&*ptr),
+ min_align_of_val(&*ptr)) }
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: PartialEq> PartialEq for Arc<T> {
+impl<T: ?Sized + PartialEq> PartialEq for Arc<T> {
/// Equality for two `Arc<T>`s.
///
/// Two `Arc<T>`s are equal if their inner value are equal.
fn ne(&self, other: &Arc<T>) -> bool { *(*self) != *(*other) }
}
#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: PartialOrd> PartialOrd for Arc<T> {
+impl<T: ?Sized + PartialOrd> PartialOrd for Arc<T> {
/// Partial comparison for two `Arc<T>`s.
///
/// The two are compared by calling `partial_cmp()` on their inner values.
fn ge(&self, other: &Arc<T>) -> bool { *(*self) >= *(*other) }
}
#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: Ord> Ord for Arc<T> {
+impl<T: ?Sized + 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> {}
+impl<T: ?Sized + Eq> Eq for Arc<T> {}
#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: fmt::Display> fmt::Display for Arc<T> {
+impl<T: ?Sized + 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> {
+impl<T: ?Sized + 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: Hash> Hash for Arc<T> {
+impl<T: ?Sized + Hash> Hash for Arc<T> {
fn hash<H: Hasher>(&self, state: &mut H) {
(**self).hash(state)
}
// Make sure deriving works with Arc<T>
#[derive(Eq, Ord, PartialEq, PartialOrd, Clone, Debug, Default)]
struct Foo { inner: Arc<i32> }
+
+ #[test]
+ fn test_unsized() {
+ let x: Arc<[i32]> = Arc::new([1, 2, 3]);
+ assert_eq!(format!("{:?}", x), "[1, 2, 3]");
+ let y = x.clone().downgrade();
+ drop(x);
+ assert!(y.upgrade().is_none());
+ }
}
--- /dev/null
+// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+//! Threadsafe reference-counted boxes (the `Arc<T>` type).
+//!
+//! The `Arc<T>` type provides shared ownership of an immutable value.
+//! Destruction is deterministic, and will occur as soon as the last owner is
+//! gone. It is marked as `Send` because it uses atomic reference counting.
+//!
+//! If you do not need thread-safety, and just need shared ownership, consider
+//! the [`Rc<T>` type](../rc/struct.Rc.html). It is the same as `Arc<T>`, but
+//! does not use atomics, making it both thread-unsafe as well as significantly
+//! faster when updating the reference count.
+//!
+//! The `downgrade` method can be used to create a non-owning `Weak<T>` pointer
+//! to the box. A `Weak<T>` pointer can be upgraded to an `Arc<T>` pointer, but
+//! will return `None` if the value has already been dropped.
+//!
+//! For example, a tree with parent pointers can be represented by putting the
+//! nodes behind strong `Arc<T>` pointers, and then storing the parent pointers
+//! as `Weak<T>` pointers.
+//!
+//! # Examples
+//!
+//! Sharing some immutable data between threads:
+//!
+//! ```no_run
+//! use std::sync::Arc;
+//! use std::thread;
+//!
+//! let five = Arc::new(5);
+//!
+//! for _ in 0..10 {
+//! let five = five.clone();
+//!
+//! thread::spawn(move || {
+//! println!("{:?}", five);
+//! });
+//! }
+//! ```
+//!
+//! Sharing mutable data safely between threads with a `Mutex`:
+//!
+//! ```no_run
+//! use std::sync::{Arc, Mutex};
+//! use std::thread;
+//!
+//! let five = Arc::new(Mutex::new(5));
+//!
+//! for _ in 0..10 {
+//! let five = five.clone();
+//!
+//! thread::spawn(move || {
+//! let mut number = five.lock().unwrap();
+//!
+//! *number += 1;
+//!
+//! println!("{}", *number); // prints 6
+//! });
+//! }
+//! ```
+
+use boxed::Box;
+
+use core::prelude::*;
+
+use core::atomic;
+use core::atomic::Ordering::{Relaxed, Release, Acquire, SeqCst};
+use core::fmt;
+use core::cmp::Ordering;
+use core::mem::{min_align_of, size_of};
+use core::mem;
+use core::nonzero::NonZero;
+use core::ops::Deref;
+use core::ptr;
+use core::hash::{Hash, Hasher};
+use heap::deallocate;
+
+/// An atomically reference counted wrapper for shared state.
+///
+/// # Examples
+///
+/// In this example, a large vector of floats is shared between several threads.
+/// With simple pipes, without `Arc`, a copy would have to be made for each
+/// thread.
+///
+/// When you clone an `Arc<T>`, it will create another pointer to the data and
+/// increase the reference counter.
+///
+/// ```
+/// # #![feature(alloc, core)]
+/// use std::sync::Arc;
+/// use std::thread;
+///
+/// fn main() {
+/// let numbers: Vec<_> = (0..100u32).collect();
+/// let shared_numbers = Arc::new(numbers);
+///
+/// for _ in 0..10 {
+/// let child_numbers = shared_numbers.clone();
+///
+/// thread::spawn(move || {
+/// let local_numbers = &child_numbers[..];
+///
+/// // Work with the local numbers
+/// });
+/// }
+/// }
+/// ```
+#[unsafe_no_drop_flag]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct Arc<T> {
+ // FIXME #12808: strange name to try to avoid interfering with
+ // field accesses of the contained type via Deref
+ _ptr: NonZero<*mut ArcInner<T>>,
+}
+
+unsafe impl<T: Sync + Send> Send for Arc<T> { }
+unsafe impl<T: Sync + Send> Sync for Arc<T> { }
+
+
+/// A weak pointer to an `Arc`.
+///
+/// Weak pointers will not keep the data inside of the `Arc` alive, and can be
+/// used to break cycles between `Arc` pointers.
+#[unsafe_no_drop_flag]
+#[unstable(feature = "alloc",
+ reason = "Weak pointers may not belong in this module.")]
+pub struct Weak<T> {
+ // FIXME #12808: strange name to try to avoid interfering with
+ // 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)
+ }
+}
projects / rust.git / commitdiff