OpenE2K/rust
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Auto merge of #25458 - P1start:arc-dst, r=huonw

Browse Source
This commit is contained in:
bors 2015-05-17 01:41:52 +00:00
commit 4f83c4b851
3 changed files with 743 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

86
src/liballoc/arc.rs
View File

@ -77,11 +77,12 @@ 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::{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;
@ -118,15 +119,16 @@ 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`.
///
@ -135,30 +137,30 @@ unsafe impl<T: Sync + Send> Sync for Arc<T> { }
#[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>`.
@ -182,7 +184,9 @@ impl<T> 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
@ -204,7 +208,7 @@ impl<T> Arc<T> {
}
}
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
@ -222,11 +226,11 @@ impl<T> Arc<T> {
// 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))
}
}
}
@ -234,12 +238,12 @@ impl<T> Arc<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 }
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.
@ -264,7 +268,7 @@ pub fn strong_count<T>(this: &Arc<T>) -> usize { this.inner().strong.load(SeqCst
/// ```
#[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
@ -279,7 +283,7 @@ pub fn get_mut<T>(this: &mut Arc<T>) -> Option<&mut T> {
}
#[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.
@ -313,7 +317,7 @@ impl<T> Clone for Arc<T> {
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T> Deref for Arc<T> {
impl<T: ?Sized> Deref for Arc<T> {
type Target = T;
#[inline]
@ -356,7 +360,7 @@ impl<T: Clone> Arc<T> {
}
#[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
@ -390,7 +394,7 @@ impl<T> Drop for Arc<T> {
// 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
@ -424,7 +428,7 @@ impl<T> Drop for Arc<T> {
#[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.
@ -465,7 +469,7 @@ impl<T> Weak<T> {
#[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.
@ -489,7 +493,7 @@ impl<T> Clone for Weak<T> {
}
#[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.
@ -520,21 +524,22 @@ impl<T> Drop for Weak<T> {
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.
@ -566,7 +571,7 @@ impl<T: PartialEq> PartialEq for Arc<T> {
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.
@ -645,21 +650,21 @@ impl<T: PartialOrd> PartialOrd for Arc<T> {
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)
}
@ -679,7 +684,7 @@ impl<T: Default> Default for Arc<T> {
}
#[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)
}
@ -906,4 +911,13 @@ mod tests {
// 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());
}
}

686
src/liballoc/arc_stage0.rs Normal file
View File

@ -0,0 +1,686 @@
// 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)
}
}

7
src/liballoc/lib.rs
View File

@ -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