// option. This file may not be copied, modified, or distributed
// except according to those terms.
-//! Thread-local reference-counted boxes (the `Rc<T>` type).
+#![allow(deprecated)]
+
+//! Single-threaded reference-counting pointers. 'Rc' stands for 'Reference
+//! Counted'.
+//!
+//! The type [`Rc<T>`][`Rc`] provides shared ownership of a value of type `T`,
+//! allocated in the heap. Invoking [`clone`][clone] on [`Rc`] produces a new
+//! pointer to the same value in the heap. When the last [`Rc`] pointer to a
+//! given value is destroyed, the pointed-to value is also destroyed.
+//!
+//! Shared references in Rust disallow mutation by default, and [`Rc`]
+//! is no exception: you cannot generally obtain a mutable reference to
+//! something inside an [`Rc`]. If you need mutability, put a [`Cell`]
+//! or [`RefCell`] inside the [`Rc`]; see [an example of mutability
+//! inside an Rc][mutability].
+//!
+//! [`Rc`] uses non-atomic reference counting. This means that overhead is very
+//! low, but an [`Rc`] cannot be sent between threads, and consequently [`Rc`]
+//! does not implement [`Send`][send]. As a result, the Rust compiler
+//! will check *at compile time* that you are not sending [`Rc`]s between
+//! threads. If you need multi-threaded, atomic reference counting, use
+//! [`sync::Arc`][arc].
+//!
+//! The [`downgrade`][downgrade] method can be used to create a non-owning
+//! [`Weak`] pointer. A [`Weak`] pointer can be [`upgrade`][upgrade]d
+//! to an [`Rc`], but this will return [`None`] if the value has
+//! already been dropped.
+//!
+//! A cycle between [`Rc`] pointers will never be deallocated. For this reason,
+//! [`Weak`] is used to break cycles. For example, a tree could have strong
+//! [`Rc`] pointers from parent nodes to children, and [`Weak`] pointers from
+//! children back to their parents.
+//!
+//! `Rc<T>` automatically dereferences to `T` (via the [`Deref`] trait),
+//! so you can call `T`'s methods on a value of type [`Rc<T>`][`Rc`]. To avoid name
+//! clashes with `T`'s methods, the methods of [`Rc<T>`][`Rc`] itself are [associated
+//! functions][assoc], called using function-like syntax:
+//!
+//! ```
+//! use std::rc::Rc;
+//! let my_rc = Rc::new(());
+//!
+//! Rc::downgrade(&my_rc);
+//! ```
//!
-//! The `Rc<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 non-sendable because it avoids the overhead of atomic
-//! reference counting.
+//! [`Weak<T>`][`Weak`] does not auto-dereference to `T`, because the value may have
+//! already been destroyed.
//!
-//! 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 `Rc<T>` pointer, but
-//! will return `None` if the value has already been dropped.
+//! # Cloning references
//!
-//! For example, a tree with parent pointers can be represented by putting the
-//! nodes behind strong `Rc<T>` pointers, and then storing the parent pointers
-//! as `Weak<T>` pointers.
+//! Creating a new reference from an existing reference counted pointer is done using the
+//! `Clone` trait implemented for [`Rc<T>`][`Rc`] and [`Weak<T>`][`Weak`].
+//!
+//! ```
+//! use std::rc::Rc;
+//! let foo = Rc::new(vec![1.0, 2.0, 3.0]);
+//! // The two syntaxes below are equivalent.
+//! let a = foo.clone();
+//! let b = Rc::clone(&foo);
+//! // a and b both point to the same memory location as foo.
+//! ```
+//!
+//! The `Rc::clone(&from)` syntax is the most idiomatic because it conveys more explicitly
+//! the meaning of the code. In the example above, this syntax makes it easier to see that
+//! this code is creating a new reference rather than copying the whole content of foo.
//!
//! # Examples
//!
//! Consider a scenario where a set of `Gadget`s are owned by a given `Owner`.
//! We want to have our `Gadget`s point to their `Owner`. We can't do this with
//! unique ownership, because more than one gadget may belong to the same
-//! `Owner`. `Rc<T>` allows us to share an `Owner` between multiple `Gadget`s,
+//! `Owner`. [`Rc`] allows us to share an `Owner` between multiple `Gadget`s,
//! and have the `Owner` remain allocated as long as any `Gadget` points at it.
//!
-//! ```rust
+//! ```
//! use std::rc::Rc;
//!
//! struct Owner {
-//! name: String
+//! name: String,
//! // ...other fields
//! }
//!
//! struct Gadget {
//! id: i32,
-//! owner: Rc<Owner>
+//! owner: Rc<Owner>,
//! // ...other fields
//! }
//!
//! fn main() {
-//! // Create a reference counted Owner.
-//! let gadget_owner : Rc<Owner> = Rc::new(
-//! Owner { name: String::from("Gadget Man") }
+//! // Create a reference-counted `Owner`.
+//! let gadget_owner: Rc<Owner> = Rc::new(
+//! Owner {
+//! name: "Gadget Man".to_string(),
+//! }
//! );
//!
-//! // Create Gadgets belonging to gadget_owner. To increment the reference
-//! // count we clone the `Rc<T>` object.
-//! let gadget1 = Gadget { id: 1, owner: gadget_owner.clone() };
-//! let gadget2 = Gadget { id: 2, owner: gadget_owner.clone() };
+//! // Create `Gadget`s belonging to `gadget_owner`. Cloning the `Rc<Owner>`
+//! // value gives us a new pointer to the same `Owner` value, incrementing
+//! // the reference count in the process.
+//! let gadget1 = Gadget {
+//! id: 1,
+//! owner: Rc::clone(&gadget_owner),
+//! };
+//! let gadget2 = Gadget {
+//! id: 2,
+//! owner: Rc::clone(&gadget_owner),
+//! };
//!
+//! // Dispose of our local variable `gadget_owner`.
//! drop(gadget_owner);
//!
-//! // Despite dropping gadget_owner, we're still able to print out the name
-//! // of the Owner of the Gadgets. This is because we've only dropped the
-//! // reference count object, not the Owner it wraps. As long as there are
-//! // other `Rc<T>` objects pointing at the same Owner, it will remain
-//! // allocated. Notice that the `Rc<T>` wrapper around Gadget.owner gets
-//! // automatically dereferenced for us.
+//! // Despite dropping `gadget_owner`, we're still able to print out the name
+//! // of the `Owner` of the `Gadget`s. This is because we've only dropped a
+//! // single `Rc<Owner>`, not the `Owner` it points to. As long as there are
+//! // other `Rc<Owner>` values pointing at the same `Owner`, it will remain
+//! // allocated. The field projection `gadget1.owner.name` works because
+//! // `Rc<Owner>` automatically dereferences to `Owner`.
//! println!("Gadget {} owned by {}", gadget1.id, gadget1.owner.name);
//! println!("Gadget {} owned by {}", gadget2.id, gadget2.owner.name);
//!
-//! // At the end of the method, gadget1 and gadget2 get destroyed, and with
-//! // them the last counted references to our Owner. Gadget Man now gets
-//! // destroyed as well.
+//! // At the end of the function, `gadget1` and `gadget2` are destroyed, and
+//! // with them the last counted references to our `Owner`. Gadget Man now
+//! // gets destroyed as well.
//! }
//! ```
//!
//! If our requirements change, and we also need to be able to traverse from
-//! Owner → Gadget, we will run into problems: an `Rc<T>` pointer from Owner
-//! → Gadget introduces a cycle between the objects. This means that their
-//! reference counts can never reach 0, and the objects will remain allocated: a
-//! memory leak. In order to get around this, we can use `Weak<T>` pointers.
-//! These pointers don't contribute to the total count.
+//! `Owner` to `Gadget`, we will run into problems. An [`Rc`] pointer from `Owner`
+//! to `Gadget` introduces a cycle between the values. This means that their
+//! reference counts can never reach 0, and the values will remain allocated
+//! forever: a memory leak. In order to get around this, we can use [`Weak`]
+//! pointers.
//!
//! Rust actually makes it somewhat difficult to produce this loop in the first
-//! place: in order to end up with two objects that point at each other, one of
-//! them needs to be mutable. This is problematic because `Rc<T>` enforces
-//! memory safety by only giving out shared references to the object it wraps,
+//! place. In order to end up with two values that point at each other, one of
+//! them needs to be mutable. This is difficult because [`Rc`] enforces
+//! memory safety by only giving out shared references to the value it wraps,
//! and these don't allow direct mutation. We need to wrap the part of the
-//! object we wish to mutate in a `RefCell`, which provides *interior
+//! value we wish to mutate in a [`RefCell`], which provides *interior
//! mutability*: a method to achieve mutability through a shared reference.
-//! `RefCell` enforces Rust's borrowing rules at runtime. Read the `Cell`
-//! documentation for more details on interior mutability.
+//! [`RefCell`] enforces Rust's borrowing rules at runtime.
//!
-//! ```rust
-//! # #![feature(rc_weak)]
+//! ```
//! use std::rc::Rc;
//! use std::rc::Weak;
//! use std::cell::RefCell;
//!
//! struct Owner {
//! name: String,
-//! gadgets: RefCell<Vec<Weak<Gadget>>>
+//! gadgets: RefCell<Vec<Weak<Gadget>>>,
//! // ...other fields
//! }
//!
//! struct Gadget {
//! id: i32,
-//! owner: Rc<Owner>
+//! owner: Rc<Owner>,
//! // ...other fields
//! }
//!
//! fn main() {
-//! // Create a reference counted Owner. Note the fact that we've put the
-//! // Owner's vector of Gadgets inside a RefCell so that we can mutate it
-//! // through a shared reference.
-//! let gadget_owner : Rc<Owner> = Rc::new(
-//! Owner {
-//! name: "Gadget Man".to_string(),
-//! gadgets: RefCell::new(Vec::new())
-//! }
+//! // Create a reference-counted `Owner`. Note that we've put the `Owner`'s
+//! // vector of `Gadget`s inside a `RefCell` so that we can mutate it through
+//! // a shared reference.
+//! let gadget_owner: Rc<Owner> = Rc::new(
+//! Owner {
+//! name: "Gadget Man".to_string(),
+//! gadgets: RefCell::new(vec![]),
+//! }
+//! );
+//!
+//! // Create `Gadget`s belonging to `gadget_owner`, as before.
+//! let gadget1 = Rc::new(
+//! Gadget {
+//! id: 1,
+//! owner: Rc::clone(&gadget_owner),
+//! }
+//! );
+//! let gadget2 = Rc::new(
+//! Gadget {
+//! id: 2,
+//! owner: Rc::clone(&gadget_owner),
+//! }
//! );
//!
-//! // Create Gadgets belonging to gadget_owner as before.
-//! let gadget1 = Rc::new(Gadget{id: 1, owner: gadget_owner.clone()});
-//! let gadget2 = Rc::new(Gadget{id: 2, owner: gadget_owner.clone()});
+//! // Add the `Gadget`s to their `Owner`.
+//! {
+//! let mut gadgets = gadget_owner.gadgets.borrow_mut();
+//! gadgets.push(Rc::downgrade(&gadget1));
+//! gadgets.push(Rc::downgrade(&gadget2));
+//!
+//! // `RefCell` dynamic borrow ends here.
+//! }
//!
-//! // Add the Gadgets to their Owner. To do this we mutably borrow from
-//! // the RefCell holding the Owner's Gadgets.
-//! gadget_owner.gadgets.borrow_mut().push(gadget1.clone().downgrade());
-//! gadget_owner.gadgets.borrow_mut().push(gadget2.clone().downgrade());
+//! // Iterate over our `Gadget`s, printing their details out.
+//! for gadget_weak in gadget_owner.gadgets.borrow().iter() {
//!
-//! // Iterate over our Gadgets, printing their details out
-//! for gadget_opt in gadget_owner.gadgets.borrow().iter() {
+//! // `gadget_weak` is a `Weak<Gadget>`. Since `Weak` pointers can't
+//! // guarantee the value is still allocated, we need to call
+//! // `upgrade`, which returns an `Option<Rc<Gadget>>`.
+//! //
+//! // In this case we know the value still exists, so we simply
+//! // `unwrap` the `Option`. In a more complicated program, you might
+//! // need graceful error handling for a `None` result.
//!
-//! // gadget_opt is a Weak<Gadget>. Since weak pointers can't guarantee
-//! // that their object is still allocated, we need to call upgrade()
-//! // on them to turn them into a strong reference. This returns an
-//! // Option, which contains a reference to our object if it still
-//! // exists.
-//! let gadget = gadget_opt.upgrade().unwrap();
+//! let gadget = gadget_weak.upgrade().unwrap();
//! println!("Gadget {} owned by {}", gadget.id, gadget.owner.name);
//! }
//!
-//! // At the end of the method, gadget_owner, gadget1 and gadget2 get
-//! // destroyed. There are now no strong (`Rc<T>`) references to the gadgets.
-//! // Once they get destroyed, the Gadgets get destroyed. This zeroes the
-//! // reference count on Gadget Man, they get destroyed as well.
+//! // At the end of the function, `gadget_owner`, `gadget1`, and `gadget2`
+//! // are destroyed. There are now no strong (`Rc`) pointers to the
+//! // gadgets, so they are destroyed. This zeroes the reference count on
+//! // Gadget Man, so he gets destroyed as well.
//! }
//! ```
+//!
+//! [`Rc`]: struct.Rc.html
+//! [`Weak`]: struct.Weak.html
+//! [clone]: ../../std/clone/trait.Clone.html#tymethod.clone
+//! [`Cell`]: ../../std/cell/struct.Cell.html
+//! [`RefCell`]: ../../std/cell/struct.RefCell.html
+//! [send]: ../../std/marker/trait.Send.html
+//! [arc]: ../../std/sync/struct.Arc.html
+//! [`Deref`]: ../../std/ops/trait.Deref.html
+//! [downgrade]: struct.Rc.html#method.downgrade
+//! [upgrade]: struct.Weak.html#method.upgrade
+//! [`None`]: ../../std/option/enum.Option.html#variant.None
+//! [assoc]: ../../book/first-edition/method-syntax.html#associated-functions
+//! [mutability]: ../../std/cell/index.html#introducing-mutability-inside-of-something-immutable
#![stable(feature = "rust1", since = "1.0.0")]
-use core::prelude::*;
-
#[cfg(not(test))]
use boxed::Box;
#[cfg(test)]
use std::boxed::Box;
+use core::any::Any;
+use core::borrow;
use core::cell::Cell;
use core::cmp::Ordering;
use core::fmt;
-use core::hash::{Hasher, Hash};
-use core::intrinsics::{assume, drop_in_place};
-use core::marker::{self, Unsize};
-use core::mem::{self, align_of, size_of, align_of_val, size_of_val, forget};
-use core::nonzero::NonZero;
-use core::ops::{CoerceUnsized, Deref};
-use core::ptr;
-
-use heap::deallocate;
+use core::hash::{Hash, Hasher};
+use core::intrinsics::abort;
+use core::marker;
+use core::marker::{Unsize, PhantomData};
+use core::mem::{self, align_of_val, forget, size_of_val, uninitialized};
+use core::ops::Deref;
+use core::ops::CoerceUnsized;
+use core::ptr::{self, NonNull};
+use core::convert::From;
+
+use heap::{Heap, Alloc, Layout, box_free};
+use string::String;
+use vec::Vec;
struct RcBox<T: ?Sized> {
strong: Cell<usize>,
value: T,
}
-
-/// A reference-counted pointer type over an immutable value.
+/// A single-threaded reference-counting pointer. 'Rc' stands for 'Reference
+/// Counted'.
+///
+/// See the [module-level documentation](./index.html) for more details.
///
-/// See the [module level documentation](./index.html) for more details.
-#[unsafe_no_drop_flag]
+/// The inherent methods of `Rc` are all associated functions, which means
+/// that you have to call them as e.g. [`Rc::get_mut(&mut value)`][get_mut] instead of
+/// `value.get_mut()`. This avoids conflicts with methods of the inner
+/// type `T`.
+///
+/// [get_mut]: #method.get_mut
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Rc<T: ?Sized> {
- // FIXME #12808: strange names to try to avoid interfering with field
- // accesses of the contained type via Deref
- _ptr: NonZero<*mut RcBox<T>>,
+ ptr: NonNull<RcBox<T>>,
+ phantom: PhantomData<T>,
}
+#[stable(feature = "rust1", since = "1.0.0")]
impl<T: ?Sized> !marker::Send for Rc<T> {}
+#[stable(feature = "rust1", since = "1.0.0")]
impl<T: ?Sized> !marker::Sync for Rc<T> {}
-impl<T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<Rc<U>> for Rc<T> {}
+#[unstable(feature = "coerce_unsized", issue = "27732")]
+impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Rc<U>> for Rc<T> {}
impl<T> Rc<T> {
/// Constructs a new `Rc<T>`.
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn new(value: T) -> Rc<T> {
- unsafe {
- Rc {
- // there is an implicit weak pointer owned by all the strong
- // pointers, which ensures that the weak destructor never frees
- // the allocation while the strong destructor is running, even
- // if the weak pointer is stored inside the strong one.
- _ptr: NonZero::new(Box::into_raw(box RcBox {
- strong: Cell::new(1),
- weak: Cell::new(1),
- value: value
- })),
- }
+ Rc {
+ // there is an implicit weak pointer owned by all the strong
+ // pointers, which ensures that the weak destructor never frees
+ // the allocation while the strong destructor is running, even
+ // if the weak pointer is stored inside the strong one.
+ ptr: Box::into_raw_non_null(box RcBox {
+ strong: Cell::new(1),
+ weak: Cell::new(1),
+ value,
+ }),
+ phantom: PhantomData,
}
}
- /// Unwraps the contained value if the `Rc<T>` is unique.
+ /// Returns the contained value, if the `Rc` has exactly one strong reference.
///
- /// If the `Rc<T>` is not unique, an `Err` is returned with the same
- /// `Rc<T>`.
+ /// Otherwise, an [`Err`][result] is returned with the same `Rc` that was
+ /// passed in.
+ ///
+ /// This will succeed even if there are outstanding weak references.
+ ///
+ /// [result]: ../../std/result/enum.Result.html
///
/// # Examples
///
/// ```
- /// # #![feature(rc_unique)]
/// use std::rc::Rc;
///
/// let x = Rc::new(3);
/// assert_eq!(Rc::try_unwrap(x), Ok(3));
///
/// let x = Rc::new(4);
- /// let _y = x.clone();
- /// assert_eq!(Rc::try_unwrap(x), Err(Rc::new(4)));
+ /// let _y = Rc::clone(&x);
+ /// assert_eq!(*Rc::try_unwrap(x).unwrap_err(), 4);
/// ```
#[inline]
- #[unstable(feature = "rc_unique")]
- pub fn try_unwrap(rc: Rc<T>) -> Result<T, Rc<T>> {
- if Rc::is_unique(&rc) {
+ #[stable(feature = "rc_unique", since = "1.4.0")]
+ pub fn try_unwrap(this: Self) -> Result<T, Self> {
+ if Rc::strong_count(&this) == 1 {
unsafe {
- let val = ptr::read(&*rc); // copy the contained object
- // destruct the box and skip our Drop
- // we can ignore the refcounts because we know we're unique
- deallocate(*rc._ptr as *mut u8, size_of::<RcBox<T>>(),
- align_of::<RcBox<T>>());
- forget(rc);
+ let val = ptr::read(&*this); // copy the contained object
+
+ // Indicate to Weaks that they can't be promoted by decrementing
+ // the strong count, and then remove the implicit "strong weak"
+ // pointer while also handling drop logic by just crafting a
+ // fake Weak.
+ this.dec_strong();
+ let _weak = Weak { ptr: this.ptr };
+ forget(this);
Ok(val)
}
} else {
- Err(rc)
+ Err(this)
}
}
}
impl<T: ?Sized> Rc<T> {
- /// Downgrades the `Rc<T>` to a `Weak<T>` reference.
+ /// Consumes the `Rc`, returning the wrapped pointer.
+ ///
+ /// To avoid a memory leak the pointer must be converted back to an `Rc` using
+ /// [`Rc::from_raw`][from_raw].
+ ///
+ /// [from_raw]: struct.Rc.html#method.from_raw
///
/// # Examples
///
/// ```
- /// # #![feature(rc_weak)]
/// use std::rc::Rc;
///
- /// let five = Rc::new(5);
+ /// let x = Rc::new(10);
+ /// let x_ptr = Rc::into_raw(x);
+ /// assert_eq!(unsafe { *x_ptr }, 10);
+ /// ```
+ #[stable(feature = "rc_raw", since = "1.17.0")]
+ pub fn into_raw(this: Self) -> *const T {
+ let ptr: *const T = &*this;
+ mem::forget(this);
+ ptr
+ }
+
+ /// Constructs an `Rc` from a raw pointer.
+ ///
+ /// The raw pointer must have been previously returned by a call to a
+ /// [`Rc::into_raw`][into_raw].
+ ///
+ /// This function is unsafe because improper use may lead to memory problems. For example, a
+ /// double-free may occur if the function is called twice on the same raw pointer.
+ ///
+ /// [into_raw]: struct.Rc.html#method.into_raw
+ ///
+ /// # Examples
///
- /// let weak_five = five.downgrade();
/// ```
- #[unstable(feature = "rc_weak",
- reason = "Weak pointers may not belong in this module")]
- pub fn downgrade(&self) -> Weak<T> {
- self.inc_weak();
- Weak { _ptr: self._ptr }
+ /// use std::rc::Rc;
+ ///
+ /// let x = Rc::new(10);
+ /// let x_ptr = Rc::into_raw(x);
+ ///
+ /// unsafe {
+ /// // Convert back to an `Rc` to prevent leak.
+ /// let x = Rc::from_raw(x_ptr);
+ /// assert_eq!(*x, 10);
+ ///
+ /// // Further calls to `Rc::from_raw(x_ptr)` would be memory unsafe.
+ /// }
+ ///
+ /// // The memory was freed when `x` went out of scope above, so `x_ptr` is now dangling!
+ /// ```
+ #[stable(feature = "rc_raw", since = "1.17.0")]
+ pub unsafe fn from_raw(ptr: *const T) -> Self {
+ // Align the unsized value to the end of the RcBox.
+ // Because it is ?Sized, it will always be the last field in memory.
+ let align = align_of_val(&*ptr);
+ let layout = Layout::new::<RcBox<()>>();
+ let offset = (layout.size() + layout.padding_needed_for(align)) as isize;
+
+ // Reverse the offset to find the original RcBox.
+ let fake_ptr = ptr as *mut RcBox<T>;
+ let rc_ptr = set_data_ptr(fake_ptr, (ptr as *mut u8).offset(-offset));
+
+ Rc {
+ ptr: NonNull::new_unchecked(rc_ptr),
+ phantom: PhantomData,
+ }
}
- /// Get the number of weak references to this value.
- #[inline]
- #[unstable(feature = "rc_counts")]
- pub fn weak_count(this: &Rc<T>) -> usize { this.weak() - 1 }
+ /// Creates a new [`Weak`][weak] pointer to this value.
+ ///
+ /// [weak]: struct.Weak.html
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let five = Rc::new(5);
+ ///
+ /// let weak_five = Rc::downgrade(&five);
+ /// ```
+ #[stable(feature = "rc_weak", since = "1.4.0")]
+ pub fn downgrade(this: &Self) -> Weak<T> {
+ this.inc_weak();
+ Weak { ptr: this.ptr }
+ }
- /// Get the number of strong references to this value.
+ /// Gets the number of [`Weak`][weak] pointers to this value.
+ ///
+ /// [weak]: struct.Weak.html
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let five = Rc::new(5);
+ /// let _weak_five = Rc::downgrade(&five);
+ ///
+ /// assert_eq!(1, Rc::weak_count(&five));
+ /// ```
#[inline]
- #[unstable(feature = "rc_counts")]
- pub fn strong_count(this: &Rc<T>) -> usize { this.strong() }
+ #[stable(feature = "rc_counts", since = "1.15.0")]
+ pub fn weak_count(this: &Self) -> usize {
+ this.weak() - 1
+ }
- /// Returns true if there are no other `Rc` or `Weak<T>` values that share
- /// the same inner value.
+ /// Gets the number of strong (`Rc`) pointers to this value.
///
/// # Examples
///
/// ```
- /// # #![feature(rc_unique)]
/// use std::rc::Rc;
///
/// let five = Rc::new(5);
+ /// let _also_five = Rc::clone(&five);
///
- /// assert!(Rc::is_unique(&five));
+ /// assert_eq!(2, Rc::strong_count(&five));
/// ```
#[inline]
- #[unstable(feature = "rc_unique")]
- pub fn is_unique(rc: &Rc<T>) -> bool {
- Rc::weak_count(rc) == 0 && Rc::strong_count(rc) == 1
+ #[stable(feature = "rc_counts", since = "1.15.0")]
+ pub fn strong_count(this: &Self) -> usize {
+ this.strong()
+ }
+
+ /// Returns true if there are no other `Rc` or [`Weak`][weak] pointers to
+ /// this inner value.
+ ///
+ /// [weak]: struct.Weak.html
+ #[inline]
+ fn is_unique(this: &Self) -> bool {
+ Rc::weak_count(this) == 0 && Rc::strong_count(this) == 1
}
- /// Returns a mutable reference to the contained value if the `Rc<T>` is
- /// unique.
+ /// Returns a mutable reference to the inner value, if there are
+ /// no other `Rc` or [`Weak`][weak] pointers to the same value.
+ ///
+ /// Returns [`None`] otherwise, because it is not safe to
+ /// mutate a shared value.
+ ///
+ /// See also [`make_mut`][make_mut], which will [`clone`][clone]
+ /// the inner value when it's shared.
///
- /// Returns `None` if the `Rc<T>` is not unique.
+ /// [weak]: struct.Weak.html
+ /// [`None`]: ../../std/option/enum.Option.html#variant.None
+ /// [make_mut]: struct.Rc.html#method.make_mut
+ /// [clone]: ../../std/clone/trait.Clone.html#tymethod.clone
///
/// # Examples
///
/// ```
- /// # #![feature(rc_unique)]
/// use std::rc::Rc;
///
/// let mut x = Rc::new(3);
/// *Rc::get_mut(&mut x).unwrap() = 4;
/// assert_eq!(*x, 4);
///
- /// let _y = x.clone();
+ /// let _y = Rc::clone(&x);
/// assert!(Rc::get_mut(&mut x).is_none());
/// ```
#[inline]
- #[unstable(feature = "rc_unique")]
- pub fn get_mut(rc: &mut Rc<T>) -> Option<&mut T> {
- if Rc::is_unique(rc) {
- let inner = unsafe { &mut **rc._ptr };
- Some(&mut inner.value)
+ #[stable(feature = "rc_unique", since = "1.4.0")]
+ pub fn get_mut(this: &mut Self) -> Option<&mut T> {
+ if Rc::is_unique(this) {
+ unsafe {
+ Some(&mut this.ptr.as_mut().value)
+ }
} else {
None
}
}
-}
-/// Get the number of weak references to this value.
-#[inline]
-#[unstable(feature = "rc_counts")]
-#[deprecated(since = "1.2.0", reason = "renamed to Rc::weak_count")]
-pub fn weak_count<T: ?Sized>(this: &Rc<T>) -> usize { Rc::weak_count(this) }
-
-/// Get the number of strong references to this value.
-#[inline]
-#[unstable(feature = "rc_counts")]
-#[deprecated(since = "1.2.0", reason = "renamed to Rc::strong_count")]
-pub fn strong_count<T: ?Sized>(this: &Rc<T>) -> usize { Rc::strong_count(this) }
-
-/// Returns true if there are no other `Rc` or `Weak<T>` values that share the
-/// same inner value.
-///
-/// # Examples
-///
-/// ```
-/// # #![feature(rc_unique)]
-/// use std::rc;
-/// use std::rc::Rc;
-///
-/// let five = Rc::new(5);
-///
-/// rc::is_unique(&five);
-/// ```
-#[inline]
-#[unstable(feature = "rc_unique")]
-#[deprecated(since = "1.2.0", reason = "renamed to Rc::is_unique")]
-pub fn is_unique<T>(rc: &Rc<T>) -> bool { Rc::is_unique(rc) }
-
-/// Unwraps the contained value if the `Rc<T>` is unique.
-///
-/// If the `Rc<T>` is not unique, an `Err` is returned with the same `Rc<T>`.
-///
-/// # Examples
-///
-/// ```
-/// # #![feature(rc_unique)]
-/// use std::rc::{self, Rc};
-///
-/// let x = Rc::new(3);
-/// assert_eq!(rc::try_unwrap(x), Ok(3));
-///
-/// let x = Rc::new(4);
-/// let _y = x.clone();
-/// assert_eq!(rc::try_unwrap(x), Err(Rc::new(4)));
-/// ```
-#[inline]
-#[unstable(feature = "rc_unique")]
-#[deprecated(since = "1.2.0", reason = "renamed to Rc::try_unwrap")]
-pub fn try_unwrap<T>(rc: Rc<T>) -> Result<T, Rc<T>> { Rc::try_unwrap(rc) }
-
-/// Returns a mutable reference to the contained value if the `Rc<T>` is unique.
-///
-/// Returns `None` if the `Rc<T>` is not unique.
-///
-/// # Examples
-///
-/// ```
-/// # #![feature(rc_unique)]
-/// use std::rc::{self, Rc};
-///
-/// let mut x = Rc::new(3);
-/// *rc::get_mut(&mut x).unwrap() = 4;
-/// assert_eq!(*x, 4);
-///
-/// let _y = x.clone();
-/// assert!(rc::get_mut(&mut x).is_none());
-/// ```
-#[inline]
-#[unstable(feature = "rc_unique")]
-#[deprecated(since = "1.2.0", reason = "renamed to Rc::get_mut")]
-pub fn get_mut<T>(rc: &mut Rc<T>) -> Option<&mut T> { Rc::get_mut(rc) }
+ #[inline]
+ #[stable(feature = "ptr_eq", since = "1.17.0")]
+ /// Returns true if the two `Rc`s point to the same value (not
+ /// just values that compare as equal).
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Rc;
+ ///
+ /// let five = Rc::new(5);
+ /// let same_five = Rc::clone(&five);
+ /// let other_five = Rc::new(5);
+ ///
+ /// assert!(Rc::ptr_eq(&five, &same_five));
+ /// assert!(!Rc::ptr_eq(&five, &other_five));
+ /// ```
+ pub fn ptr_eq(this: &Self, other: &Self) -> bool {
+ this.ptr.as_ptr() == other.ptr.as_ptr()
+ }
+}
impl<T: Clone> Rc<T> {
- /// Make a mutable reference from the given `Rc<T>`.
+ /// Makes a mutable reference into the given `Rc`.
+ ///
+ /// If there are other `Rc` or [`Weak`][weak] pointers to the same value,
+ /// then `make_mut` will invoke [`clone`][clone] on the inner value to
+ /// ensure unique ownership. This is also referred to as clone-on-write.
+ ///
+ /// See also [`get_mut`][get_mut], which will fail rather than cloning.
///
- /// 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.
+ /// [weak]: struct.Weak.html
+ /// [clone]: ../../std/clone/trait.Clone.html#tymethod.clone
+ /// [get_mut]: struct.Rc.html#method.get_mut
///
/// # Examples
///
/// ```
- /// # #![feature(rc_unique)]
/// use std::rc::Rc;
///
- /// let mut five = Rc::new(5);
+ /// let mut data = Rc::new(5);
///
- /// let mut_five = five.make_unique();
+ /// *Rc::make_mut(&mut data) += 1; // Won't clone anything
+ /// let mut other_data = Rc::clone(&data); // Won't clone inner data
+ /// *Rc::make_mut(&mut data) += 1; // Clones inner data
+ /// *Rc::make_mut(&mut data) += 1; // Won't clone anything
+ /// *Rc::make_mut(&mut other_data) *= 2; // Won't clone anything
+ ///
+ /// // Now `data` and `other_data` point to different values.
+ /// assert_eq!(*data, 8);
+ /// assert_eq!(*other_data, 12);
/// ```
#[inline]
- #[unstable(feature = "rc_unique")]
- pub fn make_unique(&mut self) -> &mut T {
- if !Rc::is_unique(self) {
- *self = Rc::new((**self).clone())
+ #[stable(feature = "rc_unique", since = "1.4.0")]
+ pub fn make_mut(this: &mut Self) -> &mut T {
+ if Rc::strong_count(this) != 1 {
+ // Gotta clone the data, there are other Rcs
+ *this = Rc::new((**this).clone())
+ } else if Rc::weak_count(this) != 0 {
+ // Can just steal the data, all that's left is Weaks
+ unsafe {
+ let mut swap = Rc::new(ptr::read(&this.ptr.as_ref().value));
+ mem::swap(this, &mut swap);
+ swap.dec_strong();
+ // Remove implicit strong-weak ref (no need to craft a fake
+ // Weak here -- we know other Weaks can clean up for us)
+ swap.dec_weak();
+ forget(swap);
+ }
}
// 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 `Rc<T>` itself to be `mut`, so we're returning the only possible
// reference to the inner value.
- let inner = unsafe { &mut **self._ptr };
- &mut inner.value
+ unsafe {
+ &mut this.ptr.as_mut().value
+ }
+ }
+}
+
+impl Rc<Any> {
+ #[inline]
+ #[unstable(feature = "rc_downcast", issue = "44608")]
+ /// Attempt to downcast the `Rc<Any>` to a concrete type.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(rc_downcast)]
+ /// use std::any::Any;
+ /// use std::rc::Rc;
+ ///
+ /// fn print_if_string(value: Rc<Any>) {
+ /// if let Ok(string) = value.downcast::<String>() {
+ /// println!("String ({}): {}", string.len(), string);
+ /// }
+ /// }
+ ///
+ /// fn main() {
+ /// let my_string = "Hello World".to_string();
+ /// print_if_string(Rc::new(my_string));
+ /// print_if_string(Rc::new(0i8));
+ /// }
+ /// ```
+ pub fn downcast<T: Any>(self) -> Result<Rc<T>, Rc<Any>> {
+ if (*self).is::<T>() {
+ // avoid the pointer arithmetic in from_raw
+ unsafe {
+ let raw: *const RcBox<Any> = self.ptr.as_ptr();
+ forget(self);
+ Ok(Rc {
+ ptr: NonNull::new_unchecked(raw as *const RcBox<T> as *mut _),
+ phantom: PhantomData,
+ })
+ }
+ } else {
+ Err(self)
+ }
+ }
+}
+
+impl<T: ?Sized> Rc<T> {
+ // Allocates an `RcBox<T>` with sufficient space for an unsized value
+ unsafe fn allocate_for_ptr(ptr: *const T) -> *mut RcBox<T> {
+ // Create a fake RcBox to find allocation size and alignment
+ let fake_ptr = ptr as *mut RcBox<T>;
+
+ let layout = Layout::for_value(&*fake_ptr);
+
+ let mem = Heap.alloc(layout)
+ .unwrap_or_else(|e| Heap.oom(e));
+
+ // Initialize the real RcBox
+ let inner = set_data_ptr(ptr as *mut T, mem) as *mut RcBox<T>;
+
+ ptr::write(&mut (*inner).strong, Cell::new(1));
+ ptr::write(&mut (*inner).weak, Cell::new(1));
+
+ inner
+ }
+
+ fn from_box(v: Box<T>) -> Rc<T> {
+ unsafe {
+ let bptr = Box::into_raw(v);
+
+ let value_size = size_of_val(&*bptr);
+ let ptr = Self::allocate_for_ptr(bptr);
+
+ // Copy value as bytes
+ ptr::copy_nonoverlapping(
+ bptr as *const T as *const u8,
+ &mut (*ptr).value as *mut _ as *mut u8,
+ value_size);
+
+ // Free the allocation without dropping its contents
+ box_free(bptr);
+
+ Rc { ptr: NonNull::new_unchecked(ptr), phantom: PhantomData }
+ }
+ }
+}
+
+// Sets the data pointer of a `?Sized` raw pointer.
+//
+// For a slice/trait object, this sets the `data` field and leaves the rest
+// unchanged. For a sized raw pointer, this simply sets the pointer.
+unsafe fn set_data_ptr<T: ?Sized, U>(mut ptr: *mut T, data: *mut U) -> *mut T {
+ ptr::write(&mut ptr as *mut _ as *mut *mut u8, data as *mut u8);
+ ptr
+}
+
+impl<T> Rc<[T]> {
+ // Copy elements from slice into newly allocated Rc<[T]>
+ //
+ // Unsafe because the caller must either take ownership or bind `T: Copy`
+ unsafe fn copy_from_slice(v: &[T]) -> Rc<[T]> {
+ let v_ptr = v as *const [T];
+ let ptr = Self::allocate_for_ptr(v_ptr);
+
+ ptr::copy_nonoverlapping(
+ v.as_ptr(),
+ &mut (*ptr).value as *mut [T] as *mut T,
+ v.len());
+
+ Rc { ptr: NonNull::new_unchecked(ptr), phantom: PhantomData }
+ }
+}
+
+trait RcFromSlice<T> {
+ fn from_slice(slice: &[T]) -> Self;
+}
+
+impl<T: Clone> RcFromSlice<T> for Rc<[T]> {
+ #[inline]
+ default fn from_slice(v: &[T]) -> Self {
+ // Panic guard while cloning T elements.
+ // In the event of a panic, elements that have been written
+ // into the new RcBox will be dropped, then the memory freed.
+ struct Guard<T> {
+ mem: *mut u8,
+ elems: *mut T,
+ layout: Layout,
+ n_elems: usize,
+ }
+
+ impl<T> Drop for Guard<T> {
+ fn drop(&mut self) {
+ use core::slice::from_raw_parts_mut;
+
+ unsafe {
+ let slice = from_raw_parts_mut(self.elems, self.n_elems);
+ ptr::drop_in_place(slice);
+
+ Heap.dealloc(self.mem, self.layout.clone());
+ }
+ }
+ }
+
+ unsafe {
+ let v_ptr = v as *const [T];
+ let ptr = Self::allocate_for_ptr(v_ptr);
+
+ let mem = ptr as *mut _ as *mut u8;
+ let layout = Layout::for_value(&*ptr);
+
+ // Pointer to first element
+ let elems = &mut (*ptr).value as *mut [T] as *mut T;
+
+ let mut guard = Guard{
+ mem: mem,
+ elems: elems,
+ layout: layout,
+ n_elems: 0,
+ };
+
+ for (i, item) in v.iter().enumerate() {
+ ptr::write(elems.offset(i as isize), item.clone());
+ guard.n_elems += 1;
+ }
+
+ // All clear. Forget the guard so it doesn't free the new RcBox.
+ forget(guard);
+
+ Rc { ptr: NonNull::new_unchecked(ptr), phantom: PhantomData }
+ }
+ }
+}
+
+impl<T: Copy> RcFromSlice<T> for Rc<[T]> {
+ #[inline]
+ fn from_slice(v: &[T]) -> Self {
+ unsafe { Rc::copy_from_slice(v) }
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized> Drop for Rc<T> {
- /// Drops the `Rc<T>`.
+unsafe impl<#[may_dangle] T: ?Sized> Drop for Rc<T> {
+ /// Drops the `Rc`.
///
/// 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.
+ /// count reaches zero then the only other references (if any) are
+ /// [`Weak`][weak], so we `drop` the inner value.
+ ///
+ /// [weak]: struct.Weak.html
///
/// # Examples
///
/// ```
/// use std::rc::Rc;
///
- /// {
- /// let five = Rc::new(5);
- ///
- /// // stuff
+ /// struct Foo;
///
- /// drop(five); // explicit drop
+ /// impl Drop for Foo {
+ /// fn drop(&mut self) {
+ /// println!("dropped!");
+ /// }
/// }
- /// {
- /// let five = Rc::new(5);
///
- /// // stuff
+ /// let foo = Rc::new(Foo);
+ /// let foo2 = Rc::clone(&foo);
///
- /// } // implicit drop
+ /// drop(foo); // Doesn't print anything
+ /// drop(foo2); // Prints "dropped!"
/// ```
fn drop(&mut self) {
unsafe {
- let ptr = *self._ptr;
- if !(*(&ptr as *const _ as *const *const ())).is_null() &&
- ptr as *const () as usize != mem::POST_DROP_USIZE {
- self.dec_strong();
- if self.strong() == 0 {
- // destroy the contained object
- drop_in_place(&mut (*ptr).value);
-
- // remove the implicit "strong weak" pointer now that we've
- // destroyed the contents.
- self.dec_weak();
-
- if self.weak() == 0 {
- deallocate(ptr as *mut u8,
- size_of_val(&*ptr),
- align_of_val(&*ptr))
- }
+ let ptr = self.ptr.as_ptr();
+
+ self.dec_strong();
+ if self.strong() == 0 {
+ // destroy the contained object
+ ptr::drop_in_place(self.ptr.as_mut());
+
+ // remove the implicit "strong weak" pointer now that we've
+ // destroyed the contents.
+ self.dec_weak();
+
+ if self.weak() == 0 {
+ Heap.dealloc(ptr as *mut u8, Layout::for_value(&*ptr));
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: ?Sized> Clone for Rc<T> {
-
- /// Makes a clone of the `Rc<T>`.
+ /// Makes a clone of the `Rc` pointer.
///
- /// When you clone an `Rc<T>`, it will create another pointer to the data and
- /// increase the strong reference counter.
+ /// This creates another pointer to the same inner value, increasing the
+ /// strong reference count.
///
/// # Examples
///
///
/// let five = Rc::new(5);
///
- /// five.clone();
+ /// Rc::clone(&five);
/// ```
#[inline]
fn clone(&self) -> Rc<T> {
self.inc_strong();
- Rc { _ptr: self._ptr }
+ Rc { ptr: self.ptr, phantom: PhantomData }
}
}
/// use std::rc::Rc;
///
/// let x: Rc<i32> = Default::default();
+ /// assert_eq!(*x, 0);
/// ```
#[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
fn default() -> Rc<T> {
Rc::new(Default::default())
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: ?Sized + PartialEq> PartialEq for Rc<T> {
- /// Equality for two `Rc<T>`s.
+ /// Equality for two `Rc`s.
///
- /// Two `Rc<T>`s are equal if their inner value are equal.
+ /// Two `Rc`s are equal if their inner values are equal.
///
/// # Examples
///
///
/// let five = Rc::new(5);
///
- /// five == Rc::new(5);
+ /// assert!(five == Rc::new(5));
/// ```
#[inline(always)]
- fn eq(&self, other: &Rc<T>) -> bool { **self == **other }
+ fn eq(&self, other: &Rc<T>) -> bool {
+ **self == **other
+ }
- /// Inequality for two `Rc<T>`s.
+ /// Inequality for two `Rc`s.
///
- /// Two `Rc<T>`s are unequal if their inner value are unequal.
+ /// Two `Rc`s are unequal if their inner values are unequal.
///
/// # Examples
///
///
/// let five = Rc::new(5);
///
- /// five != Rc::new(5);
+ /// assert!(five != Rc::new(6));
/// ```
#[inline(always)]
- fn ne(&self, other: &Rc<T>) -> bool { **self != **other }
+ fn ne(&self, other: &Rc<T>) -> bool {
+ **self != **other
+ }
}
#[stable(feature = "rust1", since = "1.0.0")]
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: ?Sized + PartialOrd> PartialOrd for Rc<T> {
- /// Partial comparison for two `Rc<T>`s.
+ /// Partial comparison for two `Rc`s.
///
/// The two are compared by calling `partial_cmp()` on their inner values.
///
///
/// ```
/// use std::rc::Rc;
+ /// use std::cmp::Ordering;
///
/// let five = Rc::new(5);
///
- /// five.partial_cmp(&Rc::new(5));
+ /// assert_eq!(Some(Ordering::Less), five.partial_cmp(&Rc::new(6)));
/// ```
#[inline(always)]
fn partial_cmp(&self, other: &Rc<T>) -> Option<Ordering> {
(**self).partial_cmp(&**other)
}
- /// Less-than comparison for two `Rc<T>`s.
+ /// Less-than comparison for two `Rc`s.
///
/// The two are compared by calling `<` on their inner values.
///
///
/// let five = Rc::new(5);
///
- /// five < Rc::new(5);
+ /// assert!(five < Rc::new(6));
/// ```
#[inline(always)]
- fn lt(&self, other: &Rc<T>) -> bool { **self < **other }
+ fn lt(&self, other: &Rc<T>) -> bool {
+ **self < **other
+ }
- /// 'Less-than or equal to' comparison for two `Rc<T>`s.
+ /// 'Less than or equal to' comparison for two `Rc`s.
///
/// The two are compared by calling `<=` on their inner values.
///
///
/// let five = Rc::new(5);
///
- /// five <= Rc::new(5);
+ /// assert!(five <= Rc::new(5));
/// ```
#[inline(always)]
- fn le(&self, other: &Rc<T>) -> bool { **self <= **other }
+ fn le(&self, other: &Rc<T>) -> bool {
+ **self <= **other
+ }
- /// Greater-than comparison for two `Rc<T>`s.
+ /// Greater-than comparison for two `Rc`s.
///
/// The two are compared by calling `>` on their inner values.
///
///
/// let five = Rc::new(5);
///
- /// five > Rc::new(5);
+ /// assert!(five > Rc::new(4));
/// ```
#[inline(always)]
- fn gt(&self, other: &Rc<T>) -> bool { **self > **other }
+ fn gt(&self, other: &Rc<T>) -> bool {
+ **self > **other
+ }
- /// 'Greater-than or equal to' comparison for two `Rc<T>`s.
+ /// 'Greater than or equal to' comparison for two `Rc`s.
///
/// The two are compared by calling `>=` on their inner values.
///
///
/// let five = Rc::new(5);
///
- /// five >= Rc::new(5);
+ /// assert!(five >= Rc::new(5));
/// ```
#[inline(always)]
- fn ge(&self, other: &Rc<T>) -> bool { **self >= **other }
+ fn ge(&self, other: &Rc<T>) -> bool {
+ **self >= **other
+ }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: ?Sized + Ord> Ord for Rc<T> {
- /// Comparison for two `Rc<T>`s.
+ /// Comparison for two `Rc`s.
///
/// The two are compared by calling `cmp()` on their inner values.
///
///
/// ```
/// use std::rc::Rc;
+ /// use std::cmp::Ordering;
///
/// let five = Rc::new(5);
///
- /// five.partial_cmp(&Rc::new(5));
+ /// assert_eq!(Ordering::Less, five.cmp(&Rc::new(6)));
/// ```
#[inline]
- fn cmp(&self, other: &Rc<T>) -> Ordering { (**self).cmp(&**other) }
+ fn cmp(&self, other: &Rc<T>) -> Ordering {
+ (**self).cmp(&**other)
+ }
}
#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized+Hash> Hash for Rc<T> {
+impl<T: ?Sized + Hash> Hash for Rc<T> {
fn hash<H: Hasher>(&self, state: &mut H) {
(**self).hash(state);
}
}
#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized+fmt::Display> fmt::Display for Rc<T> {
+impl<T: ?Sized + fmt::Display> fmt::Display for Rc<T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
fmt::Display::fmt(&**self, f)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized+fmt::Debug> fmt::Debug for Rc<T> {
+impl<T: ?Sized + fmt::Debug> fmt::Debug for Rc<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 Rc<T> {
+impl<T: ?Sized> fmt::Pointer for Rc<T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
- fmt::Pointer::fmt(&*self._ptr, f)
+ fmt::Pointer::fmt(&(&**self as *const T), f)
+ }
+}
+
+#[stable(feature = "from_for_ptrs", since = "1.6.0")]
+impl<T> From<T> for Rc<T> {
+ fn from(t: T) -> Self {
+ Rc::new(t)
+ }
+}
+
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl<'a, T: Clone> From<&'a [T]> for Rc<[T]> {
+ #[inline]
+ fn from(v: &[T]) -> Rc<[T]> {
+ <Self as RcFromSlice<T>>::from_slice(v)
+ }
+}
+
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl<'a> From<&'a str> for Rc<str> {
+ #[inline]
+ fn from(v: &str) -> Rc<str> {
+ let rc = Rc::<[u8]>::from(v.as_bytes());
+ unsafe { Rc::from_raw(Rc::into_raw(rc) as *const str) }
+ }
+}
+
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl From<String> for Rc<str> {
+ #[inline]
+ fn from(v: String) -> Rc<str> {
+ Rc::from(&v[..])
+ }
+}
+
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl<T: ?Sized> From<Box<T>> for Rc<T> {
+ #[inline]
+ fn from(v: Box<T>) -> Rc<T> {
+ Rc::from_box(v)
+ }
+}
+
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl<T> From<Vec<T>> for Rc<[T]> {
+ #[inline]
+ fn from(mut v: Vec<T>) -> Rc<[T]> {
+ unsafe {
+ let rc = Rc::copy_from_slice(&v);
+
+ // Allow the Vec to free its memory, but not destroy its contents
+ v.set_len(0);
+
+ rc
+ }
}
}
-/// A weak version of `Rc<T>`.
+/// `Weak` is a version of [`Rc`] that holds a non-owning reference to the
+/// managed value. The value is accessed by calling [`upgrade`] on the `Weak`
+/// pointer, which returns an [`Option`]`<`[`Rc`]`<T>>`.
+///
+/// Since a `Weak` reference does not count towards ownership, it will not
+/// prevent the inner value from being dropped, and `Weak` itself makes no
+/// guarantees about the value still being present and may return [`None`]
+/// when [`upgrade`]d.
+///
+/// A `Weak` pointer is useful for keeping a temporary reference to the value
+/// within [`Rc`] without extending its lifetime. It is also used to prevent
+/// circular references between [`Rc`] pointers, since mutual owning references
+/// would never allow either [`Rc`] to be dropped. For example, a tree could
+/// have strong [`Rc`] pointers from parent nodes to children, and `Weak`
+/// pointers from children back to their parents.
///
-/// Weak references do not count when determining if the inner value should be
-/// dropped.
+/// The typical way to obtain a `Weak` pointer is to call [`Rc::downgrade`].
///
-/// See the [module level documentation](./index.html) for more.
-#[unsafe_no_drop_flag]
-#[unstable(feature = "rc_weak",
- reason = "Weak pointers may not belong in this module.")]
+/// [`Rc`]: struct.Rc.html
+/// [`Rc::downgrade`]: struct.Rc.html#method.downgrade
+/// [`upgrade`]: struct.Weak.html#method.upgrade
+/// [`Option`]: ../../std/option/enum.Option.html
+/// [`None`]: ../../std/option/enum.Option.html#variant.None
+#[stable(feature = "rc_weak", since = "1.4.0")]
pub struct Weak<T: ?Sized> {
- // FIXME #12808: strange names to try to avoid interfering with
- // field accesses of the contained type via Deref
- _ptr: NonZero<*mut RcBox<T>>,
+ ptr: NonNull<RcBox<T>>,
}
+#[stable(feature = "rc_weak", since = "1.4.0")]
impl<T: ?Sized> !marker::Send for Weak<T> {}
+#[stable(feature = "rc_weak", since = "1.4.0")]
impl<T: ?Sized> !marker::Sync for Weak<T> {}
-#[unstable(feature = "rc_weak",
- reason = "Weak pointers may not belong in this module.")]
-impl<T: ?Sized> Weak<T> {
+#[unstable(feature = "coerce_unsized", issue = "27732")]
+impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Weak<U>> for Weak<T> {}
+
+impl<T> Weak<T> {
+ /// Constructs a new `Weak<T>`, allocating memory for `T` without initializing
+ /// it. Calling [`upgrade`] on the return value always gives [`None`].
+ ///
+ /// [`upgrade`]: struct.Weak.html#method.upgrade
+ /// [`None`]: ../../std/option/enum.Option.html
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Weak;
+ ///
+ /// let empty: Weak<i64> = Weak::new();
+ /// assert!(empty.upgrade().is_none());
+ /// ```
+ #[stable(feature = "downgraded_weak", since = "1.10.0")]
+ pub fn new() -> Weak<T> {
+ unsafe {
+ Weak {
+ ptr: Box::into_raw_non_null(box RcBox {
+ strong: Cell::new(0),
+ weak: Cell::new(1),
+ value: uninitialized(),
+ }),
+ }
+ }
+ }
+}
- /// Upgrades a weak reference to a strong reference.
+impl<T: ?Sized> Weak<T> {
+ /// Attempts to upgrade the `Weak` pointer to an [`Rc`], extending
+ /// the lifetime of the value if successful.
///
- /// Upgrades the `Weak<T>` reference to an `Rc<T>`, if possible.
+ /// Returns [`None`] if the value has since been dropped.
///
- /// Returns `None` if there were no strong references and the data was
- /// destroyed.
+ /// [`Rc`]: struct.Rc.html
+ /// [`None`]: ../../std/option/enum.Option.html
///
/// # Examples
///
/// ```
- /// # #![feature(rc_weak)]
/// use std::rc::Rc;
///
/// let five = Rc::new(5);
///
- /// let weak_five = five.downgrade();
+ /// let weak_five = Rc::downgrade(&five);
///
/// let strong_five: Option<Rc<_>> = weak_five.upgrade();
+ /// assert!(strong_five.is_some());
+ ///
+ /// // Destroy all strong pointers.
+ /// drop(strong_five);
+ /// drop(five);
+ ///
+ /// assert!(weak_five.upgrade().is_none());
/// ```
+ #[stable(feature = "rc_weak", since = "1.4.0")]
pub fn upgrade(&self) -> Option<Rc<T>> {
if self.strong() == 0 {
None
} else {
self.inc_strong();
- Some(Rc { _ptr: self._ptr })
+ Some(Rc { ptr: self.ptr, phantom: PhantomData })
}
}
}
-#[stable(feature = "rust1", since = "1.0.0")]
+#[stable(feature = "rc_weak", since = "1.4.0")]
impl<T: ?Sized> Drop for Weak<T> {
- /// Drops the `Weak<T>`.
- ///
- /// This will decrement the weak reference count.
+ /// Drops the `Weak` pointer.
///
/// # Examples
///
/// ```
- /// # #![feature(rc_weak)]
- /// use std::rc::Rc;
+ /// use std::rc::{Rc, Weak};
///
- /// {
- /// let five = Rc::new(5);
- /// let weak_five = five.downgrade();
+ /// struct Foo;
///
- /// // stuff
- ///
- /// drop(weak_five); // explicit drop
+ /// impl Drop for Foo {
+ /// fn drop(&mut self) {
+ /// println!("dropped!");
+ /// }
/// }
- /// {
- /// let five = Rc::new(5);
- /// let weak_five = five.downgrade();
///
- /// // stuff
+ /// let foo = Rc::new(Foo);
+ /// let weak_foo = Rc::downgrade(&foo);
+ /// let other_weak_foo = Weak::clone(&weak_foo);
+ ///
+ /// drop(weak_foo); // Doesn't print anything
+ /// drop(foo); // Prints "dropped!"
///
- /// } // implicit drop
+ /// assert!(other_weak_foo.upgrade().is_none());
/// ```
fn drop(&mut self) {
unsafe {
- let ptr = *self._ptr;
- if !(*(&ptr as *const _ as *const *const ())).is_null() &&
- ptr as *const () as usize != mem::POST_DROP_USIZE {
- self.dec_weak();
- // the weak count starts at 1, and will only go to zero if all
- // the strong pointers have disappeared.
- if self.weak() == 0 {
- deallocate(ptr as *mut u8, size_of_val(&*ptr),
- align_of_val(&*ptr))
- }
+ let ptr = self.ptr.as_ptr();
+
+ self.dec_weak();
+ // the weak count starts at 1, and will only go to zero if all
+ // the strong pointers have disappeared.
+ if self.weak() == 0 {
+ Heap.dealloc(ptr as *mut u8, Layout::for_value(&*ptr));
}
}
}
}
-#[unstable(feature = "rc_weak",
- reason = "Weak pointers may not belong in this module.")]
+#[stable(feature = "rc_weak", since = "1.4.0")]
impl<T: ?Sized> Clone for Weak<T> {
-
- /// Makes a clone of the `Weak<T>`.
- ///
- /// This increases the weak reference count.
+ /// Makes a clone of the `Weak` pointer that points to the same value.
///
/// # Examples
///
/// ```
- /// # #![feature(rc_weak)]
- /// use std::rc::Rc;
+ /// use std::rc::{Rc, Weak};
///
- /// let weak_five = Rc::new(5).downgrade();
+ /// let weak_five = Rc::downgrade(&Rc::new(5));
///
- /// weak_five.clone();
+ /// Weak::clone(&weak_five);
/// ```
#[inline]
fn clone(&self) -> Weak<T> {
self.inc_weak();
- Weak { _ptr: self._ptr }
+ Weak { ptr: self.ptr }
}
}
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized+fmt::Debug> fmt::Debug for Weak<T> {
+#[stable(feature = "rc_weak", since = "1.4.0")]
+impl<T: ?Sized + fmt::Debug> fmt::Debug for Weak<T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "(Weak)")
}
}
+#[stable(feature = "downgraded_weak", since = "1.10.0")]
+impl<T> Default for Weak<T> {
+ /// Constructs a new `Weak<T>`, allocating memory for `T` without initializing
+ /// it. Calling [`upgrade`] on the return value always gives [`None`].
+ ///
+ /// [`upgrade`]: struct.Weak.html#method.upgrade
+ /// [`None`]: ../../std/option/enum.Option.html
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::rc::Weak;
+ ///
+ /// let empty: Weak<i64> = Default::default();
+ /// assert!(empty.upgrade().is_none());
+ /// ```
+ fn default() -> Weak<T> {
+ Weak::new()
+ }
+}
+
+// NOTE: We checked_add here to deal with mem::forget safety. In particular
+// if you mem::forget Rcs (or Weaks), the ref-count can overflow, and then
+// you can free the allocation while outstanding Rcs (or Weaks) exist.
+// We abort because this is such a degenerate scenario that we don't care about
+// what happens -- no real program should ever experience this.
+//
+// This should have negligible overhead since you don't actually need to
+// clone these much in Rust thanks to ownership and move-semantics.
+
#[doc(hidden)]
trait RcBoxPtr<T: ?Sized> {
fn inner(&self) -> &RcBox<T>;
#[inline]
- fn strong(&self) -> usize { self.inner().strong.get() }
+ fn strong(&self) -> usize {
+ self.inner().strong.get()
+ }
#[inline]
- fn inc_strong(&self) { self.inner().strong.set(self.strong() + 1); }
+ fn inc_strong(&self) {
+ self.inner().strong.set(self.strong().checked_add(1).unwrap_or_else(|| unsafe { abort() }));
+ }
#[inline]
- fn dec_strong(&self) { self.inner().strong.set(self.strong() - 1); }
+ fn dec_strong(&self) {
+ self.inner().strong.set(self.strong() - 1);
+ }
#[inline]
- fn weak(&self) -> usize { self.inner().weak.get() }
+ fn weak(&self) -> usize {
+ self.inner().weak.get()
+ }
#[inline]
- fn inc_weak(&self) { self.inner().weak.set(self.weak() + 1); }
+ fn inc_weak(&self) {
+ self.inner().weak.set(self.weak().checked_add(1).unwrap_or_else(|| unsafe { abort() }));
+ }
#[inline]
- fn dec_weak(&self) { self.inner().weak.set(self.weak() - 1); }
+ fn dec_weak(&self) {
+ self.inner().weak.set(self.weak() - 1);
+ }
}
impl<T: ?Sized> RcBoxPtr<T> for Rc<T> {
#[inline(always)]
fn inner(&self) -> &RcBox<T> {
unsafe {
- // Safe to assume this here, as if it weren't true, we'd be breaking
- // the contract anyway.
- // This allows the null check to be elided in the destructor if we
- // manipulated the reference count in the same function.
- assume(!(*(&self._ptr as *const _ as *const *const ())).is_null());
- &(**self._ptr)
+ self.ptr.as_ref()
}
}
}
#[inline(always)]
fn inner(&self) -> &RcBox<T> {
unsafe {
- // Safe to assume this here, as if it weren't true, we'd be breaking
- // the contract anyway.
- // This allows the null check to be elided in the destructor if we
- // manipulated the reference count in the same function.
- assume(!(*(&self._ptr as *const _ as *const *const ())).is_null());
- &(**self._ptr)
+ self.ptr.as_ref()
}
}
}
#[cfg(test)]
mod tests {
- use super::{Rc, Weak, weak_count, strong_count};
+ use super::{Rc, Weak};
use std::boxed::Box;
use std::cell::RefCell;
use std::option::Option;
- use std::option::Option::{Some, None};
+ use std::option::Option::{None, Some};
use std::result::Result::{Err, Ok};
use std::mem::drop;
use std::clone::Clone;
+ use std::convert::From;
#[test]
fn test_clone() {
#[test]
fn test_live() {
let x = Rc::new(5);
- let y = x.downgrade();
+ let y = Rc::downgrade(&x);
assert!(y.upgrade().is_some());
}
#[test]
fn test_dead() {
let x = Rc::new(5);
- let y = x.downgrade();
+ let y = Rc::downgrade(&x);
drop(x);
assert!(y.upgrade().is_none());
}
#[test]
fn weak_self_cyclic() {
struct Cycle {
- x: RefCell<Option<Weak<Cycle>>>
+ x: RefCell<Option<Weak<Cycle>>>,
}
let a = Rc::new(Cycle { x: RefCell::new(None) });
- let b = a.clone().downgrade();
+ let b = Rc::downgrade(&a.clone());
*a.x.borrow_mut() = Some(b);
// hopefully we don't double-free (or leak)...
#[test]
fn is_unique() {
let x = Rc::new(3);
- assert!(super::is_unique(&x));
+ assert!(Rc::is_unique(&x));
let y = x.clone();
- assert!(!super::is_unique(&x));
+ assert!(!Rc::is_unique(&x));
drop(y);
- assert!(super::is_unique(&x));
- let w = x.downgrade();
- assert!(!super::is_unique(&x));
+ assert!(Rc::is_unique(&x));
+ let w = Rc::downgrade(&x);
+ assert!(!Rc::is_unique(&x));
drop(w);
- assert!(super::is_unique(&x));
+ assert!(Rc::is_unique(&x));
}
#[test]
fn test_strong_count() {
- let a = Rc::new(0u32);
- assert!(strong_count(&a) == 1);
- let w = a.downgrade();
- assert!(strong_count(&a) == 1);
+ let a = Rc::new(0);
+ assert!(Rc::strong_count(&a) == 1);
+ let w = Rc::downgrade(&a);
+ assert!(Rc::strong_count(&a) == 1);
let b = w.upgrade().expect("upgrade of live rc failed");
- assert!(strong_count(&b) == 2);
- assert!(strong_count(&a) == 2);
+ assert!(Rc::strong_count(&b) == 2);
+ assert!(Rc::strong_count(&a) == 2);
drop(w);
drop(a);
- assert!(strong_count(&b) == 1);
+ assert!(Rc::strong_count(&b) == 1);
let c = b.clone();
- assert!(strong_count(&b) == 2);
- assert!(strong_count(&c) == 2);
+ assert!(Rc::strong_count(&b) == 2);
+ assert!(Rc::strong_count(&c) == 2);
}
#[test]
fn test_weak_count() {
- let a = Rc::new(0u32);
- assert!(strong_count(&a) == 1);
- assert!(weak_count(&a) == 0);
- let w = a.downgrade();
- assert!(strong_count(&a) == 1);
- assert!(weak_count(&a) == 1);
+ let a = Rc::new(0);
+ assert!(Rc::strong_count(&a) == 1);
+ assert!(Rc::weak_count(&a) == 0);
+ let w = Rc::downgrade(&a);
+ assert!(Rc::strong_count(&a) == 1);
+ assert!(Rc::weak_count(&a) == 1);
drop(w);
- assert!(strong_count(&a) == 1);
- assert!(weak_count(&a) == 0);
+ assert!(Rc::strong_count(&a) == 1);
+ assert!(Rc::weak_count(&a) == 0);
let c = a.clone();
- assert!(strong_count(&a) == 2);
- assert!(weak_count(&a) == 0);
+ assert!(Rc::strong_count(&a) == 2);
+ assert!(Rc::weak_count(&a) == 0);
drop(c);
}
#[test]
fn try_unwrap() {
let x = Rc::new(3);
- assert_eq!(super::try_unwrap(x), Ok(3));
+ assert_eq!(Rc::try_unwrap(x), Ok(3));
let x = Rc::new(4);
let _y = x.clone();
- assert_eq!(super::try_unwrap(x), Err(Rc::new(4)));
+ assert_eq!(Rc::try_unwrap(x), Err(Rc::new(4)));
let x = Rc::new(5);
- let _w = x.downgrade();
- assert_eq!(super::try_unwrap(x), Err(Rc::new(5)));
+ let _w = Rc::downgrade(&x);
+ assert_eq!(Rc::try_unwrap(x), Ok(5));
+ }
+
+ #[test]
+ fn into_from_raw() {
+ let x = Rc::new(box "hello");
+ let y = x.clone();
+
+ let x_ptr = Rc::into_raw(x);
+ drop(y);
+ unsafe {
+ assert_eq!(**x_ptr, "hello");
+
+ let x = Rc::from_raw(x_ptr);
+ assert_eq!(**x, "hello");
+
+ assert_eq!(Rc::try_unwrap(x).map(|x| *x), Ok("hello"));
+ }
+ }
+
+ #[test]
+ fn test_into_from_raw_unsized() {
+ use std::fmt::Display;
+ use std::string::ToString;
+
+ let rc: Rc<str> = Rc::from("foo");
+
+ let ptr = Rc::into_raw(rc.clone());
+ let rc2 = unsafe { Rc::from_raw(ptr) };
+
+ assert_eq!(unsafe { &*ptr }, "foo");
+ assert_eq!(rc, rc2);
+
+ let rc: Rc<Display> = Rc::new(123);
+
+ let ptr = Rc::into_raw(rc.clone());
+ let rc2 = unsafe { Rc::from_raw(ptr) };
+
+ assert_eq!(unsafe { &*ptr }.to_string(), "123");
+ assert_eq!(rc2.to_string(), "123");
}
#[test]
fn get_mut() {
let mut x = Rc::new(3);
- *super::get_mut(&mut x).unwrap() = 4;
+ *Rc::get_mut(&mut x).unwrap() = 4;
assert_eq!(*x, 4);
let y = x.clone();
- assert!(super::get_mut(&mut x).is_none());
+ assert!(Rc::get_mut(&mut x).is_none());
drop(y);
- assert!(super::get_mut(&mut x).is_some());
- let _w = x.downgrade();
- assert!(super::get_mut(&mut x).is_none());
+ assert!(Rc::get_mut(&mut x).is_some());
+ let _w = Rc::downgrade(&x);
+ assert!(Rc::get_mut(&mut x).is_none());
}
#[test]
let mut cow1 = cow0.clone();
let mut cow2 = cow1.clone();
- assert!(75 == *cow0.make_unique());
- assert!(75 == *cow1.make_unique());
- assert!(75 == *cow2.make_unique());
+ assert!(75 == *Rc::make_mut(&mut cow0));
+ assert!(75 == *Rc::make_mut(&mut cow1));
+ assert!(75 == *Rc::make_mut(&mut cow2));
- *cow0.make_unique() += 1;
- *cow1.make_unique() += 2;
- *cow2.make_unique() += 3;
+ *Rc::make_mut(&mut cow0) += 1;
+ *Rc::make_mut(&mut cow1) += 2;
+ *Rc::make_mut(&mut cow2) += 3;
assert!(76 == *cow0);
assert!(77 == *cow1);
assert!(75 == *cow1);
assert!(75 == *cow2);
- *cow0.make_unique() += 1;
+ *Rc::make_mut(&mut cow0) += 1;
assert!(76 == *cow0);
assert!(75 == *cow1);
#[test]
fn test_cowrc_clone_weak() {
let mut cow0 = Rc::new(75);
- let cow1_weak = cow0.downgrade();
+ let cow1_weak = Rc::downgrade(&cow0);
assert!(75 == *cow0);
assert!(75 == *cow1_weak.upgrade().unwrap());
- *cow0.make_unique() += 1;
+ *Rc::make_mut(&mut cow0) += 1;
assert!(76 == *cow0);
assert!(cow1_weak.upgrade().is_none());
let foo: Rc<[i32]> = Rc::new([1, 2, 3]);
assert_eq!(foo, foo.clone());
}
+
+ #[test]
+ fn test_from_owned() {
+ let foo = 123;
+ let foo_rc = Rc::from(foo);
+ assert!(123 == *foo_rc);
+ }
+
+ #[test]
+ fn test_new_weak() {
+ let foo: Weak<usize> = Weak::new();
+ assert!(foo.upgrade().is_none());
+ }
+
+ #[test]
+ fn test_ptr_eq() {
+ let five = Rc::new(5);
+ let same_five = five.clone();
+ let other_five = Rc::new(5);
+
+ assert!(Rc::ptr_eq(&five, &same_five));
+ assert!(!Rc::ptr_eq(&five, &other_five));
+ }
+
+ #[test]
+ fn test_from_str() {
+ let r: Rc<str> = Rc::from("foo");
+
+ assert_eq!(&r[..], "foo");
+ }
+
+ #[test]
+ fn test_copy_from_slice() {
+ let s: &[u32] = &[1, 2, 3];
+ let r: Rc<[u32]> = Rc::from(s);
+
+ assert_eq!(&r[..], [1, 2, 3]);
+ }
+
+ #[test]
+ fn test_clone_from_slice() {
+ #[derive(Clone, Debug, Eq, PartialEq)]
+ struct X(u32);
+
+ let s: &[X] = &[X(1), X(2), X(3)];
+ let r: Rc<[X]> = Rc::from(s);
+
+ assert_eq!(&r[..], s);
+ }
+
+ #[test]
+ #[should_panic]
+ fn test_clone_from_slice_panic() {
+ use std::string::{String, ToString};
+
+ struct Fail(u32, String);
+
+ impl Clone for Fail {
+ fn clone(&self) -> Fail {
+ if self.0 == 2 {
+ panic!();
+ }
+ Fail(self.0, self.1.clone())
+ }
+ }
+
+ let s: &[Fail] = &[
+ Fail(0, "foo".to_string()),
+ Fail(1, "bar".to_string()),
+ Fail(2, "baz".to_string()),
+ ];
+
+ // Should panic, but not cause memory corruption
+ let _r: Rc<[Fail]> = Rc::from(s);
+ }
+
+ #[test]
+ fn test_from_box() {
+ let b: Box<u32> = box 123;
+ let r: Rc<u32> = Rc::from(b);
+
+ assert_eq!(*r, 123);
+ }
+
+ #[test]
+ fn test_from_box_str() {
+ use std::string::String;
+
+ let s = String::from("foo").into_boxed_str();
+ let r: Rc<str> = Rc::from(s);
+
+ assert_eq!(&r[..], "foo");
+ }
+
+ #[test]
+ fn test_from_box_slice() {
+ let s = vec![1, 2, 3].into_boxed_slice();
+ let r: Rc<[u32]> = Rc::from(s);
+
+ assert_eq!(&r[..], [1, 2, 3]);
+ }
+
+ #[test]
+ fn test_from_box_trait() {
+ use std::fmt::Display;
+ use std::string::ToString;
+
+ let b: Box<Display> = box 123;
+ let r: Rc<Display> = Rc::from(b);
+
+ assert_eq!(r.to_string(), "123");
+ }
+
+ #[test]
+ fn test_from_box_trait_zero_sized() {
+ use std::fmt::Debug;
+
+ let b: Box<Debug> = box ();
+ let r: Rc<Debug> = Rc::from(b);
+
+ assert_eq!(format!("{:?}", r), "()");
+ }
+
+ #[test]
+ fn test_from_vec() {
+ let v = vec![1, 2, 3];
+ let r: Rc<[u32]> = Rc::from(v);
+
+ assert_eq!(&r[..], [1, 2, 3]);
+ }
+
+ #[test]
+ fn test_downcast() {
+ use std::any::Any;
+
+ let r1: Rc<Any> = Rc::new(i32::max_value());
+ let r2: Rc<Any> = Rc::new("abc");
+
+ assert!(r1.clone().downcast::<u32>().is_err());
+
+ let r1i32 = r1.downcast::<i32>();
+ assert!(r1i32.is_ok());
+ assert_eq!(r1i32.unwrap(), Rc::new(i32::max_value()));
+
+ assert!(r2.clone().downcast::<i32>().is_err());
+
+ let r2str = r2.downcast::<&'static str>();
+ assert!(r2str.is_ok());
+ assert_eq!(r2str.unwrap(), Rc::new("abc"));
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> borrow::Borrow<T> for Rc<T> {
+ fn borrow(&self) -> &T {
+ &**self
+ }
+}
+
+#[stable(since = "1.5.0", feature = "smart_ptr_as_ref")]
+impl<T: ?Sized> AsRef<T> for Rc<T> {
+ fn as_ref(&self) -> &T {
+ &**self
+ }
}
projects / rustc.git / blobdiff