Struct std::ptr::Shared
[−]
[src]
pub struct Shared<T> where
T: ?Sized, { /* fields omitted */ }🔬 This is a nightly-only experimental API. (shared #27730)
needs an RFC to flesh out design
A wrapper around a raw *mut T that indicates that the possessor
of this wrapper has shared ownership of the referent. Useful for
building abstractions like Rc<T>, Arc<T>, or doubly-linked lists, which
internally use aliased raw pointers to manage the memory that they own.
This is similar to Unique, except that it doesn't make any aliasing
guarantees, and doesn't derive Send and Sync. Note that unlike &T,
Shared has no special mutability requirements. Shared may mutate data
aliased by other Shared pointers. More precise rules require Rust to
develop an actual aliasing model.
Unlike *mut T, the pointer must always be non-null, even if the pointer
is never dereferenced. This is so that enums may use this forbidden value
as a discriminant -- Option<Shared<T>> has the same size as Shared<T>.
However the pointer may still dangle if it isn't dereferenced.
Unlike *mut T, Shared<T> is covariant over T. If this is incorrect
for your use case, you should include some PhantomData in your type to
provide invariance, such as PhantomData<Cell<T>> or PhantomData<&'a mut T>.
Usually this won't be necessary; covariance is correct for Rc, Arc, and LinkedList
because they provide a public API that follows the normal shared XOR mutable
rules of Rust.
Methods
impl<T> Shared<T>[src]
pub fn empty() -> Shared<T>[src]
Creates a new Shared that is dangling, but well-aligned.
This is useful for initializing types which lazily allocate, like
Vec::new does.
impl<T> Shared<T> where
T: ?Sized, [src]
T: ?Sized,
pub const unsafe fn new_unchecked(ptr: *mut T) -> Shared<T>[src]
pub fn new(ptr: *mut T) -> Option<Shared<T>>[src]
Creates a new Shared if ptr is non-null.
pub fn as_ptr(self) -> *mut T[src]
Acquires the underlying *mut pointer.
ⓘImportant traits for &'a mut Ipub unsafe fn as_ref(&self) -> &T[src]
Dereferences the content.
The resulting lifetime is bound to self so this behaves "as if"
it were actually an instance of T that is getting borrowed. If a longer
(unbound) lifetime is needed, use &*my_ptr.ptr().
ⓘImportant traits for &'a mut Ipub unsafe fn as_mut(&mut self) -> &mut T[src]
Mutably dereferences the content.
The resulting lifetime is bound to self so this behaves "as if"
it were actually an instance of T that is getting borrowed. If a longer
(unbound) lifetime is needed, use &mut *my_ptr.ptr_mut().
pub unsafe fn as_mut_ptr(&self) -> *mut T[src]
: renamed to as_ptr for ergonomics/consistency
Acquires the underlying pointer as a *mut pointer.
Trait Implementations
impl<T> Clone for Shared<T> where
T: ?Sized, [src]
T: ?Sized,
fn clone(&self) -> Shared<T>[src]
Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)1.0.0[src]
Performs copy-assignment from source. Read more
impl<'a, T> From<&'a mut T> for Shared<T> where
T: ?Sized, [src]
T: ?Sized,
impl<'a, T> From<&'a T> for Shared<T> where
T: ?Sized, [src]
T: ?Sized,
impl<T> From<Unique<T>> for Shared<T> where
T: ?Sized, [src]
T: ?Sized,
impl<T> Copy for Shared<T> where
T: ?Sized, [src]
T: ?Sized,
impl<T> !Send for Shared<T> where
T: ?Sized, [src]
T: ?Sized,
Shared pointers are not Send because the data they reference may be aliased.
impl<T, U> CoerceUnsized<Shared<U>> for Shared<T> where
T: Unsize<U> + ?Sized,
U: ?Sized, [src]
T: Unsize<U> + ?Sized,
U: ?Sized,
impl<T> !Sync for Shared<T> where
T: ?Sized, [src]
T: ?Sized,
Shared pointers are not Sync because the data they reference may be aliased.
impl<T> Pointer for Shared<T> where
T: ?Sized, [src]
T: ?Sized,
fn fmt(&self, f: &mut Formatter) -> Result<(), Error>[src]
Formats the value using the given formatter.