1.25.0[−][src]Struct std::ptr::NonNull
*mut T
but non-zero and covariant.
This is often the correct thing to use when building data structures using
raw pointers, but is ultimately more dangerous to use because of its additional
properties. If you're not sure if you should use NonNull<T>
, just use *mut T
!
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<NonNull<T>>
has the same size as *mut T
.
However the pointer may still dangle if it isn't dereferenced.
Unlike *mut T
, NonNull<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 most safe abstractions,
such as Box
, Rc
, Arc
, Vec
, and LinkedList
. This is the case because they
provide a public API that follows the normal shared XOR mutable rules of Rust.
Notice that NonNull<T>
has a From
instance for &T
. However, this does
not change the fact that mutating through a (pointer derived from a) shared
reference is undefined behavior unless the mutation happens inside an
UnsafeCell<T>
. The same goes for creating a mutable reference from a shared
reference. When using this From
instance without an UnsafeCell<T>
,
it is your responsibility to ensure that as_mut
is never called, and as_ptr
is never used for mutation.
Methods
impl<T> NonNull<T>
[src]
pub const fn dangling() -> NonNull<T>
[src]
Creates a new NonNull
that is dangling, but well-aligned.
This is useful for initializing types which lazily allocate, like
Vec::new
does.
Note that the pointer value may potentially represent a valid pointer to
a T
, which means this must not be used as a "not yet initialized"
sentinel value. Types that lazily allocate must track initialization by
some other means.
impl<T> NonNull<T> where
T: ?Sized,
[src]
T: ?Sized,
pub const unsafe fn new_unchecked(ptr: *mut T) -> NonNull<T>
[src]
pub fn new(ptr: *mut T) -> Option<NonNull<T>>
[src]
Creates a new NonNull
if ptr
is non-null.
pub const fn as_ptr(self) -> *mut T
[src]
Acquires the underlying *mut
pointer.
ⓘImportant traits for &'_ mut Fpub 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.as_ptr()
.
ⓘImportant traits for &'_ mut Fpub 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.as_ptr()
.
pub const fn cast<U>(self) -> NonNull<U>
1.27.0[src]
Cast to a pointer of another type
Trait Implementations
impl<'_, T> From<&'_ T> for NonNull<T> where
T: ?Sized,
[src]
T: ?Sized,
impl<'_, T> From<&'_ mut T> for NonNull<T> where
T: ?Sized,
[src]
T: ?Sized,
impl<T> From<Unique<T>> for NonNull<T> where
T: ?Sized,
[src]
T: ?Sized,
impl<T> PartialOrd<NonNull<T>> for NonNull<T> where
T: ?Sized,
[src]
T: ?Sized,
fn partial_cmp(&self, other: &NonNull<T>) -> Option<Ordering>
[src]
#[must_use]
fn lt(&self, other: &Rhs) -> bool
1.0.0[src]
This method tests less than (for self
and other
) and is used by the <
operator. Read more
#[must_use]
fn le(&self, other: &Rhs) -> bool
1.0.0[src]
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
#[must_use]
fn gt(&self, other: &Rhs) -> bool
1.0.0[src]
This method tests greater than (for self
and other
) and is used by the >
operator. Read more
#[must_use]
fn ge(&self, other: &Rhs) -> bool
1.0.0[src]
This method tests greater than or equal to (for self
and other
) and is used by the >=
operator. Read more
impl<T> Hash for NonNull<T> where
T: ?Sized,
[src]
T: ?Sized,
fn hash<H>(&self, state: &mut H) where
H: Hasher,
[src]
H: Hasher,
fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,
1.3.0[src]
H: Hasher,
Feeds a slice of this type into the given [Hasher
]. Read more
impl<T> !Send for NonNull<T> where
T: ?Sized,
[src]
T: ?Sized,
NonNull
pointers are not Send
because the data they reference may be aliased.
impl<T> Eq for NonNull<T> where
T: ?Sized,
[src]
T: ?Sized,
impl<T> Clone for NonNull<T> where
T: ?Sized,
[src]
T: ?Sized,
fn clone(&self) -> NonNull<T>
[src]
fn clone_from(&mut self, source: &Self)
1.0.0[src]
Performs copy-assignment from source
. Read more
impl<T> Pointer for NonNull<T> where
T: ?Sized,
[src]
T: ?Sized,
impl<T> Debug for NonNull<T> where
T: ?Sized,
[src]
T: ?Sized,
impl<T> Copy for NonNull<T> where
T: ?Sized,
[src]
T: ?Sized,
impl<T> Ord for NonNull<T> where
T: ?Sized,
[src]
T: ?Sized,
fn cmp(&self, other: &NonNull<T>) -> Ordering
[src]
fn max(self, other: Self) -> Self
1.21.0[src]
Compares and returns the maximum of two values. Read more
fn min(self, other: Self) -> Self
1.21.0[src]
Compares and returns the minimum of two values. Read more
fn clamp(self, min: Self, max: Self) -> Self
[src]
Restrict a value to a certain interval. Read more
impl<T> PartialEq<NonNull<T>> for NonNull<T> where
T: ?Sized,
[src]
T: ?Sized,
fn eq(&self, other: &NonNull<T>) -> bool
[src]
#[must_use]
fn ne(&self, other: &Rhs) -> bool
1.0.0[src]
This method tests for !=
.
impl<T> !Sync for NonNull<T> where
T: ?Sized,
[src]
T: ?Sized,
NonNull
pointers are not Sync
because the data they reference may be aliased.
impl<T, U> CoerceUnsized<NonNull<U>> for NonNull<T> where
T: Unsize<U> + ?Sized,
U: ?Sized,
[src]
T: Unsize<U> + ?Sized,
U: ?Sized,
impl<T, U> DispatchFromDyn<NonNull<U>> for NonNull<T> where
T: Unsize<U> + ?Sized,
U: ?Sized,
[src]
T: Unsize<U> + ?Sized,
U: ?Sized,
impl<T: RefUnwindSafe + ?Sized> UnwindSafe for NonNull<T>
[src]
Blanket Implementations
impl<T, U> TryFrom<U> for T where
U: Into<T>,
[src]
U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
[src]
impl<T, U> Into<U> for T where
U: From<T>,
[src]
U: From<T>,
impl<T> From<T> for T
[src]
impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
[src]
U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
[src]
impl<T> Borrow<T> for T where
T: ?Sized,
[src]
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
[src]
T: ?Sized,
ⓘImportant traits for &'_ mut Ffn borrow_mut(&mut self) -> &mut T
[src]
impl<T> Any for T where
T: 'static + ?Sized,
[src]
T: 'static + ?Sized,
impl<T> ToOwned for T where
T: Clone,
[src]
T: Clone,