Struct std::ptr::NonNull

pub struct NonNull<T> where
    T: ?Sized,  { /* fields omitted */ }

*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.

Methods

impl<T> NonNull<T>

pub fn dangling() -> NonNull<T>

Creates a new NonNull that is dangling, but well-aligned.

This is useful for initializing types which lazily allocate, like Vec::new does.

impl<T> NonNull<T> where     T: ?Sized,

pub const unsafe fn new_unchecked(ptr: *mut T) -> NonNull<T>

Creates a new NonNull.

Safety

ptr must be non-null.

pub fn new(ptr: *mut T) -> Option<NonNull<T>>

Creates a new NonNull if ptr is non-null.

pub fn as_ptr(self) -> *mut T

Acquires the underlying *mut pointer.

Important traits for &'a mut I

impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W

pub unsafe fn as_ref(&self) -> &T

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 &'a mut I

impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W

pub unsafe fn as_mut(&mut self) -> &mut T

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 fn cast<U>(self) -> NonNull<U>

🔬 This is a nightly-only experimental API. (nonnull_cast #47653)

Cast to a pointer of another type

Trait Implementations

impl<T> Copy for NonNull<T> where     T: ?Sized,

impl<T> Pointer for NonNull<T> where     T: ?Sized,

fn fmt(&self, f: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.

impl<T> Debug for NonNull<T> where     T: ?Sized,

fn fmt(&self, f: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.

impl<T> !Sync for NonNull<T> where     T: ?Sized,

NonNull pointers are not Sync because the data they reference may be aliased.

impl<T> !Send for NonNull<T> where     T: ?Sized,

NonNull pointers are not Send because the data they reference may be aliased.

impl<T> Ord for NonNull<T> where     T: ?Sized,

fn cmp(&self, other: &NonNull<T>) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

impl<T> Hash for NonNull<T> where     T: ?Sized,

fn hash<H>(&self, state: &mut H) where     H: Hasher,

Feeds this value into the given [Hasher].

fn hash_slice<H>(data: &[Self], state: &mut H) where     H: Hasher,

Feeds a slice of this type into the given [Hasher].

impl<T> PartialEq<NonNull<T>> for NonNull<T> where     T: ?Sized,

fn eq(&self, other: &NonNull<T>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a, T> From<NonNull<T>> for Unique<T> where     T: ?Sized,

fn from(p: NonNull<T>) -> Unique<T>

Performs the conversion.

impl<T> From<Unique<T>> for NonNull<T> where     T: ?Sized,

fn from(unique: Unique<T>) -> NonNull<T>

Performs the conversion.

impl<'a, T> From<&'a T> for NonNull<T> where     T: ?Sized,

fn from(reference: &'a T) -> NonNull<T>

Performs the conversion.

impl<'a, T> From<&'a mut T> for NonNull<T> where     T: ?Sized,

fn from(reference: &'a mut T) -> NonNull<T>

Performs the conversion.

impl<T> Clone for NonNull<T> where     T: ?Sized,

fn clone(&self) -> NonNull<T>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T> PartialOrd<NonNull<T>> for NonNull<T> where     T: ?Sized,

fn partial_cmp(&self, other: &NonNull<T>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<T> Eq for NonNull<T> where     T: ?Sized,

impl<T, U> CoerceUnsized<NonNull<U>> for NonNull<T> where     T: Unsize<U> + ?Sized,     U: ?Sized,

impl<T: RefUnwindSafe + ?Sized> UnwindSafe for NonNull<T>