# Struct core::ptr::NonNull 1.25.0[−][src]

    #[repr(transparent)]
    pub struct NonNull<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: Sized> NonNull<T>`

[src]

####

`pub fn dangling() -> Self`

[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: ?Sized> NonNull<T>`

[src]

####

`pub const unsafe fn new_unchecked(ptr: *mut T) -> Self`

[src]

Creates a new `NonNull`.

# Safety

`ptr` must be non-null.

####

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

[src]

Creates a new `NonNull` if `ptr` is non-null.

####

`pub fn as_ptr(self) -> *mut T`

[src]

Acquires the underlying `*mut` pointer.

####

`pub 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()`.

####

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

1.27.0
[src]

Cast to a pointer of another type

## Trait Implementations

###

`impl<T: ?Sized> !Send for NonNull<T>`

[src]

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

###

`impl<T: ?Sized> !Sync for NonNull<T>`

[src]

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

###

`impl<T: ?Sized> Clone for NonNull<T>`

[src]

####

`fn clone(&self) -> Self`

[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<T: ?Sized> Copy for NonNull<T>`

[src]

###

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

[src]

###

`impl<T: ?Sized> Debug for NonNull<T>`

[src]

####

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

[src]

Formats the value using the given formatter. Read more

###

`impl<T: ?Sized> Pointer for NonNull<T>`

[src]

####

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

[src]

Formats the value using the given formatter.

###

`impl<T: ?Sized> Eq for NonNull<T>`

[src]

###

`impl<T: ?Sized> PartialEq for NonNull<T>`

[src]

####

`fn eq(&self, other: &Self) -> bool`

[src]

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

####

`#[must_use] fn ne(&self, other: &Rhs) -> bool`

1.0.0
[src]

This method tests for `!=`.

###

`impl<T: ?Sized> Ord for NonNull<T>`

[src]

####

`fn cmp(&self, other: &Self) -> Ordering`

[src]

This method returns an `Ordering` between `self` and `other`. Read more

####

`fn max(self, other: Self) -> Self where Self: Sized,`

1.21.0
[src]

Compares and returns the maximum of two values. Read more

####

`fn min(self, other: Self) -> Self where Self: Sized,`

1.21.0
[src]

Compares and returns the minimum of two values. Read more

###

`impl<T: ?Sized> PartialOrd for NonNull<T>`

[src]

####

`fn partial_cmp(&self, other: &Self) -> Option<Ordering>`

[src]

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

####

`#[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: ?Sized> Hash for NonNull<T>`

[src]

####

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

[src]

Feeds this value into the given [`Hasher`]. Read more

####

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

1.3.0
[src]

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

###

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

[src]

####

`fn from(reference: &'a mut T) -> Self`

[src]

Performs the conversion.

###

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

[src]

####

`fn from(reference: &'a T) -> Self`

[src]

Performs the conversion.

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g. `str,u8` or `String,struct:Vec,test`)