1.25.0[][src]Struct std::ptr::NonNull

#[repr(transparent)]
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>
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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
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Creates a new NonNull.

Safety

ptr must be non-null.

Creates a new NonNull if ptr is non-null.

Acquires the underlying *mut pointer.

Important traits for &'_ mut I

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 I

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().

Cast to a pointer of another type

Trait Implementations

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

impl<'a, T> From<&'a T> for NonNull<T> where
    T: ?Sized
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Performs the conversion.

impl<T> From<Unique<T>> for NonNull<T> where
    T: ?Sized
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Performs the conversion.

impl<T> Copy for NonNull<T> where
    T: ?Sized
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impl<T> !Sync for NonNull<T> where
    T: ?Sized
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NonNull pointers are not Sync because the data they reference may be aliased.

impl<T> !Send for NonNull<T> where
    T: ?Sized
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NonNull pointers are not Send because the data they reference may be aliased.

impl<T> Hash for NonNull<T> where
    T: ?Sized
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Feeds this value into the given [Hasher]. Read more

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

impl<T> Clone for NonNull<T> where
    T: ?Sized
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Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

impl<T> PartialOrd<NonNull<T>> for NonNull<T> where
    T: ?Sized
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This method returns an ordering between self and other values if one exists. Read more

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

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

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

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

impl<T> Ord for NonNull<T> where
    T: ?Sized
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This method returns an Ordering between self and other. Read more

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

impl<T> Pointer for NonNull<T> where
    T: ?Sized
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Formats the value using the given formatter.

impl<T> Eq for NonNull<T> where
    T: ?Sized
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impl<T> Debug for NonNull<T> where
    T: ?Sized
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Formats the value using the given formatter. Read more

impl<T> PartialEq<NonNull<T>> for NonNull<T> where
    T: ?Sized
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This method tests for self and other values to be equal, and is used by ==. Read more

This method tests for !=.

impl<T, U> CoerceUnsized<NonNull<U>> for NonNull<T> where
    T: Unsize<U> + ?Sized,
    U: ?Sized
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impl<T: RefUnwindSafe + ?Sized> UnwindSafe for NonNull<T>
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Blanket Implementations

impl<T, U> TryFrom for T where
    T: From<U>, 
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🔬 This is a nightly-only experimental API. (try_from #33417)

The type returned in the event of a conversion error.

🔬 This is a nightly-only experimental API. (try_from #33417)

Performs the conversion.

impl<T> From for T
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Performs the conversion.

impl<T, U> TryInto for T where
    U: TryFrom<T>, 
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🔬 This is a nightly-only experimental API. (try_from #33417)

The type returned in the event of a conversion error.

🔬 This is a nightly-only experimental API. (try_from #33417)

Performs the conversion.

impl<T, U> Into for T where
    U: From<T>, 
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Performs the conversion.

impl<T> Borrow for T where
    T: ?Sized
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Important traits for &'_ mut I

Immutably borrows from an owned value. Read more

impl<T> BorrowMut for T where
    T: ?Sized
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Important traits for &'_ mut I

Mutably borrows from an owned value. Read more

impl<T> Any for T where
    T: 'static + ?Sized
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🔬 This is a nightly-only experimental API. (get_type_id #27745)

this method will likely be replaced by an associated static

Gets the TypeId of self. Read more

impl<T> ToOwned for T where
    T: Clone
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Creates owned data from borrowed data, usually by cloning. Read more

🔬 This is a nightly-only experimental API. (toowned_clone_into #41263)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more