Struct tagged_pointer::TaggedPtr

#[repr(transparent)]pub struct TaggedPtr<T, Bits>(_);

A tagged pointer: a space-efficient representation of a pointer and integer tag.

This type stores a pointer and an integer tag without taking up more space than a normal pointer (unless the fallback implementation is used; see the module documentation).

The tagged pointer conceptually holds a NonNull<T> and a certain number of bits of an integer tag.

Bits should be a type-level unsigned integer from the typenum crate. It specifies how many bits are used for the tag. The alignment of T must be large enough to store this many bits; see Self::new.

Implementations

impl<T, Bits: Unsigned> TaggedPtr<T, Bits>

pub fn new(ptr: NonNull<T>, tag: usize) -> Self

Creates a new tagged pointer. Only the lower Bits::USIZE bits of tag are stored.

Panics

This method panics if the alignment of T is less than 2 to the power of Bits::USIZE. This ensures that all properly aligned pointers to T will be aligned enough to store the specified number of bits of the tag.

ptr should be “dereferencable” in the sense defined by core::ptr. If it is not, this method or other methods of TaggedPtr may panic.

It is recommended that ptr be properly aligned (i.e., aligned to at least mem::align_of::<T>()), but it may have a smaller alignment. However, if its alignment is not at least 2 to the power of Bits::USIZE, this method may panic.

pub fn get(self) -> (NonNull<T>, usize)

Gets the pointer and tag stored by the tagged pointer. If you need both the pointer and tag, this method may be more efficient than calling Self::ptr and Self::tag separately.

Panics

If the pointer provided to Self::new wasn’t “dereferencable”, this method may panic.

pub fn ptr(self) -> NonNull<T>

Gets the pointer stored by the tagged pointer, without the tag. Equivalent to self.get().0.

Panics

If the pointer provided to Self::new wasn’t “dereferencable”, this method may panic.

pub fn tag(self) -> usize

Gets the tag stored by the tagged pointer. Equivalent to self.get().1.

Panics

If the pointer provided to Self::new wasn’t “dereferencable”, this method may panic.

Trait Implementations

impl<T, Bits> Clone for TaggedPtr<T, Bits>

fn clone(&self) -> Self

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<T, Bits> Copy for TaggedPtr<T, Bits>

impl<T, Bits: Unsigned> Debug for TaggedPtr<T, Bits>

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

Formats the value using the given formatter.

impl<T, Bits> Eq for TaggedPtr<T, Bits>

impl<T, Bits> Hash for TaggedPtr<T, Bits>

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

Feeds this value into the given Hasher.

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

Feeds a slice of this type into the given Hasher.

impl<T, Bits> Ord for TaggedPtr<T, Bits>

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

This method returns an Ordering between self and other.

#[must_use]pub fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

#[must_use]pub fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

#[must_use]pub fn clamp(self, min: Self, max: Self) -> Self

Restrict a value to a certain interval.

impl<T, Bits> PartialEq<TaggedPtr<T, Bits>> for TaggedPtr<T, Bits>

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

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

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

This method tests for !=.

impl<T, Bits> PartialOrd<TaggedPtr<T, Bits>> for TaggedPtr<T, Bits>

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

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

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

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

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

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

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

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

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

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