Struct TaggedRef

pub struct TaggedRef<'a, T, const BITS: usize>(/* private fields */);

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

This type behaves like TaggedPtr but with a reference instead of a raw pointer.

BITS specifies how many bits are used for the tag. The alignment of T must be large enough to store this many bits: if BITS is larger than the base-2 logarithm of the alignment of T¹, panics or compilation errors will occur.

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1. Because alignment is always a power of 2, this is equal to align_of::<T>().trailing_zeros(). ↩

Implementations

impl<'a, T, const BITS: usize> TaggedRef<'a, T, BITS>

pub fn new(reference: &'a T, tag: usize) -> Self

Creates a new tagged reference. Only the lower BITS bits of tag are stored.

impl<T, const BITS: usize> TaggedRef<'_, T, BITS>

pub const BITS: u32

The number of tag bits that this tagged reference can store.

pub const MAX_TAG: usize

The maximum tag (inclusive) that this tagged reference can store. Equal to (1 << BITS) - 1 (i.e., one less than 2 to the power of BITS).

impl<'a, T, const BITS: usize> TaggedRef<'a, T, BITS>

pub unsafe fn new_unchecked(reference: &'a T, tag: usize) -> Self

Equivalent to Self::new but without some runtime checks.

Safety

tag cannot be greater than Self::MAX_TAG.

pub fn get(self) -> (&'a T, usize)

Gets the reference and tag stored by the tagged reference.

pub fn get_ref(self) -> &'a T

Gets the reference stored by the tagged reference, without the tag.

Equivalent to self.get().0.

pub fn set_ref(&mut self, reference: &'a T)

Sets the reference without modifying the tag.

This method is equivalent to:

*self = self.with_ref(reference);

Because this method mutates the tagged reference in-place, the new reference must have the exact same lifetime, 'a. As a consequence, any data currently borrowed for 'a by the old reference will remain borrowed even once the reference is updated.

Self::with_ref may be more flexible in some situations, as it returns a new tagged reference that can have a different lifetime.

pub fn with_ref(self, reference: &T) -> TaggedRef<'_, T, BITS>

Creates a new tagged reference with the same tag but a different reference.

This method is equivalent to:

TaggedRef::new(reference, self.tag())

pub fn tag(self) -> usize

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

pub fn set_tag(&mut self, tag: usize)

Sets the tag without modifying the reference.

This method is equivalent to:

*self = Self::new(self.get_ref(), tag);

Trait Implementations

impl<T, const BITS: usize> AsRef<T> for TaggedRef<'_, T, BITS>

fn as_ref(&self) -> &T

Converts this type into a shared reference of the (usually inferred) input type.

impl<T, const BITS: usize> Clone for TaggedRef<'_, T, BITS>

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T, const BITS: usize> Debug for TaggedRef<'_, T, BITS>

where T: Debug,

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

Formats the value using the given formatter.

impl<T, const BITS: usize> Hash for TaggedRef<'_, T, BITS>

where T: Hash,

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

Hashes self.get().

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

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<T, const BITS: usize> Ord for TaggedRef<'_, T, BITS>

where T: Ord,

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

Returns self.get().cmp(&other.get()).

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

where Self: Sized,

Compares and returns the maximum of two values.

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

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl<T, const BITS: usize> PartialEq for TaggedRef<'_, T, BITS>

where T: PartialEq,

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

Returns self.get() == other.get().

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T, const BITS: usize> PartialOrd for TaggedRef<'_, T, BITS>

where T: PartialOrd,

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

Returns self.get().partial_cmp(&other.get()).

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

Tests less than (for self and other) and is used by the < operator.

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

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

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

Tests greater than (for self and other) and is used by the > operator.

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

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

impl<T, const BITS: usize> Pointer for TaggedRef<'_, T, BITS>

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

Formats the value using the given formatter.

impl<T, const BITS: usize> Copy for TaggedRef<'_, T, BITS>

impl<T, const BITS: usize> Eq for TaggedRef<'_, T, BITS>

where T: Eq,

impl<T, const BITS: usize> Send for TaggedRef<'_, T, BITS>

where T: Sync,

impl<T, const BITS: usize> Sync for TaggedRef<'_, T, BITS>

where T: Sync,