Struct internment::LocalIntern

pub struct LocalIntern<T> { /* fields omitted */ }

A pointer to a thread-local interned object.

The interned object will be held in memory as long as the thread is still running. Thus you can arrange a crude sort of arena allocation by running code using LocalIntern on a temporary thread. Lifetime issues are as simple as when using Intern. LocalIntern differs in that it is neigher Send nor Share, so it cannot be used in a multithreaded manner. On the benefit side, it is faster than Intern, and the memory can be freed (by running in a temporary thread).

Example

use internment::LocalIntern;

let x = LocalIntern::new("hello");
let y = LocalIntern::new("world");
assert_ne!(x, y);
assert_eq!(x, LocalIntern::new("hello"));
assert_eq!(*x, "hello"); // dereference a LocalIntern like a pointer

Example with owned String data

use internment::LocalIntern;

let x = LocalIntern::new("hello".to_string());
let y = LocalIntern::<String>::from("world");
assert_ne!(x, y);
assert_eq!(x, LocalIntern::from("hello"));
assert_eq!(&*x, "hello"); // dereference a LocalIntern like a pointer

Implementations

impl<T: Eq + Hash + 'static> LocalIntern<T>

pub fn new(val: T) -> LocalIntern<T>

Intern a value in a thread-local way. If this value has not previously been interned, then new will allocate a spot for the value on the heap. Otherwise, it will return a pointer to the object previously allocated.

Note that LocalIntern::new is a bit slow, since it needs to check a HashMap protected by a Mutex.

pub fn from<'a, Q: ?Sized + Eq + Hash + 'a>(val: &'a Q) -> LocalIntern<T> where
    T: Borrow<Q> + From<&'a Q>, 

Intern a value from a reference in a thread-local way (fastest).

If this value has not previously been interned, then new will allocate a spot for the value on the heap and generate that value using T::from(val).

pub fn num_objects_interned() -> usize

See how many objects have been interned. This may be helpful in analyzing memory use.

Trait Implementations

impl<T> AsRef<T> for LocalIntern<T>

fn as_ref(&self) -> &T

Performs the conversion.

impl<T> Borrow<T> for LocalIntern<T>

fn borrow(&self) -> &T

Immutably borrows from an owned value.

impl<T> Clone for LocalIntern<T>

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> Copy for LocalIntern<T>

An LocalIntern is Copy, which is unusal for a pointer. This is safe because we never free the data pointed to by an LocalIntern until the thread itself is destroyed.

impl<T: Debug> Debug for LocalIntern<T>

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

Formats the value using the given formatter.

impl<T: Eq + Hash + Default + 'static> Default for LocalIntern<T>

fn default() -> LocalIntern<T>

Returns the “default value” for a type.

impl<T> Deref for LocalIntern<T>

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &T

Dereferences the value.

impl<T: Display> Display for LocalIntern<T>

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

Formats the value using the given formatter.

impl<T> Eq for LocalIntern<T>

impl<T: Eq + Hash + 'static> From<T> for LocalIntern<T>

fn from(t: T) -> Self

Performs the conversion.

impl<T> Hash for LocalIntern<T>

The hash implementation returns the hash of the pointer value, not the hash of the value pointed to. This should be irrelevant, since there is a unique pointer for every value, but it is observable, since you could compare the hash of the pointer with hash of the data itself.

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: Ord> Ord for LocalIntern<T>

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> PartialEq<LocalIntern<T>> for LocalIntern<T>

fn eq(&self, other: &LocalIntern<T>) -> 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: PartialOrd> PartialOrd<LocalIntern<T>> for LocalIntern<T>

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

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

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

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

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

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

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

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

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

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

impl<T> Pointer for LocalIntern<T>

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

Formats the value using the given formatter.