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

Methods

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 num_objects_interned(&self) -> usize

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

Trait Implementations

impl<T: Debug> Fits64 for LocalIntern<T>

The Fits64 implementation for LocalIntern<T> is designed to normally give (relatively) small numbers, by XORing with a fixed pointer that is also on the heap. This should make the most significant bits of the resulting u64 be zero, which will mean that Set64 (which is space-efficient in storing small integers) can store this result in fewer than 8 bytes.

unsafe fn from_u64(x: u64) -> Self

Convert back from a u64. This is unsafe, since it is only infallible (and lossless) if the u64 originally came from type Self.

fn to_u64(self) -> u64

Convert to a u64. This should be infallible.

fn test_fits64(self) -> bool

verify that the conversion is lossless

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

Important traits for &'a mut R

impl<'a, R> Read for &'a mut R where
    R: Read + ?Sized, impl<'a, W> Write for &'a mut W where
    W: Write + ?Sized, impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;

fn as_ref(&self) -> &T

Performs the conversion.

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

Important traits for &'a mut R

impl<'a, R> Read for &'a mut R where
    R: Read + ?Sized, impl<'a, W> Write for &'a mut W where
    W: Write + ?Sized, impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;

fn borrow(&self) -> &T

Immutably borrows from an owned value.

impl<T> Deref for LocalIntern<T>

type Target = T

The resulting type after dereferencing.

Important traits for &'a mut R

impl<'a, R> Read for &'a mut R where
    R: Read + ?Sized, impl<'a, W> Write for &'a mut W where
    W: Write + ?Sized, impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;

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> Pointer for LocalIntern<T>

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

Formats the value using the given formatter.

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

fn from(t: T) -> Self

Performs the conversion.

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

fn default() -> LocalIntern<T>

Returns the "default value" for a type.

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].

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

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

impl<T> PartialEq 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 ==.

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

This method tests for !=.

impl<T> Eq for LocalIntern<T>

impl<T: PartialOrd> PartialOrd 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: Ord> Ord for LocalIntern<T>

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

This method returns an Ordering between self and other.

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

Compares and returns the maximum of two values.

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

Compares and returns the minimum of two values.

impl<T: Serialize> Serialize for LocalIntern<T>

fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error>

Serialize this value into the given Serde serializer.

impl<'de, T: Eq + Hash + 'static + Deserialize<'de>> Deserialize<'de> for LocalIntern<T>

fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error>

Deserialize this value from the given Serde deserializer.

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

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

Formats the value using the given formatter.

impl<T> Clone for LocalIntern<T>

fn clone(&self) -> Self

Returns a copy of the value.

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.