Struct boa_gc::Ephemeron

pub struct Ephemeron<K: Trace + ?Sized + 'static, V: Trace + 'static> { /* private fields */ }

A key-value pair where the value becomes unaccesible when the key is garbage collected.

You can read more about ephemerons on:

• Racket’s page about ephemerons, which gives a brief overview.
• Barry Hayes’ paper “Ephemerons: a new finalization mechanism” which explains the topic in full detail.

Implementations

impl<K: Trace + ?Sized, V: Trace + Clone> Ephemeron<K, V>

pub fn value(&self) -> Option<V>

Gets the stored value of this Ephemeron, or None if the key was already garbage collected.

This needs to return a clone of the value because holding a reference to it between garbage collection passes could drop the underlying allocation, causing an Use After Free.

pub fn key(&self) -> Option<Gc<K>>

Gets the stored key of this Ephemeron, or None if the key was already garbage collected.

pub fn has_value(&self) -> bool

Checks if the Ephemeron has a value.

impl<K: Trace + ?Sized, V: Trace> Ephemeron<K, V>

pub fn new(key: &Gc<K>, value: V) -> Self

Creates a new Ephemeron.

pub fn ptr_eq(this: &Self, other: &Self) -> bool

Returns true if the two Ephemerons point to the same allocation.

Trait Implementations

impl<K: Trace + ?Sized, V: Trace> Clone for Ephemeron<K, V>

fn clone(&self) -> Self

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<K: Debug + Trace + ?Sized + 'static, V: Debug + Trace + 'static> Debug for Ephemeron<K, V>

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

Formats the value using the given formatter.

impl<K: Trace + ?Sized, V: Trace> Drop for Ephemeron<K, V>

fn drop(&mut self)

Executes the destructor for this type.

impl<K: Trace + ?Sized, V: Trace> Finalize for Ephemeron<K, V>

fn finalize(&self)

Cleanup logic for a type.

impl<T: Trace> From<Ephemeron<T, ()>> for WeakGc<T>

fn from(inner: Ephemeron<T, ()>) -> Self

Converts to this type from the input type.

impl<K: Trace + ?Sized, V: Trace> Trace for Ephemeron<K, V>

unsafe fn trace(&self, _tracer: &mut Tracer)

Marks all contained Gcs.

unsafe fn trace_non_roots(&self)

Trace handles located in GC heap, and mark them as non root.

fn run_finalizer(&self)

Runs Finalize::finalize on this object and all contained subobjects.