Struct Arena 

pub struct Arena<T> { /* private fields */ }

A simple arena allocator with generation-based indices.

This arena provides stable indices for inserted elements, with generation counters to detect use-after-free errors (ABA problem).

Implementations

impl<T> Arena<T>

pub const fn new() -> Self

Creates a new empty arena.

pub fn with_capacity(capacity: usize) -> Self

Creates a new arena with the specified capacity.

pub const fn len(&self) -> usize

Returns the number of occupied slots.

pub const fn is_empty(&self) -> bool

Returns true if the arena has no occupied slots.

pub fn insert(&mut self, value: T) -> ArenaIndex

Inserts a value into the arena and returns its index.

pub fn insert_with<F>(&mut self, f: F) -> ArenaIndex

where F: FnOnce(ArenaIndex) -> T,

Inserts a value produced by f into the arena and returns its index.

The closure receives the assigned ArenaIndex, allowing callers to construct records that embed their final ID without placeholder updates.

pub fn remove(&mut self, index: ArenaIndex) -> Option<T>

Removes the value at the given index and returns it.

Returns None if the index is invalid or the slot is vacant.

pub fn get(&self, index: ArenaIndex) -> Option<&T>

Returns a reference to the value at the given index.

Returns None if the index is invalid or the slot is vacant.

pub fn get_mut(&mut self, index: ArenaIndex) -> Option<&mut T>

Returns a mutable reference to the value at the given index.

Returns None if the index is invalid or the slot is vacant.

pub fn contains(&self, index: ArenaIndex) -> bool

Returns true if the index is valid and points to an occupied slot.

pub fn iter(&self) -> impl Iterator<Item = (ArenaIndex, &T)>

Iterates over all occupied slots.

pub fn iter_mut(&mut self) -> impl Iterator<Item = (ArenaIndex, &mut T)>

Iterates mutably over all occupied slots.

Trait Implementations

impl<T: Debug> Debug for Arena<T>

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

Formats the value using the given formatter.

impl<T> Default for Arena<T>

fn default() -> Self

Returns the “default value” for a type.