Struct Arena 

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

A generational arena allocator.

Provides O(1) allocation, deallocation, and access with generation-based use-after-free detection. All operations are safe Rust.

Type Parameter

T is the type of values stored in the arena. For the DOM, this will be NodeData.

Examples

use tinyxml2::arena::Arena;

let mut arena: Arena<String> = Arena::new();

// Allocate
let id = arena.alloc("hello".to_string());
assert_eq!(arena.get(id), Some(&"hello".to_string()));

// Deallocate
let removed = arena.dealloc(id);
assert_eq!(removed, Some("hello".to_string()));

// Stale ID returns None
assert_eq!(arena.get(id), None);

Implementations

impl<T> Arena<T>

pub fn new() -> Self

Creates a new, empty arena.

pub fn with_capacity(capacity: usize) -> Self

Creates a new arena with the specified capacity pre-allocated.

pub fn alloc(&mut self, value: T) -> NodeId

Allocates a new slot and stores the value, returning its NodeId.

If a previously-deallocated slot is available, it will be reused. Otherwise, a new slot is appended.

Time complexity: O(1) amortized.

pub fn dealloc(&mut self, id: NodeId) -> Option<T>

Deallocates the slot identified by id, returning the stored value.

Returns None if the ID is invalid (wrong generation, out of bounds, or already deallocated).

The slot’s generation is incremented so that any remaining copies of this NodeId become stale.

Time complexity: O(1).

pub fn get(&self, id: NodeId) -> Option<&T>

Returns a reference to the value at id, or None if the ID is invalid.

Time complexity: O(1).

pub fn get_mut(&mut self, id: NodeId) -> Option<&mut T>

Returns a mutable reference to the value at id, or None if invalid.

Time complexity: O(1).

pub fn len(&self) -> usize

Returns the number of currently occupied slots.

pub fn is_empty(&self) -> bool

Returns true if no slots are currently occupied.

pub fn capacity(&self) -> usize

Returns the total capacity (occupied + vacant slots).

pub fn clear(&mut self)

Removes all items from the arena and resets all state.

All existing NodeId values become invalid after this call.

pub fn iter(&self) -> ArenaIter<'_, T>

Returns an iterator over all occupied (NodeId, &T) pairs.

pub fn iter_mut(&mut self) -> ArenaIterMut<'_, T>

Returns a mutable iterator over all occupied (NodeId, &mut T) pairs.

pub fn contains(&self, id: NodeId) -> bool

Returns true if the given NodeId currently refers to a live entry.

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.

impl<'a, T> IntoIterator for &'a Arena<T>

type Item = (NodeId, &'a T)

The type of the elements being iterated over.

type IntoIter = ArenaIter<'a, T>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<'a, T> IntoIterator for &'a mut Arena<T>

type Item = (NodeId, &'a mut T)

The type of the elements being iterated over.

type IntoIter = ArenaIterMut<'a, T>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.