Struct SmallArena

Source

pub struct SmallArena<'tag, T> { /* private fields */ }

Expand description

A “Small” arena based on a resizable slice (i.e. a Vec) that can be indexed with 32-bit Idx32s. This can help reduce memory overhead when using many pointer-heavy objects on 64-bit systems.

You can obtain an instance of this type by calling mk_arena.

Implementations§

Source §

impl<'tag, T> SmallArena<'tag, T>

Source

pub unsafe fn new(tag: InvariantLifetime<'tag>, capacity: usize) -> Self

create a new SmallArena. Don’t do this manually. Use the in_arena macro instead.

§Safety

The whole tagged indexing trick relies on the 'tag you give to this constructor. You must never use this value in another arena, lest you might be able to mix up the indices of the two, which could lead to out of bounds access and thus Undefined Behavior!

Source

pub unsafe fn from_vec(tag: InvariantLifetime<'tag>, data: Vec<T>) -> Self

move a Vec into a SmallArena. This is unlikely to be useful to you, it’s an implementation detail of the recycle_arena! macro.

Source

pub fn into_inner(self) -> Vec<T>

consume the arena and get the data out

Source

pub fn try_add(&mut self, item: T) -> Result<Idx32<'tag>, CapacityExceeded<T>>

Add an item to the arena, get an index or CapacityExceeded back.

Source

pub fn add(&mut self, item: T) -> Idx32<'tag>

Add an item to the arena, get an index back.

Source

pub fn as_slice(&self) -> &[T]

View the current elements as a slice.

§Examples

mk_arena!(arena);
let _ = arena.add("Hi!");
let _ = arena.add("Bye!");
assert_eq!(&["Hi!", "Bye!"], arena.as_slice());

Source

pub fn as_mut_slice(&mut self) -> &mut [T]

Mutate the current elements as a slice.

§Examples

mk_arena!(arena);
let one = arena.add(1u32);
let two = arena.add(2);
arena.as_mut_slice().into_iter().for_each(|i| *i += 1);
assert_eq!(arena[one], 2);
assert_eq!(arena[two], 3);