Struct UnboundedSlab 

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

Growable slab allocator.

Uses independent chunks for growth — no copying when the slab grows.

Const Construction

Supports const construction via new() followed by runtime initialization via init(). This enables use with thread_local! using the const { } block syntax for zero-overhead TLS access.

thread_local! {
    static SLAB: Slab<MyType> = const { Slab::new() };
}

// Later, at runtime:
SLAB.with(|s| s.init(4096));

For direct usage, prefer with_chunk_capacity().

Implementations

impl<T> Slab<T>

pub const fn new() -> Slab<T>

Creates an empty, uninitialized slab.

This is a const function that performs no allocation. Call init() to configure chunk capacity before use.

For direct usage, prefer with_chunk_capacity().

Example

// For use with thread_local! const initialization
thread_local! {
    static SLAB: Slab<u64> = const { Slab::new() };
}

pub fn with_chunk_capacity(chunk_capacity: usize) -> Slab<T>

Creates a new slab with the given chunk capacity.

Chunks are allocated on-demand when slots are requested.

Panics

Panics if chunk_capacity is zero.

pub fn init(&self, chunk_capacity: usize)

Initializes the slab with the given chunk capacity.

This configures the chunk parameters. Chunks are allocated on-demand when slots are requested. Must be called exactly once before any allocations.

Panics

• Panics if the slab is already initialized (chunk_capacity > 0)
• Panics if chunk_capacity is zero

pub fn is_initialized(&self) -> bool

Returns true if the slab has been initialized.

pub fn capacity(&self) -> usize

Returns the total capacity across all chunks.

pub fn chunk_capacity(&self) -> usize

Returns the chunk capacity.

pub fn chunk_count(&self) -> usize

Returns the number of allocated chunks.

pub fn reserve_chunks(&self, count: usize)

Ensures at least count chunks are allocated.

No-op if the slab already has count or more chunks. Only allocates the difference.

pub fn claim(&self) -> Claim<'_, T>

Claims a slot from the freelist without writing a value.

Always succeeds — grows the slab if needed. The returned [Claim] must be consumed via [Claim::write()] to complete the allocation.

This two-phase allocation enables placement new optimization: the value can be constructed directly into the slot memory.

Example

use nexus_slab::unbounded::Slab;

let slab = Slab::with_chunk_capacity(16);
let claim = slab.claim();
let slot = claim.write(42u64);
assert_eq!(*slot, 42);
// SAFETY: slot was allocated from this slab
unsafe { slab.free(slot) };

pub fn alloc(&self, value: T) -> Slot<T>

Allocates a slot and writes the value.

Always succeeds — grows the slab if needed.

pub unsafe fn free(&self, slot: Slot<T>)

Frees a slot, dropping the value and returning storage to the freelist.

Performance

O(n) where n = chunk count, due to chunk lookup. Typically 1-5 chunks.

Safety

• slot must have been allocated from this slab
• No references to the slot’s value may exist

pub unsafe fn take(&self, slot: Slot<T>) -> T

Frees a slot and returns the value without dropping it.

Performance

O(n) where n = chunk count, due to chunk lookup. Typically 1-5 chunks.

Safety

• slot must have been allocated from this slab
• No references to the slot’s value may exist

Trait Implementations

impl<T> Debug for Slab<T>

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

Formats the value using the given formatter.

impl<T> Default for Slab<T>

fn default() -> Slab<T>

Returns the “default value” for a type.

impl<T> SlabStore for Slab<T>

type Item = T

The type stored in each slot.

fn alloc(&self, value: T) -> Slot<T>

Allocates a slot with the given value.

unsafe fn free(&self, slot: Slot<T>)

Drops the value and returns the slot to the freelist.

unsafe fn take(&self, slot: Slot<T>) -> T

Moves the value out and returns the slot to the freelist.

unsafe fn free_ptr(&self, ptr: *mut SlotCell<T>)

Returns a slot to the freelist by raw pointer.