Crate fastarena 

A zero-dependency bump-pointer arena allocator with RAII transactions, nested savepoints, and ArenaVec.

Features

• O(1) amortised allocation — bump pointer advance with a single bounds check
• Checkpoint / rewind — snapshot arena state in O(1), undo allocations
• RAII transactions — auto-rollback on drop, explicit commit via mem::forget
• Transaction budget — cap arena bytes per transaction (tracks inline sizes only; heap allocations inside values are not counted)
• Zero-cost reset — reuse all allocated blocks without OS calls
• ArenaVec<T> — append-only growable vector backed by arena memory

Quick Start

use fastarena::Arena;

let mut arena = Arena::new();
let x = arena.alloc(42u64);
let s = arena.alloc_str("hello");
arena.reset(); // zero-cost reset

Feature Flags

Flag	Default	Description
drop-tracking	Off	Run destructors in LIFO order on reset/rewind

Macros

arenavec

Creates an ArenaVec backed by the given arena.

Structs

Arena

A bump-pointer arena allocator with RAII transactions, checkpoint/rewind, and zero-cost reset/reuse.

ArenaStats

A snapshot of arena memory usage returned by super::allocator::Arena::stats.

ArenaVec

An append-only growable vector backed by arena memory.

ArenaVecIntoIter

Owning iterator over an ArenaVec. Drains elements front-to-back and drops any remaining elements (in LIFO order) when the iterator itself is dropped.

Checkpoint

An opaque snapshot of arena state used by Arena::rewind.

Transaction

A scoped RAII transaction over an Arena.

TxnDiff

Allocation metrics for a single transaction scope, returned by Transaction::diff.

Enums

TryReserveError

Error returned by ArenaVec::try_reserve when allocation fails.

TxnStatus

Outcome of Transaction::commit or Transaction::rollback.