WALL-E

🧮 webassembly allocator,
💗 handwritten with love in assemblyscript.

Strategy:

The strategy employs a straightforward bump allocation approach while efficiently managing freed blocks through a linked list encoded within each block's header.
For every allocated block, an 8-byte header is initially reserved to store both the logical and effective sizes. When a block is later freed, this header is repurposed to hold the effective pointer to the next free block and the effective size.
Fragmentation is minimized through a "best-fit" model, where the allocator seeks out the free block with the smallest size equal to or greater than the requested size but never exceeding 125% of the space request. The effective size, which excludes the header size, represents the actual usable content size, while the logical size is the size requested by the user.

+-< effective pointer             +-< logical pointer
!                                 !
+----------------+----------------+--------------------------------------+
|  logical size  | effective size | ... allocated data ................. |
|----------------+----------------+--------------------------------------+
|  next block *  | effective size | ... unallocated data ............... |
+----------------+----------------+--------------------------------------+

API Usage:

To allocate memory, use the allocate function:

export function allocate(s: u32): ptr

To free memory, use the deallocate function:

export function deallocate(p: ptr): void

To resize previously allocated memory, use the reallocate function:

export function reallocate(p: ptr, s: u32): ptr

To get the size of previously allocated sections, use the size function:

export function size(p: ptr): u32

⚠️ Warning: Allocations are not zeroed out, memory is not aligned, and the allocator is not thread-safe.

⛔ Critical: If you intend to use this library, DO NOT, under any circumstances, access directly raw unmanaged memory.

WebAssembly.instantiateStreaming(fetch("wall-e.wasm"))
           .then(({ instance }) => { /* ... */ });