https://github.com/cristian-5/wall-e

🧮 webassembly allocator, handwritten with 💗 in assemblyscript
https://github.com/cristian-5/wall-e

allocator assemblyscript best-fit free-list webassembly

Last synced: 20 days ago
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🧮 webassembly allocator, handwritten with 💗 in assemblyscript

• Host: GitHub
• URL: https://github.com/cristian-5/wall-e
• Owner: cristian-5
• Created: 2023-09-08T15:31:24.000Z (over 1 year ago)
• Default Branch: main
• Last Pushed: 2023-10-04T17:56:50.000Z (over 1 year ago)
• Last Synced: 2023-10-05T06:08:35.003Z (over 1 year ago)
• Topics: allocator, assemblyscript, best-fit, free-list, webassembly
• Language: TypeScript
• Homepage:
• Size: 7.81 KB
• Stars: 1
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: readme.md

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README

        

# WALL-E



 

🧮 **w**ebassembly **all**ocator,\

💗 **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:

``` ts

export function allocate(s: u32): ptr

```

To free memory, use the `deallocate` function:

```  ts

export function deallocate(p: ptr): void

```

To resize previously allocated memory, use the `reallocate` function:

``` ts

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

```

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

``` ts

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.

``` js

WebAssembly.instantiateStreaming(fetch("wall-e.wasm"))

           .then(({ instance }) => { /* ... */ });

```