Memory utility

by Nicholas C. Zakas

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Description

A JavaScript implementation of dynamic memory using an ArrayBuffer as the memory storage.

Warning: Very experimental right now. May or may not be useful.

Usage

Node.js

Install using npm or yarn:

npm install @humanwhocodes/memory --save

# or

yarn add @humanwhocodes/memory

Import into your Node.js project:

// CommonJS
const { Memory } = require("@humanwhocodes/memory");

// ESM
import { Memory } from "@humanwhocodes/memory";

Deno

Import into your Deno project:

import { Memory } from "https://cdn.skypack.dev/@humanwhocodes/memory?dts";

Browser

It's recommended to import the minified version to save bandwidth:

import { Memory } from "https://cdn.skypack.dev/@humanwhocodes/memory?min";

However, you can also import the unminified version for debugging purposes:

import { Memory } from "https://cdn.skypack.dev/@humanwhocodes/memory";

API

After importing, create a new instance of Memory and pass in an ArrayBuffer to represent your memory:

const memory = new Memory(new ArrayBuffer(64));

// allocate 4 bytes
const address = memory.allocate(4);

// address is 0 if no memory could be allocated
if (address) {

    // write some data into that address - must be a typed array
    memory.write(address, new Uint8Array([1, 2, 3, 4]));

    // read the data back out - returns a Uint8Array
    const data = memory.read(address);

    // free up the mory
    memory.free(address);

} else {
    console.error("Could not allocate memory.");
}

Safety

The Memory class provides safeguards to ensure you aren't accidentally writing or reading data where you shouldn't:

1. allocate() returns 0 when no more memory can be allocated, allowing you to handle out-of-memory issues gracefully.
2. write() throws an error when:
   1. You try to write to address 0.
   2. You try to write to an unallocated address.
   3. The data you're writing is larger than the allocated space.
3. read() throws an error if you attempt to read from an invalid address.
4. free() throws an error if you attempt to free an invalid address.

All of this is to say, it should be difficult to accidentally overwrite memory locations.

Developer Setup

1. Fork the repository
2. Clone your fork
3. Run npm install to setup dependencies
4. Run npm test to run tests

License

Apache 2.0