bufferutil is what makes ws fast. It provides some utilities to efficiently perform some operations such as masking and unmasking the data payload of WebSocket frames.

npm install bufferutil --save-optional

The --save-optional flag tells npm to save the package in your package.json under the optionalDependencies key.

The module exports 3 different functions.

Merges an array of buffers into a target buffer.

• target - The target buffer.
• list - An array containing the Buffer instances to merge.

'use strict';

const bufferUtil = require('bufferutil');
const crypto = require('crypto');

const target = Buffer.allocUnsafe(10);

bufferUtil.merge(target, [crypto.randomBytes(5), crypto.randomBytes(5)]);

Masks a buffer using the given masking-key as specified by the WebSocket protocol.

• source - The buffer to mask.
• mask - A buffer representing the masking-key.
• output - The buffer where to store the result.
• offset - The offset at which to start writing.
• length - The number of bytes to mask.

'use strict';

const bufferUtil = require('bufferutil');
const crypto = require('crypto');

const source = crypto.randomBytes(10);
const mask = crypto.randomBytes(4);

bufferUtil.mask(source, mask, source, 0, source.length);

Unmasks a buffer using the given masking-key as specified by the WebSocket protocol.

• buffer - The buffer to unmask.
• mask - A buffer representing the masking-key.

'use strict';

const bufferUtil = require('bufferutil');
const crypto = require('crypto');

const buffer = crypto.randomBytes(10);
const mask = crypto.randomBytes(4);

bufferUtil.unmask(buffer, mask);

MIT