Varintes

Encode and decode numbers per unsigned-varint specification, exposed as pure ES Module.

It is fast: 1.5x - 10x times faster than original varint module.

History

We started this package as an ES Module version of varint package. Then we added few helpers used by existing varint package consumers.

Installation

npm install varintes

Usage

To encode a number as varint use encode function:

import * as varintes from "varintes";
const bytes = varintes.encode(4242); // Uint8Array(2) [ 146, 33 ]

To decode varint from bytes, use decode function. It returns decoded number, and amount of bytes read to decode. The bytes read number may be used to continue decoding of a long bytes sequence.

import * as varintes from "varintes";
const [number, bytesRead] = varintes.decode(new Uint8Array([146, 33])); // number = 4242, bytesRead = 2

encodingLength gives you length in bytes of a number when encoded as varint:

import * as varintes from "varintes";
const length = varintes.encodingLength(4242); // 2

Let's call tight packing of varints an encoding where varints' bytes follow each other. There are two functions for tight packing and unpacking provided - encodePach and decodePack:

import * as varintes from "varintes";
const packed = varintes.encodePack([1, 17, 4242]); // Uint8Array(4) [ 1, 17, 146, 33 ]
const unpacked = varintes.decodePack(packed); // [1, 17, 4242]

To Do

• [x] Faster decode by loop unrolling

License

MIT or APACHE-2.0