points-compressor v1.0.8

npm points-compressor

Install

$ npm install points-compressor

Usage

in javascript

const ptComp = require('points-compressor');

const points = [
  {x: 123.123, y: 321.021, z: 1132.0001},
  {x: 163.222, y: 325.322, z: 1135.0201}
]
const compressed = ptComp.compress(points);
const decompressed = ptComp.decompress(compressed);
// R.equals(points, decompressed) must be true
// R means ramdajs

in typescript

import {compress, decompress} from 'points-compressor';

const points: Point[] = [
  {x: 123.123, y: 321.021, z: 1132.0001},
  {x: 163.222, y: 325.322, z: 1135.0201}
]
const compressed: string = compress(points);
const decompressed: Point[] = decompress(compressed);
// R.equals(points, decompressed) must be true
// R means ramdajs

limitation

• left of decimal must be smaller than 65535
• the length of right of decimal must be shorter than 5
• 453.44, 65000.4444, 1.0123 ok
• 77777.1, 123.22223 not ok

Why?

• In my case, this limitation is enough to represent all data
• And it is very easy to implement the functions with such limitations.
• But if you want to exceed such limitation, please let me know by leaving issue on the Github repo.

Compression performance

• 10% ~ 15%
• 4.6kb to 0.6kb
• check by running npm run test

Introduction

In many case of javascript applications, it is common to send arbitrary data using JSON.stringify.
And it is often inefficient to stringify a data which contains numbers.

For example

let num = 5555.555;

The variable above occupies at most 4byte in memory.

let num2 = '5555.555';

But num2 occupies at least 16bytes(8 characters, 2bytes each character).

In my case, there are many numbers in message packet. So it is necessary to compress that kind of packets.

Point

interface Point {
  [axis: string]: number
}

let point1 = {'x': 111.234, 'y': 1455.01, 'z': 1993.134};

Interfaces

compress

(points: Point[], axes?: string[]) => string;

decompress

(compressed: string) => Point[];