vle-integers v0.1.1

JavaScript Variable Length Encoded Integers

Dynamically encodes a number into N bytes:

0->63 -- 1 bytes
->8,191 -- 2 bytes
->1,048,575 -- 3 bytes
->2^27-1 -- 4 bytes
->2^31-1 -- 5 bytes

Important: 2^31 - 1 is currently the largest number this library can encode. This is not a hard limitation, it's just that it requires a bit more logic after that point and I don't currently need numbers that large myself so I didn't write it. If you need this open a bug report (or better yet a pull request)!

I could make an unsigned version, but I don't need it myself -- open an issue if you need this.

Usage

var encode  = require('vle-integers').encode;
var decode  = require('vle-integers').decode;

var encode  = encode(123);
var decoded = decode(123);

Decode Method

The decode method will only decode a specific number, meaning that if you attempt to decode something like:

var decoded = encode('123') + 'asdf'; // yields 123

It will work correctly. It will also properly decode Buffers. There is an optional offset that you can use to tell it where to start decodeing from:

var encoded = 'asdf' + encode(123);
var decoded = decode(encoded, 4); // yields {number: 123, offset:6}

Encode Method

Encoding always returns a string. If you want a Buffer, create one by passing the result to a Buffer and being sure to set the encoding as ascii:

var encode  = require('vle-integers').encode;
var encoded = encode(123);

var buf = new Buffer(encoded, 'ascii');

// or

buf.write(encoded, 0, 'ascii');

There is also an optional encode.array method that returns an array of numbers representing the ascii value of each byte.