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Fast base encoding / decoding of any given alphabet

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base-x

NPM Package Build Status

js-standard-style

Fast base encoding / decoding of any given alphabet using bitcoin style leading zero compression.

WARNING: This module is NOT RFC3548 compliant, it cannot be used for base16 (hex), base32, or base64 encoding in a standards compliant manner.

Example

Base58

var BASE58 = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
var bs58 = require('base-x')(BASE58)

var decoded = bs58.decode('5Kd3NBUAdUnhyzenEwVLy9pBKxSwXvE9FMPyR4UKZvpe6E3AgLr')

console.log(decoded)
// => <Buffer 80 ed db dc 11 68 f1 da ea db d3 e4 4c 1e 3f 8f 5a 28 4c 20 29 f7 8a d2 6a f9 85 83 a4 99 de 5b 19>

console.log(bs58.encode(decoded))
// => 5Kd3NBUAdUnhyzenEwVLy9pBKxSwXvE9FMPyR4UKZvpe6E3AgLr

Alphabets

See below for a list of commonly recognized alphabets, and their respective base.

BaseAlphabet
201
801234567
110123456789a
160123456789abcdef
320123456789ABCDEFGHJKMNPQRSTVWXYZ
32ybndrfg8ejkmcpqxot1uwisza345h769 (z-base-32)
360123456789abcdefghijklmnopqrstuvwxyz
58123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz
620123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ
64ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/
66ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_.!~

How it works

It encodes octet arrays by doing long divisions on all significant digits in the array, creating a representation of that number in the new base. Then for every leading zero in the input (not significant as a number) it will encode as a single leader character. This is the first in the alphabet and will decode as 8 bits. The other characters depend upon the base. For example, a base58 alphabet packs roughly 5.858 bits per character.

This means the encoded string 000f (using a base16, 0-f alphabet) will actually decode to 4 bytes unlike a canonical hex encoding which uniformly packs 4 bits into each character.

While unusual, this does mean that no padding is required and it works for bases like 43.

LICENSE MIT

A direct derivation of the base58 implementation from bitcoin/bitcoin, generalized for variable length alphabets.

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Score

Popularity37/100
Quality97/100
Maintenance100/100

Dependencies