# base-x

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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

``` javascript
var BASE58 = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
import basex from 'base-x'
var bs58 = basex(BASE58)

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

console.log(decoded)
// => Uint8Array(33) [
//   128, 237, 219, 220,  17, 104, 241, 218,
//   234, 219, 211, 228,  76,  30,  63, 143,
//    90,  40,  76,  32,  41, 247, 138, 210,
//   106, 249, 133, 131, 164, 153, 222,  91,
//    25
// ]

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

### Alphabets

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

Base | Alphabet
------------- | -------------
2 | `01`
8 | `01234567`
11 | `0123456789a`
16 | `0123456789abcdef`
32 | `0123456789ABCDEFGHJKMNPQRSTVWXYZ`
32 | `ybndrfg8ejkmcpqxot1uwisza345h769` (z-base-32)
36 | `0123456789abcdefghijklmnopqrstuvwxyz`
58 | `123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz`
62 | `0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ`
64 | `ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/`
67 | `ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_.!~`


## 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](LICENSE)
A direct derivation of the base58 implementation from [`bitcoin/bitcoin`](https://github.com/bitcoin/bitcoin/blob/f1e2f2a85962c1664e4e55471061af0eaa798d40/src/base58.cpp),  generalized for variable length alphabets.
