JavaScript Base32 implementation

base32.js

// This file is licensed under LGPLv3
// (c) teidesu 2020
const alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567'
const padLength = [0, 1, 3, 4, 6]
const padChar = '='

function encode (buf) {
    let arr = [...buf]
    let len = arr.length
    let ret = ''
    let i = 0

    while (arr.length % 5) arr.push(0)

    while (i < len) {
        let c1 = arr[i++]
        let c2 = arr[i++]
        let c3 = arr[i++]
        let c4 = arr[i++]
        let c5 = arr[i++]

        ret += alphabet[(c1 >> 3)]
        ret += alphabet[((c1 & 0x07) << 2) | (c2 >> 6)]
        ret += alphabet[((c2 & 0x3F) >> 1)]
        ret += alphabet[((c2 & 0x01) << 4) | (c3 >> 4)]
        ret += alphabet[((c3 & 0x0F) << 1) | (c4 >> 7)]
        ret += alphabet[((c4 & 0x7F) >> 2)]
        ret += alphabet[((c4 & 0x03) << 3) | (c5 >> 5)]
        ret += alphabet[(c5 & 0x1F)]
    }

    if (i > len) {
        i = padLength[i - len]
        ret = ret.substr(0, ret.length - i)
        while (ret.length % 8 !== 0) ret += padChar
    }

    return ret
}

function decode (str) {
    let ret = []
    let len = str.length
    let bits = 0
    let charBuffer = 0

    while (len > 0 && str[len - 1] === padChar) --len

    for (let i = 0; i < len; i++) {
        charBuffer = (charBuffer << 5) | alphabet.indexOf(str[i])

        bits += 5
        if (bits >= 8) {
            ret.push((charBuffer >> (bits - 8)) & 0xff)
            bits -= 8
        }
    }

    return Buffer.from(ret)
}

module.exports = {
    encode,
    decode
}