b32encode.js

/*!
 * Author: Baptiste MOINE <[email protected]>
 * Project: OTP QR-Code Generator
 * Homepage: https://vps.bmoine.fr/totp-qrcode/
 * Released: 17/04/2017
 *
 * Based on http://www.herongyang.com/Encoding/Base32-Encoding-Algorithm.html
 *
 * Base32 encoding process:
 *     0. Get input string + remove carriage return and new line;
 *     1. Parse bytes from input string;
 *     2. Add padding to divide input bytes to 5-bytes blocks;
 *     3. Create 5-bits groups;
 *     4. Map each group to one printable character based on the Base32 character set;
 *     5. Override characters that aren't based on the input string, but padding;
 *     6. (Facultative) Add padding to create 8-chars blocks;
 *     7. Return the encoded string.
 */
function b32encode(str, padding) {
    var opts = {
            'alphabet': 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567',
            'pad': '=',
            'padding': (padding === true) && true || false
        },
        str = str && str.toString().split('\r')[0].split('\n')[0] || '';  // 0
    var left = str.length % 5;  // 5

    // 1
    var out = (function(str) {
        var bits = [];

        for (var i = 0; i < str.length; ++i) {
            bits[i] = ('000000000' + (str[i].charCodeAt(0).toString(2))).substr(-8);
        }

        return bits;
    })(str.split(''));

    // 2
    out = (function(bits) {
        var len = bits.length,
            pad = '00000000';
        var left = 5 - (len % 5);

        if (left < 5) {
            for (var i = 0; i < left; ++i) {
                bits[len + i] = pad;
            }
        }

        return bits;
    })(out);

    // 3
    out = (function(bits) {
        var len = bits.length,
            parts = [];

        for (var i = 0; i < len; ++i) {
            var j = Math.floor((i / 5));

            parts[j] = parts[j] && parts[j].toString() || '';
            parts[j] += bits[i];
        }

        return parts;
    })(out.join(''));

    // 4
    out = (function(bits, alphabet) {
        var alphabet = alphabet && alphabet.toString() || 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567',
            len = bits.length;

        for (var i = 0; i < len; ++i) {
            var j = parseInt(bits[i], 2);

            bits[i] = alphabet[j];
        }

        return bits;
    })(out, opts.alphabet);

    // 5
    var override = 0;
    switch (left) {
        case 1:
            override = 6;
            break;
        case 2:
            override = 4
            break;
        case 3:
            override = 3;
            break;
        case 4:
            override = 1;
            break;
    }

    for (var i = 0; i < override; ++i) {
        out.pop();
    }

    // 6
    if (opts.padding) {
        for (i = 0; i < override; ++i) {
            out.push(opts.pad);
        }
    }

    return out.join('');
}