@lapo/asn1js/base64.js

Generic ASN.1 parser/decoder that can decode any valid ASN.1 DER or BER structures.

// Base64 JavaScript decoder
// Copyright (c) 2008 Lapo Luchini <lapo@lapo.it>

// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

const
    haveU8 = (typeof Uint8Array == 'function');

let decoder; // populated on first usage

export class Base64 {

    static decode(a) {
        let isString = (typeof a == 'string');
        let i;
        if (decoder === undefined) {
            let b64 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/',
                ignore = '= \f\n\r\t\u00A0\u2028\u2029';
            decoder = [];
            for (i = 0; i < 64; ++i)
                decoder[b64.charCodeAt(i)] = i;
            for (i = 0; i < ignore.length; ++i)
                decoder[ignore.charCodeAt(i)] = -1;
            // also support decoding Base64url (RFC 4648 section 5)
            decoder['-'.charCodeAt(0)] = decoder['+'.charCodeAt(0)];
            decoder['_'.charCodeAt(0)] = decoder['/'.charCodeAt(0)];
        }
        let out = haveU8 ? new Uint8Array(a.length * 3 >> 2) : [];
        let bits = 0, char_count = 0, len = 0;
        for (i = 0; i < a.length; ++i) {
            let c = isString ? a.charCodeAt(i) : a[i];
            if (c == 61) // '='.charCodeAt(0)
                break;
            c = decoder[c];
            if (c == -1)
                continue;
            if (c === undefined)
                throw 'Illegal character at offset ' + i;
            bits |= c;
            if (++char_count >= 4) {
                out[len++] = (bits >> 16);
                out[len++] = (bits >> 8) & 0xFF;
                out[len++] = bits & 0xFF;
                bits = 0;
                char_count = 0;
            } else {
                bits <<= 6;
            }
        }
        switch (char_count) {
        case 1:
            throw 'Base64 encoding incomplete: at least 2 bits missing';
        case 2:
            out[len++] = (bits >> 10);
            break;
        case 3:
            out[len++] = (bits >> 16);
            out[len++] = (bits >> 8) & 0xFF;
            break;
        }
        if (haveU8 && out.length > len) // in case it was originally longer because of ignored characters
            out = out.subarray(0, len);
        return out;
    }

    static pretty(str) {
        // fix padding
        let pad = 4 - str.length % 4;
        if (pad < 4)
            str += '==='.slice(0, pad);
        // convert Base64url (RFC 4648 section 5) to standard Base64 (RFC 4648 section 4)
        str = str.replace(/-/g, '+').replace(/_/g, '/');
        // 80 column width
        return str.replace(/.{80}/g, '$&\n');
    }

    static unarmor(a) {
        let m = Base64.re.exec(a);
        if (m) {
            if (m[1])
                a = m[1];
            else if (m[2])
                a = m[2];
            else if (m[3])
                a = m[3];
            else
                throw 'RegExp out of sync';
        }
        return Base64.decode(a);
    }

}

Base64.re = /-----BEGIN [^-]+-----([A-Za-z0-9+/=\s]+)-----END [^-]+-----|begin-base64[^\n]+\n([A-Za-z0-9+/=\s]+)====|^([A-Za-z0-9+/=\s]+)$/;