Function base64_decode

index.js:462–501

* Decodes a base64 encoded string to up to len bytes of output. * @param {string} s String to decode * @param {number} len Maximum output length * @returns {!Array. } * @inner

(s, len)

 * @inner
 */
function base64_decode(s, len) {
  var off = 0,
    slen = s.length,
    olen = 0,
    rs = [],
    c1,
    c2,
    c3,
    c4,
    o,
    code;
  if (len <= 0) throw Error("Illegal len: " + len);
  while (off < slen - 1 && olen < len) {
    code = s.charCodeAt(off++);
    c1 = code < BASE64_INDEX.length ? BASE64_INDEX[code] : -1;
    code = s.charCodeAt(off++);
    c2 = code < BASE64_INDEX.length ? BASE64_INDEX[code] : -1;
    if (c1 == -1 || c2 == -1) break;
    o = (c1 << 2) >>> 0;
    o |= (c2 & 0x30) >> 4;
    rs.push(String.fromCharCode(o));
    if (++olen >= len || off >= slen) break;
    code = s.charCodeAt(off++);
    c3 = code < BASE64_INDEX.length ? BASE64_INDEX[code] : -1;
    if (c3 == -1) break;
    o = ((c2 & 0x0f) << 4) >>> 0;
    o |= (c3 & 0x3c) >> 2;
    rs.push(String.fromCharCode(o));
    if (++olen >= len || off >= slen) break;
    code = s.charCodeAt(off++);
    c4 = code < BASE64_INDEX.length ? BASE64_INDEX[code] : -1;
    o = ((c3 & 0x03) << 6) >>> 0;
    o |= c4;
    rs.push(String.fromCharCode(o));
    ++olen;
  }
  var res = [];
  for (off = 0; off < olen; off++) res.push(rs[off].charCodeAt(0));
  return res;
}

/**
 * @type {number}