source: prototipo_portal_2018/prototipo/static/js/hwcrypto/hex2base.js @ 327fd70

// FIXME: origin unknown
if (!window.atob) {
  var tableStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  var table = tableStr.split("");

  window.atob = function (base64) {
    if (/(=[^=]+|={3,})$/.test(base64)) throw new Error("String contains an invalid character");
    base64 = base64.replace(/=/g, "");
    var n = base64.length & 3;
    if (n === 1) throw new Error("String contains an invalid character");
    for (var i = 0, j = 0, len = base64.length / 4, bin = []; i < len; ++i) {
      var a = tableStr.indexOf(base64[j++] || "A"), b = tableStr.indexOf(base64[j++] || "A");
      var c = tableStr.indexOf(base64[j++] || "A"), d = tableStr.indexOf(base64[j++] || "A");
      if ((a | b | c | d) < 0) throw new Error("String contains an invalid character");
      bin[bin.length] = ((a << 2) | (b >> 4)) & 255;
      bin[bin.length] = ((b << 4) | (c >> 2)) & 255;
      bin[bin.length] = ((c << 6) | d) & 255;
    };
    return String.fromCharCode.apply(null, bin).substr(0, bin.length + n - 4);
  };

  window.btoa = function (bin) {
    for (var i = 0, j = 0, len = bin.length / 3, base64 = []; i < len; ++i) {
      var a = bin.charCodeAt(j++), b = bin.charCodeAt(j++), c = bin.charCodeAt(j++);
      if ((a | b | c) > 255) throw new Error("String contains an invalid character");
      base64[base64.length] = table[a >> 2] + table[((a << 4) & 63) | (b >> 4)] +
                              (isNaN(b) ? "=" : table[((b << 2) & 63) | (c >> 6)]) +
                              (isNaN(b + c) ? "=" : table[c & 63]);
    }
    return base64.join("");
  };

}

function hexToBase64(str) {
  return btoa(String.fromCharCode.apply(null,
    str.replace(/\r|\n/g, "").replace(/([\da-fA-F]{2}) ?/g, "0x$1 ").replace(/ +$/, "").split(" "))
  );
}

function hexToPem(s) {
   var b = hexToBase64(s);
   var pem = b.match(/.{1,64}/g).join("\n");
   return "-----BEGIN CERTIFICATE-----\n" + pem + "\n-----END CERTIFICATE-----"; 
}