normalize-der.js

exports.normalize = function normalize(signature) {
  var data, p, len, rlen, slen;

  if (Buffer.isBuffer(signature))
    signature = Array.prototype.slice.call(signature);
  else if (typeof signature === 'string')
    signature = utils.toArray(signature, 'hex');

  data = signature.slice();
  p = { place: 0 };

  if (data[p.place++] !== 0x30)
    return signature;

  len = getLength(data, p);

  if (data.length > len + p.place)
    data = data.slice(0, len + p.place);

  if (data[p.place++] !== 0x02)
    return signature;

  rlen = getLength(data, p);
  p.place += rlen;

  if (data[p.place++] !== 0x02)
    return signature;

  slen = getLength(data, p);
  if (data.length > slen + p.place)
    data = data.slice(0, slen + p.place);

  return data;
};

function getLength(buf, p) {
  var initial = buf[p.place++];
  if (!(initial & 0x80)) {
    return initial;
  }
  var octetLen = initial & 0xf;
  var val = 0;
  for (var i = 0, off = p.place; i < octetLen; i++, off++) {
    val <<= 8;
    val |= buf[off];
  }
  p.place = off;
  return val;
}