decodeString static method

Implementation

static decodeString(String str) {
  var i = 0;
  var endLen = str.length - 1;
  // look up type
  var p = <String, dynamic>{'type': num.parse(str[0])};

  if (null == PacketTypes[p['type']]) {
    throw new UnsupportedError("unknown packet type " + p['type']);
  }

  // look up attachments if type binary
  if (BINARY_EVENT == p['type'] || BINARY_ACK == p['type']) {
    final start = i + 1;
    while (str[++i] != '-' && i != str.length) {}
    var buf = str.substring(start, i);
    if (buf != '${num.tryParse(buf) ?? -1}' || str[i] != '-') {
      throw new ArgumentError('Illegal attachments');
    }
    p['attachments'] = num.parse(buf);
  }

  // look up namespace (if any)
  if (i < endLen - 1 && '/' == str[i + 1]) {
    var start = i + 1;
    while (++i > 0) {
      if (i == str.length) break;
      var c = str[i];
      if ("," == c) break;
    }
    p['nsp'] = str.substring(start, i);
  } else {
    p['nsp'] = '/';
  }

  // look up id
  var next = i < endLen - 1 ? str[i + 1] : null;
  if (next?.isNotEmpty == true && '${num.tryParse(next!)}' == next) {
    var start = i + 1;
    while (++i > 0) {
      var c = str.length > i ? str[i] : null;
      if ('${num.tryParse(c!)}' != c) {
        --i;
        break;
      }
      if (i == str.length) break;
    }
    p['id'] = int.tryParse(str.substring(start, i + 1));
  }

  // look up json data
  if (i < endLen - 1 && str[++i].isNotEmpty == true) {
    var payload = tryParse(str.substring(i));
    if (isPayloadValid(p['type'], payload)) {
      p['data'] = payload;
    } else {
      throw new UnsupportedError("invalid payload");
    }
  }

//    debug('decoded %s as %j', str, p);
  return p;
}