@JRubyMethod(required = 1, optional = 1)
  @Override
  public IRubyObject seek(IRubyObject[] args) {
    checkOpen();
    checkFinalized();
    long amount = RubyNumeric.num2long(args[0]);
    int whence = Stream.SEEK_SET;
    long newPosition = data.pos;

    if (args.length > 1 && !args[0].isNil()) whence = RubyNumeric.fix2int(args[1]);

    if (whence == Stream.SEEK_CUR) {
      newPosition += amount;
    } else if (whence == Stream.SEEK_END) {
      newPosition = data.internal.getByteList().length() + amount;
    } else if (whence == Stream.SEEK_SET) {
      newPosition = amount;
    } else {
      throw getRuntime().newErrnoEINVALError("invalid whence");
    }

    if (newPosition < 0) throw getRuntime().newErrnoEINVALError("invalid seek value");

    data.pos = newPosition;
    data.eof = false;

    return RubyFixnum.zero(getRuntime());
  }
 @JRubyMethod(name = {"length", "size"})
 @Override
 public IRubyObject length() {
   checkFinalized();
   return getRuntime().newFixnum(data.internal.getByteList().length());
 }