  function amountFilled(address tokenGet, uint amountGet, address tokenGive, uint amountGive, uint expires, uint nonce, address user) public view returns(uint) {
    bytes32 hash = keccak256(abi.encodePacked(this, tokenGet, amountGet, tokenGive, amountGive, expires, nonce));
    return orderFills[user][hash];
  }