function push(address depositor, uint deposit, uint expect) private {
        
        Deposit memory dep = Deposit(depositor, uint128(deposit), uint128(expect));
        assert(currentQueueSize <= queue.length); 
        if(queue.length == currentQueueSize)
            queue.push(dep);
        else
            queue[currentQueueSize] = dep;

        currentQueueSize++;
    }