// vi:set ft=cpp: -*- Mode: C++ -*-
/*
 * (c) 2012 Adam Lackorzynski <adam@os.inf.tu-dresden.de>,
 *     economic rights: Technische Universität Dresden (Germany)
 * This file is part of TUD:OS and distributed under the terms of the
 * GNU Lesser General Public License 2.1.
 * Please see the COPYING-LGPL-2.1 file for details.
 */
#pragma once

#include <cassert>
#include <l4/sys/kip.h>
#include <l4/re/env.h>

namespace L4 {

/**
 * \brief A polling timeout based on the L4Re clock.
 *
 * This class allows to conveniently add a timeout to a polling loop.
 *
 * The original
 * ~~~{.cpp}
 * while (device.read(State) & Busy)
 *   ;
 * ~~~
 *
 * is converted to
 *
 * ~~~{.cpp}
 * Poll_timeout_kipclock timeout(10000);
 * while (timeout.test(device.read(State) & Busy))
 *   ;
 * if (timeout.timed_out())
 *   printf("ERROR: Device does not respond.\n");
 * ~~~
 */
class Poll_timeout_kipclock
{
public:
  /**
   * \brief Initialise relative timeout in microseconds
   * \param poll_time_us  Polling timeout in microseconds.
   */
  Poll_timeout_kipclock(unsigned poll_time_us)
  {
    set(poll_time_us);
  }

  /**
   * \brief (Re-)Set relative timeout in microseconds
   * \param poll_time_us  Polling timeout in microseconds.
   */
  void set(unsigned poll_time_us)
  {
    _timeout = l4_kip_clock(l4re_kip()) + poll_time_us;
    _last_check = true;
  }

  /** \brief Test whether timeout has expired
   * \param expression Optional expression.
   *
   * \retval false  The timeout has expired or the given expression returned
   *                false.
   * \retval true   The timeout has not expired and the optionally given
   *                expression returns true.
   */
  bool test(bool expression = true)
  {
    if (!expression)
      return false;

    return _last_check = l4_kip_clock(l4re_kip()) < _timeout;
  }

  /**
   * \brief Query whether timeout has expired
   * \return Expiry state of timeout
   */
  bool timed_out() const { return !_last_check; }

private:
  l4_cpu_time_t _timeout;
  bool _last_check;
};
}