text: /*
   * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *
   * 1. Redistributions of source code must retain the above copyright notice, this
   *    list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright notice,
   *    this list of conditions and the following disclaimer in the documentation
   *    and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #pragma once
  
  #include <AK/Function.h>
  #include <AK/NonnullOwnPtr.h>
  #include <AK/OwnPtr.h>
  #include <AK/SinglyLinkedList.h>
  #include <Kernel/Time/TimeManagement.h>
  
  namespace Kernel {
  
  typedef u64 TimerId;
  
  struct Timer {
      TimerId id;
      u64 expires;
      Function<void()> callback;
      bool operator<(const Timer& rhs) const
      {
          return expires < rhs.expires;
      }
      bool operator>(const Timer& rhs) const
      {
          return expires > rhs.expires;
      }
      bool operator==(const Timer& rhs) const
      {
          return id == rhs.id;
      }
  };
  
  class TimerQueue {
  public:
      static TimerQueue& the();
  
      TimerId add_timer(NonnullOwnPtr<Timer>&&);
      TimerId add_timer(timeval& timeout, Function<void()>&& callback);
      bool cancel_timer(TimerId id);
      void fire();
  
  private:
      TimerQueue();
  
      void update_next_timer_due();
  
      u64 microseconds_to_ticks(u64 micro_seconds) { return micro_seconds * (m_ticks_per_second / 1'000'000); }
      u64 seconds_to_ticks(u64 seconds) { return seconds * m_ticks_per_second; }
  
      u64 m_next_timer_due { 0 };
      u64 m_timer_id_count { 0 };
      u64 m_ticks_per_second { 0 };
      SinglyLinkedList<NonnullOwnPtr<Timer>> m_timer_queue;
  };
  
  }
  