timer.hpp

#pragma once

#include <systemd/sd-event.h>

#include <chrono>
#include <functional>

namespace phosphor
{
namespace hwmon
{
namespace timer
{

enum Action
{
    OFF = SD_EVENT_OFF,
    ON = SD_EVENT_ON,
    ONESHOT = SD_EVENT_ONESHOT
};
}

/** @class Timer
 *  @brief Provides a timer source and a mechanism to callback when the timer
 *         expires.
 *
 *  The timer is armed upon construction. The constructor requires a timeout
 *  handler function, the timer expiry duration, and the timer state (one-shot,
 *  repetitive, disabled).
 *  It's possible to change the state of the timer after it's been armed via the
 *  state() API.
 */
class Timer
{
  public:
    Timer() = delete;
    Timer(const Timer&) = delete;
    Timer& operator=(const Timer&) = delete;
    Timer(Timer&&) = delete;
    Timer& operator=(Timer&&) = delete;

    /** @brief Constructs timer object
     *
     *  @param[in] events - sd_event pointer
     *  @param[in] callback - function callback for timer expiry
     *  @param[in] usec - timer duration, in micro seconds
     *  @param[in] action - controls the timer's lifetime
     */
    Timer(sd_event* event, std::function<void()> userCallback,
          std::chrono::microseconds usec, timer::Action action);

    ~Timer()
    {
        if (eventSource)
        {
            eventSource = sd_event_source_unref(eventSource);
        }
    }

    /** @brief Timer expiry handler - invokes callback
     *
     *  @param[in] eventSource - Source of the event
     *  @param[in] usec        - time in micro seconds
     *  @param[in] userData    - User data pointer
     *
     */
    static int timeoutHandler(sd_event_source* eventSource, uint64_t usec,
                              void* userData);

    /** @brief Enables / disables the timer
     *  @param[in] action - controls the timer's lifetime
     */
    int state(timer::Action action)
    {
        return sd_event_source_set_enabled(eventSource, action);
    }

    timer::Action getAction() const
    {
        return action;
    }

    std::chrono::microseconds getDuration() const
    {
        return duration;
    }

  private:
    /** @brief the sd_event structure */
    sd_event* event = nullptr;

    /** @brief Source of events */
    sd_event_source* eventSource = nullptr;

    /** @brief Optional function to call on timer expiration */
    std::function<void()> callback{};

    /** @brief Duration of the timer */
    std::chrono::microseconds duration{};

    /** @brief whether the timer is enabled/disabled/one-shot */
    timer::Action action = timer::OFF;
};

} // namespace hwmon
} // namespace phosphor