timer.hpp

#pragma once

#include <memory>
#include <chrono>
#include <functional>
#include <systemd/sd-event.h>

namespace phosphor
{
namespace state
{
namespace manager
{
namespace timer
{

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

/* Need a custom deleter for freeing up sd_event */
struct EventDeleter
{
    void operator()(sd_event* event) const
    {
        event = sd_event_unref(event);
    }
};
using EventPtr = std::unique_ptr<sd_event, EventDeleter>;

/* Need a custom deleter for freeing up sd_event_source */
struct EventSourceDeleter
{
    void operator()(sd_event_source* eventSource) const
    {
        eventSource = sd_event_source_unref(eventSource);
    }
};
using EventSourcePtr = std::unique_ptr<sd_event_source, EventSourceDeleter>;

/** @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,
 *  reptitive, 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(EventPtr& event, std::function<void()> userCallback,
          std::chrono::microseconds usec, timer::Action action);

    /** @brief Enables / disables the timer
     *  @param[in] action - controls the timer's lifetime
     */
    int state(timer::Action value);

    timer::Action getAction() const;

    std::chrono::microseconds getDuration() const;

  private:
    /** @brief Reference to sd_event unique pointer */
    EventPtr& event_;

    /** @brief Source of events */
    EventSourcePtr eventSource_;

    /** @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;

    /** @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
     *
     *  @return zero on success, non-zero otherwise
     */
    static int timeoutHandler(sd_event_source* eventSource, uint64_t usec,
                              void* userData);
};
} // namespace manager
} // namespace state
} // namespace phosphor