src/sdevent/event.hpp

#pragma once

#include <chrono>
#include <memory>
#include <sdbusplus/bus.hpp>
#include <systemd/sd-event.h>

// TODO: openbmc/openbmc#1720 - add error handling for sd_event API failures

namespace sdevent
{
namespace event
{
namespace timer
{
class Timer;
} // namespace timer
}
namespace event
{

using EventPtr = sd_event*;
class Event;

/** @brief Get an instance of the 'default' event. */
Event newDefault();

namespace details
{

/** @brief unique_ptr functor to release an event reference. */
struct EventDeleter
{
    void operator()(sd_event* ptr) const
    {
        deleter(ptr);
    }

    decltype(&sd_event_unref) deleter = sd_event_unref;
};

/* @brief Alias 'event' to a unique_ptr type for auto-release. */
using Event = std::unique_ptr<sd_event, EventDeleter>;

} // namespace details

/** @class Event
 *  @brief Provides C++ bindings to the sd_event_* class functions.
 */
class Event
{
  public:
    /* Define all of the basic class operations:
     *     Not allowed:
     *         - Default constructor to avoid nullptrs.
     *         - Copy operations due to internal unique_ptr.
     *     Allowed:
     *         - Move operations.
     *         - Destructor.
     */
    Event() = delete;
    Event(const Event&) = delete;
    Event& operator=(const Event&) = delete;
    Event(Event&&) = default;
    Event& operator=(Event&&) = default;
    ~Event() = default;

    /** @brief Conversion constructor from 'EventPtr'.
     *
     *  Increments ref-count of the event-pointer and releases it when
     *  done.
     */
    explicit Event(EventPtr e);

    /** @brief Constructor for 'Event'.
     *
     *  Takes ownership of the event-pointer and releases it when done.
     */
    Event(EventPtr e, std::false_type);

    /** @brief Release ownership of the stored event-pointer. */
    EventPtr release()
    {
        return evt.release();
    }

    /** @brief Wait indefinitely for new event sources. */
    void loop()
    {
        sd_event_loop(evt.get());
    }

    /** @brief Attach to a DBus loop. */
    void attach(sdbusplus::bus::bus& bus)
    {
        bus.attach_event(evt.get(), SD_EVENT_PRIORITY_NORMAL);
    }

    /** @brief C++ wrapper for sd_event_now. */
    auto now()
    {
        using namespace std::chrono;

        uint64_t usec;
        sd_event_now(evt.get(), CLOCK_MONOTONIC, &usec);
        microseconds d(usec);
        return steady_clock::time_point(d);
    }

    friend class timer::Timer;

  private:
    EventPtr get()
    {
        return evt.get();
    }

    details::Event evt;
};

inline Event::Event(EventPtr l) : evt(sd_event_ref(l))
{
}

inline Event::Event(EventPtr l, std::false_type) : evt(l)
{
}

inline Event newDefault()
{
    sd_event* e = nullptr;
    sd_event_default(&e);
    return Event(e, std::false_type());
}

} // namespace event
} // namespace sdevent