Add Timer class

The class provides for a timer, callback invocation on timer expiry, and
timer control/cleanup. This will be used in subsequent commits.

Change-Id: Ic8f43264a47903732b590a360ef0d8af765d5a20
Signed-off-by: Nagaraju Goruganti <ngorugan@in.ibm.com>

1 files changed, 112 insertions, 0 deletions

diff --git a/timer.hpp b/timer.hpp
new file mode 100644
index 0000000..f5f9ada
--- /dev/null
+++ b/timer.hpp
@@ -0,0 +1,112 @@
+#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