SetLan: Define the global network timer

As timer is being referred in the provider library
so it should be defined in per process(host-ipmid, net-ipmid)
context.

Defining the timer requires to pull the code of timer in this
repository so adding the timer class.

Change-Id: I4ea5f51fed03dd87d70868b0bc76ff1fb683931c
Signed-off-by: Ratan Gupta <ratagupt@in.ibm.com>
diff --git a/timer.cpp b/timer.cpp
new file mode 100644
index 0000000..06965de
--- /dev/null
+++ b/timer.cpp
@@ -0,0 +1,110 @@
+#include <chrono>
+#include <phosphor-logging/log.hpp>
+#include "timer.hpp"
+namespace phosphor
+{
+namespace ipmi
+{
+
+using namespace phosphor::logging;
+
+// Initializes the timer object
+void Timer::initialize()
+{
+    // This can not be called more than once.
+    if (eventSource)
+    {
+        throw std::runtime_error("Timer already initialized");
+    }
+
+    // Add infinite expiration time
+    auto r = sd_event_add_time(timeEvent, &eventSource,
+                               CLOCK_MONOTONIC, // Time base
+                               UINT64_MAX,      // Expire time - way long time
+                               0,               // Use default event accuracy
+                               timeoutHandler,  // Callback handler on timeout
+                               this);           // User data
+    if (r < 0)
+    {
+        log<level::ERR>("Failure to set initial expiration time value",
+                entry("ERROR=%s", strerror(-r)));
+
+        throw std::runtime_error("Timer initialization failed");
+    }
+
+    // Disable the timer for now
+    r = setTimer(SD_EVENT_OFF);
+    if (r < 0)
+    {
+        log<level::ERR>("Failure to disable timer",
+                entry("ERROR=%s", strerror(-r)));
+
+        throw std::runtime_error("Disabling the timer failed");
+    }
+    return;
+}
+
+/** @brief callback handler on timeout */
+int Timer::timeoutHandler(sd_event_source* eventSource,
+                          uint64_t usec, void* userData)
+{
+    auto timer = static_cast<Timer*>(userData);
+    timer->expired = true;
+
+    log<level::INFO>("Timer expired");
+    // Call optional user call back function if available
+    if(timer->userCallBack)
+    {
+        timer->userCallBack();
+    }
+
+    sd_event_source_set_enabled(eventSource, SD_EVENT_OFF);
+    return 0;
+}
+
+// Gets the time from steady_clock
+std::chrono::microseconds Timer::getTime()
+{
+    using namespace std::chrono;
+    auto usec = steady_clock::now().time_since_epoch();
+    return duration_cast<microseconds>(usec);
+}
+
+// Enables or disables the timer
+int Timer::setTimer(int action)
+{
+    return sd_event_source_set_enabled(eventSource, action);
+}
+
+// Sets the time and arms the timer
+int Timer::startTimer(std::chrono::microseconds timeValue)
+{
+    // Disable the timer
+    setTimer(SD_EVENT_OFF);
+    expired = false;
+
+    // Get the current MONOTONIC time and add the delta
+    auto expireTime = getTime() + timeValue;
+
+    // Set the time
+    auto r = sd_event_source_set_time(eventSource, expireTime.count());
+    if (r < 0)
+    {
+        log<level::ERR>("Failure to set timer",
+                entry("ERROR=%s", strerror(-r)));
+        return r;
+    }
+
+    // A ONESHOT timer means that when the timer goes off,
+    // its moves to disabled state.
+    r = setTimer(SD_EVENT_ONESHOT);
+    if (r < 0)
+    {
+        log<level::ERR>("Failure to start timer",
+                entry("ERROR=%s", strerror(-r)));
+    }
+    return r;
+}
+
+} // namespace ipmi
+} // namespace phosphor