utility/timer: Implement callback setting

All of the other classes that take callbacks support having the callback
updated.

Tested:
    Builds and passed through the unit test suite.

Change-Id: I0efcd074523fa6ec0cc84c7a930346dd9340f7ec
Signed-off-by: William A. Kennington III <wak@google.com>

3 files changed, 19 insertions, 0 deletions

diff --git a/src/sdeventplus/utility/timer.cpp b/src/sdeventplus/utility/timer.cpp
index 2f28257..242f5d6 100644
--- a/src/sdeventplus/utility/timer.cpp
+++ b/src/sdeventplus/utility/timer.cpp
@@ -55,6 +55,12 @@ Timer<Id>::Timer(const Event& event, Callback&& callback,
 }
 
 template <ClockId Id>
+void Timer<Id>::set_callback(Callback&& callback)
+{
+    this->callback = std::move(callback);
+}
+
+template <ClockId Id>
 const Event& Timer<Id>::get_event() const
 {
     return timeSource.get_event();
diff --git a/src/sdeventplus/utility/timer.hpp b/src/sdeventplus/utility/timer.hpp
index e45cf46..5d36458 100644
--- a/src/sdeventplus/utility/timer.hpp
+++ b/src/sdeventplus/utility/timer.hpp
@@ -61,6 +61,12 @@ class Timer
           typename source::Time<Id>::Accuracy accuracy =
               std::chrono::milliseconds{1});
 
+    /** @brief Sets the callback
+     *
+     *  @param[in] callback - The function executed on timer elapse
+     */
+    void set_callback(Callback&& callback);
+
     /** @brief Gets the associated Event object
      *
      *  @return The Event
diff --git a/test/utility/timer.cpp b/test/utility/timer.cpp
index 6c04e87..f35a0c4 100644
--- a/test/utility/timer.cpp
+++ b/test/utility/timer.cpp
@@ -379,6 +379,13 @@ TEST_F(TimerTest, CallbackMove)
     expectSetTime(new_time + interval);
     EXPECT_EQ(0, handler(nullptr, 0, handler_userdata));
     EXPECT_EQ(1, called);
+
+    // update the callback and make sure it still works
+    timer->set_callback(std::bind([]() {}));
+    expectNow(new_time);
+    expectSetTime(new_time + interval);
+    EXPECT_EQ(0, handler(nullptr, 0, handler_userdata));
+    EXPECT_EQ(1, called);
 }
 
 TEST_F(TimerTest, SetValuesExpiredTimer)