Changed EventQueue::cancel to return boolean value

It's important in some cases to know wether the cancel
succeeded. Now Cancel method return boolean value to indicate
did the cancel succeed.

Author: Teppo Järvelin

TESTS/events/queue/main.cpp

@@ -166,9 +166,11 @@ void cancel_test1()
     }
 
     for (int i = N - 1; i >= 0; i--) {
-        queue.cancel(ids[i]);
+        TEST_ASSERT_TRUE(queue.cancel(ids[i]));
     }
 
+    TEST_ASSERT_FALSE(queue.cancel(-9999));
+
     queue.dispatch(0);
 }
 

UNITTESTS/stubs/EventQueue_stub.cpp

@@ -47,7 +47,7 @@ unsigned EventQueue::tick()
     return EventQueue_stub::unsigned_value;
 }
 
-void EventQueue::cancel(int id)
+bool EventQueue::cancel(int id)
 {
 }
 

UNITTESTS/stubs/equeue_stub.c

@@ -92,9 +92,9 @@ int equeue_post(equeue_t *queue, void (*cb)(void *), void *event)
     return 0;
 }
 
-void equeue_cancel(equeue_t *queue, int id)
+bool equeue_cancel(equeue_t *queue, int id)
 {
-
+    return true;
 }
 
 void equeue_background(equeue_t *queue,

events/EventQueue.cpp

@@ -50,7 +50,7 @@ unsigned EventQueue::tick()
     return equeue_tick();
 }
 
-void EventQueue::cancel(int id)
+bool EventQueue::cancel(int id)
 {
     return equeue_cancel(&_equeue, id);
 }

events/EventQueue.h

@@ -127,8 +127,10 @@ class EventQueue : private mbed::NonCopyable<EventQueue> {
      *  returns, as the event may have already begun executing.
      *
      *  @param id       Unique id of the event
+     *  @return         true  if event was successfully cancelled
+     *                  false if event was not cancelled (invalid id or executing already begun)
      */
-    void cancel(int id);
+    bool cancel(int id);
 
     /** Query how much time is left for delayed event
      *

events/equeue/equeue.c

@@ -373,15 +373,18 @@ int equeue_post(equeue_t *q, void (*cb)(void *), void *p)
     return id;
 }
 
-void equeue_cancel(equeue_t *q, int id)
+bool equeue_cancel(equeue_t *q, int id)
 {
     if (!id) {
-        return;
+        return false;
     }
 
     struct equeue_event *e = equeue_unqueue(q, id);
     if (e) {
         equeue_dealloc(q, e + 1);
+        return true;
+    } else {
+        return false;
     }
 }
 
@@ -602,7 +605,7 @@ static void equeue_chain_dispatch(void *p)
 static void equeue_chain_update(void *p, int ms)
 {
     struct equeue_chain_context *c = (struct equeue_chain_context *)p;
-    equeue_cancel(c->target, c->id);
+    (void)equeue_cancel(c->target, c->id);
 
     if (ms >= 0) {
         c->id = equeue_call_in(c->target, ms, equeue_chain_dispatch, c->q);

events/equeue/equeue.h

@@ -183,9 +183,9 @@ int equeue_post(equeue_t *queue, void (*cb)(void *), void *event);
 // The equeue_cancel function is irq safe.
 //
 // If called while the event queue's dispatch loop is active, equeue_cancel
-// does not guarantee that the event will not not execute after it returns as
+// does not guarantee that the event will not execute after it returns as
 // the event may have already begun executing.
-void equeue_cancel(equeue_t *queue, int id);
+bool equeue_cancel(equeue_t *queue, int id);
 
 // Query how much time is left for delayed event
 //