MT#62181 wheeltimer: refactor arming logic

Move some of the timer arming logic out of the wheeltimer and into the
timer class, so that more members can be made private. No functional
changes.

Change-Id: I4f2a10b0a3d9c775ec6cb903c2b82f4aa3219349

core/sip/wheeltimer.cpp

@@ -112,52 +112,48 @@ void _wheeltimer::process_current_timers(timer_list& list, std::unique_lock<std:
 {
     while (!list.empty()) {
 	auto* t = list.front();
-	list.pop_front();
+
+	t->disarm(); // removes it from list
 
 	// safe to unlock now
 	lock.unlock();
 
-	t->list = NULL;
-	t->disarm();
-
 	t->fire();
 
 	lock.lock();
     }
 }
 
-void _wheeltimer::place_timer(timer* t)
+uint64_t _wheeltimer::get_timer_bucket(timer* t)
 {
-    t->arm();
-
     uint64_t exp = t->get_absolute_expiry();
 
     // scale expiry based on resolution: this is the bucket index
-    exp = ((exp / resolution) + 1) * resolution;
+    uint64_t bucket = ((exp / resolution) + 1) * resolution;
 
     // if expiry is too soon or in the past, put the timer in the next bucket up
     auto now = gettimeofday_us();
-    if (exp <= now)
-	exp = ((now / resolution) + 1) * resolution;
+    if (bucket <= now)
+	bucket = ((now / resolution) + 1) * resolution;
+
+    return bucket;
+}
 
-    add_timer_to_bucket(t, exp);
+void _wheeltimer::place_timer(timer* t)
+{
+    t->arm();
+    uint64_t bucket = get_timer_bucket(t);
+    add_timer_to_bucket(t, bucket);
 }
 
 void _wheeltimer::add_timer_to_bucket(timer* t, uint64_t bucket)
 {
-    auto& b = buckets[bucket];
-    t->list = &b;
-    b.push_front(t);
-    t->pos = b.begin();
+    t->link(buckets[bucket]);
 }
 
 void _wheeltimer::delete_timer(timer* t)
 {
-    if (t->list) {
-	t->list->erase(t->pos);
-	t->list = NULL;
-    }
-
+    t->disarm();
     delete t;
 }
 

core/sip/wheeltimer.h

@@ -48,11 +48,11 @@ typedef std::map<uint64_t, timer_list> timer_buckets;
 
 class timer
 {
-public:
     // for fast removal:
     timer_list::iterator pos;
     timer_list* list;
 
+public:
     timer() 
 	: list(NULL), expires(0), expires_rel(0)
     {}
@@ -69,19 +69,28 @@ public:
 
     virtual void fire()=0;
 
-    // returns true if timer was not armed before
-    // return false and does nothing otherwise
-    bool arm()
+    void arm()
     {
 	if (expires)
-	    return false;
+	    return;
 	expires = expires_rel + gettimeofday_us();
-	return true;
+    }
+
+    void link(timer_list& new_list)
+    {
+	list = &new_list;
+	list->push_front(this);
+	pos = list->begin();
     }
 
     void disarm()
     {
 	expires = 0;
+
+	if (list) {
+	    list->erase(pos);
+	    list = NULL;
+	}
     }
 
     // microseconds
@@ -120,6 +129,7 @@ class _wheeltimer:
     void place_timer(timer* t);
 
     void add_timer_to_bucket(timer* t, uint64_t);
+    uint64_t get_timer_bucket(timer* t);
     void delete_timer(timer* t);
 
     void process_current_timers(timer_list&, std::unique_lock<std::mutex>&);