MT#62181 wheeltimer: use std::list

... instead of manually maintaining a linked list.

Store an iterator in the timer object so that it can be directly removed
if needed.

Change-Id: I38f1fbcdc6fe1b36a8adef6a95f36f8902a4f729

core/sip/wheeltimer.cpp

@@ -123,15 +123,12 @@ void _wheeltimer::update_wheel(int wheel)
 	int pos = (wall_clock >> (wheel*BITS_PER_WHEEL))
 	    & ((1<<BITS_PER_WHEEL)-1);
 	
-	timer *t = (timer*)wheels[wheel][pos].next;
-	while( t ) {
-	    
-	    timer* t1 = (timer*)t->next;
-	    place_timer(t,wheel-1);
-	    t = t1;
+	auto& w = wheels[wheel][pos];
+	while (!w.empty()) {
+	    auto* t = w.front();
+	    w.pop_front();
+	    place_timer(t, wheel-1);
 	}
-
-	wheels[wheel][pos].next = NULL;
     }
 }
 
@@ -183,23 +180,18 @@ void _wheeltimer::process_events()
 
 void _wheeltimer::process_current_timers()
 {
-    timer *t = (timer *)wheels[0][wall_clock & 0xFF].next;
-    
-    while(t){
+    auto& w = wheels[0][wall_clock & 0xFF];
 
-	timer* t1 = (timer*)t->next;
+    while (!w.empty()) {
+	auto* t = w.front();
+	w.pop_front();
 
-	t->next = NULL;
-	t->prev = NULL;
+	t->list = NULL;
 	t->disarm();
 	num_timers--;
 
 	t->fire();
-
-	t = t1;
     }
-    
-    wheels[0][wall_clock & 0xFF].next = NULL;
 }
 
 void _wheeltimer::place_timer(timer* t)
@@ -240,26 +232,18 @@ void _wheeltimer::place_timer(timer* t, int wheel)
 
 void _wheeltimer::add_timer_to_wheel(timer* t, int wheel, unsigned int pos)
 {
-    t->next = wheels[wheel][pos].next;
-    wheels[wheel][pos].next = t;
-
-    if(t->next){
-	((timer*)t->next)->prev = t;
-    }
-
-    t->prev = &(wheels[wheel][pos]);
+    t->list = &wheels[wheel][pos];
+    t->list->push_front(t);
+    t->pos = wheels[wheel][pos].begin();
 }
 
 void _wheeltimer::delete_timer(timer* t)
 {
-    if(t->prev) {
-	t->prev->next = t->next;
-	num_timers--;
+    if (t->list) {
+	t->list->erase(t->pos);
+	t->list = NULL;
     }
 
-    if(t->next)
-	((timer*)t->next)->prev = t->prev;
-
     delete t;
 }
 

core/sip/wheeltimer.h

@@ -36,6 +36,7 @@
 #include <inttypes.h>
 #include <time.h>
 #include <deque>
+#include <list>
 
 #include "atomic_types.h"
 
@@ -45,33 +46,27 @@
 // do not change
 #define WHEELS 4
 
-class base_timer
-{
-public:
-    base_timer* next;
+class timer;
 
-    base_timer():next(0) {}
-    virtual ~base_timer() {}
-};
+typedef std::list<timer*> timer_list;
 
-class timer: public base_timer
+class timer
 {
 public:
-    base_timer*  prev;
+    // for fast removal:
+    timer_list::iterator pos;
+    timer_list* list;
 
     timer() 
-	: base_timer(),
-	  prev(0), expires(0), expires_rel(0)
+	: list(NULL), expires(0), expires_rel(0)
     {}
 
     timer(uint64_t expires)
-        : base_timer(),
-	  prev(0), expires(0), expires_rel(expires)
+        : list(NULL), expires(0), expires_rel(expires)
     {}
 
     timer(const timer &t)
-        : base_timer(),
-	  prev(0), expires(t.expires), expires_rel(t.expires_rel)
+        : list(NULL), expires(t.expires), expires_rel(t.expires_rel)
     {}
 
     virtual ~timer();
@@ -122,7 +117,7 @@ class _wheeltimer:
     };
 
     //the timer wheel
-    base_timer wheels[WHEELS][ELMTS_PER_WHEEL];
+    timer_list wheels[WHEELS][ELMTS_PER_WHEEL];
     unsigned int num_timers;
     uint64_t resolution; // microseconds