Added virtual method to control zero reference notification before the

RefObject mutex is unlocked. Also expose said mutex through static method.


git-svn-id: http://yate.null.ro/svn/yate/trunk@1348 acf43c95-373e-0410-b603-e72c3f656dc1

engine/TelEngine.cpp

@@ -545,12 +545,15 @@ bool RefObject::ref()
 
 bool RefObject::deref()
 {
+    bool zeroCall = false;
     s_refmutex.lock();
     int i = m_refcount;
     if (i > 0)
 	--m_refcount;
-    s_refmutex.unlock();
     if (i == 1)
+	zeroCall = zeroRefsTest();
+    s_refmutex.unlock();
+    if (zeroCall)
 	zeroRefs();
     else if (i <= 0)
 	Debug(DebugFail,"RefObject::deref() called with count=%d [%p]",i,this);
@@ -563,6 +566,11 @@ void RefObject::zeroRefs()
     delete this;
 }
 
+bool RefObject::zeroRefsTest()
+{
+    return true;
+}
+
 bool RefObject::resurrect()
 {
     s_refmutex.lock();
@@ -577,6 +585,10 @@ void RefObject::destroyed()
 {
 }
 
+Mutex& RefObject::refMutex()
+{
+    return s_refmutex;
+}
 
 void RefPointerBase::assign(RefObject* oldptr, RefObject* newptr, void* pointer)
 {

yateclass.h

@@ -566,6 +566,7 @@ struct TokenDict {
 };
 
 class String;
+class Mutex;
 
 #if 0 /* for documentation generator */
 /**
@@ -703,13 +704,30 @@ public:
      */
     virtual void destruct();
 
+    /**
+     * Retrieve the mutex that protects ref() and deref() for all objects
+     * @return Reference to the global mutex used for all counter operations
+     */
+    static Mutex& refMutex();
+
 protected:
     /**
-     * This method is called when the reference count reaches zero.
+     * This method is called when the reference count reaches zero after
+     *  unlocking the mutex if the call to zeroRefsTest() returned true.
      * The default behaviour is to delete the object.
      */
     virtual void zeroRefs();
 
+    /**
+     * This method is called when the reference count reaches zero just before
+     *  calling zeroRefs() with the non-recursive mutex still locked.
+     * Extra care must be taken to prevent deadlocks, normally the code should
+     *  only change some variables and return.
+     * The default implementation just returns true.
+     * @return True to call zeroRefs() after releasing the mutex
+     */
+    virtual bool zeroRefsTest();
+
     /**
      * Bring the object back alive by setting the reference counter to one.
      * Note that it works only if the counter was zero previously