GC: Refine wrapper constructor.

trunk/src/app/srs_app_conn.hpp

@@ -139,22 +139,69 @@ extern ISrsLazyGc* _srs_gc;
 
 // A wrapper template for lazy-sweep resource.
 // See https://github.com/ossrs/srs/issues/3176#lazy-sweep
+//
+// Usage for resource which manages itself in coroutine cycle, see SrsLazyGbSession:
+//      class Resource {
+//      private:
+//          SrsLazyObjectWrapper<Resource>* wrapper_;
+//      private:
+//          friend class SrsLazyObjectWrapper<Resource>;
+//          Resource(SrsLazyObjectWrapper<Resource>* wrapper) { wrapper_ = wrapper; }
+//      public:
+//          srs_error_t Resource::cycle() {
+//              srs_error_t err = do_cycle();
+//              _srs_gb_manager->remove(wrapper_);
+//              return err;
+//          }
+//      };
+//      SrsLazyObjectWrapper<Resource>* obj = new SrsLazyObjectWrapper<Resource>*();
+//      _srs_gb_manager->add(obj); // Add wrapper to resource manager.
+//      Start a coroutine to do obj->resource()->cycle().
+//
+// Usage for resource managed by other object:
+//      class Resource {
+//      private:
+//          friend class SrsLazyObjectWrapper<Resource>;
+//          Resource(SrsLazyObjectWrapper<Resource>* /*wrapper*/) {
+//          }
+//      };
+//      class Manager {
+//      private:
+//          SrsLazyObjectWrapper<Resource>* wrapper_;
+//      public:
+//          Manager() { wrapper_ = new SrsLazyObjectWrapper<Resource>(); }
+//          ~Manager() { srs_freep(wrapper_); }
+//      };
+//      Manager* manager = new Manager();
+//      srs_freep(manager);
+//
+// Note that under-layer resource are destroyed by _srs_gc, which is literally equal to srs_freep. However, the root
+// wrapper might be managed by other resource manager, such as _srs_gb_manager for SrsLazyGbSession. Furthermore, other
+// copied out wrappers might be freed by srs_freep. All are ok, because all wrapper and resources are simply normal
+// object, so if you added to manager then you should use manager to remove it, and you can also directly delete it.
 template<typename T>
 class SrsLazyObjectWrapper : public ISrsResource
 {
 private:
     T* resource_;
 public:
-    SrsLazyObjectWrapper(T* resource = NULL) {
-        resource_ = resource ? resource : new T(this);
-        resource_->gc_use();
+    SrsLazyObjectWrapper() {
+        init(new T(this));
     }
     virtual ~SrsLazyObjectWrapper() {
         resource_->gc_dispose();
         if (resource_->gc_ref() == 0) {
             _srs_gc->remove(resource_);
         }
     }
+private:
+    SrsLazyObjectWrapper(T* resource) {
+        init(resource);
+    }
+    void init(T* resource) {
+        resource_ = resource;
+        resource_->gc_use();
+    }
 public:
     SrsLazyObjectWrapper<T>* copy() {
         return new SrsLazyObjectWrapper<T>(resource_);