Add the ability for objects which derive from RefCountedThreadSafe to specify...

base/ref_counted.h

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_REF_COUNTED_H_
 #define BASE_REF_COUNTED_H_
 
 #include "base/atomic_ref_count.h"
 #include "base/thread_collision_warner.h"
 
@@ skipping 75 matching lines @@
   void Release() {
     if (subtle::RefCountedBase::Release()) {
       delete static_cast<T*>(this);
     }
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(RefCounted<T>);
 };
 
+// Forward declaration.
+template <class T, typename Traits> class RefCountedThreadSafe;
+
+// Default traits for RefCountedThreadSafe<T>.  Deletes the object when its ref
+// count reaches 0.  Overload to delete it on a different thread etc.
+template<typename T>
+struct DefaultRefCountedThreadSafeTraits {
+  static void Destruct(T* x) {
+    // Delete through RefCountedThreadSafe to make child classes only need to be
+    // friend with RefCountedThreadSafe instead of this struct, which is an
+    // implementation detail.
+    RefCountedThreadSafe<T, DefaultRefCountedThreadSafeTraits>::DeleteInternal(x);
+  }
+};
+
 //
 // A thread-safe variant of RefCounted<T>
 //
 //   class MyFoo : public base::RefCountedThreadSafe<MyFoo> {
 //    ...
 //   };
 //
-template <class T>
+// If you're using the default trait, then you may choose to add compile time
+// asserts that no one else is deleting your object.  i.e.
+//    private:
+//     friend struct base::RefCountedThreadSafe<MyFoo>;
+//     ~MyFoo();
+template <class T, typename Traits = DefaultRefCountedThreadSafeTraits<T> >
 class RefCountedThreadSafe : public subtle::RefCountedThreadSafeBase {
  public:
   RefCountedThreadSafe() { }
   ~RefCountedThreadSafe() { }
 
   void AddRef() {
     subtle::RefCountedThreadSafeBase::AddRef();
   }
 
   void Release() {
     if (subtle::RefCountedThreadSafeBase::Release()) {
-      delete static_cast<T*>(this);
+      Traits::Destruct(static_cast<T*>(this));
     }
   }
 
  private:
-  DISALLOW_COPY_AND_ASSIGN(RefCountedThreadSafe<T>);
+  friend struct DefaultRefCountedThreadSafeTraits<T>;
+  static void DeleteInternal(T* x) { delete x; }
+
+  DISALLOW_COPY_AND_ASSIGN(RefCountedThreadSafe);
 };
 
 //
 // A wrapper for some piece of data so we can place other things in
 // scoped_refptrs<>.
 //
 template<typename T>
 class RefCountedData : public base::RefCounted< base::RefCountedData<T> > {
  public:
   RefCountedData() : data() {}
@@ skipping 110 matching lines @@
 
   void swap(scoped_refptr<T>& r) {
     swap(&r.ptr_);
   }
 
  protected:
   T* ptr_;
 };
 
 #endif  // BASE_REF_COUNTED_H_