michael@0: // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
michael@0: // Use of this source code is governed by a BSD-style license that can be
michael@0: // found in the LICENSE file.
michael@0: 
michael@0: #ifndef BASE_REF_COUNTED_H_
michael@0: #define BASE_REF_COUNTED_H_
michael@0: 
michael@0: #include "base/atomic_ref_count.h"
michael@0: #include "base/thread_collision_warner.h"
michael@0: 
michael@0: namespace base {
michael@0: 
michael@0: namespace subtle {
michael@0: 
michael@0: class RefCountedBase {
michael@0:  protected:
michael@0:   RefCountedBase();
michael@0:   ~RefCountedBase();
michael@0: 
michael@0:   void AddRef();
michael@0: 
michael@0:   // Returns true if the object should self-delete.
michael@0:   bool Release();
michael@0: 
michael@0:  private:
michael@0:   int ref_count_;
michael@0: #ifndef NDEBUG
michael@0:   bool in_dtor_;
michael@0: #endif
michael@0: 
michael@0:   DFAKE_MUTEX(add_release_)
michael@0: 
michael@0:   DISALLOW_COPY_AND_ASSIGN(RefCountedBase);
michael@0: };
michael@0: 
michael@0: class RefCountedThreadSafeBase {
michael@0:  protected:
michael@0:   RefCountedThreadSafeBase();
michael@0:   ~RefCountedThreadSafeBase();
michael@0: 
michael@0:   void AddRef();
michael@0: 
michael@0:   // Returns true if the object should self-delete.
michael@0:   bool Release();
michael@0: 
michael@0:  private:
michael@0:   AtomicRefCount ref_count_;
michael@0: #ifndef NDEBUG
michael@0:   bool in_dtor_;
michael@0: #endif
michael@0: 
michael@0:   DISALLOW_COPY_AND_ASSIGN(RefCountedThreadSafeBase);
michael@0: };
michael@0: 
michael@0: 
michael@0: 
michael@0: }  // namespace subtle
michael@0: 
michael@0: //
michael@0: // A base class for reference counted classes.  Otherwise, known as a cheap
michael@0: // knock-off of WebKit's RefCounted<T> class.  To use this guy just extend your
michael@0: // class from it like so:
michael@0: //
michael@0: //   class MyFoo : public base::RefCounted<MyFoo> {
michael@0: //    ...
michael@0: //   };
michael@0: //
michael@0: template <class T>
michael@0: class RefCounted : public subtle::RefCountedBase {
michael@0:  public:
michael@0:   RefCounted() { }
michael@0:   ~RefCounted() { }
michael@0: 
michael@0:   void AddRef() {
michael@0:     subtle::RefCountedBase::AddRef();
michael@0:   }
michael@0: 
michael@0:   void Release() {
michael@0:     if (subtle::RefCountedBase::Release()) {
michael@0:       delete static_cast<T*>(this);
michael@0:     }
michael@0:   }
michael@0: 
michael@0:  private:
michael@0:   DISALLOW_COPY_AND_ASSIGN(RefCounted<T>);
michael@0: };
michael@0: 
michael@0: //
michael@0: // A thread-safe variant of RefCounted<T>
michael@0: //
michael@0: //   class MyFoo : public base::RefCountedThreadSafe<MyFoo> {
michael@0: //    ...
michael@0: //   };
michael@0: //
michael@0: template <class T>
michael@0: class RefCountedThreadSafe : public subtle::RefCountedThreadSafeBase {
michael@0:  public:
michael@0:   RefCountedThreadSafe() { }
michael@0:   ~RefCountedThreadSafe() { }
michael@0: 
michael@0:   void AddRef() {
michael@0:     subtle::RefCountedThreadSafeBase::AddRef();
michael@0:   }
michael@0: 
michael@0:   void Release() {
michael@0:     if (subtle::RefCountedThreadSafeBase::Release()) {
michael@0:       delete static_cast<T*>(this);
michael@0:     }
michael@0:   }
michael@0: 
michael@0:  private:
michael@0:   DISALLOW_COPY_AND_ASSIGN(RefCountedThreadSafe<T>);
michael@0: };
michael@0: 
michael@0: //
michael@0: // A wrapper for some piece of data so we can place other things in
michael@0: // scoped_refptrs<>.
michael@0: //
michael@0: template<typename T>
michael@0: class RefCountedData : public base::RefCounted< base::RefCountedData<T> > {
michael@0:  public:
michael@0:   RefCountedData() : data() {}
michael@0:   RefCountedData(const T& in_value) : data(in_value) {}
michael@0: 
michael@0:   T data;
michael@0: };
michael@0: 
michael@0: }  // namespace base
michael@0: 
michael@0: //
michael@0: // A smart pointer class for reference counted objects.  Use this class instead
michael@0: // of calling AddRef and Release manually on a reference counted object to
michael@0: // avoid common memory leaks caused by forgetting to Release an object
michael@0: // reference.  Sample usage:
michael@0: //
michael@0: //   class MyFoo : public RefCounted<MyFoo> {
michael@0: //    ...
michael@0: //   };
michael@0: //
michael@0: //   void some_function() {
michael@0: //     scoped_refptr<MyFoo> foo = new MyFoo();
michael@0: //     foo->Method(param);
michael@0: //     // |foo| is released when this function returns
michael@0: //   }
michael@0: //
michael@0: //   void some_other_function() {
michael@0: //     scoped_refptr<MyFoo> foo = new MyFoo();
michael@0: //     ...
michael@0: //     foo = NULL;  // explicitly releases |foo|
michael@0: //     ...
michael@0: //     if (foo)
michael@0: //       foo->Method(param);
michael@0: //   }
michael@0: //
michael@0: // The above examples show how scoped_refptr<T> acts like a pointer to T.
michael@0: // Given two scoped_refptr<T> classes, it is also possible to exchange
michael@0: // references between the two objects, like so:
michael@0: //
michael@0: //   {
michael@0: //     scoped_refptr<MyFoo> a = new MyFoo();
michael@0: //     scoped_refptr<MyFoo> b;
michael@0: //
michael@0: //     b.swap(a);
michael@0: //     // now, |b| references the MyFoo object, and |a| references NULL.
michael@0: //   }
michael@0: //
michael@0: // To make both |a| and |b| in the above example reference the same MyFoo
michael@0: // object, simply use the assignment operator:
michael@0: //
michael@0: //   {
michael@0: //     scoped_refptr<MyFoo> a = new MyFoo();
michael@0: //     scoped_refptr<MyFoo> b;
michael@0: //
michael@0: //     b = a;
michael@0: //     // now, |a| and |b| each own a reference to the same MyFoo object.
michael@0: //   }
michael@0: //
michael@0: template <class T>
michael@0: class scoped_refptr {
michael@0:  public:
michael@0:   scoped_refptr() : ptr_(NULL) {
michael@0:   }
michael@0: 
michael@0:   scoped_refptr(T* p) : ptr_(p) {
michael@0:     if (ptr_)
michael@0:       ptr_->AddRef();
michael@0:   }
michael@0: 
michael@0:   scoped_refptr(const scoped_refptr<T>& r) : ptr_(r.ptr_) {
michael@0:     if (ptr_)
michael@0:       ptr_->AddRef();
michael@0:   }
michael@0: 
michael@0:   ~scoped_refptr() {
michael@0:     if (ptr_)
michael@0:       ptr_->Release();
michael@0:   }
michael@0: 
michael@0:   T* get() const { return ptr_; }
michael@0:   operator T*() const { return ptr_; }
michael@0:   T* operator->() const { return ptr_; }
michael@0: 
michael@0:   scoped_refptr<T>& operator=(T* p) {
michael@0:     // AddRef first so that self assignment should work
michael@0:     if (p)
michael@0:       p->AddRef();
michael@0:     if (ptr_ )
michael@0:       ptr_ ->Release();
michael@0:     ptr_ = p;
michael@0:     return *this;
michael@0:   }
michael@0: 
michael@0:   scoped_refptr<T>& operator=(const scoped_refptr<T>& r) {
michael@0:     return *this = r.ptr_;
michael@0:   }
michael@0: 
michael@0:   void swap(T** pp) {
michael@0:     T* p = ptr_;
michael@0:     ptr_ = *pp;
michael@0:     *pp = p;
michael@0:   }
michael@0: 
michael@0:   void swap(scoped_refptr<T>& r) {
michael@0:     swap(&r.ptr_);
michael@0:   }
michael@0: 
michael@0:  protected:
michael@0:   T* ptr_;
michael@0: };
michael@0: 
michael@0: #endif  // BASE_REF_COUNTED_H_