base/ref_counted.h - chromium/src - Git at Google

 // Copyright (c) 2010 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_
 #pragma once

 #include "base/atomic_ref_count.h"
 #include "base/thread_collision_warner.h"

 namespace base {

 namespace subtle {

 class RefCountedBase {
  public:
   static bool ImplementsThreadSafeReferenceCounting() { return false; }

   bool HasOneRef() const { return ref_count_ == 1; }

  protected:
   RefCountedBase();
   ~RefCountedBase();

   void AddRef() const;

   // Returns true if the object should self-delete.
   bool Release() const;

  private:
   mutable int ref_count_;
 #ifndef NDEBUG
   mutable bool in_dtor_;
 #endif

   DFAKE_MUTEX(add_release_);

   DISALLOW_COPY_AND_ASSIGN(RefCountedBase);
 };

 class RefCountedThreadSafeBase {
  public:
   static bool ImplementsThreadSafeReferenceCounting() { return true; }

   bool HasOneRef() const;

  protected:
   RefCountedThreadSafeBase();
   ~RefCountedThreadSafeBase();

   void AddRef() const;

   // Returns true if the object should self-delete.
   bool Release() const;

  private:
   mutable AtomicRefCount ref_count_;
 #ifndef NDEBUG
   mutable bool in_dtor_;
 #endif

   DISALLOW_COPY_AND_ASSIGN(RefCountedThreadSafeBase);
 };

 }  // namespace subtle

 //
 // A base class for reference counted classes.  Otherwise, known as a cheap
 // knock-off of WebKit's RefCounted<T> class.  To use this guy just extend your
 // class from it like so:
 //
 //   class MyFoo : public base::RefCounted<MyFoo> {
 //    ...
 //    private:
 //     friend class base::RefCounted<MyFoo>;
 //     ~MyFoo();
 //   };
 //
 // You should always make your destructor private, to avoid any code deleting
 // the object accidently while there are references to it.
 template <class T>
 class RefCounted : public subtle::RefCountedBase {
  public:
   RefCounted() { }
   ~RefCounted() { }

   void AddRef() const {
     subtle::RefCountedBase::AddRef();
   }

   void Release() const {
     if (subtle::RefCountedBase::Release()) {
       delete static_cast<const 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(const 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> {
 //    ...
 //   };
 //
 // If you're using the default trait, then you should add compile time
 // asserts that no one else is deleting your object.  i.e.
 //    private:
 //     friend class base::RefCountedThreadSafe<MyFoo>;
 //     ~MyFoo();
 template <class T, typename Traits = DefaultRefCountedThreadSafeTraits<T> >
 class RefCountedThreadSafe : public subtle::RefCountedThreadSafeBase {
  public:
   RefCountedThreadSafe() { }
   ~RefCountedThreadSafe() { }

   void AddRef() const {
     subtle::RefCountedThreadSafeBase::AddRef();
   }

   void Release() const {
     if (subtle::RefCountedThreadSafeBase::Release()) {
       Traits::Destruct(static_cast<const T*>(this));
     }
   }

  private:
   friend struct DefaultRefCountedThreadSafeTraits<T>;
   static void DeleteInternal(const 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() {}
   RefCountedData(const T& in_value) : data(in_value) {}

   T data;
 };

 }  // namespace base

 //
 // A smart pointer class for reference counted objects.  Use this class instead
 // of calling AddRef and Release manually on a reference counted object to
 // avoid common memory leaks caused by forgetting to Release an object
 // reference.  Sample usage:
 //
 //   class MyFoo : public RefCounted<MyFoo> {
 //    ...
 //   };
 //
 //   void some_function() {
 //     scoped_refptr<MyFoo> foo = new MyFoo();
 //     foo->Method(param);
 //     // |foo| is released when this function returns
 //   }
 //
 //   void some_other_function() {
 //     scoped_refptr<MyFoo> foo = new MyFoo();
 //     ...
 //     foo = NULL;  // explicitly releases |foo|
 //     ...
 //     if (foo)
 //       foo->Method(param);
 //   }
 //
 // The above examples show how scoped_refptr<T> acts like a pointer to T.
 // Given two scoped_refptr<T> classes, it is also possible to exchange
 // references between the two objects, like so:
 //
 //   {
 //     scoped_refptr<MyFoo> a = new MyFoo();
 //     scoped_refptr<MyFoo> b;
 //
 //     b.swap(a);
 //     // now, |b| references the MyFoo object, and |a| references NULL.
 //   }
 //
 // To make both |a| and |b| in the above example reference the same MyFoo
 // object, simply use the assignment operator:
 //
 //   {
 //     scoped_refptr<MyFoo> a = new MyFoo();
 //     scoped_refptr<MyFoo> b;
 //
 //     b = a;
 //     // now, |a| and |b| each own a reference to the same MyFoo object.
 //   }
 //
 template <class T>
 class scoped_refptr {
  public:
   scoped_refptr() : ptr_(NULL) {
   }

   scoped_refptr(T* p) : ptr_(p) {
     if (ptr_)
       ptr_->AddRef();
   }

   scoped_refptr(const scoped_refptr<T>& r) : ptr_(r.ptr_) {
     if (ptr_)
       ptr_->AddRef();
   }

   template <typename U>
   scoped_refptr(const scoped_refptr<U>& r) : ptr_(r.get()) {
     if (ptr_)
       ptr_->AddRef();
   }

   ~scoped_refptr() {
     if (ptr_)
       ptr_->Release();
   }

   T* get() const { return ptr_; }
   operator T*() const { return ptr_; }
   T* operator->() const { return ptr_; }

   // Release a pointer.
   // The return value is the current pointer held by this object.
   // If this object holds a NULL pointer, the return value is NULL.
   // After this operation, this object will hold a NULL pointer,
   // and will not own the object any more.
   T* release() {
     T* retVal = ptr_;
     ptr_ = NULL;
     return retVal;
   }

   scoped_refptr<T>& operator=(T* p) {
     // AddRef first so that self assignment should work
     if (p)
       p->AddRef();
     if (ptr_ )
       ptr_ ->Release();
     ptr_ = p;
     return *this;
   }

   scoped_refptr<T>& operator=(const scoped_refptr<T>& r) {
     return *this = r.ptr_;
   }

   template <typename U>
   scoped_refptr<T>& operator=(const scoped_refptr<U>& r) {
     return *this = r.get();
   }

   void swap(T** pp) {
     T* p = ptr_;
     ptr_ = *pp;
     *pp = p;
   }

   void swap(scoped_refptr<T>& r) {
     swap(&r.ptr_);
   }

  protected:
   T* ptr_;
 };

 // Handy utility for creating a scoped_refptr<T> out of a T* explicitly without
 // having to retype all the template arguments
 template <typename T>
 scoped_refptr<T> make_scoped_refptr(T* t) {
   return scoped_refptr<T>(t);
 }

 #endif  // BASE_REF_COUNTED_H_
	// Copyright (c) 2010 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_
	#pragma once

	#include "base/atomic_ref_count.h"
	#include "base/thread_collision_warner.h"

	namespace base {

	namespace subtle {

	class RefCountedBase {
	public:
	static bool ImplementsThreadSafeReferenceCounting() { return false; }

	bool HasOneRef() const { return ref_count_ == 1; }

	protected:
	RefCountedBase();
	~RefCountedBase();

	void AddRef() const;

	// Returns true if the object should self-delete.
	bool Release() const;

	private:
	mutable int ref_count_;
	#ifndef NDEBUG
	mutable bool in_dtor_;
	#endif

	DFAKE_MUTEX(add_release_);

	DISALLOW_COPY_AND_ASSIGN(RefCountedBase);
	};

	class RefCountedThreadSafeBase {
	public:
	static bool ImplementsThreadSafeReferenceCounting() { return true; }

	bool HasOneRef() const;

	protected:
	RefCountedThreadSafeBase();
	~RefCountedThreadSafeBase();

	void AddRef() const;

	// Returns true if the object should self-delete.
	bool Release() const;

	private:
	mutable AtomicRefCount ref_count_;
	#ifndef NDEBUG
	mutable bool in_dtor_;
	#endif

	DISALLOW_COPY_AND_ASSIGN(RefCountedThreadSafeBase);
	};

	} // namespace subtle

	//
	// A base class for reference counted classes. Otherwise, known as a cheap
	// knock-off of WebKit's RefCounted<T> class. To use this guy just extend your
	// class from it like so:
	//
	// class MyFoo : public base::RefCounted<MyFoo> {
	// ...
	// private:
	// friend class base::RefCounted<MyFoo>;
	// ~MyFoo();
	// };
	//
	// You should always make your destructor private, to avoid any code deleting
	// the object accidently while there are references to it.
	template <class T>
	class RefCounted : public subtle::RefCountedBase {
	public:
	RefCounted() { }
	~RefCounted() { }

	void AddRef() const {
	subtle::RefCountedBase::AddRef();
	}

	void Release() const {
	if (subtle::RefCountedBase::Release()) {
	delete static_cast<const 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(const 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> {
	// ...
	// };
	//
	// If you're using the default trait, then you should add compile time
	// asserts that no one else is deleting your object. i.e.
	// private:
	// friend class base::RefCountedThreadSafe<MyFoo>;
	// ~MyFoo();
	template <class T, typename Traits = DefaultRefCountedThreadSafeTraits<T> >
	class RefCountedThreadSafe : public subtle::RefCountedThreadSafeBase {
	public:
	RefCountedThreadSafe() { }
	~RefCountedThreadSafe() { }

	void AddRef() const {
	subtle::RefCountedThreadSafeBase::AddRef();
	}

	void Release() const {
	if (subtle::RefCountedThreadSafeBase::Release()) {
	Traits::Destruct(static_cast<const T*>(this));
	}
	}

	private:
	friend struct DefaultRefCountedThreadSafeTraits<T>;
	static void DeleteInternal(const 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() {}
	RefCountedData(const T& in_value) : data(in_value) {}

	T data;
	};

	} // namespace base

	//
	// A smart pointer class for reference counted objects. Use this class instead
	// of calling AddRef and Release manually on a reference counted object to
	// avoid common memory leaks caused by forgetting to Release an object
	// reference. Sample usage:
	//
	// class MyFoo : public RefCounted<MyFoo> {
	// ...
	// };
	//
	// void some_function() {
	// scoped_refptr<MyFoo> foo = new MyFoo();
	// foo->Method(param);
	// // \|foo\| is released when this function returns
	// }
	//
	// void some_other_function() {
	// scoped_refptr<MyFoo> foo = new MyFoo();
	// ...
	// foo = NULL; // explicitly releases \|foo\|
	// ...
	// if (foo)
	// foo->Method(param);
	// }
	//
	// The above examples show how scoped_refptr<T> acts like a pointer to T.
	// Given two scoped_refptr<T> classes, it is also possible to exchange
	// references between the two objects, like so:
	//
	// {
	// scoped_refptr<MyFoo> a = new MyFoo();
	// scoped_refptr<MyFoo> b;
	//
	// b.swap(a);
	// // now, \|b\| references the MyFoo object, and \|a\| references NULL.
	// }
	//
	// To make both \|a\| and \|b\| in the above example reference the same MyFoo
	// object, simply use the assignment operator:
	//
	// {
	// scoped_refptr<MyFoo> a = new MyFoo();
	// scoped_refptr<MyFoo> b;
	//
	// b = a;
	// // now, \|a\| and \|b\| each own a reference to the same MyFoo object.
	// }
	//
	template <class T>
	class scoped_refptr {
	public:
	scoped_refptr() : ptr_(NULL) {
	}

	scoped_refptr(T* p) : ptr_(p) {
	if (ptr_)
	ptr_->AddRef();
	}

	scoped_refptr(const scoped_refptr<T>& r) : ptr_(r.ptr_) {
	if (ptr_)
	ptr_->AddRef();
	}

	template <typename U>
	scoped_refptr(const scoped_refptr<U>& r) : ptr_(r.get()) {
	if (ptr_)
	ptr_->AddRef();
	}

	~scoped_refptr() {
	if (ptr_)
	ptr_->Release();
	}

	T* get() const { return ptr_; }
	operator T*() const { return ptr_; }
	T* operator->() const { return ptr_; }

	// Release a pointer.
	// The return value is the current pointer held by this object.
	// If this object holds a NULL pointer, the return value is NULL.
	// After this operation, this object will hold a NULL pointer,
	// and will not own the object any more.
	T* release() {
	T* retVal = ptr_;
	ptr_ = NULL;
	return retVal;
	}

	scoped_refptr<T>& operator=(T* p) {
	// AddRef first so that self assignment should work
	if (p)
	p->AddRef();
	if (ptr_ )
	ptr_ ->Release();
	ptr_ = p;
	return *this;
	}

	scoped_refptr<T>& operator=(const scoped_refptr<T>& r) {
	return *this = r.ptr_;
	}

	template <typename U>
	scoped_refptr<T>& operator=(const scoped_refptr<U>& r) {
	return *this = r.get();
	}

	void swap(T** pp) {
	T* p = ptr_;
	ptr_ = *pp;
	*pp = p;
	}

	void swap(scoped_refptr<T>& r) {
	swap(&r.ptr_);
	}

	protected:
	T* ptr_;
	};

	// Handy utility for creating a scoped_refptr<T> out of a T* explicitly without
	// having to retype all the template arguments
	template <typename T>
	scoped_refptr<T> make_scoped_refptr(T* t) {
	return scoped_refptr<T>(t);
	}

	#endif // BASE_REF_COUNTED_H_