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Diffstat (limited to 'base/memory/ref_counted.h')
-rw-r--r-- | base/memory/ref_counted.h | 299 |
1 files changed, 299 insertions, 0 deletions
diff --git a/base/memory/ref_counted.h b/base/memory/ref_counted.h new file mode 100644 index 0000000..1207ed4 --- /dev/null +++ b/base/memory/ref_counted.h @@ -0,0 +1,299 @@ +// Copyright (c) 2011 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_MEMORY_REF_COUNTED_H_ +#define BASE_MEMORY_REF_COUNTED_H_ +#pragma once + +#include "base/atomic_ref_count.h" +#include "base/base_api.h" +#include "base/threading/thread_collision_warner.h" + +namespace base { + +namespace subtle { + +class BASE_API 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 BASE_API 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_MEMORY_REF_COUNTED_H_ |