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Diffstat (limited to 'chromium/base/mac/scoped_typeref.h')
-rw-r--r-- | chromium/base/mac/scoped_typeref.h | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/chromium/base/mac/scoped_typeref.h b/chromium/base/mac/scoped_typeref.h new file mode 100644 index 00000000000..61ee3119817 --- /dev/null +++ b/chromium/base/mac/scoped_typeref.h @@ -0,0 +1,132 @@ +// Copyright 2014 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_MAC_SCOPED_TYPEREF_H_ +#define BASE_MAC_SCOPED_TYPEREF_H_ + +#include "base/basictypes.h" +#include "base/compiler_specific.h" +#include "base/logging.h" +#include "base/memory/scoped_policy.h" + +namespace base { + +// ScopedTypeRef<> is patterned after scoped_ptr<>, but maintains a ownership +// of a reference to any type that is maintained by Retain and Release methods. +// +// The Traits structure must provide the Retain and Release methods for type T. +// A default ScopedTypeRefTraits is used but not defined, and should be defined +// for each type to use this interface. For example, an appropriate definition +// of ScopedTypeRefTraits for CGLContextObj would be: +// +// template<> +// struct ScopedTypeRefTraits<CGLContextObj> { +// void Retain(CGLContextObj object) { CGLContextRetain(object); } +// void Release(CGLContextObj object) { CGLContextRelease(object); } +// }; +// +// For the many types that have pass-by-pointer create functions, the function +// InitializeInto() is provided to allow direct initialization and assumption +// of ownership of the object. For example, continuing to use the above +// CGLContextObj specialization: +// +// base::ScopedTypeRef<CGLContextObj> context; +// CGLCreateContext(pixel_format, share_group, context.InitializeInto()); +// +// For initialization with an existing object, the caller may specify whether +// the ScopedTypeRef<> being initialized is assuming the caller's existing +// ownership of the object (and should not call Retain in initialization) or if +// it should not assume this ownership and must create its own (by calling +// Retain in initialization). This behavior is based on the |policy| parameter, +// with |ASSUME| for the former and |RETAIN| for the latter. The default policy +// is to |ASSUME|. + +template<typename T> +struct ScopedTypeRefTraits; + +template<typename T, typename Traits = ScopedTypeRefTraits<T>> +class ScopedTypeRef { + public: + typedef T element_type; + + ScopedTypeRef( + T object = NULL, + base::scoped_policy::OwnershipPolicy policy = base::scoped_policy::ASSUME) + : object_(object) { + if (object_ && policy == base::scoped_policy::RETAIN) + Traits::Retain(object_); + } + + ScopedTypeRef(const ScopedTypeRef<T, Traits>& that) + : object_(that.object_) { + if (object_) + Traits::Retain(object_); + } + + ~ScopedTypeRef() { + if (object_) + Traits::Release(object_); + } + + ScopedTypeRef& operator=(const ScopedTypeRef<T, Traits>& that) { + reset(that.get(), base::scoped_policy::RETAIN); + return *this; + } + + // This is to be used only to take ownership of objects that are created + // by pass-by-pointer create functions. To enforce this, require that the + // object be reset to NULL before this may be used. + T* InitializeInto() WARN_UNUSED_RESULT { + DCHECK(!object_); + return &object_; + } + + void reset(T object = NULL, + base::scoped_policy::OwnershipPolicy policy = + base::scoped_policy::ASSUME) { + if (object && policy == base::scoped_policy::RETAIN) + Traits::Retain(object); + if (object_) + Traits::Release(object_); + object_ = object; + } + + bool operator==(T that) const { + return object_ == that; + } + + bool operator!=(T that) const { + return object_ != that; + } + + operator T() const { + return object_; + } + + T get() const { + return object_; + } + + void swap(ScopedTypeRef& that) { + T temp = that.object_; + that.object_ = object_; + object_ = temp; + } + + // ScopedTypeRef<>::release() is like scoped_ptr<>::release. It is NOT + // a wrapper for Release(). To force a ScopedTypeRef<> object to call + // Release(), use ScopedTypeRef<>::reset(). + T release() WARN_UNUSED_RESULT { + T temp = object_; + object_ = NULL; + return temp; + } + + private: + T object_; +}; + +} // namespace base + +#endif // BASE_MAC_SCOPED_TYPEREF_H_ |