Quelle StaticPtr.h Sprache: C

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_StaticPtr_h
#define mozilla_StaticPtr_h

#include "mozilla/AlreadyAddRefed.h"
#include "mozilla/Assertions.h"
#include "mozilla/Attributes.h"
#include "mozilla/RefPtr.h"

namespace mozilla {

/**
* StaticAutoPtr and StaticRefPtr are like UniquePtr and RefPtr, except they
* are suitable for use as global variables.
*
* In particular, a global instance of Static{Auto,Ref}Ptr doesn't cause the
* compiler to emit a static initializer.
*
* Since the compiler guarantees that all global variables are initialized to
* 0, the default constexpr constructors will result in no actual code being
* generated. Since we rely on this, the clang plugin, run as part of our
* "static analysis" builds, makes it a compile-time error to use
* Static{Auto,Ref}Ptr as anything except a global variable.
*
* Static{Auto,Ref}Ptr have a limited interface as compared to ns{Auto,Ref}Ptr;
* this is intentional, since their range of acceptable uses is smaller.
*/

template <class T>
class MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS StaticAutoPtr {
public:
 constexpr StaticAutoPtr() = default;
 StaticAutoPtr(const StaticAutoPtr&) = delete;

 StaticAutoPtr<T>& operator=(T* aRhs) {
 Assign(aRhs);
 return *this;
 }

 T* get() const { return mRawPtr; }

 operator T*() const { return get(); }

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

 T& operator*() const { return *get(); }

 T* forget() {
 T* temp = mRawPtr;
 mRawPtr = nullptr;
 return temp;
 }

private:
 void Assign(T* aNewPtr) {
 MOZ_ASSERT(!aNewPtr || mRawPtr != aNewPtr);
 T* oldPtr = mRawPtr;
 mRawPtr = aNewPtr;
 delete oldPtr;
 }

 T* mRawPtr = nullptr;
};

template <class T>
class MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS StaticRefPtr {
public:
 constexpr StaticRefPtr() = default;
 StaticRefPtr(const StaticRefPtr&) = delete;

 StaticRefPtr<T>& operator=(T* aRhs) {
 AssignWithAddref(aRhs);
 return *this;
 }

 StaticRefPtr<T>& operator=(const StaticRefPtr<T>& aRhs) {
 return (this = aRhs.mRawPtr);
 }

 StaticRefPtr<T>& operator=(already_AddRefed<T>& aRhs) {
 AssignAssumingAddRef(aRhs.take());
 return *this;
 }

 template <typename U>
 StaticRefPtr<T>& operator=(RefPtr&& aRhs) {
 AssignAssumingAddRef(aRhs.forget().take());
 return *this;
 }

 StaticRefPtr<T>& operator=(already_AddRefed<T>&& aRhs) {
 AssignAssumingAddRef(aRhs.take());
 return *this;
 }

 already_AddRefed<T> forget() {
 T* temp = mRawPtr;
 mRawPtr = nullptr;
 return already_AddRefed<T>(temp);
 }

 T* get() const { return mRawPtr; }

 operator T*() const { return get(); }

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

 T& operator*() const { return *get(); }

private:
 void AssignWithAddref(T* aNewPtr) {
 if (aNewPtr) {
 RefPtrTraits<T>::AddRef(aNewPtr);
 }
 AssignAssumingAddRef(aNewPtr);
 }

 void AssignAssumingAddRef(T* aNewPtr) {
 T* oldPtr = mRawPtr;
 mRawPtr = aNewPtr;
 if (oldPtr) {
 RefPtrTraits<T>::Release(oldPtr);
 }
 }

 T* MOZ_OWNING_REF mRawPtr = nullptr;
};

namespace StaticPtr_internal {
class Zero;
} // namespace StaticPtr_internal

#define REFLEXIVE_EQUALITY_OPERATORS(type1, type2, eq_fn, ...) \
 template <__VA_ARGS__> \
 inline bool operator==(type1 lhs, type2 rhs) { \
 return eq_fn; \
 } \
 \
 template <__VA_ARGS__> \
 inline bool operator==(type2 lhs, type1 rhs) { \
 return rhs == lhs; \
 } \
 \
 template <__VA_ARGS__> \
 inline bool operator!=(type1 lhs, type2 rhs) { \
 return !(lhs == rhs); \
 } \
 \
 template <__VA_ARGS__> \
 inline bool operator!=(type2 lhs, type1 rhs) { \
 return !(lhs == rhs); \
 }

// StaticAutoPtr (in)equality operators

template <class T, class U>
inline bool operator==(const StaticAutoPtr<T>& aLhs,
 const StaticAutoPtr& aRhs) {
 return aLhs.get() == aRhs.get();
}

template <class T, class U>
inline bool operator!=(const StaticAutoPtr<T>& aLhs,
 const StaticAutoPtr& aRhs) {
 return !(aLhs == aRhs);
}

REFLEXIVE_EQUALITY_OPERATORS(const StaticAutoPtr<T>&, const U*,
 lhs.get() == rhs, class T, class U)

REFLEXIVE_EQUALITY_OPERATORS(const StaticAutoPtr<T>&, U*, lhs.get() == rhs,
 class T, class U)

// Let us compare StaticAutoPtr to 0.
REFLEXIVE_EQUALITY_OPERATORS(const StaticAutoPtr<T>&, StaticPtr_internal::Zero*,
 lhs.get() == nullptr, class T)

// StaticRefPtr (in)equality operators

template <class T, class U>
inline bool operator==(const StaticRefPtr<T>& aLhs,
 const StaticRefPtr& aRhs) {
 return aLhs.get() == aRhs.get();
}

template <class T, class U>
inline bool operator!=(const StaticRefPtr<T>& aLhs,
 const StaticRefPtr& aRhs) {
 return !(aLhs == aRhs);
}

REFLEXIVE_EQUALITY_OPERATORS(const StaticRefPtr<T>&, const U*, lhs.get() == rhs,
 class T, class U)

REFLEXIVE_EQUALITY_OPERATORS(const StaticRefPtr<T>&, U*, lhs.get() == rhs,
 class T, class U)

// Let us compare StaticRefPtr to 0.
REFLEXIVE_EQUALITY_OPERATORS(const StaticRefPtr<T>&, StaticPtr_internal::Zero*,
 lhs.get() == nullptr, class T)

#undef REFLEXIVE_EQUALITY_OPERATORS

} // namespace mozilla

// Declared in mozilla/RefPtr.h
template <class T>
template <class U>
RefPtr<T>::RefPtr(const mozilla::StaticRefPtr& aOther)
 : RefPtr(aOther.get()) {}

template <class T>
template <class U>
RefPtr<T>& RefPtr<T>::operator=(const mozilla::StaticRefPtr& aOther) {
 return operator=(aOther.get());
}

template <class T>
inline already_AddRefed<T> do_AddRef(const mozilla::StaticRefPtr<T>& aObj) {
 RefPtr<T> ref(aObj);
 return ref.forget();
}

#endif

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