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297 lines
10 KiB
C++
297 lines
10 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/* DEPRECATED: Use UniquePtr.h instead. */
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#ifndef mozilla_Scoped_h
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#define mozilla_Scoped_h
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/*
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* DEPRECATED: Use UniquePtr.h instead.
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*
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* Resource Acquisition Is Initialization is a programming idiom used
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* to write robust code that is able to deallocate resources properly,
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* even in presence of execution errors or exceptions that need to be
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* propagated. The Scoped* classes defined in this header perform the
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* deallocation of the resource they hold once program execution
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* reaches the end of the scope for which they have been defined.
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*
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* This header provides the following RAII classes:
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*
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* - |ScopedFreePtr| - a container for a pointer, that automatically calls
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* |free()| at the end of the scope;
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* - |ScopedDeletePtr| - a container for a pointer, that automatically calls
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* |delete| at the end of the scope;
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*
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* |ScopedDeleteArray| is removed in favor of |UniquePtr<T[]>|.
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*
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* The general scenario for each of the RAII classes is the following:
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*
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* ScopedClass foo(create_value());
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* // ... In this scope, |foo| is defined. Use |foo.get()| or |foo.rwget()|
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* to access the value.
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* // ... In case of |return| or |throw|, |foo| is deallocated automatically.
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* // ... If |foo| needs to be returned or stored, use |foo.forget()|
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*
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* Note that the RAII classes defined in this header do _not_ perform any form
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* of reference-counting or garbage-collection. These classes have exactly two
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* behaviors:
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*
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* - if |forget()| has not been called, the resource is always deallocated at
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* the end of the scope;
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* - if |forget()| has been called, any control on the resource is unbound
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* and the resource is not deallocated by the class.
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*
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* Extension:
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*
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* In addition, this header provides class |Scoped| and macros |SCOPED_TEMPLATE|
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* and |MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLATE| to simplify the definition
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* of RAII classes for other scenarios. These macros have been used to
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* automatically close file descriptors/file handles when reaching the end of
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* the scope, graphics contexts, etc.
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*/
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#include "mozilla/Assertions.h"
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#include "mozilla/Attributes.h"
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#include "mozilla/GuardObjects.h"
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#include "mozilla/Move.h"
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namespace mozilla {
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/*
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* Scoped is a helper to create RAII wrappers
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* Type argument |Traits| is expected to have the following structure:
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*
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* struct Traits
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* {
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* // Define the type of the value stored in the wrapper
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* typedef value_type type;
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* // Returns the value corresponding to the uninitialized or freed state
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* const static type empty();
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* // Release resources corresponding to the wrapped value
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* // This function is responsible for not releasing an |empty| value
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* const static void release(type);
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* }
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*/
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template<typename Traits>
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class Scoped
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{
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public:
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typedef typename Traits::type Resource;
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explicit Scoped(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM)
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: mValue(Traits::empty())
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{
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MOZ_GUARD_OBJECT_NOTIFIER_INIT;
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}
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explicit Scoped(const Resource& aValue
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MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
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: mValue(aValue)
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{
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MOZ_GUARD_OBJECT_NOTIFIER_INIT;
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}
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/* Move constructor. */
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explicit Scoped(Scoped&& aOther
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MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
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: mValue(Move(aOther.mValue))
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{
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MOZ_GUARD_OBJECT_NOTIFIER_INIT;
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aOther.mValue = Traits::empty();
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}
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~Scoped() { Traits::release(mValue); }
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// Constant getter
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operator const Resource&() const { return mValue; }
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const Resource& operator->() const { return mValue; }
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const Resource& get() const { return mValue; }
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// Non-constant getter.
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Resource& rwget() { return mValue; }
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/*
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* Forget the resource.
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*
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* Once |forget| has been called, the |Scoped| is neutralized, i.e. it will
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* have no effect at destruction (unless it is reset to another resource by
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* |operator=|).
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*
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* @return The original resource.
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*/
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Resource forget()
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{
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Resource tmp = mValue;
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mValue = Traits::empty();
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return tmp;
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}
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/*
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* Perform immediate clean-up of this |Scoped|.
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*
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* If this |Scoped| is currently empty, this method has no effect.
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*/
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void dispose()
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{
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Traits::release(mValue);
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mValue = Traits::empty();
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}
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bool operator==(const Resource& aOther) const { return mValue == aOther; }
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/*
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* Replace the resource with another resource.
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*
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* Calling |operator=| has the side-effect of triggering clean-up. If you do
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* not want to trigger clean-up, you should first invoke |forget|.
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*
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* @return this
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*/
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Scoped& operator=(const Resource& aOther) { return reset(aOther); }
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Scoped& reset(const Resource& aOther)
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{
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Traits::release(mValue);
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mValue = aOther;
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return *this;
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}
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/* Move assignment operator. */
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Scoped& operator=(Scoped&& aRhs)
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{
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MOZ_ASSERT(&aRhs != this, "self-move-assignment not allowed");
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this->~Scoped();
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new(this) Scoped(Move(aRhs));
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return *this;
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}
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private:
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explicit Scoped(const Scoped& aValue) = delete;
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Scoped& operator=(const Scoped& aValue) = delete;
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private:
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Resource mValue;
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MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
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};
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/*
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* SCOPED_TEMPLATE defines a templated class derived from Scoped
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* This allows to implement templates such as ScopedFreePtr.
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*
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* @param name The name of the class to define.
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* @param Traits A struct implementing clean-up. See the implementations
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* for more details.
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*/
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#define SCOPED_TEMPLATE(name, Traits) \
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template<typename Type> \
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struct name : public mozilla::Scoped<Traits<Type> > \
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{ \
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typedef mozilla::Scoped<Traits<Type> > Super; \
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typedef typename Super::Resource Resource; \
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name& operator=(Resource aRhs) \
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{ \
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Super::operator=(aRhs); \
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return *this; \
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} \
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name& operator=(name&& aRhs) \
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{ \
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Super::operator=(Move(aRhs)); \
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return *this; \
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} \
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explicit name(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM) \
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: Super(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM_TO_PARENT) \
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{} \
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explicit name(Resource aRhs \
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MOZ_GUARD_OBJECT_NOTIFIER_PARAM) \
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: Super(aRhs \
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MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT) \
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{} \
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explicit name(name&& aRhs \
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MOZ_GUARD_OBJECT_NOTIFIER_PARAM) \
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: Super(Move(aRhs) \
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MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT) \
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{} \
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private: \
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explicit name(name&) = delete; \
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name& operator=(name&) = delete; \
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};
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/*
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* ScopedFreePtr is a RAII wrapper for pointers that need to be free()d.
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*
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* struct S { ... };
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* ScopedFreePtr<S> foo = malloc(sizeof(S));
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* ScopedFreePtr<char> bar = strdup(str);
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*/
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template<typename T>
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struct ScopedFreePtrTraits
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{
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typedef T* type;
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static T* empty() { return nullptr; }
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static void release(T* aPtr) { free(aPtr); }
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};
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SCOPED_TEMPLATE(ScopedFreePtr, ScopedFreePtrTraits)
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/*
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* ScopedDeletePtr is a RAII wrapper for pointers that need to be deleted.
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*
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* struct S { ... };
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* ScopedDeletePtr<S> foo = new S();
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*/
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template<typename T>
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struct ScopedDeletePtrTraits : public ScopedFreePtrTraits<T>
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{
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static void release(T* aPtr) { delete aPtr; }
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};
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SCOPED_TEMPLATE(ScopedDeletePtr, ScopedDeletePtrTraits)
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/*
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* MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLATE makes it easy to create scoped
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* pointers for types with custom deleters; just overload
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* TypeSpecificDelete(T*) in the same namespace as T to call the deleter for
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* type T.
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*
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* @param name The name of the class to define.
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* @param Type A struct implementing clean-up. See the implementations
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* for more details.
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* *param Deleter The function that is used to delete/destroy/free a
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* non-null value of Type*.
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*
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* Example:
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*
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* MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLATE(ScopedPRFileDesc, PRFileDesc, \
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* PR_Close)
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* ...
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* {
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* ScopedPRFileDesc file(PR_OpenFile(...));
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* ...
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* } // file is closed with PR_Close here
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*/
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#define MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLATE(name, Type, Deleter) \
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template <> inline void TypeSpecificDelete(Type* aValue) { Deleter(aValue); } \
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typedef ::mozilla::TypeSpecificScopedPointer<Type> name;
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template <typename T> void TypeSpecificDelete(T* aValue);
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template <typename T>
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struct TypeSpecificScopedPointerTraits
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{
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typedef T* type;
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static type empty() { return nullptr; }
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static void release(type aValue)
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{
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if (aValue) {
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TypeSpecificDelete(aValue);
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}
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}
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};
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SCOPED_TEMPLATE(TypeSpecificScopedPointer, TypeSpecificScopedPointerTraits)
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} /* namespace mozilla */
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#endif /* mozilla_Scoped_h */
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