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/* -*- 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/. */
/* DEPRECATED: Use UniquePtr.h instead. */
#ifndef mozilla_Scoped_h
#define mozilla_Scoped_h
/*
* DEPRECATED: Use UniquePtr.h instead.
*
* Resource Acquisition Is Initialization is a programming idiom used
* to write robust code that is able to deallocate resources properly,
* even in presence of execution errors or exceptions that need to be
* propagated. The Scoped* classes defined via the |SCOPED_TEMPLATE|
* and |MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLTE| macros perform the
* deallocation of the resource they hold once program execution
* reaches the end of the scope for which they have been defined.
* These macros have been used to automatically close file
* descriptors/file handles when reaching the end of the scope,
* graphics contexts, etc.
*
* The general scenario for RAII classes created by the above macros
* is the following:
*
* ScopedClass foo(create_value());
* // ... In this scope, |foo| is defined. Use |foo.get()| or |foo.rwget()|
* to access the value.
* // ... In case of |return| or |throw|, |foo| is deallocated automatically.
* // ... If |foo| needs to be returned or stored, use |foo.forget()|
*
* Note that the RAII classes defined in this header do _not_ perform any form
* of reference-counting or garbage-collection. These classes have exactly two
* behaviors:
*
* - if |forget()| has not been called, the resource is always deallocated at
* the end of the scope;
* - if |forget()| has been called, any control on the resource is unbound
* and the resource is not deallocated by the class.
*/
#include <utility>
#include "mozilla/Assertions.h"
#include "mozilla/Attributes.h"
namespace mozilla {
/*
* Scoped is a helper to create RAII wrappers
* Type argument |Traits| is expected to have the following structure:
*
* struct Traits
* {
* // Define the type of the value stored in the wrapper
* typedef value_type type;
* // Returns the value corresponding to the uninitialized or freed state
* const static type empty();
* // Release resources corresponding to the wrapped value
* // This function is responsible for not releasing an |empty| value
* const static void release(type);
* }
*/
template <typename Traits>
class MOZ_NON_TEMPORARY_CLASS Scoped {
public:
typedef typename Traits::type Resource;
explicit Scoped() : mValue(Traits::empty()) {}
explicit Scoped(const Resource& aValue) : mValue(aValue) {}
/* Move constructor. */
Scoped(Scoped&& aOther) : mValue(std::move(aOther.mValue)) {
aOther.mValue = Traits::empty();
}
~Scoped() { Traits::release(mValue); }
// Constant getter
operator const Resource&() const { return mValue; }
const Resource& operator->() const { return mValue; }
const Resource& get() const { return mValue; }
// Non-constant getter.
Resource& rwget() { return mValue; }
/*
* Forget the resource.
*
* Once |forget| has been called, the |Scoped| is neutralized, i.e. it will
* have no effect at destruction (unless it is reset to another resource by
* |operator=|).
*
* @return The original resource.
*/
Resource forget() {
Resource tmp = mValue;
mValue = Traits::empty();
return tmp;
}
/*
* Perform immediate clean-up of this |Scoped|.
*
* If this |Scoped| is currently empty, this method has no effect.
*/
void dispose() {
Traits::release(mValue);
mValue = Traits::empty();
}
bool operator==(const Resource& aOther) const { return mValue == aOther; }
/*
* Replace the resource with another resource.
*
* Calling |operator=| has the side-effect of triggering clean-up. If you do
* not want to trigger clean-up, you should first invoke |forget|.
*
* @return this
*/
Scoped& operator=(const Resource& aOther) { return reset(aOther); }
Scoped& reset(const Resource& aOther) {
Traits::release(mValue);
mValue = aOther;
return *this;
}
/* Move assignment operator. */
Scoped& operator=(Scoped&& aRhs) {
MOZ_ASSERT(&aRhs != this, "self-move-assignment not allowed");
this->~Scoped();
new (this) Scoped(std::move(aRhs));
return *this;
}
private:
explicit Scoped(const Scoped& aValue) = delete;
Scoped& operator=(const Scoped& aValue) = delete;
private:
Resource mValue;
};
/*
* SCOPED_TEMPLATE defines a templated class derived from Scoped
* This allows to implement templates such as ScopedFreePtr.
*
* @param name The name of the class to define.
* @param Traits A struct implementing clean-up. See the implementations
* for more details.
*/
#define SCOPED_TEMPLATE(name, Traits) \
template <typename Type> \
struct MOZ_NON_TEMPORARY_CLASS name \
: public mozilla::Scoped<Traits<Type> > { \
typedef mozilla::Scoped<Traits<Type> > Super; \
typedef typename Super::Resource Resource; \
name& operator=(Resource aRhs) { \
Super::operator=(aRhs); \
return *this; \
} \
name& operator=(name&& aRhs) = default; \
\
explicit name() : Super() {} \
explicit name(Resource aRhs) : Super(aRhs) {} \
name(name&& aRhs) : Super(std::move(aRhs)) {} \
\
private: \
explicit name(const name&) = delete; \
name& operator=(const name&) = delete; \
};
/*
* MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLATE makes it easy to create scoped
* pointers for types with custom deleters; just overload
* TypeSpecificDelete(T*) in the same namespace as T to call the deleter for
* type T.
*
* @param name The name of the class to define.
* @param Type A struct implementing clean-up. See the implementations
* for more details.
* *param Deleter The function that is used to delete/destroy/free a
* non-null value of Type*.
*
* Example:
*
* MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLATE(ScopedPRFileDesc, PRFileDesc, \
* PR_Close)
* ...
* {
* ScopedPRFileDesc file(PR_OpenFile(...));
* ...
* } // file is closed with PR_Close here
*/
#define MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLATE(name, Type, Deleter) \
template <> \
inline void TypeSpecificDelete(Type* aValue) { \
Deleter(aValue); \
} \
typedef ::mozilla::TypeSpecificScopedPointer<Type> name;
template <typename T>
void TypeSpecificDelete(T* aValue);
template <typename T>
struct TypeSpecificScopedPointerTraits {
typedef T* type;
static type empty() { return nullptr; }
static void release(type aValue) {
if (aValue) {
TypeSpecificDelete(aValue);
}
}
};
SCOPED_TEMPLATE(TypeSpecificScopedPointer, TypeSpecificScopedPointerTraits)
} /* namespace mozilla */
#endif /* mozilla_Scoped_h */
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