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/*
* Copyright (c) 2013, Ford Motor Company
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following
* disclaimer in the documentation and/or other materials provided with the
* distribution.
*
* Neither the name of the Ford Motor Company nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef SRC_COMPONENTS_UTILS_INCLUDE_UTILS_SINGLETON_H_
#define SRC_COMPONENTS_UTILS_INCLUDE_UTILS_SINGLETON_H_
#include "utils/lock.h"
#include "utils/memory_barrier.h"
#include "utils/atomic.h"
namespace utils {
namespace deleters {
class DummyDeleter {
public:
void grab(void* pointer) {
}
};
template<typename T>
class Deleter {
public:
Deleter() : pointer_(0) {
}
~Deleter() {
if (pointer_) {
delete pointer_;
}
}
void grab(T* pointer) {
pointer_ = pointer;
}
private:
T* pointer_;
};
} // namespace deleters
template<typename T, class Deleter = deleters::DummyDeleter>
class Singleton {
/**
* @brief Singleton template
* Singleton classes must derive from this template specialized with class itself:
*
* class MySingleton : public Singleton<MySingleton> {...};
*
* All such classes must declare instance() method as friend
* by adding FRIEND_BASE_SINGLETON_CLASS macro from macro.h to class definition:
*
* FRIEND_BASE_SINGLETON_CLASS(MySingleton);
*
* Instance of this class (if created) can be deleted by Deleter destructor
* which is called after main() (or from exit())
* This requires T destructor to be accessible for Deleter (e.g. public)
* Deleter template parameter can be specified with any class
* with public default constructor, destructor and method
* void grab(T*);
* However, default Deleter specification does nothing
*
* Also instance can be deleted explicitly by calling destroy() method
*
* Both instance() and destroy() methods are thread safe
* but not thread safety between simultaneous calls
* of instance() and destroy() is cared about
*/
public:
/**
* @brief Returns the singleton of class
*/
static T* instance();
/**
* @brief Destroys the singleton (if it had been created)
*/
static void destroy();
/**
* @brief Checks whether the singleton exists
*/
static bool exists();
private:
static T** instance_pointer();
static Deleter* deleter();
};
template<typename T, class Deleter>
T* Singleton<T, Deleter>::instance() {
static sync_primitives::Lock lock;
T* local_instance;
atomic_pointer_assign(local_instance, *instance_pointer());
memory_barrier();
if (!local_instance) {
lock.Acquire();
local_instance = *instance_pointer();
if (!local_instance) {
local_instance = new T();
memory_barrier();
atomic_pointer_assign(*instance_pointer(), local_instance);
deleter()->grab(local_instance);
}
lock.Release();
}
return local_instance;
}
template<typename T, class Deleter>
void Singleton<T, Deleter>::destroy() {
static sync_primitives::Lock lock;
T* local_instance;
atomic_pointer_assign(local_instance, *instance_pointer());
memory_barrier();
if (local_instance) {
lock.Acquire();
local_instance = *instance_pointer();
if (local_instance) {
atomic_pointer_assign(*instance_pointer(), 0);
memory_barrier();
delete local_instance;
deleter()->grab(0);
}
lock.Release();
}
}
template<typename T, class Deleter>
bool Singleton<T, Deleter>::exists() {
return *instance_pointer() != 0;
}
template<typename T, class Deleter>
T** Singleton<T, Deleter>::instance_pointer() {
static T* instance = 0;
return &instance;
}
template<typename T, class Deleter>
Deleter* Singleton<T, Deleter>::deleter() {
static Deleter deleter;
return &deleter;
}
} // namespace utils
#endif // SRC_COMPONENTS_UTILS_INCLUDE_UTILS_SINGLETON_H_
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