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/***************************************************************************
* Copyright (C) 2005-2019 by the FIFE team *
* http://www.fifengine.net *
* This file is part of FIFE. *
* *
* FIFE is free software; you can redistribute it and/or *
* modify it under the terms of the GNU Lesser General Public *
* License as published by the Free Software Foundation; either *
* version 2.1 of the License, or (at your option) any later version. *
* *
* This library is distributed in the hope that it will be useful, *
* but WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU *
* Lesser General Public License for more details. *
* *
* You should have received a copy of the GNU Lesser General Public *
* License along with this library; if not, write to the *
* Free Software Foundation, Inc., *
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA *
***************************************************************************/
#ifndef FIFE_SHARED_PTR_H_
#define FIFE_SHARED_PTR_H_
// Standard C++ library includes
#include <cassert>
#include <functional>
// 3rd party library includes
// FIFE includes
// These includes are split up in two parts, separated by one empty line
// First block: files included from the FIFE root src directory
// Second block: files included from the same folder
#include "fife_stdint.h"
namespace FIFE {
/** shared pointer implementation to provide automatic
* reference counting and deletion when last reference
* falls out of scope.
*/
template <typename T>
class SharedPtr {
public:
/** Constructor
* default constructor
* creates a null shared pointer
*/
SharedPtr()
: m_ptr(0), m_refCount(0) {
}
/** Constructor
* takes over ownership of the provided pointer
* and will delete it automatically when last
* reference falls out of scope.
*/
template <typename U>
explicit SharedPtr(U *ptr)
: m_ptr(ptr), m_refCount(ptr ? new uint32_t(1) : 0) {
}
/** Copy Constructor
* provides ability to properly copy a shared resource
*/
SharedPtr(const SharedPtr& rhs)
: m_ptr(rhs.m_ptr), m_refCount(rhs.m_refCount) {
// increase reference count
incRefCount();
}
/** Constructor
* shares ownership with the value passed into rhs
* the pointer type passed in must be convertible
* to this shared pointer type
*/
template <typename U>
SharedPtr(const SharedPtr<U>& rhs) {
m_ptr = rhs.get();
m_refCount = rhs.useCountPtr();
incRefCount();
}
/** Destructor
* handles deletion of underlying pointer
* if the reference count reaches 0
*/
~SharedPtr() {
// decrement reference count
decRefCount();
// check to see if we need to delete
if (m_refCount && *m_refCount == 0) {
// delete and set pointers to null
delete m_ptr;
delete m_refCount;
m_ptr = 0;
m_refCount = 0;
}
}
/** provides functionality for the equality operator
*/
SharedPtr& operator=(const SharedPtr& rhs) {
// handle self assignment
if (rhs.get() == m_ptr) {
return *this;
}
// store in temporary (which causes a ref count increase)
// and swap with this object
SharedPtr<T> temp(rhs);
swap(temp);
return *this;
}
/** provides functionality for the equality operator
* the passed in pointer type must be convertible to
* this pointer type
*/
template <typename U>
SharedPtr& operator=(const SharedPtr<U>& rhs) {
// handle self assignment
if (rhs.get() == m_ptr) {
return *this;
}
// store in temporary (which causes a ref count increase)
// and swap with this object
SharedPtr<T> temp(rhs);
swap(temp);
return *this;
}
/** allows dereferencing of shared pointer to act
* identical to dereferencing the underlying pointer
*/
inline T& operator*() const {
assert(m_ptr);
return *m_ptr;
}
/** allows dereferencing of shared pointer to act
* identical to dereferencing the underlying pointer
*/
inline T* operator->() const {
assert(m_ptr);
return m_ptr;
}
/** allows direct access to underlying pointer
*/
inline T* get() const {
return m_ptr;
}
/** reset this pointer to a null shared pointer
* this can be used to lower the reference count
* of the shared resource or set the underlying pointer
* to different pointer.
*/
inline void reset(T* ptr = 0) {
assert(ptr == 0 || ptr != m_ptr);
SharedPtr<T>(ptr).swap(*this);
}
/** returns the current reference count
* this should only be called on a non-null
* shared pointer
*/
inline uint32_t useCount() const {
assert(m_refCount);
if (!m_refCount) {
return 0;
}
return *m_refCount;
}
/** returns the current reference count
* provides direct access to the user count pointer
* this should really only be used internally
*/
inline uint32_t* useCountPtr() const {
return m_refCount;
}
/** provides the ability to see if
* a shared resource is currently only
* held by a single shared pointer
* this should only be called on a non-null
* shared pointer
*/
inline bool unique() const {
assert(m_refCount);
return (*m_refCount == 1);
}
/** provides the ability to convert a
* shared pointer to a bool, this is
* a convenience for checking validity
* of a shared pointer in a conditional
*/
operator bool() const {
return (m_ptr != 0);
}
/** negation operator overload
*/
bool operator!() const {
return (m_ptr == 0);
}
private:
/** provides swapping function between
* two shared pointers, used internally
*/
inline void swap(SharedPtr<T>& rhs) {
std::swap(m_ptr, rhs.m_ptr);
std::swap(m_refCount, rhs.m_refCount);
}
/** increases the reference count for
* this shared resource, used internally
*/
inline void incRefCount() {
if (m_refCount) {
++(*m_refCount);
}
}
/** decreases the reference count for
* this shared resource, used internally
*/
inline void decRefCount() {
if (m_refCount) {
--(*m_refCount);
}
}
private:
T* m_ptr;
uint32_t* m_refCount;
};
/** provides equality operator for shared pointers
*/
template <typename T, typename U>
inline bool operator==(const SharedPtr<T>& lhs, const SharedPtr<U>& rhs) {
return (lhs.get() == rhs.get());
}
/** provides inequality operator for shared pointers
*/
template <typename T, typename U>
inline bool operator!=(const SharedPtr<T>& lhs, const SharedPtr<U>& rhs) {
return (lhs.get() != rhs.get());
}
/** provides less than operator for shared pointers
*/
template<class T, class U>
inline bool operator<(SharedPtr<T> const& lhs, SharedPtr<U> const& rhs) {
return std::less<const void*>()(lhs.get(), rhs.get());
}
/** convenience function for making a shared pointer
* can be used anytime a shared pointer should be created
*/
template <typename T>
SharedPtr<T> make_shared(T* ptr) {
return SharedPtr<T>(ptr);
}
} //FIFE
#endif //FIFE_SHARED_PTR_H_
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