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ptr.h
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ptr.h
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/* ScummVM - Graphic Adventure Engine
*
* ScummVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the COPYRIGHT
* file distributed with this source distribution.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
*/
#ifndef COMMON_PTR_H
#define COMMON_PTR_H
#include "common/scummsys.h"
#include "common/noncopyable.h"
#include "common/safe-bool.h"
#include "common/types.h"
namespace Common {
/**
* @defgroup common_ptr Pointers
* @ingroup common
*
* @brief API and templates for pointers.
* @{
*/
class BasePtrDeletionInternal {
public:
virtual ~BasePtrDeletionInternal() {}
};
template<class T>
class BasePtrDeletionImpl : public BasePtrDeletionInternal {
public:
BasePtrDeletionImpl(T *ptr) : _ptr(ptr) {}
~BasePtrDeletionImpl() {
STATIC_ASSERT(sizeof(T) > 0, SharedPtr_cannot_delete_incomplete_type);
delete _ptr;
}
private:
T *_ptr;
};
template<class T, class DL>
class BasePtrDeletionDeleterImpl : public BasePtrDeletionInternal {
public:
BasePtrDeletionDeleterImpl(T *ptr, DL d) : _ptr(ptr), _deleter(d) {}
~BasePtrDeletionDeleterImpl() { _deleter(_ptr); }
private:
T *_ptr;
DL _deleter;
};
/**
* A base class for both SharedPtr and WeakPtr.
*
* This base class encapsulates the logic for the reference counter
* used by both.
*/
template<class T>
class BasePtr : public SafeBool<BasePtr<T> > {
#if !defined(__GNUC__) || GCC_ATLEAST(3, 0)
template<class T2> friend class BasePtr;
#endif
public:
typedef int RefValue;
typedef T ValueType;
typedef T *PointerType;
typedef T &ReferenceType;
BasePtr() : _refCount(nullptr), _deletion(nullptr), _pointer(nullptr) {
}
explicit BasePtr(nullptr_t) : _refCount(nullptr), _deletion(nullptr), _pointer(nullptr) {
}
template<class T2>
explicit BasePtr(T2 *p) : _refCount(new RefValue(1)), _deletion(new BasePtrDeletionImpl<T2>(p)), _pointer(p) {
}
template<class T2, class DL>
BasePtr(T2 *p, DL d) : _refCount(new RefValue(1)), _deletion(new BasePtrDeletionDeleterImpl<T2, DL>(p, d)), _pointer(p) {
}
BasePtr(const BasePtr &r) : _refCount(r._refCount), _deletion(r._deletion), _pointer(r._pointer) {
if (_refCount)
++(*_refCount);
}
template<class T2>
BasePtr(const BasePtr<T2> &r) : _refCount(r._refCount), _deletion(r._deletion), _pointer(r._pointer) {
if (_refCount) ++(*_refCount);
}
~BasePtr() {
decRef();
}
/**
* Implicit conversion operator to bool for convenience, to make
* checks like "if (sharedPtr) ..." possible.
*/
bool operator_bool() const {
return _pointer != nullptr;
}
/**
* Returns the number of references to the assigned pointer.
* This should just be used for debugging purposes.
*/
RefValue refCount() const {
return _refCount ? *_refCount : 0;
}
/**
* Returns whether the referenced object isn't valid
*/
bool expired() const {
return !_refCount;
}
/**
* Checks if the object is the only object refering
* to the assigned pointer. This should just be used for
* debugging purposes.
*/
bool unique() const {
return refCount() == 1;
}
BasePtr &operator=(const BasePtr &r) {
reset(r);
return *this;
}
template<class T2>
BasePtr &operator=(const BasePtr<T2> &r) {
reset(r);
return *this;
}
/**
* Resets the object to a NULL pointer.
*/
void reset() {
decRef();
_deletion = nullptr;
_refCount = nullptr;
_pointer = nullptr;
}
/**
* Resets the object to the specified pointer
*/
void reset(const BasePtr &r) {
if (r._refCount)
++(*r._refCount);
decRef();
_refCount = r._refCount;
_deletion = r._deletion;
_pointer = r._pointer;
}
/**
* Resets the object to the specified pointer
*/
template<class T2>
void reset(const BasePtr<T2> &r) {
if (r._refCount)
++(*r._refCount);
decRef();
_refCount = r._refCount;
_deletion = r._deletion;
_pointer = r._pointer;
}
/**
* Resets the object to the specified pointer
*/
void reset(T *ptr) {
reset(BasePtr<T>(ptr));
}
protected:
RefValue *_refCount;
BasePtrDeletionInternal *_deletion;
PointerType _pointer;
protected:
/**
* Decrements the reference count to the stored pointer, and deletes it if
* there are no longer any references to it
*/
void decRef() {
if (_refCount) {
--(*_refCount);
if (!*_refCount) {
delete _refCount;
delete _deletion;
_deletion = nullptr;
_refCount = nullptr;
_pointer = nullptr;
}
}
}
/**
* Increments the reference count to the stored pointer
*/
void incRef() {
if (_refCount)
++*_refCount;
}
};
template<class T>
class WeakPtr;
/**
* A simple shared pointer implementation modelled after boost.
*
* This object keeps track of the assigned pointer and automatically
* frees it when no more SharedPtr references to it exist.
*
* To achieve that the object implements an internal reference counting.
* Thus you should try to avoid using the plain pointer after assigning
* it to a SharedPtr object for the first time. If you still use the
* plain pointer be sure you do not delete it on your own. You may also
* not use the plain pointer to create a new SharedPtr object, since that
* would result in a double deletion of the pointer sooner or later.
*
* Example creation:
* Common::SharedPtr<int> pointer(new int(1));
* would create a pointer to int. Later on usage via *pointer is the same
* as for a normal pointer. If you need to access the plain pointer value
* itself later on use the get method. The class also supplies a operator
* ->, which does the same as the -> operator on a normal pointer.
*
* Be sure you are using new to initialize the pointer you want to manage.
* If you do not use new for allocating, you have to supply a deleter as
* second parameter when creating a SharedPtr object. The deleter has to
* implement operator() which takes the pointer it should free as argument.
*
* Note that you have to specify the type itself not the pointer type as
* template parameter.
*
* When creating a SharedPtr object from a normal pointer you need a real
* definition of the type you want SharedPtr to manage, a simple forward
* definition is not enough.
*
* The class has implicit upcast support, so if you got a class B derived
* from class A, you can assign a pointer to B without any problems to a
* SharedPtr object with template parameter A. The very same applies to
* assignment of a SharedPtr<B> object to a SharedPtr<A> object.
*
* There are also operators != and == to compare two SharedPtr objects
* with compatible pointers. Comparison between a SharedPtr object and
* a plain pointer is only possible via SharedPtr::get.
*/
template<class T>
class SharedPtr : public BasePtr<T> {
public:
using ReferenceType = typename BasePtr<T>::ReferenceType;
using PointerType = typename BasePtr<T>::PointerType;
SharedPtr() : BasePtr<T>() {
}
SharedPtr(nullptr_t) : BasePtr<T>() {
}
template<class T2>
explicit SharedPtr(T2 *p) : BasePtr<T>(p) {
}
template<class T2, class DL>
SharedPtr(T2 *p, DL d) : BasePtr<T>(p, d) {
}
SharedPtr(const SharedPtr<T> &r) : BasePtr<T>(r) {
}
SharedPtr(const WeakPtr<T> &r) : BasePtr<T>(r) {
}
template<class T2>
SharedPtr(const SharedPtr<T2> &r) : BasePtr<T>(r) {
}
T &operator*() const { assert(this->_pointer); return *this->_pointer; }
T *operator->() const { assert(this->_pointer); return this->_pointer; }
/**
* Returns the plain pointer value. Be sure you know what you
* do if you are continuing to use that pointer.
*
* @return the pointer the SharedPtr object manages
*/
PointerType get() const { return this->_pointer; }
template<class T2>
bool operator==(const SharedPtr<T2> &r) const {
return this->_pointer == r.get();
}
template<class T2>
bool operator!=(const SharedPtr<T2> &r) const {
return this->_pointer != r.get();
}
};
/**
* Implements a smart pointer that holds a non-owning ("weak") refrence to
* a pointer. It needs to be converted to a SharedPtr to access it.
*/
template<class T>
class WeakPtr : public BasePtr<T> {
public:
WeakPtr() : BasePtr<T>() {
}
WeakPtr(nullptr_t) : BasePtr<T>() {
}
template<class T2>
explicit WeakPtr(T2 *p) : BasePtr<T>(p) {
}
WeakPtr(const BasePtr<T> &r) : BasePtr<T>(r) {
}
template<class T2>
WeakPtr(const BasePtr<T2> &r) : BasePtr<T>(r) {
}
/**
* Creates a SharedPtr that manages the referenced object
*/
SharedPtr<T> lock() const {
return SharedPtr<T>(*this);
}
};
template <typename T>
struct DefaultDeleter {
inline void operator()(T *object) {
STATIC_ASSERT(sizeof(T) > 0, cannot_delete_incomplete_type);
delete object;
}
};
template<typename T, class DL = DefaultDeleter<T> >
class ScopedPtr : private NonCopyable, public SafeBool<ScopedPtr<T, DL> > {
public:
typedef T ValueType;
typedef T *PointerType;
typedef T &ReferenceType;
explicit ScopedPtr(PointerType o = nullptr) : _pointer(o) {}
ReferenceType operator*() const { return *_pointer; }
PointerType operator->() const { return _pointer; }
/**
* Implicit conversion operator to bool for convenience, to make
* checks like "if (scopedPtr) ..." possible.
*/
bool operator_bool() const { return _pointer != nullptr; }
~ScopedPtr() {
DL()(_pointer);
}
/**
* Resets the pointer with the new value. Old object will be destroyed
*/
void reset(PointerType o = nullptr) {
DL()(_pointer);
_pointer = o;
}
/**
* Returns the plain pointer value.
*
* @return the pointer the ScopedPtr manages
*/
PointerType get() const { return _pointer; }
/**
* Returns the plain pointer value and releases ScopedPtr.
* After release() call you need to delete object yourself
*
* @return the pointer the ScopedPtr manages
*/
PointerType release() {
PointerType r = _pointer;
_pointer = nullptr;
return r;
}
private:
PointerType _pointer;
};
template<typename T, class DL = DefaultDeleter<T> >
class DisposablePtr : private NonCopyable, public SafeBool<DisposablePtr<T, DL> > {
public:
typedef T ValueType;
typedef T *PointerType;
typedef T &ReferenceType;
explicit DisposablePtr(PointerType o, DisposeAfterUse::Flag dispose) : _pointer(o), _dispose(dispose) {}
~DisposablePtr() {
if (_dispose) DL()(_pointer);
}
ReferenceType operator*() const { return *_pointer; }
PointerType operator->() const { return _pointer; }
/**
* Implicit conversion operator to bool for convenience, to make
* checks like "if (scopedPtr) ..." possible.
*/
bool operator_bool() const { return _pointer != nullptr; }
/**
* Resets the pointer with the new value. Old object will be destroyed
*/
void reset(PointerType o, DisposeAfterUse::Flag dispose) {
if (_dispose) DL()(_pointer);
_pointer = o;
_dispose = dispose;
}
/**
* Clears the pointer. Old object will be destroyed
*/
void reset() {
reset(nullptr, DisposeAfterUse::NO);
}
/**
* Returns the plain pointer value.
*
* @return the pointer the DisposablePtr manages
*/
PointerType get() const { return _pointer; }
private:
PointerType _pointer;
DisposeAfterUse::Flag _dispose;
};
/** @} */
} // End of namespace Common
#endif