/usr/include/cxxtools/smartptr.h is in libcxxtools-dev 2.0-4ubuntu2.
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* Copyright (C) 2005 Tommi Maekitalo
*
* This library 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.
*
* As a special exception, you may use this file as part of a free
* software library without restriction. Specifically, if other files
* instantiate templates or use macros or inline functions from this
* file, or you compile this file and link it with other files to
* produce an executable, this file does not by itself cause the
* resulting executable to be covered by the GNU General Public
* License. This exception does not however invalidate any other
* reasons why the executable file might be covered by the GNU Library
* General Public License.
*
* 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 CXXTOOLS_SMARTPTR_H
#define CXXTOOLS_SMARTPTR_H
#include <cxxtools/atomicity.h>
namespace cxxtools
{
template <typename objectType>
class RefLinked
{
mutable const RefLinked* prev;
mutable const RefLinked* next;
protected:
RefLinked()
: prev(0),
next(0)
{ }
bool unlink(objectType* object)
{
bool ret = false;
if (object)
{
if (next == this)
{
ret = true;
}
else
{
next->prev = prev;
prev->next = next;
}
next = prev = this;
}
return ret;
}
void link(const RefLinked& ptr, objectType* object)
{
if (object)
{
prev = &ptr;
next = ptr.next;
prev->next = this;
next->prev = this;
}
}
};
template <typename objectType>
class InternalRefCounted
{
protected:
bool unlink(objectType* object)
{
if (object)
object->release();
return false;
}
void link(const InternalRefCounted& ptr, objectType* object)
{
if (object)
object->addRef();
}
};
template <typename objectType>
class ExternalRefCounted
{
unsigned* rc;
protected:
ExternalRefCounted()
: rc(0) { }
bool unlink(objectType* object)
{
if (object && --*rc <= 0)
{
delete rc;
// no need to set rc to 0 since the pointer is either
// destroyed or another object is linked in
return true;
}
else
return false;
}
void link(const ExternalRefCounted& ptr, objectType* object)
{
if (object)
{
if (ptr.rc == 0)
rc = new unsigned(1);
else
{
rc = ptr.rc;
++*rc;
}
}
else
rc = 0;
}
public:
unsigned refs() const
{ return rc ? *rc : 0; }
};
template <typename objectType>
class ExternalAtomicRefCounted
{
volatile atomic_t* rc;
protected:
ExternalAtomicRefCounted()
: rc(0) { }
bool unlink(objectType* object)
{
if (object && atomicDecrement(*rc) <= 0)
{
delete rc;
// no need to set rc to 0 since the pointer is either
// destroyed or another object is linked in
return true;
}
else
return false;
}
void link(const ExternalAtomicRefCounted& ptr, objectType* object)
{
if (object)
{
if (ptr.rc == 0)
rc = new atomic_t(1);
else
{
rc = ptr.rc;
atomicIncrement(*rc);
}
}
else
rc = 0;
}
public:
atomic_t refs() const
{ return rc ? *rc : 0; }
};
template <typename objectType>
class DefaultDestroyPolicy
{
public:
static void destroy(objectType* ptr)
{ delete ptr; }
};
template <typename T>
class FreeDestroyPolicy
{
protected:
void destroy(T* ptr)
{ free(ptr); }
};
template <typename objectType>
class ArrayDestroyPolicy
{
public:
static void destroy(objectType* ptr)
{ delete[] ptr; }
};
/**
* Policy-based smart-pointer-class.
*
* This class works like a pointer, but the destructor deletes the held
* object if this is the last reference. The policy specifies, how the class
* counts the references. There are 4 policies:
*
* ExternalRefCounted: allocates a reference-count
*
* ExternalAtomicRefCounted: like ExternalRefCounted, but thread safe
*
* InternalRefCounted: the pointed object needs to have a reference-counter
* with methods addRef() and release(). The release-method deletes the
* object, when the reference-count drops to 0.
*
* RefLinked: all pointers to a object are linked
*
* The default policy is InternalRefCounted. Another class
* cxxtools::RefCounted implements proper methods for the pointer, which
* makes it straight-forward to use.
*
*/
template <typename objectType,
template <class> class ownershipPolicy = InternalRefCounted,
template <class> class destroyPolicy = DefaultDestroyPolicy>
class SmartPtr : public ownershipPolicy<objectType>,
public destroyPolicy<objectType>
{
objectType* object;
typedef ownershipPolicy<objectType> ownershipPolicyType;
typedef destroyPolicy<objectType> destroyPolicyType;
public:
SmartPtr()
: object(0)
{}
SmartPtr(objectType* ptr)
: object(ptr)
{ ownershipPolicyType::link(*this, ptr); }
SmartPtr(const SmartPtr& ptr)
: object(ptr.object)
{ ownershipPolicyType::link(ptr, ptr.object); }
~SmartPtr()
{ if (ownershipPolicyType::unlink(object))
destroy(object); }
SmartPtr& operator= (const SmartPtr& ptr)
{
if (object != ptr.object)
{
if (ownershipPolicyType::unlink(object))
destroy(object);
object = ptr.object;
ownershipPolicyType::link(ptr, object);
}
return *this;
}
/// The object can be dereferenced like the held object
objectType* operator->() const { return object; }
/// The object can be dereferenced like the held object
objectType& operator*() const { return *object; }
bool operator== (const objectType* p) const { return object == p; }
bool operator!= (const objectType* p) const { return object != p; }
bool operator< (const objectType* p) const { return object < p; }
bool operator! () const { return object == 0; }
operator bool () const { return object != 0; }
objectType* getPointer() { return object; }
const objectType* getPointer() const { return object; }
operator objectType* () { return object; }
operator const objectType* () const { return object; }
};
}
#endif // CXXTOOLS_SMARTPTR_H
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