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/*
* Copyright (c)2019 ZeroTier, Inc.
*
* Use of this software is governed by the Business Source License included
* in the LICENSE.TXT file in the project's root directory.
*
* Change Date: 2025-01-01
*
* On the date above, in accordance with the Business Source License, use
* of this software will be governed by version 2.0 of the Apache License.
*/
/****/
#ifndef ZT_SHAREDPTR_HPP
#define ZT_SHAREDPTR_HPP
#include "Mutex.hpp"
#include "AtomicCounter.hpp"
namespace ZeroTier {
/**
* Simple zero-overhead introspective reference counted pointer
*
* This is an introspective shared pointer. Classes that need to be reference
* counted must list this as a 'friend' and must have a private instance of
* AtomicCounter called __refCount.
*/
template<typename T>
class SharedPtr
{
public:
SharedPtr() : _ptr((T *)0) {}
SharedPtr(T *obj) : _ptr(obj) { ++obj->__refCount; }
SharedPtr(const SharedPtr &sp) : _ptr(sp._getAndInc()) {}
~SharedPtr()
{
if (_ptr) {
if (--_ptr->__refCount <= 0) {
delete _ptr;
}
}
}
inline SharedPtr &operator=(const SharedPtr &sp)
{
if (_ptr != sp._ptr) {
T *p = sp._getAndInc();
if (_ptr) {
if (--_ptr->__refCount <= 0) {
delete _ptr;
}
}
_ptr = p;
}
return *this;
}
/**
* Set to a naked pointer and increment its reference count
*
* This assumes this SharedPtr is NULL and that ptr is not a 'zombie.' No
* checks are performed.
*
* @param ptr Naked pointer to assign
*/
inline void set(T *ptr)
{
zero();
++ptr->__refCount;
_ptr = ptr;
}
/**
* Swap with another pointer 'for free' without ref count overhead
*
* @param with Pointer to swap with
*/
inline void swap(SharedPtr &with)
{
T *tmp = _ptr;
_ptr = with._ptr;
with._ptr = tmp;
}
inline operator bool() const { return (_ptr != (T *)0); }
inline T &operator*() const { return *_ptr; }
inline T *operator->() const { return _ptr; }
/**
* @return Raw pointer to held object
*/
inline T *ptr() const { return _ptr; }
/**
* Set this pointer to NULL
*/
inline void zero()
{
if (_ptr) {
if (--_ptr->__refCount <= 0) {
delete _ptr;
}
_ptr = (T *)0;
}
}
/**
* @return Number of references according to this object's ref count or 0 if NULL
*/
inline int references()
{
if (_ptr) {
return _ptr->__refCount.load();
}
return 0;
}
inline bool operator==(const SharedPtr &sp) const { return (_ptr == sp._ptr); }
inline bool operator!=(const SharedPtr &sp) const { return (_ptr != sp._ptr); }
inline bool operator>(const SharedPtr &sp) const { return (_ptr > sp._ptr); }
inline bool operator<(const SharedPtr &sp) const { return (_ptr < sp._ptr); }
inline bool operator>=(const SharedPtr &sp) const { return (_ptr >= sp._ptr); }
inline bool operator<=(const SharedPtr &sp) const { return (_ptr <= sp._ptr); }
private:
inline T *_getAndInc() const
{
if (_ptr) {
++_ptr->__refCount;
}
return _ptr;
}
T *_ptr;
};
} // namespace ZeroTier
#endif
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