ZeroTierOne/node/SharedPtr.hpp
Adam Ierymenko d537428421
Build fixes.
2020-05-18 09:44:23 -07:00

193 lines
4.7 KiB
C++

/*
* Copyright (c)2013-2020 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: 2024-01-01
*
* 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 "Constants.hpp"
#include "TriviallyCopyable.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
* atomic<int> called __refCount.
*/
template<typename T>
class SharedPtr : public TriviallyCopyable
{
public:
ZT_INLINE SharedPtr() noexcept : m_ptr((T *)0) {}
explicit ZT_INLINE SharedPtr(T *obj) noexcept : m_ptr(obj) { ++obj->__refCount; }
ZT_INLINE SharedPtr(const SharedPtr &sp) noexcept : m_ptr(sp._getAndInc()) {}
ZT_INLINE ~SharedPtr()
{
if (m_ptr) {
if (--m_ptr->__refCount <= 0)
delete m_ptr;
}
}
ZT_INLINE SharedPtr &operator=(const SharedPtr &sp)
{
if (m_ptr != sp.m_ptr) {
T *p = sp._getAndInc();
if (m_ptr) {
if (--m_ptr->__refCount <= 0)
delete m_ptr;
}
m_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
*/
ZT_INLINE void set(T *ptr) noexcept
{
zero();
++ptr->__refCount;
m_ptr = ptr;
}
/**
* Stupidly set this SharedPtr to 'ptr', ignoring current value and not incrementing reference counter
*
* This must only be used in code that knows what it's doing. :)
*
* @param ptr Pointer to set
*/
ZT_INLINE void unsafeSet(T *ptr) noexcept { m_ptr = ptr; }
/**
* Swap with another pointer 'for free' without ref count overhead
*
* @param with Pointer to swap with
*/
ZT_INLINE void swap(SharedPtr &with) noexcept
{
T *tmp = m_ptr;
m_ptr = with.m_ptr;
with.m_ptr = tmp;
}
/**
* Set this value to one from another pointer and set that pointer to zero (take ownership from)
*
* This is faster than setting and zeroing the source pointer since it
* avoids a synchronized reference count change.
*
* @param from Origin pointer; will be zeroed
*/
ZT_INLINE void move(SharedPtr &from)
{
if (m_ptr) {
if (--m_ptr->__refCount <= 0)
delete m_ptr;
}
m_ptr = from.m_ptr;
from.m_ptr = nullptr;
}
ZT_INLINE operator bool() const noexcept { return (m_ptr != nullptr); }
ZT_INLINE T &operator*() const noexcept { return *m_ptr; }
ZT_INLINE T *operator->() const noexcept { return m_ptr; }
/**
* @return Raw pointer to held object
*/
ZT_INLINE T *ptr() const noexcept { return m_ptr; }
/**
* Set this pointer to NULL
*/
ZT_INLINE void zero()
{
if (m_ptr) {
if (--m_ptr->__refCount <= 0)
delete m_ptr;
m_ptr = nullptr;
}
}
/**
* Set pointer to NULL and delete object if reference count is only 1
*
* This can be called periodically to implement something like a weak
* reference as it exists in other more managed languages like Java,
* but with the caveat that it only works if there is only one remaining
* SharedPtr to be treated as weak.
*
* @return True if object was in fact deleted or was already zero/NULL
*/
ZT_INLINE bool weakGC()
{
if (m_ptr) {
int one = 1;
if (m_ptr->__refCount.compare_exchange_strong(one,(int)0)) {
delete m_ptr;
m_ptr = nullptr;
return true;
}
return false;
} else {
return true;
}
}
/**
* @return Number of references according to this object's ref count or 0 if NULL
*/
ZT_INLINE int references() noexcept
{
if (m_ptr)
return m_ptr->__refCount;
return 0;
}
ZT_INLINE bool operator==(const SharedPtr &sp) const noexcept { return (m_ptr == sp.m_ptr); }
ZT_INLINE bool operator!=(const SharedPtr &sp) const noexcept { return (m_ptr != sp.m_ptr); }
ZT_INLINE bool operator>(const SharedPtr &sp) const noexcept { return (m_ptr > sp.m_ptr); }
ZT_INLINE bool operator<(const SharedPtr &sp) const noexcept { return (m_ptr < sp.m_ptr); }
ZT_INLINE bool operator>=(const SharedPtr &sp) const noexcept { return (m_ptr >= sp.m_ptr); }
ZT_INLINE bool operator<=(const SharedPtr &sp) const noexcept { return (m_ptr <= sp.m_ptr); }
private:
ZT_INLINE T *_getAndInc() const noexcept
{
if (m_ptr)
++m_ptr->__refCount;
return m_ptr;
}
T *m_ptr;
};
} // namespace ZeroTier
namespace std {
template<typename T>
ZT_INLINE void swap(ZeroTier::SharedPtr<T> &a,ZeroTier::SharedPtr<T> &b) noexcept { a.swap(b); }
}
#endif