#ifndef RefCounter_h
#define RefCounter_h
#include <wtf/Function.h>
#include <wtf/Noncopyable.h>
#include <wtf/RefPtr.h>
#include <wtf/SetForScope.h>
namespace WTF {
enum class RefCounterEvent { Decrement, Increment };
template<typename T>
class RefCounter {
WTF_MAKE_NONCOPYABLE(RefCounter);
class Count {
WTF_MAKE_NONCOPYABLE(Count);
public:
void ref();
void deref();
void refCounterWasDeleted();
private:
friend class RefCounter;
Count(RefCounter& refCounter)
: m_refCounter(&refCounter)
, m_value(0)
{
}
RefCounter* m_refCounter;
size_t m_value;
bool m_inValueDidChange { false };
};
public:
using Token = RefPtr<Count>;
using ValueChangeFunction = WTF::Function<void (RefCounterEvent)>;
RefCounter(ValueChangeFunction&& = nullptr);
~RefCounter();
Token count() const
{
return m_count;
}
size_t value() const
{
return m_count->m_value;
}
private:
ValueChangeFunction m_valueDidChange;
Count* m_count;
};
template<typename T>
inline void RefCounter<T>::Count::ref()
{
++m_value;
if (m_refCounter && m_refCounter->m_valueDidChange)
m_refCounter->m_valueDidChange(RefCounterEvent::Increment);
}
template<typename T>
inline void RefCounter<T>::Count::deref()
{
ASSERT(m_value);
--m_value;
if (m_refCounter && m_refCounter->m_valueDidChange) {
SetForScope<bool> inCallback(m_inValueDidChange, true);
m_refCounter->m_valueDidChange(RefCounterEvent::Decrement);
}
if (!m_refCounter && !m_value)
delete this;
}
template<typename T>
inline void RefCounter<T>::Count::refCounterWasDeleted()
{
m_refCounter = nullptr;
if (m_inValueDidChange)
return;
if (!m_value)
delete this;
}
template<typename T>
inline RefCounter<T>::RefCounter(ValueChangeFunction&& valueDidChange)
: m_valueDidChange(WTFMove(valueDidChange))
, m_count(new Count(*this))
{
}
template<typename T>
inline RefCounter<T>::~RefCounter()
{
m_count->refCounterWasDeleted();
}
}
using WTF::RefCounter;
using WTF::RefCounterEvent;
#endif // RefCounter_h