xref: /titanic_41/usr/src/cmd/lms/SyncLib/Include/SPtr.h (revision 617e2443dfc17fe44fd44c0675d6aad2ffc9df42)

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//////////////////////////////////////////////////////////////////////////
//  SPtr.h
//
//  This is a smart pointer class. It receives an initialized object in
//  the constructor, and maintains a reference count to this object. It
//  deletes the object only when the reference count reaches 0.
//
//////////////////////////////////////////////////////////////////////////

#ifndef _SPTR_H_
#define _SPTR_H_

#include <memory>
#include "Semaphore.h"

template
<class T>
class SPtr
{
public:
	// constructor
	explicit SPtr(T *ptr_p = 0) :
		_ptr(ptr_p),
		_pref_count(new int(1)),
		_psem(new Semaphore(1)) {}

	// copy constructor
	template<class X>
	SPtr(const SPtr<X> &other_sptr_p)
	{
		other_sptr_p.getSem()->acquire();
		_ptr = other_sptr_p.get();
		_pref_count = other_sptr_p.getRefcnt();
		_psem = other_sptr_p.getSem();
		++(*_pref_count);
		_psem->release();
	}

	SPtr(const SPtr &other_sptr_p)
	{
		other_sptr_p.getSem()->acquire();
		_ptr = other_sptr_p.get();
		_pref_count = other_sptr_p.getRefcnt();
		_psem = other_sptr_p.getSem();
		++(*_pref_count);
		_psem->release();
	}

	// destructor
	~SPtr()
	{
		_psem->acquire();
		if (--(*_pref_count) == 0) {
			// delete pointer only on last destruction
			delete _pref_count;
			delete _psem;
			if (_ptr) {
				delete _ptr;
			}
			_ptr = 0;
		} else {
			_psem->release();
		}
	}

	// operator=
	// if 'this' already points to an object, unreference it
	template<class X>
	SPtr &operator= (const SPtr<X> &other_sptr_p)
	{
		if ((void *)&other_sptr_p == this) {
			return *this;
		}
		_psem->acquire();
		if (--(*_pref_count) == 0) {
			delete _pref_count;
			delete _psem;
			if (_ptr) {
				delete _ptr;
			}
		} else {
			_psem->release();
		}
		other_sptr_p.getSem()->acquire();
		_ptr = (T *)other_sptr_p.get();
		_pref_count = other_sptr_p.getRefcnt();
		_psem = other_sptr_p.getSem();
		++(*_pref_count);
		_psem->release();
		return *this;
	}

	SPtr &operator=(const SPtr &other_sptr_p)
	{
		if (&other_sptr_p == this) {
			return *this;
		}
		_psem->acquire();
		if (--(*_pref_count) == 0) {
			delete _pref_count;
			delete _psem;
			if (_ptr) {
				delete _ptr;
			}
		} else {
			_psem->release();
		}
		other_sptr_p.getSem()->acquire();
		_ptr = other_sptr_p.get();
		_pref_count = other_sptr_p.getRefcnt();
		_psem = other_sptr_p.getSem();
		++(*_pref_count);
		_psem->release();
		return *this;
	}

	// operator*
	T &operator*() const
	{
		return *_ptr;
	}

	// operator->
	T *operator->() const
	{
		return _ptr;
	}

	// get - return inner pointer
	T *get() const
	{
		return _ptr;
	}

	int *getRefcnt() const
	{
		return _pref_count;
	}

	Semaphore *getSem() const
	{
		return _psem;
	}

private:
	// the pointer itself
	T *_ptr;
	// a pointer to the reference count
	int *_pref_count;
	Semaphore *_psem;
} ;

template
<class T>
inline bool operator==(const SPtr<T> &x, const SPtr<T> &y) {
	return(x.get() == y.get());
}

template
<class T>
inline bool operator!=(const SPtr<T> &x, const SPtr<T> &y) {
	return(x.get() != y.get());
}

#endif // _SPTR_H_