LockPtr.h

/*
 *  Lock and LockPtr classes
 *
 *  This file is part of ELM
 *  Copyright (c) 2016, IRIT UPS.
 *
 *  OTAWA is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  OTAWA 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with OTAWA; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#ifndef ELM_UTIL_LOCKPTR_H
#define ELM_UTIL_LOCKPTR_H
 
#include <elm/assert.h>
 
namespace elm {
 
// Lock class
class Lock {
    int u;
public:
    inline Lock(int usage = 0): u(usage) { }
    inline void lock(void) { u++; }
    inline void unlock(void) { u--; }
    inline int usage(void) const { return u; }
};
 
 
// AutoPtr class
template <class T> class LockPtr {
public:
    inline LockPtr(T *p = 0): ptr(p ? p : null_lock()) { ptr->lock(); }
    inline LockPtr(const LockPtr& l): ptr(l.ptr) { ptr->lock(); }
    inline ~LockPtr(void) { unlock(); }
    static LockPtr<T> null;
 
    inline LockPtr& operator=(const LockPtr& lock)
        { unlock(); ptr = lock.ptr; ptr->lock(); return *this;}
    inline LockPtr& operator=(T *p)
        { unlock(); ptr = p ? p : null_lock(); ptr->lock(); return *this; }
 
    inline T *operator->(void) const
        { ASSERTP(!isNull(), "accessing null pointer"); return (T *)ptr; }
    inline T& operator*(void) const
        { ASSERTP(!isNull(), "accessing null pointer"); return *(T *)ptr; }
    inline T *operator&(void) const
        { return isNull() ? 0 : (T *)ptr; }
 
    inline bool isNull(void) const
        { return ptr == null_lock(); }
    inline operator bool(void) const { return !isNull(); };
 
    inline bool operator==(const LockPtr<T>& ap) const
        { return ptr == ap.ptr; }
    inline bool operator!=(const LockPtr<T>& ap) const
        { return ptr != ap.ptr; }
    inline bool operator>(const LockPtr<T>& ap) const
        { return ptr > ap.ptr; }
    inline bool operator>=(const LockPtr<T>& ap) const
        { return ptr >= ap.ptr; }
    inline bool operator<(const LockPtr<T>& ap) const
        { return ptr < ap.ptr; }
    inline bool operator<=(const LockPtr<T>& ap) const
        { return ptr <= ap.ptr; }
 
private:
    void unlock(void) { ptr->unlock(); if(!ptr->usage()) { delete ptr; ptr = null_lock(); } }
    T *ptr;
    static T *null_lock(void) { static Lock n(1); return (T *)&n; }
};
 
}   // elm
 
#endif // ELM_UTIL_AUTOPTR_H