ircproxy  The Ultimate Cyborg

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Counter.h

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// ircproxy -- An IRC bouncer.
//
//! @file Counter.h
//! @brief This file contains the declaration of class Counter.
//
// Copyright (C) 2007 by
//
// Carlo Wood, Run on IRC <carlo@alinoe.com>
// RSA-1024 0x624ACAD5 1997-01-26                    Sign & Encrypt
// Fingerprint16 = 32 EC A7 B6 AC DB 65 A6  F6 F6 55 DD 1C DC FF 61
//
// This file may be distributed under the terms of the Q Public License
// version 1.0 as appearing in the file LICENSE.QPL included in the
// packaging of this file.

#ifndef COUNTER_H
#define COUNTER_H

#include <boost/noncopyable.hpp>
#include "debug.h"

class Increment;

/*! @brief A counter with scope-safe increment/decrement.
 *
 * Use this class like:
 *
 * Counter counter;
 *
 * if (counter == 0)
 *
 * To increment the counter, create an Increment object in a scope:
 *
 * Increment increment(counter);
 *
 * When increment is destructed, the counter will automatically be decremented again.
 */
class Counter : public boost::noncopyable {
  private:
    friend class Increment;     //!< Has direct access to M_counter.
    int M_counter;              //!< Non-zero when locked.
  public:
    //! Constructor.
    Counter(void) : M_counter(0) { }
    //! Destructor.
    ~Counter() { ASSERT(M_counter == 0); }

    //! Automatic conversion to int.
    operator int() const { return M_counter; }
};

/*! @brief Helper object for class Counter.
 *
 * This class increments/decrements a Counter object.
 */
class Increment : public boost::noncopyable {
  private:
    Counter& M_counter;         //!< A reference to the underlying counter.
  public:
    //! Constructor; increment reference counter \a counter.
    Increment(Counter& counter) : M_counter(counter) { ++M_counter.M_counter; }
    //! Destructor: decrement reference counter.
    ~Increment() { --M_counter.M_counter; }
};

#endif // COUNTER_H

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