File: pushvalue.h

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/*
   Copyright 2007-2008 David Nolden <david.nolden.kdevelop@art-master.de>

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public
   License version 2 as published by the Free Software Foundation.

   This library 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public License
   along with this library; see the file COPYING.LIB.  If not, write to
   the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
   Boston, MA 02110-1301, USA.
*/

#ifndef PUSHVALUE_H
#define PUSHVALUE_H

/**
 * A simple helper-class that does the following:
 * Backup the given reference-value given through @param ptr,
 * replace it with the value given through @param push,
 * restore the backed up value back on destruction.
 * */
template<class Value>
class PushValue {
  public:
    PushValue( Value& ptr, const Value& push = Value()  ) : m_ptr(ptr)  {
      m_oldPtr = m_ptr;
      m_ptr = push;
    }
    ~PushValue() {
      m_ptr = m_oldPtr;
    }
  private:
    Value& m_ptr;
    Value m_oldPtr;
};

///Only difference to PushValue: The value is only replaced if the new value is positive
template<class Value>
class PushPositiveValue {
  public:
    PushPositiveValue( Value& ptr, const Value& push = Value()  ) : m_ptr(ptr)  {
      m_oldPtr = m_ptr;
      if( push ) {
        m_ptr = push;
      }
    }
    ~PushPositiveValue() {
      m_ptr = m_oldPtr;
    }
  private:
    Value& m_ptr;
    Value m_oldPtr;
};

#endif