/*
 * Copyright (c) 2003-2008, John Wiegley.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 *
 * - Neither the name of New Artisans LLC nor the names of its
 *   contributors may be used to endorse or promote products derived from
 *   this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * @file   pushvar.h
 * @author John Wiegley
 * @date   Sun May  6 20:10:52 2007
 *
 * @brief  Adds a facility to C++ for handling "scoped yet global".
 */

#ifndef _PUSHVAR_H
#define _PUSHVAR_H

template <typename T>
class push_variable : public boost::noncopyable
{
  push_variable();

public:
  T&   var;
  T    prev;
  bool enabled;

  explicit push_variable(T& _var)
    : var(_var), prev(var), enabled(true) {
    TRACE_CTOR(push_variable, "T&");
  }
  explicit push_variable(T& _var, const T& value)
    : var(_var), prev(var), enabled(true) {
    TRACE_CTOR(push_variable, "T&, constT&");
    var = value;
  }
  ~push_variable() throw() {
    TRACE_DTOR(push_variable);
    if (enabled)
      var = prev;
  }

  T& operator*() {
    return var;
  }
  T * operator->() {
    return &var;
  }

  void clear() {
    enabled = false;
  }
};

#endif // _PUSHVAR_H