p44obj.cpp

//  SPDX-License-Identifier: GPL-3.0-or-later
//
//  Copyright (c) 2013-2023 plan44.ch / Lukas Zeller, Zurich, Switzerland
//
//  Author: Lukas Zeller <luz@plan44.ch>
//
//  This file is part of p44utils.
//
//  p44utils 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 3 of the License, or
//  (at your option) any later version.
//
//  p44utils 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 p44utils. If not, see <http://www.gnu.org/licenses/>.
//

#include "p44obj.hpp"


using namespace p44;

namespace p44 {

  void intrusive_ptr_add_ref(P44Obj* o)
  {
    ++(o->refCount);
  }

  void intrusive_ptr_release(P44Obj* o)
  {
    if(--(o->refCount) == 0) {
      // Setting the refCount to an arbitrary not small negative number
      // gives us some protection (at no performance penalty for normal ref+/- operations)
      // against destructors that cause reference count to increase again (e.g. by callbacks
      // that reference the object) and would otherwise cause a double delete once the
      // refcount re-reaches zero.
      // Only after 4242 extra references added to the object DURING DESTRUCTION, this
      // would not hold any more...
      o->refCount = -4242;
      // now delete, ONCE
      delete o;
    }
  }

  void P44Obj::isMemberVariable()
  {
    // set refcount high to avoid deletion via intrusive_ptr_release
    // the only way the object can get deleted is along with the object it is a member variable of.
    refCount = 4242;
  }

}