Line data    Source code

       1             : /*
       2             :  *  Copyright (C) 2004-2025 Savoir-faire Linux Inc.
       3             :  *
       4             :  *  This program is free software: you can redistribute it and/or modify
       5             :  *  it under the terms of the GNU General Public License as published by
       6             :  *  the Free Software Foundation, either version 3 of the License, or
       7             :  *  (at your option) any later version.
       8             :  *
       9             :  *  This program is distributed in the hope that it will be useful,
      10             :  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
      11             :  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
      12             :  *  GNU General Public License for more details.
      13             :  *
      14             :  *  You should have received a copy of the GNU General Public License
      15             :  *  along with this program. If not, see <https://www.gnu.org/licenses/>.
      16             :  */
      17             : 
      18             : #pragma once
      19             : 
      20             : #include <memory>
      21             : #include <mutex>
      22             : 
      23             : namespace jami {
      24             : 
      25             : /**
      26             :  * Return a shared pointer on an auto-generated global instance of class T.
      27             :  * This instance is created only at usage and destroyed when not,
      28             :  * as we keep only a weak reference on it.
      29             :  * But when created it's always the same object until all holders release
      30             :  * their sharing.
      31             :  * An optional MaxRespawn positive integer can be given to limit the number
      32             :  * of time the object can be created (i.e. different instance).
      33             :  * Any negative values (default) block this effect (unlimited respawn).
      34             :  * This function is thread-safe.
      35             :  */
      36             : template<class T, signed MaxRespawn = -1>
      37             : std::shared_ptr<T>
      38         857 : getGlobalInstance()
      39             : {
      40             :     static std::recursive_mutex mutex; // recursive as instance calls recursively
      41         857 :     static std::weak_ptr<T> wlink;
      42             : 
      43         857 :     std::unique_lock lock(mutex);
      44             : 
      45         857 :     if (wlink.expired()) {
      46             :         static signed counter {MaxRespawn};
      47         269 :         if (not counter)
      48           0 :             return nullptr;
      49         269 :         auto link = std::make_shared<T>();
      50         269 :         wlink = link;
      51         269 :         if (counter > 0)
      52           0 :             --counter;
      53         269 :         return link;
      54         269 :     }
      55             : 
      56         588 :     return wlink.lock();
      57         857 : }
      58             : 
      59             : } // namespace jami