readorwritelocker.h

   1 /*
   2   readorwritelocker.h
   3
   4   This file is part of GammaRay, the Qt application inspection and
   5   manipulation tool.
   6
   7   Copyright (C) 2010-2011 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com
   8   Author: Milian Wolff <milian.wolff@kdab.com>
   9
  10   This program is free software; you can redistribute it and/or modify
  11   it under the terms of the GNU General Public License as published by
  12   the Free Software Foundation, either version 2 of the License, or
  13   (at your option) any later version.
  14
  15   This program is distributed in the hope that it will be useful,
  16   but WITHOUT ANY WARRANTY; without even the implied warranty of
  17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18   GNU General Public License for more details.
  19
  20   You should have received a copy of the GNU General Public License
  21   along with this program.  If not, see <http://www.gnu.org/licenses/>.
  22 */
  23
  24 #ifndef GAMMARAY_READORWRITELOCKER_H
  25 #define GAMMARAY_READORWRITELOCKER_H
  26
  27 #include <QReadWriteLock>
  28
  29 namespace GammaRay {
  30
  31 /**
  32  * Lock that can/should be used instead of QReadLocker
  33  * when we want to read or write lock and can have
  34  * nested functions that first writelock and then readlock.
  35  *
  36  * Esp. required for the threadsafe models.
  37  */
  38 class ReadOrWriteLocker
  39 {
  40   public:
  41     ReadOrWriteLocker(QReadWriteLock *lock)
  42       : m_lock(lock),
  43         m_locked(false)
  44     {
  45       this->lock();
  46     }
  47
  48     void lock()
  49     {
  50       if (!m_lock->tryLockForWrite()) {
  51         m_lock->lockForRead();
  52       }
  53       m_locked = true;
  54     }
  55
  56     void unlock()
  57     {
  58       m_lock->unlock();
  59       m_locked = false;
  60     }
  61
  62     ~ReadOrWriteLocker()
  63     {
  64       if (m_locked) {
  65         unlock();
  66       }
  67     }
  68
  69   private:
  70     QReadWriteLock *m_lock;
  71     bool m_locked;
  72 };
  73
  74 }
  75
  76 #endif // GAMMARAY_READORWRITELOCKER_H