Long live Qt 4.5!

1 files changed, 119 insertions, 0 deletions

diff --git a/src/corelib/thread/qorderedmutexlocker_p.h b/src/corelib/thread/qorderedmutexlocker_p.h
new file mode 100644
index 0000000..3b92e31
--- /dev/null
+++ b/src/corelib/thread/qorderedmutexlocker_p.h
@@ -0,0 +1,119 @@
+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** Contact: Qt Software Information (qt-info@nokia.com)
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the either Technology Preview License Agreement or the
+** Beta Release License Agreement.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain
+** additional rights. These rights are described in the Nokia Qt LGPL
+** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this
+** package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+** If you are unsure which license is appropriate for your use, please
+** contact the sales department at qt-sales@nokia.com.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QORDEREDMUTEXLOCKER_P_H
+#define QORDEREDMUTEXLOCKER_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+QT_BEGIN_NAMESPACE
+
+class QMutex;
+
+/*
+  Locks 2 mutexes in a defined order, avoiding a recursive lock if
+  we're trying to lock the same mutex twice.
+*/
+class QOrderedMutexLocker
+{
+public:
+    QOrderedMutexLocker(QMutex *m1, QMutex *m2)
+        : mtx1((m1 == m2) ? m1 : (m1 < m2 ? m1 : m2)),
+          mtx2((m1 == m2) ?  0 : (m1 < m2 ? m2 : m1)),
+          locked(false)
+    {
+        relock();
+    }
+    ~QOrderedMutexLocker()
+    {
+        unlock();
+    }
+
+    void relock()
+    {
+        if (!locked) {
+            if (mtx1) mtx1->lock();
+            if (mtx2) mtx2->lock();
+            locked = true;
+        }
+    }
+
+    void unlock()
+    {
+        if (locked) {
+            if (mtx1) mtx1->unlock();
+            if (mtx2) mtx2->unlock();
+            locked = false;
+        }
+    }
+
+    static bool relock(QMutex *mtx1, QMutex *mtx2)
+    {
+        // mtx1 is already locked, mtx2 not... do we need to unlock and relock?
+        if (mtx1 == mtx2)
+            return false;
+        if (mtx1 < mtx2) {
+            mtx2->lock();
+            return true;
+        }
+        mtx1->unlock();
+        mtx2->lock();
+        mtx1->lock();
+        return true;
+    }
+
+private:
+    QMutex *mtx1, *mtx2;
+    bool locked;
+};
+
+QT_END_NAMESPACE
+
+#endif