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diff --git a/src/statusbar/mountpointobserver.h b/src/statusbar/mountpointobserver.h
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+++ b/src/statusbar/mountpointobserver.h
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+/***************************************************************************
+ *   Copyright (C) 2014 by Frank Reininghaus <[email protected]>    *
+ *                                                                         *
+ *   This program 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 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ *   This program 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 this program; if not, write to the                         *
+ *   Free Software Foundation, Inc.,                                       *
+ *   51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA          *
+ ***************************************************************************/
+
+#ifndef MOUNTPOINTOBSERVER_H
+#define MOUNTPOINTOBSERVER_H
+
+#include <KDiskFreeSpaceInfo>
+
+#include <QObject>
+
+/**
+ * A MountPointObserver can be used to determine the free space on a mount
+ * point. It will then check the free space periodically, and emit the signal
+ * spaceInfoChanged() if the return value of spaceInfo() has changed.
+ *
+ * Since multiple users which watch paths on the same mount point can share
+ * a MountPointObserver, it is not possible to create a MountPointObserver
+ * manually. Instead, the function observerForPath(QString&) should be called,
+ * which returns either an existing or a newly created MountPointObserver for
+ * the mount point where the path is mounted. observerForPath(QString&) looks
+ * for a suitable MountPointObserver in an internal cache and creates new
+ * MountPointObservers and adds them to the cache if necessary.
+ *
+ * Reference counting is used to keep track of the number of users, and to
+ * decide when the object can be deleted. A user of this class should call
+ * the method ref() when it starts using it, and deref() when it does not need
+ * the MountPointObserver any more.
+ *
+ * The object will not be deleted immediately if the reference count reaches
+ * zero. The object will only be destroyed when the next periodic update of
+ * the free space information happens, and the reference count is still zero.
+ * This approach makes it possible to re-use the object if a new user requests
+ * the free space for the same mount point before the next update.
+ */
+class MountPointObserver : public QObject
+{
+    Q_OBJECT
+
+    explicit MountPointObserver(const QString& mountPoint, QObject* parent = 0);
+    virtual ~MountPointObserver() {}
+
+public:
+    /**
+     * Obtains information about the available space on the observed mount point.
+     */
+    KDiskFreeSpaceInfo spaceInfo() const { return m_spaceInfo; }
+
+    /**
+     * Call this function to indicate that the caller intends to continue using this object. An
+     * internal reference count is increased then. When the observer is not needed any more,
+     * deref() should be called, which decreases the reference count again.
+     */
+    void ref() { ++m_referenceCount; }
+
+    /**
+     * This function can be used to indicate that the caller does not need this MountPointObserver
+     * any more. Internally, a reference count is decreased. If the reference count is zero while
+     * update() is called, the object deletes itself.
+     */
+    void deref()
+    {
+        --m_referenceCount;
+        Q_ASSERT(m_referenceCount >= 0);
+    }
+
+    /**
+     * Returns a MountPointObserver for the given \a path. If the caller intends to continue using
+     * the returned object, it must call its ref() method.
+     */
+    static MountPointObserver* observerForPath(const QString& path);
+
+signals:
+    /**
+     * This signal is emitted if the information that spaceInfo() will return has changed.
+     */
+    void spaceInfoChanged();
+
+public slots:
+    /**
+     * If this slot is invoked, MountPointObserver checks if the available space on the observed
+     * mount point has changed, and emits spaceInfoChanged() if that is the case.
+     */
+    void update();
+
+private:
+    const QString m_mountPoint;
+    int m_referenceCount;
+    KDiskFreeSpaceInfo m_spaceInfo;
+
+    friend class MountPointObserverCache;
+};
+
+#endif