* add the ability to limit the number of data sources in an engine; least used items drop off. the algorithm for this is pretty simplistic and not overly scalable, but that's something that can be fixed when we run into problems (e.g. setLimit(1000) or something silly =) svn path=/trunk/KDE/kdebase/workspace/plasma/lib/; revision=668927
231 lines
7.5 KiB
C++
231 lines
7.5 KiB
C++
/*
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* Copyright (C) 2006 Aaron Seigo <aseigo@kde.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Library General Public License version 2 as
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* published by the Free Software Foundation
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this program; if not, write to the
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* Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#ifndef PLASMA_DATAENGINE_H
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#define PLASMA_DATAENGINE_H
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#include <QtCore/QAtomic>
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#include <QtCore/QHash>
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#include <QtCore/QObject>
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#include <QtCore/QStringList>
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#include <KGenericFactory>
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#include <plasma_export.h>
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namespace Plasma
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{
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class DataSource;
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/**
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* @class DataEngine
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* @brief Data provider for plasmoids (Plasma plugins)
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*
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* This is the base class for DataEngines, which provide access to bodies of
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* data via a common and consistent interface. The common use of a DataEngine
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* is to provide data to a widget for display. This allows a user interface
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* element to show all sorts of data: as long as there is a DataEngine, the
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* data is retrievable.
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*
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* DataEngines are loaded as plugins on demand and provide zero, one or more
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* data sources which are identified by name. For instance, a network
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* DataEngine might provide a data source for each network interface.
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**/
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class PLASMA_EXPORT DataEngine : public QObject
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{
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Q_OBJECT
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public:
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typedef QHash<QString, DataEngine*> Dict;
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typedef QHash<QString, QVariant> Data;
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typedef QHashIterator<QString, QVariant> DataIterator;
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/**
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* Default constructor.
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*
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* @param parent The parent object.
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**/
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explicit DataEngine(QObject* parent);
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virtual ~DataEngine();
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/**
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* @return a list of all the data sources currently available via this
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* DataEngine
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**/
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virtual QStringList dataSources() const;
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/**
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* Connects a source to an object for data updates. The object must
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* have a slot with the following signature:
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*
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* SLOT(updated(QString, Plasma::DataEngine::Data))
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*
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* The data is a QHash of QVariants keyed by QString names, allowing
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* one data source to provide sets of related data.
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*
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* @param source the name of the data source
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* @param visualization the object to connect the data source to
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**/
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void connectSource(const QString& source, QObject* visualization) const;
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/**
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* Connects all sources to an object for data updates. The object must
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* have a slot with the following signature:
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*
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* SLOT(updated(QString, Plasma::DataEngine::Data))
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*
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* The data is a QHash of QVariants keyed by QString names, allowing
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* one data source to provide sets of related data.
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*
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* @param visualization the object to connect the data source to
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**/
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void connectAllSources(QObject* viualization) const;
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/**
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* Gets the Data associated with a data source.
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*
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* The data is a QHash of QVariants keyed by QString names, allowing
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* one data source to provide sets of related data.
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*
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* @param source the data source to retrieve the data for
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* @return the Data associated with the source; if the source doesn't
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* exist an empty data set is returned
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**/
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Data query(const QString& source) const;
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/**
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* Reference counting method. Calling this method increases the count
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* by one.
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**/
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void ref();
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/**
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* Reference counting method. Calling this method decreases the count
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* by one.
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**/
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void deref();
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/**
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* Reference counting method. Used to determine if this DataEngine is
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* used.
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* @return true if the reference count is zero
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**/
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bool isUsed() const;
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/**
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* Sets the icon for this data engine
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**/
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void setIcon(const QString& icon);
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/**
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* @return the name of the icon for this data engine; and empty string
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* is returned if there is no associated icon.
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**/
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QString icon() const;
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Q_SIGNALS:
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/**
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* Emitted when a new data source is created
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* @param source the name of the new data source
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**/
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void newDataSource(const QString& source);
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/**
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* Emitted when a data source is removed.
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* @param source the name of the data source that was removed
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**/
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void dataSourceRemoved(const QString& source);
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protected:
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/**
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* This method is called when the DataEngine is started. When this
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* method is called the DataEngine is fully constructed and ready to be
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* used. This method should be reimplemented by DataEngine subclasses
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* which have the need to perform a startup routine.
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**/
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virtual void init();
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/**
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* Sets a value for a data source. If the source
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* doesn't exist then it is created.
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*
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* @param source the name of the data source
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* @param value the data to associated with the source
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**/
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void setData(const QString& source, const QVariant& value);
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/**
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* Sets a value for a data source. If the source
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* doesn't exist then it is created.
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*
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* @param source the name of the data source
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* @param key the key to use for the data
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* @param value the data to associated with the source
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**/
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void setData(const QString& source, const QString& key, const QVariant& value);
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/**
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* Adds an already constructed data source. The DataEngine takes
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* ownership of the DataSource object.
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* @param source the DataSource to add to the DataEngine
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**/
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void addSource(DataSource* source);
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/**
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* Sets an upper limit on the number of data sources to keep in this engine.
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* If the limit is exceeded, then the oldest data source, as defined by last
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* update, is dropped.
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*
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* @param limit the maximum number of sources to keep active
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**/
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void setSourceLimit(uint limit);
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/* DataSource* domain(const QString &domain);
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void createDataSource(const QString& source,
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const QString& domain = QString());*/
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/**
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* Removes a data source.
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* @param source the name of the data source to remove
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**/
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void removeDataSource(const QString& source);
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/**
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* Removes all data sources
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**/
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void clearAllDataSources();
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private Q_SLOTS:
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void checkForUpdates();
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private:
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class Private;
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Private* const d;
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};
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} // Plasma namespace
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#define K_EXPORT_PLASMA_DATAENGINE(libname, classname) \
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K_EXPORT_COMPONENT_FACTORY( \
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plasma_engine_##libname, \
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KGenericFactory<classname>("plasma_engine_" #libname))
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#endif // multiple inclusion guard
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