Difference between revisions of "AnyWave:BuildReader"

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(AwReaderPlugin and AwFileReader classes)
(AwReaderPlugin and AwFileReader classes)
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Click [http://meg.univ-amu.fr/AnyWave/tuto/BuildReader/ades_reader.h Here to download this file]

Revision as of 13:47, 23 March 2015

One important thing with AnyWave is to be able to read a data file.
Although that AnyWave is able to read some common EEG or MEG file formats, you might need to read a particular data file.
The only way to achieve that is to build a Reader plug-in for AnyWave.
This will require implementing a C++ plug-in using the SDK.
See the previous sections of the Developer's corner to see how to build the SDK and use it to build a new plug-in.

Let's start with the basic cmake project that we will modify to suit our needs.

ADES reader as example

AnyWave is able to read .ades file format which is a simple file format built upon a text header file and a binary data file.
This 'plug-in' is embedded within AnyWave but we are going to implement it as an external plug-in, for the sake of demonstration.

Define the C++ classes

A C++ plug-in is defined by two classes:

  • A class that describes the plug-in to AnyWave.
  • A class that describes the core mechanism of the plug-in.

That is true for all kind of plug-ins in AnyWave.

AwReaderPlugin and AwFileReader classes

As mentioned above, two C++ classes must be described and implemented to build a Reader plug-in.
Here are the two classes, described within one header file:

#include <AwReaderInterface.h>
#include <QtCore>
#include <QDataStream>
class ADesReader : public AwFileReader // our class must derived from AwFileReader
	Q_OBJECT                            // Q_OBJECT and Q_INTERFACES macro are specific to the Qt Framework.
	Q_INTERFACES(AwFileReader)          // They indicate that the object is also derived from QObject and implements the Qt signals and slots mechanism.
	ADesReader(const QString& filename);
	~ADesReader() { cleanUpAndClose(); }
// The three methods above need to be implemented. There are virtuals method defined in AwFileReader.
	long readDataFromChannels(float start, float duration, QList<AwChannel *> &channelList);     // This method will get data from the file and fill channels with them.
	FileStatus openFile(const QString &path);                                                    // This method will open the file and return a status.
	FileStatus canRead(const QString &path);                                                     // This method will check if the file format is correct and return a status.
// The method above is optional but it is a good practice to implement it.
        void cleanUpAndClose();              //  A cleanup method to clean memory and close the file.
// Here we define variables and methods required by our plug-in.
	QFile m_headerFile;                  // A QFile to handle the text header file.
	QFile m_binFile;                     // A QFile to handle the binary data file.
	QTextStream m_headerStream;          // A stream object to read the content of the header file.
	QDataStream m_binStream;             // A stream object to read the content of the data file.
	float m_samplingRate;                // A variable to store the global sampling rate.
	int m_nSamples;                      // A variable to store the number of samples.
	QString m_binPath;                   // A variable to store the file path to the binary data file.
class ADesReaderPlugin : public AwReaderPlugin  // The plugin class must derived from AwReaderPlugin
	Q_OBJECT                             // Define the object as a QObject. The interface for the plugin must be AwReaderPlugin
	ADesReaderPlugin();                 // The constructor
	ADesReader *newInstance(const QString& filename) { return new ADesReader(filename); }   // MANDATORY method that must instantiate the AwFileReader derived class for our plug-in.
#endif // DESREADER_H

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