Editing STIR Howto Create Custom InputFileFormat (section)

== Creating classes for reading events ==

Again, files for ECAT962 provide some example. You need to create a class for cLMD from your scanner, which inherits from CListModeData. A minimal example header file looks like

<pre>
template <class CListRecordT> class CListModeDataMyScanner : public CListModeData
{
public:
	CListModeDataMyScanner( const std::string& listmode_filename_prefix);
	
	virtual std::string get_name() const;
	virtual shared_ptr <CListRecord> get_empty_record_sptr() const;
	virtual Succeeded get_next_record(CListRecord& record_of_general_type) const;
	virtual Succeeded reset();
	
	virtual SavedPosition save_get_position();
	virtual Succeeded set_get_position(const SavedPosition&);

	virtual bool has_delayeds() const;
	
private:
	std::string listmode_filename_prefix;
	mutable shared_ptr<InputStreamWithRecords<CListRecordT, bool> > current_lm_data_ptr;
	mutable std::vector< unsigned int> saved_get_positions;
	Succeeded open_lm_file() const;
};
</pre>

There are also two inherited data members 
* shared_ptr<Scanner> scanner_sptr
* shared_ptr<ExamInfo> exam_info_sptr
which have to be set in the derived class.

The filename of the file to be read has to be given as an argument to the constructor. It does the following:

* Set inherited exam info pointer. Minimum: set empty ExamInfo
** this->exam_info_sptr.reset(new ExamInfo);

* Set inherited Scanner pointer. If user-defined scanner, do something like this
<pre>
	scanner_sptr.reset(new Scanner(Scanner::User_defined_scanner, "MyScanner",
	   124, 63,      // int num_detectors_per_ring_v, int num_rings_v,
	   120,      // int max_num_non_arccorrected_bins_v,
	   120,      // int default_num_arccorrected_bins_v,
	   63, 10.0,      // float inner_ring_radius_v, float average_depth_of_interaction_v,
	   3.2, 1.2, 0.0,      // float ring_spacing_v, float bin_size_v, float intrinsic_tilt_v,
	   1, 2,       // int num_axial_blocks_per_bucket_v, int num_transaxial_blocks_per_bucket_v,
	   1, 1,       // int num_axial_crystals_per_block_v, int num_transaxial_crystals_per_block_v,
	   1,       // int num_axial_crystals_per_singles_unit_v,
	   1,      // int num_transaxial_crystals_per_singles_unit_v,
	   1      // int num_detector_layers_v);
	));
</pre>

* call open_lm_file(). This function in a minimal version looks like
<pre>
template <class CListRecordT>
Succeeded
CListModeDataMyScanner<CListRecordT>::
open_lm_file() const
{
	// Could put something here to fiddle with file extensions, let's assume listmode_filename_prefix=filename
	cerr << "CListModeDataMyScanner: opening file " << listmode_filename_prefix << endl;
	shared_ptr<istream> stream_ptr(new fstream(listmode_filename_prefix.c_str(), ios::in | ios::binary ));
	if(!(*stream_ptr))
	{
		warning("CListModeDataMyScanner: cannot open file %s\n", filename.c_str());
		return Succeeded::no;
	}
	stream_ptr->seekg(32); // first 32 bytes of file used for signature, thus move stream forward.
	current_lm_data_ptr.reset(
			new InputStreamWithRecords<CListRecordT, bool>
			( stream_ptr, sizeof(CListTimeDataMyScanner),
					sizeof(CListTimeDataMyScanner),
					ByteOrder::little_endian !=ByteOrder::get_native_order())); // Pay attention to byte order in your binary file!
	return Succeeded::yes;
}
</pre>

Last thing to do is to create an instance of your templated class by
* template class CListModeDataMyScanner<CListRecordMyScanner>;