Documenting event segment packet types

Documenting event segment packet types

By convention, events consist of packets of the following form show in the figure Event packet format

Documented event packets allow you to place entries in the event stream that document the set of event packets that can appear in the buffer. Readout software that uses documented packets are much more self documenting than those that don't.

To do this you should:

• Create instances of CDocumentedPacket for each packet you will create in your readout. Note that Daniel Bazin (bazin@nscl.msu.edu) maintains a registry of packet ids. When designing a packet consult him to get a new unique packet.
• When starting to read a packet invoke the corresponding packet object's Begin() member.
• When finished reading a pakcet, invoke the corresponding packet object's End() member.

The code fragment below shows an implementation of an event segment that uses documented packets.

	class CMySegment : public CEventSegment
	{
	private:
	   CDocumentedPacket m_MyPacket;
	 public:
	    CMySegment();
	    ...
	    virtual DAQWordBufferPtr& 
	                 Read(DAQWordBufferPtr& rBuffer);
	    ...
	};
	...
	CMySegment::CMySegment() :
	   m_MyPacket(0xaa, 
		      string("Example"),
		      string("Example tag for Readout docs"),
		      string("1.0"));
	 {}
	 
	 DAQWordBufferPtr&
	 CMySegment::Read(DAQWordBufferPtr& rBuffer)
	 {
	    ...
	    rBuffer = m_MyPacket.Begin(rBuffer);
	    // Read packet body...
	    ...
	    rBuffer = m_MyPacket.End(rBuffer);
	    
	    ...
	    return rBuffer;
	 }
      

Documenting event segment packet types