ADC 400F Manual descarregar pdf (Página 24)

Chapter 2. Setting up the software

Í As previously mentioned, our event processor class must be derived from a CEventProcessor.

This class deﬁnition does that.

Ï The TreeParameter package provides both individual parameters (CTreeParameter), and arrays of

parameters, (CTreeParameterArray). In this application we will create a

CTreeParameterArray that will have one element for each channel of the CAEN V785. This data

member will be a reference to that array. A reference in C++ is a variable that operates like a pointer

with the notation of something that is not a pointer. For example, if I have a pointer p to a structure

containing an element b, I would access that element using the notation: p->b. If I have a reference r

to the same structure, I would access element b using the notation r.b.

Ð The m_nId member variable will be used to hold the id of the packet our event processor is

supposed to decode.

Ñ The m_nSlot member variable will be used to hold the geographical address of the CAEN V785

we are unpacking. This member is used as a sanity check. Sanity checks double check that the code

you write is operating the way you think it should. In this case, if the packet that matches our id does

not contain data that is from the ADC with the correct geographical address, we know that

something has gone seriously wrong. It is a good practice to employ sanity checks whenever you can

think of one.

Ò The constructor is called to initialize the members of an object of class MyEventProcessor. It’s

parameters are as follows:

ourId

Provides the packet id that this object will locate and unpack. By parameterizing this, our class

can unpack more than one packet id as long as the packet body is data from a single CAEN

V785 ADC

ourSlot

Provides the slot number of the ADC we expect to see in the packet of type ourId. This

enables us to perform the sanity check we described earlier.

baseParameterName

CTreeParameter objects have a parameter name, this parameter name becomes the SpecTcl

parameter name. In the case of CTreeParameterArray objects, the parameter name becomes

a base name and actual parameters have a period and an element number appended to this

basename. For example, a ten parameter array with the base name george might create

SpecTcl parameters george.00, george.01 ... george.09. The baseParameterName

will be used to set the CTreeParameterArray base name.

(10) A destructor is necessary when classes use dynamcially allocated data, in order to prevent memory

leaks when an object is destroyed.

(11) operator() allows objects of a class to be treated as functions that can be called. Objects of this

sort behave as functions that can retain state between calls. The function call operator of a

CEventProcessor is a virtual function which means that the appropriate function for pointer to an

object derived from CEventProcessor will be selected at run time from the actual class of the

object the pointer points to (in this case a MyEventProcessor. The function call operator for

1 2 ... 19 20 21 22 23 24 25 26 27 28 29 ... 73 74

Sem comentários

ADC 400F Manual Página 24