4.2. Modifications to skeleton.cpp

This section will provide a guide to the modifications you will need to make to a skeleton.cpp and files it depends on to be able to use it with the RingDaq readout framework.

The primary modifications are needed in readevt and the set of headers and stem from the fact that spectrodaq.h no longer exists as RingDaq by definition does not use spectrodaq, and the fact that therefore DAQWordBufferPtr objects also no longer exist. DAQWordBufferPtr objects are replaced by ordinary pointers to ordinary memory.

Since a DAQWordBufferPtr does a good job of imitating an ordinary pointer, these modifications should have minimal impact on your actual code.

I'm going to show two fairly empty readevt functions and what you have to do to them. The first is the 'standard' version, where data are taken into DAQWordBufferPtr objects directly, while the second uses the DAQWordBufferPtr::CopyIn function and a local buffer to improve the SPDAQ performance.

Let's look at the relevant pieces of the first case. Many of the standard comments have been removed for the sake of brevity, as is the standard body.

...
#include <spectrodaq.h>  
...
#include <daqinterface.h> 
...
WORD
#ifdef __unix__
readevt (DAQWordBufferPtr& bufpt)  
#else 
readevt (WORD* bufpt)
#endif
{
#ifdef __unix__
    DAQWordBufferPtr _sbufpt = bufpt; 
#else
    WORD *_sbufpt = bufpt;
#endif
    LOGICAL reject;

    reject   = FALSE;
    {
    // code here that invokes putbufw a bunch of times explicitly or
    // implicitly.
    ...
    }
    IF(reject) return 0;
#ifdef __unix__
    return bufpt.GetIndex() - _sbufpt.GetIndex();  
#else
    return (bufpt - _sbufpt);
#endif
}


                

In fact the non __unix__ version of readevt is actually almost correct for the RingDaq. Here's how this code fragment would be modified:

... 
WORD
readevt (WORD* bufpt)   
{

    WORD *_sbufpt = bufpt;

    LOGICAL reject;

    reject   = FALSE;
    {    
     // readout code that uses putbufw etc.
     ...
    }

    IF(reject) return 0;

    return (bufpt - _sbufpt);  
}

                

Now lets look at the case where readevt reads data into a local buffer and then uses DAQWordBuferPtr::CopyIn to transfer it to the spectrodaq buffer. Typically readevt functions have the following form:

                    
static WORD localBuffer[8192];                       
...
WORD
#ifdef __unix__
readevt (DAQWordBufferPtr& bufpt)
#else 
readevt (WORD* bufpt)
#endif
{
#ifdef __unix__
    DAQWordBufferPtr _sbufpt = bufpt;
#else
    WORD *_sbufpt = bufpt;
#endif
    LOGICAL reject;

    reject   = FALSE;
    {
        WORD* localbufpt = localbuffer;  
    // code here that invokes localputbufw a bunch of times explicitly or
    // implicitly. putting data into localbuffer.
    ...
        int nWords = localbufpt - localBuffer;  
        bufpt.CopyIn(localBuffer, 0, nWords);   
        bufpt += nWords;                        
    }

    
    IF(reject) return 0;
#ifdef __unix__
    return bufpt.GetIndex() - _sbufpt.GetIndex(); 
#else
    return (bufpt - _sbufpt);
#endif
}
                

Key features of this scheme are:

With RingDaq, since readevt is recdeiving an ordinary pointer parameter, there are no efficiency gains to be had by using a local buffer. In order to avoid having to recast all the readout code in terms of e.g. putbufw the following trick can be used:

#include <stdint.h>     
...
readevt (uint16_t bufpt)
    WORD *_sbufpt = bufpt;
    LOGICAL reject;

    reject   = FALSE;
    {
        WORD* localbufpt = bufpt;    
    // code here that invokes localputbufw a bunch of times explicitly or
    // implicitly. putting data into localbuffer.
    ...
        bufpt = localbuffer;   
    }
    
    
    
    IF(reject) return 0;
    return (bufpt - _sbufpt);
}