Experimental Physics and
Industrial Control System

Marty Kraimer <[email protected]> · Thu, 03 Jun 1999 08:24:33 -0500

Ron Chestnut wrote:
> 
> Hello All,
> 
> I think I've seen the answer to this, I may have even asked the question before.
> 
> I have a 10 element waveform (type float) from which I wish to extract each
> element into an individual AI.
> 
> I could code 10 individual subArray records, each mapped to another element, but
> a subroutine record seems easier. If my 10 element waveform VAL is linked to A
> of the subroutine record, is the code simply:
> 
> psub->b=psub->a[0]
> psub->c=psub->a[1], etc.?
> 
> That seems much too easy, and "a" is not an array, right?
> 
> /Ron Chestnut

The safe way to do this is

#include "dbAccess.h"
...

DBADDR *pdbAddr
...
pdbAddr = dbGetPdbAddrFromLink(&psub->inpa);
if(!pdbAddr) { /*ERROR DO SOMETHING*/}
...

The DBADDR structure contains all the info you need, i.e.

typedef struct dbAddr{
        struct dbCommon *precord;/* address of record                   */
        void    *pfield;        /* address of field                     */
        void    *pfldDes;       /* address of struct fldDes             */
        void    *asPvt;         /* Access Security Private              */
        long    no_elements;    /* number of elements (arrays)          */
        short   field_type;     /* type of database field               */
        short   field_size;     /* size (bytes) of the field being accessed */
        short   special;        /* special processing                   */
        short   dbr_field_type; /* field type as seen by database request*/
                                /*DBR_STRING,...,DBR_ENUM,DBR_NOACCESS*/
}DBADDR;

In particular

pfield is the addresss of actual data
no_elements is actual size of the array
field_type is the data type, i.e. DBF_xxx

You should check that the data type is what you expect, for example

if(pdbAddr->field_type != DBF_DOUBLE|| pdbAddr->no_elements<=myindex) {
    /*error */
} else {
   double mydata;
   double *subdata = (double *)pdbAddr->pfield;
   mydata = subdata[myindex]
}

If the array varies in size you should also call the subroutine RSET
get_array_info routine to get the current size (note that no_elements is the
maximum size). This can be done by

struct rset     *prset;
prset=dbGetRset(pdbAddr);
...
long *no_elements = 0;
long *offset = 0;

if(prset && (prset->get_array_info)) {
    status = (*prset->get_array_info)(pdbAddr,&no_elements,&offset)
   ...

}

Marty Kraimer

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System