Re: writing to record

[Marty Kraimer <mrk@aps.anl.gov>]

Liyu, Andrei wrote:

> I would like to write to waveform record (long or float type) directly.
> At first, I can use dbPutField( ...) but it would take much time because
> I need to change 30% of record's array.
> At second,
>
> dbScanLock( ...)
> write to record array
> if I need to give sign CA monitors
> 	precord->putf = TRUE and dbProcess( ...)	
> dbScanUnlock( ...)
>
> Am I right?
>
> Thanks, Andrei.
>
>  
I assume you are concerned about performance and thus want to directly 
access the array.
I will also assume that your code is not run under a scan task, i.e. it 
is not part of record or device support or a subroutine connected to a 
record.

Do the following:

At initialization:

struct dbAddr addr;
dbCommon *pdbCommon;
rset               *prset;


   status = dbNameToAddr("<name>",&addr);
   if(status) /*error handle it!!! */
   pdbCommon = (dbCommon *)addr.precord;
   prset = pdbCommon->rset;



Now get ready to access the array

   long no_elements,offset,nNew;
    double *pdata;

   dbScanLock(pdbCommon);
   status = prset->get_array_info(&addr,&no_elements,&offset)
   /* check the following things to see if your code can handle the array
     Is offset 0?
     The current number of elements is no_elements.
     The maximum number of elements is addr.no_elements.
      Are these OK with you?
     Is addr.field_type OK with you?
     You probable want DBF_DOUBLE.
      This example assumes double
   */
     if(addr.field_type!=DBF_DOUBLE) /*ERROR handle it*/
     pdata = (double *)addr.pfield;
     /* You can now write the data. also set nNew */
     status = put_array_info(&addr,nNew);
     status = dbProcess(pdbCommon);
    dbScanUnlock(pdbCommon);