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Subject: Field support
From: "Rees, NP (Nick)" <nick.rees@diamond.ac.uk>
To: <core-talk@aps.anl.gov>
Date: Fri, 17 Apr 2009 16:02:11 +0100
All,

Attached is the result of the field support work I did at the codeathon.
There are two files - a gzipped patch file which is a patch against the
version of base I downloaded this morning labeled 17 April 2009, and a
makeBaseApp application which implements a default version of field
support.

New files in base are:
 - src/dbStatic/fldSup.h   - This declares the new field Support
structure and helper routines. There are a
                             number of forward structure declarations,
because I wasn't sure about the exact
                             order of include files.
 - src/fldSupParams.c      - additional dbStaticLib routines for saving
and restoring field support parameters.
 - src/db/dbAccessFldSup.c - These routines have extracted all the if
(prset->function) (*prset->function)(param)
                             type calls for field support into one file
so they are done consistently. It also
                             reduces the number of changes needed in
dbAccess.c and the convert routines.
 - src/db/dbAccessFldSup.h - header file for the above. Since all the
field support routines now have their
                             prototypes fully declared this uncovered a
number of times where longs were being
                             passed as int's in get_precision in the
convert routines. This is a bug and should
                             be fixed.

Other files changed (apart from Makefiles) are dbAccess.c and the
convert routines in src/db; dbBase.h, dbStaticLib.c and dbLexRoutines in
src/dbStatic, and iocInit.c. I have re-used the driver support registry
because I couldn't be bothered to implement something special for field
support (why do we have all these separate registry's anyway?).

The test app provides a default version of field support
(fldSupDefault.c) that provides a fairly traditional implementation for
cvt_dbaddr, get_array_info, put_array_info, get_units, get_precision,
get_graphic_double, get_control_double and get_alarm_double. It isn't
ready for prime time - there are a few printf's just to reassure you
that things are working. However it is basically there. The dbd for the
VAL field of a waveform record now looks like:

	field(VAL,DBF_NOACCESS) {
		prompt("Value")
		asl(ASL0)
		special(SPC_DBADDR)
		fldSup(fldSupDefault_fset)
		fldSup_bptr(BPTR)
		fldSup_type(FTVL)
		fldSup_nelm(NELM)
		fldSup_nord(NORD)
		fldSup_prec(PREC)
		fldSup_units(furlongs)
		fldSup_hopr(HOPR)
		fldSup_lopr(LOPR)
		fldSup_drvh(HOPR)
		fldSup_drvl(LOPR)
		fldSup_hihi(HOPR)
		fldSup_high(HOPR)
		fldSup_low(LOPR)
		fldSup_lolo(LOPR)
		pp(TRUE)
		extra("void *		val")
	}

This is a lot longer than before, but you no longer need any of the
record support routines...

I hope its fairly obvious, but the values in the fldSup_ bits can be
other fields in the same record or constants. If you leave them out then
the corresponding field support routine returns S_db_noRSET.

As to what else to do, I was going to experiment with supporting arrays
and maybe strings a bit more. I am not sure what else it is good for,
but that may come.

I also don't quite know how this fits in with Andrew's code generation
work, but that is mainly because I don't know what that is. Andrew, is
there any reference for that anywhere - I would be interested in knowing
what you are getting at there - I know what you are doing in principal,
but not in practice.

Any comments are welcome.

Cheers,

Nick Rees
Principal Software Engineer           Phone: +44 (0)1235-778430
Diamond Light Source                  Fax:   +44 (0)1235-446713

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Attachment: fldSupBase_20090417.patch.gz
Description: fldSupBase_20090417.patch.gz

Attachment: testFldSup.tgz
Description: testFldSup.tgz


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