Re: Engineering Units

[mrk@aps.anl.gov (Marty Kraimer)]

It seems that the consensus is that the units string should be null terminated.
Here is my latest thoughts of how to patch problem for now.

Changes to dbAccess.h

       will define the following:

	#define DB_UNITS_SIZE	16
  
        The current definition for DBRunits will be changed to

         #define DBRunits \
              char        units[DB_UNITS_SIZE]

        Since everything is local to an ioc it is ok to
        change from 8 characters to 16.

The get_units of each record support module will be changed from

	strncpy(units,pai->egu,sizeof(pai->egu));

to

	strncpy(units,pai->egu,DB_UNITS_SIZE);

New database access, after calling the record support get_units routine,
will force the last byte of the units string to be null

The routine that translates between old and new database access
will force the units field passed to channel access to be a null
terminated 8 byte field.


This solution has the following features:

1) New database access completely supports a 16 byte null terminated
   units string
2) Clients (database and channel access) always get a null terminated string.
3) When we go to new major EPICS release number, i.e. CA protocal change
   database access will already support 16 byte character strings.

The only impact on existing clients is that some may find 8th character
of units string missing.

If there are any objections make them soon or else I will make
these changes for release 3.12.2 which is planned for next month.

Marty Kraimer