structure alignment on Suns...

[Peter Morreale]

I have an application in which I write/read structures to files.

In an earlier version, I was able to have both the Sun3 and Sun4
versions read/write the same files.  I realize that I got lucky, since
the member alignment is different on the two machines.

Now however, I increased both the sizes and number of members
and things don't work between the two machines.  I'd like to get that
functionality back if I can by playing games with member alignment if I
can.  

Portability is *not* an issue here.  This is a local app.
likewise, it will be a long time before we move off of the Suns.

Can someone familiar with this show me what needs to go where? 
(and/or tell me if this is possible anymore?)

How does Sun align struct members?  Word boundries?  Of what size?
(as you will see most of the members are char arrays...)

As this may not be of general interest, email is fine......

Here is the current definition of the structure:

------------------start of indxstruct.h----------------------

 /*
 * Define the maximum number of chars for use in the structure.
 * (includes the null byte)
 */

#define LISTCHARS 	23
#define LOGCHARS 	9
#define NMECHARS 	32
#define PHNCHARS 	20
#define EMLCHARS 	39
#define DTECHARS 	9
#define TMECHARS 	5
#define LCTCHARS 	27
#define RFRCHARS 	11
#define DIVCHARS 	6
#define AREACHARS 	21
#define SEQCHARS	7
#define	SCICHARS	5
#define	USRCHARS	9
#define	BUFCHARS	12


/*  The index structure.  This contains all the fields of a contact. */

typedef struct index {
	long	offset;			/* offset in text file	*/
	short	len;			/* len of note string	*/

	char	area[AREACHARS];	/* subject area		*/
	char	user[USRCHARS];		/* xconslog user's name */
	char	seq[SEQCHARS];		/* contact sequence. #	*/
	char	tmstmp[BUFCHARS];	/* Enter timestamp	*/
	char    scinum[SCICHARS];	/* Scientist number	*/
	char	list_str[LISTCHARS];  	/* List string 		*/
	char	log[LOGCHARS];		/* Contact logon name 	*/
	char	nme[NMECHARS];		/* Contact name		*/
	char	tme[TMECHARS];          /* Time spent on contact*/
	char	phn[PHNCHARS];		/* Contact phone number */
	char	eml[EMLCHARS];          /* Email address	*/
	char	lct[LCTCHARS];		/* location of contact	*/
	char	div[DIVCHARS];		/* Contact division	*/
	char    dte[DTECHARS];		/* Contact enter date   */
	char    d_dte[DTECHARS];	/* done date		*/

	char	del_con;		/* delete flag		*/
	char	contact;		/* type of contact	*/
	char	done;			/* done flag		*/
	char	rpt;			/* report flag		*/
	char    site;			/* site flag		*/
	char    refer;			/* referral  flag	*/
	char	buffer2[BUFCHARS];	/* unused		*/
	char    flag2;			/* unused		*/
} Construct;


extern Construct indx;
----------------end of indxstruct.h---------------------------

This certainly isn't critical as I can constrain the users to the 
Sun4 machine, but if I can, I'd like this new version to match the old.

Thanks,
-PWM
------------------------------------------------------------------
Peter W. Morreale                  email:  morreale at ncar.ucar.edu
Nat'l Center for Atmos Research    voice:  (303) 497-1293
Scientific Computing Division     
Consulting Office
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