Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!samsung!aplcen!haven!uvaarpa!mmdf
From: mdb@kosciusko.esd.3com.com (Mark D. Baushke)
Newsgroups: comp.lang.perl
Subject: Re: do_select() bug
Message-ID: <1870@uvaarpa.virginia.edu>
Date: 20 Dec 89 04:59:01 GMT
Sender: mmdf@uvaarpa.virginia.edu
Reply-To: mdb@kosciusko.esd.3com.com
Lines: 59

On 19 Dec 89 07:04:01 GMT, lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall) said:

Larry> I've got a do_select for patch 7 that should work everwhere
Larry> that uses bitmaps composed of ints or longs.  Even places that
Larry> don't have FD_SET(), etc.  (if there are any such).  

There are indeed machines without FD_SET(). For example, SunOS 3.x
does NOT have it. I believe that at least some versions Ultrix (e.g., 2.0)
also do not have it.

I have seen something like the following code used on SunOS 3.x and
Ultrix 2.0 machines as a workaround.

/*
 * Ultrix 2.0/SunOS 3.x File Descriptor Compatibility Macros
 *
 * BIG NOTE!!! This will only allow fd_sets of 32 bits (assuming that's
 * the size of an int). Also, SunOS 3.x only allows 30 FDs in any case.
 *
 */

#ifndef FD_SET

#define NBBY    8               /* number of bits in a byte */

#define	NFDBITS	(sizeof(int) * NBBY)

/*
 * This is for Ultrix 2.0 and SunOS 3.x where fd_sets only have 1 element.
*/

/*
	I'm assuming that the only use of howmany is 
	howmany(FD_SETSIZE, NFDBITS), which should always return 1.
	The following code will need to be uncommented otherwise.

#define howmany(x, y) (((x)+((y)-1))/(y))
*/

#define howmany(x,y) 1

#ifndef FD_SETSIZE
#define FD_SETSIZE	NFDBITS
#endif

#define FD_SET(n, p)    ((p)->fds_bits[0] |= (1 << ((n) % NFDBITS)))
#define FD_CLR(n, p)    ((p)->fds_bits[0] &= ~(1 << ((n) % NFDBITS)))
#define FD_ISSET(n, p)  ((p)->fds_bits[0] & (1 << ((n) % NFDBITS)))
#define FD_ZERO(p)      ((p)->fds_bits[0] = 0)

#endif /* FD_SET */

Larry> Someone will have to tell me about "sellist" structures,
Larry> though.

Hope this helps,
-- 
Mark D. Baushke
mdb@ESD.3Com.COM