Xenix sys/select.h for System V?

[Brandon S. Allbery KB8JRR]

As quoted from <1991Jan31.224424.27733 at jwt.UUCP> by john at jwt.UUCP (John Temples):
+---------------
| macros I assume are in it: FD_SETSIZE, FD_ISSET, FD_SET, FD_CLR, and
| FD_ZERO.  There's also a missing typedef for "fd_set".  Has anyone
| already ported this program to System V, or can you point me to a
| System V equivalent for these Xenix functions?
+---------------

They came from 4.3BSD, and as such are publicly available e.g. on uunet.
But here's a simplistic version that will serve:

	#include <sys/param.h>
	#ifndef NBPL
	#define NBPL (sizeof (long) * 8)
	#endif

	#define FD_SETSIZE NOFILE
	typedef long fd_set[(FD_SETSIZE + NBPL - 1) / NBPL];

	#define FD_SET(fd,p) ((p)[(fd) / NBPL] |= (1 << ((fd) % NBPL)))
	#define FD_CLR(fd,p) ((p)[(fd) / NBPL] &= ~(1 << ((fd) % NBPL)))
	#define FD_ISSET(fd,p) ((p)[(fd) / NBPL] & (1 << ((fd) % NBPL)))

(Note:  these are not necessarily the fastest way to do it.)

BTW:  they may be defined somewhere else on the system.  But if they aren't,
chances are the compile will eventually fail with a missing symbol "select".
If so, you may be able to use poll (look for poll(S) or poll(2), depending on
whether the manuals have been screwed with or not); it doesn't use these
macros, but you may be able to write a select() based on poll().  If not,
you're out of luck.  Not all System Vs have networking built in.

++Brandon
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