#ifndef lintstatic	char sccsid[] = "@(#)select.c 1.1 92/07/30 SMI"; /* from S5R2 1.1 */#endif/* * Code for various kinds of delays.  Most of this is nonportable and * requires various enhancements to the operating system, so it won't * work on all systems.  It is included in curses to provide a portable * interface, and so curses itself can use it for function keys. */#include "curses.ext"#include <signal.h>#define NAPINTERVAL 100/* From early specs - this may change by 4.2BSD */struct _timeval {	long tv_sec;	long tv_usec;};#ifdef FIONREAD# ifndef TIOCREMOTE/* * Decide if we can emulate select but don't have it.  This is * intended to be true only on 4.1BSD, not 4.2BSD or USG. */#  define NEEDSELECT# endif#endif#ifdef NEEDSELECT/* * Emulation of 4.2BSD select system call.  This is somewhat crude but * better than nothing.  We do FIONREAD on each fd, and if we have to * wait we use nap to avoid a busy wait.  The resolution of the nap * will hurt response - so will the fact that we ignore the write fds. * If we are simulating nap with a 1 second sleep, this will be very poor. * * nfds is the number of fds to check - this is usually 20. * prfds is a pointer to a bit vector of file descriptors - in the case *	where nfds < 32, prfds points to an integer, where bit 1<<fd *	is 1 if we are supposed to check file descriptor fd. * pwfds is like prfds but for write checks instead of read checks. * ms is the max number of milliseconds to wait before returning failure. * The value returned is the number of file descriptors ready for input. * The bit vectors are updated in place. */intselect(nfds, prfds, pwfds, pefds, timeout)register int nfds;int *prfds, *pwfds, *pefds;struct _timeval *timeout;{	register int fd;	register int rfds = *prfds;	register int n;	int nwaiting, rv = 0;	long ms = timeout->tv_sec * 1000 + timeout->tv_usec / 1000;	for (;;) {		/* check the fds */		for (fd=0; fd<nfds; fd++)			if (1<<fd & rfds) {				ioctl(fd, FIONREAD, &nwaiting);				if (nwaiting > 0) {					rv++;				} else					*prfds &= ~(1<<fd);			}		if (rv)			return rv;		/* Nothing ready.  Should we give up? */		if (ms <= 0)			return 0;		*prfds = rfds;	/* we clobbered it, so restore. */		/* Wait a bit */		n = NAPINTERVAL;		if (ms < NAPINTERVAL)			n = ms;		ms -= n;		napms(n);	}}#else#ifndef FIONREADintselect(nfds, prfds, pwfds, pefds, ms)register int nfds;int *prfds, *pwfds, *pefds;struct _timeval *ms;{	/* Can't do it, but at least compile right */	return ERR;}#endif FIONREAD#endif NEEDSELECT