ndet_read.c

操作系统SunOS 4.1.3版本的源码

#ifndef	lint
#ifdef sccs
static	char sccsid[] = "@(#)ndet_read.c 1.1 92/07/30 Copyr 1985 Sun Micro";
#endif
#endif

/*
 * Copyright (c) 1985 by Sun Microsystems, Inc.
 */

/*
 * Ndet_read.c - Notifier's version of read.  Will do notification cycle
 *		   if not already in the middle of it.
 */

#include <sunwindow/ntfy.h>
#include <sunwindow/ndet.h>
#include <sunwindow/ndis.h>	/* For ndis_client == NTFY_CLIENT_NULL check */
#include <errno.h>

extern	errno;

static	Notify_value	ndet_read_in_func();

static	int	ndet_read_done;

static	Notify_client ndet_read_nclient = (Notify_client)&ndet_read_done;

extern int
read(fd, buf, nbytes)
	register int fd;
	char *buf;
	int nbytes;
{
	int ndelay;
	Notify_error return_code;

	/*
	 * Do real read if in middle of notification loop or
	 * no other clients and no notifications pending.
	 * Also, don't dispatch events if haven't started notifier and
	 * "background" dispatching hasn't been turned on.
	 */
	if ((ndet_flags & NDET_STARTED) ||
	    ((!(ndet_flags & NDET_STARTED)) &&
	      (!(ndet_flags & NDET_DISPATCH))) ||
	    ((ndet_clients == NTFY_CLIENT_NULL) &&
	      (ndis_clients == NTFY_CLIENT_NULL)))
		return(notify_read(fd, buf, nbytes));
	/* Set up read condition */
	if (notify_set_input_func(ndet_read_nclient, ndet_read_in_func, fd) ==
	    NOTIFY_FUNC_NULL && notify_errno == NOTIFY_BADF) {
		errno = EBADF;
		return(-1);
	}
	/* Set up variable that will notice the notification */
	ndet_read_done = 0;
	/* Setup flag to break out of notify_start if fd is non-blocking */
/*	if (ndelay = (FD_BIT(fd) & ndet_fndelay_mask)) */
	if (ndelay = FD_ISSET(fd, &ndet_fndelay_mask))
		ndet_flags |= NDET_NO_DELAY;
	/*
	 * Start notifier.  Wouldn't return until (1) input available on fd,
	 * (2) some other notifier client calls notify_stop(), (3) there
	 * is an error during the real select call (e.g., EWOULDBLOCK,
	 * EBADF, EINTR on slow fd).  Note: Using errno from the real
	 * select as return value for read.  Will this work in all cases?
	 */
	return_code = notify_start();
	ndet_flags &= ~NDET_NO_DELAY;
	/* Clear read condition from notifier */
	(void) notify_set_input_func(ndet_read_nclient, NOTIFY_FUNC_NULL, fd);
	/* If no read notification then assume error return from real read */
	if (ndet_read_done) {
		/* Do real read */
		return(notify_read(fd, buf,nbytes));
	} else {
		if (return_code == NOTIFY_OK && ndelay)
			errno = EWOULDBLOCK;
		return(-1);
	}
}

/* ARGSUSED */
static Notify_value
ndet_read_in_func(nclient, fd)
	Notify_client nclient;
	int fd;
{
	ndet_read_done = 1;
	(void) notify_stop();
	return(NOTIFY_DONE);
}