getutim.c

来自「TCP-IP红宝书源代码」· C语言 代码 · 共 42 行

/* getutim.c - getutim */

#include <conf.h>
#include <kernel.h>
#include <sleep.h>
#include <date.h>
#include <network.h>

/*------------------------------------------------------------------------
 * getutim  --  obtain time in seconds past Jan 1, 1970, ut (gmt)
 *------------------------------------------------------------------------
 */
SYSCALL
getutim(unsigned long *timvar)
{
	int	dev;
	int	len;
	int	ret;
	u_long	now;
	u_long	utnow;
	char	*msg = "No time server response\n";

	wait(clmutex);
	ret = OK;
	if (clktime < SECPERHR) {	/* assume small numbers invalid	*/
		if ((dev=open(UDP, TSERVER, ANYLPORT)) == SYSERR ||
		    control(dev,DG_SETMODE,DG_TMODE|DG_DMODE) == SYSERR) {
			panic(msg);
			ret = SYSERR;
		}
		write(dev, msg, 2);	/* send junk packet to prompt */
		if (read(dev,&utnow,4) != 4) {
			ret = SYSERR;
		} else
			clktime = net2xt( net2hl(utnow) );
		close(dev);
	}
	*timvar = clktime;
	signal(clmutex);
	return(ret);
}