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fakeftime.c
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C/C++ Source or Header
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1995-04-27
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3KB
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112 lines
/*
* fake ftime, assumes you have gettimeofday
*/
#include <sys/types.h>
#include <sys/time.h>
/* <sys/time.h> should have included <time.h>, cross your fingers... */
#include <sys/timeb.h>
#include <stdlib.h>
#define DUNNO 1000000L /* impossible seconds timezone offset */
/*
- secswest - intuit the timezone, portably
*/
static long /* seconds west of GMT, or DUNNO */
secswest(now, localp)
time_t now;
struct tm *localp; /* result of localtime(&now) */
{
struct tm localt;
struct tm gmt;
register struct tm *a;
register struct tm *b;
# define LG a = &localt, b = &gmt
# define GL a = &gmt, b = &localt
register long sw;
register char *newstz;
/* special hack primarily for testing */
newstz = getenv("NEWSTZ");
if (newstz != NULL)
return(atol(newstz));
/* get local and GMT, broken down */
localt = *localp;
gmt = *gmtime(&now);
/* simplify things: decide whether local is ahead of or behind GMT */
if (localt.tm_year < gmt.tm_year)
LG; /* local first */
else if (localt.tm_year > gmt.tm_year)
GL; /* GMT first */
else if (localt.tm_yday < gmt.tm_yday)
LG;
else if (localt.tm_yday > gmt.tm_yday)
GL;
else if (localt.tm_hour < gmt.tm_hour)
LG;
else if (localt.tm_hour > gmt.tm_hour)
GL;
else if (localt.tm_min < gmt.tm_min)
LG;
else if (localt.tm_min > gmt.tm_min)
GL;
else if (localt.tm_sec < gmt.tm_sec)
LG;
else if (localt.tm_sec > gmt.tm_sec)
GL;
else
return(0); /* no difference -- local is GMT! */
/* a is now the earlier time, b the later */
/* deal with year boundaries */
if (a->tm_year != b->tm_year && a->tm_yday >= 364 && b->tm_yday == 0)
a->tm_yday = -1; /* Dec 31 == Jan 0 */
else if (a->tm_year != b->tm_year)
return(DUNNO); /* something strange here */
/* we're now in the same year; deal with day boundaries */
if (a->tm_yday != b->tm_yday && a->tm_yday == b->tm_yday - 1)
a->tm_hour -= 24; /* 2200 Sun == -0200 Mon */
else if (a->tm_yday != b->tm_yday)
return(DUNNO);
/* we're now in the same day, so now it's easy */
sw = (b->tm_hour - a->tm_hour)*3600L + (b->tm_min - a->tm_min)*60L +
(b->tm_sec - a->tm_sec);
/* and get the sign right */
if (a == &gmt) /* local ahead, i.e. east, of GMT */
return(-sw);
else
return(sw);
}
int
ftime(tb)
struct timeb *tb;
{
struct timeval tv;
int ret;
struct tm *nowp;
long sw;
ret = gettimeofday(&tv, (struct timezone *)NULL);
tb->time = tv.tv_sec;
tb->millitm = (tv.tv_usec + 500) / 1000;
nowp = localtime(&tb->time);
tb->dstflag = nowp->tm_isdst;
sw = secswest(tb->time, nowp);
if (sw != DUNNO)
tb->timezone = (sw + 30) / 60;
else
tb->timezone = 0; /* for lack of anything better to do */
return(ret);
}