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/*
* prettydate - convert a time stamp to something readable
*/
#include <stdio.h>
#include "ntp_fp.h"
#include "ntp_unixtime.h" /* includes <sys/time.h> */
#include "lib_strbuf.h"
#include "ntp_stdlib.h"
#include "ntp_assert.h"
static char *common_prettydate(l_fp *, int);
const char *months[] = {
"Jan", "Feb", "Mar", "Apr", "May", "Jun",
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
};
static const char *days[] = {
"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
};
/* Helper function to handle possible wraparound of the ntp epoch.
Works by periodic extension of the ntp time stamp in the NTP epoch. If the
'time_t' is 32 bit, use solar cycle warping to get the value in a suitable
range. Also uses solar cycle warping to work around really buggy
implementations of 'gmtime()' / 'localtime()' that cannot work with a
negative time value, that is, times before 1970-01-01. (MSVCRT...)
Apart from that we're assuming that the localtime/gmtime library functions
have been updated so that they work...
*/
/* solar cycle in secs, unsigned secs and years. And the cycle limits.
**
** And an explanation. The julian calendar repeats ever 28 years, because it's
** the LCM of 7 and 4, the week and leap year cycles. This is called a 'solar
** cycle'. The gregorian calendar does the same as long as no centennial year
** (divisible by 100, but not 400) goes in the way. So between 1901 and 2099
** (inclusive) we can warp time stamps by 28 years to make them suitable for
** localtime() and gmtime() if we have trouble. Of course this will play
** hubbubb with the DST zone switches, so we should do it only if necessary;
** but as we NEED a proper conversion to dates via gmtime() we should try to
** cope with as many idiosyncrasies as possible.
*/
#define SOLAR_CYCLE_SECS 0x34AADC80UL /* 7*1461*86400*/
#define SOLAR_CYCLE_YEARS 28
#define MINFOLD -3
#define MAXFOLD 3
struct tm *
ntp2unix_tm(
u_long ntp, int local
)
{
struct tm *tm;
int32 folds = 0;
time_t t = time(NULL);
u_int32 dwlo = (int32)t; /* might expand for SIZEOF_TIME_T < 4 */
#if ( SIZEOF_TIME_T > 4 )
int32 dwhi = (int32)(t >> 16 >> 16);/* double shift: avoid warnings */
#else
/*
* Get the correct sign extension in the high part.
* (now >> 32) may not work correctly on every 32 bit
* system, e.g. it yields garbage under Win32/VC6.
*/
int32 dwhi = (int32)(t >> 31);
#endif
/* Shift NTP to UN*X epoch, then unfold around currrent time. It's
* important to use a 32 bit max signed value -- LONG_MAX is 64 bit on
* a 64-bit system, and it will give wrong results.
*/
M_ADD(dwhi, dwlo, 0, ((1UL << 31)-1)); /* 32-bit max signed */
if ((ntp -= JAN_1970) > dwlo)
--dwhi;
dwlo = ntp;
# if SIZEOF_TIME_T < 4
# error sizeof(time_t) < 4 -- this will not work!
# elif SIZEOF_TIME_T == 4
/*
** If the result will not fit into a 'time_t' we have to warp solar
** cycles. That's implemented by looped addition / subtraction with
** M_ADD and M_SUB to avoid implicit 64 bit operations, especially
** division. As he number of warps is rather limited there's no big
** performance loss here.
**
** note: unless the high word doesn't match the sign-extended low word,
** the combination will not fit into time_t. That's what we use for
** loop control here...
*/
while (dwhi != ((int32)dwlo >> 31)) {
if (dwhi < 0 && --folds >= MINFOLD)
M_ADD(dwhi, dwlo, 0, SOLAR_CYCLE_SECS);
else if (dwhi >= 0 && ++folds <= MAXFOLD)
M_SUB(dwhi, dwlo, 0, SOLAR_CYCLE_SECS);
else
return NULL;
}
# else
/* everything fine -- no reduction needed for the next thousand years */
# endif
/* combine hi/lo to make time stamp */
t = ((time_t)dwhi << 16 << 16) | dwlo; /* double shift: avoid warnings */
# ifdef _MSC_VER /* make this an autoconf option? */
/*
** The MSDN says that the (Microsoft) Windoze versions of 'gmtime()'
** and 'localtime()' will bark on time stamps < 0. Better to fix it
** immediately.
*/
while (t < 0) {
if (--folds < MINFOLD)
return NULL;
t += SOLAR_CYCLE_SECS;
}
# endif /* Microsoft specific */
/* 't' should be a suitable value by now. Just go ahead. */
while ( (tm = (*(local ? localtime : gmtime))(&t)) == 0)
/* seems there are some other pathological implementations of
** 'gmtime()' and 'localtime()' somewhere out there. No matter
** if we have 32-bit or 64-bit 'time_t', try to fix this by
** solar cycle warping again...
*/
if (t < 0) {
if (--folds < MINFOLD)
return NULL;
t += SOLAR_CYCLE_SECS;
} else {
if ((++folds > MAXFOLD) || ((t -= SOLAR_CYCLE_SECS) < 0))
return NULL; /* That's truely pathological! */
}
/* 'tm' surely not NULL here... */
NTP_INSIST(tm != NULL);
if (folds != 0) {
tm->tm_year += folds * SOLAR_CYCLE_YEARS;
if (tm->tm_year <= 0 || tm->tm_year >= 200)
return NULL; /* left warp range... can't help here! */
}
return tm;
}
static char *
common_prettydate(
l_fp *ts,
int local
)
{
char *bp;
struct tm *tm;
u_long sec;
u_long msec;
LIB_GETBUF(bp);
sec = ts->l_ui;
msec = ts->l_uf / 4294967; /* fract / (2 ** 32 / 1000) */
tm = ntp2unix_tm(sec, local);
if (!tm)
snprintf(bp, LIB_BUFLENGTH,
"%08lx.%08lx --- --- -- ---- --:--:--",
(u_long)ts->l_ui, (u_long)ts->l_uf);
else
snprintf(bp, LIB_BUFLENGTH,
"%08lx.%08lx %s, %s %2d %4d %2d:%02d:%02d.%03lu",
(u_long)ts->l_ui, (u_long)ts->l_uf,
days[tm->tm_wday], months[tm->tm_mon],
tm->tm_mday, 1900 + tm->tm_year, tm->tm_hour,
tm->tm_min, tm->tm_sec, msec);
return bp;
}
char *
prettydate(
l_fp *ts
)
{
return common_prettydate(ts, 1);
}
char *
gmprettydate(
l_fp *ts
)
{
return common_prettydate(ts, 0);
}
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