mirror of
https://git.FreeBSD.org/src.git
synced 2024-12-08 09:39:38 +00:00
2b15cb3d09
Thanks to roberto for providing pointers to wedge this into HEAD. Approved by: roberto
107 lines
2.8 KiB
C
107 lines
2.8 KiB
C
/*
|
|
* timetoa.c -- time_t related string formatting
|
|
*
|
|
* Written by Juergen Perlinger (perlinger@ntp.org) for the NTP project.
|
|
* The contents of 'html/copyright.html' apply.
|
|
*
|
|
* Printing a 'time_t' has a lot of portability pitfalls, due to it's
|
|
* opaque base type. The only requirement imposed by the standard is
|
|
* that it must be a numeric type. For all practical purposes it's a
|
|
* signed int, and 32 bits are common.
|
|
*
|
|
* Since the UN*X time epoch will cause a signed integer overflow for
|
|
* 32-bit signed int in the year 2038, implementations slowly move to
|
|
* 64bit base types for time_t, even in 32-bit environments.
|
|
*
|
|
* As the printf() family has no standardised type specifier for time_t,
|
|
* guessing the right output format specifier is a bit troublesome and
|
|
* best done with the help of the preprocessor and "config.h".
|
|
*/
|
|
|
|
#include "config.h"
|
|
|
|
#include <math.h>
|
|
#include <stdio.h>
|
|
|
|
#include "timetoa.h"
|
|
#include "ntp_assert.h"
|
|
#include "lib_strbuf.h"
|
|
|
|
/*
|
|
* Formatting to string needs at max 40 bytes (even with 64 bit time_t),
|
|
* so we check LIB_BUFLENGTH is big enough for our purpose.
|
|
*/
|
|
#if LIB_BUFLENGTH < 40
|
|
# include "GRONK: LIB_BUFLENGTH is not sufficient"
|
|
#endif
|
|
|
|
/*
|
|
* general fractional timestamp formatting
|
|
*
|
|
* Many pieces of ntpd require a machine with two's complement
|
|
* representation of signed integers, so we don't go through the whole
|
|
* rigamarole of creating fully portable code here. But we have to stay
|
|
* away from signed integer overflow, as this might cause trouble even
|
|
* with two's complement representation.
|
|
*/
|
|
const char *
|
|
format_time_fraction(
|
|
time_t secs,
|
|
long frac,
|
|
int prec
|
|
)
|
|
{
|
|
char * cp;
|
|
u_int prec_u;
|
|
u_time secs_u;
|
|
u_int u;
|
|
long fraclimit;
|
|
int notneg; /* flag for non-negative value */
|
|
ldiv_t qr;
|
|
|
|
DEBUG_REQUIRE(prec != 0);
|
|
|
|
LIB_GETBUF(cp);
|
|
secs_u = (u_time)secs;
|
|
|
|
/* check if we need signed or unsigned mode */
|
|
notneg = (prec < 0);
|
|
prec_u = abs(prec);
|
|
/* fraclimit = (long)pow(10, prec_u); */
|
|
for (fraclimit = 10, u = 1; u < prec_u; u++) {
|
|
DEBUG_INSIST(fraclimit < fraclimit * 10);
|
|
fraclimit *= 10;
|
|
}
|
|
|
|
/*
|
|
* Since conversion to string uses lots of divisions anyway,
|
|
* there's no big extra penalty for normalisation. We do it for
|
|
* consistency.
|
|
*/
|
|
if (frac < 0 || frac >= fraclimit) {
|
|
qr = ldiv(frac, fraclimit);
|
|
if (qr.rem < 0) {
|
|
qr.quot--;
|
|
qr.rem += fraclimit;
|
|
}
|
|
secs_u += (time_t)qr.quot;
|
|
frac = qr.rem;
|
|
}
|
|
|
|
/* Get the absolute value of the split representation time. */
|
|
notneg = notneg || ((time_t)secs_u >= 0);
|
|
if (!notneg) {
|
|
secs_u = ~secs_u;
|
|
if (0 == frac)
|
|
secs_u++;
|
|
else
|
|
frac = fraclimit - frac;
|
|
}
|
|
|
|
/* finally format the data and return the result */
|
|
snprintf(cp, LIB_BUFLENGTH, "%s%" UTIME_FORMAT ".%0*ld",
|
|
notneg? "" : "-", secs_u, prec_u, frac);
|
|
|
|
return cp;
|
|
}
|