Path: seismo!harvard!talcott!panda!sources-request
From: sources-request@panda.UUCP
Newsgroups: mod.sources
Subject: tm_to_time(3) -- convert broken-down time into time_t.
Message-ID: <1539@panda.UUCP>
Date: 19 Mar 86 19:28:46 GMT
Sender: jpn@panda.UUCP
Organization: Technical University of Berlin, Dept. of Computer Science
Lines: 142
Approved: jpn@panda.UUCP

Mod.sources:  Volume 4, Issue 38
Submitted by: "Oliver Laumann" <seismo!unido!tub!net>


A number of requests have been posted to the net in the past asking
for a function that can be used to convert a broken-down time (such
as returned by localtime()) into a time_t (such as returned by
time()).
The following shell archive contains a function (plus manual page)
that performs this conversion.

Regards,
    Oliver Laumann, Technical University of Berlin, Germany.
    ...ihnp4!seismo!unido!tub!net   or   net@DB0TUI6.BITNET
          ...!mcvax!unido!tub!net

---------------cut here---------------cut here---------------
#! /bin/sh
# This is a shell archive, meaning:
# 1. Remove everything above the #! /bin/sh line.
# 2. Save the resulting text in a file.
# 3. Execute the file with /bin/sh (not csh) to create the files:
#	tm_to_time.3
#	tm_to_time.c
# This archive created: Wed Mar 19 13:04:07 1986
export PATH; PATH=/bin:$PATH
echo shar: extracting "'tm_to_time.3'" '(683 characters)'
if test -f 'tm_to_time.3'
then
	echo shar: will not over-write existing file "'tm_to_time.3'"
else
cat << \SHAR_EOF > 'tm_to_time.3'
.TH MKTIME 3 "19 March 1986"
.SH NAME
tm_to_time \- convert broken-down time into time_t
.SH SYNOPSIS
.nf
.B #include <sys/types.h>
.B #include <sys/time.h>
.PP
.B time_t tm_to_time (tp);
.B struct tm *tp;
.fi
.SH DESCRIPTION
.I Tm_to_time
converts a broken-down time pointed to by
.I tp
(such as returned by
.IR localtime )
into a
.I time_t
(that is, a number of seconds since 00:00:00 GMT, Jan 1, 1970).
Thus, if
.I tm_to_time
is called with a broken-down time
returned by a call to
.I localtime
with some
.I time_t
argument,
the value obtained by
.I tm_to_time
is identical to the original
.IR time_t .
.SH AUTHOR
Oliver Laumann
.SH SEE ALSO
gettimeofday(2) or time(2), ctime(3).
SHAR_EOF
if test 683 -ne "`wc -c < 'tm_to_time.3'`"
then
	echo shar: error transmitting "'tm_to_time.3'" '(should have been 683 characters)'
fi
fi # end of overwriting check
echo shar: extracting "'tm_to_time.c'" '(1192 characters)'
if test -f 'tm_to_time.c'
then
	echo shar: will not over-write existing file "'tm_to_time.c'"
else
cat << \SHAR_EOF > 'tm_to_time.c'
#include <sys/types.h>
#include <sys/time.h>

/* Return 1 if `y' is a leap year, 0 otherwise.
 */

static int leap (y) int y; {
    y += 1900;
    if (y % 400 == 0)
	return (1);
    if (y % 100 == 0)
	return (0);
    return (y % 4 == 0);
}

/* Return the number of days between Jan 1, 1970 and the given
 * broken-down time.
 */

static int ndays (p) struct tm *p; {
    register n = p->tm_mday;
    register m, y;
    register char *md = "\37\34\37\36\37\36\37\37\36\37\36\37";

    for (y = 70; y < p->tm_year; ++y) {
	n += 365;
	if (leap (y)) ++n;
    }
    for (m = 0; m < p->tm_mon; ++m)
	n += md[m] + (m == 1 && leap (y));
    return (n);
}

/* Convert a broken-down time (such as returned by localtime())
 * back into a `time_t'.
 */

time_t tm_to_time (tp) struct tm *tp; {
    register int m1, m2;
    time_t t;
    struct tm otm;

    t = (ndays (tp) - 1) * 86400L + tp->tm_hour * 3600L
	+ tp->tm_min * 60 + tp->tm_sec;
    /*
     * Now the hard part -- correct for the time zone:
     */
    otm = *tp;
    tp = localtime (&t);
    m1 = tp->tm_hour * 60 + tp->tm_min;
    m2 = otm.tm_hour * 60 + otm.tm_min;
    t -= ((m1 - m2 + 720 + 1440) % 1440 - 720) * 60L;
    return (t);
}
SHAR_EOF
if test 1192 -ne "`wc -c < 'tm_to_time.c'`"
then
	echo shar: error transmitting "'tm_to_time.c'" '(should have been 1192 characters)'
fi
fi # end of overwriting check
#	End of shell archive
exit 0