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// mktime.c (emx+gcc) -- Copyright (c) 1990-1996 by Eberhard Mattes
//
// $Id: mytime.cpp,v 1.3 2001/09/19 18:14:31 peter Exp $
//
// The emx libraries are not distributed under the GPL. Linking an
// application with the emx libraries does not cause the executable to be
// covered by the GNU General Public License. You are allowed to change
// and copy the emx library sources if you keep the copyright message
// intact.
//
// Modifications for Turquoise SuperStat copyright (c) 2000-2001 Peter
// Karlsson.
#include <time.h>
#include <limits.h>
#include "mytime.h"
#include "utility.h"
static long day(long, long, long);
// This variation of the mktime function will not do GMT adjustments on the
// output.
time_t my_mktime(struct tm *t)
{
long x;
long long r;
// tm_mon must be in range. The other members are not restricted.
if (t->tm_mon < 0)
{
// Avoid applying the `/' and `%' operators to negative numbers
// as the results are implementation-defined for negative
// numbers.
t->tm_year -= 1 + ((-t->tm_mon) / 12);
t->tm_mon = 12 - ((-t->tm_mon) % 12);
}
if (t->tm_mon >= 12)
{
t->tm_year += (t->tm_mon / 12);
t->tm_mon %= 12;
}
x = day(t->tm_year + 1900, t->tm_mon + 1, t->tm_mday);
if (-1 == x)
return (time_t) -1;
/* 719528 = day(1970, 1, 1) */
r = (long long) (x - 719528) * 24 * 60 * 60;
/* This expression is not checked for overflow. */
x = t->tm_sec + 60 * t->tm_min + 60 * 60 * t->tm_hour;
r += x;
if (r < 0 || r > INFINITY || r == (time_t)-1)
return (time_t) -1;
return (time_t) r;
}
/* year >= 1582, 1 <= month <= 12, 1 <= day <= 31 */
/** Helper function that returns the day number for a given date. */
static long day(long year, long month, long day)
{
long result;
if (year < 1582 || year >= INT_MAX / 365)
return -1;
result = 365 * year + day + 31 * (month - 1);
if (month <= 2)
-- year;
else
result -= (4 * month + 23) / 10;
result += year / 4 - (3 * (year / 100 + 1)) / 4;
return result;
}
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