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/*****************************************************************************/
/* */
/* mktime.c */
/* */
/* Make calendar time from broken down time and cleanup */
/* */
/* */
/* */
/* (C) 2002 Ullrich von Bassewitz */
/* Wacholderweg 14 */
/* D-70597 Stuttgart */
/* EMail: uz@musoftware.de */
/* */
/* */
/* This software is provided 'as-is', without any expressed or implied */
/* warranty. In no event will the authors be held liable for any damages */
/* arising from the use of this software. */
/* */
/* Permission is granted to anyone to use this software for any purpose, */
/* including commercial applications, and to alter it and redistribute it */
/* freely, subject to the following restrictions: */
/* */
/* 1. The origin of this software must not be misrepresented; you must not */
/* claim that you wrote the original software. If you use this software */
/* in a product, an acknowledgment in the product documentation would be */
/* appreciated but is not required. */
/* 2. Altered source versions must be plainly marked as such, and must not */
/* be misrepresented as being the original software. */
/* 3. This notice may not be removed or altered from any source */
/* distribution. */
/* */
/*****************************************************************************/
#include <limits.h>
#include <stdlib.h>
#include <time.h>
/*****************************************************************************/
/* Data */
/*****************************************************************************/
#define JANUARY 0
#define FEBRUARY 1
#define DECEMBER 11
#define JAN_1_1970 4 /* 1/1/1970 is a thursday */
static const unsigned char MonthLength [] = {
31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
};
static const unsigned MonthDays [] = {
0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
};
/*****************************************************************************/
/* Code */
/*****************************************************************************/
static unsigned char __fastcall__ IsLeapYear (unsigned Year)
/* Returns 1 if the given year is a leap year */
{
return (((Year % 4) == 0) && ((Year % 100) != 0 || (Year % 400) == 0));
}
time_t __fastcall__ mktime (register struct tm* TM)
/* Make a time in seconds since 1/1/1970 from the broken down time in TM.
** A call to mktime does also correct the time in TM to contain correct
** values.
*/
{
register div_t D;
int Max;
unsigned DayCount;
/* Check if TM is valid */
if (TM == 0) {
/* Invalid data */
goto Error;
}
/* Adjust seconds. */
D = div (TM->tm_sec, 60);
TM->tm_sec = D.rem;
/* Adjust minutes */
if (TM->tm_min + D.quot < 0) {
goto Error;
}
TM->tm_min += D.quot;
D = div (TM->tm_min, 60);
TM->tm_min = D.rem;
/* Adjust hours */
if (TM->tm_hour + D.quot < 0) {
goto Error;
}
TM->tm_hour += D.quot;
D = div (TM->tm_hour, 24);
TM->tm_hour = D.rem;
/* Adjust days */
if (TM->tm_mday + D.quot < 0) {
goto Error;
}
TM->tm_mday += D.quot;
/* Adjust month and year. This is an iterative process, since changing
** the month will change the allowed days for this month.
*/
while (1) {
/* Make sure, month is in the range 0..11 */
D = div (TM->tm_mon, 12);
TM->tm_mon = D.rem;
if (TM->tm_year + D.quot < 0) {
goto Error;
}
TM->tm_year += D.quot;
/* Now check if mday is in the correct range, if not, correct month
** and eventually year and repeat the process.
*/
if (TM->tm_mon == FEBRUARY && IsLeapYear (TM->tm_year + 1900)) {
Max = 29;
} else {
Max = MonthLength[TM->tm_mon];
}
if (TM->tm_mday > Max) {
/* Must correct month and eventually, year */
if (TM->tm_mon == DECEMBER) {
TM->tm_mon = JANUARY;
++TM->tm_year;
} else {
++TM->tm_mon;
}
TM->tm_mday -= Max;
} else {
/* Done */
break;
}
}
/* Ok, all time/date fields are now correct. Calculate the days in this
** year.
*/
TM->tm_yday = MonthDays[TM->tm_mon] + TM->tm_mday - 1;
if (TM->tm_mon > FEBRUARY && IsLeapYear (TM->tm_year + 1900)) {
++TM->tm_yday;
}
/* Calculate days since 1/1/1970. In the complete epoch (1/1/1970 to
** somewhere in 2038) all years dividable by 4 are leap years, so
** dividing by 4 gives the days that must be added cause of leap years.
** (and the last leap year before 1970 was 1968)
*/
DayCount = ((unsigned) (TM->tm_year-70)) * 365U +
(((unsigned) (TM->tm_year-(68+1))) / 4) +
TM->tm_yday;
/* Calculate the weekday */
TM->tm_wday = (JAN_1_1970 + DayCount) % 7;
/* No (US) daylight saving (for now) */
TM->tm_isdst = 0;
/* Return seconds since 1970 */
return DayCount * 86400UL +
((unsigned) TM->tm_hour) * 3600UL +
((unsigned) TM->tm_min) * 60U +
((unsigned) TM->tm_sec) -
_tz.timezone;
Error:
/* Error exit */
return (time_t) -1L;
}
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