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