143 lines
2.2 KiB
C
143 lines
2.2 KiB
C
/*
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* Gutils -
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*
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* - date conversion functions
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*
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* Geraint, 22 May, 28 Oct 91.
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*/
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#include "windows.h"
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#include "gutils.h"
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#include <string.h>
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BOOL gdi_isleap(LONG year);
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/*---static data--------------------------------------------*/
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int monthdays[] = {
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31,
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28,
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31,
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30,
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31,
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30,
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31,
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31,
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30,
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31,
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30,
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31
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};
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/*--public functions--------------------------------------*/
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void APIENTRY
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gdate_daytodmy(LONG days, int FAR* yrp, int FAR* monthp, int FAR* dayp)
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{
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int years;
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int nleaps;
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int month;
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int mdays;
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/* get number of completed years and calc leap days */
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years = (int) (days / 365);
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days = days % 365;
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nleaps = (years / 4) - (years / 100) + (years / 400);
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while (nleaps > days) {
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days += 365;
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years--;
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nleaps = (years / 4) - (years / 100) + (years / 400);
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}
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days -= nleaps;
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/* add one year for current (non-complete) year */
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years++;
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/* current month */
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for (month = 0; month < 12; month++) {
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mdays = monthdays[month];
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if (gdi_isleap(years) && (month == 1)) {
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mdays++;
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}
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if (days == mdays) {
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days = 0;
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month++;
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break;
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} else if (days < mdays) {
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break;
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} else {
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days -= mdays;
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}
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}
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/* conv month from 0-11 to 1-12 */
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if (monthp != NULL) {
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*monthp = month+1;
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}
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if (dayp != NULL) {
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*dayp = (int) days + 1;
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}
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if (yrp != NULL) {
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*yrp = years;
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}
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}
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LONG APIENTRY
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gdate_dmytoday(int yr, int month, int day)
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{
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int nleaps;
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int i;
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long ndays;
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/* exclude the current year */
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yr--;
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nleaps = (yr / 4) - (yr / 100) + (yr / 400);
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/* in any given year, day 0 is jan1 */
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month--;
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day--;
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ndays = 0;
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for (i = 0; i < month ; i++) {
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ndays += monthdays[i];
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if (gdi_isleap(yr+1) && (i == 1)) {
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ndays++;
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}
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}
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ndays = ndays + day + nleaps + (yr * 365L);
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return(ndays);
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}
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int APIENTRY
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gdate_monthdays(int month, int year)
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{
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int ndays;
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ndays = monthdays[month - 1];
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if (gdi_isleap(year) && (month == 2)) {
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ndays++;
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}
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return(ndays);
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}
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int APIENTRY
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gdate_weekday(long daynr)
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{
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return((int) ((daynr + 1) % 7));
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}
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/* internal functions-----------------------------------------*/
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BOOL
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gdi_isleap(LONG year)
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{
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if ( ((year % 4) == 0) &&
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(((year % 100) != 0) ||
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((year % 400) == 0))) {
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return TRUE;
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} else {
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return FALSE;
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}
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}
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