58 lines
1.3 KiB
C
58 lines
1.3 KiB
C
#include <time.h>
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/* seconds per day */
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#define SPD 24*60*60
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/* days per month -- nonleap! */
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static const short __spm[13] =
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{ 0,
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(31),
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(31+28),
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(31+28+31),
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(31+28+31+30),
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(31+28+31+30+31),
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(31+28+31+30+31+30),
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(31+28+31+30+31+30+31),
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(31+28+31+30+31+30+31+31),
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(31+28+31+30+31+30+31+31+30),
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(31+28+31+30+31+30+31+31+30+31),
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(31+28+31+30+31+30+31+31+30+31+30),
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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 inline int isleap(int year) {
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/* every fourth year is a leap year except for century years that are
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* not divisible by 400. */
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/* return (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0)); */
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return (!(year%4) && ((year%100) || !(year%400)));
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}
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struct tm *gmtime(const time_t *timep) {
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static struct tm r;
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time_t i;
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register time_t work=*timep%(SPD);
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r.tm_sec=work%60; work/=60;
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r.tm_min=work%60; r.tm_hour=work/60;
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work=*timep/(SPD);
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r.tm_wday=(4+work)%7;
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for (i=1970; ; ++i) {
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register time_t k=isleap(i)?366:365;
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if (work>=k)
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work-=k;
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else
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break;
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}
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r.tm_year=i-1900;
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r.tm_yday=work;
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r.tm_mday=1;
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if (isleap(i) && (work>58)) {
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if (work==59) r.tm_mday=2; /* 29.2. */
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work-=1;
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}
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for (i=11; i && (__spm[i]>work); --i) ;
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r.tm_mon=i;
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r.tm_mday+=work-__spm[i];
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return &r;
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}
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