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59 lines
1.5 KiB
59 lines
1.5 KiB
2 years ago
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/*
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* linux/kernel/mktime.c
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*
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* (C) 1991 Linus Torvalds
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*/
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#include <time.h>
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/*
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* This isn't the library routine, it is only used in the kernel.
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* as such, we don't care about years<1970 etc, but assume everything
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* is ok. Similarly, TZ etc is happily ignored. We just do everything
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* as easily as possible. Let's find something public for the library
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* routines (although I think minix times is public).
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*/
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/*
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* PS. I hate whoever though up the year 1970 - couldn't they have gotten
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* a leap-year instead? I also hate Gregorius, pope or no. I'm grumpy.
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*/
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#define MINUTE 60
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#define HOUR (60*MINUTE)
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#define DAY (24*HOUR)
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#define YEAR (365*DAY)
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/* interestingly, we assume leap-years */
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static int month[12] = {
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0,
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DAY*(31),
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DAY*(31+29),
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DAY*(31+29+31),
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DAY*(31+29+31+30),
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DAY*(31+29+31+30+31),
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DAY*(31+29+31+30+31+30),
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DAY*(31+29+31+30+31+30+31),
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DAY*(31+29+31+30+31+30+31+31),
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DAY*(31+29+31+30+31+30+31+31+30),
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DAY*(31+29+31+30+31+30+31+31+30+31),
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DAY*(31+29+31+30+31+30+31+31+30+31+30)
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};
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long kernel_mktime(struct tm * tm)
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{
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long res;
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int year;
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if (tm->tm_year < 70 ) tm->tm_year += 100; /* gohigh */
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year = tm->tm_year - 70;
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/* magic offsets (y+1) needed to get leapyears right.*/
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res = YEAR*year + DAY*((year+1)/4);
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res += month[tm->tm_mon];
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/* and (y+2) here. If it wasn't a leap-year, we have to adjust */
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if (tm->tm_mon>1 && ((year+2)%4))
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res -= DAY;
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res += DAY*(tm->tm_mday-1);
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res += HOUR*tm->tm_hour;
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res += MINUTE*tm->tm_min;
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res += tm->tm_sec;
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return res;
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}
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