Full anatomy of the Linux kernel mktime.c

The definition of the TM structure is inside the time.h.

struct TM {    int tm_sec;    int tm_min;    int tm_hour;    int tm_mday;    int Tm_mon;    int tm_year;    int tm_wday;    int tm_yday;    int tm_isdst;};

/* * LINUX/KERNEL/MKTIME.C * * (c) 1991 Linus Torvalds */#include <time.h>/* * This isn ' t the library routine, it is only used in the kernel. * As such, we don ' t care on years<1970 etc, but assume everything * is OK. Similarly, TZ etc is happily ignored. We just do everything * as easily as possible. Let's find something public for the library * routines (although I think Minix times are public). *//* * PS. I hate whoever though up the year 1970-couldn ' t they has gotten * a leap-year instead?
 I also hate Gregorius, Pope or No. i ' M grumpy. */#define MINUTE 60//一分钟60秒. Here 60 is the count in seconds # # HOUR (60*minute)//hour 60 Minutes # define Day (24*hour)//24 hours a year (365*day)//365 days/day/* inte    restingly, we assume leap-years */static int month[12] = {//Initialize the number of seconds to start every one months, that is, the starting time in seconds 0, day* (+), day* (31+29),     day* (31+29+31), day* (31+29+31+30), day* (31+29+31+30+31), day* (31+29+31+30+31+30), day* (31+29+31+30+31+30+31), day* (31+29+31+30+31+30+31+31), day* (31+29+31+30+31+30+31+31+30), day* (31+29+31+30+31+30+31+31+30+31), DAY* (31    +29+31+30+31+30+31+31+30+31+30)};long kernel_mktime (struct TM * tm) {long res;    int year; Year = tm->tm_year-70;//from the beginning of 1970. Year get is and 70 years difference/* Magic offsets (y+1) needed to get leapyears right.*/res = year*year + day* ((year+1)/4);//Leap day multiple days re s + = month[tm->tm_mon];//time is accurate to month/* and (y+2) here. If it wasn ' t a leap-year, we have to adjust */if (tm->tm_mon>1 && ((year+2)%4)//due to be counted from 1970, here year+2 can be coupled on a leap year ... In other words, 1972 is a leap year, but the annual difference is 2. The 2 is aligned here.
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。。 Res-= Day;//year is not a leap year.    Minus one day res + = day* (tm->tm_mday-1);    Res + = hour*tm->tm_hour;    Res + = minute*tm->tm_min; Res + = tm->tm_sec;//Time accurate to seconds return res;}

Full anatomy of the Linux kernel mktime.c