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这是0.11内核中的一个文件/*
* linux/kernel/mktime.c
*
* (C) 1991 Linus Torvalds
*/
#include
/*
* This isn't the library routine, it is only used in the kernel.
* as such, we don't care about 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 is public).
*/
/*
* PS. I hate whoever though up the year 1970 - couldn't they have gotten
* a leap-year instead? I also hate Gregorius, pope or no. I'm grumpy.
*/
#define MINUTE 60
#define HOUR (60*MINUTE)
#define DAY (24*HOUR)
#define YEAR (365*DAY)
/* interestingly, we assume leap-years */
static int month[12] = {
0,
DAY*(31),
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;
/* magic offsets (y+1) needed to get leapyears right.*/
res = YEAR*year + DAY*((year+1)/4);
res += month[tm->tm_mon];
/* and (y+2) here. If it wasn't a leap-year, we have to adjust */
if (tm->tm_mon>1 && ((year+2)%4))
res -= DAY;
res += DAY*(tm->tm_mday-1);
res += HOUR*tm->tm_hour;
res += MINUTE*tm->tm_min;
res += tm->tm_sec;
return res;
}
看第一遍时觉得kernel_mktime()
在kernel/mktime.c 中的kernel_mktime()函数原型如下：
41 long kernel_mktime(struct tm * tm)
42 {
43 long res;
44 int year;
45
46 year = tm->tm_year - 70;
47 /* magic offsets (y+1) needed to get leapyears right.*/
48 res = YEAR*year + DAY*((year+1)/4);
49 res += month[tm->tm_mon];
50 /* and (y+2) here. If it wasn't a leap-year, we have to adjust */
51 if (tm->tm_mon>1 && ((year+2)%4))
52 res -= DAY;
53 res += DAY*(tm->tm_mday-1);
54 res += HOUR*tm->tm_hour;
55 res += MINUTE*tm->tm_min;
56 res += tm->tm_sec;
57 return res;
58 }
我的问题处在第48行的“ ((year+1)/4)“上，
((year+1)/4)是计算从1970年到现在的闰年数，
而闰年是每4年出现一次吗？不是的。400年中闰年只有97个，
所以他 这样计算出来的闰年数对吗？
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sunjiangang-ok2014-01-27 22:28:47
c87276548：kernel里头计算的这个秒数应该是1970-2038年的 所有不存在所谓的世纪年不是闰年，因为这个时间段里头只有一个世纪年
谢谢
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c872765482013-10-22 15:58:13
kernel里头计算的这个秒数应该是1970-2038年的 所有不存在所谓的世纪年不是闰年，因为这个时间段里头只有一个世纪年
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