gettimeofday

有些事看起来很简单，真的做好却需要费一番力气。
今天闲来无事，决定做个小程序，把刚写的程序中用到的gettimeofday函数取出的时间，转换成标准的时间格式（YYYY-MM-DD HH24:MI:SS.USEC），很快把程序做出来了。

#include <stdio.h>

#include <sys/time.h>

//typedef long long Int64;

#define BEIJINGTIME 8;

main()

{

struct timeval tv;

struct timezone tz;

long tm = 0;

long sec = 0, usec = 0;

int yy = 0, mm = 0, dd = 0, hh = 0, mi = 0, ss = 0, ms =0;

int m[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

int i;

gettimeofday(&tv, &tz);

sec = tv.tv_sec;

sec = sec + 60*60*BEIJINGTIME;

usec = tv.tv_usec;

//年

yy = sec/(60*60*24*(365*4+1)/4) + 1970;

//日

dd = sec/(60*60*24) - ((yy - 1970)*365 + (yy - 1968)/4);

//月

if(0 == yy%1000)

{

if(0 == (yy/1000)%4)

{

m[1] = 29;

}

}

else

{

if(0 == yy%4)

{

m[1] = 29;

}

}

for(i = 1; i <= 12; i++)

{

if(dd - m[i] < 0)

{

break;

}

else

{

dd = dd -m[i];

}

}

mm = i;

//小时

hh = sec/(60*60)%24;

//分

mi = sec/60 - sec/(60*60)*60;

//秒

ss = sec - sec/60*60;

ms = usec;

printf("%d-%02d-%02d %02d:%02d:%02d.%06d/n", yy, mm, dd, hh, mi, ss, ms);

return 1;

}

执行结果开起来也没问题；

2009-11-27 12:37:38.435576

乍一看，程序似乎没有什么问题，仔细看上面的程序，却有很多疏漏，由于对闰年的考虑不够周全，当时间到达每年年初在某段时间内会出现年和天的取值错误问题，当然，我这个程序只是做出来玩玩，不一定有多大用处，但把程序做的离完美一点不是坏事。

考虑闰年的计算修改程序如下：

#include <stdio.h>

#include <string.h>

#include <sys/time.h>

#define BEIJINGTIME 8

#define DAY (60*60*24)

#define YEARFIRST 2001

#define YEARSTART (365*(YEARFIRST-1970) + 8)

#define YEAR400 (365*4*100 + (4*(100/4 - 1) + 1))

#define YEAR100 (365*100 + (100/4 - 1))

#define YEAR004 (365*4 + 1)

#define YEAR001 365

/*

取当前时间，精确到微秒；

*/

int main(int argc, char *argv[])

{

struct timeval tv;

long sec = 0, usec = 0;

int yy = 0, mm = 0, dd = 0, hh = 0, mi = 0, ss = 0, ms = 0;

int ad = 0;

int y400 = 0, y100 = 0, y004 = 0, y001 = 0;

int m[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

int i;

memset(&tv, 0, sizeof(timeval));

gettimeofday(&tv, NULL);

sec = tv.tv_sec;

usec = tv.tv_usec;

sec = sec + (60*60)*BEIJINGTIME;

ad = sec/DAY;

ad = ad - YEARSTART;

y400 = ad/YEAR400;

y100 = (ad - y400*YEAR400)/YEAR100;

y004 = (ad - y400*YEAR400 - y100*YEAR100)/YEAR004;

y001 = (ad - y400*YEAR400 - y100*YEAR100 - y004*YEAR004)/YEAR001;

yy = y400*4*100 + y100*100 + y004*4 + y001*1 + YEARFIRST;

dd = (ad - y400*YEAR400 - y100*YEAR100 - y004*YEAR004)%YEAR001;

//月 日

if(0 == yy%1000)

{

if(0 == (yy/1000)%4)

{

m[1] = 29;

}

}

else

{

if(0 == yy%4)

{

m[1] = 29;

}

}

for(i = 1; i <= 12; i++)

{

if(dd - m[i] < 0)

{

break;

}

else

{

dd = dd -m[i];

}

}

mm = i;

//小时

hh = sec/(60*60)%24;

//分

mi = sec/60 - sec/(60*60)*60;

//秒

ss = sec - sec/60*60;

ms = usec;

printf("%d-%02d-%02d %02d:%02d:%02d.%06d/n", yy, mm, dd, hh, mi, ss, ms);

return 1;

}

到目前为止，我觉得没有问题了。

以上程序仅供娱乐。如果问题，欢迎指正。