演示了指针的使用

/*
下面这个例子演示了指针是对应着地址,当改变地址的内容的时候，该指针的内容也改变
*/
#include <Winsock2.h>
#include <stdio.h>
#include <stdio.h>
#include <sys/timeb.h>
#include <time.h>

int evutil_gettimeofday(struct timeval *tv, struct timezone *tz)
{
struct _timeb tb;

if(tv == NULL)
return -1;

_ftime(&tb);
tv->tv_sec = (long) tb.time;
tv->tv_usec = ((int) tb.millitm) * 1000;
return 0;
}

#define evutil_timeradd(tvp, uvp, vvp)							/
do {														/
(vvp)->tv_sec = (tvp)->tv_sec + (uvp)->tv_sec;			/
(vvp)->tv_usec = (tvp)->tv_usec + (uvp)->tv_usec;       /
if ((vvp)->tv_usec >= 1000000) {						/
(vvp)->tv_sec++;									/
(vvp)->tv_usec -= 1000000;							/
}														/
} while (0)
#define	evutil_timersub(tvp, uvp, vvp)						/
do {													/
(vvp)->tv_sec = (tvp)->tv_sec - (uvp)->tv_sec;		/
(vvp)->tv_usec = (tvp)->tv_usec - (uvp)->tv_usec;	/
if ((vvp)->tv_usec < 0) {							/
(vvp)->tv_sec--;								/
(vvp)->tv_usec += 1000000;						/
}													/
} while (0)
#define	evutil_timerclear(tvp)	(tvp)->tv_sec = (tvp)->tv_usec = 0

int main(int argc, char* argv[])
{
struct timeval tv;
struct timeval *tv_p;

evutil_gettimeofday(&tv,NULL);

tv_p = &tv;

printf( "current time is : %s/n", ctime( &tv_p->tv_sec) );
//把地址赋给指针

struct timeval tvm;
tvm.tv_sec = 10;
tvm.tv_usec = 0;
//增加tv的时间
evutil_timeradd(&tv,&tvm,tv_p);

printf("After add 10 second is :%s/r/n",ctime( &tv_p->tv_sec));

return 0;
}