timer.h

/* File:     timer.h
 *
 * Purpose:  Define a macro that returns the number of seconds that 
 *           have elapsed since some point in the past.  The timer
 *           should return times with microsecond accuracy.
 *
 * Note:     The argument passed to the GET_TIME macro should be
 *           a double, *not* a pointer to a double.
 *
 * Example:  
 *    #include "timer.h"
 *    . . .
 *    double start, finish, elapsed;
 *    . . .
 *    GET_TIME(start);
 *    . . .
 *    Code to be timed
 *    . . .
 *    GET_TIME(finish);
 *    elapsed = finish - start;
 *    printf("The code to be timed took %e seconds\n", elapsed);
 */
#ifndef _TIMER_H_
#define _TIMER_H_

#include <sys/time.h>

#define GET_TIME(now) { \
   struct timeval t; \
   gettimeofday(&t, NULL); \
   now = t.tv_sec + t.tv_usec/1000000.0; \
}

/**
 * 获得当前时间
 *
 *   int len = 10;
 *   char buf[len];
 *   NOW_TIME(buf, len);
 *   printf("%s\n", buf);
 *
 */

#define NOW_TIME(buf, len) { \
    time_t nowtime; \
    nowtime = time(NULL); \
    struct tm *local; \
    local = localtime(&nowtime); \
    strftime(buf, len, "%H:%M:%S", local); \
}
#endif