C/C++ 获取时间间隔的方法

Returns the number of clock ticks elapsed since the program was launched.

The macro constant expression CLOCKS_PER_SEC specifies the relation between a clock tick and a second (clock ticks per second).

The initial moment of reference used by clock as the beginning of the program execution may vary between platforms. To calculate the actual processing times of a program, the value returned by clock should be compared to a value returned by an initial call to clock.

通过两次调用clock函数可以得到起始时间和结束时间，从而得到毫秒级的时间差

gettimeofday函数方式

C/C++语言中有个timeval结构是可以精确到毫秒，可以利用timeval来记录起始时间和结束时间

struct timeval {
               time_t      tv_sec;     /* seconds */
               SUSEconds_t tv_usec;    /* microseconds */
           };

通过调用gettimeofday函数可以得到用timeval结构记录的当前时间

int gettimeofday(struct timeval *tv, struct timezone *tz);

具体实现

#include <time.h>

#include <sys/time.h>

class ClockTool
{
    public:
    ClockTool()
        : m_begin(0), m_end(0)
    {
    }

    inline void begin()
    {
        m_begin = clock();
    }

    inline void end()
    {
        m_end = clock();
    }

    inline void reset()
    {
        m_begin = 0;
        m_end = 0;
    }

    float getInterval()
    {
        if (m_end < m_begin)
        {
            return 0;
        }
        return (double)(m_end - m_begin)/CLOCKS_PER_SEC;
    }

    private:
    clock_t m_begin;
    clock_t m_end;
};

class TimeTool
{
    public:
    TimeTool()
    {
        reset();
    }

    inline void begin()
    {
        gettimeofday(&m_begin, NULL);
    }

    inline void end()
    {
        gettimeofday(&m_end, NULL);
    }

    inline void reset()
    {
        memset(&m_begin, 0, sizeof(struct timeval));
        memset(&m_end, 0, sizeof(struct timeval));
    }

    float getInterval()
    {
        if (m_end.tv_usec < m_begin.tv_usec)
        {
            m_end.tv_usec += 1000;
            m_end.tv_sec = m_end.tv_sec - 1;
        }
        return (m_end.tv_sec - m_begin.tv_sec) + (m_end.tv_usec - m_begin.tv_usec) / 1000000.0;
    }

    private:
    struct timeval m_begin;
    struct timeval m_end;
};