C++编写一个打印对象生命期的类：

定义：

snippet.cpp

/*
Execution timer class.
*/
class ExecuteTimer
{
public:
       ExecuteTimer();
       ~ExecuteTimer();
 
       /*\brief: Get char* type time.
       *\return: char* type time, unit:second.
       */
       char*      GetCTime();
 
       /*\brief: Get double type time.
       *\return: double type time, unit:second.
       */
       double     GetDTime();
 
       /*\brief: Reset the begin time.
       */
       void Reset();
 
       /*\brief: ostream << operator friend function.
       *\param:  os, The left operation.
       *\param:  obj, The right operation.
       *\return: std::ostream object ref..
       */
       friend std::ostream& operator << (std::ostream& os, ExecuteTimer& obj);
 
       /*\brief: ofstream << operator friend function.
       *\param:  os, The left operation.
       *\param:  obj, The right operation.
       *\return: std::ofstream object ref..
       */
       friend std::ofstream& operator << (std::ofstream& ofs, ExecuteTimer& obj);
 
private:
       struct timespec       m_begin;
       char m_ctime[32];
};

实现：

snippet.cpp

ExecuteTimer::ExecuteTimer()
{
       memset(m_ctime, 0, sizeof(char)*32);
       //Reset the begin time.
       Reset();
}
 
ExecuteTimer::~ExecuteTimer()
{
}
 
char* ExecuteTimer::GetCTime()
{
       double lt = GetDTime();
       sprintf(m_ctime, "%.3fs", lt);
       return m_ctime;
}
 
double ExecuteTimer::GetDTime()
{
       struct timespec end;
       clock_gettime(CLOCK_REALTIME, &end);
       //trans. to second unit.
       double lt = (end.tv_sec - m_begin.tv_sec) + (end.tv_nsec - m_begin.tv_nsec) * 1.0e-9;
       return lt;
}
 
void ExecuteTimer::Reset()
{
       clock_gettime(CLOCK_REALTIME, &m_begin);
}
 
std::ostream& operator << (std::ostream& os, ExecuteTimer& obj)
{
       double lt = obj.GetDTime();
       //output formated string.
       char fmt[32] = {0};
       sprintf(fmt, "%.3fs", lt);
       os << fmt;
       return os;
}
 
std::ofstream& operator << (std::ofstream& ofs, ExecuteTimer& obj)
{
       double lt = obj.GetDTime();
       //output formated string.
       char fmt[32] = {0};
       sprintf(fmt, "%.3fs", lt);
       ofs << fmt;
       return ofs;
}