C指针原理(42)-c++-boost(日期时间)
boost库
时间类timer
#include <boost/timer.hpp>
#include <iostream>
using namespace boost;
using namespace std;
int main(){
timer t;
cout<<"最大测量时间:"<<t.elapsed_max()/3600<<"h"<<endl;
cout<<"最小测量时间:"<<t.elapsed_min()<<"s"<<endl;
int x=0;
for (int i=1;i<5000;i++){
x=i;
}
cout<<"程序启动后已经过去的时间"<<t.elapsed()<<"s"<<endl;
return 0;
}
dp@dp:~/boostlearn % CC -o mytest 2.cpp -I /home/dp/boost_1_55_0
dp@dp:~/boostlearn % ./mytest
最大测量时间:9320.68h
最小测量时间:0.0078125s
程序启动后已经过去的时间0.0078125s
麦好的AI乐园博客所有内容是原创，如果转载请注明来源
http://blog.csdn.net/myhaspl/
下面是timer类的内容
// boost timer.hpp header file ---------------------------------------------//
// Copyright Beman Dawes 1994-99. Distributed under the Boost
// Software License, Version 1.0. (See accompanying file
// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
// See http://www.boost.org/libs/timer for documentation.
// Revision History
// 01 Apr 01 Modified to use new <boost/limits.hpp> header. (JMaddock)
// 12 Jan 01 Change to inline implementation to allow use without library
// builds. See docs for more rationale. (Beman Dawes)
// 25 Sep 99 elapsed_max() and elapsed_min() added (John Maddock)
// 16 Jul 99 Second beta
// 6 Jul 99 Initial boost version
#ifndef BOOST_TIMER_HPP
#define BOOST_TIMER_HPP
#include <boost/config.hpp>
#include <ctime>
#include <boost/limits.hpp>
# ifdef BOOST_NO_STDC_NAMESPACE
namespace std { using ::clock_t; using ::clock; }
# endif
namespace boost {
// timer -------------------------------------------------------------------//
// A timer object measures elapsed time.
// It is recommended that implementations measure wall clock rather than CPU
// time since the intended use is performance measurement on systems where
// total elapsed time is more important than just process or CPU time.
// Warnings: The maximum measurable elapsed time may well be only 596.5+ hours
// due to implementation limitations. The accuracy of timings depends on the
// accuracy of timing information provided by the underlying platform, and
// this varies a great deal from platform to platform.
class timer
{
public:
timer() { _start_time = std::clock(); } // postcondition: elapsed()==0
// timer( const timer& src ); // post: elapsed()==src.elapsed()
// ~timer(){}
// timer& operator=( const timer& src ); // post: elapsed()==src.elapsed()
void restart() { _start_time = std::clock(); } // post: elapsed()==0
double elapsed() const // return elapsed time in seconds
{ return double(std::clock() - _start_time) / CLOCKS_PER_SEC; }
double elapsed_max() const // return estimated maximum value for elapsed()
// Portability warning: elapsed_max() may return too high a value on systems
// where std::clock_t overflows or resets at surprising values.
{
return (double((std::numeric_limits<std::clock_t>::max)())
- double(_start_time)) / double(CLOCKS_PER_SEC);
}
double elapsed_min() const // return minimum value for elapsed()
{ return double(1)/double(CLOCKS_PER_SEC); }
private:
std::clock_t _start_time;
}; // timer
} // namespace boost
#endif // BOOST_TIMER_HPP
从上面timer类的内容可看出：
1、该类有一个私有变量保存了启动时间，在类实例化同时对其私有成员代表的启动时间赋初值：
private:
std::clock_t _start_time;
在timer()构造函数中，进行赋值。_start_time = std::clock();
void restart() { _start_time = std::clock(); }
2、elapsed计算了当前时间与启动时间的差额，同时可以看到时间由标准库的clock函数获得：
double elapsed() const // return elapsed time in seconds
{ return double(std::clock() - _start_time) / CLOCKS_PER_SEC; }
3、gregorian库
日期时间还可以使用gregorian库
boost::gregorian::date类是日期程序的接口，可如下引用该库：
#include "boost/date_time/gregorian/gregorian.hpp"
date可构造日期，常用构造函数：
date(greg_year, greg_month, greg_day)
比如：date d(2002,Jan,10);
date(date d)
比如：date d1(d);
也可从字符串构造
date from_string(std::string)
比如：
std::string ds("2002/1/25");
date d(from_string(ds));
也可以使用没有分隔符的字符串：
date from_undelimited_string(std::string)
比如：
std::string ds("20020125");
date d(from_undelimited_string(ds));
date_duration可完成日期的计算，表示日期间隔
常用构造函数：
date_duration(long)
比如：date_duration dd(6); //6天
days dd5(min_date_time);
下面是个例子
dp@dp:~/boost_1_55_0/boost % vim 3.cpp
#include <iostream>
#include "boost/date_time/gregorian/gregorian.hpp"
using namespace std;
using namespace boost::gregorian;
int main(){
date d1(2013,06,01);
date d2(2013,12,31);
date_duration dd = d2-d1+date_duration(1);
cout<<"2013年下半年共"<<dd<<"天"<<endl;
return 0;
}
dp@dp:~/boost_1_55_0/boost % CC -o mytest 3.cpp -I /home/dp/boost_1_55_0
dp@dp:~/boost_1_55_0/boost % ./mytest
2013年下半年共214天
dp@dp:~/boost_1_55_0/boost %