《Boost程序完全开发》跟踪学习训练一：Boost::date_time库的使用

主要是记录个人如何按照Boost程序完全开发一书去学习入门Boost库

书中第一个是date_time库首先我们看一下怎么去用

#include <boost\timer.hpp>#include <boost\progress.hpp>#include <iostream>#include "mytimer.h"using namespace boost;void main1(){boost::timer t;std::cout<< "max span" << t.elapsed_max() / 3600 << "h" << std::endl;std::cout << "time espaced" << t.elapsed() << "S" << std::endl;shao::mytimer mytime;std::cout << "mytime spend " << mytime.time_spend() << "S" << std::endl;system("pause");}void test(){boost::progress_timer time;}void main2(){test();std::cin.get();}

看一下boost::timer的实现还是简单的

//  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; }# endifnamespace 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

下面就是boost::progress_display进度条的显示

使用案例

#include <boost\progress.hpp>#include <fstream>#include <vector>using namespace boost;using namespace std;void main(){std::vector<string> myvec(100);//文件输出流ofstream outFile("D:\\shao.txt");progress_display progress(myvec.size(),std::cout);vector<string>::iterator myit = myvec.begin();for(;myit != myvec.end();myit++){outFile << *myit << endl;++progress;}std::cin.get();} 

下面我们看一下progress_display的源码呢

class progress_display : private noncopyable{ public:  //构造函数需要进度条的最大值 和 输出流 默认是控制台  explicit progress_display( unsigned long expected_count,                             std::ostream & os = std::cout,                             const std::string & s1 = "\n", //leading strings                             const std::string & s2 = "",                             const std::string & s3 = "" )   : noncopyable(), m_os(os), m_s1(s1), m_s2(s2), m_s3(s3) { restart(expected_count); }  void           restart( unsigned long expected_count )  {    _count = _next_tic_count = _tic = 0;    _expected_count = expected_count;    m_os << m_s1 << "0%   10   20   30   40   50   60   70   80   90   100%\n"         << m_s2 << "|----|----|----|----|----|----|----|----|----|----|"         << std::endl  // endl implies flush, which ensures display         << m_s3;    if ( !_expected_count ) _expected_count = 1;  // prevent divide by zero  } // restart  //重载+=方法  unsigned long  operator+=( unsigned long increment )  {    if ( (_count += increment) >= _next_tic_count ) { display_tic(); }    return _count;  }  //重载 ++方法 进度+1  unsigned long  operator++()           { return operator+=( 1 ); }  unsigned long  count() const          { return _count; }  unsigned long  expected_count() const { return _expected_count; }  private:  std::ostream &     m_os;  // may not be present in all imps  const std::string  m_s1;  // string is more general, safer than   const std::string  m_s2;  //  const char *, and efficiency or size are  const std::string  m_s3;  //  not issues  unsigned long _count, _expected_count, _next_tic_count;  unsigned int  _tic;  void display_tic()  {      unsigned int tics_needed =      static_cast<unsigned int>(        (static_cast<double>(_count)/_expected_count)*50.0 );    do { m_os << '*' << std::flush; } while ( ++_tic < tics_needed );    _next_tic_count =       static_cast<unsigned long>((_tic/50.0)*_expected_count);    if ( _count == _expected_count ) {      if ( _tic < 51 ) m_os << '*';      m_os << std::endl;      }  } // display_tic};

到这进度 计时的类库还是比较简单的 算是入门第一篇吧 作者讲解的挺好 有点缺点都会暴露出来