c++ boost progress_display

快来打我* 2022-06-02 00:21 139阅读 0赞

progress\_display可以在控制台程序中显示程序的执行进度，如果程序执行很耗费时间，那么它能够提供一个良好的等待界面。

命名空间：boost

头文件：\#include

class progress_display : private noncopyable
    {
     public:
      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 = "" )
       // os is hint; implementation may ignore, particularly in embedded systems
       : noncopyable(), m_os(os), m_s1(s1), m_s2(s2), m_s3(s3) { restart(expected_count_); }
    
      void           restart( unsigned long expected_count_ )
      // Effects: display appropriate scale
      // Postconditions: count()==0, expected_count()==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
    
      unsigned long  operator+=( unsigned long increment )
      // Effects: Display appropriate progress tic if needed.
      // Postconditions: count()== original count() + increment
      // Returns: count().
      {
        if ( (_count += increment) >= _next_tic_count ) { display_tic(); }
        return _count;
      }
    
      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()
      {
        // use of floating point ensures that both large and small counts
        // work correctly. static_cast<>() is also used several places
        // to suppress spurious compiler warnings. 
        unsigned int tics_needed = static_cast<unsigned int>((static_cast<double>(_count)
            / static_cast<double>(_expected_count)) * 50.0);
        do { m_os << '*' << std::flush; } while ( ++_tic < tics_needed );
        _next_tic_count = 
          static_cast<unsigned long>((_tic/50.0) * static_cast<double>(_expected_count));
        if ( _count == _expected_count ) {
          if ( _tic < 51 ) m_os << '*';
          m_os << std::endl;
          }
      } // display_tic
    };

实例：

#include <boost\progress.hpp>
    #include <vector>
    #include <string>
    #include <fstream>
    using namespace std;
    int main()
    {
    
        vector<string> v(100000,"adbddddeed");
    
        boost::progress_display display(v.size());
    
        vector<string>::iterator pos;
    
        ofstream out("a.txt");
        for (pos = v.begin(); pos != v.end(); ++pos)
        {
            out << *pos <<"\n" << endl;
            ++display;
        }
        return 0;
    }

在这里我向文件中写内容，然后等待完成。这里将vector的内容设置的很大，避免程序运行就完成了，这样就看不到效果了。。程序运行截图：  
![这里写图片描述][SouthEast]

如果progress\_display构造函数中设定的expected\_count\_和你在for循环中循环次数不一致，这里会出现问题的。。  
在这里我将expected\_count\_设置为100，其他的不变，输出如下：  
![这里写图片描述][SouthEast 1]

同时我们还需要注意到，输出是控制台中的io流，我们没办法确定什么时候还会有内容输出到输出流中去，我们在上面的代码中修改以下，看下运行结果：

for (pos = v.begin(); pos != v.end(); ++pos)
        {
            out << *pos << endl;
            cout << "hello" << endl;
            ++display;
        }

![这里写图片描述][SouthEast 2]

可以看到两者都不知道彼此的存在，各顾各的拼命往标准输出中打印。。此时输出结果就变得混乱了。。

一种相对好看点的解决方法是，每次通过restart方法重新启动计时器，并且通过(+=)重载操作符设定当前刻度。

for (pos = v.begin(); pos != v.end(); ++pos)
        {
            out << *pos << endl;
            cout << "hello" << endl;
            display.restart(v.size());
            display += pos - v.begin() +1;
            cout << endl;
        }

![这里写图片描述][SouthEast 3]

[SouthEast]: /images/20220602/da27c66500254144a157338e881bfa56.png
[SouthEast 1]: /images/20220602/6e6a24af33274d919fae2b236bdfadd3.png
[SouthEast 2]: /images/20220602/1a43d3366d204a088988f3fac6ba0113.png
[SouthEast 3]: /images/20220602/ce3116b193e94687ae1ec62895426e55.png