boost学习2.4：progress_diplay

progress_diplay可以在显示台显示程序执行的进度。

（1）类摘要

#include "stdafx.h"
#include<stdlib.h>
#include <vector>
#include<iostream>
#include <fstream>
#include <boost/progress.hpp>
using namespace std;
using namespace boost;
class progress_display : private noncopyable//noncopyable子类可以继承，但是禁止拷贝（即只能单例化）
{
public://explicit关键字，表示不能发生隐式转换
    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
        : 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)/_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
};

（2）用法

#include "stdafx.h"
#include<stdlib.h>
#include <vector>
#include<iostream>
#include <fstream>
#include <boost/progress.hpp>
using namespace std;
using namespace boost;
int _tmain(int argc, _TCHAR* argv[])
{
    vector<string> v(100);
    for (vector<string>::iterator& i=v.begin();i!=v.end();i++)
    {
        *i="asd";
    }

    ofstream fs("./test.txt");//打开一个文件输出流，记得包含fstrean头文件
    progress_display pd(v.size());//实例化一个显示类的基数（即进度条里最多的个数作为分母）
    for(vector<string>::iterator& x=v.begin();x!=v.end();x++)
    {
        fs<<*x<<endl;//想test写入文件
        ++pd;//更新进度条
    }
    return 0;
}

 3.注意事项

当我们想显示进度的同时还可以显示中间的一些空字符行号，当我们下面这样做时

int _tmain(int argc, _TCHAR* argv[])
{
    vector<string> v(100,"aaa");
    v[10]="";
    v[23]="";

    ofstream fs("./test.txt");//打开一个文件输出流，记得包含fstrean头文件
    progress_display pd(v.size());//实例化一个显示类的基数（即进度条里最多的个数作为分母）
    for(vector<string>::iterator& x=v.begin();x!=v.end();x++)
    {
        fs<<*x<<endl;//想test写入文件
        ++pd;//更新进度条
        if(x->empty())
        {
            cout<<"null string #"<<(x-v.begin());
        }
    }
    return 0;
}

当我们按上面这样做时会发现：

这样会打乱我们们进度条的显示：

所以我们只能下面这样做：

// test1.cpp : 定义控制台应用程序的入口点。
//
#include "stdafx.h"
#include<stdlib.h>
#include <vector>
#include<iostream>
#include <fstream>
#include <boost/progress.hpp>
using namespace std;
using namespace boost;

int _tmain(int argc, _TCHAR* argv[])
{
    vector<string> v(100,"aaa");
    v[10]="";
    v[23]="";

    ofstream fs("./test.txt");//打开一个文件输出流，记得包含fstrean头文件
    progress_display pd(v.size());//实例化一个显示类的基数（即进度条里最多的个数作为分母）
    for(vector<string>::iterator& x=v.begin();x!=v.end();x++)
    {
        fs<<*x<<endl;//想test写入文件
        ++pd;//更新进度条
        if(x->empty())
        {
            cout<<"null string #"<<(x-v.begin());
            pd.restart(v.size());//将pd重新设置到开始
            pd+=(x-v.begin()+1);//同时再将进度显示到我们需要显示的那
        }
    }
    return 0;
}

结果：