如何将wstring转换为字符串？ [英] How to convert wstring into string?

问题描述

问题是如何将wstring转换为字符串？

我有下面的例子：

  #include< string> 
 #include< iostream> 
 
 int main（）
 {
 std :: wstring ws = LHello; 
 std :: string s（w​​s.begin（），ws.end（））; 
 
 // std :: cout<<std :: string =<< s<< std :: endl; 
 std :: wcout<<std :: wstring =<< ws<< std :: endl; 
 std :: cout<<std :: string =<< s<< std :: endl; 
} 
  

带注释行的输出是：

  std :: string = Hello 
 std :: wstring = Hello 
 std :: string = Hello 
  

但不包含：

  std :: wstring = Hello 
  

示例中有什么问题吗？

新示例（采用）可以执行上面的转换。

<考虑一些答案）

  #include< string> 
 #include< iostream> 
 #include< sstream> 
 #include< locale> 
 
 int main（）
 {
 setlocale（LC_CTYPE，）; 
 
 const std :: wstring ws = LHello; 
 const std :: string s（w​​s.begin（），ws.end（））; 
 
 std :: cout<<std :: string =<< s<< std :: endl; 
 std :: wcout<<std :: wstring =<< ws<< std :: endl; 
 
 std :: stringstream ss; 
 ss<< ws.c_str（）; 
 std :: cout<<std :: stringstream =<< ss.str（）<< std :: endl; 
} 
  

输出为：

  std :: string = Hello 
 std :: wstring = Hello 
 std :: stringstream = 0x860283c 
  

因此，stringstream不能用于将wstring转换为字符串。

解决方案

这里是一个基于其他建议的解决方案：

  #include< string& 
 #include< iostream> 
 #include< clocale> 
 #include< locale> 
 #include< vector> 
 
 int main（）{
 std :: setlocale（LC_ALL，）; 
 const std :: wstring ws = Lħëłlö; 
 const std :: locale locale（）; 
 typedef std :: codecvt< wchar_t，char，std :: mbstate_t> converter_type; 
 const converter_type& converter = std :: use_facet< converter_type>（locale）; 
 std :: vector< char> to（ws.length（）* converter.max_length（））; 
 std :: mbstate_t state; 
 const wchar_t * from_next; 
 char * to_next; 
 const converter_type :: result result = converter.out（state，ws.data（），ws.data（）+ ws.length（），from_next，& to [0]，& to [0] + to.size（），to_next）; 
 if（result == converter_type :: ok或result == converter_type :: noconv）{
 const std :: string s（& to [0]，to_next）; 
 std :: cout<<std :: string =<< s<< std :: endl; 
} 
} 
  

这通常适用于Linux，在Windows上。

The question is how to convert wstring to string?

I have next example :

#include <string>
#include <iostream>

int main()
{
    std::wstring ws = L"Hello";
    std::string s( ws.begin(), ws.end() );

  //std::cout <<"std::string =     "<<s<<std::endl;
    std::wcout<<"std::wstring =    "<<ws<<std::endl;
    std::cout <<"std::string =     "<<s<<std::endl;
}

the output with commented out line is :

std::string =     Hello
std::wstring =    Hello
std::string =     Hello

but without is only :

std::wstring =    Hello

Is anything wrong in the example? Can I do the conversion like above?

EDIT

New example (taking into account some answers) is

#include <string>
#include <iostream>
#include <sstream>
#include <locale>

int main()
{
    setlocale(LC_CTYPE, "");

    const std::wstring ws = L"Hello";
    const std::string s( ws.begin(), ws.end() );

    std::cout<<"std::string =     "<<s<<std::endl;
    std::wcout<<"std::wstring =    "<<ws<<std::endl;

    std::stringstream ss;
    ss << ws.c_str();
    std::cout<<"std::stringstream =     "<<ss.str()<<std::endl;
}

The output is :

std::string =     Hello
std::wstring =    Hello
std::stringstream =     0x860283c

therefore the stringstream can not be used to convert wstring into string.

解决方案

Here is a worked-out solution based on the other suggestions:

#include <string>
#include <iostream>
#include <clocale>
#include <locale>
#include <vector>

int main() {
  std::setlocale(LC_ALL, "");
  const std::wstring ws = L"ħëłlö";
  const std::locale locale("");
  typedef std::codecvt<wchar_t, char, std::mbstate_t> converter_type;
  const converter_type& converter = std::use_facet<converter_type>(locale);
  std::vector<char> to(ws.length() * converter.max_length());
  std::mbstate_t state;
  const wchar_t* from_next;
  char* to_next;
  const converter_type::result result = converter.out(state, ws.data(), ws.data() + ws.length(), from_next, &to[0], &to[0] + to.size(), to_next);
  if (result == converter_type::ok or result == converter_type::noconv) {
    const std::string s(&to[0], to_next);
    std::cout <<"std::string =     "<<s<<std::endl;
  }
}

This will usually work for Linux, but will create problems on Windows.

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