BЈовић BЈовић - 4 days ago 5
C++ Question

How to convert wstring into string?

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.

Answer

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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