c++ - How to convert wchar_t* to std::string?

C++ - How to convert wchar_t* to std::string?

To convert a wchar_t* (wide character string) to std::string (narrow character string) in C++, you'll need to perform a wide-to-narrow conversion. This is because wchar_t represents wide characters (typically UTF-16 or UTF-32), while std::string represents narrow characters (usually UTF-8 or ASCII).

Here's a step-by-step guide to perform this conversion using C++ standard libraries:

Using std::wstring_convert (C++11 and C++14)

If you're using C++11 or C++14, you can use the std::wstring_convert with std::codecvt facet. However, note that std::wstring_convert and std::codecvt are deprecated in C++17 and removed in C++20.

Here's how you can use it:

#include <iostream> #include <string> #include <locale> #include <codecvt> std::string WideToNarrow(const std::wstring& wstr) { std::wstring_convert<std::codecvt_utf8<wchar_t>> converter; return converter.to_bytes(wstr); } int main() { const wchar_t* wideStr = L"Hello, World!"; std::wstring wstr(wideStr); std::string narrowStr = WideToNarrow(wstr); std::cout << "Converted string: " << narrowStr << std::endl; return 0; }

Using std::wstring_convert with std::wstring to std::string Conversion (C++17 or later)

Since std::wstring_convert is deprecated, a more modern approach is to use the std::wstring to std::string conversion with std::wcout and std::cout:

#include <iostream> #include <string> #include <locale> #include <codecvt> // Function to convert wchar_t* to std::string std::string WideToNarrow(const wchar_t* wideStr) { std::wstring wstr(wideStr); std::wstring_convert<std::codecvt_utf8<wchar_t>> converter; return converter.to_bytes(wstr); } int main() { const wchar_t* wideStr = L"Hello, World!"; std::string narrowStr = WideToNarrow(wideStr); std::cout << "Converted string: " << narrowStr << std::endl; return 0; }

Using std::wstring_convert with Custom Conversion Functions (C++20)

If you're using C++20 or later and std::wstring_convert is not available, you can manually convert the wide string using the std::wstring and UTF-8 conversion:

#include <iostream> #include <string> #include <locale> #include <codecvt> // Function to convert wchar_t* to std::string std::string WideToNarrow(const std::wstring& wstr) { std::string narrowStr; std::locale loc(""); const std::ctype<wchar_t>& ctype = std::use_facet<std::ctype<wchar_t>>(loc); for (const wchar_t& wc : wstr) { char c[MB_CUR_MAX]; ctype.widen(wc, c); narrowStr += c; } return narrowStr; } int main() { const wchar_t* wideStr = L"Hello, World!"; std::wstring wstr(wideStr); std::string narrowStr = WideToNarrow(wstr); std::cout << "Converted string: " << narrowStr << std::endl; return 0; }

Summary

  1. C++11/14: Use std::wstring_convert with std::codecvt_utf8<wchar_t>.
  2. C++17 and later: Consider using the std::wstring conversion functions or manual conversion methods as shown.
  3. C++20: Manual conversion using facets or other conversion libraries.

Choose the method based on your C++ standard and the requirements of your application.

Examples

  1. "Convert wchar_t* to std::string using std::wstring_convert"

    • Description: Use the deprecated std::wstring_convert class to convert wchar_t* to std::string.
    • Code:
      #include <string> #include <locale> #include <codecvt> std::string wcharToString(const wchar_t* wcharStr) { std::wstring_convert<std::codecvt_utf8<wchar_t>> converter; return converter.to_bytes(wcharStr); }

  2. "Convert wchar_t* to std::string using WideCharToMultiByte"

    • Description: Utilize the Windows API function WideCharToMultiByte for conversion.
    • Code:
      #include <windows.h> #include <string> std::string wcharToString(const wchar_t* wcharStr) { int size = WideCharToMultiByte(CP_UTF8, 0, wcharStr, -1, NULL, 0, NULL, NULL); std::string str(size, 0); WideCharToMultiByte(CP_UTF8, 0, wcharStr, -1, &str[0], size, NULL, NULL); return str; }

  3. "Convert wchar_t* to std::string using std::wstring and std::string constructors"

    • Description: Convert wchar_t* to std::wstring, then use the std::string constructor.
    • Code:
      #include <string> std::string wcharToString(const wchar_t* wcharStr) { std::wstring wstr(wcharStr); return std::string(wstr.begin(), wstr.end()); }

  4. "Convert wchar_t* to std::string using std::wstring_convert with custom facet"

    • Description: Use std::wstring_convert with a custom codecvt facet to convert wchar_t* to std::string.
    • Code:
      #include <string> #include <locale> #include <codecvt> std::string wcharToString(const wchar_t* wcharStr) { std::wstring_convert<std::codecvt_utf8<wchar_t>> converter; return converter.to_bytes(wcharStr); }

  5. "Convert wchar_t* to std::string using std::mbstowcs and std::wcstombs"

    • Description: Use the C standard library functions for conversion.
    • Code:
      #include <string> #include <cstdlib> std::string wcharToString(const wchar_t* wcharStr) { size_t len = wcstombs(NULL, wcharStr, 0); std::string str(len, '\0'); wcstombs(&str[0], wcharStr, len); return str; }

  6. "Convert wchar_t* to std::string with UTF-8 encoding using iconv"

    • Description: Use the iconv library for converting wchar_t* to UTF-8 encoded std::string.
    • Code:
      #include <iconv.h> #include <string> #include <vector> std::string wcharToString(const wchar_t* wcharStr) { iconv_t cd = iconv_open("UTF-8", "WCHAR_T"); if (cd == (iconv_t)-1) return ""; size_t inBytes = wcslen(wcharStr) * sizeof(wchar_t); size_t outBytes = inBytes * 4; // UTF-8 may expand to 4 bytes std::vector<char> buffer(outBytes); char* inBuf = (char*)wcharStr; char* outBuf = buffer.data(); iconv(cd, &inBuf, &inBytes, &outBuf, &outBytes); iconv_close(cd); return std::string(buffer.data(), buffer.size() - outBytes); }

  7. "Convert wchar_t* to std::string using std::wstring::c_str and std::string constructor"

    • Description: First convert wchar_t* to std::wstring and then use the std::string constructor to convert it.
    • Code:
      #include <string> std::string wcharToString(const wchar_t* wcharStr) { std::wstring wstr(wcharStr); return std::string(wstr.c_str(), wstr.size()); }

  8. "Convert wchar_t* to std::string with error handling using std::wstring_convert"

    • Description: Handle potential errors during the conversion process with std::wstring_convert.
    • Code:
      #include <string> #include <locale> #include <codecvt> std::string wcharToString(const wchar_t* wcharStr) { try { std::wstring_convert<std::codecvt_utf8<wchar_t>> converter; return converter.to_bytes(wcharStr); } catch (...) { // Handle conversion error return ""; } }

  9. "Convert wchar_t* to std::string using Boost.Locale library"

    • Description: Utilize Boost.Locale for conversion from wchar_t* to std::string.
    • Code:
      #include <boost/locale.hpp> #include <string> std::string wcharToString(const wchar_t* wcharStr) { return boost::locale::conv::utf_to_utf<char>(wcharStr); }

  10. "Convert wchar_t* to std::string using custom conversion function with std::ostringstream"

    • Description: Create a custom function for converting wchar_t* to std::string using std::ostringstream.
    • Code:
      #include <string> #include <sstream> #include <locale> std::string wcharToString(const wchar_t* wcharStr) { std::wstringstream wss; wss.imbue(std::locale("en_US.UTF-8")); wss << wcharStr; std::string str = wss.str(); return str; }

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