Encoding conversion in C++

string-conversion.cpp

// Convert a wide Unicode string to an ANSI string.
std::string unicodeToAnsi(const std::wstring &wstr) {
  int bufSize = WideCharToMultiByte(CP_ACP, 0, &wstr[0], -1, NULL, 0, NULL, NULL);
  std::string strTo(bufSize, 0);
  WideCharToMultiByte(CP_ACP, 0, &wstr[0], (int)wstr.size(), &strTo[0], bufSize, NULL, NULL);
  return strTo;
}

// Convert a wide Unicode string to an UTF8 string.
std::string unicodeToUtf8(const std::wstring &wstr) {
  int bufSize = WideCharToMultiByte(CP_UTF8, 0, &wstr[0], (int)wstr.size(), NULL, 0, NULL, NULL);
  std::string strTo(bufSize, 0);
  WideCharToMultiByte(CP_UTF8, 0, &wstr[0], (int)wstr.size(), &strTo[0], bufSize, NULL, NULL);
  return strTo;
}

// Convert a UTF8 string to a wide Unicode string.
std::wstring utf8ToUnicode(const std::string &str) {
  int bufSize = MultiByteToWideChar(CP_UTF8, 0, &str[0], (int)str.size(), NULL, 0);
  std::wstring wstrTo(bufSize, 0);
  MultiByteToWideChar(CP_UTF8, 0, &str[0], (int)str.size(), &wstrTo[0], bufSize);
  return wstrTo;
}

// Convert a UTF-8 string to an ANSI string.
std::string WINAPI utf8ToAnsi(const std::string &str) {
  return unicodeToAnsi(utf8ToUnicode(str));
}

// Convert an ANSI string to a wide Unicode (UTF-16) string.
std::wstring ansiToUnicode(const std::string &str) {
  int bufSize = MultiByteToWideChar(CP_ACP, 0, &str[0], (int)str.size(), NULL, 0);
  std::wstring wstrTo(bufSize, 0);
  MultiByteToWideChar(CP_ACP, 0, &str[0], (int)str.size(), &wstrTo[0], bufSize);
  return wstrTo;
}

// Convert an ANSI string to a UTF-8 string.
std::string WINAPI ansiToUtf8(const std::string &str) {
  return unicodeToUtf8(ansiToUnicode(str));
}