Encoding conversion in C++

string-conversion.cpp

// Convert a UTF-16 string to an ANSI string.
std::string utf16ToAnsi(const std::wstring &wstr) {
  size_type length = wstr.size();
  int bufSize = WideCharToMultiByte(CP_ACP, WC_COMPOSITECHECK, &wstr[0], length, NULL, 0, NULL, NULL);
  std::string strTo(bufSize + 1, 0);
  WideCharToMultiByte(CP_ACP, WC_COMPOSITECHECK, &wstr[0], length, &strTo[0], bufSize, NULL, NULL);
  return strTo;
}

// Convert a UTF-16 string to an UTF-8 string.
std::string utf16ToUtf8(const std::wstring &wstr) {
  size_type length = wstr.size();
  int bufSize = WideCharToMultiByte(CP_UTF8, WC_COMPOSITECHECK, &wstr[0], length, NULL, 0, NULL, NULL);
  std::string strTo(bufSize + 1, 0);
  WideCharToMultiByte(CP_UTF8, WC_COMPOSITECHECK, &wstr[0], length, &strTo[0], bufSize, NULL, NULL);
  return strTo;
}

// Convert a UTF-8 string to a UTF-16 string.
std::wstring utf8ToUtf16(const std::string &str) {
  size_type length = str.size();
  int bufSize = MultiByteToWideChar(CP_UTF8, 0, &str[0], length, NULL, 0);
  std::wstring wstrTo(bufSize + 1, 0);
  MultiByteToWideChar(CP_UTF8, 0, &str[0], length, &wstrTo[0], bufSize);
  return wstrTo;
}

// Convert a UTF-8 string to an ANSI string.
std::string WINAPI utf8ToAnsi(const std::string &str) {
  return utf16ToAnsi(utf8ToUtf16(str));
}

// Convert an ANSI string to a UTF-16 string.
std::wstring ansiToUtf16(const std::string &str) {
  size_type length = str.size();
  int bufSize = MultiByteToWideChar(CP_ACP, 0, &str[0], length, NULL, 0);
  std::wstring wstrTo(bufSize + 1, 0);
  MultiByteToWideChar(CP_ACP, 0, &str[0], length, &wstrTo[0], bufSize);
  return wstrTo;
}

// Convert an ANSI string to a UTF-8 string.
std::string WINAPI ansiToUtf8(const std::string &str) {
  return utf16ToUtf8(ansiToUtf16(str));
}