Convert Platform::String to std::string

问题:

I am getting String^ which Contains some Indian language characters in a callback from C# Component in my C++ WinRT Component in a Cocos2dx game for Windows Phone 8 project.

Whenever I convert it to std::string the Hindi and other characters turn in to garbage characters. I'm not able to find why this is happening.

Here is a sample code and I have just defined Platform::String^ here but consider it's passed to C++ WinRT Component from C# Component

String^ str = L"विकास, વિકાસ, ਵਿਕਾਸ, Vikas";
std::wstring wsstr(str->Data());
std::string res(wsstr.begin(), wsstr.end());

回答1:

Edit: see this answer for a better portable solution.

The problem is that std::string only holds 8-bit character data and your Platform::String^ holds Unicode data. Windows provides functions WideCharToMultiByte and MultiByteToWideChar to convert back and forth:

std::string make_string(const std::wstring& wstring)
{
  auto wideData = wstring.c_str();
  int bufferSize = WideCharToMultiByte(CP_UTF8, 0, wideData, -1, nullptr, 0, NULL, NULL);
  auto utf8 = std::make_unique<char[]>(bufferSize);
  if (0 == WideCharToMultiByte(CP_UTF8, 0, wideData, -1, utf8.get(), bufferSize, NULL, NULL))
    throw std::exception("Can't convert string to UTF8");

  return std::string(utf8.get());
}

std::wstring make_wstring(const std::string& string)
{
  auto utf8Data = string.c_str();
  int bufferSize = MultiByteToWideChar(CP_UTF8, 0, utf8Data, -1, nullptr, 0);
  auto wide = std::make_unique<wchar_t[]>(bufferSize);
  if (0 == MultiByteToWideChar(CP_UTF8, 0, utf8Data, -1, wide.get(), bufferSize))
    throw std::exception("Can't convert string to Unicode");

  return std::wstring(wide.get());
}

void Test()
{
  Platform::String^ str = L"विकास, વિકાસ, ਵਿਕਾਸ, Vikas";
  std::wstring wsstr(str->Data());
  auto utf8Str = make_string(wsstr); // UTF8-encoded text
  wsstr = make_wstring(utf8Str); // same as original text
}

回答2:

With C++, you can convert from Platform::String to std::string with the following code:

Platform::String^ fooRT = "aoeu";
std::wstring fooW(fooRT->Begin());
std::string fooA(fooW.begin(), fooW.end());

Reference: How to convert Platform::String to char*?