I am aware that std::string and std::wstring come from the same base type std::basic_string<>. But there isn't an "official" way to convert std::string data to std::wstring using the C++ STL? I mean Windows provide MultiByteToWideChar() to convert but why cant the STL provide one?
I used std::codecvt before to get it done but now it says that it is deprecated. Why does the STL remove this support the first place?
Thanks in advance.
The character encoding of std::string is not defined by the C++ standard, a std::string can hold any encoding that can be represented using 1-byte char elements, which includes UTF-7/8, ISO-8859-x, Windows-125x, etc.
Also, the size of wchar_t is implementation-defined, not defined by the standard, so even the encoding of std::wstring can vary, too. On Windows, wchar_t is 2 bytes, so std::wstring uses UCS-2/UTF-16 encoding. Whereas on other platforms, wchar_t is 4 bytes, so std::wstring uses UCS-4/UTF-32.
So, there is no single conversion that satisfies all possible combinations of std::string <-> std::wstring conversions across all platforms and use-cases. So, you need to know the encoding of the source string, and the intended encoding of the target string, in order to perform a conversion.
And yes, the C++ standard did provide std::codecvt and std::wstring_convert/std::wbuffer_convert for this task, but they have been deprecated, as you have noted. There is no standard replacement provided (yet?).
So, you are best off using 3rd party Unicode API/libraries to handle character conversions.
