LPWSTR to wstring c++

Question

I would like to read utf-8 test from a .dll string table. something like this

LPWSTR nnW;
LoadStringW(hMod, id, nnW, MAX_PATH);

and after that I would like to convert the LPWSTR nnW to std::wstring nnWstring. I tried in this way: LPWSTR nnW; LoadStringW(hMod, id, nnW, MAX_PATH);

const int length = MultiByteToWideChar(CP_UTF8,
                                       0,   // no flags required
                                       (LPCSTR)nnW,
                                       -1,  // automatically determine length
                                       NULL,
                                       0);

std::wstring nnWstring(length, L'\0');

if (!MultiByteToWideChar(CP_UTF8,
                         0,
                         (LPCSTR)nnW,
                         -1,
                         &nnWstring[0],
                         length))

MessageBoxW(NULL, (LPCWSTR)nnWstring.c_str(),  L"wstring", MB_OK | MB_ICONERROR);

After that in the MessageBoxW only shows the first letter.

Answer 1

No conversion or copying needed.

std::wstring nnWString(MAX_PATH, 0);
nnWString.resize(LoadStringW(hMod, id, &nnWString[0], nnWString.size());

Note: Your original code causes undefined behavior, because it writes using an uninitialized pointer. Surely not what you wanted.

Here's another variation:

• http://msmvps.com/blogs/gdicanio/archive/2010/01/05/stl-strings-loading-from-resources.aspx

Answer 2

I would like to read utf-8 test from a .dll string table. something like this

Generally, string tables in Windows are UTF-16. You're trying to put UTF-8 data into one. The UTF-8 data is being treated like "extended" ASCII, so each byte is being expanded to two bytes with zero bytes between them.

You should probably put UTF-16 data in the string table directly.

If you must store UTF-8 data in the resources, you can put it into an RCDATA resource and use the lower-level resource functions to get the data out. Then you'll have to convert from UTF-8 to UTF-16 to store it in a wstring.