std::string to const WCHAR*

David Crow

The c_str() method is a member of both string and wstring. Is that what you are asking?

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Stick

ummm seems that would do the reverse of what I want. I want to go to a wide string from a cstr.

Stick

Don't think I can use ATL and not sure how I would do that anyway yet. I'm programming a win32 dll.

Stick

Would if I could, but I am given a c_str and must convert it to a wide, hence the question.

James R Twine

No, I am verifying that even though he is using std::string (ANSI) instead of std::wstring (Unicode/Wide), he can still expect to get a const WCHAR* returned by std::string::c_str()? I am under the impression that he will get a const **char*** from std::string::c_str(), and a const **WCHAR*** (or const wchar_t*) from std::**w**string::c_str(). Peace!

-=- James

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James R Twine

You can use the conversion macros without adding "real" ATL support to your project. Anyway, MultiByteToWideChar(...) is likely the way to go - look it up in MSDN for usage info. Peace!

-=- James

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David Crow

Because string.c_str() returns a char* is why I indicated it would need to be a minimum. A typecast would still need to be applied (to make it wide). I don't use the STL, but a better solution would be to use wstring instead.

"Approved Workmen Are Not Ashamed" - 2 Timothy 2:15

"Judge not by the eye but by the heart." - Native American Proverb

David Crow

As I do not use the STL, I did not want to commit to a definite solution. That's why I prefaced it with, "At a minimum." From there you could have just cast it to a WCHAR*. A better solution is to use a wstring instead.

"Approved Workmen Are Not Ashamed" - 2 Timothy 2:15

"Judge not by the eye but by the heart." - Native American Proverb

David Crow

Stick^ wrote:

Would if I could, but I am given a c_str and must convert it to a wide, hence the question.

c_str() is a method of wstring. No conversion is necessary as it is already "wide." Now if you are unable to change std::string to std::wstring, that's a different problem.

"Approved Workmen Are Not Ashamed" - 2 Timothy 2:15

"Judge not by the eye but by the heart." - Native American Proverb

Zac Howland

You are given a const char* you mean? If that is the case, use MultiByteToWideChar to convert the const char* to an array of const wchar_t* and pass that to your draw function (NOTE: that will only work for UNICODE builds -- for a more generic approach, look at the A2T macro)

If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week Zac

Stick

No. I'm given a std::string... here's the declaration: string m_ac; Now, if I attempt: m_graphics->DrawString(m_ac, -1, &font, PointF(8,8), NULL, &grnbrush); I get: Error 1 error C2664: 'Gdiplus::Status Gdiplus::Graphics::DrawString(const WCHAR *,INT,const Gdiplus::Font *,const Gdiplus::RectF &,const Gdiplus::StringFormat *,const Gdiplus::Brush *)' : cannot convert parameter 1 from 'std::string' to 'const WCHAR *' so as you can clearly see, the m_ac is NOT already wide. I have tried to do something like this: WCHAR str[20+1] = L""; WideCharToMultiByte(CP_ACP, 0, m_ac.c_str(), -1, str, wcslen(str)+1, NULL, NULL); but this does not work either. Nor does just m_ac in parameter 3.

James R Twine

The const char* returned by c_str() is not a wide string, while casting it to WCHAR* will allow the code to compile, it will not work correctly. Peace!

-=- James

If you think it costs a lot to do it right, just wait until you find out how much it costs to do it wrong!
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Jorgen Sigvardsson

James R. Twine wrote:

while casting it to WCHAR* will allow the code to compile, it will not work correctly.

From the context, I think he meant casting the entire string, and not the pointer. :)

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George L Jackson

Have you tried "mbstowcs" or "mbstowcs_s" in stdlib.h. std::string mbstr = "The string!"; std::vector<wchar_t> wcstr(mbstr.size() + 1, L'\0'); size_t written = 0; mbstate_t state = {0}; const char* pmbstr = mbstr.c_str(); errno_t result = mbsrtowcs_s(&written, &wcstr[0], wcstr.size(), &pmbstr, mbstr.size(), &state); std::wcout << &wcstr[0] << std::endl; -- modified at 20:19 Thursday 28th September, 2006

James R Twine

You mean to create a temporary, as in wstring( sTheString.c_str() )? I do not think that will work, either... Unless I am missing the intent of your smiley, that is. Peace!

-=- James

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Jorgen Sigvardsson

Naw, more likely using CA2CW or something along those lines. My bet's on that David's a bit too experienced to fall for the (wchar_t*)str.c_str() and similar newbie mistakes. :)

Jorgen Sigvardsson

If you are using a fairly new version of MFC (7, 8), you can use the conversion classes such as CA2W without any hassles. Just include atlconv.h in stdafx.h, and you're set.

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Jorgen Sigvardsson

Stick^ wrote:

WideCharToMultiByte(CP_ACP, 0, m_ac.c_str(), -1, str, wcslen(str)+1, NULL, NULL);

Please use MultiByteToWideChar() instead. You are converting from char to wchar_t, right?

wchar_t buf[20+1] = { 0 };
MultiByteToWideChar(CP_ACP, MB_PRECOMPOSED, m_ac.c_str(), m_ac.size(), buf, 20);

should do the trick.

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David Crow

James R. Twine wrote:

The const char* returned by c_str() is not a wide string,...

So what exactly does std::wstring::c_str() return?

"Approved Workmen Are Not Ashamed" - 2 Timothy 2:15

"Judge not by the eye but by the heart." - Native American Proverb

James R Twine

std::**w**string::c_str() returns a const WCHAR* (const wchar_t*), but not std::string:c_str(), which is what the OP was asking about. I think that we (I?) are just getting confused about what "width" of string object is in use here. The OP is dealing with having a std::string (ANSI) object and needs to get a (presumably valid) const WCHAR* (Unicode) out of it. Since they cannot simply change the strings from std::string to std::wstring, they are stuck with ANSI string objects, and no amount of casting is going to create a valid wide string from the return of std::string:c_str(). They need to call a conversion function (either directly or indirectly) in order to translate the string correctly. Peace!

-=- James

If you think it costs a lot to do it right, just wait until you find out how much it costs to do it wrong!
Avoid driving a vehicle taller than you and remember that Professional Driver on Closed Course does not mean your Dumb Ass on a Public Road!
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