How do I convert from a wchar_t* to a wstring?

Question

Or how to I initialize a wstring using a wchar_t*?

I tried something like this, but it's not quite working. I'm given an LPVOID and it points to a wchar_t pointer. I just want to get it into a wstring so I can use some normal string functions on it.

LPVOID lpOutBuffer = NULL;
//later in code this is initialized this way
lpOutBuffer = new WCHAR[dwSize/sizeof(WCHAR)];
//fills up the buffer
doStuff(lpOutBuffer, &dwSize);
//try to convert it to a wstring
wchar_t* t =  (wchar_t*)lpOutBuffer;
wstring responseHeaders = wstring(t);

printf("This prints response headers: \n%S", t);
printf("This prints nothing: \n%S", responseHeaders);

doStuff is really a call to WinHttpQueryHeaders I just changed it to make it easier to understand my example.

Should work - `wstring` has a constructor for that. What do you get? Also, is the buffer null-terminated? — Seva Alekseyev, Jan 18 '12 at 19:34
I updated the code with what's happening to initialize the pointer. I'm new to c++ so I'm still wrapping my head around pointers and such. I don't know if the the wchar_t is null terminated. I'm calling the WinHttpQueryHeaders Funtion - http://msdn.microsoft.com/en-us/library/windows/desktop/aa384102(v=vs.85).aspx I couldn't tell if it was null terminating the buffer. — ScArcher2, Jan 18 '12 at 19:40
@DrewDormann The responseHeaders wstring is empty when i attempt to print it out. If I print the wchar_t it prints out what I expect. — ScArcher2, Jan 18 '12 at 19:44

Drew Dormann · Answer 1 · 2012-01-18T19:48:06.803

4

If the LPVOID points to a wchar_t pointer as you say, your level of indirection is wrong.

LPVOID lpOutBuffer;
wchar_t** t =  (wchar_t**)lpOutBuffer;
wstring responseHeaders = wstring(*t);

Edit: Question has changed. This answer no longer applies.

edited Jan 18 '12 at 19:48

answered Jan 18 '12 at 19:36

Drew Dormann

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I believe I misspoke I corrected my example, since I don't know what I'm talking about :) – ScArcher2 Jan 18 '12 at 19:44

score 4 · Accepted Answer · answered Jan 18 '12 at 19:54

4

Passing the wstring object to printf is not going to work. Rephrase the second prinf line as

printf("This prints nothing: \n%S", responseHeaders.c_str());

c_str() gives you a const pointer to the underlying string data.

answered Jan 18 '12 at 19:54

Seva Alekseyev

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This is where my problem was. Thank you! – ScArcher2 Jan 18 '12 at 19:56
@ScArcher2 You should see if your compiler has printf format checking so you can avoid this error. – bames53 Jan 18 '12 at 20:05
1

Reference to WinHttpQueryHeaders suggests Visual C++. It does not. – Seva Alekseyev Jan 18 '12 at 20:07
@SevaAlekseyev is correct. I'm using Visual Studio. At least now I know to check the type I'm passing to printf. Thanks again! – ScArcher2 Jan 18 '12 at 20:13

score 0 · Answer 3 · edited Jan 15 '23 at 11:12

0

Again, too complicated. Just do this:

std::wstring TheNewWideString = std::wstring(TheOldWideCharacterTPointer);

It works directly for me on Microsoft Windows with C++11 and CodeBlocks.

edited Jan 15 '23 at 11:12

Adrian Mole

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answered Jan 14 '23 at 23:07

MyVat9

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How do I convert from a wchar_t* to a wstring?

3 Answers3