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casting from BSTR <-> char *

meverest
meverest asked
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Last Modified: 2010-04-10
Hi folks,

am i allowed to do:

char *str1 = strdup("hello");
BSTR str2 = (BSTR) str1;

or vice-versa?

what happens if i do this, and if it is not legal, how can i convert from wchar to char?

thanks and regards.
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Commented:
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Commented:
>> how can i convert from wchar to char?
use WideCharToMultiByte().

Commented:
If you're using MFC (actually I think this works in non-MFC apps as well), you can also use the string-type conversion macros in afxpriv.h.

For instance, to convert from WCHAR to CHAR, you can use the W2T macro.

There is a whole family of these that convert from almost any string type to almost any other.  (I say "almost" since there is probably some type that is not supported.)

Commented:
The macros that jhance mentioned are actually from ATL. See

TN059: Using MFC MBCS/Unicode Conversion Macros
http://msdn.microsoft.com/isapi/msdnlib.idc?theURL=/library/devprods/vs6/visualc/vcmfc/_mfcnotes_tn059.htm

String Conversion Macros
http://msdn.microsoft.com/isapi/msdnlib.idc?theURL=/library/devprods/vs6/visualc/vcmfc/_atl_string_conversion_macros.htm

If you are using Visual C++ 5.0 or above, you may also use the _bstr_t class since it has the operator wchar_t*, char*.

_bstr_t
http://msdn.microsoft.com/isapi/msdnlib.idc?theURL=/library/devprods/vs6/visualc/vclang/_pluslang__bstr_t.htm

Commented:
nietod> To convert a C-stly string to a BSTR you use the
 nietod> SysAllocString() function defined in oleauto.h.  Like

 nietod> BSTR str2 = SysAllocString("hello");

Your code doesn't compile.  I think you meant to show

  BSTR str2 = SysAllocString(L"hello");

..B ekiM

Commented:
Thanks--everyone.
Top Expert 2008

Author

Commented:
thanks netiod,

although i am already using SysAllocString() (and SysReAllocString()), i found what i was after when lloking into WideCharToMultiByte and related functions.

regards.
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