How to compare BSTR against a string in c/c++?

c++ windows com activex
COMer picture COMer · Sep 13, 2010 · Viewed 20.8k times · Source 
wprintf(L"Selecting Audio Input Device: %s\n", 
                            varName.bstrVal);

if(0 == strcmp(varName.bstrVal, "IP Camera [JPEG/MJPEG]"))...

The above reports :

error C2664: 'strcmp' : cannot convert parameter 1 from 'BSTR' to 'const char *'

Answer

Brian R. Bondy picture Brian R. Bondy · Sep 13, 2010

You have to use wcscmp instead:

if(0 == wcscmp(varName.bstrVal, L"IP Camera [JPEG/MJPEG]"))
{
}

Here is a description of the BSTR data type, it has a length prefix and a real string part which is just an array of WCHAR characters. It also has 2 NULL terminators.

The only thing to look out for is that the BSTR data type can contain embedded NULLs in the string portion, so wcscmp will only work in the cases where the BSTR does not contain embedded NULLs (which is probably most cases).

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