How to convert BSTR string to Unsigned Char (Using com technology in the appln)

manpreet Best Answer 2 years ago

I am writing small application which uses com technology. I want to convert BSTR string to an unsigned char. To do this, i used W2A() Macro to convert from BSTR to String and then copied String.C_STR() to an unsigned char array. The code snippet is as follows:

Send(BSTR *packet, int length)
{ 
     std::string strPacket = W2A(*packet);
     unsigned char * pBuffer = new unsigned char [strPacket.length()+1];
     memset(pBuffer,0,strPacket.length()+1); 
     memcpy(pBuffer,strPacket.c_str(),strPacket.length()+1);
}

This works fine when packet contains normal string. But if the packetcontains a NUL character in it, the problem occurs. Some unknown characters appear after that NUL in the pBuffer i.e, after conversion.

Can anyone please let me know how to avoid that? Or is there any other way to do it correctly?

manpreet 2 years ago

A BSTR is a Windows API type and must be managed with API macros or functions. If you cannot use W2A macro because your string may have null chars inside, you will have to use functions as WideCharToMultiByte that can convert from wide characters of BSTR to narrow chararacters for a char*. Be sure to have the SDK documentation. Alternatively, you could make you program use WCHARs