Re: bstr

From:

"Igor Tandetnik" <itandetnik@mvps.org>

Newsgroups:

microsoft.public.vc.atl

Date:

Fri, 11 May 2007 12:06:23 -0400

Message-ID:

<#PYlTZ#kHHA.1776@TK2MSFTNGP05.phx.gbl>

John <John@discussions.microsoft.com> wrote:

I have created atl com dll. I want to return some data in bstr as a
reference. But, this bstr should support null characters also in the
data. Is
it possible with BSTR?

Yes, but you must be extremely careful when handling such a BSTR. A lot
of functions will assume a NUL-terminated string and truncate it.

STDMETHODIMP CMyDll::GetData(BSTR *bstrData)
{
char* str = new char[30721];
int nFileHandle =
_open((LPCSTR)"c:\\atlcomdll\\chk.txt",_O_CREAT|_O_BINARY|_O_RDWR|_O_TRUNC,_S_IREAD
| _S_IWRITE); _write(nFileHandle,str,30720);
_close(nFileHandle);
//chk.txt has 30kb data. and it has 100's of null character in this
data.
How to copy this whole data to *bstrData buffer.

It's not clear what you are trying to do here. BSTR holds Unicode
characters. You have read the file into char* array. Do you want to
convert it to Unicode, and then store in BSTR? Or do you want BSTR to
carry binary data as is? For the latter, it's best to use SAFEARRAY of
bytes instead.
--
With best wishes,
Igor Tandetnik

With sufficient thrust, pigs fly just fine. However, this is not
necessarily a good idea. It is hard to be sure where they are going to
land, and it could be dangerous sitting under them as they fly
overhead. -- RFC 1925