Re: Problem with writing XML DOM tree to memory buffer.

"Alex Blekhman" <xfkt@oohay.moc>
Wed, 4 Apr 2007 16:43:32 +0300
In addition to Igor's reply, you don't need to call
`Detach()' om `CComBSTR' object; it will leak BSTR.
`CComBSTR' class already has `operator BSTR'. Also, calling
`GlobalLock' is not enough. You should also call
`GlobalSize' in order to determine actual size of written
data. Stream doesn't append terminating NUL automatically.
Here's working example (made with VC2005, though it should
be easily adaptable to VC6):


#include <comutil.h>
#include <comdef.h>
#include <atlstr.h>

_COM_SMARTPTR_TYPEDEF(IUnknown, __uuidof(IUnknown));
_COM_SMARTPTR_TYPEDEF(IDispatch, __uuidof(IDispatch));

#import <msxml4.dll>

_COM_SMARTPTR_TYPEDEF(IStream, __uuidof(IStream));

using namespace MSXML2;

int _tmain(int /*argc*/, _TCHAR* /*argv*/[])

        // Create the document and fill it with
        // some example data.
        IXMLDOMDocument2Ptr spDocument(

        IXMLDOMElementPtr spCurrentNode =
        spCurrentNode->setAttribute(L"value", 3.14159);


        // Let the document persist into a memory stream.
        IStreamPtr spStream;
        HRESULT hr = ::CreateStreamOnHGlobal(
            NULL, TRUE, &spStream);
        if(FAILED(hr)) _com_issue_error(hr);

        _variant_t vtStream(spStream.GetInterfacePtr());
        hr = spDocument->save(vtStream);
        if(FAILED(hr)) _com_issue_error(hr);

        HGLOBAL hMem = NULL;
        hr = ::GetHGlobalFromStream(spStream, &hMem);
        if(FAILED(hr)) _com_issue_error(hr);

        LPVOID lp = ::GlobalLock(hMem);
        CStringA strXmlText((LPCSTR)lp, ::GlobalSize(hMem));

        ::MessageBoxA(NULL, strXmlText, "XML Text",
    catch(const _com_error& e)
        ::MessageBox(NULL, e.ErrorMessage(), _T("Error"),
            MB_OK | MB_ICONERROR);


    return 0;



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