How to convert char* to BSTR *?

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How to convert char* to BSTR *?

Postby lily » Sat, 17 Apr 2004 07:02:48 GMT

I'm calling a COM function inside this C++ function. How to convert char* to
BSTR and BSTR*?
void myFunction( INchar* name,
OUT char* path)
{
MyCOMFunction( CComBSTR( name), ??);
}
The COM function prototype is like this:
HRESULT MyCOMFunction(IN BSTR name,
OUT BSTR* path)
{

}
Thanks.


Top

Re: How to convert char* to BSTR *?

Postby Brian Muth » Sat, 17 Apr 2004 08:12:41 GMT 

There are many ways of skinning this cat. Here's one:

void myFunction( INchar* name,
                            OUT char* path)
{
    USES_CONVERSION;

     MyCOMFunction( CComBSTR(A2COLE(name));
}

For background reading, see:

 http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vclib/html/_atl_string_conversion_macros.asp 

(watch for line breaks).

Brian
Top

Re: How to convert char* to BSTR *?

Postby dva » Sat, 17 Apr 2004 20:40:00 GMT 

even better use T2COLE instead of A2COLE





 http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vclib/html/_atl_string_conversion_macros.asp
Top

Re: How to convert char* to BSTR *?

Postby ColdShine » Sat, 17 Apr 2004 21:31:05 GMT 

> even better use T2COLE instead of A2COLE

Why on the earth? He's talking about char *, not TCHAR * nor LPTSTR. He'd
get compile errors if he uses T2COLE in an Unicode build.

"Experience is a hard teacher: she gives the test first, the lesson
afterwards."
- Vernon Sanders law
Top

Re: How to convert char* to BSTR *?

Postby Simon Trew » Sat, 17 Apr 2004 23:45:49 GMT 

I believe that is new to ATL7, so if you are stuck with ATL3 (VC6) that is
not an option.

However,

void myFunction(IN char* name, OUT char* path)
{
    MyCOMFunction(_bstr_t(name));
}

is another way of doing it.

Incidentally, if "path" is truly an "out" parameter then this function
signature looks like a good candidate for a buffer overrun. Either pass a
pointer to a pointer and allocate the storage inside myFunction (COM-style),
making the client responsible for cleaning it up (and so requiring it to
know the means used to allocate it), or pass a size_t cchMax which gives the
maximum number of characters that can be copied into path (and respect it).

S.








 http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vclib/html/_atl_string_conversion_macros.asp
Top

Re: How to convert char* to BSTR *?

Postby Brian Muth » Sun, 18 Apr 2004 01:51:09 GMT 

Simon, this works for ATL3 as well as ATL7.
Top

Re: How to convert char* to BSTR *?

Postby Igor Tandetnik » Sun, 18 Apr 2004 02:41:16 GMT 





You can just write CComBSTR(name). CComBSTR has a constructor taking
char*
-- 
With best wishes,
    Igor Tandetnik

"For every complex problem, there is a solution that is simple, neat,
and wrong." H.L. Mencken
Top

Re: How to convert char* to BSTR *?

Postby Kim Grman » Sun, 18 Apr 2004 23:02:28 GMT 

Hey everybody,




You're all missing the out parameter. Simon touched on it, and he has a
point in that the char* is really not adequate for out-params. Either add an
extra indirection (char**) and allocate memory inside myFunction, or add a
buffer length parameter as well, indicating how long the buffer pointer to
by 'path' is.

I'd re-do it something like this;

void myFunction(const char* pszName, char* pszPath, unsigned cchPath)
{
    CComBSTR strPath;
    MyCOMFunction(CComBSTR(pszName), &strPath);

    if(strPath.Length() > 0)
    {
        strncpy(pszPath, OLE2A(strPath), cchPath);
    }
    else
    {
        pszPath[0] = 0;
    }
}

-- 
Best regards,
Kim Grman
Top

Re: How to convert char* to BSTR *?

Postby Simon Trew » Tue, 20 Apr 2004 16:16:22 GMT 

OK thanks Brian, I should trust you to know better :)

S.








is
Top

Re: How to convert char* to BSTR *?

Postby Simon Trew » Tue, 20 Apr 2004 16:21:23 GMT 






Well I thought I did more than that :)... anyway, I suppose I should have
given an example of the rewrite.

Thanks Kim

S.
Top

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Hello I want to be able to convert a pointer that is defined as a BSTR
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issues.  First of all I want to make sure I understand BSTR HUGEP * -<
to me this means I have a BSTR pointer that is cable of 64 bit but I'm
not quiet sure .  Anyway I have the code working to get the elements
from the safe array but I want to convert the array value to a char *
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program.  I can copy  pbstr[0]  into a wchar_t data[300] but Id rather
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at the suface but since a BSTR is not a true Wchar_t then this concerns
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Here is my code

int u_dll_ims21_call(wchar_t *TheConnectString, wchar_t *TheTable,
wchar_t *TheFields, wchar_t *ThePopupTitle, wchar_t *TheOrderBy,
wchar_t *TheWhereClause, wchar_t *ThePosition)
{
	// Now we will intilize COM

	HRESULT hr = CoInitialize(0);

	if(SUCCEEDED(hr))
	{
		_clsCat16Ptr ptrCat16(__uuidof(clsCat16));  //Smart pointer wrapper

		//_clsCat16	    *IclsCat16 = NULL;
		//hr = CoCreateInstance(__uuidof (clsCat16),
		//	          NULL,
		//			  CLSCTX_INPROC_SERVER,
          //            _uuidof (_clsCat16),
			//		  (void**) &IclsCat16);

	//	if(SUCCEEDED(hr))
	//	{

			BSTR bstrTheConnectString= SysAllocString(TheConnectString);
			BSTR bstrTheTable = SysAllocString(TheTable);
			BSTR bstrTheFields= SysAllocString(TheFields);
			BSTR bstrThePopupTitle = SysAllocString(ThePopupTitle);
			BSTR bstrTheOrderBy = SysAllocString(TheOrderBy);
			BSTR bstrTheWhereClause = SysAllocString(TheWhereClause);
			BSTR bstrThePosition = SysAllocString(ThePosition);

			//Create a SafeArray
			SAFEARRAY FAR* RTNArray = NULL;

		//	_bstr_t bvalue = ptrCat16->Popup(&bstrTheConnectString,
&bstrTheTable,
		//		                             &bstrTheFields, &bstrThePopupTitle,
		//									 &bstrTheOrderBy, &bstrTheWhereClause,
		//									 &bstrThePosition);

			short bvalue = ptrCat16->Popup(&bstrTheConnectString, &bstrTheTable,
				                             &bstrTheFields, &bstrThePopupTitle,
											 &bstrTheOrderBy, &RTNArray, &bstrTheWhereClause,
											 &bstrThePosition);

			if(bvalue == 0)
			{
				//Free all the bstrings //
				SysFreeString(bstrTheConnectString);
				SysFreeString(bstrTheTable);
				SysFreeString(bstrTheFields);
				SysFreeString(bstrThePopupTitle);
				SysFreeString(bstrTheOrderBy);
				SysFreeString(bstrTheWhereClause);
				SysFreeString(bstrThePosition);
				return 0;
			}
			//Pointer to the safe array that is returned from the VB call //
			BSTR HUGEP *pbstr;
			wchar_t data[300];
			wchar_t *arraylimit = NULL;
			// check to see if it is a one-dimensional or two-dimensional array
//
			if ( RTNArray->cDims != 1 )
			{
				//Lock the array //
				hr= SafeArrayLock(RTNArray);
				long ai[2];
				int lower1 = RTNArray->rgsabound[1].lLbound;
				int upper1 = RTNArray->rgsabound[1].cElements + lower1;
				//Loop through the row first
				for(int i = lower1; i < upper1; i++)
				{
					ai[0]=i;
					int lower0 = RTNArray->rgsabound[0].lLbound;
					int upper0 = RTNArray->rgsabound[0].cElements + lower0;
					//Now loop through each column in the row //
					for(int j = lower0; j < upper0; j++)
					{
						ai[1]=j;
						hr=SafeArrayPtrOfIndex(RTNArray, ai, (void HUGEP* FAR*)&pbstr);
						if(SUCCEEDED(hr))
						{
							data[0] = L'\000';
							wcscpy(data,pbstr[0]);
							char* lpszText2 = _com_util::ConvertBSTRToString(pbstr[0]);

						}
					}
				}
				//Unlock the array //
				hr= SafeArrayUnlock(RTNArray);
				//Destroy the array //
				hr = SafeArrayDestroy(RTNArray);

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