Re: Marshaling a byte array by ref

Hi Al,

First I must let you know that its been quite a while since I was almost
"fluent" in VARIANT-arguments. So please don't take everything I write
below as the "one-and-only" truth on VARIANT's :-)

From your description I am still somewhat in doubt about whether your
are using the COM-functionalities of Jawin (which I would expect when we
are talking about VARIANTS) or whether your method is actually a
DLL-exported "old-style" function using the VARIANT-types for some reason?

So are you calling the function using a DispatchPtr, a COMPtr or a FuncPtr?

If you are using a *FuncPtr*, Sean's and my comments from previous mails
may be what you are looking for, although I fear that it would require
manual formatting of the VARIANT structures from Java (I can't really
remember how the marshalling code is on the native side, and whether it
can handle 'v' and 'V' instruction strings.

If you are using a *DispatchPtr* you should be using a
Variant.ByrefHolder for your out variables:

> vTag must be VT_UI4
> vValue must be VT_BYREF|VT_UI1
> vinBuff must be VT_BYREF|VT_UI1
> vbuffSize must be VT_UI4
> vinfLen must be VT_BYREF|VT_UI4

But I assume that for the above you means:
  vValue must be VT_ARRAY|VT_UI1
  vinBuff must be VT_ARRAY|VT_UI1 (|VT_BYREF)
  vinfLen must be VT_ARRAY|VT_UI4 (|VT_BYREF)

Also I am somewhat in doubt about how the method actually requires the
caller to allocate vinBuff and send the length in vbuffSize? This is not
how I previously worked with SAFEARRAY**'s. But perhaps some other
VARIANT-experts on the list can help us on this?

The VARIANT-documentation (as I read it) does not separate clearly
between [in] and [out] VT_ARRAY. From

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/automat/html/e305240e-9e11-4006-98cc-26f4932d2118.asp

it states both:

  SAFEARRAY               * parray;          // VT_ARRAY|*.

and

  SAFEARRAY               ** pparray;        // VT_ARRAY|*.

Thats why I put the VT_BYREF in () above.

But one of the Jawin unittests actually contains some code showing how
to call a method with an input SAFEARRAY and an output SAFEARRAY (both
of type VT_ARRAY|VT_I4), with the signature:

STDMETHOD(multiplySingleIntArray)(/*[in]*/ int multiplier,
       /*[in]*/SAFEARRAY* set,
       /*[out]*/SAFEARRAY** pOutset);

In the DispatchTestBase#testMultiplySingleIntArrayInvoke()-method it is
shown how to call this using the Variant.ByrefHolder

http://jawinproject.cvs.sourceforge.net/jawinproject/jawin/test/org/jawin/DispatchTestBase.java?revision=1.4&view=markup

This should also work for SAFEARRAYS of VT_UI1, i.e. Java byte[].

Hope this helps you a little further

Best Regards
Morten