From: Andreas Lundgren <lists@...>
Date: 2012-10-26T17:46:11+09:00
Subject: Creating a pointer to SAFEARRAY(BSTR) for COM object communication

Hi!

I have a hardware driver in DLL format that I would like to invoke from
a Ruby script using the win32ole gem. One of the inputs is defined as a
"SAFEARRAY(BSTR)*" is it possible to create such a pointer in Ruby?

A BSTR type is defined on MSDN. Four byte header with length, then data
and then two null characters as a terminator.



===== WORKING =====
When I call another method defined like this:

HRESULT ICdfGetHandlerByName::GetHandlerByName([in] BSTR HandlerName,
[out, retval] IUnknown ** ppUnk)

I use this Ruby call:
light_i = my_handler_interface.GetHandlerByName("CdfLight")

Ruby solves this, I do not assemble the BSTR by hand, not introducing
the header, terminator or anything, not doing anything to get the output
from the double pointer to the result variable. Ot works!



===== NOT WORKING =====
This method however, I just cannot solve how to call:

HRESULT ICdfHandleManager::ListHandleTypes([in, out] long * Count,
[in, out, size_is(*Count)] SAFEARRAY(BSTR)* HandleTypes )

Anyone have any idéa how to create a pointer ro a SAFEARRAY(BSTR)?

I constantly get "Type mismatch." and I have tried dussens of different
syntax.

straight_ruby_ldh_api.rb:30:in `method_missing':
ListHandleTypes(WIN32OLERuntimeError)
    OLE error code:0 in <Unknown>
      <No Description>
    HRESULT error code:0x80020005
      Type mismatch.
        from straight_ruby_ldh_api.rb:30


(I also tried to assemble the BSTR myself although the calls with
straigh usage of BSTR don't require me to take any action.

length = 512
data = "x"*(length+4+2)
#Header
length_hs = length.to_s(16)
if (4 < length_hs.length)
  raise "To Large Data"
end
for i in (0..3) do
  data[i+4-length_hs.length] = length_hs[(i)..(i)].to_i
end

In Python it is very smooth to use this DLL, works of the shelf. I
really need to solve this in order for us to keep Ruby! :-/

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