[python-win32] problem with win32com and one-based indexed collections

[Barry B]

I have run across what I believe may be a shortcoming with win32com when
trying to call functions that expect one-based indexed arrays as input.  The
function I'm trying to invoke which demonstrates the problem is defined in
my documentation as follows:

HRESULT SyncRead(
      [in] SHORT Source,
      [in] LONG NumItems,
      [in] SAFEARRAY(LONG) * ServerHandles,
      [out] SAFEARRAY(VARIANT) * Values,
      [out] SAFEARRAY(LONG) * Errors,
      [out,optional] VARIANT * Qualities,
      [out,optional] VARIANT * TimeStamps);

In Python, this looks like:

server_handles = [16384,16385]
num_items = 2
values, errors, qualities, timestamps = groups.SyncRead(2, num_items,
server_handles)

The num_items parameter is supposed to tell the function the total number
sever_handles being passed in.  Anyway, the above code always throws a com
exception and fails.  I am assuming this issue is due to the SyncRead
function using one-based indexing for its array collection.

However, if I append an extra "dummy" argument to the beginning of the
server_handles list, it will always work.

server_handles = [0, 16384,16385]
num_items = 2
values, errors, qualities, timestamps = groups.SyncRead(2, num_items,
server_handles)

The above example is a very poor solution since it appears to produce a slow
memory leak in my application.  Every 10 to 12 times the SyncRead call is
invoked using the exact same server_handles, memory consumption increases by
4kb.  This memory leak problem does not happen when called from VB.

As an amusing test, I tried setting the variables passed to the function as
follows:

server_handles = [0, 16384, 16385, 0, 0, 0, 0, 0, 0, 0, 0, 0]
num_items = 2

This makes an even bigger memory leak, leading me to believe any extra
elements passed in the list beyond the num_items passed will always be
allocated but never freed.

Does Mark or anyone else know how to correctly pass a collection to a COM
call using one-based indexing that won't cause a mem leak?   I couldn't find
any mention of this issue in the Python Win32 book other than an Excel
example which didn't seem to apply.

-BB
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