From: Michael Hale <michael@...>
Date: 2004-08-21T06:47:08+09:00
Subject: Re: calling a swig generated function

Thank you for the suggestion.  I was able to get my code to work with 
the following in my smartlib.i file:
	
	%apply unsigned long *OUTPUT { unsigned long *pulGap };

Now I call the function like this:
	
	NSCalculateGap(iMode, iSpeed, ulPacketLength, dValue, hub, slot, port)

And get back an array with the first element being the original return 
value and the second being the value of the pulGap pointer.  Like this:

	[0,1273]

BTW here is the method definition from my header file:

int		DLL_EXPORT NSCalculateGap(int iMode, int iSpeed,
										unsigned long ulPacketLength,
										double dValue,
										unsigned long *pulGap,
										int iHub, int iSlot, int iPort);


On Aug 19, 2004, at 9:09 AM, Lyle Johnson wrote:

> On Thu, 19 Aug 2004 09:58:32 +0900, Michael Hale
> <michael@halefamilysite.com> wrote:
>
>> I have a library that I wrapped with SWIG.  One of the SWIG generated
>> functions looks like this:
>
> <snip>
>
> I'm guessing that the fifth argument is declared as a pointer to an
> unsigned long, correct? The problem is that SWIG doesn't know which
> one of the many interpretations of that to use. In this case, it
> appears that the NSCalculateGap() function uses that unsigned long
> pointer argument to return a value (i.e. for output), but as far as
> SWIG knows you could be passing in a single unsigned long value, or
> even an array of unsigned longs, as input.
>
>> How should I call this function from ruby?
>
> You're going to need to use a typemap of some kind to let SWIG know
> that, in this case, that unsigned long pointer argument is actually an
> output value. Depending on how you've written your SWIG interface
> file, you'll want to do something like this:
>
>     // Include declarations for output typemaps from the SWIG library
>     %include typemaps.i
>
>     // Apply SWIG's OUTPUT typemap for unsigned long values to the
> "ulGap" argument
>     %apply unsigned long *OUTPUT { unsigned long ulGap; }
>
>     // Here's what I would guess the actual function declaration looks 
> like...
>     void NSCalculateGap(int iMode, int iSpeed, unsigned long
> ulPacketLength, double dValue, unsigned long *ulGap, int iHub, int
> iSlot, int iPort);
>
> Now, when you call this function from Ruby you will only pass in the
> seven input arguments, and catch the output value as the method
> result, e.g.
>
>     ulGap = Smartlib::NSCalculateGap(iMode, iSpeed, ulPacketLength,
> dValue, hub, slot, port)
>
> For more information, see the "Argument Handling" chapter of the SWIG 
> manual:
>
>     http://www.swig.org/Doc1.3/Arguments.html
>
> Hope this helps,
>
> Lyle
>
>
>
  "OS X: because it was easier to make UNIX user-friendly than to fix 
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