From: Alex Fenton <alex@...>
Date: 2006-11-15T18:50:05+09:00
Subject: Re: Ruby <-SWIG-> C arrays

Aureliano Buendia wrote:

> typedef unsigned long uInt32
> someFunction(uInt32 someArray[])
> 
> The array is simply some input. Calling the wrapped function in Ruby:
> 
> Wrapper.someFunction([1, 2, 3])
> 
> produces this error:
> 
> ..in method 'someFunction', argument 1 of type 'uInt32 []' (TypeError)

It looks like you require some typemap here to convert a ruby array of integers to a C array of longs. You probably want %typemap(in), which mangles Ruby function/method params to something that the C function can digest.

Your %typemap(in) will use the RARRAY($input)->len Ruby C macro to get the length of the incoming ruby array. $input is a placeholder for the ruby parameter being processed. Create a new empty uInt32[].

Then, for each element in the Ruby array use the NUM2LONG macro to convert the Ruby integer to a C long, and add this to your uInt32[]. Lastly, assign the uInt32 to the special variable $1, which is a placeholder for the actual value that will be passed to the C function. SWIG will generate the appropriate wrapper code. 

You will want to verify the types of the arguments passed in from ruby, using TYPE and T_ARRAY etc macros.

Suggest you re-read the following sections of the Ruby/SWIG documentation should be useful:

http://www.swig.org/Doc1.3/Ruby.html#Ruby_nn39

http://www.swig.org/Doc1.3/Ruby.html#Ruby_nn47

Sorry I can't give you a complete example, but I'm not a C programmer, just familiar with SWIG. Hopefully this will get you started.

alex