Question

I have a Swig-wrapped C library that I use in Ruby. I have no control over Swig or any interface definitions since that is done by the vendor of the interface.

No I find that there’s a function in the library that has a char ** output parameter defined (among others). Example function definition:

void get_information(char * input, char **output, int someint)

Of course, my first attempt in Ruby was:

output_thing = ''
get_information "input", output_thing, 123
puts output_thing

This resulted in the error message

Expected argument 1 of type char **, but got String “”

Having no experience in Swig, I’m kindof stuck. Is it possible to make use of this function in Swig without defining or using a typemap?

Thanks in advance for your quick responses!

Answer 1

I found it (weee!)
There is a new_charpp method that creates the correct datatype. Apparently you have several of these methods for each of the primitives and commonly used datatypes (new_longpp, new_longlongpp, new_intpp et cetera).

Afterwards, you can read the correct contents from this variable using charpp_value(…)