Wrapping array of booleans

acoussat · September 9, 2019, 9:40am

Hi!

I am currently working on wrapping an RTK filter which has a bool * property along with a setter. The wrapped filter properly compiles but the method, when called from a Python script, produces an error (something like the method expects a bool *). I call it by passing a standard Python array (like [True, False, True]) as a parameter. Wrapping C arrays works correctly for other data types, such as int * or float *, but seems broken for bool *.

I tried to look at ITK source code in order to figure out how C arrays are wrapped, but I could not understand, and as far as I searched ITK never wraps bool *. I also tried to replace my bool * by a std::vector<bool> and it made the wrapped filter work.

I thus have several questions:

According to ITK development guidelines, is it alright to wrap a std::vector<bool> instead of a bool *? (RTK tries to stick as much as possible to ITK guidelines.)
Is there something to modify in ITK which would enable bool * to be properly wrapped?
Is there any significant difference in wrapping a std::vector instead of a standard C array?

Sorry if the questions seem basic, I am far from being a swig expect.

Thank you very much!

dzenanz · September 9, 2019, 1:17pm

@matt.mccormick can best answer this question, but probably in about two weeks when he gets back to the office.

phcerdan · September 9, 2019, 1:41pm

Not tested, but should be easy to add a couple of lines here:

github.com

InsightSoftwareConsortium/ITK/blob/master/Modules/Core/Common/wrapping/SwigExtras.i#L15


%include "carrays.i"
%array_functions(unsigned long, ULArray);
%array_functions(long, LArray);
%array_functions(int, IArray);
%array_functions(float, FArray);
%array_functions(double, DArray);
%array_class(unsigned long, ULArrayClass);
%array_class(long, LArrayClass);
%array_class(int, IArrayClass);
%array_class(float, FArrayClass);
%array_class(double, DArrayClass);


// Create swig version of std::list with
// a specialization for std::string.
// This is because list<std::string> is used
// in the wrapper interface of ITK and for java
// this creates SWIGTYPE_p_*.java files that are
// too big for windows file systems.   But if the
// class is wrapped, the shorter name StringList is used.


%{

%array_functions(bool, BArray);
%array_class(bool, BArrayClass);

acoussat · September 13, 2019, 1:43pm

Hi,

Thank you for your kind replies!
I have tried to implement @phcerdan’s solution, and recompiled everything from scratch, but the error message remains identical:
TypeError: in method '...', argument 2 of type 'bool *'

I’m still stuck with this issue, as my understanding of Swig is very limited. Any tip would be greatly appreciated! Thank you very much.