[squeak-dev] Questions regarding FFI

Ricardo Moran richi.moran at gmail.com
Wed May 13 13:41:17 UTC 2009

Hi, I’m trying to make a Squeak interface to OpenCV, the computer vision
library, and I have a few newbie questions about FFI:

1)      I managed to make an ExternalStructure for the IplImage and other
simple structs such as CvScalar, CvSize, etc. I have a problem when trying
to make the ExternalStructure for CvMat, which represents a matrix, because
some members are unions. What should I do to make an ExternalStructure with

2)      To finalize objects the OpenCV library defines some functions such
as cvReleaseImage, cvReleaseMat, etc. As far as I can tell, these functions
receive a pointer-to-pointer as argument. How can I declare such a method in
Squeak? Having one object, how can I get the pointer to that object? Should
I use the #getHandle method?

3)      Some OpenCV functions are declared as inline functions. I haven’t
been able to access those functions from Squeak. Is this an expected

So far, these are the problems I encounter. As you may see from the
questions above my knowledge of Squeak, FFI and C is pretty limited, so I
would be very thankful if someone could give me a hand with these issues.

Thanks, bye
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