Data input: parse STL and facet import about python-admesh

[hroncok]

Both features are something that I wanted to have but decided not to implement it yet due to higher complexity. I would gladly accept contributions containing those features.

Problem 1: read from stream

This will be hard. Currently, loading from file is done by directly calling underlying admesh code and passing the path down to C. In C, the stl_open function calls stuff that will eventually open the file in different modes.

Possible approaches:

• create a separate loading mechanism in Cython, that works with Python streams (cons: when a bug is found in the C code, it has to be fixed on multiple places)
• change the C code so that it can accept something else than path (cons: I have no idea how to pass a Python stream to C library, I think it is not possible or very hard)

Problem 2: add facets manually

This should be much easier. All that has to be done:

1. change the __cinit__ so that it initializes and empty inmemory STL struct when no filename is given
2. remove the open() method and the _opened attribute
3. add a method that would add a facet to the struct, get inspired by stl_open_merge

Loading facets one by one would be very inefficient. A method that can load facets in bulk would be much better. I suggest it would be able to get list of dicts and/or a NumPy-like array (or even numpy-stl object).

Let me know if ypou decide to implement 2, if so I will do a quick release deprecating the open() method.

[sumpfralle]

Thank you for your detailed thoughts!

Sadly I have to admit, that my cython knowledge is fairly non-existing. Nevertheless I tried my luck and prepared a trivial merge request (#11). It should partly solve problem (2) - except for being highly inefficient.
I assume, that my changes are not suitable (at least not the "add_facets" function). Feel free to ignore/change them at your will.

[hroncok]

Would you like to digg deeper?

[sumpfralle]

I am sorry: no, I do not want to acquire more knowledge about cython.
Please feel free to use or discard my changeset - whatever feels appropriate for you.

[hroncok]

Closing this, since reading from stream will probably not get implemented. Manually adding facets added in #12