access RoaringBitmap from cython for static typing about roaringbitmap

[andreasvc]

You wouldn't use a .h file, but a .pxd file. See http://docs.cython.org/en/latest/src/userguide/sharing_declarations.html

A RoaringBitmap object is a Python object, implemented with a cdef class, and until now I only exposed it with a Python API. Therefore, any operation you do with it has to go through Python, and there is (as far as I understand) almost nothing to be gained from static typing and cimporting RoaringBitmap from Cython headers in a .pxd file. In particular, as I recall, even cdef functions of a cdef class still go through the Python API, because they are part of a Python object, so for a Cython API to make sense, one would need to avoid using the cdef class.

What would need to happen for this to make sense is that it should be decided which functions will be exposed as a public Cython API, and these cdef functions and structs should then be listed in a .pxd file. However, I'm not sure whether it is worth the effort. In general, it's always good to profile to identify bottlenecks before investing time in a potentially complicated change like this.

[remiadon]

Agreed, .pyx file, not .h, I got confused

Now, from what I understand, the way to do it would be to define a _RoaringBitmap cdef struct, which would be an attribute inside the RoaringBitmap cdef class (just like you do for Block), and then expose cdef functions taking pointers on this struct as arguments.

Anyway I understand this seems complicated and gives no guarantee over potential speedups.

Thank you