Add as_ffi_ptr to NDArray

[barakugav]

The function return a Capsule with the raw b2nd_array_t* pointer, and it is useful for passing the array to C functions

[FrancescAlted]

Ok. Can you explain why exactly you want to add this functionality?

[barakugav]

Ok. Can you explain why exactly you want to add this functionality?

I write a library that save data to disk, and some of it is ndarrays. The library is written in Rust and has a Rust API, and I use blosc2 through Rust bindings crate to compress the ndarray data.
In addition, there is a python bindings package that calls the Rust code, and expose a similar API in Python. I want to be able to pass blosc2.NDArray objects through the FFI boundary to Rust, convert it to the Rust bindings object and write it, and also read an array in Rust and pass it back to Python, and I want to do it all without copying.
In both Rust and Python the libraries hold a pointer to b2nd_array_t, so my solution is to expose it

[FrancescAlted]

LGTM