replacing def_buffer

[fraguada]

I'm working on switching our lib to use nanobind and don't have a good idea of how to replace def_buffer. Here is an example of what we have running in pybind:

From: https://github.com/mcneel/rhino3dm/blob/main/src/bindings/bnd_nurbscurve.cpp#L255

py::class_<BND_NurbsCurvePointList>(m, "NurbsCurvePointList", py::buffer_protocol())
    // ...
    .def_buffer([](BND_NurbsCurvePointList& pl) -> py::buffer_info
    {
      return py::buffer_info
      (
        pl.GetCurve()->m_cv,                      /* Pointer to buffer */
        sizeof(double),                           /* Size of one scalar */
        py::format_descriptor<double>::format(),  /* Python struct-style format descriptor */
        2,                                        /* Number of dimensions */
        {pl.Count(), pl.GetCVDims() },            /* Buffer dimensions */
        {pl.GetCurve()->m_cv_stride * sizeof(double), sizeof(double)}  /* Strides (in bytes) for each index */
      );
    })
    //...
    ;

Would appreciate any tips on how to do this in nanobind!

[wojdyr]

FTR a similar question was asked by @awni in #478

[awni]

We did this in MLX. Here's the relevant code if it's useful:

• Insert the right functions in the object slots https://github.com/ml-explore/mlx/blob/main/python/src/array.cpp#L209-L213
• Implement the buffer protocol functions https://github.com/ml-explore/mlx/blob/main/python/src/buffer.h

[fraguada]

Thanks for the tip. We'll study how to implement the buffer protocol functions in our code base based on your implementation and report back when we have something working.