[R] Export functions for low-level pointer operations

[eitsupi]

Describe the enhancement requested

It would be useful to have exported the following functions used when using the Arrow C interface.

arrow/r/R/python.R

Lines 18 to 32 in 2e8bd8d

	py_to_r.pyarrow.lib.Array <- function(x, ...) {
	schema_ptr <- allocate_arrow_schema()
	array_ptr <- allocate_arrow_array()
	on.exit({
	delete_arrow_schema(schema_ptr)
	delete_arrow_array(array_ptr)
	})
	x$`_export_to_c`(
	pyarrow_compatible_pointer(array_ptr),
	pyarrow_compatible_pointer(schema_ptr)
	)
	Array$import_from_c(array_ptr, schema_ptr)
	}

• allocate_arrow_schema
• delete_arrow_schema
• allocate_arrow_array
• delete_arrow_array
• allocate_arrow_array_stream
• delete_arrow_array_stream

For now, these could easily be solved by having a dependency on nanoarrow, as it appears that the equivalent functions are provided by nanoarrow, but given that the functions already exist in arrow, it is not clear that it would be worthwhile for the arrow package not to export them.

Component(s)

R

[eitsupi]

Use case example pola-rs/r-polars#754