Packages that produce or consume cells in compiled code can convert
between 64-bit ids and a5_cell vectors through a5R's C API, without
depending on how a5_cell stores its data. Add LinkingTo: a5R and
Imports: a5R to the package's DESCRIPTION, then include a5R.h:
Details
#include <a5R.h>
// ids to an a5_cell vector; is_na may be NULL
SEXP cells = PROTECT(a5R_cells_from_u64(ids, is_na, n));
// an a5_cell vector to ids and NA flags; returns the length
R_xlen_t n = a5R_cells_to_u64(cells, ids, is_na);a5R_api_version() returns the version of the API, currently 1, also
given by a5_info()$c_api. NA cells
are flagged in an int array, as in an R logical vector, rather than
encoded in the id. Packages written in Rust can call the same functions
through R_GetCCallable("a5R", "a5R_cells_from_u64") and its siblings;
the signatures are in system.file("include", "a5R.h", package = "a5R").