path: root/lib/nt_ffi.ml

(* Low-level ctypes bindings to RNT_C_API.h.
   This module is internal to Nt — never import it anywhere else. *)

open Ctypes
open Foreign

let fn name typ = foreign name typ

(* Runtime ----------------------------------------------------------------- *)
let rnt_init =
  fn "rnt_init" (string @-> string @-> returning int)

(* Auth -------------------------------------------------------------------- *)
let rnt_firewall =
  fn "rnt_firewall" (string @-> ptr (ptr char) @-> returning int)

(* Session lifecycle ------------------------------------------------------- *)
let rnt_session_open =
  fn "rnt_session_open" (ptr void @-> ptr (ptr char) @-> returning int)

let rnt_session_close =
  fn "rnt_session_close" (string @-> returning int)

let rnt_session_set_branch =
  fn "rnt_session_set_branch"
    (string @-> string @-> string @-> returning int)

(* Ephemeral relations ------------------------------------------------------ *)

(* rnt_generator_fn: (ctx, args, offset, limit, sink) -> int.
   OCaml closures passed here cross into C; the closure must stay reachable
   for as long as RNT may invoke it (Nt retains them, see
   Nt.retained_generators). *)
let rnt_generator_fn =
  funptr
    (ptr void @-> string @-> size_t @-> size_t @-> ptr void @-> returning int)

let rnt_sink_emit =
  fn "rnt_sink_emit" (ptr void @-> string @-> returning int)

let rnt_register_ephemeral_relation =
  fn "rnt_register_ephemeral_relation"
    (string @-> int @-> string @-> rnt_generator_fn @-> ptr void @-> int
     @-> string @-> string @-> string @-> ptr (ptr char) @-> returning int)

let rnt_drop_ephemeral_relation =
  fn "rnt_drop_ephemeral_relation" (string @-> string @-> returning int)

(* Handle lifecycle -------------------------------------------------------- *)
let rnt_open_handle =
  fn "rnt_open_handle" (string @-> ptr void @-> returning (ptr void))

let rnt_close_handle =
  fn "rnt_close_handle" (ptr void @-> returning int)

(* Branch hash-pointer ----------------------------------------------------- *)
let rnt_branch_target =
  fn "rnt_branch_target"
    (ptr void @-> ptr (ptr char) @-> returning int)

let rnt_branch_advance =
  fn "rnt_branch_advance" (string @-> string @-> returning int)

(* Object registration ----------------------------------------------------- *)
let rnt_register_relation =
  fn "rnt_register_relation" (string @-> returning int)

let rnt_register_branch =
  fn "rnt_register_branch" (string @-> string @-> returning int)

(* Branch / snapshot relation enumeration ----------------------------------- *)
let rnt_list_relations =
  fn "rnt_list_relations" (string @-> ptr (ptr char) @-> returning int)

let rnt_list_branch_multigroups =
  fn "rnt_list_branch_multigroups" (string @-> ptr (ptr char) @-> returning int)

let rnt_list_snapshot_relations =
  fn "rnt_list_snapshot_relations" (string @-> ptr (ptr char) @-> returning int)

(* Tuple storage ----------------------------------------------------------- *)
let rnt_link_tuple =
  fn "rnt_link_tuple"
    (string @-> string @-> ptr (ptr char) @-> returning int)

let rnt_unlink_tuple =
  fn "rnt_unlink_tuple" (string @-> string @-> returning int)

let rnt_clear_relation =
  fn "rnt_clear_relation" (string @-> returning int)

let rnt_relation_root =
  fn "rnt_relation_root"
    (string @-> ptr (ptr char) @-> returning int)

(* Cursor and VM ----------------------------------------------------------- *)
let rnt_cursor_open =
  fn "rnt_cursor_open" (ptr void @-> returning (ptr void))

let rnt_cursor_next =
  fn "rnt_cursor_next" (ptr void @-> ptr (ptr char) @-> returning int)

let rnt_cursor_close =
  fn "rnt_cursor_close" (ptr void @-> returning int)

(* VM plan builder --------------------------------------------------------- *)

(* For PlanAction in RNT_C_API.h, where one context struct per operator is laid
   side by side (no unions unfortunately as ctypes has no union support 🤡, and
   the C side reads only the member matching [operation]). Strings are passed
   as [ptr char]; the caller owns the backing CArray and must keep it alive across
   the rnt_plan_assemble call (the C side copies immediately). *)

type plan_args_scan
let plan_args_scan : plan_args_scan structure typ = structure "PlanArgsScan"
let scan_relation_path = field plan_args_scan "relation_path" (ptr char)
let () = seal plan_args_scan

type plan_args_join
let plan_args_join : plan_args_join structure typ = structure "PlanArgsJoin"
let join_left  = field plan_args_join "left" (ptr void)
let join_right = field plan_args_join "right" (ptr void)
let () = seal plan_args_join

type plan_args_take
let plan_args_take : plan_args_take structure typ = structure "PlanArgsTake"
let take_source = field plan_args_take "source" (ptr void)
let take_limit  = field plan_args_take "limit" size_t
let () = seal plan_args_take

type plan_args_project
let plan_args_project : plan_args_project structure typ =
  structure "PlanArgsProject"
let project_source = field plan_args_project "source" (ptr void)
let project_attrs  = field plan_args_project "attrs" (ptr (ptr char))
let () = seal plan_args_project

type plan_action
let plan_action : plan_action structure typ = structure "PlanAction"
let action_operation = field plan_action "operation" int
let action_scan      = field plan_action "scan" plan_args_scan
let action_join      = field plan_action "join" plan_args_join
let action_take      = field plan_action "take" plan_args_take
let action_project   = field plan_action "project" plan_args_project
let () = seal plan_action

(* nt::Operation values, RNT include/VM.h *)
let fol_operation_scan    = 1
let fol_operation_join    = 2
let fol_operation_take    = 3
let fol_operation_project = 4

let rnt_plan_assemble =
  fn "rnt_plan_assemble" (plan_action @-> returning (ptr void))

let rnt_plan_free =
  fn "rnt_plan_free" (ptr void @-> returning void)

let rnt_vm_execute_plan =
  fn "rnt_vm_execute_plan" (ptr void @-> returning (ptr void))

let rnt_vm_cursor_next =
  fn "rnt_vm_cursor_next" (ptr void @-> ptr (ptr char) @-> returning int)

let rnt_vm_cursor_close =
  fn "rnt_vm_cursor_close" (ptr void @-> returning int)

(* Memory management ------------------------------------------------------- *)
let rnt_free_string =
  fn "rnt_free_string" (ptr char @-> returning void)

let rnt_free_bytes =
  fn "rnt_free_bytes" (ptr uint8_t @-> returning void)

(* --------------------------------------------------------------------------
   Helpers shared by Nt (not exported from the library module)
   -------------------------------------------------------------------------- *)

let null_char_ptr : char ptr = from_voidp char null

let cstring (s : string) : char CArray.t =
  let n = String.length s in
  let arr = CArray.make char (n + 1) in
  String.iteri (CArray.set arr) s;
  CArray.set arr n '\000';
  arr

(* Reads a null-terminated C string from a char pointer, then frees it. *)
let consume_cstring (p : char ptr) : string =
  let n = ref 0 in
  while !@(p +@ !n) <> '\000' do incr n done;
  let s = string_from_ptr p ~length:!n in
  rnt_free_string p;
  s

(* Allocates a char* out-parameter, calls [f], returns the rc and string. *)
let with_out_string (f : char ptr ptr -> int) : int * string option =
  let pp = allocate (ptr char) null_char_ptr in
  let rc = f pp in
  let p  = !@ pp in
  if is_null p then (rc, None)
  else (rc, Some (consume_cstring p))

(* Converts a void* (returned from open_handle / cursor_open) to nativeint.
   Returns None when the pointer is NULL (failure). *)
let ptr_to_opt (p : unit ptr) : nativeint option =
  if is_null p then None
  else Some (raw_address_of_ptr p)

(* Converts a stored nativeint back to a void* for API calls. *)
let nint_to_ptr (n : nativeint) : unit ptr =
  ptr_of_raw_address n