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|
type t = {loaded_libraries: (string, unit) Hashtbl.t; mutex: Mutex.t}
let state : t = {loaded_libraries= Hashtbl.create 16; mutex= Mutex.create ()}
let load_library path : (unit, string) result =
Mutex.protect state.mutex (fun () ->
if Hashtbl.mem state.loaded_libraries path then Ok ()
else
try
Dynlink.loadfile path;
Hashtbl.replace state.loaded_libraries path ();
Ok ()
with Dynlink.Error e -> Error (Dynlink.error_message e) )
(* Convert an engine materialized tuple to the plugin's (string * Obj.t) list format. *)
let to_plugin_row (schema : Schema.t) (tuple : Tuple.materialized) : Sakura_prl_api.tuple option =
let rec go acc = function
| [] -> Some (List.rev acc)
| (attr_name, _) :: rest -> (
match Tuple.AttributeMap.find_opt attr_name tuple.attributes with
| None -> None
| Some attr -> go ((attr_name, attr.Attribute.value) :: acc) rest )
in
go [] schema
(* Convert a plugin row back to an engine materialized tuple. *)
let of_plugin_row relation_name (schema : Schema.t) (row : Sakura_prl_api.tuple) :
Tuple.materialized option =
let rec go acc = function
| [] -> Some {Tuple.relation= relation_name; attributes= acc}
| (attr_name, _) :: rest -> (
match List.assoc_opt attr_name row with
| None -> None
| Some value -> go (Tuple.AttributeMap.add attr_name {Attribute.value} acc) rest )
in
go Tuple.AttributeMap.empty schema
(* Wrap a list of plugin rows as a generator. Uses an array for O(1) indexing. *)
let rows_to_generator relation_name schema (rows : Sakura_prl_api.tuple list) : Generator.t =
let arr = Array.of_list rows in
let n = Array.length arr in
let rec gen i _pos =
if i >= n then Generator.Done
else
match of_plugin_row relation_name schema arr.(i) with
| None -> Generator.Error "Plugin row does not conform to predicate schema."
| Some tuple -> Generator.Value (Tuple.Materialized tuple, gen (i + 1))
in
gen 0
let make_generator relation_name schema (impl : Sakura_prl_api.implementation)
(bindings : Sakura_prl_api.tuple) : Generator.t =
match impl.produce with
| None -> fun _ -> Generator.Done
| Some produce -> (
let rows_result = lazy (produce bindings) in
fun _pos ->
match Lazy.force rows_result with
| Error e -> Generator.Error e
| Ok rows -> rows_to_generator relation_name schema rows _pos )
let make_producer relation_name schema (impl : Sakura_prl_api.implementation) : Relation.producer =
fun bindings -> make_generator relation_name schema impl bindings
let make_membership_criteria schema (impl : Sakura_prl_api.implementation) : Tuple.t -> bool =
match impl.membership_criteria with
| None -> fun _ -> false
| Some check -> (
(* fun _tree_of -> *)
function
| Tuple.NonMaterialized _ -> false
| Tuple.Materialized m -> (
match to_plugin_row schema m with
| None -> false
| Some row -> ( match check row with Ok b -> b | Error _ -> false ) ) )
|
