feat: add host context

src/bindings.ml

@@ -128,6 +128,19 @@ let extism_plugin_call_s =
   fn "extism_plugin_call"
     (plugin @-> string @-> string @-> uint64_t @-> returning int32_t)
 
+let extism_current_plugin_host_context =
+  fn "extism_current_plugin_host_context" (ptr void @-> returning (ptr void))
+
+let extism_plugin_call_with_host_contet =
+  fn "extism_plugin_call_with_host_context"
+    (plugin @-> string @-> ptr char @-> uint64_t @-> ptr void
+   @-> returning int32_t)
+
+let extism_plugin_call_s_with_host_context =
+  fn "extism_plugin_call_with_host_context"
+    (plugin @-> string @-> string @-> uint64_t @-> ptr void
+   @-> returning int32_t)
+
 let extism_error = fn "extism_plugin_error" (plugin @-> returning string_opt)
 
 let extism_plugin_output_length =

src/extism.mli

@@ -296,6 +296,9 @@ module Host_function : sig
   val output : (module Type.S with type t = 'a) -> ?index:int -> t -> 'a -> unit
   (** Convert a value, allocate it and update the results array at [index] *)
 
+  val host_context : t -> 'a option
+  (** Get configured host context *)
+
   (** Some helpter functions for reading/writing memory *)
   module Memory_handle : sig
     val memory : ?offs:Unsigned.UInt64.t -> t -> Unsigned.uint8 Ctypes.ptr
@@ -421,6 +424,28 @@ module Plugin : sig
     'b
   (** Similar to {!call} but raises an exception using {!Error.unwrap} *)
 
+
+  val call_with_host_context :
+    (module Type.S with type t = 'a) ->
+    (module Type.S with type t = 'b) ->
+    t ->
+    ctx: 'c ->
+    name:string ->
+    'a ->
+    ('b, Error.t) result
+  (** [call_with_host_context input_type output_type t ~ctx ~name input] executes a function with input
+      and output types defined in {!Type} *)
+
+  val call_with_host_context_exn :
+    (module Type.S with type t = 'a) ->
+    (module Type.S with type t = 'b) ->
+    t ->
+    ctx:'c ->
+    name:string ->
+    'a ->
+    'b
+  (** Similar to {!call_with_host_context} but raises an exception using {!Error.unwrap} *)
+
   val free : t -> unit
   (** Free a plugin immediately, this isn't normally required unless there are a
       lot of plugins open at once *)

src/host_function.ml

@@ -103,3 +103,7 @@ let input (type a) (module C : Type.S with type t = a) ?index t =
   C.decode bs
 
 let input_exn a ?index t = input a ?index t |> Error.unwrap
+
+let host_context t =
+  let ptr = Bindings.extism_current_plugin_host_context t.pointer in
+  if Ctypes.is_null ptr then None else Some (Ctypes.Root.get ptr)

src/plugin.ml

@@ -98,6 +98,26 @@ let call' f { pointer; _ } ~name input len =
       in
       Ok buf
 
+let call_with_host_context' f { pointer; _ } ~name input len ctx =
+  if Ctypes.is_null pointer then Error.throw (`Msg "Plugin already freed")
+  else
+    let root = Ctypes.Root.create ctx in
+    let rc = f pointer name input len root in
+    let err = Bindings.extism_error pointer in
+    if rc <> 0l || Option.is_some err then
+      match err with
+      | None -> Error (`Msg "extism_plugin_call failed")
+      | Some msg -> Error (`Msg msg)
+    else
+      let out_len = Bindings.extism_plugin_output_length pointer in
+      let ptr = Bindings.extism_plugin_output_data pointer in
+      let buf =
+        Ctypes.bigarray_of_ptr Ctypes.array1
+          (Unsigned.UInt64.to_int out_len)
+          Char ptr
+      in
+      Ok buf
+
 let call_bigstring (t : t) ~name input =
   let len = Unsigned.UInt64.of_int (Bigstringaf.length input) in
   let ptr = Ctypes.bigarray_start Ctypes.array1 input in
@@ -135,6 +155,23 @@ let call (type a b) (module In : Type.S with type t = a)
 
 let call_exn a b t ~name input = call a b t ~name input |> Error.unwrap
 
+let call_with_host_context (type a b) (module In : Type.S with type t = a)
+    (module Out : Type.S with type t = b) t ~ctx ~name (a : a) :
+    (b, Error.t) result =
+  let input = In.encode a in
+  let len = String.length input in
+  match
+    call_with_host_context' Bindings.extism_plugin_call_s_with_host_context t
+      ~name input
+      (Unsigned.UInt64.of_int len)
+      ctx
+  with
+  | Ok x -> Out.decode x
+  | Error e -> Error e
+
+let call_with_host_context_exn a b t ~ctx ~name input =
+  call_with_host_context a b t ~ctx ~name input |> Error.unwrap
+
 let%test "call" =
   let manifest = Manifest.(create [ Wasm.file "test/code.wasm" ]) in
   let plugin = of_manifest manifest |> Error.unwrap in