feat: support host context changes

src/bindings.ml

@@ -115,6 +115,15 @@ let extism_plugin_call_s =
   fn "extism_plugin_call"
     (plugin @-> string @-> string @-> uint64_t @-> returning int32_t)
 
+
+let extism_plugin_call_with_host_context =
+  fn "extism_plugin_call_with_host_context"
+    (plugin @-> string @-> ptr char @-> uint64_t @-> ptr void @-> returning int32_t)
+
+let extism_plugin_call_with_host_context_s =
+  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 =
@@ -159,6 +168,9 @@ let extism_function_set_namespace =
 let extism_function_free =
   fn "extism_function_free" (ptr void @-> returning void)
 
+let extism_current_plugin_host_context =
+  fn "extism_current_plugin_host_context" (ptr void @-> returning (ptr void))
+
 let extism_current_plugin_memory =
   fn "extism_current_plugin_memory" (ptr void @-> returning (ptr uint8_t))
 

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
+  (** Get the configured host context value *)
+
   (** 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 ->
+    name:string ->
+    'a ->
+    'c ->
+    ('b, Error.t) result
+  (** [call input_type output_type t ~name input host_ctx] executes a function with a host context value,
+      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 ->
+    name:string ->
+    'a ->
+    'c ->
+    '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 failwith "Host_function.host_context" else Ctypes.Root.get ptr

src/plugin.ml

@@ -105,6 +105,26 @@ let call_bigstring (t : t) ~name input =
 let call_bigstring_exn t ~name input =
   call_bigstring t ~name input |> Error.unwrap
 
+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 ctx = Ctypes.Root.create ctx in
+    let rc = f pointer name input len ctx in
+    let () = Ctypes.Root.release ctx in
+    if rc <> 0l then
+      match Bindings.extism_error pointer 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%test "call_bigstring" =
   let manifest = Manifest.(create [ Wasm.file "test/code.wasm" ]) in
   let plugin = of_manifest manifest |> Error.unwrap in
@@ -134,6 +154,20 @@ 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 ~name (a : a) ctx : (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_with_host_context_s 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 ~name input ctx = call_with_host_context a b t ~name input ctx |> Error.unwrap
+
 let%test "call" =
   let manifest = Manifest.(create [ Wasm.file "test/code.wasm" ]) in
   let plugin = of_manifest manifest |> Error.unwrap in