Add 'shf/' from commit 'b6c5a95b664aeb861d7b33ffc9eefe447ba99dd7'

git-subtree-dir: shf
git-subtree-mainline: 401408448f
git-subtree-split: b6c5a95b66

shf/shell/make-mailbox.sml

@@ -0,0 +1,29 @@
+signature MAKE_MAILBOX =
+sig
+  type t
+end
+
+functor MakeMailbox(Fn: MAKE_MAILBOX) =
+struct
+  val messages: Fn.t vector ref = ref #[]
+
+  fun getMessagesAndClear () =
+    let
+      val () = MLton.Thread.atomicBegin ()
+      val msgs = !messages
+      val () = messages := #[]
+      val () = MLton.Thread.atomicEnd ()
+    in
+      msgs
+    end
+
+  fun append newMsg =
+    let
+      val () = MLton.Thread.atomicBegin ()
+      val msgs = !messages
+      val msgs = Vector.concat [msgs, #[newMsg]]
+      val () = messages := msgs
+    in
+      MLton.Thread.atomicEnd ()
+    end
+end