flan/test/programs/agent-queue.flan

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;;;; The job ring between the listener thread and the game thread, and what it
;;;; does when it is full.
;;;;
;;;; The window this needs is "the listener has queued modules the game thread
;;;; has not looked at yet", and that window has to be held open by something
;;;; other than a timer — how long sixty-five connections take on a loaded
;;;; machine is exactly the kind of race a test must not be. So the program
;;;; blocks on stdin: the test fills the ring, checks what the agent said, and
;;;; only then writes the byte that lets the program poll.
(import agent "vendor:agent")
;;; libc's, declared straight: no aggregate crosses the boundary, so there is
;;; nothing for a shim to do.
(declare stdin-byte [] i32 "getchar")
(defonce ticks i64)
(defn tick [] i64
(set ticks (+ ticks 1))
ticks)
(defn main [args [str]] i32
(if (< (length args) 2)
(do (println "usage: agent-queue <socket>") 2)
(do
(if (< (agent/start (at args 1)) 0)
(do (println "cannot listen") 1)
(do
(println "ready")
(stdin-byte)
;; How many the ring actually held. Every module queued is installed
;; here, so this number is the count of slots that survived — which
;; is the whole claim: a ring that overwrote the slot it was reading
;; would answer with something else.
(print (agent/poll)) (println "")
;; Round two: one evaluated expression, whose rendering is longer
;; than the 4K the dev runtime will hold. The program has to still be
;; here afterwards for the value to be read back off the socket, so
;; it waits a third time and leaves on end of file.
(stdin-byte)
(print (agent/poll)) (println "")
(stdin-byte)
0)))))