Line reader for TCP

racket/syndicate/drivers/line-reader.rkt

@@ -0,0 +1,28 @@
+#lang syndicate/actor
+
+(provide (struct-out tcp-channel-line))
+
+(require "tcp.rkt")
+
+(struct tcp-channel-line (source destination bytes) #:prefab)
+
+;; This should probably be in the standard library.
+(define (bytes-index bs b)
+  (define len (bytes-length bs))
+  (let loop ((i 0))
+    (cond [(= i len) #f]
+          [(eqv? (bytes-ref bs i) b) i]
+          [else (loop (+ i 1))])))
+
+(actor
+ (react
+  (during/actor (observe (tcp-channel-line $src $dst _))
+    (field [buffer #""])
+    (on (message (tcp-channel src dst $bs))
+        (buffer (bytes-append (buffer) bs)))
+    (begin/dataflow
+      (define newline-pos (bytes-index (buffer) (char->integer #\newline)))
+      (when newline-pos
+        (define line (subbytes (buffer) 0 newline-pos))
+        (buffer (subbytes (buffer) (+ newline-pos 1)))
+        (send! (tcp-channel-line src dst line)))))))