chunking-port.scm

;; rough conception - chunks output only
(use-modules (ice-9 q))
(define (q-for-each f q)
  (while (not (q-empty? q))
    (f (deq! q))))

(define f! #f)

(define (port->chunking-port port)
  (define queue (make-q))
  (define (put-char c)
    (enq! queue c))
  (define (put-string s)
    (string-for-each (lambda (c) (enq! queue c))
                     s))
  (define (flush)
    (let ((len (q-length queue)))
      (display (number->string len 16) port)
      (display "\r\n" port)
      (q-for-each (lambda (elem) (write-char elem port))
                  queue)
      (display "\r\n" port)))
  (define (get-char)
    (read-char port))
  (define (close)
    (flush)
    (flush) ;; this way a zero chunk gets written
    (close-port port))
  (set! f! flush)
  (make-soft-port
   (vector
    put-char
    put-string
    flush
    get-char
    close)
   "rw"))

(call-with-output-string
 (lambda (out-raw)
   (let ((out-chunked (port->chunking-port out-raw)))
     (display "First chunk" out-chunked)
     (flush-all-ports)
     (f!)
     ;(force-output out-chunked)
     (display "Second chunk" out-chunked)
     (f!)
     ;(force-output out-chunked)
     (display "Third chunk" out-chunked)
     (f!)
     (f!)
     ;(close-port out-chunked)
     )))