gistfile1.sls

(define (write-handler fd)
    ;; epoll tells us to write to socket
    (let ((buf (hash-table-ref fd-write-table fd)))
        (##net#write fd buf (string-length buf)))

    ;; write prompt to client after sending buf
    (##net#write fd "> " 2)

    ;; clear out write buffer
    (hash-table-set! fd-write-table fd "")

    ;; update epoll to watch for a read event on this fd
    (##epoll#epoll_ctl epfd _EPOLL_CTL_MOD fd _READ))

(define (read-handler fd)
    ;; epoll tells us to read from socket
    (let* ((len 4096)
           (buf (make-string len)))
        (let loop ((rbytes 0))
            (unless (= rbytes len)
                (let ((res (##net#read fd buf (- len rbytes))))
                    (if (= res 0)
                        (begin
                            ;; remove fd from epoll and close socket
                            (##epoll#epoll_ctl epfd _EPOLL_CTL_DEL fd 0)
                            (##net#close fd))
                        (unless (string-index  buf #\newline)
                            ;; keep reading if no newline
                            (loop (+ rbytes res)))))))

        (let ((i (string-index buf #\newline)))
            (unless (eq? i #f)
                (send-to-client fd (substring buf 0 (+ i 1)))
                ;; update epoll to watch for a write event on this fd
                (##epoll#epoll_ctl epfd _EPOLL_CTL_MOD fd _WRITE)))))

(define (fd-event-list-handler ls)
    ;; takes a list of (fd . events) pairs
    (if (eq? ls '())
        '()
        (let* ((pair (car ls))
               (sfd (tcp-listener-fileno listener))
               (fd (car pair)))
            (if (eq? sfd fd)
                (accept-fd sfd)
                (cond ((= (bitwise-and (cdr pair) _WRITE) _WRITE)
                        (write-handler fd))

                      ((= (bitwise-and (cdr pair) _READ) _READ)
                        (read-handler fd))))

            ;; loop over rest of (fd . events) list of pairs
            (fd-event-list-handler (cdr ls)))))