(cd (pack (sys "HOME") "/picolisp"))
(load (pack (sys "HOME") "/src/picolisp/nb.l"))

# (out "/tmp/a" (wrx '(1 2 3 4) 4))
# (out "/tmp/a" (wrx '(1 2 3 4) 3 1))

# (setq *B (need 5))
# (in "/tmp/a" (rdx *B 3))
# (in "/tmp/a" (rdx *B 2 3))
# *B

# non-blocking echo server

(setq *N 5) # try bigger buffer;-)
(setq *B (need *N))
(setq *I 0)
(setq *J 0)

(set 'EAGAIN (eagain))

(de _rdx (Sock)
   (in Sock
      (let? N (rdx *B (- *N *I) *I)
         (when (gt0 N)
            (inc '*I N))
         N)))

(de _wrx (Sock)
   (out Sock
      (let? N (wrx *B (- *I *J) *J)
         (when (gt0 N)
            (inc '*J N))
         N)))

(de callback (Sock)
   (let End NIL
      (prinl "callback " Sock " J=" *J " I=" *I " N=" *N)
      (block Sock NIL) # first time would be enough
      (unless End
         (let N (_rdx Sock)
            (prinl "  read " N)
            (unless (or (gt0 N) (= N 'EAGAIN))
               (setq End (cons rd N)))))
      (unless End
         (let N (_wrx Sock)
            (prinl "  written " N)
            (unless (or (gt0 N) (= N 'EAGAIN))
               (setq End (cons wr N)))))
      (when End
         (prinl "  finish")
         (task Sock)
         (close Sock))
      (when (<= *I *J)
         (prinl "  rotate J=" *J " I=" *I " N=" *N)
         (setq *I 0)
         (setq *J 0))
      (prinl "end " Sock " J=" *J " I=" *I " N=" *N)))

(task (port 4444)             # Listen on port 4444
   (when (accept @)           # A connect arrived
      (task @                 # Install another task on this socket
         Sock @               # Keep the socket in the task's env
            (callback Sock) ) ) )