带有cl-usocket的通用lisp回波服务器

Question

我正在用普通的lisp尝试一个简单的echo服务器(我使用clisp)。我在Lisp中试过这个例子

CLISP版本(没有usocket)工作正常。

当我尝试usocket版本(带有clisp)时，我得到以下错误：

*-条件CDR：:INPUT不是发生的列表。

谢谢你的答复，迪米特里斯

Answer 1

我不确定答案，但我认为这可以追溯到wait-for-input和wait-for-input-internal.函数wait-for-input有以下定义(缩写)：

(defun wait-for-input (socket-or-sockets &key timeout ready-only)
  "Waits for one or more streams to become ready for reading from
the socket.  When `timeout' (a non-negative real number) is
specified, wait `timeout' seconds, or wait indefinitely when
it isn't specified.  A `timeout' value of 0 (zero) means polling. …"
  (unless (wait-list-p socket-or-sockets)
    (let ((wl (make-wait-list (if (listp socket-or-sockets)
                                  socket-or-sockets (list socket-or-sockets)))))
      (multiple-value-bind
            (socks to)
          (wait-for-input wl :timeout timeout :ready-only ready-only)
        (return-from wait-for-input
          (values (if ready-only socks socket-or-sockets) to)))))
  (let* ((start (get-internal-real-time))
         (sockets-ready 0))
    (dolist (x (wait-list-waiters socket-or-sockets))
      (when (setf (state x)
                  #+(and win32 (or sbcl ecl)) nil ; they cannot rely on LISTEN
                  #-(and win32 (or sbcl ecl))
                  (if (and (stream-usocket-p x)
                           (listen (socket-stream x)))
                      :read
                      nil))
        (incf sockets-ready)))
    ;; the internal routine is responsibe for
    ;; making sure the wait doesn't block on socket-streams of
    ;; which theready- socket isn't ready, but there's space left in the
    ;; buffer
    (wait-for-input-internal socket-or-sockets
                             :timeout (if (zerop sockets-ready) timeout 0))
    (let ((to-result (when timeout
                       (let ((elapsed (/ (- (get-internal-real-time) start)
                                         internal-time-units-per-second)))
                         (when (< elapsed timeout)
                           (- timeout elapsed))))))
      (values (if ready-only
                  (remove-if #'null (wait-list-waiters socket-or-sockets) :key #'state)
                  socket-or-sockets)
              to-result))))

请注意，最后一节使用

(wait-for-input-internal socket-or-sockets
                         :timeout (if (zerop sockets-ready) timeout 0))

现在，名称socket-or-sockets意味着它的值可能是一个套接字或一个套接字列表。但是，让我们看一下CLISP的wait-for-input-internal定义(它在backend/<implementation>.lisp中定义)：

(defmethod wait-for-input-internal (wait-list &key timeout)
  (with-mapped-conditions ()
    (multiple-value-bind
        (secs musecs)
        (split-timeout (or timeout 1))
      (dolist (x (wait-list-%wait wait-list))
        (setf (cdr x) :INPUT))
      (let* ((request-list (wait-list-%wait wait-list))
             (status-list (if timeout
                              (socket:socket-status request-list secs musecs)
                            (socket:socket-status request-list)))
             (sockets (wait-list-waiters wait-list)))
        (do* ((x (pop sockets) (pop sockets))
              (y (cdr (pop status-list)) (cdr (pop status-list))))
             ((null x))
          (when (member y '(T :INPUT))
            (setf (state x) :READ)))
        wait-list))))

有两种用法:输入。看来，等待列表中的每个元素都应该是其cdr包含某种状态的反式。也许wait-for-input是用一个套接字来调用的(毕竟，参数名是socket-or-sockets，，当调用wait-for-input-internal时，它需要一个列表。这可能导致后者在期待(<something> . :INPUT)时获得((<something . :INPUT))。不过我不确定。无论如何，错误来自于这里附近的某个地方。