[usocket-devel] wait-for-input fix for CLISP - usocket-devel - mailman3.common-lisp.net

10 Apr 2011


      Hello.
I am using usocket 0.5.0 and it has a bug for CLISP.
In the function wait-for-input-internal there is a do* cycle which analyzes
the result of the CLISP function socket-status
(its docs are here: http://www.clisp.org/impnotes/socket.html#so-status)
Here is how the cycle is written now:
(do* ((x (pop sockets) (pop sockets))
              (y (pop status-list) (pop status-list)))
             ((null x))
          (when (eq y :INPUT)
            (setf (state x) :READ)))
This cycle never recognizes that a server socket is ready to accept a connection.
The fixed cycle
(do* ((x (pop sockets) (pop sockets))
              (y (cdr (pop status-list)) (cdr (pop status-list)))) ; <- fixed here
             ((null x))
          (when (member y '(T :INPUT)) ; <- and here
            (setf (state x) :READ)))
The first mistake was that the code expects socket-status to return a list of statuses,
but it actually returns a list of cons cells, according to the doc:
...
If you want to avoid consing[3] up a fresh list, you can make the elements of 
socket-stream-or-list to be (socket-stream direction . x) or (socket-server . x). 
Then SOCKET:SOCKET-STATUS will destructively modify its argument and replace
x or NIL with the status and return the modified list.
The second mistake is that socket-status specifies ready SOCKET-SERVER as T
(and :INPUTS is for SOCKET-STREAM). As far as I understood usocket intention
for the wait-for-input-internal function, we should check both.
With these changes, I have hunchentoot 1.1.1 working with clisp 2.49.
Best regards,
- Anton