[usocket-devel] with-* style macros for sockets

[Harold Lee]

Hi,

I've just started using usocket, and it is very nice. The first thing I 
did was to write a couple of helper macros for server-side socket 
handling, and I thought they might be worth including in the library:

(defmacro with-listener (socket-specs &rest body)
  "Listen for connections and clean up when done."
  (destructuring-bind (socket-var &rest socket-options) socket-specs
    (let ((var-name (gensym)))
      `(let* ((,var-name   (socket-listen , at socket-options))
              (,socket-var ,var-name))
        (unwind-protect (progn , at body)
          (socket-close ,var-name))))))

(defmacro with-client-stream (socket-specs &rest body)
  "Work with a client socket stream and clean up when done."
  (destructuring-bind (stream-var listener-var &rest socket-options)
      socket-specs
    (let ((var-name (gensym)))
      `(let* ((,var-name   (socket-accept ,listener-var , at socket-options))
              (,stream-var (socket-stream ,var-name)))
        (unwind-protect (progn , at body)
          (socket-close ,var-name))))))

They let you easily get started listening for connections and working 
with connected clients (partly because all you see are the listener 
socket and a stream for each client). e.g.

(defun handle-one-request ()
  (with-listener (listener "127.0.0.1" 40389)
    (with-client-stream (stream listener)
      (handle-request stream))))

-Harold