slime Coonection part

;;;; Connections
;;;
;;; Connection structures represent the network connections between
;;; Emacs and Lisp. Each has a socket stream, a set of user I/O
;;; streams that redirect to Emacs, and optionally a second socket
;;; used solely to pipe user-output to Emacs (an optimization).  This
;;; is also the place where we keep everything that needs to be
;;; freed/closed/killed when we disconnect.

(defstruct (connection
             (:constructor %make-connection)
             (:conc-name connection.)
             (:print-function print-connection))
  ;; The listening socket. (usually closed)
  (socket           (missing-arg) :type t :read-only t)
  ;; Character I/O stream of socket connection.  Read-only to avoid
  ;; race conditions during initialization.
  (socket-io        (missing-arg) :type stream :read-only t)
  ;; Optional dedicated output socket (backending `user-output' slot).
  ;; Has a slot so that it can be closed with the connection.
  (dedicated-output nil :type (or stream null))
  ;; Streams that can be used for user interaction, with requests
  ;; redirected to Emacs.
  (user-input       nil :type (or stream null))
  (user-output      nil :type (or stream null))
  (user-io          nil :type (or stream null))
  ;; Bindings used for this connection (usually streams)
  (env '() :type list)
  ;; A stream that we use for *trace-output*; if nil, we user user-output.
  (trace-output     nil :type (or stream null))
  ;; A stream where we send REPL results.
  (repl-results     nil :type (or stream null))
  ;; Cache of macro-indentation information that has been sent to Emacs.
  ;; This is used for preparing deltas to update Emacs's knowledge.
  ;; Maps: symbol -> indentation-specification
  (indentation-cache (make-hash-table :test 'eq) :type hash-table)
  ;; The list of packages represented in the cache:
  (indentation-cache-packages '())
  ;; The communication style used.
  (communication-style nil :type (member nil :spawn :sigio :fd-handler))
  )

(defun print-connection (conn stream depth)
  (declare (ignore depth))
  (print-unreadable-object (conn stream :type t :identity t)))

(defstruct (singlethreaded-connection (:include connection)
                                      (:conc-name sconn.))
  ;; The SIGINT handler we should restore when the connection is
  ;; closed.
  saved-sigint-handler
  ;; A queue of events.  Not all events can be processed in order and
  ;; we need a place to stored them.
  (event-queue '() :type list)
  ;; A counter that is incremented whenever an event is added to the
  ;; queue.  This is used to detected modifications to the event queue
  ;; by interrupts.  The counter wraps around.
  (events-enqueued 0 :type fixnum))

(defstruct (multithreaded-connection (:include connection)
                                     (:conc-name mconn.))
  ;; In multithreaded systems we delegate certain tasks to specific
  ;; threads. The `reader-thread' is responsible for reading network
  ;; requests from Emacs and sending them to the `control-thread'; the
  ;; `control-thread' is responsible for dispatching requests to the
  ;; threads that should handle them; the `repl-thread' is the one
  ;; that evaluates REPL expressions. The control thread dispatches
  ;; all REPL evaluations to the REPL thread and for other requests it
  ;; spawns new threads.
  reader-thread
  control-thread
  repl-thread
  auto-flush-thread
  indentation-cache-thread
  ;; List of threads that are currently processing requests.  We use
  ;; this to find the newest/current thread for an interrupt.  In the
  ;; future we may store here (thread . request-tag) pairs so that we
  ;; can interrupt specific requests.
  (active-threads '() :type list)
  )

(defvar *emacs-connection* nil
  "The connection to Emacs currently in use.")

(defun make-connection (socket stream style)
  (let ((conn (funcall (ecase style
                         (:spawn
                          #'make-multithreaded-connection)
                         ((:sigio nil :fd-handler)
                          #'make-singlethreaded-connection))
                       :socket socket
                       :socket-io stream
                       :communication-style style)))
    (run-hook *new-connection-hook* conn)
    (send-to-sentinel `(:add-connection ,conn))
    conn))

(defslimefun ping (tag)
  tag)

(defun safe-backtrace ()
  (ignore-errors
    (call-with-debugging-environment
     (lambda () (backtrace 0 nil)))))

(define-condition swank-error (error)
  ((backtrace :initarg :backtrace :reader swank-error.backtrace)
   (condition :initarg :condition :reader swank-error.condition))
  (:report (lambda (c s) (princ (swank-error.condition c) s)))
  (:documentation "Condition which carries a backtrace."))

(defun signal-swank-error (condition &optional (backtrace (safe-backtrace)))
  (error 'swank-error :condition condition :backtrace backtrace))

(defvar *debug-on-swank-protocol-error* nil
  "When non-nil invoke the system debugger on errors that were
signalled during decoding/encoding the wire protocol.  Do not set this
to T unless you want to debug swank internals.")

(defmacro with-swank-error-handler ((connection) &body body)
  "Close the connection on internal `swank-error's."
  (let ((conn (gensym)))
  `(let ((,conn ,connection))
     (handler-case
         (handler-bind ((swank-error
                         (lambda (condition)
                           (when *debug-on-swank-protocol-error*
                             (invoke-default-debugger condition)))))
           (progn . ,body))
       (swank-error (condition)
         (close-connection ,conn
                           (swank-error.condition condition)
                           (swank-error.backtrace condition)))))))

(defmacro with-panic-handler ((connection) &body body)
  "Close the connection on unhandled `serious-condition's."
  (let ((conn (gensym)))
    `(let ((,conn ,connection))
       (handler-bind ((serious-condition
                        (lambda (condition)
                          (close-connection ,conn condition (safe-backtrace))
                          (abort condition))))
         . ,body))))

(add-hook *new-connection-hook* 'notify-backend-of-connection)
(defun notify-backend-of-connection (connection)
  (declare (ignore connection))
  (emacs-connected))