r11464: add signal handling functions

[kmrcl.git] / signals.lisp

diff --git a/signals.lisp b/signals.lisp
new file mode 100644 (file)
index 0000000..1547aba
--- /dev/null
+++ b/signals.lisp
@@ -0,0 +1,70 @@
+;;;; -*- Mode: Lisp; Syntax: ANSI-Common-Lisp; Base: 10; Package: modlisp -*-
+;;;; *************************************************************************
+;;;; FILE IDENTIFICATION
+;;;;
+;;;; Name:          signals.lisp
+;;;; Purpose:       Signal processing functions
+;;;; Programmer:    Kevin M. Rosenberg
+;;;; Date Started:  Jan 2007
+;;;;
+;;;; $Id: processes.lisp 10985 2006-07-26 18:52:03Z kevin $
+;;;; *************************************************************************
+
+(in-package #:kmrcl)
+
+(defun signal-key-to-number (sig)
+  "These signals and numbers are only valid on POSIX systems, perhaps
+some are Linux-specific."
+  (case sig
+    (:hup 1)
+    (:int 2)
+    (:quit 3)
+    (:kill 9)
+    (:usr1 10)
+    (:usr2 12)
+    (:pipe 13)
+    (:alrm 14)
+    (:term 15)
+    (t
+     (error "Signal ~A not known." sig))))
+
+
+(defun set-signal-handler (sig handler)
+  "Sets the handler for a signal to a function. Where possible, returns
+the old handler for the function for later restoration with remove-signal-handler
+below.
+
+To be portable, signal handlers should use (&rest dummy) function signatures
+and ignore the value. They should return T to tell some Lisp implementations (Allegro)
+that the signal was successfully handled."
+  (let ((signum (etypecase sig
+                  (integer sig)
+                  (keyword (signal-key-to-number sig)))))
+    #+allegro (excl:add-signal-handler signum handler)
+    #+cmu (system:enable-interrupt signum handler)
+    #+lispworks
+    ;; non-documented method to get old handler, works in lispworks 5
+    (let ((old-handler (when (and (boundp 'system::*signal-handler-functions*)
+                                  (typep system::*signal-handler-functions* 'array))
+                         (aref system::*signal-handler-functions* signum))))
+      (system:set-signal-handler signum handler)
+      old-handler)
+    #+sbcl (sb-sys:enable-interrupt signum handler)
+    #-(or allegro cmu lispworks sbcl) (warn "Signal setting not supported on this platform.")
+  ))
+
+(defun remove-signal-handler (sig &optional old-handler)
+  "Removes a handler from signal. Tries, when possible, to restore old-handler."
+  (let ((signum (etypecase sig
+                  (integer sig)
+                  (keyword (signal-key-to-number sig)))))
+    ;; allegro automatically restores old handler, because set-signal-handler above
+    ;; actually pushes the new handler onto a list of handlers
+    #+allegro (declare (ignore old-handler))
+    #+allegro (excl:remove-signal-handler signum)
+    #+cmu (system:enable-interrupt signum (or old-handler :default))
+    ;; lispworks removes handler if old-handler is nil
+    #+lispworks (system:set-signal-handler signum old-handler)
+    #+sbcl (sb-sys:enable-interrupt signum (or old-handler :default))
+    #-(or allegro cmu lispworks sbcl) (warn "Signal setting not supported on this platform.")
+    ))