;;;
;;; signal.scm - with-signal-handlers
;;;  
;;;   Copyright (c) 2000-2011  Shiro Kawai  <shiro@acm.org>
;;;   
;;;   Redistribution and use in source and binary forms, with or without
;;;   modification, are permitted provided that the following conditions
;;;   are met:
;;;   
;;;   1. Redistributions of source code must retain the above copyright
;;;      notice, this list of conditions and the following disclaimer.
;;;  
;;;   2. Redistributions in binary form must reproduce the above copyright
;;;      notice, this list of conditions and the following disclaimer in the
;;;      documentation and/or other materials provided with the distribution.
;;;  
;;;   3. Neither the name of the authors nor the names of its contributors
;;;      may be used to endorse or promote products derived from this
;;;      software without specific prior written permission.
;;;  
;;;   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
;;;   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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;; This file is to be autoloaded

(select-module gauche)
(use srfi-1)

;; (with-signal-handlers
;;   (clause ...)
;;   thunk)
;;
;; clause := (signals expr ...) or (signals => proc)
;; signals := an expr that evaluates to an integer, a list of integers or
;;            a sigset object
;; proc   := an expr that evaluates to a procedure that takes one arg

(define-syntax with-signal-handlers
  (syntax-rules (=>)
    ((_ "loop" () handlers thunk)
     (%with-signal-handlers (list . handlers) thunk))
    ((_ "loop" ((sigs => proc) . clauses) handlers thunk)
     (with-signal-handlers "loop" clauses
                           ((cons (%make-sigset sigs) proc) . handlers)
                           thunk))
    ((_ "loop" ((sigs expr ...) . clauses) handlers thunk)
     (with-signal-handlers "loop" clauses
                           ((cons (%make-sigset sigs) (lambda _ expr ...))
                            . handlers)
                           thunk))
    ((_ "loop" whatever handlers thunk)
     (syntax-error "bad clause in with-signal-handlers" whatever))
    ((_ (clause ...) thunk)
     (with-signal-handlers "loop" (clause ...) () thunk))
    ((_ . whatever)
     (syntax-error "malformed with-signal-handlers"
                   (with-signal-handlers . whatever)))
    ))

(define (%make-sigset signals)
  (cond
   ((is-a? signals <sys-sigset>) signals)
   ((or (integer? signals) (eq? signals #t))
    (sys-sigset-add! (make <sys-sigset>) signals))
   ((and (list? signals)
         (every integer? signals))
    (apply sys-sigset-add! (make <sys-sigset>) signals))
   (else
    (error "bad signal set" signals))))

(define (%with-signal-handlers handlers-alist thunk)
  (let ((ohandlers (get-signal-handlers)))
    (dynamic-wind
     (lambda ()
       (for-each (lambda (p) (set-signal-handler! (car p) (cdr p)))
                 handlers-alist))
     thunk
     (lambda ()
       (for-each (lambda (p) (set-signal-handler! (car p) (cdr p)))
                 ohandlers)))))


    
