mdw@git.distorted.org.uk Git - lisp/blob - weak.lisp

   1 ;;; -*-lisp-*-
   2 ;;;
   3 ;;; Weak pointers and data structures
   4 ;;;
   5 ;;; (c) 2008 Straylight/Edgeware
   6 ;;;
   7
   8 ;;;----- Licensing notice ---------------------------------------------------
   9 ;;;
  10 ;;; This program is free software; you can redistribute it and/or modify
  11 ;;; it under the terms of the GNU General Public License as published by
  12 ;;; the Free Software Foundation; either version 2 of the License, or
  13 ;;; (at your option) any later version.
  14 ;;;
  15 ;;; This program is distributed in the hope that it will be useful,
  16 ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;;; GNU General Public License for more details.
  19 ;;;
  20 ;;; You should have received a copy of the GNU General Public License
  21 ;;; along with this program; if not, write to the Free Software Foundation,
  22 ;;; Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  23
  24 (cl:defpackage #:weak
  25   (:use #:common-lisp)
  26   #+sbcl
  27     (:import-from #:sb-ext #:make-weak-pointer #:weak-pointer-value)
  28   #+(or cmu clisp)
  29     (:import-from #:ext #:make-weak-pointer #:weak-pointer-value)
  30   (:export #:make-weak-pointer #:weak-pointer-value))
  31 (cl:in-package #:weak)
  32
  33 #+(or allegro common-lispworks)
  34 (progn
  35   (defun make-weak-pointer (object)
  36     (make-array 1 :initial-contents (list object) :weak t))
  37   (defun weak-pointer-value (weak)
  38     (aref weak 0)))
  39
  40 #+ecl
  41 (progn
  42   (defun make-weak-pointer (object)
  43     (ffi:c-inline (object) (:object) :pointer-void
  44       "{ cl_object *weak = GC_malloc_atomic(sizeof(cl_object));
  45          *weak = #0;
  46          GC_general_register_disappearing_link(weak, GC_base(#0));
  47          @(return) = weak; }"
  48       :one-liner nil))
  49   (defun weak-pointer-value (weak)
  50     (ffi:c-inline (weak) (:pointer-void) (values :object :object)
  51       "{ cl_object *weak = #0;
  52          if (*weak) { @(return 0) = *weak; @(return 1) = @t; }
  53          else { @(return 0) = @nil; @(return 1) = @nil; } }"
  54       :one-liner nil)))
  55
  56 #-(or sbcl cmu clisp allegro common-lispworks ecl)
  57 (progn
  58   (defun make-weak-pointer (object) object)
  59   (defun weak-pointer-value (weak) (values weak t)))
  60
  61 ;;;----- That's all, folks --------------------------------------------------