ttrivial-garbage.lisp - clic - Clic is an command line interactive client for gopher written in Common LISP
(HTM) git clone git://bitreich.org/clic/ git://hg6vgqziawt5s4dj.onion/clic/
(DIR) Log
(DIR) Files
(DIR) Refs
(DIR) Tags
(DIR) LICENSE
---
ttrivial-garbage.lisp (15356B)
---
1 ;;;; -*- Mode: lisp; indent-tabs-mode: nil -*-
2 ;;;
3 ;;; trivial-garbage.lisp --- Trivial Garbage!
4 ;;;
5 ;;; This software is placed in the public domain by Luis Oliveira
6 ;;; <loliveira@common-lisp.net> and is provided with absolutely no
7 ;;; warranty.
8
9 #+xcvb (module ())
10
11 (defpackage #:trivial-garbage
12 (:use #:cl)
13 (:shadow #:make-hash-table)
14 (:nicknames #:tg)
15 (:export #:gc
16 #:make-weak-pointer
17 #:weak-pointer-value
18 #:weak-pointer-p
19 #:make-weak-hash-table
20 #:hash-table-weakness
21 #:finalize
22 #:cancel-finalization)
23 (:documentation
24 "@a[http://common-lisp.net/project/trivial-garbage]{trivial-garbage}
25 provides a portable API to finalizers, weak hash-tables and weak
26 pointers on all major implementations of the Common Lisp
27 programming language. For a good introduction to these
28 data-structures, have a look at
29 @a[http://www.haible.de/bruno/papers/cs/weak/WeakDatastructures-writeup.html]{Weak
30 References: Data Types and Implementation} by Bruno Haible.
31
32 Source code is available at
33 @a[https://github.com/trivial-garbage/trivial-garbage]{github},
34 which you are welcome to use for submitting patches and/or
35 @a[https://github.com/trivial-garbage/trivial-garbage/issues]{bug
36 reports}. Discussion takes place on
37 @a[http://lists.common-lisp.net/cgi-bin/mailman/listinfo/trivial-garbage-devel]{trivial-garbage-devel
38 at common-lisp.net}.
39
40 @a[http://common-lisp.net/project/trivial-garbage/releases/]{Tarball
41 releases} are available, but the easiest way to install this
42 library is via @a[http://www.quicklisp.org/]{Quicklisp}:
43 @code{(ql:quickload :trivial-garbage)}.
44
45 @begin[Weak Pointers]{section}
46 A @em{weak pointer} holds an object in a way that does not prevent
47 it from being reclaimed by the garbage collector. An object
48 referenced only by weak pointers is considered unreachable (or
49 \"weakly reachable\") and so may be collected at any time. When
50 that happens, the weak pointer's value becomes @code{nil}.
51
52 @aboutfun{make-weak-pointer}
53 @aboutfun{weak-pointer-value}
54 @aboutfun{weak-pointer-p}
55 @end{section}
56
57 @begin[Weak Hash-Tables]{section}
58 A @em{weak hash-table} is one that weakly references its keys
59 and/or values. When both key and value are unreachable (or weakly
60 reachable) that pair is reclaimed by the garbage collector.
61
62 @aboutfun{make-weak-hash-table}
63 @aboutfun{hash-table-weakness}
64 @end{section}
65
66 @begin[Finalizers]{section}
67 A @em{finalizer} is a hook that is executed after a given object
68 has been reclaimed by the garbage collector.
69
70 @aboutfun{finalize}
71 @aboutfun{cancel-finalization}
72 @end{section}"))
73
74 (in-package #:trivial-garbage)
75
76 ;;;; GC
77
78 (defun gc (&key full verbose)
79 "Initiates a garbage collection. @code{full} forces the collection
80 of all generations, when applicable. When @code{verbose} is
81 @em{true}, diagnostic information about the collection is printed
82 if possible."
83 (declare (ignorable verbose full))
84 #+(or cmu scl) (ext:gc :verbose verbose :full full)
85 #+sbcl (sb-ext:gc :full full)
86 #+allegro (excl:gc (not (null full)))
87 #+(or abcl clisp) (ext:gc)
88 #+ecl (si:gc t)
89 #+openmcl (ccl:gc)
90 #+corman (ccl:gc (if full 3 0))
91 #+lispworks (hcl:gc-generation (if full t 0))
92 #+clasp (gctools:garbage-collect))
93
94 ;;;; Weak Pointers
95
96 #+openmcl
97 (defvar *weak-pointers* (cl:make-hash-table :test 'eq :weak :value)
98 "Weak value hash-table mapping between pseudo weak pointers and its values.")
99
100 #+(or allegro openmcl lispworks)
101 (defstruct (weak-pointer (:constructor %make-weak-pointer))
102 #-openmcl pointer)
103
104 (defun make-weak-pointer (object)
105 "Creates a new weak pointer which points to @code{object}. For
106 portability reasons, @code{object} must not be @code{nil}."
107 (assert (not (null object)))
108 #+sbcl (sb-ext:make-weak-pointer object)
109 #+(or cmu scl) (ext:make-weak-pointer object)
110 #+clisp (ext:make-weak-pointer object)
111 #+abcl (ext:make-weak-reference object)
112 #+ecl (ext:make-weak-pointer object)
113 #+allegro
114 (let ((wv (excl:weak-vector 1)))
115 (setf (svref wv 0) object)
116 (%make-weak-pointer :pointer wv))
117 #+openmcl
118 (let ((wp (%make-weak-pointer)))
119 (setf (gethash wp *weak-pointers*) object)
120 wp)
121 #+corman (ccl:make-weak-pointer object)
122 #+lispworks
123 (let ((array (make-array 1 :weak t)))
124 (setf (svref array 0) object)
125 (%make-weak-pointer :pointer array))
126 #+clasp (core:make-weak-pointer object))
127
128 #-(or allegro openmcl lispworks)
129 (defun weak-pointer-p (object)
130 "Returns @em{true} if @code{object} is a weak pointer and @code{nil}
131 otherwise."
132 #+sbcl (sb-ext:weak-pointer-p object)
133 #+(or cmu scl) (ext:weak-pointer-p object)
134 #+clisp (ext:weak-pointer-p object)
135 #+abcl (typep object 'ext:weak-reference)
136 #+ecl (typep object 'ext:weak-pointer)
137 #+corman (ccl:weak-pointer-p object)
138 #+clasp (core:weak-pointer-valid object))
139
140 (defun weak-pointer-value (weak-pointer)
141 "If @code{weak-pointer} is valid, returns its value. Otherwise,
142 returns @code{nil}."
143 #+sbcl (values (sb-ext:weak-pointer-value weak-pointer))
144 #+(or cmu scl) (values (ext:weak-pointer-value weak-pointer))
145 #+clisp (values (ext:weak-pointer-value weak-pointer))
146 #+abcl (values (ext:weak-reference-value weak-pointer))
147 #+ecl (values (ext:weak-pointer-value weak-pointer))
148 #+allegro (svref (weak-pointer-pointer weak-pointer) 0)
149 #+openmcl (values (gethash weak-pointer *weak-pointers*))
150 #+corman (ccl:weak-pointer-obj weak-pointer)
151 #+lispworks (svref (weak-pointer-pointer weak-pointer) 0)
152 #+clasp (core:weak-pointer-value weak-pointer))
153
154 ;;;; Weak Hash-tables
155
156 ;;; Allegro can apparently create weak hash-tables with both weak keys
157 ;;; and weak values but it's not obvious whether it's an OR or an AND
158 ;;; relation. TODO: figure that out.
159
160 (defun weakness-keyword-arg (weakness)
161 (declare (ignorable weakness))
162 #+(or sbcl abcl clasp ecl-weak-hash) :weakness
163 #+(or clisp openmcl) :weak
164 #+lispworks :weak-kind
165 #+allegro (case weakness (:key :weak-keys) (:value :values))
166 #+cmu :weak-p)
167
168 (defvar *weakness-warnings* '()
169 "List of weaknesses that have already been warned about this
170 session. Used by `weakness-missing'.")
171
172 (defun weakness-missing (weakness errorp)
173 "Signal an error or warning, depending on ERRORP, about lack of Lisp
174 support for WEAKNESS."
175 (cond (errorp
176 (error "Your Lisp does not support weak ~(~A~) hash-tables."
177 weakness))
178 ((member weakness *weakness-warnings*) nil)
179 (t (push weakness *weakness-warnings*)
180 (warn "Your Lisp does not support weak ~(~A~) hash-tables."
181 weakness))))
182
183 (defun weakness-keyword-opt (weakness errorp)
184 (declare (ignorable errorp))
185 (ecase weakness
186 (:key
187 #+(or lispworks sbcl abcl clasp clisp openmcl ecl-weak-hash) :key
188 #+(or allegro cmu) t
189 #-(or lispworks sbcl abcl clisp openmcl allegro cmu ecl-weak-hash clasp)
190 (weakness-missing weakness errorp))
191 (:value
192 #+allegro :weak
193 #+(or clisp openmcl sbcl abcl lispworks cmu ecl-weak-hash) :value
194 #-(or allegro clisp openmcl sbcl abcl lispworks cmu ecl-weak-hash clasp)
195 (weakness-missing weakness errorp))
196 (:key-or-value
197 #+(or clisp sbcl abcl cmu) :key-or-value
198 #+lispworks :either
199 #-(or clisp sbcl abcl lispworks cmu clasp)
200 (weakness-missing weakness errorp))
201 (:key-and-value
202 #+(or clisp abcl sbcl cmu ecl-weak-hash) :key-and-value
203 #+lispworks :both
204 #-(or clisp sbcl abcl lispworks cmu ecl-weak-hash clasp)
205 (weakness-missing weakness errorp))))
206
207 (defun make-weak-hash-table (&rest args &key weakness (weakness-matters t)
208 #+openmcl (test #'eql)
209 &allow-other-keys)
210 "Returns a new weak hash table. In addition to the standard
211 arguments accepted by @code{cl:make-hash-table}, this function adds
212 extra keywords: @code{:weakness} being the kind of weak table it
213 should create, and @code{:weakness-matters} being whether an error
214 should be signalled when that weakness isn't available (the default
215 is to signal an error). @code{weakness} can be one of @code{:key},
216 @code{:value}, @code{:key-or-value}, @code{:key-and-value}.
217
218 If @code{weakness} is @code{:key} or @code{:value}, an entry is
219 kept as long as its key or value is reachable, respectively. If
220 @code{weakness} is @code{:key-or-value} or @code{:key-and-value},
221 an entry is kept if either or both of its key and value are
222 reachable, respectively.
223
224 @code{tg::make-hash-table} is available as an alias for this
225 function should you wish to import it into your package and shadow
226 @code{cl:make-hash-table}."
227 (remf args :weakness)
228 (remf args :weakness-matters)
229 (if weakness
230 (let ((arg (weakness-keyword-arg weakness))
231 (opt (weakness-keyword-opt weakness weakness-matters)))
232 (apply #'cl:make-hash-table
233 #+openmcl :test #+openmcl (if (eq opt :key) #'eq test)
234 (if arg
235 (list* arg opt args)
236 args)))
237 (apply #'cl:make-hash-table args)))
238
239 ;;; If you want to use this function to override CL:MAKE-HASH-TABLE,
240 ;;; it's necessary to shadow-import it. For example:
241 ;;;
242 ;;; (defpackage #:foo
243 ;;; (:use #:common-lisp #:trivial-garbage)
244 ;;; (:shadowing-import-from #:trivial-garbage #:make-hash-table))
245 ;;;
246 (defun make-hash-table (&rest args)
247 (apply #'make-weak-hash-table args))
248
249 (defun hash-table-weakness (ht)
250 "Returns one of @code{nil}, @code{:key}, @code{:value},
251 @code{:key-or-value} or @code{:key-and-value}."
252 #-(or allegro sbcl abcl clisp cmu openmcl lispworks
253 ecl-weak-hash clasp)
254 (declare (ignore ht))
255 ;; keep this first if any of the other lisps bugously insert a NIL
256 ;; for the returned (values) even when *read-suppress* is NIL (e.g. clisp)
257 #.(if (find :sbcl *features*)
258 (if (find-symbol "HASH-TABLE-WEAKNESS" "SB-EXT")
259 (read-from-string "(sb-ext:hash-table-weakness ht)")
260 nil)
261 (values))
262 #+abcl (sys:hash-table-weakness ht)
263 #+ecl-weak-hash (ext:hash-table-weakness ht)
264 #+allegro (cond ((excl:hash-table-weak-keys ht) :key)
265 ((eq (excl:hash-table-values ht) :weak) :value))
266 #+clisp (ext:hash-table-weak-p ht)
267 #+cmu (let ((weakness (lisp::hash-table-weak-p ht)))
268 (if (eq t weakness) :key weakness))
269 #+openmcl (ccl::hash-table-weak-p ht)
270 #+lispworks (system::hash-table-weak-kind ht)
271 #+clasp (core:hash-table-weakness ht))
272
273 ;;;; Finalizers
274
275 ;;; Note: Lispworks can't finalize gensyms.
276
277 #+(or allegro clisp lispworks openmcl)
278 (defvar *finalizers*
279 (cl:make-hash-table :test 'eq
280 #+allegro :weak-keys #+:allegro t
281 #+(or clisp openmcl) :weak
282 #+lispworks :weak-kind
283 #+(or clisp openmcl lispworks) :key
284 #+clasp :weakness #+clasp :key)
285 "Weak hashtable that holds registered finalizers.")
286
287 #+corman
288 (progn
289 (defvar *finalizers* '()
290 "Weak alist that holds registered finalizers.")
291
292 (defvar *finalizers-cs* (threads:allocate-critical-section)))
293
294 #+lispworks
295 (progn
296 (hcl:add-special-free-action 'free-action)
297 (defun free-action (object)
298 (let ((finalizers (gethash object *finalizers*)))
299 (unless (null finalizers)
300 (mapc #'funcall finalizers)))))
301
302 (defun finalize (object function)
303 "Pushes a new @code{function} to the @code{object}'s list of
304 finalizers. @code{function} should take no arguments. Returns
305 @code{object}.
306
307 @b{Note:} @code{function} should not attempt to look at
308 @code{object} by closing over it because that will prevent it from
309 being garbage collected."
310 #+(or cmu scl) (ext:finalize object function)
311 #+sbcl (sb-ext:finalize object function)
312 #+abcl (ext:finalize object function)
313 #+ecl (let ((next-fn (ext:get-finalizer object)))
314 (ext:set-finalizer
315 object (lambda (obj)
316 (declare (ignore obj))
317 (funcall function)
318 (when next-fn
319 (funcall next-fn nil)))))
320 #+allegro
321 (progn
322 (push (excl:schedule-finalization
323 object (lambda (obj) (declare (ignore obj)) (funcall function)))
324 (gethash object *finalizers*))
325 object)
326 #+clasp (gctools:finalize object function)
327 #+clisp
328 ;; The CLISP code used to be a bit simpler but we had to workaround
329 ;; a bug regarding the interaction between GC and weak hashtables.
330 ;; See <http://article.gmane.org/gmane.lisp.clisp.general/11028>
331 ;; and <http://article.gmane.org/gmane.lisp.cffi.devel/994>.
332 (multiple-value-bind (finalizers presentp)
333 (gethash object *finalizers* (cons 'finalizers nil))
334 (unless presentp
335 (setf (gethash object *finalizers*) finalizers)
336 (ext:finalize object (lambda (obj)
337 (declare (ignore obj))
338 (mapc #'funcall (cdr finalizers)))))
339 (push function (cdr finalizers))
340 object)
341 #+openmcl
342 (progn
343 (ccl:terminate-when-unreachable
344 object (lambda (obj) (declare (ignore obj)) (funcall function)))
345 ;; store number of finalizers
346 (incf (gethash object *finalizers* 0))
347 object)
348 #+corman
349 (flet ((get-finalizers (obj)
350 (assoc obj *finalizers* :test #'eq :key #'ccl:weak-pointer-obj)))
351 (threads:with-synchronization *finalizers-cs*
352 (let ((pair (get-finalizers object)))
353 (if (null pair)
354 (push (list (ccl:make-weak-pointer object) function) *finalizers*)
355 (push function (cdr pair)))))
356 (ccl:register-finalization
357 object (lambda (obj)
358 (threads:with-synchronization *finalizers-cs*
359 (mapc #'funcall (cdr (get-finalizers obj)))
360 (setq *finalizers*
361 (delete obj *finalizers*
362 :test #'eq :key #'ccl:weak-pointer-obj)))))
363 object)
364 #+lispworks
365 (progn
366 (let ((finalizers (gethash object *finalizers*)))
367 (unless finalizers
368 (hcl:flag-special-free-action object))
369 (setf (gethash object *finalizers*)
370 (cons function finalizers)))
371 object))
372
373 (defun cancel-finalization (object)
374 "Cancels all of @code{object}'s finalizers, if any."
375 #+cmu (ext:cancel-finalization object)
376 #+scl (ext:cancel-finalization object nil)
377 #+sbcl (sb-ext:cancel-finalization object)
378 #+abcl (ext:cancel-finalization object)
379 #+ecl (ext:set-finalizer object nil)
380 #+allegro
381 (progn
382 (mapc #'excl:unschedule-finalization
383 (gethash object *finalizers*))
384 (remhash object *finalizers*))
385 #+clasp (gctools:definalize object)
386 #+clisp
387 (multiple-value-bind (finalizers present-p)
388 (gethash object *finalizers*)
389 (when present-p
390 (setf (cdr finalizers) nil))
391 (remhash object *finalizers*))
392 #+openmcl
393 (let ((count (gethash object *finalizers*)))
394 (unless (null count)
395 (dotimes (i count)
396 (ccl:cancel-terminate-when-unreachable object))))
397 #+corman
398 (threads:with-synchronization *finalizers-cs*
399 (setq *finalizers*
400 (delete object *finalizers* :test #'eq :key #'ccl:weak-pointer-obj)))
401 #+lispworks
402 (progn
403 (remhash object *finalizers*)
404 (hcl:flag-not-special-free-action object)))