3rdparties/software/trivial-garbage-20200325-git/trivial-garbage.lisp (15981 bytes)
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) 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) 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) 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 #+clasp :test #+clasp #'eq 235 (if arg 236 (list* arg opt args) 237 args))) 238 (apply #'cl:make-hash-table args))) 239 240 ;;; If you want to use this function to override CL:MAKE-HASH-TABLE, 241 ;;; it's necessary to shadow-import it. For example: 242 ;;; 243 ;;; (defpackage #:foo 244 ;;; (:use #:common-lisp #:trivial-garbage) 245 ;;; (:shadowing-import-from #:trivial-garbage #:make-hash-table)) 246 ;;; 247 (defun make-hash-table (&rest args) 248 (apply #'make-weak-hash-table args)) 249 250 (defun hash-table-weakness (ht) 251 "Returns one of @code{nil}, @code{:key}, @code{:value}, 252 @code{:key-or-value} or @code{:key-and-value}." 253 #-(or allegro sbcl abcl clisp cmu openmcl lispworks 254 ecl-weak-hash clasp) 255 (declare (ignore ht)) 256 ;; keep this first if any of the other lisps bugously insert a NIL 257 ;; for the returned (values) even when *read-suppress* is NIL (e.g. clisp) 258 #.(if (find :sbcl *features*) 259 (if (find-symbol "HASH-TABLE-WEAKNESS" "SB-EXT") 260 (read-from-string "(sb-ext:hash-table-weakness ht)") 261 nil) 262 (values)) 263 #+abcl (sys:hash-table-weakness ht) 264 #+ecl-weak-hash (ext:hash-table-weakness ht) 265 #+allegro (cond ((excl:hash-table-weak-keys ht) :key) 266 ((eq (excl:hash-table-values ht) :weak) :value)) 267 #+clisp (ext:hash-table-weak-p ht) 268 #+cmu (let ((weakness (lisp::hash-table-weak-p ht))) 269 (if (eq t weakness) :key weakness)) 270 #+openmcl (ccl::hash-table-weak-p ht) 271 #+lispworks (system::hash-table-weak-kind ht) 272 #+clasp (core:hash-table-weakness ht)) 273 274 ;;;; Finalizers 275 276 ;;; Note: Lispworks can't finalize gensyms. 277 278 #+(or allegro clisp lispworks openmcl) 279 (defvar *finalizers* 280 (cl:make-hash-table :test 'eq 281 #+allegro :weak-keys #+:allegro t 282 #+(or clisp openmcl) :weak 283 #+lispworks :weak-kind 284 #+(or clisp openmcl lispworks) :key 285 #+clasp :weakness #+clasp :key) 286 "Weak hashtable that holds registered finalizers.") 287 288 #+corman 289 (progn 290 (defvar *finalizers* '() 291 "Weak alist that holds registered finalizers.") 292 293 (defvar *finalizers-cs* (threads:allocate-critical-section))) 294 295 #+lispworks 296 (progn 297 (hcl:add-special-free-action 'free-action) 298 (defun free-action (object) 299 (let ((finalizers (gethash object *finalizers*))) 300 (unless (null finalizers) 301 (mapc #'funcall finalizers))))) 302 303 ;;; Note: ECL bytecmp does not perform escape analysis and unused 304 ;;; variables are not optimized away from its lexenv. That leads to 305 ;;; closing over whole definition lexenv. That's why we define 306 ;;; EXTEND-FINALIZER-FN which defines lambda outside the lexical scope 307 ;;; of FINALIZE (which inludes object) - to prevent closing over 308 ;;; finalized object. This problem does not apply to C compiler. 309 310 #+ecl 311 (defun extend-finalizer-fn (old-fn new-fn) 312 (if (null old-fn) 313 (lambda (obj) 314 (declare (ignore obj)) 315 (funcall new-fn)) 316 (lambda (obj) 317 (declare (ignore obj)) 318 (funcall new-fn) 319 (funcall old-fn nil)))) 320 321 (defun finalize (object function) 322 "Pushes a new @code{function} to the @code{object}'s list of 323 finalizers. @code{function} should take no arguments. Returns 324 @code{object}. 325 326 @b{Note:} @code{function} should not attempt to look at 327 @code{object} by closing over it because that will prevent it from 328 being garbage collected." 329 #+(or cmu scl) (ext:finalize object function) 330 #+sbcl (sb-ext:finalize object function) 331 #+abcl (ext:finalize object function) 332 #+ecl (let* ((old-fn (ext:get-finalizer object)) 333 (new-fn (extend-finalizer-fn old-fn function))) 334 (ext:set-finalizer object new-fn) 335 object) 336 #+allegro 337 (progn 338 (push (excl:schedule-finalization 339 object (lambda (obj) (declare (ignore obj)) (funcall function))) 340 (gethash object *finalizers*)) 341 object) 342 #+clasp (gctools:finalize object (lambda (obj) (declare (ignore obj)) (funcall function))) 343 #+clisp 344 ;; The CLISP code used to be a bit simpler but we had to workaround 345 ;; a bug regarding the interaction between GC and weak hashtables. 346 ;; See <http://article.gmane.org/gmane.lisp.clisp.general/11028> 347 ;; and <http://article.gmane.org/gmane.lisp.cffi.devel/994>. 348 (multiple-value-bind (finalizers presentp) 349 (gethash object *finalizers* (cons 'finalizers nil)) 350 (unless presentp 351 (setf (gethash object *finalizers*) finalizers) 352 (ext:finalize object (lambda (obj) 353 (declare (ignore obj)) 354 (mapc #'funcall (cdr finalizers))))) 355 (push function (cdr finalizers)) 356 object) 357 #+openmcl 358 (progn 359 (ccl:terminate-when-unreachable 360 object (lambda (obj) (declare (ignore obj)) (funcall function))) 361 ;; store number of finalizers 362 (incf (gethash object *finalizers* 0)) 363 object) 364 #+corman 365 (flet ((get-finalizers (obj) 366 (assoc obj *finalizers* :test #'eq :key #'ccl:weak-pointer-obj))) 367 (threads:with-synchronization *finalizers-cs* 368 (let ((pair (get-finalizers object))) 369 (if (null pair) 370 (push (list (ccl:make-weak-pointer object) function) *finalizers*) 371 (push function (cdr pair))))) 372 (ccl:register-finalization 373 object (lambda (obj) 374 (threads:with-synchronization *finalizers-cs* 375 (mapc #'funcall (cdr (get-finalizers obj))) 376 (setq *finalizers* 377 (delete obj *finalizers* 378 :test #'eq :key #'ccl:weak-pointer-obj))))) 379 object) 380 #+lispworks 381 (progn 382 (let ((finalizers (gethash object *finalizers*))) 383 (unless finalizers 384 (hcl:flag-special-free-action object)) 385 (setf (gethash object *finalizers*) 386 (cons function finalizers))) 387 object)) 388 389 (defun cancel-finalization (object) 390 "Cancels all of @code{object}'s finalizers, if any." 391 #+cmu (ext:cancel-finalization object) 392 #+scl (ext:cancel-finalization object nil) 393 #+sbcl (sb-ext:cancel-finalization object) 394 #+abcl (ext:cancel-finalization object) 395 #+ecl (ext:set-finalizer object nil) 396 #+allegro 397 (progn 398 (mapc #'excl:unschedule-finalization 399 (gethash object *finalizers*)) 400 (remhash object *finalizers*)) 401 #+clasp (gctools:definalize object) 402 #+clisp 403 (multiple-value-bind (finalizers present-p) 404 (gethash object *finalizers*) 405 (when present-p 406 (setf (cdr finalizers) nil)) 407 (remhash object *finalizers*)) 408 #+openmcl 409 (let ((count (gethash object *finalizers*))) 410 (unless (null count) 411 (dotimes (i count) 412 (ccl:cancel-terminate-when-unreachable object)))) 413 #+corman 414 (threads:with-synchronization *finalizers-cs* 415 (setq *finalizers* 416 (delete object *finalizers* :test #'eq :key #'ccl:weak-pointer-obj))) 417 #+lispworks 418 (progn 419 (remhash object *finalizers*) 420 (hcl:flag-not-special-free-action object)))