1 /* Copyright (C) 1995, 1996, 1998, 2000, 2001, 2003, 2006, 2008, 2009, 2010,
2 * 2011, 2012 Free Software Foundation, Inc.
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public License
6 * as published by the Free Software Foundation; either version 3 of
7 * the License, or (at your option) any later version.
9 * This library is distributed in the hope that it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Lesser General Public License for more details.
14 * You should have received a copy of the GNU Lesser General Public
15 * License along with this library; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
28 #include "libguile/_scm.h"
29 #include "libguile/vectors.h"
30 #include "libguile/hashtab.h"
32 #include "libguile/validate.h"
33 #include "libguile/weaks.h"
35 #include "libguile/bdw-gc.h"
36 #include <gc/gc_typed.h>
40 /* Weak pairs for use in weak alist vectors and weak hash tables.
42 We have weal-car pairs, weak-cdr pairs, and doubly weak pairs. In weak
43 pairs, the weak component(s) are not scanned for pointers and are
44 registered as disapperaring links; therefore, the weak component may be
45 set to NULL by the garbage collector when no other reference to that word
46 exist. Thus, users should only access weak pairs via the
47 `SCM_WEAK_PAIR_C[AD]R ()' macros. See also `scm_fixup_weak_alist ()' in
50 /* Type descriptors for weak-c[ad]r pairs. */
51 static GC_descr wcar_pair_descr
, wcdr_pair_descr
;
55 scm_weak_car_pair (SCM car
, SCM cdr
)
59 cell
= (scm_t_cell
*)GC_malloc_explicitly_typed (sizeof (*cell
),
66 /* Weak car cells make sense iff the car is non-immediate. */
67 SCM_I_REGISTER_DISAPPEARING_LINK ((void **) &cell
->word_0
, SCM2PTR (car
));
69 return (SCM_PACK (cell
));
73 scm_weak_cdr_pair (SCM car
, SCM cdr
)
77 cell
= (scm_t_cell
*)GC_malloc_explicitly_typed (sizeof (*cell
),
84 /* Weak cdr cells make sense iff the cdr is non-immediate. */
85 SCM_I_REGISTER_DISAPPEARING_LINK ((void **) &cell
->word_1
, SCM2PTR (cdr
));
87 return (SCM_PACK (cell
));
91 scm_doubly_weak_pair (SCM car
, SCM cdr
)
93 /* Doubly weak cells shall not be scanned at all for pointers. */
94 scm_t_cell
*cell
= (scm_t_cell
*)scm_gc_malloc_pointerless (sizeof (*cell
),
101 SCM_I_REGISTER_DISAPPEARING_LINK ((void **) &cell
->word_0
, SCM2PTR (car
));
103 SCM_I_REGISTER_DISAPPEARING_LINK ((void **) &cell
->word_1
, SCM2PTR (cdr
));
105 return (SCM_PACK (cell
));
111 /* 1. The current hash table implementation in hashtab.c uses weak alist
112 * vectors (formerly called weak hash tables) internally.
114 * 2. All hash table operations still work on alist vectors.
116 * 3. The weak vector and alist vector Scheme API is accessed through
117 * the module (ice-9 weak-vector).
125 SCM_DEFINE (scm_make_weak_vector
, "make-weak-vector", 1, 1, 0,
126 (SCM size
, SCM fill
),
127 "Return a weak vector with @var{size} elements. If the optional\n"
128 "argument @var{fill} is given, all entries in the vector will be\n"
129 "set to @var{fill}. The default value for @var{fill} is the\n"
131 #define FUNC_NAME s_scm_make_weak_vector
133 return scm_i_make_weak_vector (0, size
, fill
);
138 SCM_REGISTER_PROC(s_list_to_weak_vector
, "list->weak-vector", 1, 0, 0, scm_weak_vector
);
140 SCM_DEFINE (scm_weak_vector
, "weak-vector", 0, 0, 1,
142 "@deffnx {Scheme Procedure} list->weak-vector l\n"
143 "Construct a weak vector from a list: @code{weak-vector} uses\n"
144 "the list of its arguments while @code{list->weak-vector} uses\n"
145 "its only argument @var{l} (a list) to construct a weak vector\n"
146 "the same way @code{list->vector} would.")
147 #define FUNC_NAME s_scm_weak_vector
149 return scm_i_make_weak_vector_from_list (0, l
);
154 SCM_DEFINE (scm_weak_vector_p
, "weak-vector?", 1, 0, 0,
156 "Return @code{#t} if @var{obj} is a weak vector. Note that all\n"
157 "weak hashes are also weak vectors.")
158 #define FUNC_NAME s_scm_weak_vector_p
160 return scm_from_bool (SCM_I_WVECTP (obj
) && !SCM_IS_WHVEC (obj
));
165 /* Weak alist vectors, i.e., vectors of alists.
167 The alist vector themselves are _not_ weak. The `car' (or `cdr', or both)
168 of the pairs within it are weak. See `hashtab.c' for details. */
171 /* FIXME: We used to have two implementations of weak hash tables: the one in
172 here and the one in `hashtab.c'. The difference is that weak alist
173 vectors could be used as vectors while (weak) hash tables can't. We need
176 SCM_DEFINE (scm_make_weak_key_alist_vector
, "make-weak-key-alist-vector", 0, 1, 0,
178 "@deffnx {Scheme Procedure} make-weak-value-alist-vector size\n"
179 "@deffnx {Scheme Procedure} make-doubly-weak-alist-vector size\n"
180 "Return a weak hash table with @var{size} buckets. As with any\n"
181 "hash table, choosing a good size for the table requires some\n"
184 "You can modify weak hash tables in exactly the same way you\n"
185 "would modify regular hash tables. (@pxref{Hash Tables})")
186 #define FUNC_NAME s_scm_make_weak_key_alist_vector
188 return scm_make_weak_key_hash_table (size
);
193 SCM_DEFINE (scm_make_weak_value_alist_vector
, "make-weak-value-alist-vector", 0, 1, 0,
195 "Return a hash table with weak values with @var{size} buckets.\n"
196 "(@pxref{Hash Tables})")
197 #define FUNC_NAME s_scm_make_weak_value_alist_vector
199 return scm_make_weak_value_hash_table (size
);
204 SCM_DEFINE (scm_make_doubly_weak_alist_vector
, "make-doubly-weak-alist-vector", 1, 0, 0,
206 "Return a hash table with weak keys and values with @var{size}\n"
207 "buckets. (@pxref{Hash Tables})")
208 #define FUNC_NAME s_scm_make_doubly_weak_alist_vector
210 return scm_make_doubly_weak_hash_table (size
);
215 SCM_DEFINE (scm_weak_key_alist_vector_p
, "weak-key-alist-vector?", 1, 0, 0,
217 "@deffnx {Scheme Procedure} weak-value-alist-vector? obj\n"
218 "@deffnx {Scheme Procedure} doubly-weak-alist-vector? obj\n"
219 "Return @code{#t} if @var{obj} is the specified weak hash\n"
220 "table. Note that a doubly weak hash table is neither a weak key\n"
221 "nor a weak value hash table.")
222 #define FUNC_NAME s_scm_weak_key_alist_vector_p
224 return scm_from_bool (SCM_I_WVECTP (obj
) && SCM_IS_WHVEC (obj
));
229 SCM_DEFINE (scm_weak_value_alist_vector_p
, "weak-value-alist-vector?", 1, 0, 0,
231 "Return @code{#t} if @var{obj} is a weak value hash table.")
232 #define FUNC_NAME s_scm_weak_value_alist_vector_p
234 return scm_from_bool (SCM_I_WVECTP (obj
) && SCM_IS_WHVEC_V (obj
));
239 SCM_DEFINE (scm_doubly_weak_alist_vector_p
, "doubly-weak-alist-vector?", 1, 0, 0,
241 "Return @code{#t} if @var{obj} is a doubly weak hash table.")
242 #define FUNC_NAME s_scm_doubly_weak_alist_vector_p
244 return scm_from_bool (SCM_I_WVECTP (obj
) && SCM_IS_WHVEC_B (obj
));
252 scm_init_weaks_builtins ()
254 #include "libguile/weaks.x"
255 return SCM_UNSPECIFIED
;
259 scm_weaks_prehistory ()
261 /* Initialize weak pairs. */
262 GC_word wcar_pair_bitmap
[GC_BITMAP_SIZE (scm_t_cell
)] = { 0 };
263 GC_word wcdr_pair_bitmap
[GC_BITMAP_SIZE (scm_t_cell
)] = { 0 };
265 /* In a weak-car pair, only the second word must be scanned for
267 GC_set_bit (wcar_pair_bitmap
, GC_WORD_OFFSET (scm_t_cell
, word_1
));
268 wcar_pair_descr
= GC_make_descriptor (wcar_pair_bitmap
,
269 GC_WORD_LEN (scm_t_cell
));
271 /* Conversely, in a weak-cdr pair, only the first word must be scanned for
273 GC_set_bit (wcdr_pair_bitmap
, GC_WORD_OFFSET (scm_t_cell
, word_0
));
274 wcdr_pair_descr
= GC_make_descriptor (wcdr_pair_bitmap
,
275 GC_WORD_LEN (scm_t_cell
));
282 scm_c_define_gsubr ("%init-weaks-builtins", 0, 0, 0,
283 scm_init_weaks_builtins
);