1 /* Copyright (C) 1995,1996,1998,2000,2001, 2003, 2006, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
3 * This library is free software; you can redistribute it and/or
4 * modify it under the terms of the GNU Lesser General Public License
5 * as published by the Free Software Foundation; either version 3 of
6 * the License, or (at your option) any later version.
8 * This library is distributed in the hope that it will be useful, but
9 * WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11 * Lesser General Public License for more details.
13 * You should have received a copy of the GNU Lesser General Public
14 * License along with this library; if not, write to the Free Software
15 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
27 #include "libguile/_scm.h"
28 #include "libguile/vectors.h"
29 #include "libguile/hashtab.h"
31 #include "libguile/validate.h"
32 #include "libguile/weaks.h"
34 #include "libguile/bdw-gc.h"
35 #include <gc/gc_typed.h>
39 /* Weak pairs for use in weak alist vectors and weak hash tables.
41 We have weal-car pairs, weak-cdr pairs, and doubly weak pairs. In weak
42 pairs, the weak component(s) are not scanned for pointers and are
43 registered as disapperaring links; therefore, the weak component may be
44 set to NULL by the garbage collector when no other reference to that word
45 exist. Thus, users should only access weak pairs via the
46 `SCM_WEAK_PAIR_C[AD]R ()' macros. See also `scm_fixup_weak_alist ()' in
49 /* Type descriptors for weak-c[ad]r pairs. */
50 static GC_descr wcar_pair_descr
, wcdr_pair_descr
;
54 scm_weak_car_pair (SCM car
, SCM cdr
)
58 cell
= (scm_t_cell
*)GC_malloc_explicitly_typed (sizeof (*cell
),
65 /* Weak car cells make sense iff the car is non-immediate. */
66 SCM_I_REGISTER_DISAPPEARING_LINK ((GC_PTR
) &cell
->word_0
,
67 (GC_PTR
) 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 ((GC_PTR
) &cell
->word_1
,
86 (GC_PTR
) SCM2PTR (cdr
));
88 return (SCM_PACK (cell
));
92 scm_doubly_weak_pair (SCM car
, SCM cdr
)
94 /* Doubly weak cells shall not be scanned at all for pointers. */
95 scm_t_cell
*cell
= (scm_t_cell
*)scm_gc_malloc_pointerless (sizeof (*cell
),
102 SCM_I_REGISTER_DISAPPEARING_LINK ((GC_PTR
) &cell
->word_0
,
103 (GC_PTR
) SCM2PTR (car
));
105 SCM_I_REGISTER_DISAPPEARING_LINK ((GC_PTR
) &cell
->word_1
,
106 (GC_PTR
) SCM2PTR (cdr
));
108 return (SCM_PACK (cell
));
114 /* 1. The current hash table implementation in hashtab.c uses weak alist
115 * vectors (formerly called weak hash tables) internally.
117 * 2. All hash table operations still work on alist vectors.
119 * 3. The weak vector and alist vector Scheme API is accessed through
120 * the module (ice-9 weak-vector).
128 SCM_DEFINE (scm_make_weak_vector
, "make-weak-vector", 1, 1, 0,
129 (SCM size
, SCM fill
),
130 "Return a weak vector with @var{size} elements. If the optional\n"
131 "argument @var{fill} is given, all entries in the vector will be\n"
132 "set to @var{fill}. The default value for @var{fill} is the\n"
134 #define FUNC_NAME s_scm_make_weak_vector
136 return scm_i_make_weak_vector (0, size
, fill
);
141 SCM_REGISTER_PROC(s_list_to_weak_vector
, "list->weak-vector", 1, 0, 0, scm_weak_vector
);
143 SCM_DEFINE (scm_weak_vector
, "weak-vector", 0, 0, 1,
145 "@deffnx {Scheme Procedure} list->weak-vector l\n"
146 "Construct a weak vector from a list: @code{weak-vector} uses\n"
147 "the list of its arguments while @code{list->weak-vector} uses\n"
148 "its only argument @var{l} (a list) to construct a weak vector\n"
149 "the same way @code{list->vector} would.")
150 #define FUNC_NAME s_scm_weak_vector
152 return scm_i_make_weak_vector_from_list (0, l
);
157 SCM_DEFINE (scm_weak_vector_p
, "weak-vector?", 1, 0, 0,
159 "Return @code{#t} if @var{obj} is a weak vector. Note that all\n"
160 "weak hashes are also weak vectors.")
161 #define FUNC_NAME s_scm_weak_vector_p
163 return scm_from_bool (SCM_I_WVECTP (obj
) && !SCM_IS_WHVEC (obj
));
168 /* Weak alist vectors, i.e., vectors of alists.
170 The alist vector themselves are _not_ weak. The `car' (or `cdr', or both)
171 of the pairs within it are weak. See `hashtab.c' for details. */
174 /* FIXME: We used to have two implementations of weak hash tables: the one in
175 here and the one in `hashtab.c'. The difference is that weak alist
176 vectors could be used as vectors while (weak) hash tables can't. We need
179 SCM_DEFINE (scm_make_weak_key_alist_vector
, "make-weak-key-alist-vector", 0, 1, 0,
181 "@deffnx {Scheme Procedure} make-weak-value-alist-vector size\n"
182 "@deffnx {Scheme Procedure} make-doubly-weak-alist-vector size\n"
183 "Return a weak hash table with @var{size} buckets. As with any\n"
184 "hash table, choosing a good size for the table requires some\n"
187 "You can modify weak hash tables in exactly the same way you\n"
188 "would modify regular hash tables. (@pxref{Hash Tables})")
189 #define FUNC_NAME s_scm_make_weak_key_alist_vector
191 return scm_make_weak_key_hash_table (size
);
196 SCM_DEFINE (scm_make_weak_value_alist_vector
, "make-weak-value-alist-vector", 0, 1, 0,
198 "Return a hash table with weak values with @var{size} buckets.\n"
199 "(@pxref{Hash Tables})")
200 #define FUNC_NAME s_scm_make_weak_value_alist_vector
202 return scm_make_weak_value_hash_table (size
);
207 SCM_DEFINE (scm_make_doubly_weak_alist_vector
, "make-doubly-weak-alist-vector", 1, 0, 0,
209 "Return a hash table with weak keys and values with @var{size}\n"
210 "buckets. (@pxref{Hash Tables})")
211 #define FUNC_NAME s_scm_make_doubly_weak_alist_vector
213 return scm_make_doubly_weak_hash_table (size
);
218 SCM_DEFINE (scm_weak_key_alist_vector_p
, "weak-key-alist-vector?", 1, 0, 0,
220 "@deffnx {Scheme Procedure} weak-value-alist-vector? obj\n"
221 "@deffnx {Scheme Procedure} doubly-weak-alist-vector? obj\n"
222 "Return @code{#t} if @var{obj} is the specified weak hash\n"
223 "table. Note that a doubly weak hash table is neither a weak key\n"
224 "nor a weak value hash table.")
225 #define FUNC_NAME s_scm_weak_key_alist_vector_p
227 return scm_from_bool (SCM_I_WVECTP (obj
) && SCM_IS_WHVEC (obj
));
232 SCM_DEFINE (scm_weak_value_alist_vector_p
, "weak-value-alist-vector?", 1, 0, 0,
234 "Return @code{#t} if @var{obj} is a weak value hash table.")
235 #define FUNC_NAME s_scm_weak_value_alist_vector_p
237 return scm_from_bool (SCM_I_WVECTP (obj
) && SCM_IS_WHVEC_V (obj
));
242 SCM_DEFINE (scm_doubly_weak_alist_vector_p
, "doubly-weak-alist-vector?", 1, 0, 0,
244 "Return @code{#t} if @var{obj} is a doubly weak hash table.")
245 #define FUNC_NAME s_scm_doubly_weak_alist_vector_p
247 return scm_from_bool (SCM_I_WVECTP (obj
) && SCM_IS_WHVEC_B (obj
));
255 scm_init_weaks_builtins ()
257 #include "libguile/weaks.x"
258 return SCM_UNSPECIFIED
;
262 scm_weaks_prehistory ()
264 /* Initialize weak pairs. */
265 GC_word wcar_pair_bitmap
[GC_BITMAP_SIZE (scm_t_cell
)] = { 0 };
266 GC_word wcdr_pair_bitmap
[GC_BITMAP_SIZE (scm_t_cell
)] = { 0 };
268 /* In a weak-car pair, only the second word must be scanned for
270 GC_set_bit (wcar_pair_bitmap
, GC_WORD_OFFSET (scm_t_cell
, word_1
));
271 wcar_pair_descr
= GC_make_descriptor (wcar_pair_bitmap
,
272 GC_WORD_LEN (scm_t_cell
));
274 /* Conversely, in a weak-cdr pair, only the first word must be scanned for
276 GC_set_bit (wcdr_pair_bitmap
, GC_WORD_OFFSET (scm_t_cell
, word_0
));
277 wcdr_pair_descr
= GC_make_descriptor (wcdr_pair_bitmap
,
278 GC_WORD_LEN (scm_t_cell
));
285 scm_c_define_gsubr ("%init-weaks-builtins", 0, 0, 0,
286 scm_init_weaks_builtins
);