| 1 | /* Copyright (C) 1995, 1996, 1998, 2000, 2001, 2003, 2006, 2008, 2009, 2010, |
| 2 | * 2011, 2012, 2014 Free Software Foundation, Inc. |
| 3 | * |
| 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. |
| 8 | * |
| 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. |
| 13 | * |
| 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 |
| 17 | * 02110-1301 USA |
| 18 | */ |
| 19 | |
| 20 | |
| 21 | \f |
| 22 | #ifdef HAVE_CONFIG_H |
| 23 | # include <config.h> |
| 24 | #endif |
| 25 | |
| 26 | #include <stdio.h> |
| 27 | |
| 28 | #include "libguile/_scm.h" |
| 29 | #include "libguile/vectors.h" |
| 30 | #include "libguile/hashtab.h" |
| 31 | |
| 32 | #include "libguile/validate.h" |
| 33 | #include "libguile/weaks.h" |
| 34 | |
| 35 | #include "libguile/bdw-gc.h" |
| 36 | #include <gc/gc_typed.h> |
| 37 | |
| 38 | |
| 39 | \f |
| 40 | /* Weak pairs for use in weak alist vectors and weak hash tables. |
| 41 | |
| 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 |
| 48 | `hashtab.c'. */ |
| 49 | |
| 50 | /* Type descriptors for weak-c[ad]r pairs. */ |
| 51 | static GC_descr wcar_pair_descr, wcdr_pair_descr; |
| 52 | |
| 53 | |
| 54 | SCM |
| 55 | scm_weak_car_pair (SCM car, SCM cdr) |
| 56 | { |
| 57 | scm_t_cell *cell; |
| 58 | |
| 59 | cell = (scm_t_cell *)GC_malloc_explicitly_typed (sizeof (*cell), |
| 60 | wcar_pair_descr); |
| 61 | |
| 62 | cell->word_0 = car; |
| 63 | cell->word_1 = cdr; |
| 64 | |
| 65 | if (SCM_NIMP (car)) |
| 66 | /* Weak car cells make sense iff the car is non-immediate. */ |
| 67 | SCM_I_REGISTER_DISAPPEARING_LINK ((void **) &cell->word_0, SCM2PTR (car)); |
| 68 | |
| 69 | return (SCM_PACK (cell)); |
| 70 | } |
| 71 | |
| 72 | SCM |
| 73 | scm_weak_cdr_pair (SCM car, SCM cdr) |
| 74 | { |
| 75 | scm_t_cell *cell; |
| 76 | |
| 77 | cell = (scm_t_cell *)GC_malloc_explicitly_typed (sizeof (*cell), |
| 78 | wcdr_pair_descr); |
| 79 | |
| 80 | cell->word_0 = car; |
| 81 | cell->word_1 = cdr; |
| 82 | |
| 83 | if (SCM_NIMP (cdr)) |
| 84 | /* Weak cdr cells make sense iff the cdr is non-immediate. */ |
| 85 | SCM_I_REGISTER_DISAPPEARING_LINK ((void **) &cell->word_1, SCM2PTR (cdr)); |
| 86 | |
| 87 | return (SCM_PACK (cell)); |
| 88 | } |
| 89 | |
| 90 | SCM |
| 91 | scm_doubly_weak_pair (SCM car, SCM cdr) |
| 92 | { |
| 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), |
| 95 | "weak cell"); |
| 96 | |
| 97 | cell->word_0 = car; |
| 98 | cell->word_1 = cdr; |
| 99 | |
| 100 | if (SCM_NIMP (car)) |
| 101 | SCM_I_REGISTER_DISAPPEARING_LINK ((void **) &cell->word_0, SCM2PTR (car)); |
| 102 | if (SCM_NIMP (cdr)) |
| 103 | SCM_I_REGISTER_DISAPPEARING_LINK ((void **) &cell->word_1, SCM2PTR (cdr)); |
| 104 | |
| 105 | return (SCM_PACK (cell)); |
| 106 | } |
| 107 | |
| 108 | |
| 109 | \f |
| 110 | |
| 111 | /* 1. The current hash table implementation in hashtab.c uses weak alist |
| 112 | * vectors (formerly called weak hash tables) internally. |
| 113 | * |
| 114 | * 2. All hash table operations still work on alist vectors. |
| 115 | * |
| 116 | * 3. The weak vector and alist vector Scheme API is accessed through |
| 117 | * the module (ice-9 weak-vector). |
| 118 | */ |
| 119 | |
| 120 | |
| 121 | /* {Weak Vectors} |
| 122 | */ |
| 123 | |
| 124 | |
| 125 | #define SCM_VALIDATE_WEAK_VECTOR(pos, var) \ |
| 126 | SCM_I_MAKE_VALIDATE_MSG2 (pos, var, SCM_I_WVECTP, "weak vector") |
| 127 | |
| 128 | |
| 129 | SCM_DEFINE (scm_make_weak_vector, "make-weak-vector", 1, 1, 0, |
| 130 | (SCM size, SCM fill), |
| 131 | "Return a weak vector with @var{size} elements. If the optional\n" |
| 132 | "argument @var{fill} is given, all entries in the vector will be\n" |
| 133 | "set to @var{fill}. The default value for @var{fill} is the\n" |
| 134 | "empty list.") |
| 135 | #define FUNC_NAME s_scm_make_weak_vector |
| 136 | { |
| 137 | return scm_i_make_weak_vector (0, size, fill); |
| 138 | } |
| 139 | #undef FUNC_NAME |
| 140 | |
| 141 | |
| 142 | SCM_REGISTER_PROC(s_list_to_weak_vector, "list->weak-vector", 1, 0, 0, scm_weak_vector); |
| 143 | |
| 144 | SCM_DEFINE (scm_weak_vector, "weak-vector", 0, 0, 1, |
| 145 | (SCM l), |
| 146 | "@deffnx {Scheme Procedure} list->weak-vector l\n" |
| 147 | "Construct a weak vector from a list: @code{weak-vector} uses\n" |
| 148 | "the list of its arguments while @code{list->weak-vector} uses\n" |
| 149 | "its only argument @var{l} (a list) to construct a weak vector\n" |
| 150 | "the same way @code{list->vector} would.") |
| 151 | #define FUNC_NAME s_scm_weak_vector |
| 152 | { |
| 153 | return scm_i_make_weak_vector_from_list (0, l); |
| 154 | } |
| 155 | #undef FUNC_NAME |
| 156 | |
| 157 | |
| 158 | SCM_DEFINE (scm_weak_vector_p, "weak-vector?", 1, 0, 0, |
| 159 | (SCM obj), |
| 160 | "Return @code{#t} if @var{obj} is a weak vector. Note that all\n" |
| 161 | "weak hashes are also weak vectors.") |
| 162 | #define FUNC_NAME s_scm_weak_vector_p |
| 163 | { |
| 164 | return scm_from_bool (scm_is_weak_vector (obj)); |
| 165 | } |
| 166 | #undef FUNC_NAME |
| 167 | |
| 168 | |
| 169 | int |
| 170 | scm_is_weak_vector (SCM obj) |
| 171 | { |
| 172 | return SCM_I_WVECTP (obj) && !SCM_IS_WHVEC (obj); |
| 173 | } |
| 174 | |
| 175 | |
| 176 | SCM_DEFINE (scm_weak_vector_length, "weak-vector-length", 1, 0, 0, |
| 177 | (SCM wvect), |
| 178 | "Returns the number of elements in @var{wvect} as an exact integer.") |
| 179 | #define FUNC_NAME s_scm_weak_vector_length |
| 180 | { |
| 181 | return scm_from_size_t (scm_c_weak_vector_length (wvect)); |
| 182 | } |
| 183 | #undef FUNC_NAME |
| 184 | |
| 185 | |
| 186 | size_t |
| 187 | scm_c_weak_vector_length (SCM wvect) |
| 188 | #define FUNC_NAME s_scm_weak_vector_length |
| 189 | { |
| 190 | SCM_VALIDATE_WEAK_VECTOR (1, wvect); |
| 191 | return SCM_I_VECTOR_LENGTH (wvect); |
| 192 | } |
| 193 | #undef FUNC_NAME |
| 194 | |
| 195 | |
| 196 | SCM_DEFINE (scm_weak_vector_ref, "weak-vector-ref", 2, 0, 0, |
| 197 | (SCM wvect, SCM k), |
| 198 | "Like @code{vector-ref}, but for weak vectors.") |
| 199 | #define FUNC_NAME s_scm_weak_vector_ref |
| 200 | { |
| 201 | return scm_c_weak_vector_ref (wvect, scm_to_size_t (k)); |
| 202 | } |
| 203 | #undef FUNC_NAME |
| 204 | |
| 205 | |
| 206 | SCM |
| 207 | scm_c_weak_vector_ref (SCM wvect, size_t k) |
| 208 | #define FUNC_NAME s_scm_weak_vector_ref |
| 209 | { |
| 210 | SCM elt; |
| 211 | |
| 212 | SCM_VALIDATE_WEAK_VECTOR (1, wvect); |
| 213 | |
| 214 | if (k >= SCM_I_VECTOR_LENGTH (wvect)) |
| 215 | scm_out_of_range ("weak-vector-ref", scm_from_size_t (k)); |
| 216 | elt = (SCM_I_VECTOR_ELTS(wvect))[k]; |
| 217 | |
| 218 | if (SCM_UNPACK (elt) == 0) |
| 219 | /* ELT was a weak pointer and got nullified by the GC. */ |
| 220 | return SCM_BOOL_F; |
| 221 | |
| 222 | return elt; |
| 223 | } |
| 224 | #undef FUNC_NAME |
| 225 | |
| 226 | |
| 227 | SCM_DEFINE (scm_weak_vector_set_x, "weak-vector-set!", 3, 0, 0, |
| 228 | (SCM wvect, SCM k, SCM elt), |
| 229 | "Like @code{vector-set!}, but for weak vectors.") |
| 230 | #define FUNC_NAME s_scm_weak_vector_set_x |
| 231 | { |
| 232 | scm_c_weak_vector_set_x (wvect, scm_to_size_t (k), elt); |
| 233 | |
| 234 | return SCM_UNSPECIFIED; |
| 235 | } |
| 236 | #undef FUNC_NAME |
| 237 | |
| 238 | |
| 239 | void |
| 240 | scm_c_weak_vector_set_x (SCM wvect, size_t k, SCM elt) |
| 241 | #define FUNC_NAME s_scm_weak_vector_set_x |
| 242 | { |
| 243 | SCM *loc; |
| 244 | |
| 245 | SCM_VALIDATE_WEAK_VECTOR (1, wvect); |
| 246 | |
| 247 | if (k >= SCM_I_VECTOR_LENGTH (wvect)) |
| 248 | scm_out_of_range ("weak-vector-set!", scm_from_size_t (k)); |
| 249 | |
| 250 | loc = & SCM_I_VECTOR_WELTS (wvect)[k]; |
| 251 | *loc = elt; |
| 252 | |
| 253 | /* Make it a weak pointer. */ |
| 254 | SCM_I_REGISTER_DISAPPEARING_LINK ((void **) loc, SCM2PTR (elt)); |
| 255 | } |
| 256 | #undef FUNC_NAME |
| 257 | |
| 258 | |
| 259 | \f |
| 260 | /* Weak alist vectors, i.e., vectors of alists. |
| 261 | |
| 262 | The alist vector themselves are _not_ weak. The `car' (or `cdr', or both) |
| 263 | of the pairs within it are weak. See `hashtab.c' for details. */ |
| 264 | |
| 265 | |
| 266 | /* FIXME: We used to have two implementations of weak hash tables: the one in |
| 267 | here and the one in `hashtab.c'. The difference is that weak alist |
| 268 | vectors could be used as vectors while (weak) hash tables can't. We need |
| 269 | to unify that. */ |
| 270 | |
| 271 | SCM_DEFINE (scm_make_weak_key_alist_vector, "make-weak-key-alist-vector", 0, 1, 0, |
| 272 | (SCM size), |
| 273 | "@deffnx {Scheme Procedure} make-weak-value-alist-vector size\n" |
| 274 | "@deffnx {Scheme Procedure} make-doubly-weak-alist-vector size\n" |
| 275 | "Return a weak hash table with @var{size} buckets. As with any\n" |
| 276 | "hash table, choosing a good size for the table requires some\n" |
| 277 | "caution.\n" |
| 278 | "\n" |
| 279 | "You can modify weak hash tables in exactly the same way you\n" |
| 280 | "would modify regular hash tables. (@pxref{Hash Tables})") |
| 281 | #define FUNC_NAME s_scm_make_weak_key_alist_vector |
| 282 | { |
| 283 | return scm_make_weak_key_hash_table (size); |
| 284 | } |
| 285 | #undef FUNC_NAME |
| 286 | |
| 287 | |
| 288 | SCM_DEFINE (scm_make_weak_value_alist_vector, "make-weak-value-alist-vector", 0, 1, 0, |
| 289 | (SCM size), |
| 290 | "Return a hash table with weak values with @var{size} buckets.\n" |
| 291 | "(@pxref{Hash Tables})") |
| 292 | #define FUNC_NAME s_scm_make_weak_value_alist_vector |
| 293 | { |
| 294 | return scm_make_weak_value_hash_table (size); |
| 295 | } |
| 296 | #undef FUNC_NAME |
| 297 | |
| 298 | |
| 299 | SCM_DEFINE (scm_make_doubly_weak_alist_vector, "make-doubly-weak-alist-vector", 1, 0, 0, |
| 300 | (SCM size), |
| 301 | "Return a hash table with weak keys and values with @var{size}\n" |
| 302 | "buckets. (@pxref{Hash Tables})") |
| 303 | #define FUNC_NAME s_scm_make_doubly_weak_alist_vector |
| 304 | { |
| 305 | return scm_make_doubly_weak_hash_table (size); |
| 306 | } |
| 307 | #undef FUNC_NAME |
| 308 | |
| 309 | |
| 310 | SCM_DEFINE (scm_weak_key_alist_vector_p, "weak-key-alist-vector?", 1, 0, 0, |
| 311 | (SCM obj), |
| 312 | "@deffnx {Scheme Procedure} weak-value-alist-vector? obj\n" |
| 313 | "@deffnx {Scheme Procedure} doubly-weak-alist-vector? obj\n" |
| 314 | "Return @code{#t} if @var{obj} is the specified weak hash\n" |
| 315 | "table. Note that a doubly weak hash table is neither a weak key\n" |
| 316 | "nor a weak value hash table.") |
| 317 | #define FUNC_NAME s_scm_weak_key_alist_vector_p |
| 318 | { |
| 319 | return scm_from_bool (SCM_I_WVECTP (obj) && SCM_IS_WHVEC (obj)); |
| 320 | } |
| 321 | #undef FUNC_NAME |
| 322 | |
| 323 | |
| 324 | SCM_DEFINE (scm_weak_value_alist_vector_p, "weak-value-alist-vector?", 1, 0, 0, |
| 325 | (SCM obj), |
| 326 | "Return @code{#t} if @var{obj} is a weak value hash table.") |
| 327 | #define FUNC_NAME s_scm_weak_value_alist_vector_p |
| 328 | { |
| 329 | return scm_from_bool (SCM_I_WVECTP (obj) && SCM_IS_WHVEC_V (obj)); |
| 330 | } |
| 331 | #undef FUNC_NAME |
| 332 | |
| 333 | |
| 334 | SCM_DEFINE (scm_doubly_weak_alist_vector_p, "doubly-weak-alist-vector?", 1, 0, 0, |
| 335 | (SCM obj), |
| 336 | "Return @code{#t} if @var{obj} is a doubly weak hash table.") |
| 337 | #define FUNC_NAME s_scm_doubly_weak_alist_vector_p |
| 338 | { |
| 339 | return scm_from_bool (SCM_I_WVECTP (obj) && SCM_IS_WHVEC_B (obj)); |
| 340 | } |
| 341 | #undef FUNC_NAME |
| 342 | |
| 343 | |
| 344 | |
| 345 | \f |
| 346 | SCM |
| 347 | scm_init_weaks_builtins () |
| 348 | { |
| 349 | #include "libguile/weaks.x" |
| 350 | return SCM_UNSPECIFIED; |
| 351 | } |
| 352 | |
| 353 | void |
| 354 | scm_weaks_prehistory () |
| 355 | { |
| 356 | /* Initialize weak pairs. */ |
| 357 | GC_word wcar_pair_bitmap[GC_BITMAP_SIZE (scm_t_cell)] = { 0 }; |
| 358 | GC_word wcdr_pair_bitmap[GC_BITMAP_SIZE (scm_t_cell)] = { 0 }; |
| 359 | |
| 360 | /* In a weak-car pair, only the second word must be scanned for |
| 361 | pointers. */ |
| 362 | GC_set_bit (wcar_pair_bitmap, GC_WORD_OFFSET (scm_t_cell, word_1)); |
| 363 | wcar_pair_descr = GC_make_descriptor (wcar_pair_bitmap, |
| 364 | GC_WORD_LEN (scm_t_cell)); |
| 365 | |
| 366 | /* Conversely, in a weak-cdr pair, only the first word must be scanned for |
| 367 | pointers. */ |
| 368 | GC_set_bit (wcdr_pair_bitmap, GC_WORD_OFFSET (scm_t_cell, word_0)); |
| 369 | wcdr_pair_descr = GC_make_descriptor (wcdr_pair_bitmap, |
| 370 | GC_WORD_LEN (scm_t_cell)); |
| 371 | |
| 372 | } |
| 373 | |
| 374 | void |
| 375 | scm_init_weaks () |
| 376 | { |
| 377 | scm_c_define_gsubr ("%init-weaks-builtins", 0, 0, 0, |
| 378 | scm_init_weaks_builtins); |
| 379 | } |
| 380 | |
| 381 | |
| 382 | /* |
| 383 | Local Variables: |
| 384 | c-file-style: "gnu" |
| 385 | End: |
| 386 | */ |