| 1 | /* Copyright (C) 2011, 2012, 2013 Free Software Foundation, Inc. |
| 2 | * |
| 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. |
| 7 | * |
| 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. |
| 12 | * |
| 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 |
| 16 | * 02110-1301 USA |
| 17 | */ |
| 18 | |
| 19 | |
| 20 | \f |
| 21 | #ifdef HAVE_CONFIG_H |
| 22 | # include <config.h> |
| 23 | #endif |
| 24 | |
| 25 | #include <assert.h> |
| 26 | |
| 27 | #include "libguile/_scm.h" |
| 28 | #include "libguile/hash.h" |
| 29 | #include "libguile/eval.h" |
| 30 | #include "libguile/ports.h" |
| 31 | #include "libguile/bdw-gc.h" |
| 32 | |
| 33 | #include "libguile/validate.h" |
| 34 | #include "libguile/weak-set.h" |
| 35 | |
| 36 | |
| 37 | /* Weak Sets |
| 38 | |
| 39 | This file implements weak sets. One example of a weak set is the |
| 40 | symbol table, where you want all instances of the `foo' symbol to map |
| 41 | to one object. So when you load a file and it wants a symbol with |
| 42 | the characters "foo", you one up in the table, using custom hash and |
| 43 | equality predicates. Only if one is not found will you bother to |
| 44 | cons one up and intern it. |
| 45 | |
| 46 | Another use case for weak sets is the set of open ports. Guile needs |
| 47 | to be able to flush them all when the process exits, but the set |
| 48 | shouldn't prevent the GC from collecting the port (and thus closing |
| 49 | it). |
| 50 | |
| 51 | Weak sets are implemented using an open-addressed hash table. |
| 52 | Basically this means that there is an array of entries, and the item |
| 53 | is expected to be found the slot corresponding to its hash code, |
| 54 | modulo the length of the array. |
| 55 | |
| 56 | Collisions are handled using linear probing with the Robin Hood |
| 57 | technique. See Pedro Celis' paper, "Robin Hood Hashing": |
| 58 | |
| 59 | http://www.cs.uwaterloo.ca/research/tr/1986/CS-86-14.pdf |
| 60 | |
| 61 | The vector of entries is allocated as an "atomic" piece of memory, so |
| 62 | that the GC doesn't trace it. When an item is added to the set, a |
| 63 | disappearing link is registered to its location. If the item is |
| 64 | collected, then that link will be zeroed out. |
| 65 | |
| 66 | An entry is not just an item, though; the hash code is also stored in |
| 67 | the entry. We munge hash codes so that they are never 0. In this |
| 68 | way we can detect removed entries (key of zero but nonzero hash |
| 69 | code), and can then reshuffle elements as needed to maintain the |
| 70 | robin hood ordering. |
| 71 | |
| 72 | Compared to buckets-and-chains hash tables, open addressing has the |
| 73 | advantage that it is very cache-friendly. It also uses less memory. |
| 74 | |
| 75 | Implementation-wise, there are two things to note. |
| 76 | |
| 77 | 1. We assume that hash codes are evenly distributed across the |
| 78 | range of unsigned longs. The actual hash code stored in the |
| 79 | entry is left-shifted by 1 bit (losing 1 bit of hash precision), |
| 80 | and then or'd with 1. In this way we ensure that the hash field |
| 81 | of an occupied entry is nonzero. To map to an index, we |
| 82 | right-shift the hash by one, divide by the size, and take the |
| 83 | remainder. |
| 84 | |
| 85 | 2. Since the "keys" (the objects in the set) are stored in an |
| 86 | atomic region with disappearing links, they need to be accessed |
| 87 | with the GC alloc lock. `copy_weak_entry' will do that for |
| 88 | you. The hash code itself can be read outside the lock, |
| 89 | though. |
| 90 | */ |
| 91 | |
| 92 | |
| 93 | typedef struct { |
| 94 | unsigned long hash; |
| 95 | scm_t_bits key; |
| 96 | } scm_t_weak_entry; |
| 97 | |
| 98 | |
| 99 | struct weak_entry_data { |
| 100 | scm_t_weak_entry *in; |
| 101 | scm_t_weak_entry *out; |
| 102 | }; |
| 103 | |
| 104 | static void* |
| 105 | do_copy_weak_entry (void *data) |
| 106 | { |
| 107 | struct weak_entry_data *e = data; |
| 108 | |
| 109 | e->out->hash = e->in->hash; |
| 110 | e->out->key = e->in->key; |
| 111 | |
| 112 | return NULL; |
| 113 | } |
| 114 | |
| 115 | static void |
| 116 | copy_weak_entry (scm_t_weak_entry *src, scm_t_weak_entry *dst) |
| 117 | { |
| 118 | struct weak_entry_data data; |
| 119 | |
| 120 | data.in = src; |
| 121 | data.out = dst; |
| 122 | |
| 123 | GC_call_with_alloc_lock (do_copy_weak_entry, &data); |
| 124 | } |
| 125 | |
| 126 | |
| 127 | typedef struct { |
| 128 | scm_t_weak_entry *entries; /* the data */ |
| 129 | scm_i_pthread_mutex_t lock; /* the lock */ |
| 130 | unsigned long size; /* total number of slots. */ |
| 131 | unsigned long n_items; /* number of items in set */ |
| 132 | unsigned long lower; /* when to shrink */ |
| 133 | unsigned long upper; /* when to grow */ |
| 134 | int size_index; /* index into hashset_size */ |
| 135 | int min_size_index; /* minimum size_index */ |
| 136 | } scm_t_weak_set; |
| 137 | |
| 138 | |
| 139 | #define SCM_WEAK_SET_P(x) (SCM_HAS_TYP7 (x, scm_tc7_weak_set)) |
| 140 | #define SCM_VALIDATE_WEAK_SET(pos, arg) \ |
| 141 | SCM_MAKE_VALIDATE_MSG (pos, arg, WEAK_SET_P, "weak-set") |
| 142 | #define SCM_WEAK_SET(x) ((scm_t_weak_set *) SCM_CELL_WORD_1 (x)) |
| 143 | |
| 144 | |
| 145 | static unsigned long |
| 146 | hash_to_index (unsigned long hash, unsigned long size) |
| 147 | { |
| 148 | return (hash >> 1) % size; |
| 149 | } |
| 150 | |
| 151 | static unsigned long |
| 152 | entry_distance (unsigned long hash, unsigned long k, unsigned long size) |
| 153 | { |
| 154 | unsigned long origin = hash_to_index (hash, size); |
| 155 | |
| 156 | if (k >= origin) |
| 157 | return k - origin; |
| 158 | else |
| 159 | /* The other key was displaced and wrapped around. */ |
| 160 | return size - origin + k; |
| 161 | } |
| 162 | |
| 163 | #ifndef HAVE_GC_MOVE_DISAPPEARING_LINK |
| 164 | static void |
| 165 | GC_move_disappearing_link (void **from, void **to) |
| 166 | { |
| 167 | GC_unregister_disappearing_link (from); |
| 168 | SCM_I_REGISTER_DISAPPEARING_LINK (to, *to); |
| 169 | } |
| 170 | #endif |
| 171 | |
| 172 | static void |
| 173 | move_weak_entry (scm_t_weak_entry *from, scm_t_weak_entry *to) |
| 174 | { |
| 175 | if (from->hash) |
| 176 | { |
| 177 | scm_t_weak_entry copy; |
| 178 | |
| 179 | copy_weak_entry (from, ©); |
| 180 | to->hash = copy.hash; |
| 181 | to->key = copy.key; |
| 182 | |
| 183 | if (copy.key && SCM_HEAP_OBJECT_P (SCM_PACK (copy.key))) |
| 184 | GC_move_disappearing_link ((void **) &from->key, (void **) &to->key); |
| 185 | } |
| 186 | else |
| 187 | { |
| 188 | to->hash = 0; |
| 189 | to->key = 0; |
| 190 | } |
| 191 | } |
| 192 | |
| 193 | static void |
| 194 | rob_from_rich (scm_t_weak_set *set, unsigned long k) |
| 195 | { |
| 196 | unsigned long empty, size; |
| 197 | |
| 198 | size = set->size; |
| 199 | |
| 200 | /* If we are to free up slot K in the set, we need room to do so. */ |
| 201 | assert (set->n_items < size); |
| 202 | |
| 203 | empty = k; |
| 204 | do |
| 205 | empty = (empty + 1) % size; |
| 206 | /* Here we access key outside the lock. Is this a problem? At first |
| 207 | glance, I wouldn't think so. */ |
| 208 | while (set->entries[empty].key); |
| 209 | |
| 210 | do |
| 211 | { |
| 212 | unsigned long last = empty ? (empty - 1) : (size - 1); |
| 213 | move_weak_entry (&set->entries[last], &set->entries[empty]); |
| 214 | empty = last; |
| 215 | } |
| 216 | while (empty != k); |
| 217 | |
| 218 | /* Just for sanity. */ |
| 219 | set->entries[empty].hash = 0; |
| 220 | set->entries[empty].key = 0; |
| 221 | } |
| 222 | |
| 223 | static void |
| 224 | give_to_poor (scm_t_weak_set *set, unsigned long k) |
| 225 | { |
| 226 | /* Slot K was just freed up; possibly shuffle others down. */ |
| 227 | unsigned long size = set->size; |
| 228 | |
| 229 | while (1) |
| 230 | { |
| 231 | unsigned long next = (k + 1) % size; |
| 232 | unsigned long hash; |
| 233 | scm_t_weak_entry copy; |
| 234 | |
| 235 | hash = set->entries[next].hash; |
| 236 | |
| 237 | if (!hash || hash_to_index (hash, size) == next) |
| 238 | break; |
| 239 | |
| 240 | copy_weak_entry (&set->entries[next], ©); |
| 241 | |
| 242 | if (!copy.key) |
| 243 | /* Lost weak reference. */ |
| 244 | { |
| 245 | give_to_poor (set, next); |
| 246 | set->n_items--; |
| 247 | continue; |
| 248 | } |
| 249 | |
| 250 | move_weak_entry (&set->entries[next], &set->entries[k]); |
| 251 | |
| 252 | k = next; |
| 253 | } |
| 254 | |
| 255 | /* We have shuffled down any entries that should be shuffled down; now |
| 256 | free the end. */ |
| 257 | set->entries[k].hash = 0; |
| 258 | set->entries[k].key = 0; |
| 259 | } |
| 260 | |
| 261 | |
| 262 | \f |
| 263 | |
| 264 | /* Growing or shrinking is triggered when the load factor |
| 265 | * |
| 266 | * L = N / S (N: number of items in set, S: bucket vector length) |
| 267 | * |
| 268 | * passes an upper limit of 0.9 or a lower limit of 0.2. |
| 269 | * |
| 270 | * The implementation stores the upper and lower number of items which |
| 271 | * trigger a resize in the hashset object. |
| 272 | * |
| 273 | * Possible hash set sizes (primes) are stored in the array |
| 274 | * hashset_size. |
| 275 | */ |
| 276 | |
| 277 | static unsigned long hashset_size[] = { |
| 278 | 31, 61, 113, 223, 443, 883, 1759, 3517, 7027, 14051, 28099, 56197, 112363, |
| 279 | 224717, 449419, 898823, 1797641, 3595271, 7190537, 14381041, 28762081, |
| 280 | 57524111, 115048217, 230096423 |
| 281 | }; |
| 282 | |
| 283 | #define HASHSET_SIZE_N (sizeof(hashset_size)/sizeof(unsigned long)) |
| 284 | |
| 285 | static int |
| 286 | compute_size_index (scm_t_weak_set *set) |
| 287 | { |
| 288 | int i = set->size_index; |
| 289 | |
| 290 | if (set->n_items < set->lower) |
| 291 | { |
| 292 | /* rehashing is not triggered when i <= min_size */ |
| 293 | do |
| 294 | --i; |
| 295 | while (i > set->min_size_index |
| 296 | && set->n_items < hashset_size[i] / 5); |
| 297 | } |
| 298 | else if (set->n_items > set->upper) |
| 299 | { |
| 300 | ++i; |
| 301 | if (i >= HASHSET_SIZE_N) |
| 302 | /* The biggest size currently is 230096423, which for a 32-bit |
| 303 | machine will occupy 1.5GB of memory at a load of 80%. There |
| 304 | is probably something better to do here, but if you have a |
| 305 | weak map of that size, you are hosed in any case. */ |
| 306 | abort (); |
| 307 | } |
| 308 | |
| 309 | return i; |
| 310 | } |
| 311 | |
| 312 | static int |
| 313 | is_acceptable_size_index (scm_t_weak_set *set, int size_index) |
| 314 | { |
| 315 | int computed = compute_size_index (set); |
| 316 | |
| 317 | if (size_index == computed) |
| 318 | /* We were going to grow or shrink, and allocating the new vector |
| 319 | didn't change the target size. */ |
| 320 | return 1; |
| 321 | |
| 322 | if (size_index == computed + 1) |
| 323 | { |
| 324 | /* We were going to enlarge the set, but allocating the new |
| 325 | vector finalized some objects, making an enlargement |
| 326 | unnecessary. It might still be a good idea to use the larger |
| 327 | set, though. (This branch also gets hit if, while allocating |
| 328 | the vector, some other thread was actively removing items from |
| 329 | the set. That is less likely, though.) */ |
| 330 | unsigned long new_lower = hashset_size[size_index] / 5; |
| 331 | |
| 332 | return set->size > new_lower; |
| 333 | } |
| 334 | |
| 335 | if (size_index == computed - 1) |
| 336 | { |
| 337 | /* We were going to shrink the set, but when we dropped the lock |
| 338 | to allocate the new vector, some other thread added elements to |
| 339 | the set. */ |
| 340 | return 0; |
| 341 | } |
| 342 | |
| 343 | /* The computed size differs from our newly allocated size by more |
| 344 | than one size index -- recalculate. */ |
| 345 | return 0; |
| 346 | } |
| 347 | |
| 348 | static void |
| 349 | resize_set (scm_t_weak_set *set) |
| 350 | { |
| 351 | scm_t_weak_entry *old_entries, *new_entries; |
| 352 | int new_size_index; |
| 353 | unsigned long old_size, new_size, old_k; |
| 354 | |
| 355 | do |
| 356 | { |
| 357 | new_size_index = compute_size_index (set); |
| 358 | if (new_size_index == set->size_index) |
| 359 | return; |
| 360 | new_size = hashset_size[new_size_index]; |
| 361 | new_entries = scm_gc_malloc_pointerless (new_size * sizeof(scm_t_weak_entry), |
| 362 | "weak set"); |
| 363 | } |
| 364 | while (!is_acceptable_size_index (set, new_size_index)); |
| 365 | |
| 366 | old_entries = set->entries; |
| 367 | old_size = set->size; |
| 368 | |
| 369 | memset (new_entries, 0, new_size * sizeof(scm_t_weak_entry)); |
| 370 | |
| 371 | set->size_index = new_size_index; |
| 372 | set->size = new_size; |
| 373 | if (new_size_index <= set->min_size_index) |
| 374 | set->lower = 0; |
| 375 | else |
| 376 | set->lower = new_size / 5; |
| 377 | set->upper = 9 * new_size / 10; |
| 378 | set->n_items = 0; |
| 379 | set->entries = new_entries; |
| 380 | |
| 381 | for (old_k = 0; old_k < old_size; old_k++) |
| 382 | { |
| 383 | scm_t_weak_entry copy; |
| 384 | unsigned long new_k, distance; |
| 385 | |
| 386 | if (!old_entries[old_k].hash) |
| 387 | continue; |
| 388 | |
| 389 | copy_weak_entry (&old_entries[old_k], ©); |
| 390 | |
| 391 | if (!copy.key) |
| 392 | continue; |
| 393 | |
| 394 | new_k = hash_to_index (copy.hash, new_size); |
| 395 | |
| 396 | for (distance = 0; ; distance++, new_k = (new_k + 1) % new_size) |
| 397 | { |
| 398 | unsigned long other_hash = new_entries[new_k].hash; |
| 399 | |
| 400 | if (!other_hash) |
| 401 | /* Found an empty entry. */ |
| 402 | break; |
| 403 | |
| 404 | /* Displace the entry if our distance is less, otherwise keep |
| 405 | looking. */ |
| 406 | if (entry_distance (other_hash, new_k, new_size) < distance) |
| 407 | { |
| 408 | rob_from_rich (set, new_k); |
| 409 | break; |
| 410 | } |
| 411 | } |
| 412 | |
| 413 | set->n_items++; |
| 414 | new_entries[new_k].hash = copy.hash; |
| 415 | new_entries[new_k].key = copy.key; |
| 416 | |
| 417 | if (SCM_HEAP_OBJECT_P (SCM_PACK (copy.key))) |
| 418 | SCM_I_REGISTER_DISAPPEARING_LINK ((void **) &new_entries[new_k].key, |
| 419 | (void *) new_entries[new_k].key); |
| 420 | } |
| 421 | } |
| 422 | |
| 423 | /* Run from a finalizer via do_vacuum_weak_set, this function runs over |
| 424 | the whole table, removing lost weak references, reshuffling the set |
| 425 | as it goes. It might resize the set if it reaps enough entries. */ |
| 426 | static void |
| 427 | vacuum_weak_set (scm_t_weak_set *set) |
| 428 | { |
| 429 | scm_t_weak_entry *entries = set->entries; |
| 430 | unsigned long size = set->size; |
| 431 | unsigned long k; |
| 432 | |
| 433 | for (k = 0; k < size; k++) |
| 434 | { |
| 435 | unsigned long hash = entries[k].hash; |
| 436 | |
| 437 | if (hash) |
| 438 | { |
| 439 | scm_t_weak_entry copy; |
| 440 | |
| 441 | copy_weak_entry (&entries[k], ©); |
| 442 | |
| 443 | if (!copy.key) |
| 444 | /* Lost weak reference; reshuffle. */ |
| 445 | { |
| 446 | give_to_poor (set, k); |
| 447 | set->n_items--; |
| 448 | } |
| 449 | } |
| 450 | } |
| 451 | |
| 452 | if (set->n_items < set->lower) |
| 453 | resize_set (set); |
| 454 | } |
| 455 | |
| 456 | |
| 457 | \f |
| 458 | |
| 459 | static SCM |
| 460 | weak_set_lookup (scm_t_weak_set *set, unsigned long hash, |
| 461 | scm_t_set_predicate_fn pred, void *closure, |
| 462 | SCM dflt) |
| 463 | { |
| 464 | unsigned long k, distance, size; |
| 465 | scm_t_weak_entry *entries; |
| 466 | |
| 467 | size = set->size; |
| 468 | entries = set->entries; |
| 469 | |
| 470 | hash = (hash << 1) | 0x1; |
| 471 | k = hash_to_index (hash, size); |
| 472 | |
| 473 | for (distance = 0; distance < size; distance++, k = (k + 1) % size) |
| 474 | { |
| 475 | unsigned long other_hash; |
| 476 | |
| 477 | retry: |
| 478 | other_hash = entries[k].hash; |
| 479 | |
| 480 | if (!other_hash) |
| 481 | /* Not found. */ |
| 482 | return dflt; |
| 483 | |
| 484 | if (hash == other_hash) |
| 485 | { |
| 486 | scm_t_weak_entry copy; |
| 487 | |
| 488 | copy_weak_entry (&entries[k], ©); |
| 489 | |
| 490 | if (!copy.key) |
| 491 | /* Lost weak reference; reshuffle. */ |
| 492 | { |
| 493 | give_to_poor (set, k); |
| 494 | set->n_items--; |
| 495 | goto retry; |
| 496 | } |
| 497 | |
| 498 | if (pred (SCM_PACK (copy.key), closure)) |
| 499 | /* Found. */ |
| 500 | return SCM_PACK (copy.key); |
| 501 | } |
| 502 | |
| 503 | /* If the entry's distance is less, our key is not in the set. */ |
| 504 | if (entry_distance (other_hash, k, size) < distance) |
| 505 | return dflt; |
| 506 | } |
| 507 | |
| 508 | /* If we got here, then we were unfortunate enough to loop through the |
| 509 | whole set. Shouldn't happen, but hey. */ |
| 510 | return dflt; |
| 511 | } |
| 512 | |
| 513 | |
| 514 | static SCM |
| 515 | weak_set_add_x (scm_t_weak_set *set, unsigned long hash, |
| 516 | scm_t_set_predicate_fn pred, void *closure, |
| 517 | SCM obj) |
| 518 | { |
| 519 | unsigned long k, distance, size; |
| 520 | scm_t_weak_entry *entries; |
| 521 | |
| 522 | size = set->size; |
| 523 | entries = set->entries; |
| 524 | |
| 525 | hash = (hash << 1) | 0x1; |
| 526 | k = hash_to_index (hash, size); |
| 527 | |
| 528 | for (distance = 0; ; distance++, k = (k + 1) % size) |
| 529 | { |
| 530 | unsigned long other_hash; |
| 531 | |
| 532 | retry: |
| 533 | other_hash = entries[k].hash; |
| 534 | |
| 535 | if (!other_hash) |
| 536 | /* Found an empty entry. */ |
| 537 | break; |
| 538 | |
| 539 | if (other_hash == hash) |
| 540 | { |
| 541 | scm_t_weak_entry copy; |
| 542 | |
| 543 | copy_weak_entry (&entries[k], ©); |
| 544 | |
| 545 | if (!copy.key) |
| 546 | /* Lost weak reference; reshuffle. */ |
| 547 | { |
| 548 | give_to_poor (set, k); |
| 549 | set->n_items--; |
| 550 | goto retry; |
| 551 | } |
| 552 | |
| 553 | if (pred (SCM_PACK (copy.key), closure)) |
| 554 | /* Found an entry with this key. */ |
| 555 | return SCM_PACK (copy.key); |
| 556 | } |
| 557 | |
| 558 | if (set->n_items > set->upper) |
| 559 | /* Full set, time to resize. */ |
| 560 | { |
| 561 | resize_set (set); |
| 562 | return weak_set_add_x (set, hash >> 1, pred, closure, obj); |
| 563 | } |
| 564 | |
| 565 | /* Displace the entry if our distance is less, otherwise keep |
| 566 | looking. */ |
| 567 | if (entry_distance (other_hash, k, size) < distance) |
| 568 | { |
| 569 | rob_from_rich (set, k); |
| 570 | break; |
| 571 | } |
| 572 | } |
| 573 | |
| 574 | set->n_items++; |
| 575 | entries[k].hash = hash; |
| 576 | entries[k].key = SCM_UNPACK (obj); |
| 577 | |
| 578 | if (SCM_HEAP_OBJECT_P (obj)) |
| 579 | SCM_I_REGISTER_DISAPPEARING_LINK ((void **) &entries[k].key, |
| 580 | (void *) SCM2PTR (obj)); |
| 581 | |
| 582 | return obj; |
| 583 | } |
| 584 | |
| 585 | |
| 586 | static void |
| 587 | weak_set_remove_x (scm_t_weak_set *set, unsigned long hash, |
| 588 | scm_t_set_predicate_fn pred, void *closure) |
| 589 | { |
| 590 | unsigned long k, distance, size; |
| 591 | scm_t_weak_entry *entries; |
| 592 | |
| 593 | size = set->size; |
| 594 | entries = set->entries; |
| 595 | |
| 596 | hash = (hash << 1) | 0x1; |
| 597 | k = hash_to_index (hash, size); |
| 598 | |
| 599 | for (distance = 0; distance < size; distance++, k = (k + 1) % size) |
| 600 | { |
| 601 | unsigned long other_hash; |
| 602 | |
| 603 | retry: |
| 604 | other_hash = entries[k].hash; |
| 605 | |
| 606 | if (!other_hash) |
| 607 | /* Not found. */ |
| 608 | return; |
| 609 | |
| 610 | if (other_hash == hash) |
| 611 | { |
| 612 | scm_t_weak_entry copy; |
| 613 | |
| 614 | copy_weak_entry (&entries[k], ©); |
| 615 | |
| 616 | if (!copy.key) |
| 617 | /* Lost weak reference; reshuffle. */ |
| 618 | { |
| 619 | give_to_poor (set, k); |
| 620 | set->n_items--; |
| 621 | goto retry; |
| 622 | } |
| 623 | |
| 624 | if (pred (SCM_PACK (copy.key), closure)) |
| 625 | /* Found an entry with this key. */ |
| 626 | { |
| 627 | entries[k].hash = 0; |
| 628 | entries[k].key = 0; |
| 629 | |
| 630 | if (SCM_HEAP_OBJECT_P (SCM_PACK (copy.key))) |
| 631 | GC_unregister_disappearing_link ((void **) &entries[k].key); |
| 632 | |
| 633 | if (--set->n_items < set->lower) |
| 634 | resize_set (set); |
| 635 | else |
| 636 | give_to_poor (set, k); |
| 637 | |
| 638 | return; |
| 639 | } |
| 640 | } |
| 641 | |
| 642 | /* If the entry's distance is less, our key is not in the set. */ |
| 643 | if (entry_distance (other_hash, k, size) < distance) |
| 644 | return; |
| 645 | } |
| 646 | } |
| 647 | |
| 648 | |
| 649 | \f |
| 650 | static SCM |
| 651 | make_weak_set (unsigned long k) |
| 652 | { |
| 653 | scm_t_weak_set *set; |
| 654 | |
| 655 | int i = 0, n = k ? k : 31; |
| 656 | while (i + 1 < HASHSET_SIZE_N && n > hashset_size[i]) |
| 657 | ++i; |
| 658 | n = hashset_size[i]; |
| 659 | |
| 660 | set = scm_gc_malloc (sizeof (*set), "weak-set"); |
| 661 | set->entries = scm_gc_malloc_pointerless (n * sizeof(scm_t_weak_entry), |
| 662 | "weak-set"); |
| 663 | memset (set->entries, 0, n * sizeof(scm_t_weak_entry)); |
| 664 | set->n_items = 0; |
| 665 | set->size = n; |
| 666 | set->lower = 0; |
| 667 | set->upper = 9 * n / 10; |
| 668 | set->size_index = i; |
| 669 | set->min_size_index = i; |
| 670 | scm_i_pthread_mutex_init (&set->lock, NULL); |
| 671 | |
| 672 | return scm_cell (scm_tc7_weak_set, (scm_t_bits)set); |
| 673 | } |
| 674 | |
| 675 | void |
| 676 | scm_i_weak_set_print (SCM exp, SCM port, scm_print_state *pstate) |
| 677 | { |
| 678 | scm_puts_unlocked ("#<", port); |
| 679 | scm_puts_unlocked ("weak-set ", port); |
| 680 | scm_uintprint (SCM_WEAK_SET (exp)->n_items, 10, port); |
| 681 | scm_putc_unlocked ('/', port); |
| 682 | scm_uintprint (SCM_WEAK_SET (exp)->size, 10, port); |
| 683 | scm_puts_unlocked (">", port); |
| 684 | } |
| 685 | |
| 686 | static void |
| 687 | do_vacuum_weak_set (SCM set) |
| 688 | { |
| 689 | scm_t_weak_set *s; |
| 690 | |
| 691 | s = SCM_WEAK_SET (set); |
| 692 | |
| 693 | /* We should always be able to grab this lock, because we are run from |
| 694 | a finalizer, which runs in another thread (or an async, which is |
| 695 | mostly equivalent). */ |
| 696 | scm_i_pthread_mutex_lock (&s->lock); |
| 697 | vacuum_weak_set (s); |
| 698 | scm_i_pthread_mutex_unlock (&s->lock); |
| 699 | } |
| 700 | |
| 701 | SCM |
| 702 | scm_c_make_weak_set (unsigned long k) |
| 703 | { |
| 704 | SCM ret; |
| 705 | |
| 706 | ret = make_weak_set (k); |
| 707 | |
| 708 | scm_i_register_weak_gc_callback (ret, do_vacuum_weak_set); |
| 709 | |
| 710 | return ret; |
| 711 | } |
| 712 | |
| 713 | SCM |
| 714 | scm_weak_set_p (SCM obj) |
| 715 | { |
| 716 | return scm_from_bool (SCM_WEAK_SET_P (obj)); |
| 717 | } |
| 718 | |
| 719 | SCM |
| 720 | scm_weak_set_clear_x (SCM set) |
| 721 | { |
| 722 | scm_t_weak_set *s = SCM_WEAK_SET (set); |
| 723 | |
| 724 | scm_i_pthread_mutex_lock (&s->lock); |
| 725 | |
| 726 | memset (s->entries, 0, sizeof (scm_t_weak_entry) * s->size); |
| 727 | s->n_items = 0; |
| 728 | |
| 729 | scm_i_pthread_mutex_unlock (&s->lock); |
| 730 | |
| 731 | return SCM_UNSPECIFIED; |
| 732 | } |
| 733 | |
| 734 | SCM |
| 735 | scm_c_weak_set_lookup (SCM set, unsigned long raw_hash, |
| 736 | scm_t_set_predicate_fn pred, |
| 737 | void *closure, SCM dflt) |
| 738 | { |
| 739 | SCM ret; |
| 740 | scm_t_weak_set *s = SCM_WEAK_SET (set); |
| 741 | |
| 742 | scm_i_pthread_mutex_lock (&s->lock); |
| 743 | |
| 744 | ret = weak_set_lookup (s, raw_hash, pred, closure, dflt); |
| 745 | |
| 746 | scm_i_pthread_mutex_unlock (&s->lock); |
| 747 | |
| 748 | return ret; |
| 749 | } |
| 750 | |
| 751 | SCM |
| 752 | scm_c_weak_set_add_x (SCM set, unsigned long raw_hash, |
| 753 | scm_t_set_predicate_fn pred, |
| 754 | void *closure, SCM obj) |
| 755 | { |
| 756 | SCM ret; |
| 757 | scm_t_weak_set *s = SCM_WEAK_SET (set); |
| 758 | |
| 759 | scm_i_pthread_mutex_lock (&s->lock); |
| 760 | |
| 761 | ret = weak_set_add_x (s, raw_hash, pred, closure, obj); |
| 762 | |
| 763 | scm_i_pthread_mutex_unlock (&s->lock); |
| 764 | |
| 765 | return ret; |
| 766 | } |
| 767 | |
| 768 | void |
| 769 | scm_c_weak_set_remove_x (SCM set, unsigned long raw_hash, |
| 770 | scm_t_set_predicate_fn pred, |
| 771 | void *closure) |
| 772 | { |
| 773 | scm_t_weak_set *s = SCM_WEAK_SET (set); |
| 774 | |
| 775 | scm_i_pthread_mutex_lock (&s->lock); |
| 776 | |
| 777 | weak_set_remove_x (s, raw_hash, pred, closure); |
| 778 | |
| 779 | scm_i_pthread_mutex_unlock (&s->lock); |
| 780 | } |
| 781 | |
| 782 | static int |
| 783 | eq_predicate (SCM x, void *closure) |
| 784 | { |
| 785 | return scm_is_eq (x, SCM_PACK_POINTER (closure)); |
| 786 | } |
| 787 | |
| 788 | SCM |
| 789 | scm_weak_set_add_x (SCM set, SCM obj) |
| 790 | { |
| 791 | return scm_c_weak_set_add_x (set, scm_ihashq (obj, -1), |
| 792 | eq_predicate, SCM_UNPACK_POINTER (obj), obj); |
| 793 | } |
| 794 | |
| 795 | SCM |
| 796 | scm_weak_set_remove_x (SCM set, SCM obj) |
| 797 | { |
| 798 | scm_c_weak_set_remove_x (set, scm_ihashq (obj, -1), |
| 799 | eq_predicate, SCM_UNPACK_POINTER (obj)); |
| 800 | |
| 801 | return SCM_UNSPECIFIED; |
| 802 | } |
| 803 | |
| 804 | SCM |
| 805 | scm_c_weak_set_fold (scm_t_set_fold_fn proc, void *closure, |
| 806 | SCM init, SCM set) |
| 807 | { |
| 808 | scm_t_weak_set *s; |
| 809 | scm_t_weak_entry *entries; |
| 810 | unsigned long k, size; |
| 811 | |
| 812 | s = SCM_WEAK_SET (set); |
| 813 | |
| 814 | scm_i_pthread_mutex_lock (&s->lock); |
| 815 | |
| 816 | size = s->size; |
| 817 | entries = s->entries; |
| 818 | |
| 819 | for (k = 0; k < size; k++) |
| 820 | { |
| 821 | if (entries[k].hash) |
| 822 | { |
| 823 | scm_t_weak_entry copy; |
| 824 | |
| 825 | copy_weak_entry (&entries[k], ©); |
| 826 | |
| 827 | if (copy.key) |
| 828 | { |
| 829 | /* Release set lock while we call the function. */ |
| 830 | scm_i_pthread_mutex_unlock (&s->lock); |
| 831 | init = proc (closure, SCM_PACK (copy.key), init); |
| 832 | scm_i_pthread_mutex_lock (&s->lock); |
| 833 | } |
| 834 | } |
| 835 | } |
| 836 | |
| 837 | scm_i_pthread_mutex_unlock (&s->lock); |
| 838 | |
| 839 | return init; |
| 840 | } |
| 841 | |
| 842 | static SCM |
| 843 | fold_trampoline (void *closure, SCM item, SCM init) |
| 844 | { |
| 845 | return scm_call_2 (SCM_PACK_POINTER (closure), item, init); |
| 846 | } |
| 847 | |
| 848 | SCM |
| 849 | scm_weak_set_fold (SCM proc, SCM init, SCM set) |
| 850 | { |
| 851 | return scm_c_weak_set_fold (fold_trampoline, SCM_UNPACK_POINTER (proc), init, set); |
| 852 | } |
| 853 | |
| 854 | static SCM |
| 855 | for_each_trampoline (void *closure, SCM item, SCM seed) |
| 856 | { |
| 857 | scm_call_1 (SCM_PACK_POINTER (closure), item); |
| 858 | return seed; |
| 859 | } |
| 860 | |
| 861 | SCM |
| 862 | scm_weak_set_for_each (SCM proc, SCM set) |
| 863 | { |
| 864 | scm_c_weak_set_fold (for_each_trampoline, SCM_UNPACK_POINTER (proc), SCM_BOOL_F, set); |
| 865 | |
| 866 | return SCM_UNSPECIFIED; |
| 867 | } |
| 868 | |
| 869 | static SCM |
| 870 | map_trampoline (void *closure, SCM item, SCM seed) |
| 871 | { |
| 872 | return scm_cons (scm_call_1 (SCM_PACK_POINTER (closure), item), seed); |
| 873 | } |
| 874 | |
| 875 | SCM |
| 876 | scm_weak_set_map_to_list (SCM proc, SCM set) |
| 877 | { |
| 878 | return scm_c_weak_set_fold (map_trampoline, SCM_UNPACK_POINTER (proc), SCM_EOL, set); |
| 879 | } |
| 880 | |
| 881 | |
| 882 | void |
| 883 | scm_init_weak_set () |
| 884 | { |
| 885 | #include "libguile/weak-set.x" |
| 886 | } |
| 887 | |
| 888 | /* |
| 889 | Local Variables: |
| 890 | c-file-style: "gnu" |
| 891 | End: |
| 892 | */ |