/js/lib/Socket.IO-node/support/expresso/deps/jscoverage/js/jsdhash.cpp
C++ | 876 lines | 625 code | 111 blank | 140 comment | 94 complexity | a4ea72d4299baa5adae07d29773b5184 MD5 | raw file
1/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */ 2/* ***** BEGIN LICENSE BLOCK ***** 3 * Version: MPL 1.1/GPL 2.0/LGPL 2.1 4 * 5 * The contents of this file are subject to the Mozilla Public License Version 6 * 1.1 (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * http://www.mozilla.org/MPL/ 9 * 10 * Software distributed under the License is distributed on an "AS IS" basis, 11 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License 12 * for the specific language governing rights and limitations under the 13 * License. 14 * 15 * The Original Code is Mozilla JavaScript code. 16 * 17 * The Initial Developer of the Original Code is 18 * Netscape Communications Corporation. 19 * Portions created by the Initial Developer are Copyright (C) 1999-2001 20 * the Initial Developer. All Rights Reserved. 21 * 22 * Contributor(s): 23 * Brendan Eich <brendan@mozilla.org> (Original Author) 24 * Chris Waterson <waterson@netscape.com> 25 * L. David Baron <dbaron@dbaron.org>, Mozilla Corporation 26 * 27 * Alternatively, the contents of this file may be used under the terms of 28 * either of the GNU General Public License Version 2 or later (the "GPL"), 29 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"), 30 * in which case the provisions of the GPL or the LGPL are applicable instead 31 * of those above. If you wish to allow use of your version of this file only 32 * under the terms of either the GPL or the LGPL, and not to allow others to 33 * use your version of this file under the terms of the MPL, indicate your 34 * decision by deleting the provisions above and replace them with the notice 35 * and other provisions required by the GPL or the LGPL. If you do not delete 36 * the provisions above, a recipient may use your version of this file under 37 * the terms of any one of the MPL, the GPL or the LGPL. 38 * 39 * ***** END LICENSE BLOCK ***** */ 40 41/* 42 * Double hashing implementation. 43 */ 44#include <stdio.h> 45#include <stdlib.h> 46#include <string.h> 47#include "jsbit.h" 48#include "jsdhash.h" 49#include "jsutil.h" /* for JS_ASSERT */ 50 51#ifdef JS_DHASHMETER 52# if defined MOZILLA_CLIENT && defined DEBUG_XXXbrendan 53# include "nsTraceMalloc.h" 54# endif 55# define METER(x) x 56#else 57# define METER(x) /* nothing */ 58#endif 59 60/* 61 * The following DEBUG-only code is used to assert that calls to one of 62 * table->ops or to an enumerator do not cause re-entry into a call that 63 * can mutate the table. The recursion level is stored in additional 64 * space allocated at the end of the entry store to avoid changing 65 * JSDHashTable, which could cause issues when mixing DEBUG and 66 * non-DEBUG components. 67 */ 68#ifdef DEBUG 69 70#define JSDHASH_ONELINE_ASSERT JS_ASSERT 71#define RECURSION_LEVEL(table_) (*(uint32*)(table_->entryStore + \ 72 JS_DHASH_TABLE_SIZE(table_) * \ 73 table_->entrySize)) 74 75#define ENTRY_STORE_EXTRA sizeof(uint32) 76#define INCREMENT_RECURSION_LEVEL(table_) \ 77 JS_BEGIN_MACRO \ 78 ++RECURSION_LEVEL(table_); \ 79 JS_END_MACRO 80#define DECREMENT_RECURSION_LEVEL(table_) \ 81 JS_BEGIN_MACRO \ 82 JSDHASH_ONELINE_ASSERT(RECURSION_LEVEL(table_) > 0); \ 83 --RECURSION_LEVEL(table_); \ 84 JS_END_MACRO 85 86#else 87 88#define ENTRY_STORE_EXTRA 0 89#define INCREMENT_RECURSION_LEVEL(table_) JS_BEGIN_MACRO JS_END_MACRO 90#define DECREMENT_RECURSION_LEVEL(table_) JS_BEGIN_MACRO JS_END_MACRO 91 92#endif /* defined(DEBUG) */ 93 94JS_PUBLIC_API(void *) 95JS_DHashAllocTable(JSDHashTable *table, uint32 nbytes) 96{ 97 return malloc(nbytes); 98} 99 100JS_PUBLIC_API(void) 101JS_DHashFreeTable(JSDHashTable *table, void *ptr) 102{ 103 free(ptr); 104} 105 106JS_PUBLIC_API(JSDHashNumber) 107JS_DHashStringKey(JSDHashTable *table, const void *key) 108{ 109 JSDHashNumber h; 110 const unsigned char *s; 111 112 h = 0; 113 for (s = (const unsigned char *) key; *s != '\0'; s++) 114 h = JS_ROTATE_LEFT32(h, 4) ^ *s; 115 return h; 116} 117 118JS_PUBLIC_API(JSDHashNumber) 119JS_DHashVoidPtrKeyStub(JSDHashTable *table, const void *key) 120{ 121 return (JSDHashNumber)(unsigned long)key >> 2; 122} 123 124JS_PUBLIC_API(JSBool) 125JS_DHashMatchEntryStub(JSDHashTable *table, 126 const JSDHashEntryHdr *entry, 127 const void *key) 128{ 129 const JSDHashEntryStub *stub = (const JSDHashEntryStub *)entry; 130 131 return stub->key == key; 132} 133 134JS_PUBLIC_API(JSBool) 135JS_DHashMatchStringKey(JSDHashTable *table, 136 const JSDHashEntryHdr *entry, 137 const void *key) 138{ 139 const JSDHashEntryStub *stub = (const JSDHashEntryStub *)entry; 140 141 /* XXX tolerate null keys on account of sloppy Mozilla callers. */ 142 return stub->key == key || 143 (stub->key && key && 144 strcmp((const char *) stub->key, (const char *) key) == 0); 145} 146 147JS_PUBLIC_API(void) 148JS_DHashMoveEntryStub(JSDHashTable *table, 149 const JSDHashEntryHdr *from, 150 JSDHashEntryHdr *to) 151{ 152 memcpy(to, from, table->entrySize); 153} 154 155JS_PUBLIC_API(void) 156JS_DHashClearEntryStub(JSDHashTable *table, JSDHashEntryHdr *entry) 157{ 158 memset(entry, 0, table->entrySize); 159} 160 161JS_PUBLIC_API(void) 162JS_DHashFreeStringKey(JSDHashTable *table, JSDHashEntryHdr *entry) 163{ 164 const JSDHashEntryStub *stub = (const JSDHashEntryStub *)entry; 165 166 free((void *) stub->key); 167 memset(entry, 0, table->entrySize); 168} 169 170JS_PUBLIC_API(void) 171JS_DHashFinalizeStub(JSDHashTable *table) 172{ 173} 174 175static const JSDHashTableOps stub_ops = { 176 JS_DHashAllocTable, 177 JS_DHashFreeTable, 178 JS_DHashVoidPtrKeyStub, 179 JS_DHashMatchEntryStub, 180 JS_DHashMoveEntryStub, 181 JS_DHashClearEntryStub, 182 JS_DHashFinalizeStub, 183 NULL 184}; 185 186JS_PUBLIC_API(const JSDHashTableOps *) 187JS_DHashGetStubOps(void) 188{ 189 return &stub_ops; 190} 191 192JS_PUBLIC_API(JSDHashTable *) 193JS_NewDHashTable(const JSDHashTableOps *ops, void *data, uint32 entrySize, 194 uint32 capacity) 195{ 196 JSDHashTable *table; 197 198 table = (JSDHashTable *) malloc(sizeof *table); 199 if (!table) 200 return NULL; 201 if (!JS_DHashTableInit(table, ops, data, entrySize, capacity)) { 202 free(table); 203 return NULL; 204 } 205 return table; 206} 207 208JS_PUBLIC_API(void) 209JS_DHashTableDestroy(JSDHashTable *table) 210{ 211 JS_DHashTableFinish(table); 212 free(table); 213} 214 215JS_PUBLIC_API(JSBool) 216JS_DHashTableInit(JSDHashTable *table, const JSDHashTableOps *ops, void *data, 217 uint32 entrySize, uint32 capacity) 218{ 219 int log2; 220 uint32 nbytes; 221 222#ifdef DEBUG 223 if (entrySize > 10 * sizeof(void *)) { 224 fprintf(stderr, 225 "jsdhash: for the table at address %p, the given entrySize" 226 " of %lu %s favors chaining over double hashing.\n", 227 (void *) table, 228 (unsigned long) entrySize, 229 (entrySize > 16 * sizeof(void*)) ? "definitely" : "probably"); 230 } 231#endif 232 233 table->ops = ops; 234 table->data = data; 235 if (capacity < JS_DHASH_MIN_SIZE) 236 capacity = JS_DHASH_MIN_SIZE; 237 238 JS_CEILING_LOG2(log2, capacity); 239 240 capacity = JS_BIT(log2); 241 if (capacity >= JS_DHASH_SIZE_LIMIT) 242 return JS_FALSE; 243 table->hashShift = JS_DHASH_BITS - log2; 244 table->maxAlphaFrac = (uint8)(0x100 * JS_DHASH_DEFAULT_MAX_ALPHA); 245 table->minAlphaFrac = (uint8)(0x100 * JS_DHASH_DEFAULT_MIN_ALPHA); 246 table->entrySize = entrySize; 247 table->entryCount = table->removedCount = 0; 248 table->generation = 0; 249 nbytes = capacity * entrySize; 250 251 table->entryStore = (char *) ops->allocTable(table, 252 nbytes + ENTRY_STORE_EXTRA); 253 if (!table->entryStore) 254 return JS_FALSE; 255 memset(table->entryStore, 0, nbytes); 256 METER(memset(&table->stats, 0, sizeof table->stats)); 257 258#ifdef DEBUG 259 RECURSION_LEVEL(table) = 0; 260#endif 261 262 return JS_TRUE; 263} 264 265/* 266 * Compute max and min load numbers (entry counts) from table params. 267 */ 268#define MAX_LOAD(table, size) (((table)->maxAlphaFrac * (size)) >> 8) 269#define MIN_LOAD(table, size) (((table)->minAlphaFrac * (size)) >> 8) 270 271JS_PUBLIC_API(void) 272JS_DHashTableSetAlphaBounds(JSDHashTable *table, 273 float maxAlpha, 274 float minAlpha) 275{ 276 uint32 size; 277 278 /* 279 * Reject obviously insane bounds, rather than trying to guess what the 280 * buggy caller intended. 281 */ 282 JS_ASSERT(0.5 <= maxAlpha && maxAlpha < 1 && 0 <= minAlpha); 283 if (maxAlpha < 0.5 || 1 <= maxAlpha || minAlpha < 0) 284 return; 285 286 /* 287 * Ensure that at least one entry will always be free. If maxAlpha at 288 * minimum size leaves no entries free, reduce maxAlpha based on minimum 289 * size and the precision limit of maxAlphaFrac's fixed point format. 290 */ 291 JS_ASSERT(JS_DHASH_MIN_SIZE - (maxAlpha * JS_DHASH_MIN_SIZE) >= 1); 292 if (JS_DHASH_MIN_SIZE - (maxAlpha * JS_DHASH_MIN_SIZE) < 1) { 293 maxAlpha = (float) 294 (JS_DHASH_MIN_SIZE - JS_MAX(JS_DHASH_MIN_SIZE / 256, 1)) 295 / JS_DHASH_MIN_SIZE; 296 } 297 298 /* 299 * Ensure that minAlpha is strictly less than half maxAlpha. Take care 300 * not to truncate an entry's worth of alpha when storing in minAlphaFrac 301 * (8-bit fixed point format). 302 */ 303 JS_ASSERT(minAlpha < maxAlpha / 2); 304 if (minAlpha >= maxAlpha / 2) { 305 size = JS_DHASH_TABLE_SIZE(table); 306 minAlpha = (size * maxAlpha - JS_MAX(size / 256, 1)) / (2 * size); 307 } 308 309 table->maxAlphaFrac = (uint8)(maxAlpha * 256); 310 table->minAlphaFrac = (uint8)(minAlpha * 256); 311} 312 313/* 314 * Double hashing needs the second hash code to be relatively prime to table 315 * size, so we simply make hash2 odd. 316 */ 317#define HASH1(hash0, shift) ((hash0) >> (shift)) 318#define HASH2(hash0,log2,shift) ((((hash0) << (log2)) >> (shift)) | 1) 319 320/* 321 * Reserve keyHash 0 for free entries and 1 for removed-entry sentinels. Note 322 * that a removed-entry sentinel need be stored only if the removed entry had 323 * a colliding entry added after it. Therefore we can use 1 as the collision 324 * flag in addition to the removed-entry sentinel value. Multiplicative hash 325 * uses the high order bits of keyHash, so this least-significant reservation 326 * should not hurt the hash function's effectiveness much. 327 * 328 * If you change any of these magic numbers, also update JS_DHASH_ENTRY_IS_LIVE 329 * in jsdhash.h. It used to be private to jsdhash.c, but then became public to 330 * assist iterator writers who inspect table->entryStore directly. 331 */ 332#define COLLISION_FLAG ((JSDHashNumber) 1) 333#define MARK_ENTRY_FREE(entry) ((entry)->keyHash = 0) 334#define MARK_ENTRY_REMOVED(entry) ((entry)->keyHash = 1) 335#define ENTRY_IS_REMOVED(entry) ((entry)->keyHash == 1) 336#define ENTRY_IS_LIVE(entry) JS_DHASH_ENTRY_IS_LIVE(entry) 337#define ENSURE_LIVE_KEYHASH(hash0) if (hash0 < 2) hash0 -= 2; else (void)0 338 339/* Match an entry's keyHash against an unstored one computed from a key. */ 340#define MATCH_ENTRY_KEYHASH(entry,hash0) \ 341 (((entry)->keyHash & ~COLLISION_FLAG) == (hash0)) 342 343/* Compute the address of the indexed entry in table. */ 344#define ADDRESS_ENTRY(table, index) \ 345 ((JSDHashEntryHdr *)((table)->entryStore + (index) * (table)->entrySize)) 346 347JS_PUBLIC_API(void) 348JS_DHashTableFinish(JSDHashTable *table) 349{ 350 char *entryAddr, *entryLimit; 351 uint32 entrySize; 352 JSDHashEntryHdr *entry; 353 354#ifdef DEBUG_XXXbrendan 355 static FILE *dumpfp = NULL; 356 if (!dumpfp) dumpfp = fopen("/tmp/jsdhash.bigdump", "w"); 357 if (dumpfp) { 358#ifdef MOZILLA_CLIENT 359 NS_TraceStack(1, dumpfp); 360#endif 361 JS_DHashTableDumpMeter(table, NULL, dumpfp); 362 fputc('\n', dumpfp); 363 } 364#endif 365 366 INCREMENT_RECURSION_LEVEL(table); 367 368 /* Call finalize before clearing entries, so it can enumerate them. */ 369 table->ops->finalize(table); 370 371 /* Clear any remaining live entries. */ 372 entryAddr = table->entryStore; 373 entrySize = table->entrySize; 374 entryLimit = entryAddr + JS_DHASH_TABLE_SIZE(table) * entrySize; 375 while (entryAddr < entryLimit) { 376 entry = (JSDHashEntryHdr *)entryAddr; 377 if (ENTRY_IS_LIVE(entry)) { 378 METER(table->stats.removeEnums++); 379 table->ops->clearEntry(table, entry); 380 } 381 entryAddr += entrySize; 382 } 383 384 DECREMENT_RECURSION_LEVEL(table); 385 JS_ASSERT(RECURSION_LEVEL(table) == 0); 386 387 /* Free entry storage last. */ 388 table->ops->freeTable(table, table->entryStore); 389} 390 391static JSDHashEntryHdr * JS_DHASH_FASTCALL 392SearchTable(JSDHashTable *table, const void *key, JSDHashNumber keyHash, 393 JSDHashOperator op) 394{ 395 JSDHashNumber hash1, hash2; 396 int hashShift, sizeLog2; 397 JSDHashEntryHdr *entry, *firstRemoved; 398 JSDHashMatchEntry matchEntry; 399 uint32 sizeMask; 400 401 METER(table->stats.searches++); 402 JS_ASSERT(!(keyHash & COLLISION_FLAG)); 403 404 /* Compute the primary hash address. */ 405 hashShift = table->hashShift; 406 hash1 = HASH1(keyHash, hashShift); 407 entry = ADDRESS_ENTRY(table, hash1); 408 409 /* Miss: return space for a new entry. */ 410 if (JS_DHASH_ENTRY_IS_FREE(entry)) { 411 METER(table->stats.misses++); 412 return entry; 413 } 414 415 /* Hit: return entry. */ 416 matchEntry = table->ops->matchEntry; 417 if (MATCH_ENTRY_KEYHASH(entry, keyHash) && matchEntry(table, entry, key)) { 418 METER(table->stats.hits++); 419 return entry; 420 } 421 422 /* Collision: double hash. */ 423 sizeLog2 = JS_DHASH_BITS - table->hashShift; 424 hash2 = HASH2(keyHash, sizeLog2, hashShift); 425 sizeMask = JS_BITMASK(sizeLog2); 426 427 /* Save the first removed entry pointer so JS_DHASH_ADD can recycle it. */ 428 firstRemoved = NULL; 429 430 for (;;) { 431 if (JS_UNLIKELY(ENTRY_IS_REMOVED(entry))) { 432 if (!firstRemoved) 433 firstRemoved = entry; 434 } else { 435 if (op == JS_DHASH_ADD) 436 entry->keyHash |= COLLISION_FLAG; 437 } 438 439 METER(table->stats.steps++); 440 hash1 -= hash2; 441 hash1 &= sizeMask; 442 443 entry = ADDRESS_ENTRY(table, hash1); 444 if (JS_DHASH_ENTRY_IS_FREE(entry)) { 445 METER(table->stats.misses++); 446 return (firstRemoved && op == JS_DHASH_ADD) ? firstRemoved : entry; 447 } 448 449 if (MATCH_ENTRY_KEYHASH(entry, keyHash) && 450 matchEntry(table, entry, key)) { 451 METER(table->stats.hits++); 452 return entry; 453 } 454 } 455 456 /* NOTREACHED */ 457 return NULL; 458} 459 460/* 461 * This is a copy of SearchTable, used by ChangeTable, hardcoded to 462 * 1. assume |op == PL_DHASH_ADD|, 463 * 2. assume that |key| will never match an existing entry, and 464 * 3. assume that no entries have been removed from the current table 465 * structure. 466 * Avoiding the need for |key| means we can avoid needing a way to map 467 * entries to keys, which means callers can use complex key types more 468 * easily. 469 */ 470static JSDHashEntryHdr * JS_DHASH_FASTCALL 471FindFreeEntry(JSDHashTable *table, JSDHashNumber keyHash) 472{ 473 JSDHashNumber hash1, hash2; 474 int hashShift, sizeLog2; 475 JSDHashEntryHdr *entry; 476 uint32 sizeMask; 477 478 METER(table->stats.searches++); 479 JS_ASSERT(!(keyHash & COLLISION_FLAG)); 480 481 /* Compute the primary hash address. */ 482 hashShift = table->hashShift; 483 hash1 = HASH1(keyHash, hashShift); 484 entry = ADDRESS_ENTRY(table, hash1); 485 486 /* Miss: return space for a new entry. */ 487 if (JS_DHASH_ENTRY_IS_FREE(entry)) { 488 METER(table->stats.misses++); 489 return entry; 490 } 491 492 /* Collision: double hash. */ 493 sizeLog2 = JS_DHASH_BITS - table->hashShift; 494 hash2 = HASH2(keyHash, sizeLog2, hashShift); 495 sizeMask = JS_BITMASK(sizeLog2); 496 497 for (;;) { 498 JS_ASSERT(!ENTRY_IS_REMOVED(entry)); 499 entry->keyHash |= COLLISION_FLAG; 500 501 METER(table->stats.steps++); 502 hash1 -= hash2; 503 hash1 &= sizeMask; 504 505 entry = ADDRESS_ENTRY(table, hash1); 506 if (JS_DHASH_ENTRY_IS_FREE(entry)) { 507 METER(table->stats.misses++); 508 return entry; 509 } 510 } 511 512 /* NOTREACHED */ 513 return NULL; 514} 515 516static JSBool 517ChangeTable(JSDHashTable *table, int deltaLog2) 518{ 519 int oldLog2, newLog2; 520 uint32 oldCapacity, newCapacity; 521 char *newEntryStore, *oldEntryStore, *oldEntryAddr; 522 uint32 entrySize, i, nbytes; 523 JSDHashEntryHdr *oldEntry, *newEntry; 524 JSDHashMoveEntry moveEntry; 525#ifdef DEBUG 526 uint32 recursionLevel; 527#endif 528 529 /* Look, but don't touch, until we succeed in getting new entry store. */ 530 oldLog2 = JS_DHASH_BITS - table->hashShift; 531 newLog2 = oldLog2 + deltaLog2; 532 oldCapacity = JS_BIT(oldLog2); 533 newCapacity = JS_BIT(newLog2); 534 if (newCapacity >= JS_DHASH_SIZE_LIMIT) 535 return JS_FALSE; 536 entrySize = table->entrySize; 537 nbytes = newCapacity * entrySize; 538 539 newEntryStore = (char *) table->ops->allocTable(table, 540 nbytes + ENTRY_STORE_EXTRA); 541 if (!newEntryStore) 542 return JS_FALSE; 543 544 /* We can't fail from here on, so update table parameters. */ 545#ifdef DEBUG 546 recursionLevel = RECURSION_LEVEL(table); 547#endif 548 table->hashShift = JS_DHASH_BITS - newLog2; 549 table->removedCount = 0; 550 table->generation++; 551 552 /* Assign the new entry store to table. */ 553 memset(newEntryStore, 0, nbytes); 554 oldEntryAddr = oldEntryStore = table->entryStore; 555 table->entryStore = newEntryStore; 556 moveEntry = table->ops->moveEntry; 557#ifdef DEBUG 558 RECURSION_LEVEL(table) = recursionLevel; 559#endif 560 561 /* Copy only live entries, leaving removed ones behind. */ 562 for (i = 0; i < oldCapacity; i++) { 563 oldEntry = (JSDHashEntryHdr *)oldEntryAddr; 564 if (ENTRY_IS_LIVE(oldEntry)) { 565 oldEntry->keyHash &= ~COLLISION_FLAG; 566 newEntry = FindFreeEntry(table, oldEntry->keyHash); 567 JS_ASSERT(JS_DHASH_ENTRY_IS_FREE(newEntry)); 568 moveEntry(table, oldEntry, newEntry); 569 newEntry->keyHash = oldEntry->keyHash; 570 } 571 oldEntryAddr += entrySize; 572 } 573 574 table->ops->freeTable(table, oldEntryStore); 575 return JS_TRUE; 576} 577 578JS_PUBLIC_API(JSDHashEntryHdr *) JS_DHASH_FASTCALL 579JS_DHashTableOperate(JSDHashTable *table, const void *key, JSDHashOperator op) 580{ 581 JSDHashNumber keyHash; 582 JSDHashEntryHdr *entry; 583 uint32 size; 584 int deltaLog2; 585 586 JS_ASSERT(op == JS_DHASH_LOOKUP || RECURSION_LEVEL(table) == 0); 587 INCREMENT_RECURSION_LEVEL(table); 588 589 keyHash = table->ops->hashKey(table, key); 590 keyHash *= JS_DHASH_GOLDEN_RATIO; 591 592 /* Avoid 0 and 1 hash codes, they indicate free and removed entries. */ 593 ENSURE_LIVE_KEYHASH(keyHash); 594 keyHash &= ~COLLISION_FLAG; 595 596 switch (op) { 597 case JS_DHASH_LOOKUP: 598 METER(table->stats.lookups++); 599 entry = SearchTable(table, key, keyHash, op); 600 break; 601 602 case JS_DHASH_ADD: 603 /* 604 * If alpha is >= .75, grow or compress the table. If key is already 605 * in the table, we may grow once more than necessary, but only if we 606 * are on the edge of being overloaded. 607 */ 608 size = JS_DHASH_TABLE_SIZE(table); 609 if (table->entryCount + table->removedCount >= MAX_LOAD(table, size)) { 610 /* Compress if a quarter or more of all entries are removed. */ 611 if (table->removedCount >= size >> 2) { 612 METER(table->stats.compresses++); 613 deltaLog2 = 0; 614 } else { 615 METER(table->stats.grows++); 616 deltaLog2 = 1; 617 } 618 619 /* 620 * Grow or compress table, returning null if ChangeTable fails and 621 * falling through might claim the last free entry. 622 */ 623 if (!ChangeTable(table, deltaLog2) && 624 table->entryCount + table->removedCount == size - 1) { 625 METER(table->stats.addFailures++); 626 entry = NULL; 627 break; 628 } 629 } 630 631 /* 632 * Look for entry after possibly growing, so we don't have to add it, 633 * then skip it while growing the table and re-add it after. 634 */ 635 entry = SearchTable(table, key, keyHash, op); 636 if (!ENTRY_IS_LIVE(entry)) { 637 /* Initialize the entry, indicating that it's no longer free. */ 638 METER(table->stats.addMisses++); 639 if (ENTRY_IS_REMOVED(entry)) { 640 METER(table->stats.addOverRemoved++); 641 table->removedCount--; 642 keyHash |= COLLISION_FLAG; 643 } 644 if (table->ops->initEntry && 645 !table->ops->initEntry(table, entry, key)) { 646 /* We haven't claimed entry yet; fail with null return. */ 647 memset(entry + 1, 0, table->entrySize - sizeof *entry); 648 entry = NULL; 649 break; 650 } 651 entry->keyHash = keyHash; 652 table->entryCount++; 653 } 654 METER(else table->stats.addHits++); 655 break; 656 657 case JS_DHASH_REMOVE: 658 entry = SearchTable(table, key, keyHash, op); 659 if (ENTRY_IS_LIVE(entry)) { 660 /* Clear this entry and mark it as "removed". */ 661 METER(table->stats.removeHits++); 662 JS_DHashTableRawRemove(table, entry); 663 664 /* Shrink if alpha is <= .25 and table isn't too small already. */ 665 size = JS_DHASH_TABLE_SIZE(table); 666 if (size > JS_DHASH_MIN_SIZE && 667 table->entryCount <= MIN_LOAD(table, size)) { 668 METER(table->stats.shrinks++); 669 (void) ChangeTable(table, -1); 670 } 671 } 672 METER(else table->stats.removeMisses++); 673 entry = NULL; 674 break; 675 676 default: 677 JS_ASSERT(0); 678 entry = NULL; 679 } 680 681 DECREMENT_RECURSION_LEVEL(table); 682 683 return entry; 684} 685 686JS_PUBLIC_API(void) 687JS_DHashTableRawRemove(JSDHashTable *table, JSDHashEntryHdr *entry) 688{ 689 JSDHashNumber keyHash; /* load first in case clearEntry goofs it */ 690 691 JS_ASSERT(JS_DHASH_ENTRY_IS_LIVE(entry)); 692 keyHash = entry->keyHash; 693 table->ops->clearEntry(table, entry); 694 if (keyHash & COLLISION_FLAG) { 695 MARK_ENTRY_REMOVED(entry); 696 table->removedCount++; 697 } else { 698 METER(table->stats.removeFrees++); 699 MARK_ENTRY_FREE(entry); 700 } 701 table->entryCount--; 702} 703 704JS_PUBLIC_API(uint32) 705JS_DHashTableEnumerate(JSDHashTable *table, JSDHashEnumerator etor, void *arg) 706{ 707 char *entryAddr, *entryLimit; 708 uint32 i, capacity, entrySize, ceiling; 709 JSBool didRemove; 710 JSDHashEntryHdr *entry; 711 JSDHashOperator op; 712 713 INCREMENT_RECURSION_LEVEL(table); 714 715 entryAddr = table->entryStore; 716 entrySize = table->entrySize; 717 capacity = JS_DHASH_TABLE_SIZE(table); 718 entryLimit = entryAddr + capacity * entrySize; 719 i = 0; 720 didRemove = JS_FALSE; 721 while (entryAddr < entryLimit) { 722 entry = (JSDHashEntryHdr *)entryAddr; 723 if (ENTRY_IS_LIVE(entry)) { 724 op = etor(table, entry, i++, arg); 725 if (op & JS_DHASH_REMOVE) { 726 METER(table->stats.removeEnums++); 727 JS_DHashTableRawRemove(table, entry); 728 didRemove = JS_TRUE; 729 } 730 if (op & JS_DHASH_STOP) 731 break; 732 } 733 entryAddr += entrySize; 734 } 735 736 JS_ASSERT(!didRemove || RECURSION_LEVEL(table) == 1); 737 738 /* 739 * Shrink or compress if a quarter or more of all entries are removed, or 740 * if the table is underloaded according to the configured minimum alpha, 741 * and is not minimal-size already. Do this only if we removed above, so 742 * non-removing enumerations can count on stable table->entryStore until 743 * the next non-lookup-Operate or removing-Enumerate. 744 */ 745 if (didRemove && 746 (table->removedCount >= capacity >> 2 || 747 (capacity > JS_DHASH_MIN_SIZE && 748 table->entryCount <= MIN_LOAD(table, capacity)))) { 749 METER(table->stats.enumShrinks++); 750 capacity = table->entryCount; 751 capacity += capacity >> 1; 752 if (capacity < JS_DHASH_MIN_SIZE) 753 capacity = JS_DHASH_MIN_SIZE; 754 755 JS_CEILING_LOG2(ceiling, capacity); 756 ceiling -= JS_DHASH_BITS - table->hashShift; 757 758 (void) ChangeTable(table, ceiling); 759 } 760 761 DECREMENT_RECURSION_LEVEL(table); 762 763 return i; 764} 765 766#ifdef JS_DHASHMETER 767#include <math.h> 768 769JS_PUBLIC_API(void) 770JS_DHashTableDumpMeter(JSDHashTable *table, JSDHashEnumerator dump, FILE *fp) 771{ 772 char *entryAddr; 773 uint32 entrySize, entryCount; 774 int hashShift, sizeLog2; 775 uint32 i, tableSize, sizeMask, chainLen, maxChainLen, chainCount; 776 JSDHashNumber hash1, hash2, saveHash1, maxChainHash1, maxChainHash2; 777 double sqsum, mean, variance, sigma; 778 JSDHashEntryHdr *entry, *probe; 779 780 entryAddr = table->entryStore; 781 entrySize = table->entrySize; 782 hashShift = table->hashShift; 783 sizeLog2 = JS_DHASH_BITS - hashShift; 784 tableSize = JS_DHASH_TABLE_SIZE(table); 785 sizeMask = JS_BITMASK(sizeLog2); 786 chainCount = maxChainLen = 0; 787 hash2 = 0; 788 sqsum = 0; 789 790 for (i = 0; i < tableSize; i++) { 791 entry = (JSDHashEntryHdr *)entryAddr; 792 entryAddr += entrySize; 793 if (!ENTRY_IS_LIVE(entry)) 794 continue; 795 hash1 = HASH1(entry->keyHash & ~COLLISION_FLAG, hashShift); 796 saveHash1 = hash1; 797 probe = ADDRESS_ENTRY(table, hash1); 798 chainLen = 1; 799 if (probe == entry) { 800 /* Start of a (possibly unit-length) chain. */ 801 chainCount++; 802 } else { 803 hash2 = HASH2(entry->keyHash & ~COLLISION_FLAG, sizeLog2, 804 hashShift); 805 do { 806 chainLen++; 807 hash1 -= hash2; 808 hash1 &= sizeMask; 809 probe = ADDRESS_ENTRY(table, hash1); 810 } while (probe != entry); 811 } 812 sqsum += chainLen * chainLen; 813 if (chainLen > maxChainLen) { 814 maxChainLen = chainLen; 815 maxChainHash1 = saveHash1; 816 maxChainHash2 = hash2; 817 } 818 } 819 820 entryCount = table->entryCount; 821 if (entryCount && chainCount) { 822 mean = (double)entryCount / chainCount; 823 variance = chainCount * sqsum - entryCount * entryCount; 824 if (variance < 0 || chainCount == 1) 825 variance = 0; 826 else 827 variance /= chainCount * (chainCount - 1); 828 sigma = sqrt(variance); 829 } else { 830 mean = sigma = 0; 831 } 832 833 fprintf(fp, "Double hashing statistics:\n"); 834 fprintf(fp, " table size (in entries): %u\n", tableSize); 835 fprintf(fp, " number of entries: %u\n", table->entryCount); 836 fprintf(fp, " number of removed entries: %u\n", table->removedCount); 837 fprintf(fp, " number of searches: %u\n", table->stats.searches); 838 fprintf(fp, " number of hits: %u\n", table->stats.hits); 839 fprintf(fp, " number of misses: %u\n", table->stats.misses); 840 fprintf(fp, " mean steps per search: %g\n", table->stats.searches ? 841 (double)table->stats.steps 842 / table->stats.searches : 843 0.); 844 fprintf(fp, " mean hash chain length: %g\n", mean); 845 fprintf(fp, " standard deviation: %g\n", sigma); 846 fprintf(fp, " maximum hash chain length: %u\n", maxChainLen); 847 fprintf(fp, " number of lookups: %u\n", table->stats.lookups); 848 fprintf(fp, " adds that made a new entry: %u\n", table->stats.addMisses); 849 fprintf(fp, "adds that recycled removeds: %u\n", table->stats.addOverRemoved); 850 fprintf(fp, " adds that found an entry: %u\n", table->stats.addHits); 851 fprintf(fp, " add failures: %u\n", table->stats.addFailures); 852 fprintf(fp, " useful removes: %u\n", table->stats.removeHits); 853 fprintf(fp, " useless removes: %u\n", table->stats.removeMisses); 854 fprintf(fp, "removes that freed an entry: %u\n", table->stats.removeFrees); 855 fprintf(fp, " removes while enumerating: %u\n", table->stats.removeEnums); 856 fprintf(fp, " number of grows: %u\n", table->stats.grows); 857 fprintf(fp, " number of shrinks: %u\n", table->stats.shrinks); 858 fprintf(fp, " number of compresses: %u\n", table->stats.compresses); 859 fprintf(fp, "number of enumerate shrinks: %u\n", table->stats.enumShrinks); 860 861 if (dump && maxChainLen && hash2) { 862 fputs("Maximum hash chain:\n", fp); 863 hash1 = maxChainHash1; 864 hash2 = maxChainHash2; 865 entry = ADDRESS_ENTRY(table, hash1); 866 i = 0; 867 do { 868 if (dump(table, entry, i++, fp) != JS_DHASH_NEXT) 869 break; 870 hash1 -= hash2; 871 hash1 &= sizeMask; 872 entry = ADDRESS_ENTRY(table, hash1); 873 } while (JS_DHASH_ENTRY_IS_BUSY(entry)); 874 } 875} 876#endif /* JS_DHASHMETER */