/js/lib/Socket.IO-node/support/expresso/deps/jscoverage/js/jsdhash.h
C++ Header | 588 lines | 179 code | 53 blank | 356 comment | 5 complexity | 9c63a295f020457f52047cd26f4f2fda MD5 | raw file
Possible License(s): GPL-2.0, LGPL-2.1, MPL-2.0-no-copyleft-exception, BSD-3-Clause
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 * 25 * Alternatively, the contents of this file may be used under the terms of 26 * either of the GNU General Public License Version 2 or later (the "GPL"), 27 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"), 28 * in which case the provisions of the GPL or the LGPL are applicable instead 29 * of those above. If you wish to allow use of your version of this file only 30 * under the terms of either the GPL or the LGPL, and not to allow others to 31 * use your version of this file under the terms of the MPL, indicate your 32 * decision by deleting the provisions above and replace them with the notice 33 * and other provisions required by the GPL or the LGPL. If you do not delete 34 * the provisions above, a recipient may use your version of this file under 35 * the terms of any one of the MPL, the GPL or the LGPL. 36 * 37 * ***** END LICENSE BLOCK ***** */ 38 39#ifndef jsdhash_h___ 40#define jsdhash_h___ 41/* 42 * Double hashing, a la Knuth 6. 43 */ 44#include "jstypes.h" 45 46JS_BEGIN_EXTERN_C 47 48#if defined(__GNUC__) && defined(__i386__) && (__GNUC__ >= 3) && !defined(XP_OS2) 49#define JS_DHASH_FASTCALL __attribute__ ((regparm (3),stdcall)) 50#elif defined(XP_WIN) 51#define JS_DHASH_FASTCALL __fastcall 52#else 53#define JS_DHASH_FASTCALL 54#endif 55 56#ifdef DEBUG_XXXbrendan 57#define JS_DHASHMETER 1 58#endif 59 60/* Table size limit, do not equal or exceed (see min&maxAlphaFrac, below). */ 61#undef JS_DHASH_SIZE_LIMIT 62#define JS_DHASH_SIZE_LIMIT JS_BIT(24) 63 64/* Minimum table size, or gross entry count (net is at most .75 loaded). */ 65#ifndef JS_DHASH_MIN_SIZE 66#define JS_DHASH_MIN_SIZE 16 67#elif (JS_DHASH_MIN_SIZE & (JS_DHASH_MIN_SIZE - 1)) != 0 68#error "JS_DHASH_MIN_SIZE must be a power of two!" 69#endif 70 71/* 72 * Multiplicative hash uses an unsigned 32 bit integer and the golden ratio, 73 * expressed as a fixed-point 32-bit fraction. 74 */ 75#define JS_DHASH_BITS 32 76#define JS_DHASH_GOLDEN_RATIO 0x9E3779B9U 77 78/* Primitive and forward-struct typedefs. */ 79typedef uint32 JSDHashNumber; 80typedef struct JSDHashEntryHdr JSDHashEntryHdr; 81typedef struct JSDHashEntryStub JSDHashEntryStub; 82typedef struct JSDHashTable JSDHashTable; 83typedef struct JSDHashTableOps JSDHashTableOps; 84 85/* 86 * Table entry header structure. 87 * 88 * In order to allow in-line allocation of key and value, we do not declare 89 * either here. Instead, the API uses const void *key as a formal parameter. 90 * The key need not be stored in the entry; it may be part of the value, but 91 * need not be stored at all. 92 * 93 * Callback types are defined below and grouped into the JSDHashTableOps 94 * structure, for single static initialization per hash table sub-type. 95 * 96 * Each hash table sub-type should nest the JSDHashEntryHdr structure at the 97 * front of its particular entry type. The keyHash member contains the result 98 * of multiplying the hash code returned from the hashKey callback (see below) 99 * by JS_DHASH_GOLDEN_RATIO, then constraining the result to avoid the magic 0 100 * and 1 values. The stored keyHash value is table size invariant, and it is 101 * maintained automatically by JS_DHashTableOperate -- users should never set 102 * it, and its only uses should be via the entry macros below. 103 * 104 * The JS_DHASH_ENTRY_IS_LIVE macro tests whether entry is neither free nor 105 * removed. An entry may be either busy or free; if busy, it may be live or 106 * removed. Consumers of this API should not access members of entries that 107 * are not live. 108 * 109 * However, use JS_DHASH_ENTRY_IS_BUSY for faster liveness testing of entries 110 * returned by JS_DHashTableOperate, as JS_DHashTableOperate never returns a 111 * non-live, busy (i.e., removed) entry pointer to its caller. See below for 112 * more details on JS_DHashTableOperate's calling rules. 113 */ 114struct JSDHashEntryHdr { 115 JSDHashNumber keyHash; /* every entry must begin like this */ 116}; 117 118#define JS_DHASH_ENTRY_IS_FREE(entry) ((entry)->keyHash == 0) 119#define JS_DHASH_ENTRY_IS_BUSY(entry) (!JS_DHASH_ENTRY_IS_FREE(entry)) 120#define JS_DHASH_ENTRY_IS_LIVE(entry) ((entry)->keyHash >= 2) 121 122/* 123 * A JSDHashTable is currently 8 words (without the JS_DHASHMETER overhead) 124 * on most architectures, and may be allocated on the stack or within another 125 * structure or class (see below for the Init and Finish functions to use). 126 * 127 * To decide whether to use double hashing vs. chaining, we need to develop a 128 * trade-off relation, as follows: 129 * 130 * Let alpha be the load factor, esize the entry size in words, count the 131 * entry count, and pow2 the power-of-two table size in entries. 132 * 133 * (JSDHashTable overhead) > (JSHashTable overhead) 134 * (unused table entry space) > (malloc and .next overhead per entry) + 135 * (buckets overhead) 136 * (1 - alpha) * esize * pow2 > 2 * count + pow2 137 * 138 * Notice that alpha is by definition (count / pow2): 139 * 140 * (1 - alpha) * esize * pow2 > 2 * alpha * pow2 + pow2 141 * (1 - alpha) * esize > 2 * alpha + 1 142 * 143 * esize > (1 + 2 * alpha) / (1 - alpha) 144 * 145 * This assumes both tables must keep keyHash, key, and value for each entry, 146 * where key and value point to separately allocated strings or structures. 147 * If key and value can be combined into one pointer, then the trade-off is: 148 * 149 * esize > (1 + 3 * alpha) / (1 - alpha) 150 * 151 * If the entry value can be a subtype of JSDHashEntryHdr, rather than a type 152 * that must be allocated separately and referenced by an entry.value pointer 153 * member, and provided key's allocation can be fused with its entry's, then 154 * k (the words wasted per entry with chaining) is 4. 155 * 156 * To see these curves, feed gnuplot input like so: 157 * 158 * gnuplot> f(x,k) = (1 + k * x) / (1 - x) 159 * gnuplot> plot [0:.75] f(x,2), f(x,3), f(x,4) 160 * 161 * For k of 2 and a well-loaded table (alpha > .5), esize must be more than 4 162 * words for chaining to be more space-efficient than double hashing. 163 * 164 * Solving for alpha helps us decide when to shrink an underloaded table: 165 * 166 * esize > (1 + k * alpha) / (1 - alpha) 167 * esize - alpha * esize > 1 + k * alpha 168 * esize - 1 > (k + esize) * alpha 169 * (esize - 1) / (k + esize) > alpha 170 * 171 * alpha < (esize - 1) / (esize + k) 172 * 173 * Therefore double hashing should keep alpha >= (esize - 1) / (esize + k), 174 * assuming esize is not too large (in which case, chaining should probably be 175 * used for any alpha). For esize=2 and k=3, we want alpha >= .2; for esize=3 176 * and k=2, we want alpha >= .4. For k=4, esize could be 6, and alpha >= .5 177 * would still obtain. See the JS_DHASH_MIN_ALPHA macro further below. 178 * 179 * The current implementation uses a configurable lower bound on alpha, which 180 * defaults to .25, when deciding to shrink the table (while still respecting 181 * JS_DHASH_MIN_SIZE). 182 * 183 * Note a qualitative difference between chaining and double hashing: under 184 * chaining, entry addresses are stable across table shrinks and grows. With 185 * double hashing, you can't safely hold an entry pointer and use it after an 186 * ADD or REMOVE operation, unless you sample table->generation before adding 187 * or removing, and compare the sample after, dereferencing the entry pointer 188 * only if table->generation has not changed. 189 * 190 * The moral of this story: there is no one-size-fits-all hash table scheme, 191 * but for small table entry size, and assuming entry address stability is not 192 * required, double hashing wins. 193 */ 194struct JSDHashTable { 195 const JSDHashTableOps *ops; /* virtual operations, see below */ 196 void *data; /* ops- and instance-specific data */ 197 int16 hashShift; /* multiplicative hash shift */ 198 uint8 maxAlphaFrac; /* 8-bit fixed point max alpha */ 199 uint8 minAlphaFrac; /* 8-bit fixed point min alpha */ 200 uint32 entrySize; /* number of bytes in an entry */ 201 uint32 entryCount; /* number of entries in table */ 202 uint32 removedCount; /* removed entry sentinels in table */ 203 uint32 generation; /* entry storage generation number */ 204 char *entryStore; /* entry storage */ 205#ifdef JS_DHASHMETER 206 struct JSDHashStats { 207 uint32 searches; /* total number of table searches */ 208 uint32 steps; /* hash chain links traversed */ 209 uint32 hits; /* searches that found key */ 210 uint32 misses; /* searches that didn't find key */ 211 uint32 lookups; /* number of JS_DHASH_LOOKUPs */ 212 uint32 addMisses; /* adds that miss, and do work */ 213 uint32 addOverRemoved; /* adds that recycled a removed entry */ 214 uint32 addHits; /* adds that hit an existing entry */ 215 uint32 addFailures; /* out-of-memory during add growth */ 216 uint32 removeHits; /* removes that hit, and do work */ 217 uint32 removeMisses; /* useless removes that miss */ 218 uint32 removeFrees; /* removes that freed entry directly */ 219 uint32 removeEnums; /* removes done by Enumerate */ 220 uint32 grows; /* table expansions */ 221 uint32 shrinks; /* table contractions */ 222 uint32 compresses; /* table compressions */ 223 uint32 enumShrinks; /* contractions after Enumerate */ 224 } stats; 225#endif 226}; 227 228/* 229 * Size in entries (gross, not net of free and removed sentinels) for table. 230 * We store hashShift rather than sizeLog2 to optimize the collision-free case 231 * in SearchTable. 232 */ 233#define JS_DHASH_TABLE_SIZE(table) JS_BIT(JS_DHASH_BITS - (table)->hashShift) 234 235/* 236 * Table space at entryStore is allocated and freed using these callbacks. 237 * The allocator should return null on error only (not if called with nbytes 238 * equal to 0; but note that jsdhash.c code will never call with 0 nbytes). 239 */ 240typedef void * 241(* JSDHashAllocTable)(JSDHashTable *table, uint32 nbytes); 242 243typedef void 244(* JSDHashFreeTable) (JSDHashTable *table, void *ptr); 245 246/* 247 * Compute the hash code for a given key to be looked up, added, or removed 248 * from table. A hash code may have any JSDHashNumber value. 249 */ 250typedef JSDHashNumber 251(* JSDHashHashKey) (JSDHashTable *table, const void *key); 252 253/* 254 * Compare the key identifying entry in table with the provided key parameter. 255 * Return JS_TRUE if keys match, JS_FALSE otherwise. 256 */ 257typedef JSBool 258(* JSDHashMatchEntry)(JSDHashTable *table, const JSDHashEntryHdr *entry, 259 const void *key); 260 261/* 262 * Copy the data starting at from to the new entry storage at to. Do not add 263 * reference counts for any strong references in the entry, however, as this 264 * is a "move" operation: the old entry storage at from will be freed without 265 * any reference-decrementing callback shortly. 266 */ 267typedef void 268(* JSDHashMoveEntry)(JSDHashTable *table, const JSDHashEntryHdr *from, 269 JSDHashEntryHdr *to); 270 271/* 272 * Clear the entry and drop any strong references it holds. This callback is 273 * invoked during a JS_DHASH_REMOVE operation (see below for operation codes), 274 * but only if the given key is found in the table. 275 */ 276typedef void 277(* JSDHashClearEntry)(JSDHashTable *table, JSDHashEntryHdr *entry); 278 279/* 280 * Called when a table (whether allocated dynamically by itself, or nested in 281 * a larger structure, or allocated on the stack) is finished. This callback 282 * allows table->ops-specific code to finalize table->data. 283 */ 284typedef void 285(* JSDHashFinalize) (JSDHashTable *table); 286 287/* 288 * Initialize a new entry, apart from keyHash. This function is called when 289 * JS_DHashTableOperate's JS_DHASH_ADD case finds no existing entry for the 290 * given key, and must add a new one. At that point, entry->keyHash is not 291 * set yet, to avoid claiming the last free entry in a severely overloaded 292 * table. 293 */ 294typedef JSBool 295(* JSDHashInitEntry)(JSDHashTable *table, JSDHashEntryHdr *entry, 296 const void *key); 297 298/* 299 * Finally, the "vtable" structure for JSDHashTable. The first eight hooks 300 * must be provided by implementations; they're called unconditionally by the 301 * generic jsdhash.c code. Hooks after these may be null. 302 * 303 * Summary of allocation-related hook usage with C++ placement new emphasis: 304 * allocTable Allocate raw bytes with malloc, no ctors run. 305 * freeTable Free raw bytes with free, no dtors run. 306 * initEntry Call placement new using default key-based ctor. 307 * Return JS_TRUE on success, JS_FALSE on error. 308 * moveEntry Call placement new using copy ctor, run dtor on old 309 * entry storage. 310 * clearEntry Run dtor on entry. 311 * finalize Stub unless table->data was initialized and needs to 312 * be finalized. 313 * 314 * Note the reason why initEntry is optional: the default hooks (stubs) clear 315 * entry storage: On successful JS_DHashTableOperate(tbl, key, JS_DHASH_ADD), 316 * the returned entry pointer addresses an entry struct whose keyHash member 317 * has been set non-zero, but all other entry members are still clear (null). 318 * JS_DHASH_ADD callers can test such members to see whether the entry was 319 * newly created by the JS_DHASH_ADD call that just succeeded. If placement 320 * new or similar initialization is required, define an initEntry hook. Of 321 * course, the clearEntry hook must zero or null appropriately. 322 * 323 * XXX assumes 0 is null for pointer types. 324 */ 325struct JSDHashTableOps { 326 /* Mandatory hooks. All implementations must provide these. */ 327 JSDHashAllocTable allocTable; 328 JSDHashFreeTable freeTable; 329 JSDHashHashKey hashKey; 330 JSDHashMatchEntry matchEntry; 331 JSDHashMoveEntry moveEntry; 332 JSDHashClearEntry clearEntry; 333 JSDHashFinalize finalize; 334 335 /* Optional hooks start here. If null, these are not called. */ 336 JSDHashInitEntry initEntry; 337}; 338 339/* 340 * Default implementations for the above ops. 341 */ 342extern JS_PUBLIC_API(void *) 343JS_DHashAllocTable(JSDHashTable *table, uint32 nbytes); 344 345extern JS_PUBLIC_API(void) 346JS_DHashFreeTable(JSDHashTable *table, void *ptr); 347 348extern JS_PUBLIC_API(JSDHashNumber) 349JS_DHashStringKey(JSDHashTable *table, const void *key); 350 351/* A minimal entry contains a keyHash header and a void key pointer. */ 352struct JSDHashEntryStub { 353 JSDHashEntryHdr hdr; 354 const void *key; 355}; 356 357extern JS_PUBLIC_API(JSDHashNumber) 358JS_DHashVoidPtrKeyStub(JSDHashTable *table, const void *key); 359 360extern JS_PUBLIC_API(JSBool) 361JS_DHashMatchEntryStub(JSDHashTable *table, 362 const JSDHashEntryHdr *entry, 363 const void *key); 364 365extern JS_PUBLIC_API(JSBool) 366JS_DHashMatchStringKey(JSDHashTable *table, 367 const JSDHashEntryHdr *entry, 368 const void *key); 369 370extern JS_PUBLIC_API(void) 371JS_DHashMoveEntryStub(JSDHashTable *table, 372 const JSDHashEntryHdr *from, 373 JSDHashEntryHdr *to); 374 375extern JS_PUBLIC_API(void) 376JS_DHashClearEntryStub(JSDHashTable *table, JSDHashEntryHdr *entry); 377 378extern JS_PUBLIC_API(void) 379JS_DHashFreeStringKey(JSDHashTable *table, JSDHashEntryHdr *entry); 380 381extern JS_PUBLIC_API(void) 382JS_DHashFinalizeStub(JSDHashTable *table); 383 384/* 385 * If you use JSDHashEntryStub or a subclass of it as your entry struct, and 386 * if your entries move via memcpy and clear via memset(0), you can use these 387 * stub operations. 388 */ 389extern JS_PUBLIC_API(const JSDHashTableOps *) 390JS_DHashGetStubOps(void); 391 392/* 393 * Dynamically allocate a new JSDHashTable using malloc, initialize it using 394 * JS_DHashTableInit, and return its address. Return null on malloc failure. 395 * Note that the entry storage at table->entryStore will be allocated using 396 * the ops->allocTable callback. 397 */ 398extern JS_PUBLIC_API(JSDHashTable *) 399JS_NewDHashTable(const JSDHashTableOps *ops, void *data, uint32 entrySize, 400 uint32 capacity); 401 402/* 403 * Finalize table's data, free its entry storage (via table->ops->freeTable), 404 * and return the memory starting at table to the malloc heap. 405 */ 406extern JS_PUBLIC_API(void) 407JS_DHashTableDestroy(JSDHashTable *table); 408 409/* 410 * Initialize table with ops, data, entrySize, and capacity. Capacity is a 411 * guess for the smallest table size at which the table will usually be less 412 * than 75% loaded (the table will grow or shrink as needed; capacity serves 413 * only to avoid inevitable early growth from JS_DHASH_MIN_SIZE). 414 */ 415extern JS_PUBLIC_API(JSBool) 416JS_DHashTableInit(JSDHashTable *table, const JSDHashTableOps *ops, void *data, 417 uint32 entrySize, uint32 capacity); 418 419/* 420 * Set maximum and minimum alpha for table. The defaults are 0.75 and .25. 421 * maxAlpha must be in [0.5, 0.9375] for the default JS_DHASH_MIN_SIZE; or if 422 * MinSize=JS_DHASH_MIN_SIZE <= 256, in [0.5, (float)(MinSize-1)/MinSize]; or 423 * else in [0.5, 255.0/256]. minAlpha must be in [0, maxAlpha / 2), so that 424 * we don't shrink on the very next remove after growing a table upon adding 425 * an entry that brings entryCount past maxAlpha * tableSize. 426 */ 427extern JS_PUBLIC_API(void) 428JS_DHashTableSetAlphaBounds(JSDHashTable *table, 429 float maxAlpha, 430 float minAlpha); 431 432/* 433 * Call this macro with k, the number of pointer-sized words wasted per entry 434 * under chaining, to compute the minimum alpha at which double hashing still 435 * beats chaining. 436 */ 437#define JS_DHASH_MIN_ALPHA(table, k) \ 438 ((float)((table)->entrySize / sizeof(void *) - 1) \ 439 / ((table)->entrySize / sizeof(void *) + (k))) 440 441/* 442 * Default max/min alpha, and macros to compute the value for the |capacity| 443 * parameter to JS_NewDHashTable and JS_DHashTableInit, given default or any 444 * max alpha, such that adding entryCount entries right after initializing the 445 * table will not require a reallocation (so JS_DHASH_ADD can't fail for those 446 * JS_DHashTableOperate calls). 447 * 448 * NB: JS_DHASH_CAP is a helper macro meant for use only in JS_DHASH_CAPACITY. 449 * Don't use it directly! 450 */ 451#define JS_DHASH_DEFAULT_MAX_ALPHA 0.75 452#define JS_DHASH_DEFAULT_MIN_ALPHA 0.25 453 454#define JS_DHASH_CAP(entryCount, maxAlpha) \ 455 ((uint32)((double)(entryCount) / (maxAlpha))) 456 457#define JS_DHASH_CAPACITY(entryCount, maxAlpha) \ 458 (JS_DHASH_CAP(entryCount, maxAlpha) + \ 459 (((JS_DHASH_CAP(entryCount, maxAlpha) * (uint8)(0x100 * (maxAlpha))) \ 460 >> 8) < (entryCount))) 461 462#define JS_DHASH_DEFAULT_CAPACITY(entryCount) \ 463 JS_DHASH_CAPACITY(entryCount, JS_DHASH_DEFAULT_MAX_ALPHA) 464 465/* 466 * Finalize table's data, free its entry storage using table->ops->freeTable, 467 * and leave its members unchanged from their last live values (which leaves 468 * pointers dangling). If you want to burn cycles clearing table, it's up to 469 * your code to call memset. 470 */ 471extern JS_PUBLIC_API(void) 472JS_DHashTableFinish(JSDHashTable *table); 473 474/* 475 * To consolidate keyHash computation and table grow/shrink code, we use a 476 * single entry point for lookup, add, and remove operations. The operation 477 * codes are declared here, along with codes returned by JSDHashEnumerator 478 * functions, which control JS_DHashTableEnumerate's behavior. 479 */ 480typedef enum JSDHashOperator { 481 JS_DHASH_LOOKUP = 0, /* lookup entry */ 482 JS_DHASH_ADD = 1, /* add entry */ 483 JS_DHASH_REMOVE = 2, /* remove entry, or enumerator says remove */ 484 JS_DHASH_NEXT = 0, /* enumerator says continue */ 485 JS_DHASH_STOP = 1 /* enumerator says stop */ 486} JSDHashOperator; 487 488/* 489 * To lookup a key in table, call: 490 * 491 * entry = JS_DHashTableOperate(table, key, JS_DHASH_LOOKUP); 492 * 493 * If JS_DHASH_ENTRY_IS_BUSY(entry) is true, key was found and it identifies 494 * entry. If JS_DHASH_ENTRY_IS_FREE(entry) is true, key was not found. 495 * 496 * To add an entry identified by key to table, call: 497 * 498 * entry = JS_DHashTableOperate(table, key, JS_DHASH_ADD); 499 * 500 * If entry is null upon return, then either the table is severely overloaded, 501 * and memory can't be allocated for entry storage via table->ops->allocTable; 502 * Or if table->ops->initEntry is non-null, the table->ops->initEntry op may 503 * have returned false. 504 * 505 * Otherwise, entry->keyHash has been set so that JS_DHASH_ENTRY_IS_BUSY(entry) 506 * is true, and it is up to the caller to initialize the key and value parts 507 * of the entry sub-type, if they have not been set already (i.e. if entry was 508 * not already in the table, and if the optional initEntry hook was not used). 509 * 510 * To remove an entry identified by key from table, call: 511 * 512 * (void) JS_DHashTableOperate(table, key, JS_DHASH_REMOVE); 513 * 514 * If key's entry is found, it is cleared (via table->ops->clearEntry) and 515 * the entry is marked so that JS_DHASH_ENTRY_IS_FREE(entry). This operation 516 * returns null unconditionally; you should ignore its return value. 517 */ 518extern JS_PUBLIC_API(JSDHashEntryHdr *) JS_DHASH_FASTCALL 519JS_DHashTableOperate(JSDHashTable *table, const void *key, JSDHashOperator op); 520 521/* 522 * Remove an entry already accessed via LOOKUP or ADD. 523 * 524 * NB: this is a "raw" or low-level routine, intended to be used only where 525 * the inefficiency of a full JS_DHashTableOperate (which rehashes in order 526 * to find the entry given its key) is not tolerable. This function does not 527 * shrink the table if it is underloaded. It does not update stats #ifdef 528 * JS_DHASHMETER, either. 529 */ 530extern JS_PUBLIC_API(void) 531JS_DHashTableRawRemove(JSDHashTable *table, JSDHashEntryHdr *entry); 532 533/* 534 * Enumerate entries in table using etor: 535 * 536 * count = JS_DHashTableEnumerate(table, etor, arg); 537 * 538 * JS_DHashTableEnumerate calls etor like so: 539 * 540 * op = etor(table, entry, number, arg); 541 * 542 * where number is a zero-based ordinal assigned to live entries according to 543 * their order in table->entryStore. 544 * 545 * The return value, op, is treated as a set of flags. If op is JS_DHASH_NEXT, 546 * then continue enumerating. If op contains JS_DHASH_REMOVE, then clear (via 547 * table->ops->clearEntry) and free entry. Then we check whether op contains 548 * JS_DHASH_STOP; if so, stop enumerating and return the number of live entries 549 * that were enumerated so far. Return the total number of live entries when 550 * enumeration completes normally. 551 * 552 * If etor calls JS_DHashTableOperate on table with op != JS_DHASH_LOOKUP, it 553 * must return JS_DHASH_STOP; otherwise undefined behavior results. 554 * 555 * If any enumerator returns JS_DHASH_REMOVE, table->entryStore may be shrunk 556 * or compressed after enumeration, but before JS_DHashTableEnumerate returns. 557 * Such an enumerator therefore can't safely set aside entry pointers, but an 558 * enumerator that never returns JS_DHASH_REMOVE can set pointers to entries 559 * aside, e.g., to avoid copying live entries into an array of the entry type. 560 * Copying entry pointers is cheaper, and safe so long as the caller of such a 561 * "stable" Enumerate doesn't use the set-aside pointers after any call either 562 * to PL_DHashTableOperate, or to an "unstable" form of Enumerate, which might 563 * grow or shrink entryStore. 564 * 565 * If your enumerator wants to remove certain entries, but set aside pointers 566 * to other entries that it retains, it can use JS_DHashTableRawRemove on the 567 * entries to be removed, returning JS_DHASH_NEXT to skip them. Likewise, if 568 * you want to remove entries, but for some reason you do not want entryStore 569 * to be shrunk or compressed, you can call JS_DHashTableRawRemove safely on 570 * the entry being enumerated, rather than returning JS_DHASH_REMOVE. 571 */ 572typedef JSDHashOperator 573(* JSDHashEnumerator)(JSDHashTable *table, JSDHashEntryHdr *hdr, uint32 number, 574 void *arg); 575 576extern JS_PUBLIC_API(uint32) 577JS_DHashTableEnumerate(JSDHashTable *table, JSDHashEnumerator etor, void *arg); 578 579#ifdef JS_DHASHMETER 580#include <stdio.h> 581 582extern JS_PUBLIC_API(void) 583JS_DHashTableDumpMeter(JSDHashTable *table, JSDHashEnumerator dump, FILE *fp); 584#endif 585 586JS_END_EXTERN_C 587 588#endif /* jsdhash_h___ */