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Revision 332 - (show annotations)
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Add SpiderMonkey from Firefox 3.1b1.

The following directories and files were removed:
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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
46 JS_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. */
79 typedef uint32 JSDHashNumber;
80 typedef struct JSDHashEntryHdr JSDHashEntryHdr;
81 typedef struct JSDHashEntryStub JSDHashEntryStub;
82 typedef struct JSDHashTable JSDHashTable;
83 typedef 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 */
114 struct 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 */
194 struct 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 */
240 typedef void *
241 (* JSDHashAllocTable)(JSDHashTable *table, uint32 nbytes);
242
243 typedef 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 */
250 typedef 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 */
257 typedef 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 */
267 typedef 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 */
276 typedef 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 */
284 typedef 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 */
294 typedef 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 */
325 struct 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 */
342 extern JS_PUBLIC_API(void *)
343 JS_DHashAllocTable(JSDHashTable *table, uint32 nbytes);
344
345 extern JS_PUBLIC_API(void)
346 JS_DHashFreeTable(JSDHashTable *table, void *ptr);
347
348 extern JS_PUBLIC_API(JSDHashNumber)
349 JS_DHashStringKey(JSDHashTable *table, const void *key);
350
351 /* A minimal entry contains a keyHash header and a void key pointer. */
352 struct JSDHashEntryStub {
353 JSDHashEntryHdr hdr;
354 const void *key;
355 };
356
357 extern JS_PUBLIC_API(JSDHashNumber)
358 JS_DHashVoidPtrKeyStub(JSDHashTable *table, const void *key);
359
360 extern JS_PUBLIC_API(JSBool)
361 JS_DHashMatchEntryStub(JSDHashTable *table,
362 const JSDHashEntryHdr *entry,
363 const void *key);
364
365 extern JS_PUBLIC_API(JSBool)
366 JS_DHashMatchStringKey(JSDHashTable *table,
367 const JSDHashEntryHdr *entry,
368 const void *key);
369
370 extern JS_PUBLIC_API(void)
371 JS_DHashMoveEntryStub(JSDHashTable *table,
372 const JSDHashEntryHdr *from,
373 JSDHashEntryHdr *to);
374
375 extern JS_PUBLIC_API(void)
376 JS_DHashClearEntryStub(JSDHashTable *table, JSDHashEntryHdr *entry);
377
378 extern JS_PUBLIC_API(void)
379 JS_DHashFreeStringKey(JSDHashTable *table, JSDHashEntryHdr *entry);
380
381 extern JS_PUBLIC_API(void)
382 JS_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 */
389 extern JS_PUBLIC_API(const JSDHashTableOps *)
390 JS_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 */
398 extern JS_PUBLIC_API(JSDHashTable *)
399 JS_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 */
406 extern JS_PUBLIC_API(void)
407 JS_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 */
415 extern JS_PUBLIC_API(JSBool)
416 JS_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 */
427 extern JS_PUBLIC_API(void)
428 JS_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 */
471 extern JS_PUBLIC_API(void)
472 JS_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 */
480 typedef 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 */
518 extern JS_PUBLIC_API(JSDHashEntryHdr *) JS_DHASH_FASTCALL
519 JS_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 */
530 extern JS_PUBLIC_API(void)
531 JS_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 */
572 typedef JSDHashOperator
573 (* JSDHashEnumerator)(JSDHashTable *table, JSDHashEntryHdr *hdr, uint32 number,
574 void *arg);
575
576 extern JS_PUBLIC_API(uint32)
577 JS_DHashTableEnumerate(JSDHashTable *table, JSDHashEnumerator etor, void *arg);
578
579 #ifdef JS_DHASHMETER
580 #include <stdio.h>
581
582 extern JS_PUBLIC_API(void)
583 JS_DHashTableDumpMeter(JSDHashTable *table, JSDHashEnumerator dump, FILE *fp);
584 #endif
585
586 JS_END_EXTERN_C
587
588 #endif /* jsdhash_h___ */

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