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