1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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4 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
6 * The contents of this file are subject to the Mozilla Public License Version
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16 * The Original Code is Mozilla Communicator client code, released
19 * The Initial Developer of the Original Code is
20 * Netscape Communications Corporation.
21 * Portions created by the Initial Developer are Copyright (C) 1998
22 * the Initial Developer. All Rights Reserved.
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38 * ***** END LICENSE BLOCK ***** */
41 * PR hash table package.
51 /* Compute the number of buckets in ht */
52 #define NBUCKETS(ht) JS_BIT(JS_HASH_BITS - (ht)->shift)
54 /* The smallest table has 16 buckets */
55 #define MINBUCKETSLOG2 4
56 #define MINBUCKETS JS_BIT(MINBUCKETSLOG2)
58 /* Compute the maximum entries given n buckets that we will tolerate, ~90% */
59 #define OVERLOADED(n) ((n) - ((n) >> 3))
61 /* Compute the number of entries below which we shrink the table by half */
62 #define UNDERLOADED(n) (((n) > MINBUCKETS) ? ((n) >> 2) : 0)
65 ** Stubs for default hash allocator ops.
68 DefaultAllocTable(void *pool, size_t size)
70 return js_malloc(size);
74 DefaultFreeTable(void *pool, void *item, size_t size)
80 DefaultAllocEntry(void *pool, const void *key)
82 return (JSHashEntry*) js_malloc(sizeof(JSHashEntry));
86 DefaultFreeEntry(void *pool, JSHashEntry *he, uintN flag)
88 if (flag == HT_FREE_ENTRY)
92 static JSHashAllocOps defaultHashAllocOps = {
93 DefaultAllocTable, DefaultFreeTable,
94 DefaultAllocEntry, DefaultFreeEntry
97 JS_PUBLIC_API(JSHashTable *)
98 JS_NewHashTable(uint32 n, JSHashFunction keyHash,
99 JSHashComparator keyCompare, JSHashComparator valueCompare,
100 JSHashAllocOps *allocOps, void *allocPriv)
105 if (n <= MINBUCKETS) {
108 n = JS_CeilingLog2(n);
113 if (!allocOps) allocOps = &defaultHashAllocOps;
115 ht = (JSHashTable*) allocOps->allocTable(allocPriv, sizeof *ht);
118 memset(ht, 0, sizeof *ht);
119 ht->shift = JS_HASH_BITS - n;
121 nb = n * sizeof(JSHashEntry *);
122 ht->buckets = (JSHashEntry**) allocOps->allocTable(allocPriv, nb);
124 allocOps->freeTable(allocPriv, ht, nb);
127 memset(ht->buckets, 0, nb);
129 ht->keyHash = keyHash;
130 ht->keyCompare = keyCompare;
131 ht->valueCompare = valueCompare;
132 ht->allocOps = allocOps;
133 ht->allocPriv = allocPriv;
138 JS_HashTableDestroy(JSHashTable *ht)
141 JSHashEntry *he, **hep;
142 JSHashAllocOps *allocOps = ht->allocOps;
143 void *allocPriv = ht->allocPriv;
146 for (i = 0; i < n; i++) {
147 hep = &ht->buckets[i];
148 while ((he = *hep) != NULL) {
150 allocOps->freeEntry(allocPriv, he, HT_FREE_ENTRY);
154 memset(ht->buckets, 0xDB, n * sizeof ht->buckets[0]);
156 allocOps->freeTable(allocPriv, ht->buckets, n * sizeof ht->buckets[0]);
158 memset(ht, 0xDB, sizeof *ht);
160 allocOps->freeTable(allocPriv, ht, sizeof *ht);
164 * Multiplicative hash, from Knuth 6.4.
166 #define BUCKET_HEAD(ht, keyHash) \
167 (&(ht)->buckets[((keyHash) * JS_GOLDEN_RATIO) >> (ht)->shift])
169 JS_PUBLIC_API(JSHashEntry **)
170 JS_HashTableRawLookup(JSHashTable *ht, JSHashNumber keyHash, const void *key)
172 JSHashEntry *he, **hep, **hep0;
177 hep = hep0 = BUCKET_HEAD(ht, keyHash);
178 while ((he = *hep) != NULL) {
179 if (he->keyHash == keyHash && ht->keyCompare(key, he->key)) {
180 /* Move to front of chain if not already there */
197 Resize(JSHashTable *ht, uint32 newshift)
199 size_t nb, nentries, i;
200 JSHashEntry **oldbuckets, *he, *next, **hep;
201 size_t nold = NBUCKETS(ht);
203 JS_ASSERT(newshift < JS_HASH_BITS);
205 nb = (size_t)1 << (JS_HASH_BITS - newshift);
207 /* Integer overflow protection. */
208 if (nb > (size_t)-1 / sizeof(JSHashEntry*))
210 nb *= sizeof(JSHashEntry*);
212 oldbuckets = ht->buckets;
213 ht->buckets = (JSHashEntry**)ht->allocOps->allocTable(ht->allocPriv, nb);
215 ht->buckets = oldbuckets;
218 memset(ht->buckets, 0, nb);
220 ht->shift = newshift;
221 nentries = ht->nentries;
223 for (i = 0; nentries != 0; i++) {
224 for (he = oldbuckets[i]; he; he = next) {
225 JS_ASSERT(nentries != 0);
228 hep = BUCKET_HEAD(ht, he->keyHash);
231 * We do not require unique entries, instead appending he to the
232 * chain starting at hep.
241 memset(oldbuckets, 0xDB, nold * sizeof oldbuckets[0]);
243 ht->allocOps->freeTable(ht->allocPriv, oldbuckets,
244 nold * sizeof oldbuckets[0]);
248 JS_PUBLIC_API(JSHashEntry *)
249 JS_HashTableRawAdd(JSHashTable *ht, JSHashEntry **&hep,
250 JSHashNumber keyHash, const void *key, void *value)
255 /* Grow the table if it is overloaded */
257 if (ht->nentries >= OVERLOADED(n)) {
258 if (!Resize(ht, ht->shift - 1))
263 hep = JS_HashTableRawLookup(ht, keyHash, key);
266 /* Make a new key value entry */
267 he = ht->allocOps->allocEntry(ht->allocPriv, key);
270 he->keyHash = keyHash;
279 JS_PUBLIC_API(JSHashEntry *)
280 JS_HashTableAdd(JSHashTable *ht, const void *key, void *value)
282 JSHashNumber keyHash;
283 JSHashEntry *he, **hep;
285 keyHash = ht->keyHash(key);
286 hep = JS_HashTableRawLookup(ht, keyHash, key);
287 if ((he = *hep) != NULL) {
288 /* Hit; see if values match */
289 if (ht->valueCompare(he->value, value)) {
290 /* key,value pair is already present in table */
294 ht->allocOps->freeEntry(ht->allocPriv, he, HT_FREE_VALUE);
298 return JS_HashTableRawAdd(ht, hep, keyHash, key, value);
302 JS_HashTableRawRemove(JSHashTable *ht, JSHashEntry **hep, JSHashEntry *he)
307 ht->allocOps->freeEntry(ht->allocPriv, he, HT_FREE_ENTRY);
309 /* Shrink table if it's underloaded */
311 if (--ht->nentries < UNDERLOADED(n)) {
312 Resize(ht, ht->shift + 1);
319 JS_PUBLIC_API(JSBool)
320 JS_HashTableRemove(JSHashTable *ht, const void *key)
322 JSHashNumber keyHash;
323 JSHashEntry *he, **hep;
325 keyHash = ht->keyHash(key);
326 hep = JS_HashTableRawLookup(ht, keyHash, key);
327 if ((he = *hep) == NULL)
330 /* Hit; remove element */
331 JS_HashTableRawRemove(ht, hep, he);
335 JS_PUBLIC_API(void *)
336 JS_HashTableLookup(JSHashTable *ht, const void *key)
338 JSHashNumber keyHash;
339 JSHashEntry *he, **hep;
341 keyHash = ht->keyHash(key);
342 hep = JS_HashTableRawLookup(ht, keyHash, key);
343 if ((he = *hep) != NULL) {
350 ** Iterate over the entries in the hash table calling func for each
351 ** entry found. Stop if "f" says to (return value & JS_ENUMERATE_STOP).
352 ** Return a count of the number of elements scanned.
355 JS_HashTableEnumerateEntries(JSHashTable *ht, JSHashEnumerator f, void *arg)
357 JSHashEntry *he, **hep, **bucket;
358 uint32 nlimit, n, nbuckets, newlog2;
361 nlimit = ht->nentries;
363 for (bucket = ht->buckets; n != nlimit; ++bucket) {
365 while ((he = *hep) != NULL) {
366 JS_ASSERT(n < nlimit);
369 if (rv & HT_ENUMERATE_REMOVE) {
371 ht->allocOps->freeEntry(ht->allocPriv, he, HT_FREE_ENTRY);
376 if (rv & HT_ENUMERATE_STOP) {
383 /* Shrink table if removal of entries made it underloaded */
384 if (ht->nentries != nlimit) {
385 JS_ASSERT(ht->nentries < nlimit);
386 nbuckets = NBUCKETS(ht);
387 if (MINBUCKETS < nbuckets && ht->nentries < UNDERLOADED(nbuckets)) {
388 newlog2 = JS_CeilingLog2(ht->nentries);
389 if (newlog2 < MINBUCKETSLOG2)
390 newlog2 = MINBUCKETSLOG2;
392 /* Check that we really shrink the table. */
393 JS_ASSERT(JS_HASH_BITS - ht->shift > newlog2);
394 Resize(ht, JS_HASH_BITS - newlog2);
404 JS_HashTableDumpMeter(JSHashTable *ht, JSHashEnumerator dump, FILE *fp)
406 double sqsum, mean, sigma;
407 uint32 nchains, nbuckets;
408 uint32 i, n, maxChain, maxChainLen;
413 maxChain = maxChainLen = 0;
414 nbuckets = NBUCKETS(ht);
415 for (i = 0; i < nbuckets; i++) {
420 for (n = 0; he; he = he->next)
423 if (n > maxChainLen) {
429 mean = JS_MeanAndStdDev(nchains, ht->nentries, sqsum, &sigma);
431 fprintf(fp, "\nHash table statistics:\n");
432 fprintf(fp, " number of lookups: %u\n", ht->nlookups);
433 fprintf(fp, " number of entries: %u\n", ht->nentries);
434 fprintf(fp, " number of grows: %u\n", ht->ngrows);
435 fprintf(fp, " number of shrinks: %u\n", ht->nshrinks);
436 fprintf(fp, " mean steps per hash: %g\n", (double)ht->nsteps
438 fprintf(fp, "mean hash chain length: %g\n", mean);
439 fprintf(fp, " standard deviation: %g\n", sigma);
440 fprintf(fp, " max hash chain length: %u\n", maxChainLen);
441 fprintf(fp, " max hash chain: [%u]\n", maxChain);
443 for (he = ht->buckets[maxChain], i = 0; he; he = he->next, i++)
444 if (dump(he, i, fp) != HT_ENUMERATE_NEXT)
447 #endif /* JS_HASHMETER */
450 JS_HashTableDump(JSHashTable *ht, JSHashEnumerator dump, FILE *fp)
454 count = JS_HashTableEnumerateEntries(ht, dump, fp);
456 JS_HashTableDumpMeter(ht, dump, fp);
461 JS_PUBLIC_API(JSHashNumber)
462 JS_HashString(const void *key)
465 const unsigned char *s;
468 for (s = (const unsigned char *)key; *s; s++)
469 h = JS_ROTATE_LEFT32(h, 4) ^ *s;
474 JS_CompareValues(const void *v1, const void *v2)