summaryrefslogtreecommitdiffstats
path: root/nsprpub/lib/ds/plhash.c
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--nsprpub/lib/ds/plhash.c495
1 files changed, 495 insertions, 0 deletions
diff --git a/nsprpub/lib/ds/plhash.c b/nsprpub/lib/ds/plhash.c
new file mode 100644
index 0000000000..95497f06fe
--- /dev/null
+++ b/nsprpub/lib/ds/plhash.c
@@ -0,0 +1,495 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * PL hash table package.
+ */
+#include "plhash.h"
+#include "prbit.h"
+#include "prlog.h"
+#include "prmem.h"
+#include "prtypes.h"
+#include <stdlib.h>
+#include <string.h>
+
+/* Compute the number of buckets in ht */
+#define NBUCKETS(ht) (1 << (PL_HASH_BITS - (ht)->shift))
+
+/* The smallest table has 16 buckets */
+#define MINBUCKETSLOG2 4
+#define MINBUCKETS (1 << MINBUCKETSLOG2)
+
+/* Compute the maximum entries given n buckets that we will tolerate, ~90% */
+#define OVERLOADED(n) ((n) - ((n) >> 3))
+
+/* Compute the number of entries below which we shrink the table by half */
+#define UNDERLOADED(n) (((n) > MINBUCKETS) ? ((n) >> 2) : 0)
+
+/*
+** Stubs for default hash allocator ops.
+*/
+static void * PR_CALLBACK
+DefaultAllocTable(void *pool, PRSize size)
+{
+ return PR_MALLOC(size);
+}
+
+static void PR_CALLBACK
+DefaultFreeTable(void *pool, void *item)
+{
+ PR_Free(item);
+}
+
+static PLHashEntry * PR_CALLBACK
+DefaultAllocEntry(void *pool, const void *key)
+{
+ return PR_NEW(PLHashEntry);
+}
+
+static void PR_CALLBACK
+DefaultFreeEntry(void *pool, PLHashEntry *he, PRUintn flag)
+{
+ if (flag == HT_FREE_ENTRY) {
+ PR_Free(he);
+ }
+}
+
+static PLHashAllocOps defaultHashAllocOps = {
+ DefaultAllocTable, DefaultFreeTable,
+ DefaultAllocEntry, DefaultFreeEntry
+};
+
+PR_IMPLEMENT(PLHashTable *)
+PL_NewHashTable(PRUint32 n, PLHashFunction keyHash,
+ PLHashComparator keyCompare, PLHashComparator valueCompare,
+ const PLHashAllocOps *allocOps, void *allocPriv)
+{
+ PLHashTable *ht;
+ PRSize nb;
+
+ if (n <= MINBUCKETS) {
+ n = MINBUCKETSLOG2;
+ } else {
+ n = PR_CeilingLog2(n);
+ if ((PRInt32)n < 0) {
+ return 0;
+ }
+ }
+
+ if (!allocOps) {
+ allocOps = &defaultHashAllocOps;
+ }
+
+ ht = (PLHashTable*)((*allocOps->allocTable)(allocPriv, sizeof *ht));
+ if (!ht) {
+ return 0;
+ }
+ memset(ht, 0, sizeof *ht);
+ ht->shift = PL_HASH_BITS - n;
+ n = 1 << n;
+ nb = n * sizeof(PLHashEntry *);
+ ht->buckets = (PLHashEntry**)((*allocOps->allocTable)(allocPriv, nb));
+ if (!ht->buckets) {
+ (*allocOps->freeTable)(allocPriv, ht);
+ return 0;
+ }
+ memset(ht->buckets, 0, nb);
+
+ ht->keyHash = keyHash;
+ ht->keyCompare = keyCompare;
+ ht->valueCompare = valueCompare;
+ ht->allocOps = allocOps;
+ ht->allocPriv = allocPriv;
+ return ht;
+}
+
+PR_IMPLEMENT(void)
+PL_HashTableDestroy(PLHashTable *ht)
+{
+ PRUint32 i, n;
+ PLHashEntry *he, *next;
+ const PLHashAllocOps *allocOps = ht->allocOps;
+ void *allocPriv = ht->allocPriv;
+
+ n = NBUCKETS(ht);
+ for (i = 0; i < n; i++) {
+ for (he = ht->buckets[i]; he; he = next) {
+ next = he->next;
+ (*allocOps->freeEntry)(allocPriv, he, HT_FREE_ENTRY);
+ }
+ }
+#ifdef DEBUG
+ memset(ht->buckets, 0xDB, n * sizeof ht->buckets[0]);
+#endif
+ (*allocOps->freeTable)(allocPriv, ht->buckets);
+#ifdef DEBUG
+ memset(ht, 0xDB, sizeof *ht);
+#endif
+ (*allocOps->freeTable)(allocPriv, ht);
+}
+
+/*
+** Multiplicative hash, from Knuth 6.4.
+*/
+#define GOLDEN_RATIO 0x9E3779B9U /* 2/(1+sqrt(5))*(2^32) */
+
+PR_IMPLEMENT(PLHashEntry **)
+PL_HashTableRawLookup(PLHashTable *ht, PLHashNumber keyHash, const void *key)
+{
+ PLHashEntry *he, **hep, **hep0;
+ PLHashNumber h;
+
+#ifdef HASHMETER
+ ht->nlookups++;
+#endif
+ h = keyHash * GOLDEN_RATIO;
+ h >>= ht->shift;
+ hep = hep0 = &ht->buckets[h];
+ while ((he = *hep) != 0) {
+ if (he->keyHash == keyHash && (*ht->keyCompare)(key, he->key)) {
+ /* Move to front of chain if not already there */
+ if (hep != hep0) {
+ *hep = he->next;
+ he->next = *hep0;
+ *hep0 = he;
+ }
+ return hep0;
+ }
+ hep = &he->next;
+#ifdef HASHMETER
+ ht->nsteps++;
+#endif
+ }
+ return hep;
+}
+
+/*
+** Same as PL_HashTableRawLookup but doesn't reorder the hash entries.
+*/
+PR_IMPLEMENT(PLHashEntry **)
+PL_HashTableRawLookupConst(PLHashTable *ht, PLHashNumber keyHash,
+ const void *key)
+{
+ PLHashEntry *he, **hep;
+ PLHashNumber h;
+
+#ifdef HASHMETER
+ ht->nlookups++;
+#endif
+ h = keyHash * GOLDEN_RATIO;
+ h >>= ht->shift;
+ hep = &ht->buckets[h];
+ while ((he = *hep) != 0) {
+ if (he->keyHash == keyHash && (*ht->keyCompare)(key, he->key)) {
+ break;
+ }
+ hep = &he->next;
+#ifdef HASHMETER
+ ht->nsteps++;
+#endif
+ }
+ return hep;
+}
+
+PR_IMPLEMENT(PLHashEntry *)
+PL_HashTableRawAdd(PLHashTable *ht, PLHashEntry **hep,
+ PLHashNumber keyHash, const void *key, void *value)
+{
+ PRUint32 i, n;
+ PLHashEntry *he, *next, **oldbuckets;
+ PRSize nb;
+
+ /* Grow the table if it is overloaded */
+ n = NBUCKETS(ht);
+ if (ht->nentries >= OVERLOADED(n)) {
+ oldbuckets = ht->buckets;
+ nb = 2 * n * sizeof(PLHashEntry *);
+ ht->buckets = (PLHashEntry**)
+ ((*ht->allocOps->allocTable)(ht->allocPriv, nb));
+ if (!ht->buckets) {
+ ht->buckets = oldbuckets;
+ return 0;
+ }
+ memset(ht->buckets, 0, nb);
+#ifdef HASHMETER
+ ht->ngrows++;
+#endif
+ ht->shift--;
+
+ for (i = 0; i < n; i++) {
+ for (he = oldbuckets[i]; he; he = next) {
+ next = he->next;
+ hep = PL_HashTableRawLookup(ht, he->keyHash, he->key);
+ PR_ASSERT(*hep == 0);
+ he->next = 0;
+ *hep = he;
+ }
+ }
+#ifdef DEBUG
+ memset(oldbuckets, 0xDB, n * sizeof oldbuckets[0]);
+#endif
+ (*ht->allocOps->freeTable)(ht->allocPriv, oldbuckets);
+ hep = PL_HashTableRawLookup(ht, keyHash, key);
+ }
+
+ /* Make a new key value entry */
+ he = (*ht->allocOps->allocEntry)(ht->allocPriv, key);
+ if (!he) {
+ return 0;
+ }
+ he->keyHash = keyHash;
+ he->key = key;
+ he->value = value;
+ he->next = *hep;
+ *hep = he;
+ ht->nentries++;
+ return he;
+}
+
+PR_IMPLEMENT(PLHashEntry *)
+PL_HashTableAdd(PLHashTable *ht, const void *key, void *value)
+{
+ PLHashNumber keyHash;
+ PLHashEntry *he, **hep;
+
+ keyHash = (*ht->keyHash)(key);
+ hep = PL_HashTableRawLookup(ht, keyHash, key);
+ if ((he = *hep) != 0) {
+ /* Hit; see if values match */
+ if ((*ht->valueCompare)(he->value, value)) {
+ /* key,value pair is already present in table */
+ return he;
+ }
+ if (he->value) {
+ (*ht->allocOps->freeEntry)(ht->allocPriv, he, HT_FREE_VALUE);
+ }
+ he->value = value;
+ return he;
+ }
+ return PL_HashTableRawAdd(ht, hep, keyHash, key, value);
+}
+
+PR_IMPLEMENT(void)
+PL_HashTableRawRemove(PLHashTable *ht, PLHashEntry **hep, PLHashEntry *he)
+{
+ PRUint32 i, n;
+ PLHashEntry *next, **oldbuckets;
+ PRSize nb;
+
+ *hep = he->next;
+ (*ht->allocOps->freeEntry)(ht->allocPriv, he, HT_FREE_ENTRY);
+
+ /* Shrink table if it's underloaded */
+ n = NBUCKETS(ht);
+ if (--ht->nentries < UNDERLOADED(n)) {
+ oldbuckets = ht->buckets;
+ nb = n * sizeof(PLHashEntry*) / 2;
+ ht->buckets = (PLHashEntry**)(
+ (*ht->allocOps->allocTable)(ht->allocPriv, nb));
+ if (!ht->buckets) {
+ ht->buckets = oldbuckets;
+ return;
+ }
+ memset(ht->buckets, 0, nb);
+#ifdef HASHMETER
+ ht->nshrinks++;
+#endif
+ ht->shift++;
+
+ for (i = 0; i < n; i++) {
+ for (he = oldbuckets[i]; he; he = next) {
+ next = he->next;
+ hep = PL_HashTableRawLookup(ht, he->keyHash, he->key);
+ PR_ASSERT(*hep == 0);
+ he->next = 0;
+ *hep = he;
+ }
+ }
+#ifdef DEBUG
+ memset(oldbuckets, 0xDB, n * sizeof oldbuckets[0]);
+#endif
+ (*ht->allocOps->freeTable)(ht->allocPriv, oldbuckets);
+ }
+}
+
+PR_IMPLEMENT(PRBool)
+PL_HashTableRemove(PLHashTable *ht, const void *key)
+{
+ PLHashNumber keyHash;
+ PLHashEntry *he, **hep;
+
+ keyHash = (*ht->keyHash)(key);
+ hep = PL_HashTableRawLookup(ht, keyHash, key);
+ if ((he = *hep) == 0) {
+ return PR_FALSE;
+ }
+
+ /* Hit; remove element */
+ PL_HashTableRawRemove(ht, hep, he);
+ return PR_TRUE;
+}
+
+PR_IMPLEMENT(void *)
+PL_HashTableLookup(PLHashTable *ht, const void *key)
+{
+ PLHashNumber keyHash;
+ PLHashEntry *he, **hep;
+
+ keyHash = (*ht->keyHash)(key);
+ hep = PL_HashTableRawLookup(ht, keyHash, key);
+ if ((he = *hep) != 0) {
+ return he->value;
+ }
+ return 0;
+}
+
+/*
+** Same as PL_HashTableLookup but doesn't reorder the hash entries.
+*/
+PR_IMPLEMENT(void *)
+PL_HashTableLookupConst(PLHashTable *ht, const void *key)
+{
+ PLHashNumber keyHash;
+ PLHashEntry *he, **hep;
+
+ keyHash = (*ht->keyHash)(key);
+ hep = PL_HashTableRawLookupConst(ht, keyHash, key);
+ if ((he = *hep) != 0) {
+ return he->value;
+ }
+ return 0;
+}
+
+/*
+** Iterate over the entries in the hash table calling func for each
+** entry found. Stop if "f" says to (return value & PR_ENUMERATE_STOP).
+** Return a count of the number of elements scanned.
+*/
+PR_IMPLEMENT(int)
+PL_HashTableEnumerateEntries(PLHashTable *ht, PLHashEnumerator f, void *arg)
+{
+ PLHashEntry *he, **hep;
+ PRUint32 i, nbuckets;
+ int rv, n = 0;
+ PLHashEntry *todo = 0;
+
+ nbuckets = NBUCKETS(ht);
+ for (i = 0; i < nbuckets; i++) {
+ hep = &ht->buckets[i];
+ while ((he = *hep) != 0) {
+ rv = (*f)(he, n, arg);
+ n++;
+ if (rv & (HT_ENUMERATE_REMOVE | HT_ENUMERATE_UNHASH)) {
+ *hep = he->next;
+ if (rv & HT_ENUMERATE_REMOVE) {
+ he->next = todo;
+ todo = he;
+ }
+ } else {
+ hep = &he->next;
+ }
+ if (rv & HT_ENUMERATE_STOP) {
+ goto out;
+ }
+ }
+ }
+
+out:
+ hep = &todo;
+ while ((he = *hep) != 0) {
+ PL_HashTableRawRemove(ht, hep, he);
+ }
+ return n;
+}
+
+#ifdef HASHMETER
+#include <math.h>
+#include <stdio.h>
+
+PR_IMPLEMENT(void)
+PL_HashTableDumpMeter(PLHashTable *ht, PLHashEnumerator dump, FILE *fp)
+{
+ double mean, variance;
+ PRUint32 nchains, nbuckets;
+ PRUint32 i, n, maxChain, maxChainLen;
+ PLHashEntry *he;
+
+ variance = 0;
+ nchains = 0;
+ maxChainLen = 0;
+ nbuckets = NBUCKETS(ht);
+ for (i = 0; i < nbuckets; i++) {
+ he = ht->buckets[i];
+ if (!he) {
+ continue;
+ }
+ nchains++;
+ for (n = 0; he; he = he->next) {
+ n++;
+ }
+ variance += n * n;
+ if (n > maxChainLen) {
+ maxChainLen = n;
+ maxChain = i;
+ }
+ }
+ mean = (double)ht->nentries / nchains;
+ variance = fabs(variance / nchains - mean * mean);
+
+ fprintf(fp, "\nHash table statistics:\n");
+ fprintf(fp, " number of lookups: %u\n", ht->nlookups);
+ fprintf(fp, " number of entries: %u\n", ht->nentries);
+ fprintf(fp, " number of grows: %u\n", ht->ngrows);
+ fprintf(fp, " number of shrinks: %u\n", ht->nshrinks);
+ fprintf(fp, " mean steps per hash: %g\n", (double)ht->nsteps
+ / ht->nlookups);
+ fprintf(fp, "mean hash chain length: %g\n", mean);
+ fprintf(fp, " standard deviation: %g\n", sqrt(variance));
+ fprintf(fp, " max hash chain length: %u\n", maxChainLen);
+ fprintf(fp, " max hash chain: [%u]\n", maxChain);
+
+ for (he = ht->buckets[maxChain], i = 0; he; he = he->next, i++)
+ if ((*dump)(he, i, fp) != HT_ENUMERATE_NEXT) {
+ break;
+ }
+}
+#endif /* HASHMETER */
+
+PR_IMPLEMENT(int)
+PL_HashTableDump(PLHashTable *ht, PLHashEnumerator dump, FILE *fp)
+{
+ int count;
+
+ count = PL_HashTableEnumerateEntries(ht, dump, fp);
+#ifdef HASHMETER
+ PL_HashTableDumpMeter(ht, dump, fp);
+#endif
+ return count;
+}
+
+PR_IMPLEMENT(PLHashNumber)
+PL_HashString(const void *key)
+{
+ PLHashNumber h;
+ const PRUint8 *s;
+
+ h = 0;
+ for (s = (const PRUint8*)key; *s; s++) {
+ h = PR_ROTATE_LEFT32(h, 4) ^ *s;
+ }
+ return h;
+}
+
+PR_IMPLEMENT(int)
+PL_CompareStrings(const void *v1, const void *v2)
+{
+ return strcmp((const char*)v1, (const char*)v2) == 0;
+}
+
+PR_IMPLEMENT(int)
+PL_CompareValues(const void *v1, const void *v2)
+{
+ return v1 == v2;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-29 11:48:33 +0000