mirror of
https://github.com/mozilla/gecko-dev.git
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451 lines
11 KiB
C++
451 lines
11 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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* vim: set ts=8 sts=4 et sw=4 tw=99:
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/*
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* PR hash table package.
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*/
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#include "jshash.h"
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#include "mozilla/MathAlgorithms.h"
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#include <stdlib.h>
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#include <string.h>
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#include "jstypes.h"
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#include "jsutil.h"
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using namespace js;
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using mozilla::CeilingLog2Size;
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/* Compute the number of buckets in ht */
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#define NBUCKETS(ht) JS_BIT(JS_HASH_BITS - (ht)->shift)
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/* The smallest table has 16 buckets */
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#define MINBUCKETSLOG2 4
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#define MINBUCKETS JS_BIT(MINBUCKETSLOG2)
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/* Compute the maximum entries given n buckets that we will tolerate, ~90% */
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#define OVERLOADED(n) ((n) - ((n) >> 3))
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/* Compute the number of entries below which we shrink the table by half */
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#define UNDERLOADED(n) (((n) > MINBUCKETS) ? ((n) >> 2) : 0)
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/*
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** Stubs for default hash allocator ops.
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*/
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static void *
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DefaultAllocTable(void *pool, size_t size)
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{
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return js_malloc(size);
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}
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static void
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DefaultFreeTable(void *pool, void *item, size_t size)
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{
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js_free(item);
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}
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static JSHashEntry *
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DefaultAllocEntry(void *pool, const void *key)
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{
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return (JSHashEntry*) js_malloc(sizeof(JSHashEntry));
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}
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static void
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DefaultFreeEntry(void *pool, JSHashEntry *he, unsigned flag)
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{
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if (flag == HT_FREE_ENTRY)
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js_free(he);
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}
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static JSHashAllocOps defaultHashAllocOps = {
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DefaultAllocTable, DefaultFreeTable,
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DefaultAllocEntry, DefaultFreeEntry
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};
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JSHashTable *
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JS_NewHashTable(uint32_t n, JSHashFunction keyHash,
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JSHashComparator keyCompare, JSHashComparator valueCompare,
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JSHashAllocOps *allocOps, void *allocPriv)
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{
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JSHashTable *ht;
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size_t nb;
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if (n <= MINBUCKETS) {
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n = MINBUCKETSLOG2;
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} else {
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n = CeilingLog2Size(n);
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if (int32_t(n) < 0)
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return NULL;
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}
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if (!allocOps) allocOps = &defaultHashAllocOps;
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ht = (JSHashTable*) allocOps->allocTable(allocPriv, sizeof *ht);
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if (!ht)
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return NULL;
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memset(ht, 0, sizeof *ht);
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ht->shift = JS_HASH_BITS - n;
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n = JS_BIT(n);
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nb = n * sizeof(JSHashEntry *);
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ht->buckets = (JSHashEntry**) allocOps->allocTable(allocPriv, nb);
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if (!ht->buckets) {
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allocOps->freeTable(allocPriv, ht, nb);
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return NULL;
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}
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memset(ht->buckets, 0, nb);
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ht->keyHash = keyHash;
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ht->keyCompare = keyCompare;
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ht->valueCompare = valueCompare;
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ht->allocOps = allocOps;
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ht->allocPriv = allocPriv;
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return ht;
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}
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void
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JS_HashTableDestroy(JSHashTable *ht)
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{
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uint32_t i, n;
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JSHashEntry *he, **hep;
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JSHashAllocOps *allocOps = ht->allocOps;
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void *allocPriv = ht->allocPriv;
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n = NBUCKETS(ht);
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for (i = 0; i < n; i++) {
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hep = &ht->buckets[i];
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while ((he = *hep) != NULL) {
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*hep = he->next;
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allocOps->freeEntry(allocPriv, he, HT_FREE_ENTRY);
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}
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}
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#ifdef DEBUG
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memset(ht->buckets, 0xDB, n * sizeof ht->buckets[0]);
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#endif
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allocOps->freeTable(allocPriv, ht->buckets, n * sizeof ht->buckets[0]);
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#ifdef DEBUG
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memset(ht, 0xDB, sizeof *ht);
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#endif
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allocOps->freeTable(allocPriv, ht, sizeof *ht);
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}
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/*
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* Multiplicative hash, from Knuth 6.4.
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*/
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#define BUCKET_HEAD(ht, keyHash) \
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(&(ht)->buckets[((keyHash) * JS_GOLDEN_RATIO) >> (ht)->shift])
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JSHashEntry **
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JS_HashTableRawLookup(JSHashTable *ht, JSHashNumber keyHash, const void *key)
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{
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JSHashEntry *he, **hep, **hep0;
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#ifdef JS_HASHMETER
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ht->nlookups++;
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#endif
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hep = hep0 = BUCKET_HEAD(ht, keyHash);
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while ((he = *hep) != NULL) {
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if (he->keyHash == keyHash && ht->keyCompare(key, he->key)) {
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/* Move to front of chain if not already there */
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if (hep != hep0) {
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*hep = he->next;
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he->next = *hep0;
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*hep0 = he;
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}
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return hep0;
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}
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hep = &he->next;
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#ifdef JS_HASHMETER
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ht->nsteps++;
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#endif
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}
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return hep;
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}
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static JSBool
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Resize(JSHashTable *ht, uint32_t newshift)
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{
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size_t nb, nentries, i;
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JSHashEntry **oldbuckets, *he, *next, **hep;
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size_t nold = NBUCKETS(ht);
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JS_ASSERT(newshift < JS_HASH_BITS);
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nb = (size_t)1 << (JS_HASH_BITS - newshift);
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/* Integer overflow protection. */
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if (nb > (size_t)-1 / sizeof(JSHashEntry*))
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return JS_FALSE;
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nb *= sizeof(JSHashEntry*);
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oldbuckets = ht->buckets;
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ht->buckets = (JSHashEntry**)ht->allocOps->allocTable(ht->allocPriv, nb);
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if (!ht->buckets) {
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ht->buckets = oldbuckets;
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return JS_FALSE;
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}
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memset(ht->buckets, 0, nb);
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ht->shift = newshift;
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nentries = ht->nentries;
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for (i = 0; nentries != 0; i++) {
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for (he = oldbuckets[i]; he; he = next) {
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JS_ASSERT(nentries != 0);
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--nentries;
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next = he->next;
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hep = BUCKET_HEAD(ht, he->keyHash);
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/*
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* We do not require unique entries, instead appending he to the
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* chain starting at hep.
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*/
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while (*hep)
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hep = &(*hep)->next;
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he->next = NULL;
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*hep = he;
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}
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}
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#ifdef DEBUG
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memset(oldbuckets, 0xDB, nold * sizeof oldbuckets[0]);
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#endif
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ht->allocOps->freeTable(ht->allocPriv, oldbuckets,
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nold * sizeof oldbuckets[0]);
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return JS_TRUE;
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}
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JSHashEntry *
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JS_HashTableRawAdd(JSHashTable *ht, JSHashEntry **&hep,
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JSHashNumber keyHash, const void *key, void *value)
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{
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uint32_t n;
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JSHashEntry *he;
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/* Grow the table if it is overloaded */
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n = NBUCKETS(ht);
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if (ht->nentries >= OVERLOADED(n)) {
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if (!Resize(ht, ht->shift - 1))
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return NULL;
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#ifdef JS_HASHMETER
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ht->ngrows++;
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#endif
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hep = JS_HashTableRawLookup(ht, keyHash, key);
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}
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/* Make a new key value entry */
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he = ht->allocOps->allocEntry(ht->allocPriv, key);
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if (!he)
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return NULL;
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he->keyHash = keyHash;
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he->key = key;
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he->value = value;
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he->next = *hep;
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*hep = he;
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ht->nentries++;
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return he;
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}
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JSHashEntry *
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JS_HashTableAdd(JSHashTable *ht, const void *key, void *value)
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{
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JSHashNumber keyHash;
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JSHashEntry *he, **hep;
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keyHash = ht->keyHash(key);
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hep = JS_HashTableRawLookup(ht, keyHash, key);
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if ((he = *hep) != NULL) {
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/* Hit; see if values match */
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if (ht->valueCompare(he->value, value)) {
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/* key,value pair is already present in table */
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return he;
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}
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if (he->value)
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ht->allocOps->freeEntry(ht->allocPriv, he, HT_FREE_VALUE);
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he->value = value;
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return he;
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}
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return JS_HashTableRawAdd(ht, hep, keyHash, key, value);
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}
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void
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JS_HashTableRawRemove(JSHashTable *ht, JSHashEntry **hep, JSHashEntry *he)
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{
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uint32_t n;
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*hep = he->next;
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ht->allocOps->freeEntry(ht->allocPriv, he, HT_FREE_ENTRY);
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/* Shrink table if it's underloaded */
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n = NBUCKETS(ht);
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if (--ht->nentries < UNDERLOADED(n)) {
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Resize(ht, ht->shift + 1);
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#ifdef JS_HASHMETER
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ht->nshrinks++;
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#endif
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}
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}
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JSBool
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JS_HashTableRemove(JSHashTable *ht, const void *key)
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{
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JSHashNumber keyHash;
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JSHashEntry *he, **hep;
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keyHash = ht->keyHash(key);
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hep = JS_HashTableRawLookup(ht, keyHash, key);
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if ((he = *hep) == NULL)
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return JS_FALSE;
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/* Hit; remove element */
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JS_HashTableRawRemove(ht, hep, he);
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return JS_TRUE;
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}
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void *
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JS_HashTableLookup(JSHashTable *ht, const void *key)
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{
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JSHashNumber keyHash;
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JSHashEntry *he, **hep;
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keyHash = ht->keyHash(key);
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hep = JS_HashTableRawLookup(ht, keyHash, key);
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if ((he = *hep) != NULL) {
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return he->value;
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}
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return NULL;
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}
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/*
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** Iterate over the entries in the hash table calling func for each
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** entry found. Stop if "f" says to (return value & JS_ENUMERATE_STOP).
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** Return a count of the number of elements scanned.
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*/
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int
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JS_HashTableEnumerateEntries(JSHashTable *ht, JSHashEnumerator f, void *arg)
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{
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JSHashEntry *he, **hep, **bucket;
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uint32_t nlimit, n, nbuckets, newlog2;
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int rv;
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nlimit = ht->nentries;
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n = 0;
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for (bucket = ht->buckets; n != nlimit; ++bucket) {
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hep = bucket;
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while ((he = *hep) != NULL) {
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JS_ASSERT(n < nlimit);
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rv = f(he, n, arg);
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n++;
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if (rv & HT_ENUMERATE_REMOVE) {
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*hep = he->next;
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ht->allocOps->freeEntry(ht->allocPriv, he, HT_FREE_ENTRY);
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--ht->nentries;
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} else {
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hep = &he->next;
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}
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if (rv & HT_ENUMERATE_STOP) {
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goto out;
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}
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}
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}
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out:
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/* Shrink table if removal of entries made it underloaded */
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if (ht->nentries != nlimit) {
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JS_ASSERT(ht->nentries < nlimit);
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nbuckets = NBUCKETS(ht);
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if (MINBUCKETS < nbuckets && ht->nentries < UNDERLOADED(nbuckets)) {
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newlog2 = CeilingLog2Size(ht->nentries);
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if (newlog2 < MINBUCKETSLOG2)
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newlog2 = MINBUCKETSLOG2;
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/* Check that we really shrink the table. */
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JS_ASSERT(JS_HASH_BITS - ht->shift > newlog2);
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Resize(ht, JS_HASH_BITS - newlog2);
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}
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}
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return (int)n;
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}
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#ifdef JS_HASHMETER
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#include <stdio.h>
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void
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JS_HashTableDumpMeter(JSHashTable *ht, JSHashEnumerator dump, FILE *fp)
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{
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double sqsum, mean, sigma;
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uint32_t nchains, nbuckets;
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uint32_t i, n, maxChain, maxChainLen;
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JSHashEntry *he;
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sqsum = 0;
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nchains = 0;
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maxChain = maxChainLen = 0;
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nbuckets = NBUCKETS(ht);
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for (i = 0; i < nbuckets; i++) {
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he = ht->buckets[i];
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if (!he)
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continue;
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nchains++;
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for (n = 0; he; he = he->next)
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n++;
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sqsum += n * n;
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if (n > maxChainLen) {
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maxChainLen = n;
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maxChain = i;
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}
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}
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mean = JS_MeanAndStdDev(nchains, ht->nentries, sqsum, &sigma);
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fprintf(fp, "\nHash table statistics:\n");
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fprintf(fp, " number of lookups: %u\n", ht->nlookups);
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fprintf(fp, " number of entries: %u\n", ht->nentries);
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fprintf(fp, " number of grows: %u\n", ht->ngrows);
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fprintf(fp, " number of shrinks: %u\n", ht->nshrinks);
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fprintf(fp, " mean steps per hash: %g\n", (double)ht->nsteps
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/ ht->nlookups);
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fprintf(fp, "mean hash chain length: %g\n", mean);
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fprintf(fp, " standard deviation: %g\n", sigma);
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fprintf(fp, " max hash chain length: %u\n", maxChainLen);
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fprintf(fp, " max hash chain: [%u]\n", maxChain);
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for (he = ht->buckets[maxChain], i = 0; he; he = he->next, i++)
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if (dump(he, i, fp) != HT_ENUMERATE_NEXT)
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break;
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}
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#endif /* JS_HASHMETER */
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int
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JS_HashTableDump(JSHashTable *ht, JSHashEnumerator dump, FILE *fp)
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{
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int count;
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count = JS_HashTableEnumerateEntries(ht, dump, fp);
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#ifdef JS_HASHMETER
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JS_HashTableDumpMeter(ht, dump, fp);
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#endif
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return count;
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}
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JSHashNumber
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JS_HashString(const void *key)
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{
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JSHashNumber h;
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const unsigned char *s;
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h = 0;
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for (s = (const unsigned char *)key; *s; s++)
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h = JS_ROTATE_LEFT32(h, 4) ^ *s;
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return h;
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}
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int
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JS_CompareValues(const void *v1, const void *v2)
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{
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return v1 == v2;
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}
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