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gecko-dev/js/ref/liveconnect/jsj_hash.c

473 строки
12 KiB
C
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/* -*- Mode: C; tab-width: 8 -*-
* Copyright (C) 1998 Netscape Communications Corporation, All Rights Reserved.
*/
/*
* This is a copy of the NSPR hash-table library, but it has been slightly
* modified to allow an additional argument to be passed into the hash
* key-comparision function. This is used to maintain thread-safety by
* passing in a JNIEnv pointer to the key-comparison function rather
* than storing it in a global. All types,function names, etc. have
* been renamed from their original NSPR names to protect the innocent.
*/
#include <stdlib.h>
#include <string.h>
#include "jsj_hash.h"
#include "prtypes.h"
#ifdef NSPR20
# include "prlog.h"
# include "prbit.h"
#else
# include "prassert.h"
#endif
/* Compute the number of buckets in ht */
#define NBUCKETS(ht) (1 << (JSJ_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 *
DefaultAllocTable(void *pool, size_t size)
{
#if defined(XP_MAC)
#pragma unused (pool)
#endif
return malloc(size);
}
static void
DefaultFreeTable(void *pool, void *item)
{
#if defined(XP_MAC)
#pragma unused (pool)
#endif
free(item);
}
static JSJHashEntry *
DefaultAllocEntry(void *pool, const void *key)
{
#if defined(XP_MAC)
#pragma unused (pool,key)
#endif
return malloc(sizeof(JSJHashEntry));
}
static void
DefaultFreeEntry(void *pool, JSJHashEntry *he, PRUintn flag)
{
#if defined(XP_MAC)
#pragma unused (pool)
#endif
if (flag == HT_FREE_ENTRY)
free(he);
}
static JSJHashAllocOps defaultHashAllocOps = {
DefaultAllocTable, DefaultFreeTable,
DefaultAllocEntry, DefaultFreeEntry
};
PR_IMPLEMENT(JSJHashTable *)
JSJ_NewHashTable(PRUint32 n, JSJHashFunction keyHash,
JSJHashComparator keyCompare, JSJHashComparator valueCompare,
JSJHashAllocOps *allocOps, void *allocPriv)
{
JSJHashTable *ht;
PRUint32 nb;
if (n <= MINBUCKETS) {
n = MINBUCKETSLOG2;
} else {
n = PR_CeilingLog2(n);
if ((PRInt32)n < 0)
return 0;
}
if (!allocOps) allocOps = &defaultHashAllocOps;
ht = (*allocOps->allocTable)(allocPriv, sizeof *ht);
if (!ht)
return 0;
memset(ht, 0, sizeof *ht);
ht->shift = JSJ_HASH_BITS - n;
n = 1 << n;
#if defined(XP_PC) && !defined(_WIN32)
if (n > 16000) {
(*allocOps->freeTable)(allocPriv, ht);
return 0;
}
#endif /* WIN16 */
nb = n * sizeof(JSJHashEntry *);
ht->buckets = (*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)
JSJ_HashTableDestroy(JSJHashTable *ht)
{
PRUint32 i, n;
JSJHashEntry *he, *next;
JSJHashAllocOps *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
PR_IMPLEMENT(JSJHashEntry **)
JSJ_HashTableRawLookup(JSJHashTable *ht, JSJHashNumber keyHash, const void *key, void *arg)
{
JSJHashEntry *he, **hep, **hep0;
JSJHashNumber 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, arg)) {
/* 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;
}
PR_IMPLEMENT(JSJHashEntry *)
JSJ_HashTableRawAdd(JSJHashTable *ht, JSJHashEntry **hep,
JSJHashNumber keyHash, const void *key, void *value,
void *arg)
{
PRUint32 i, n;
JSJHashEntry *he, *next, **oldbuckets;
PRUint32 nb;
/* Grow the table if it is overloaded */
n = NBUCKETS(ht);
if (ht->nentries >= OVERLOADED(n)) {
#ifdef HASHMETER
ht->ngrows++;
#endif
ht->shift--;
oldbuckets = ht->buckets;
#if defined(XP_PC) && !defined(_WIN32)
if (2 * n > 16000)
return 0;
#endif /* WIN16 */
nb = 2 * n * sizeof(JSJHashEntry *);
ht->buckets = (*ht->allocOps->allocTable)(ht->allocPriv, nb);
if (!ht->buckets) {
ht->buckets = oldbuckets;
return 0;
}
memset(ht->buckets, 0, nb);
for (i = 0; i < n; i++) {
for (he = oldbuckets[i]; he; he = next) {
next = he->next;
hep = JSJ_HashTableRawLookup(ht, he->keyHash, he->key, arg);
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 = JSJ_HashTableRawLookup(ht, keyHash, key, arg);
}
/* 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(JSJHashEntry *)
JSJ_HashTableAdd(JSJHashTable *ht, const void *key, void *value, void *arg)
{
JSJHashNumber keyHash;
JSJHashEntry *he, **hep;
keyHash = (*ht->keyHash)(key, arg);
hep = JSJ_HashTableRawLookup(ht, keyHash, key, arg);
if ((he = *hep) != 0) {
/* Hit; see if values match */
if ((*ht->valueCompare)(he->value, value, arg)) {
/* 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 JSJ_HashTableRawAdd(ht, hep, keyHash, key, value, arg);
}
PR_IMPLEMENT(void)
JSJ_HashTableRawRemove(JSJHashTable *ht, JSJHashEntry **hep, JSJHashEntry *he, void *arg)
{
PRUint32 i, n;
JSJHashEntry *next, **oldbuckets;
PRUint32 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)) {
#ifdef HASHMETER
ht->nshrinks++;
#endif
ht->shift++;
oldbuckets = ht->buckets;
nb = n * sizeof(JSJHashEntry*) / 2;
ht->buckets = (*ht->allocOps->allocTable)(ht->allocPriv, nb);
if (!ht->buckets) {
ht->buckets = oldbuckets;
return;
}
memset(ht->buckets, 0, nb);
for (i = 0; i < n; i++) {
for (he = oldbuckets[i]; he; he = next) {
next = he->next;
hep = JSJ_HashTableRawLookup(ht, he->keyHash, he->key, arg);
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)
JSJ_HashTableRemove(JSJHashTable *ht, const void *key, void *arg)
{
JSJHashNumber keyHash;
JSJHashEntry *he, **hep;
keyHash = (*ht->keyHash)(key, arg);
hep = JSJ_HashTableRawLookup(ht, keyHash, key, arg);
if ((he = *hep) == 0)
return PR_FALSE;
/* Hit; remove element */
JSJ_HashTableRawRemove(ht, hep, he, arg);
return PR_TRUE;
}
PR_IMPLEMENT(void *)
JSJ_HashTableLookup(JSJHashTable *ht, const void *key, void *arg)
{
JSJHashNumber keyHash;
JSJHashEntry *he, **hep;
keyHash = (*ht->keyHash)(key, arg);
hep = JSJ_HashTableRawLookup(ht, keyHash, key, arg);
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)
JSJ_HashTableEnumerateEntries(JSJHashTable *ht, JSJHashEnumerator f, void *arg)
{
JSJHashEntry *he, **hep;
PRUint32 i, nbuckets;
int rv, n = 0;
JSJHashEntry *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) {
JSJ_HashTableRawRemove(ht, hep, he, arg);
}
return n;
}
#ifdef HASHMETER
#include <math.h>
#include <stdio.h>
PR_IMPLEMENT(void)
JSJ_HashTableDumpMeter(JSJHashTable *ht, JSJHashEnumerator dump, FILE *fp)
{
double mean, variance;
PRUint32 nchains, nbuckets;
PRUint32 i, n, maxChain, maxChainLen;
JSJHashEntry *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)
JSJ_HashTableDump(JSJHashTable *ht, JSJHashEnumerator dump, FILE *fp)
{
int count;
count = JSJ_HashTableEnumerateEntries(ht, dump, fp);
#ifdef HASHMETER
JSJ_HashTableDumpMeter(ht, dump, fp);
#endif
return count;
}
PR_IMPLEMENT(JSJHashNumber)
JSJ_HashString(const void *key)
{
JSJHashNumber h;
const unsigned char *s;
h = 0;
for (s = key; *s; s++)
h = (h >> 28) ^ (h << 4) ^ *s;
return h;
}
PR_IMPLEMENT(int)
JSJ_CompareStrings(const void *v1, const void *v2)
{
return strcmp(v1, v2) == 0;
}
PR_IMPLEMENT(int)
JSJ_CompareValues(const void *v1, const void *v2)
{
return v1 == v2;
}
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