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336 lines
9.5 KiB
C
336 lines
9.5 KiB
C
/* $NetBSD: hash.c,v 1.79 2024/07/07 09:37:00 rillig Exp $ */
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/*
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* Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
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* All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Adam de Boor.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* Copyright (c) 1988, 1989 by Adam de Boor
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* Copyright (c) 1989 by Berkeley Softworks
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* All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Adam de Boor.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/* Hash tables with string keys and pointer values. */
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#include "make.h"
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/* "@(#)hash.c 8.1 (Berkeley) 6/6/93" */
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MAKE_RCSID("$NetBSD: hash.c,v 1.79 2024/07/07 09:37:00 rillig Exp $");
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/*
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* The ratio of # entries to # buckets at which we rebuild the table to
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* make it larger.
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*/
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#define rebuildLimit 3
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/* This hash function matches Gosling's Emacs and java.lang.String. */
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static unsigned int
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Hash_String(const char *key, const char **out_keyEnd)
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{
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unsigned int h;
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const char *p;
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h = 0;
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for (p = key; *p != '\0'; p++)
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h = 31 * h + (unsigned char)*p;
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*out_keyEnd = p;
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return h;
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}
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/* This hash function matches Gosling's Emacs and java.lang.String. */
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unsigned int
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Hash_Substring(Substring key)
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{
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unsigned int h;
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const char *p;
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h = 0;
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for (p = key.start; p != key.end; p++)
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h = 31 * h + (unsigned char)*p;
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return h;
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}
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static HashEntry *
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HashTable_Find(HashTable *t, Substring key, unsigned int h)
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{
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HashEntry *he;
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size_t keyLen = Substring_Length(key);
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#ifdef DEBUG_HASH_LOOKUP
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DEBUG4(HASH, "HashTable_Find: %p h=%08x key=%.*s\n",
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t, h, (int)keyLen, key.start);
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#endif
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for (he = t->buckets[h & t->bucketsMask]; he != NULL; he = he->next) {
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if (he->hash == h &&
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strncmp(he->key, key.start, keyLen) == 0 &&
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he->key[keyLen] == '\0')
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break;
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}
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return he;
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}
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/* Set up the hash table. */
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void
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HashTable_Init(HashTable *t)
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{
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unsigned int n = 16, i;
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HashEntry **buckets = bmake_malloc(sizeof *buckets * n);
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for (i = 0; i < n; i++)
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buckets[i] = NULL;
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t->buckets = buckets;
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t->bucketsSize = n;
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t->numEntries = 0;
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t->bucketsMask = n - 1;
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}
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/*
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* Remove everything from the hash table and free up the memory for the keys
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* of the hash table, but not for the values associated to these keys.
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*/
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void
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HashTable_Done(HashTable *t)
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{
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HashEntry **buckets = t->buckets;
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size_t i, n = t->bucketsSize;
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for (i = 0; i < n; i++) {
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HashEntry *he = buckets[i];
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while (he != NULL) {
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HashEntry *next = he->next;
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free(he);
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he = next;
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}
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}
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free(t->buckets);
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#ifdef CLEANUP
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t->buckets = NULL;
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#endif
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}
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/* Find the entry corresponding to the key, or return NULL. */
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HashEntry *
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HashTable_FindEntry(HashTable *t, const char *key)
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{
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const char *keyEnd;
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unsigned int h = Hash_String(key, &keyEnd);
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return HashTable_Find(t, Substring_Init(key, keyEnd), h);
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}
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/* Find the value corresponding to the key, or return NULL. */
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void *
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HashTable_FindValue(HashTable *t, const char *key)
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{
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HashEntry *he = HashTable_FindEntry(t, key);
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return he != NULL ? he->value : NULL;
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}
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/*
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* Find the value corresponding to the key and the precomputed hash,
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* or return NULL.
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*/
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void *
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HashTable_FindValueBySubstringHash(HashTable *t, Substring key, unsigned int h)
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{
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HashEntry *he = HashTable_Find(t, key, h);
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return he != NULL ? he->value : NULL;
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}
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static unsigned
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HashTable_MaxChain(const HashTable *t)
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{
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unsigned b, cl, max_cl = 0;
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for (b = 0; b < t->bucketsSize; b++) {
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const HashEntry *he = t->buckets[b];
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for (cl = 0; he != NULL; he = he->next)
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cl++;
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if (cl > max_cl)
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max_cl = cl;
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}
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return max_cl;
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}
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/*
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* Make the hash table larger. Any bucket numbers from the old table become
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* invalid; the hash values stay valid though.
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*/
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static void
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HashTable_Enlarge(HashTable *t)
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{
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unsigned int oldSize = t->bucketsSize;
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HashEntry **oldBuckets = t->buckets;
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unsigned int newSize = 2 * oldSize;
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unsigned int newMask = newSize - 1;
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HashEntry **newBuckets = bmake_malloc(sizeof *newBuckets * newSize);
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size_t i;
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for (i = 0; i < newSize; i++)
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newBuckets[i] = NULL;
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for (i = 0; i < oldSize; i++) {
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HashEntry *he = oldBuckets[i];
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while (he != NULL) {
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HashEntry *next = he->next;
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he->next = newBuckets[he->hash & newMask];
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newBuckets[he->hash & newMask] = he;
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he = next;
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}
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}
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free(oldBuckets);
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t->bucketsSize = newSize;
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t->bucketsMask = newMask;
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t->buckets = newBuckets;
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DEBUG4(HASH, "HashTable_Enlarge: %p size=%d entries=%d maxchain=%d\n",
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(void *)t, t->bucketsSize, t->numEntries, HashTable_MaxChain(t));
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}
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/*
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* Find or create an entry corresponding to the key.
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* Return in out_isNew whether a new entry has been created.
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*/
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HashEntry *
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HashTable_CreateEntry(HashTable *t, const char *key, bool *out_isNew)
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{
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const char *keyEnd;
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unsigned int h = Hash_String(key, &keyEnd);
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HashEntry *he = HashTable_Find(t, Substring_Init(key, keyEnd), h);
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if (he != NULL) {
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if (out_isNew != NULL)
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*out_isNew = false;
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return he;
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}
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if (t->numEntries >= rebuildLimit * t->bucketsSize)
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HashTable_Enlarge(t);
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he = bmake_malloc(sizeof *he + (size_t)(keyEnd - key));
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he->value = NULL;
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he->hash = h;
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memcpy(he->key, key, (size_t)(keyEnd - key) + 1);
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he->next = t->buckets[h & t->bucketsMask];
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t->buckets[h & t->bucketsMask] = he;
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t->numEntries++;
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if (out_isNew != NULL)
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*out_isNew = true;
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return he;
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}
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void
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HashTable_Set(HashTable *t, const char *key, void *value)
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{
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HashEntry *he = HashTable_CreateEntry(t, key, NULL);
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HashEntry_Set(he, value);
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}
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/* Delete the entry from the table, don't free the value of the entry. */
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void
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HashTable_DeleteEntry(HashTable *t, HashEntry *he)
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{
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HashEntry **ref = &t->buckets[he->hash & t->bucketsMask];
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for (; *ref != he; ref = &(*ref)->next)
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continue;
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*ref = he->next;
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free(he);
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t->numEntries--;
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}
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/*
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* Place the next entry from the hash table in hi->entry, or return false if
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* the end of the table is reached.
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*/
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bool
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HashIter_Next(HashIter *hi)
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{
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HashTable *t = hi->table;
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HashEntry *he = hi->entry;
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HashEntry **buckets = t->buckets;
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unsigned int bucketsSize = t->bucketsSize;
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if (he != NULL)
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he = he->next; /* skip the most recently returned entry */
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while (he == NULL) { /* find the next nonempty chain */
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if (hi->nextBucket >= bucketsSize)
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return false;
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he = buckets[hi->nextBucket++];
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}
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hi->entry = he;
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return true;
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}
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void
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HashTable_DebugStats(const HashTable *t, const char *name)
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{
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DEBUG4(HASH, "HashTable \"%s\": size=%u entries=%u maxchain=%u\n",
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name, t->bucketsSize, t->numEntries, HashTable_MaxChain(t));
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}
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