399 lines
9.8 KiB
C
399 lines
9.8 KiB
C
/*-
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* Copyright (c) 1988, 1989, 1990, 1993
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* The Regents of the University of California. All rights reserved.
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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.c 8.1 (Berkeley) 6/6/93
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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/* hash.c --
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*
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* This module contains routines to manipulate a hash table.
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* See hash.h for a definition of the structure of the hash
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* table. Hash tables grow automatically as the amount of
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* information increases.
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*/
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "hash.h"
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#include "util.h"
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/*
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* Forward references to local procedures that are used before they're
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* defined:
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*/
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static void RebuildTable(Hash_Table *);
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/*
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* The following defines the ratio of # entries to # buckets
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* at which we rebuild the table to make it larger.
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*/
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#define rebuildLimit 8
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/*
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*---------------------------------------------------------
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*
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* Hash_InitTable --
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*
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* Set up the hash table t with a given number of buckets, or a
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* reasonable default if the number requested is less than or
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* equal to zero. Hash tables will grow in size as needed.
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*
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*
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* Results:
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* None.
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*
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* Side Effects:
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* Memory is allocated for the initial bucket area.
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*
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*---------------------------------------------------------
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*/
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void
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Hash_InitTable(Hash_Table *t, int numBuckets)
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{
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int i;
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struct Hash_Entry **hp;
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/*
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* Round up the size to a power of two.
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*/
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if (numBuckets <= 0)
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i = 16;
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else {
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for (i = 2; i < numBuckets; i <<= 1)
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continue;
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}
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t->numEntries = 0;
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t->size = i;
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t->mask = i - 1;
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t->bucketPtr = hp = emalloc(sizeof(*hp) * i);
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while (--i >= 0)
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*hp++ = NULL;
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}
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/*
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*---------------------------------------------------------
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*
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* Hash_DeleteTable --
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*
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* This routine removes everything from a hash table
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* and frees up the memory space it occupied (except for
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* the space in the Hash_Table structure).
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*
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* Results:
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* None.
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*
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* Side Effects:
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* Lots of memory is freed up.
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*
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*---------------------------------------------------------
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*/
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void
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Hash_DeleteTable(Hash_Table *t)
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{
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struct Hash_Entry **hp, *h, *nexth = NULL;
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int i;
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for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
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for (h = *hp++; h != NULL; h = nexth) {
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nexth = h->next;
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free(h);
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}
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}
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free(t->bucketPtr);
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/*
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* Set up the hash table to cause memory faults on any future access
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* attempts until re-initialization.
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*/
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t->bucketPtr = NULL;
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}
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/*
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*---------------------------------------------------------
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*
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* Hash_FindEntry --
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*
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* Searches a hash table for an entry corresponding to key.
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*
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* Results:
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* The return value is a pointer to the entry for key,
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* if key was present in the table. If key was not
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* present, NULL is returned.
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*
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* Side Effects:
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* None.
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*
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*---------------------------------------------------------
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*/
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Hash_Entry *
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Hash_FindEntry(const Hash_Table *t, const char *key)
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{
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Hash_Entry *e;
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unsigned h;
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const char *p;
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for (h = 0, p = key; *p;)
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h = (h << 5) - h + *p++;
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p = key;
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for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
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if (e->namehash == h && strcmp(e->name, p) == 0)
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return (e);
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return (NULL);
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}
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/*
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*---------------------------------------------------------
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*
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* Hash_CreateEntry --
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*
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* Searches a hash table for an entry corresponding to
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* key. If no entry is found, then one is created.
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*
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* Results:
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* The return value is a pointer to the entry. If *newPtr
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* isn't NULL, then *newPtr is filled in with TRUE if a
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* new entry was created, and FALSE if an entry already existed
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* with the given key.
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*
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* Side Effects:
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* Memory may be allocated, and the hash buckets may be modified.
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*---------------------------------------------------------
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*/
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Hash_Entry *
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Hash_CreateEntry(Hash_Table *t, const char *key, Boolean *newPtr)
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{
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Hash_Entry *e;
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unsigned int h;
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const char *p;
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int keylen;
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struct Hash_Entry **hp;
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/*
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* Hash the key. As a side effect, save the length (strlen) of the
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* key in case we need to create the entry.
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*/
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for (h = 0, p = key; *p;)
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h = (h << 5) - h + *p++;
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keylen = p - key;
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p = key;
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for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
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if (e->namehash == h && strcmp(e->name, p) == 0) {
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if (newPtr != NULL)
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*newPtr = FALSE;
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return (e);
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}
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}
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/*
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* The desired entry isn't there. Before allocating a new entry,
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* expand the table if necessary (and this changes the resulting
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* bucket chain).
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*/
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if (t->numEntries >= rebuildLimit * t->size)
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RebuildTable(t);
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e = emalloc(sizeof(*e) + keylen);
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hp = &t->bucketPtr[h & t->mask];
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e->next = *hp;
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*hp = e;
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e->clientData = NULL;
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e->namehash = h;
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strcpy(e->name, p);
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t->numEntries++;
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if (newPtr != NULL)
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*newPtr = TRUE;
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return (e);
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}
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/*
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*---------------------------------------------------------
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*
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* Hash_DeleteEntry --
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*
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* Delete the given hash table entry and free memory associated with
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* it.
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*
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* Results:
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* None.
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*
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* Side Effects:
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* Hash chain that entry lives in is modified and memory is freed.
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*
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*---------------------------------------------------------
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*/
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void
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Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e)
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{
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Hash_Entry **hp, *p;
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if (e == NULL)
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return;
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for (hp = &t->bucketPtr[e->namehash & t->mask];
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(p = *hp) != NULL; hp = &p->next) {
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if (p == e) {
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*hp = p->next;
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free(p);
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t->numEntries--;
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return;
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}
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}
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write(STDERR_FILENO, "bad call to Hash_DeleteEntry\n", 29);
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abort();
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}
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/*
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*---------------------------------------------------------
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*
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* Hash_EnumFirst --
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* This procedure sets things up for a complete search
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* of all entries recorded in the hash table.
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*
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* Results:
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* The return value is the address of the first entry in
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* the hash table, or NULL if the table is empty.
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*
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* Side Effects:
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* The information in searchPtr is initialized so that successive
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* calls to Hash_Next will return successive HashEntry's
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* from the table.
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*
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*---------------------------------------------------------
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*/
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Hash_Entry *
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Hash_EnumFirst(const Hash_Table *t, Hash_Search *searchPtr)
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{
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searchPtr->tablePtr = t;
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searchPtr->nextIndex = 0;
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searchPtr->hashEntryPtr = NULL;
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return (Hash_EnumNext(searchPtr));
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}
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/*
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*---------------------------------------------------------
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*
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* Hash_EnumNext --
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* This procedure returns successive entries in the hash table.
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*
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* Results:
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* The return value is a pointer to the next HashEntry
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* in the table, or NULL when the end of the table is
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* reached.
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*
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* Side Effects:
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* The information in searchPtr is modified to advance to the
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* next entry.
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*
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*---------------------------------------------------------
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*/
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Hash_Entry *
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Hash_EnumNext(Hash_Search *searchPtr)
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{
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Hash_Entry *e;
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const Hash_Table *t = searchPtr->tablePtr;
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/*
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* The hashEntryPtr field points to the most recently returned
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* entry, or is NULL if we are starting up. If not NULL, we have
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* to start at the next one in the chain.
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*/
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e = searchPtr->hashEntryPtr;
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if (e != NULL)
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e = e->next;
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/*
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* If the chain ran out, or if we are starting up, we need to
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* find the next nonempty chain.
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*/
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while (e == NULL) {
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if (searchPtr->nextIndex >= t->size)
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return (NULL);
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e = t->bucketPtr[searchPtr->nextIndex++];
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}
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searchPtr->hashEntryPtr = e;
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return (e);
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}
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/*
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*---------------------------------------------------------
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*
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* RebuildTable --
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* This local routine makes a new hash table that
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* is larger than the old one.
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*
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* Results:
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* None.
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*
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* Side Effects:
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* The entire hash table is moved, so any bucket numbers
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* from the old table are invalid.
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*
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*---------------------------------------------------------
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*/
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static void
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RebuildTable(Hash_Table *t)
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{
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Hash_Entry *e, *next = NULL, **hp, **xp;
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int i, mask;
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Hash_Entry **oldhp;
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int oldsize;
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oldhp = t->bucketPtr;
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oldsize = i = t->size;
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i <<= 1;
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t->size = i;
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t->mask = mask = i - 1;
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t->bucketPtr = hp = emalloc(sizeof(*hp) * i);
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while (--i >= 0)
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*hp++ = NULL;
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for (hp = oldhp, i = oldsize; --i >= 0;) {
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for (e = *hp++; e != NULL; e = next) {
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next = e->next;
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xp = &t->bucketPtr[e->namehash & mask];
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e->next = *xp;
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*xp = e;
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}
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}
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free(oldhp);
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}
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