/* $NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $ */ /*- * SPDX-License-Identifier: BSD-4-Clause * * Copyright (c) 1988, 1989, 1990 The Regents of the University of California. * Copyright (c) 1988, 1989 by Adam de Boor * Copyright (c) 1989 by Berkeley Softworks * All rights reserved. * * This code is derived from software contributed to Berkeley by * Adam de Boor. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #include <sys/types.h> #include <stdlib.h> #include <string.h> #include <unistd.h> /* hash.c -- * * This module contains routines to manipulate a hash table. * See hash.h for a definition of the structure of the hash * table. Hash tables grow automatically as the amount of * information increases. */ #include "sprite.h" #ifndef ORDER #include "make.h" #endif /* ORDER */ #include "hash.h" #include "ealloc.h" /* * Forward references to local procedures that are used before they're * defined: */ static void RebuildTable(Hash_Table *); /* * The following defines the ratio of # entries to # buckets * at which we rebuild the table to make it larger. */ #define rebuildLimit 8 /* *--------------------------------------------------------- * * Hash_InitTable -- * * This routine just sets up the hash table. * * Results: * None. * * Side Effects: * Memory is allocated for the initial bucket area. * *--------------------------------------------------------- */ void Hash_InitTable( register Hash_Table *t, /* Structure to use to hold table. */ int numBuckets) /* How many buckets to create for starters. * This number is rounded up to a power of * two. If <= 0, a reasonable default is * chosen. The table will grow in size later * as needed. */ { register int i; register struct Hash_Entry **hp; /* * Round up the size to a power of two. */ if (numBuckets <= 0) i = 16; else { for (i = 2; i < numBuckets; i <<= 1) continue; } t->numEntries = 0; t->size = i; t->mask = i - 1; t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i); while (--i >= 0) *hp++ = NULL; } /* *--------------------------------------------------------- * * Hash_DeleteTable -- * * This routine removes everything from a hash table * and frees up the memory space it occupied (except for * the space in the Hash_Table structure). * * Results: * None. * * Side Effects: * Lots of memory is freed up. * *--------------------------------------------------------- */ void Hash_DeleteTable(Hash_Table *t) { register struct Hash_Entry **hp, *h, *nexth = NULL; register int i; for (hp = t->bucketPtr, i = t->size; --i >= 0;) { for (h = *hp++; h != NULL; h = nexth) { nexth = h->next; free((char *)h); } } free((char *)t->bucketPtr); /* * Set up the hash table to cause memory faults on any future access * attempts until re-initialization. */ t->bucketPtr = NULL; } /* *--------------------------------------------------------- * * Hash_FindEntry -- * * Searches a hash table for an entry corresponding to key. * * Results: * The return value is a pointer to the entry for key, * if key was present in the table. If key was not * present, NULL is returned. * * Side Effects: * None. * *--------------------------------------------------------- */ Hash_Entry * Hash_FindEntry( Hash_Table *t, /* Hash table to search. */ char *key) /* A hash key. */ { register Hash_Entry *e; register unsigned h; register char *p; for (h = 0, p = key; *p;) h = (h << 5) - h + *p++; p = key; for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) if (e->namehash == h && strcmp(e->name, p) == 0) return (e); return (NULL); } /* *--------------------------------------------------------- * * Hash_CreateEntry -- * * Searches a hash table for an entry corresponding to * key. If no entry is found, then one is created. * * Results: * The return value is a pointer to the entry. If *newPtr * isn't NULL, then *newPtr is filled in with TRUE if a * new entry was created, and FALSE if an entry already existed * with the given key. * * Side Effects: * Memory may be allocated, and the hash buckets may be modified. *--------------------------------------------------------- */ Hash_Entry * Hash_CreateEntry( register Hash_Table *t, /* Hash table to search. */ char *key, /* A hash key. */ Boolean *newPtr) /* Filled in with TRUE if new entry created, * FALSE otherwise. */ { register Hash_Entry *e; register unsigned h; register char *p; int keylen; struct Hash_Entry **hp; /* * Hash the key. As a side effect, save the length (strlen) of the * key in case we need to create the entry. */ for (h = 0, p = key; *p;) h = (h << 5) - h + *p++; keylen = p - key; p = key; for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) { if (e->namehash == h && strcmp(e->name, p) == 0) { if (newPtr != NULL) *newPtr = FALSE; return (e); } } /* * The desired entry isn't there. Before allocating a new entry, * expand the table if necessary (and this changes the resulting * bucket chain). */ if (t->numEntries >= rebuildLimit * t->size) RebuildTable(t); e = (Hash_Entry *) emalloc(sizeof(*e) + keylen); hp = &t->bucketPtr[h & t->mask]; e->next = *hp; *hp = e; e->clientData = NULL; e->namehash = h; (void) strcpy(e->name, p); t->numEntries++; if (newPtr != NULL) *newPtr = TRUE; return (e); } /* *--------------------------------------------------------- * * Hash_DeleteEntry -- * * Delete the given hash table entry and free memory associated with * it. * * Results: * None. * * Side Effects: * Hash chain that entry lives in is modified and memory is freed. * *--------------------------------------------------------- */ void Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e) { register Hash_Entry **hp, *p; if (e == NULL) return; for (hp = &t->bucketPtr[e->namehash & t->mask]; (p = *hp) != NULL; hp = &p->next) { if (p == e) { *hp = p->next; free((char *)p); t->numEntries--; return; } } (void)write(2, "bad call to Hash_DeleteEntry\n", 29); abort(); } /* *--------------------------------------------------------- * * Hash_EnumFirst -- * This procedure sets things up for a complete search * of all entries recorded in the hash table. * * Results: * The return value is the address of the first entry in * the hash table, or NULL if the table is empty. * * Side Effects: * The information in searchPtr is initialized so that successive * calls to Hash_Next will return successive HashEntry's * from the table. * *--------------------------------------------------------- */ Hash_Entry * Hash_EnumFirst( Hash_Table *t, /* Table to be searched. */ register Hash_Search *searchPtr)/* Area in which to keep state * about search.*/ { searchPtr->tablePtr = t; searchPtr->nextIndex = 0; searchPtr->hashEntryPtr = NULL; return Hash_EnumNext(searchPtr); } /* *--------------------------------------------------------- * * Hash_EnumNext -- * This procedure returns successive entries in the hash table. * * Results: * The return value is a pointer to the next HashEntry * in the table, or NULL when the end of the table is * reached. * * Side Effects: * The information in searchPtr is modified to advance to the * next entry. * *--------------------------------------------------------- */ Hash_Entry * Hash_EnumNext( register Hash_Search *searchPtr) /* Area used to keep state about search. */ { register Hash_Entry *e; Hash_Table *t = searchPtr->tablePtr; /* * The hashEntryPtr field points to the most recently returned * entry, or is nil if we are starting up. If not nil, we have * to start at the next one in the chain. */ e = searchPtr->hashEntryPtr; if (e != NULL) e = e->next; /* * If the chain ran out, or if we are starting up, we need to * find the next nonempty chain. */ while (e == NULL) { if (searchPtr->nextIndex >= t->size) return (NULL); e = t->bucketPtr[searchPtr->nextIndex++]; } searchPtr->hashEntryPtr = e; return (e); } /* *--------------------------------------------------------- * * RebuildTable -- * This local routine makes a new hash table that * is larger than the old one. * * Results: * None. * * Side Effects: * The entire hash table is moved, so any bucket numbers * from the old table are invalid. * *--------------------------------------------------------- */ static void RebuildTable(register Hash_Table *t) { register Hash_Entry *e, *next = NULL, **hp, **xp; register int i, mask; register Hash_Entry **oldhp; int oldsize; oldhp = t->bucketPtr; oldsize = i = t->size; i <<= 1; t->size = i; t->mask = mask = i - 1; t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i); while (--i >= 0) *hp++ = NULL; for (hp = oldhp, i = oldsize; --i >= 0;) { for (e = *hp++; e != NULL; e = next) { next = e->next; xp = &t->bucketPtr[e->namehash & mask]; e->next = *xp; *xp = e; } } free((char *)oldhp); }
