284 lines
6.9 KiB
C
284 lines
6.9 KiB
C
/* $NetBSD: hash.c,v 1.3 1996/03/17 13:18:20 cgd Exp $ */
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/*
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* Copyright (c) 1992, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This software was developed by the Computer Systems Engineering group
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* at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
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* contributed to Berkeley.
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*
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* 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, Lawrence Berkeley Laboratories.
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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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* from: @(#)hash.c 8.1 (Berkeley) 6/6/93
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*/
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#include <sys/param.h>
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#include <stdlib.h>
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#include <string.h>
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#include "config.h"
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/*
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* Interned strings are kept in a hash table. By making each string
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* unique, the program can compare strings by comparing pointers.
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*/
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struct hashent {
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struct hashent *h_next; /* hash buckets are chained */
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const char *h_name; /* the string */
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u_int h_hash; /* its hash value */
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void *h_value; /* other values (for name=value) */
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};
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struct hashtab {
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size_t ht_size; /* size (power of 2) */
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u_int ht_mask; /* == ht_size - 1 */
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u_int ht_used; /* number of entries used */
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u_int ht_lim; /* when to expand */
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struct hashent **ht_tab; /* base of table */
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};
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static struct hashtab strings;
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/*
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* HASHFRACTION controls ht_lim, which in turn controls the average chain
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* length. We allow a few entries, on average, as comparing them is usually
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* cheap (the h_hash values prevent a strcmp).
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*/
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#define HASHFRACTION(sz) ((sz) * 3 / 2)
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/* round up to next multiple of y, where y is a power of 2 */
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#define ROUND(x, y) (((x) + (y) - 1) & ~((y) - 1))
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/*
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* Allocate space that will never be freed.
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*/
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static void *
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poolalloc(size)
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size_t size;
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{
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register char *p;
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register size_t alloc;
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static char *pool;
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static size_t nleft;
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if (nleft < size) {
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/*
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* Compute a `good' size to allocate via malloc.
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* 16384 is a guess at a good page size for malloc;
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* 32 is a guess at malloc's overhead.
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*/
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alloc = ROUND(size + 32, 16384) - 32;
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p = emalloc(alloc);
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nleft = alloc - size;
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} else {
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p = pool;
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nleft -= size;
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}
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pool = p + size;
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return (p);
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}
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/*
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* Initialize a new hash table. The size must be a power of 2.
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*/
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static void
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ht_init(ht, sz)
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register struct hashtab *ht;
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size_t sz;
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{
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register struct hashent **h;
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register u_int n;
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h = emalloc(sz * sizeof *h);
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ht->ht_tab = h;
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ht->ht_size = sz;
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ht->ht_mask = sz - 1;
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for (n = 0; n < sz; n++)
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*h++ = NULL;
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ht->ht_used = 0;
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ht->ht_lim = HASHFRACTION(sz);
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}
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/*
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* Expand an existing hash table.
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*/
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static void
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ht_expand(ht)
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register struct hashtab *ht;
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{
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register struct hashent *p, **h, **oldh, *q;
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register u_int n, i;
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n = ht->ht_size * 2;
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h = emalloc(n * sizeof *h);
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for (i = 0; i < n; i++)
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h[i] = NULL;
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oldh = ht->ht_tab;
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n--;
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for (i = ht->ht_size; i != 0; i--) {
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for (p = *oldh++; p != NULL; p = q) {
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q = p->h_next;
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p->h_next = h[p->h_hash & n];
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h[p->h_hash & n] = p;
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}
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}
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free(ht->ht_tab);
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ht->ht_tab = h;
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ht->ht_mask = n;
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ht->ht_size = ++n;
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ht->ht_lim = HASHFRACTION(n);
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}
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/*
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* Make a new hash entry, setting its h_next to NULL.
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*/
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static inline struct hashent *
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newhashent(name, h)
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const char *name;
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u_int h;
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{
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register struct hashent *hp;
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register char *m;
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m = poolalloc(sizeof(*hp) + ALIGNBYTES);
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hp = (struct hashent *)ALIGN(m);
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hp->h_name = name;
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hp->h_hash = h;
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hp->h_next = NULL;
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return (hp);
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}
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/*
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* Hash a string.
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*/
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static inline u_int
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hash(str)
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register const char *str;
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{
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register u_int h;
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for (h = 0; *str;)
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h = (h << 5) + h + *str++;
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return (h);
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}
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void
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initintern()
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{
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ht_init(&strings, 128);
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}
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/*
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* Generate a single unique copy of the given string. We expect this
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* function to be used frequently, so it should be fast.
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*/
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const char *
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intern(s)
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register const char *s;
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{
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register struct hashtab *ht;
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register struct hashent *hp, **hpp;
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register u_int h;
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register char *p;
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register size_t l;
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ht = &strings;
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h = hash(s);
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hpp = &ht->ht_tab[h & ht->ht_mask];
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for (; (hp = *hpp) != NULL; hpp = &hp->h_next)
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if (hp->h_hash == h && strcmp(hp->h_name, s) == 0)
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return (hp->h_name);
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l = strlen(s) + 1;
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p = poolalloc(l);
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bcopy(s, p, l);
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*hpp = newhashent(p, h);
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if (++ht->ht_used > ht->ht_lim)
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ht_expand(ht);
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return (p);
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}
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struct hashtab *
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ht_new()
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{
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register struct hashtab *ht;
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ht = emalloc(sizeof *ht);
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ht_init(ht, 8);
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return (ht);
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}
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/*
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* Insert and/or replace.
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*/
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int
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ht_insrep(ht, nam, val, replace)
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register struct hashtab *ht;
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register const char *nam;
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void *val;
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int replace;
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{
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register struct hashent *hp, **hpp;
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register u_int h;
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h = hash(nam);
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hpp = &ht->ht_tab[h & ht->ht_mask];
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for (; (hp = *hpp) != NULL; hpp = &hp->h_next) {
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if (hp->h_name == nam) {
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if (replace)
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hp->h_value = val;
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return (1);
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}
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}
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*hpp = hp = newhashent(nam, h);
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hp->h_value = val;
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if (++ht->ht_used > ht->ht_lim)
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ht_expand(ht);
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return (0);
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}
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void *
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ht_lookup(ht, nam)
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register struct hashtab *ht;
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register const char *nam;
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{
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register struct hashent *hp, **hpp;
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register u_int h;
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h = hash(nam);
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hpp = &ht->ht_tab[h & ht->ht_mask];
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for (; (hp = *hpp) != NULL; hpp = &hp->h_next)
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if (hp->h_name == nam)
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return (hp->h_value);
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return (NULL);
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}
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