4.4BSD/usr/src/usr.sbin/config.new/hash.c
/*
* Copyright (c) 1992, 1993
* The Regents of the University of California. All rights reserved.
*
* This software was developed by the Computer Systems Engineering group
* at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
* contributed to Berkeley.
*
* 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, Lawrence Berkeley Laboratories.
*
* 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.
*
* @(#)hash.c 8.1 (Berkeley) 6/6/93
*/
#include <sys/param.h>
#include <stdlib.h>
#include <string.h>
#include "config.h"
/*
* Interned strings are kept in a hash table. By making each string
* unique, the program can compare strings by comparing pointers.
*/
struct hashent {
struct hashent *h_next; /* hash buckets are chained */
const char *h_name; /* the string */
u_int h_hash; /* its hash value */
void *h_value; /* other values (for name=value) */
};
struct hashtab {
size_t ht_size; /* size (power of 2) */
u_int ht_mask; /* == ht_size - 1 */
u_int ht_used; /* number of entries used */
u_int ht_lim; /* when to expand */
struct hashent **ht_tab; /* base of table */
};
static struct hashtab strings;
/*
* HASHFRACTION controls ht_lim, which in turn controls the average chain
* length. We allow a few entries, on average, as comparing them is usually
* cheap (the h_hash values prevent a strcmp).
*/
#define HASHFRACTION(sz) ((sz) * 3 / 2)
/* round up to next multiple of y, where y is a power of 2 */
#define ROUND(x, y) (((x) + (y) - 1) & ~((y) - 1))
/*
* Allocate space that will never be freed.
*/
static void *
poolalloc(size)
size_t size;
{
register char *p;
register size_t alloc;
static char *pool;
static size_t nleft;
if (nleft < size) {
/*
* Compute a `good' size to allocate via malloc.
* 16384 is a guess at a good page size for malloc;
* 32 is a guess at malloc's overhead.
*/
alloc = ROUND(size + 32, 16384) - 32;
p = emalloc(alloc);
nleft = alloc - size;
} else {
p = pool;
nleft -= size;
}
pool = p + size;
return (p);
}
/*
* Initialize a new hash table. The size must be a power of 2.
*/
static void
ht_init(ht, sz)
register struct hashtab *ht;
size_t sz;
{
register struct hashent **h;
register u_int n;
h = emalloc(sz * sizeof *h);
ht->ht_tab = h;
ht->ht_size = sz;
ht->ht_mask = sz - 1;
for (n = 0; n < sz; n++)
*h++ = NULL;
ht->ht_used = 0;
ht->ht_lim = HASHFRACTION(sz);
}
/*
* Expand an existing hash table.
*/
static void
ht_expand(ht)
register struct hashtab *ht;
{
register struct hashent *p, **h, **oldh, *q;
register u_int n, i;
n = ht->ht_size * 2;
h = emalloc(n * sizeof *h);
for (i = 0; i < n; i++)
h[i] = NULL;
oldh = ht->ht_tab;
n--;
for (i = ht->ht_size; i != 0; i--) {
for (p = *oldh++; p != NULL; p = q) {
q = p->h_next;
p->h_next = h[p->h_hash & n];
h[p->h_hash & n] = p;
}
}
free(ht->ht_tab);
ht->ht_tab = h;
ht->ht_mask = n;
ht->ht_size = ++n;
ht->ht_lim = HASHFRACTION(n);
}
/*
* Make a new hash entry, setting its h_next to NULL.
*/
static inline struct hashent *
newhashent(name, h)
const char *name;
u_int h;
{
register struct hashent *hp;
register char *m;
m = poolalloc(sizeof(*hp) + ALIGNBYTES);
hp = (struct hashent *)ALIGN(m);
hp->h_name = name;
hp->h_hash = h;
hp->h_next = NULL;
return (hp);
}
/*
* Hash a string.
*/
static inline u_int
hash(str)
register const char *str;
{
register u_int h;
for (h = 0; *str;)
h = (h << 5) + h + *str++;
return (h);
}
void
initintern()
{
ht_init(&strings, 128);
}
/*
* Generate a single unique copy of the given string. We expect this
* function to be used frequently, so it should be fast.
*/
const char *
intern(s)
register const char *s;
{
register struct hashtab *ht;
register struct hashent *hp, **hpp;
register u_int h;
register char *p;
register size_t l;
ht = &strings;
h = hash(s);
hpp = &ht->ht_tab[h & ht->ht_mask];
for (; (hp = *hpp) != NULL; hpp = &hp->h_next)
if (hp->h_hash == h && strcmp(hp->h_name, s) == 0)
return (hp->h_name);
l = strlen(s) + 1;
p = poolalloc(l);
bcopy(s, p, l);
*hpp = newhashent(p, h);
if (++ht->ht_used > ht->ht_lim)
ht_expand(ht);
return (p);
}
struct hashtab *
ht_new()
{
register struct hashtab *ht;
ht = emalloc(sizeof *ht);
ht_init(ht, 8);
return (ht);
}
/*
* Insert and/or replace.
*/
int
ht_insrep(ht, nam, val, replace)
register struct hashtab *ht;
register const char *nam;
void *val;
int replace;
{
register struct hashent *hp, **hpp;
register u_int h;
h = hash(nam);
hpp = &ht->ht_tab[h & ht->ht_mask];
for (; (hp = *hpp) != NULL; hpp = &hp->h_next) {
if (hp->h_name == nam) {
if (replace)
hp->h_value = val;
return (1);
}
}
*hpp = hp = newhashent(nam, h);
hp->h_value = val;
return (0);
}
void *
ht_lookup(ht, nam)
register struct hashtab *ht;
register const char *nam;
{
register struct hashent *hp, **hpp;
register u_int h;
h = hash(nam);
hpp = &ht->ht_tab[h & ht->ht_mask];
for (; (hp = *hpp) != NULL; hpp = &hp->h_next)
if (hp->h_name == nam)
return (hp->h_value);
return (NULL);
}