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/*
* hashtable.c: in core hash table routines.
*
* Copyright (C) 1994, 1995 Graeme W. Wilford. (Wilf.)
* Copyright (C) 2002, 2003, 2004, 2005, 2007, 2008, 2009 Colin Watson.
*
* This file is part of man-db.
*
* man-db is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* man-db is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with man-db; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
* All of these routines except hash_free() can be found in K&R II.
*
* Sat Aug 20 15:01:02 BST 1994 Wilf. (G.Wilford@ee.surrey.ac.uk)
*/
/* which hash function do we want ? */
/* #define PROLOGUE */
#define KRII
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif /* HAVE_CONFIG_H */
#include <string.h>
#include <stdlib.h>
#include "manconfig.h"
#include "hashtable.h"
#if defined(PROLOGUE)
#define HASHSIZE 2048
#elif defined(KRII)
#define HASHSIZE 2001
#else
#error hash function not defined
#endif
/* Return hash value for string. */
static unsigned int hash (const char *s, size_t len)
{
unsigned int hashval = 0;
size_t i;
for (i = 0; i < len && s[i]; ++i)
#if defined(KRII)
hashval = s[i] + 31 * hashval;
return hashval % HASHSIZE;
#elif defined(PROLOGUE)
hashval = (hashval << 1) + s[i];
return hashval & (HASHSIZE - 1);
#endif
}
void null_hash_free (void *defn)
{
defn = defn; /* unused */
}
void plain_hash_free (void *defn)
{
if (defn)
free (defn);
}
/* Create a hashtable. */
struct hashtable *hash_create (hash_free_ptr free_defn)
{
struct hashtable *ht = XMALLOC (struct hashtable);
ht->hashtab = XCALLOC (HASHSIZE, struct nlist *);
ht->unique = 0;
ht->identical = 0;
ht->free_defn = free_defn;
return ht;
}
/* Return pointer to hash entry structure containing s, or NULL if it
* doesn't exist.
*/
void *hash_lookup_structure (const struct hashtable *ht,
const char *s, size_t len)
{
struct nlist *np;
for (np = ht->hashtab[hash (s, len)]; np; np = np->next) {
if (strncmp (s, np->name, len) == 0)
return np;
}
return NULL;
}
/* Return pointer to definition of s, or NULL if it doesn't exist. */
void *hash_lookup (const struct hashtable *ht, const char *s, size_t len)
{
struct nlist *np = hash_lookup_structure (ht, s, len);
if (np)
return np->defn;
else
return NULL;
}
/* Return structure containing definition (never NULL). */
struct nlist *hash_install (struct hashtable *ht, const char *name, size_t len,
void *defn)
{
struct nlist *np;
np = hash_lookup_structure (ht, name, len);
if (np) {
if (np->defn)
ht->free_defn (np->defn);
} else {
unsigned int hashval;
np = XMALLOC (struct nlist);
np->name = xstrndup (name, len);
hashval = hash (name, len);
/* record uniqueness if debugging */
if (debug_level) {
if (ht->hashtab[hashval])
ht->identical++;
else
ht->unique++;
}
/* point to last entry with this hash */
np->next = ht->hashtab[hashval];
/* attach to hashtab array */
ht->hashtab[hashval] = np;
}
np->defn = defn;
return np;
}
/* Remove structure containing name from the hash tree. */
void hash_remove (struct hashtable *ht, const char *name, size_t len)
{
struct nlist *np, *prev;
unsigned int hashval = hash (name, len);
for (np = ht->hashtab[hashval], prev = NULL; np;
prev = np, np = np->next) {
if (strncmp (name, np->name, len) == 0) {
if (prev)
prev->next = np->next;
else
ht->hashtab[hashval] = np->next;
if (np->defn)
ht->free_defn (np->defn);
free (np->name);
free (np);
return;
}
}
}
/* Free up the hash tree (garbage collection). Also call the free_defn()
* hook to free up values if necessary.
*/
void hash_free (struct hashtable *ht)
{
int i;
if (!ht)
return;
debug ("hash_free: %d entries, %d (%d%%) unique\n",
ht->unique + ht->identical,
ht->unique,
ht->unique ? (ht->unique * 100) / (ht->unique + ht->identical)
: 0);
for (i = 0; i < HASHSIZE; i++) {
struct nlist *np;
np = ht->hashtab[i];
while (np) {
struct nlist *next;
if (np->defn)
ht->free_defn (np->defn);
free (np->name);
next = np->next;
free (np);
np = next;
}
}
free (ht->hashtab);
free (ht);
}
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