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/* A library of functions that implements a key-value database using a
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hash as the data storage/retrieval system. */
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/* Copyright (C) 1999-2000 Jim Hall <jhall1@isd.net> */
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/*
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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/* The following functions are deprecated: db_init, db_free, db_compare */
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/* Hash concept borrowed from _The C Programming Language_, Second Ed.,
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BWK/DMR. */
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#include <stdio.h>
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#include <stdlib.h> /* malloc */
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#include <string.h> /* strdup */
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#include "db.h"
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/* Function prototypes */
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unsigned hash (char *s);
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/* Global variables */
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static db_t *hashtab[HASHSIZE];
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/* Functions */
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/* hash() - My hash function. This is a little simple, but it will
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suffice. */
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unsigned
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hash (char *s)
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{
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unsigned hashval;
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for (hashval = 0; *s != '\0'; s++)
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{
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/* assign a hash value (iterative) */
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hashval = *s + 31 * hashval;
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}
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/* return the hash value */
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return (hashval % HASHSIZE);
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}
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/* db_fetch() - Query the hash and return a struct that contains the
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key and the pointer. The calling function should not look beyond
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that. */
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db_t *
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db_fetch (char *s)
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{
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db_t *db_ptr;
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for (db_ptr = hashtab[hash(s)]; db_ptr != NULL; db_ptr = db_ptr->next)
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{
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if (strcmp (s, db_ptr->key) == 0)
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{
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/* found it */
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return (db_ptr);
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}
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}
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/* else, not found */
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return (NULL);
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}
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/* db_insert() - Inserts a key,value pair into the hash. If the key
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already exists in the hash, the new value is NOT inserted. */
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db_t *
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db_insert (char *key, char *value)
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{
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db_t *db_ptr;
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unsigned hashval;
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if ((db_ptr = db_fetch (key)) == NULL)
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{
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/* not found */
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db_ptr = (db_t *) malloc (sizeof (*db_ptr));
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if (db_ptr == NULL || (db_ptr->key = strdup (key)) == NULL)
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{
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return (NULL);
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}
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/* insert the key,value into the hash. */
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hashval = hash(key);
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db_ptr->next = hashtab[hashval];
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hashtab[hashval] = db_ptr;
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}
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else
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{
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/* already there */
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free ((void *) db_ptr->value);
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}
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if ((db_ptr ->value = strdup (value)) == NULL)
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{
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return (NULL);
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}
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/* else */
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return (db_ptr);
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}
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