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/* A library of functions that implements a key-value database using a
hash as the data storage/retrieval system. */
/* Copyright (C) 1999-2000 Jim Hall <jhall@freedos.org> */
/*
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/* The following functions are deprecated: db_init, db_free, db_compare */
/* Hash concept borrowed from _The C Programming Language_, Second Ed.,
BWK/DMR. */
#include <stdio.h>
#include <stdlib.h> /* malloc */
#include <string.h> /* strdup */
#include "db.h"
/* Function prototypes */
unsigned hash (char *s);
/* Global variables */
static db_t *hashtab[HASHSIZE];
/* Functions */
/* hash() - My hash function. This is a little simple, but it will
suffice. */
unsigned
hash (char *s)
{
unsigned hashval;
for (hashval = 0; *s != '\0'; s++)
{
/* assign a hash value (iterative) */
hashval = *s + 31 * hashval;
}
/* return the hash value */
return (hashval % HASHSIZE);
}
/* db_fetch() - Query the hash and return a struct that contains the
key and the pointer. The calling function should not look beyond
that. */
db_t *
db_fetch (char *s)
{
db_t *db_ptr;
for (db_ptr = hashtab[hash(s)]; db_ptr != NULL; db_ptr = db_ptr->next)
{
if (strcmp (s, db_ptr->key) == 0)
{
/* found it */
return (db_ptr);
}
}
/* else, not found */
return (NULL);
}
/* db_insert() - Inserts a key,value pair into the hash. If the key
already exists in the hash, the new value is NOT inserted. */
db_t *
db_insert (char *key, char *value)
{
db_t *db_ptr;
unsigned hashval;
if ((db_ptr = db_fetch (key)) == NULL)
{
/* not found */
db_ptr = (db_t *) malloc (sizeof (*db_ptr));
if (db_ptr == NULL || (db_ptr->key = strdup (key)) == NULL)
{
return (NULL);
}
/* insert the key,value into the hash. */
hashval = hash(key);
db_ptr->next = hashtab[hashval];
hashtab[hashval] = db_ptr;
}
else
{
/* already there */
free ((void *) db_ptr->value);
}
if ((db_ptr ->value = strdup (value)) == NULL)
{
return (NULL);
}
/* else */
return (db_ptr);
}
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