420 lines
9.3 KiB
C
420 lines
9.3 KiB
C
#ifndef lint
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static char *rcsid = "$Header: /home/ncvs/src/lib/libc/stdlib/strhash.c,v 1.1 1995/03/26 10:21:55 jkh Exp $";
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#endif
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/*
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*
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* Copyright 1990
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* Terry Jones & Jordan Hubbard
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*
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* PCS Computer Systeme, GmbH.
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* Munich, West Germany
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*
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*
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* All rights reserved.
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*
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* This is unsupported software and is subject to change without notice.
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* the author makes no representations about the suitability of this software
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* for any purpose. It is supplied "as is" without express or implied
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* warranty.
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*
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* Permission to use, copy, modify, and distribute this software and its
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* documentation for any purpose and without fee is hereby granted, provided
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* that the above copyright notice appear in all copies and that both that
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* copyright notice and this permission notice appear in supporting
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* documentation, and that the name of the author not be used in
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* advertising or publicity pertaining to distribution of the software
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* without specific, written prior permission.
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*
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*/
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/*
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* This is a fairly simple open addressing hash scheme.
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* Terry did all the code, I just did the spec.
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* Thanks again, you crazy Aussie..
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*
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*/
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/*
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* $Log: strhash.c,v $
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* Revision 1.1 1995/03/26 10:21:55 jkh
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* Add the strhash family of routines. They provide a number of features
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* that the db/hash functions don't, and they're much simpler to use for
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* low-overhead string hashing.
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*
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* Revision 1.1 1995/02/25 02:16:34 jkh
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* Second version of this - now support the essentials of a basic
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* attributed file system for storing menu information and command
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* templates. This is not finished yet, but it does compile so I can
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* commit it to the tree now and continue working on it.
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*
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* Revision 2.0 90/03/26 01:44:26 jkh
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* pre-beta check-in
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*
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* Revision 1.8 90/03/09 19:22:35 jkh
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* Fixed bogus comment.
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*
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* Revision 1.7 90/03/09 19:01:08 jkh
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* Added comments, GPL.
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*
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* Revision 1.6 90/03/08 17:55:58 terry
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* Rearranged hash_purge to be a tiny bit more efficient.
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* Added verbose option to hash_stats.
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*
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* Revision 1.5 90/03/08 17:19:54 terry
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* Added hash_purge. Added arg to hash_traverse. Changed all
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* void * to Generic.
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*
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* Revision 1.4 90/03/08 12:02:35 terry
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* Fixed problems with allocation that I screwed up last night.
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* Changed bucket lists to be singly linked. Thanks to JKH, my hero.
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*
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* Revision 1.3 90/03/07 21:33:33 terry
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* Cleaned up a few decls to keep gcc -Wall quiet.
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*
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* Revision 1.2 90/03/07 21:14:53 terry
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* Comments. Added HASH_STATS define. Removed hash_find()
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* and new_node().
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*
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* Revision 1.1 90/03/07 20:49:45 terry
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* Initial revision
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*
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*
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*/
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#include <string.h>
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#include <sys/types.h>
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#include <strhash.h>
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#define HASH_NULL (hash_table *)0
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#define NODE_NULL (hash_node *)0
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#define GENERIC_NULL (void *)0
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#define HASH_SZ 97
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static int _hash(int size, char *key);
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static hash_node *list_find(caddr_t key, hash_node *head);
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/*
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* hash_create()
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*
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* Malloc room for a new hash table and then room for its
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* bucket pointers. Then set all the buckets to
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* point to 0. Return the address of the new table.
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*/
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hash_table *
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hash_create(int size)
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{
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register int i;
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hash_table *new = (hash_table *)malloc(sizeof(hash_table));
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if (!new || size < 0){
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return HASH_NULL;
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}
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if (size == 0){
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size = HASH_SZ;
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}
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if (!(new->buckets = (hash_node **)malloc(size * sizeof(hash_node *)))){
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return HASH_NULL;
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}
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for (i = 0; i < size; i++){
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new->buckets[i] = NODE_NULL;
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}
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new->size = size;
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return new;
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}
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/*
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* list_find()
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*
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* Find the key in the linked list pointed to by head.
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*/
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static hash_node *
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list_find(caddr_t key, hash_node *head)
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{
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while (head){
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if (!strcmp(head->key, key)){
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return head;
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}
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head = head->next;
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}
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return NODE_NULL;
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}
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/*
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* _hash()
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*
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* Compute the hash value for the given key.
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*/
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static int
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_hash(int size, char *key)
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{
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unsigned int h = 0x0;
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while (*key){
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h = (h << 1) ^ (h ^ (unsigned char) *key++);
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}
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h %= size;
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return h;
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}
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/*
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* hash_destroy()
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*
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* Find the key and (if it's there) remove it entirely.
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* The function (*nukefunc)() is in charge of disposing
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* of the storage help by the data associated with the node.
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*/
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void
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hash_destroy(hash_table *table, char *key, void (*nukefunc)())
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{
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int bucket = _hash(table->size, key);
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hash_node *found = table->buckets[bucket];
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hash_node *to_free = NODE_NULL;
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if (!found) {
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return;
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}
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if (!strcmp(found->key, key)) {
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/*
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* It was the head of the list.
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*/
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table->buckets[bucket] = found->next;
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to_free = found;
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}
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else {
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/*
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* Walk the list, looking one ahead.
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*/
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while (found->next) {
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if (!strcmp(found->next->key, key)) {
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to_free = found->next;
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found->next = found->next->next;
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break;
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}
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found = found->next;
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}
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if (!to_free){
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return;
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}
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}
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if (nukefunc)
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(*nukefunc)(to_free->key, to_free->data);
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free(to_free);
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return;
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}
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/*
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* hash_search()
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*
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* Search the table for the given key. Then:
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*
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* 1) If you find it and there is no replacement function, just
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* return what you found. (This is a simple search).
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* 2) If you find it and there is a replacement function, run
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* the function on the data you found, and replace the old
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* data with whatever is passed in datum. Return 0.
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* 3) If you don't find it and there is some datum, insert a
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* new item into the table. Insertions go at the front of
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* the bucket. Return 0.
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* 4) Otherwise just return 0.
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*
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*/
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void *
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hash_search(hash_table *table, caddr_t key, void *datum,
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void (*replace_func)())
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{
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int bucket = hash(table->size, key);
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hash_node *found = list_find(key, table->buckets[bucket]);
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if (found){
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if (!replace_func){
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return found->data;
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}
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else{
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(*replace_func)(found->data);
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found->data = datum;
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}
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}
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else{
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if (datum){
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static int assign_key();
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hash_node *new = (hash_node *)malloc(sizeof(hash_node));
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if (!new || !assign_key(key, new)){
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return GENERIC_NULL;
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}
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new->data = datum;
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new->next = table->buckets[bucket];
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table->buckets[bucket] = new;
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}
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}
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return GENERIC_NULL;
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}
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/*
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* assign_key()
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*
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* Set the key value of a node to be 'key'. Get some space from
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* malloc and copy it in etc. Return 1 if all is well, 0 otherwise.
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*/
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static int
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assign_key(char *key, hash_node *node)
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{
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if (!node || !key){
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return 0;
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}
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if (!(node->key = (char *)malloc(strlen(key) + 1))){
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return 0;
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}
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node->key[0] = '\0';
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strcat(node->key, key);
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return 1;
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}
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/*
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* hash_traverse()
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*
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* Traverse the hash table and run the function func on the
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* data found at each node and the argument we're passed for it.
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*/
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void
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hash_traverse(hash_table *table, int (*func)(), void *arg)
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{
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register int i;
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register int size = table->size;
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if (!func)
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return;
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for (i = 0; i < size; i++) {
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hash_node *n = table->buckets[i];
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while (n) {
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if ((*func)(n->key, n->data, arg) == 0)
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return;
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n = n->next;
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}
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}
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return;
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}
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/*
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* hash_purge()
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*
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* Run through the entire hash table. Call purge_func
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* on the data found at each node, and then free the node.
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* Set all the bucket pointers to 0.
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*/
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void
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hash_purge(hash_table *table, void (*purge_func)(char *p1, void *p2))
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{
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register int i;
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register int size = table->size;
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for (i = 0; i < size; i++) {
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hash_node *n = table->buckets[i];
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if (n) {
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do {
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hash_node *to_free = n;
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if (purge_func) {
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(*purge_func)(n->key, n->data);
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}
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n = n->next;
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free(to_free);
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} while (n);
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table->buckets[i] = NODE_NULL;
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}
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}
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}
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#ifdef HASH_STATS
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#include <stdio.h>
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#define min(a, b) (a) < (b) ? (a) : (b)
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/*
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* hash_stats()
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*
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* Print statistics about the current table allocation to stdout.
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*/
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void
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hash_stats(hash_table *table, int verbose)
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{
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register int i;
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int total_elements = 0;
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int non_empty_buckets = 0;
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int max_count = 0;
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int max_repeats = 0;
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int *counts;
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int size = table->size;
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if (!(counts = (int *)malloc(size * sizeof(int)))){
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fprintf(stderr, "malloc returns 0\n");
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exit(1);
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}
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for (i = 0; i < size; i++){
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int x = 0;
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hash_node *n = table->buckets[i];
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counts[i] = 0;
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while (n){
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if (!x){
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x = 1;
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non_empty_buckets++;
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if (verbose){
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printf("bucket %2d: ", i);
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}
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}
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if (verbose){
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printf(" %s", n->key);
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}
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counts[i]++;
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n = n->next;
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}
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total_elements += counts[i];
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if (counts[i] > max_count){
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max_count = counts[i];
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max_repeats = 1;
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}
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else if (counts[i] == max_count){
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max_repeats++;
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}
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if (counts[i] && verbose){
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printf(" (%d)\n", counts[i]);
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}
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}
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printf("\n");
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printf("%d element%s in storage.\n", total_elements, total_elements == 1 ? "" : "s");
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if (total_elements){
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printf("%d of %d (%.2f%%) buckets are in use\n", non_empty_buckets, size,
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(double)100 * (double)non_empty_buckets / (double)(size));
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printf("the maximum number of elements in a bucket is %d (%d times)\n", max_count, max_repeats);
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printf("average per bucket is %f\n", (double)total_elements / (double)non_empty_buckets);
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printf("optimal would be %f\n", (double)total_elements / (double)(min(size, total_elements)));
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}
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return;
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}
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#endif /* HASH_STATS */
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