420 lines
10 KiB
C
420 lines
10 KiB
C
/************************************************************************
|
||
Copyright 1988, 1991 by Carnegie Mellon University
|
||
|
||
All Rights Reserved
|
||
|
||
Permission to use, copy, modify, and distribute this software and its
|
||
documentation for any purpose and without fee is hereby granted, provided
|
||
that the above copyright notice appear in all copies and that both that
|
||
copyright notice and this permission notice appear in supporting
|
||
documentation, and that the name of Carnegie Mellon University not be used
|
||
in advertising or publicity pertaining to distribution of the software
|
||
without specific, written prior permission.
|
||
|
||
CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
|
||
SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.
|
||
IN NO EVENT SHALL CMU BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
|
||
DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
|
||
PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
|
||
ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
|
||
SOFTWARE.
|
||
|
||
$FreeBSD$
|
||
|
||
************************************************************************/
|
||
|
||
/*
|
||
* Generalized hash table ADT
|
||
*
|
||
* Provides multiple, dynamically-allocated, variable-sized hash tables on
|
||
* various data and keys.
|
||
*
|
||
* This package attempts to follow some of the coding conventions suggested
|
||
* by Bob Sidebotham and the AFS Clean Code Committee of the
|
||
* Information Technology Center at Carnegie Mellon.
|
||
*/
|
||
|
||
|
||
#include <sys/types.h>
|
||
#include <stdlib.h>
|
||
|
||
#ifndef USE_BFUNCS
|
||
#include <memory.h>
|
||
/* Yes, memcpy is OK here (no overlapped copies). */
|
||
#define bcopy(a,b,c) memcpy(b,a,c)
|
||
#define bzero(p,l) memset(p,0,l)
|
||
#define bcmp(a,b,c) memcmp(a,b,c)
|
||
#endif
|
||
|
||
#include "hash.h"
|
||
|
||
#define TRUE 1
|
||
#define FALSE 0
|
||
#ifndef NULL
|
||
#define NULL 0
|
||
#endif
|
||
|
||
/*
|
||
* This can be changed to make internal routines visible to debuggers, etc.
|
||
*/
|
||
#ifndef PRIVATE
|
||
#define PRIVATE static
|
||
#endif
|
||
|
||
#define P(args) args
|
||
|
||
PRIVATE void hashi_FreeMembers P((hash_member *, hash_freefp));
|
||
|
||
#undef P
|
||
|
||
|
||
|
||
/*
|
||
* Hash table initialization routine.
|
||
*
|
||
* This routine creates and intializes a hash table of size "tablesize"
|
||
* entries. Successful calls return a pointer to the hash table (which must
|
||
* be passed to other hash routines to identify the hash table). Failed
|
||
* calls return NULL.
|
||
*/
|
||
|
||
hash_tbl *
|
||
hash_Init(tablesize)
|
||
unsigned tablesize;
|
||
{
|
||
register hash_tbl *hashtblptr;
|
||
register unsigned totalsize;
|
||
|
||
if (tablesize > 0) {
|
||
totalsize = sizeof(hash_tbl)
|
||
+ sizeof(hash_member *) * (tablesize - 1);
|
||
hashtblptr = (hash_tbl *) malloc(totalsize);
|
||
if (hashtblptr) {
|
||
bzero((char *) hashtblptr, totalsize);
|
||
hashtblptr->size = tablesize; /* Success! */
|
||
hashtblptr->bucketnum = 0;
|
||
hashtblptr->member = (hashtblptr->table)[0];
|
||
}
|
||
} else {
|
||
hashtblptr = NULL; /* Disallow zero-length tables */
|
||
}
|
||
return hashtblptr; /* NULL if failure */
|
||
}
|
||
|
||
|
||
|
||
/*
|
||
* Frees an entire linked list of bucket members (used in the open
|
||
* hashing scheme). Does nothing if the passed pointer is NULL.
|
||
*/
|
||
|
||
PRIVATE void
|
||
hashi_FreeMembers(bucketptr, free_data)
|
||
hash_member *bucketptr;
|
||
hash_freefp free_data;
|
||
{
|
||
hash_member *nextbucket;
|
||
while (bucketptr) {
|
||
nextbucket = bucketptr->next;
|
||
(*free_data) (bucketptr->data);
|
||
free((char *) bucketptr);
|
||
bucketptr = nextbucket;
|
||
}
|
||
}
|
||
|
||
|
||
|
||
|
||
/*
|
||
* This routine re-initializes the hash table. It frees all the allocated
|
||
* memory and resets all bucket pointers to NULL.
|
||
*/
|
||
|
||
void
|
||
hash_Reset(hashtable, free_data)
|
||
hash_tbl *hashtable;
|
||
hash_freefp free_data;
|
||
{
|
||
hash_member **bucketptr;
|
||
unsigned i;
|
||
|
||
bucketptr = hashtable->table;
|
||
for (i = 0; i < hashtable->size; i++) {
|
||
hashi_FreeMembers(*bucketptr, free_data);
|
||
*bucketptr++ = NULL;
|
||
}
|
||
hashtable->bucketnum = 0;
|
||
hashtable->member = (hashtable->table)[0];
|
||
}
|
||
|
||
|
||
|
||
/*
|
||
* Generic hash function to calculate a hash code from the given string.
|
||
*
|
||
* For each byte of the string, this function left-shifts the value in an
|
||
* accumulator and then adds the byte into the accumulator. The contents of
|
||
* the accumulator is returned after the entire string has been processed.
|
||
* It is assumed that this result will be used as the "hashcode" parameter in
|
||
* calls to other functions in this package. These functions automatically
|
||
* adjust the hashcode for the size of each hashtable.
|
||
*
|
||
* This algorithm probably works best when the hash table size is a prime
|
||
* number.
|
||
*
|
||
* Hopefully, this function is better than the previous one which returned
|
||
* the sum of the squares of all the bytes. I'm still open to other
|
||
* suggestions for a default hash function. The programmer is more than
|
||
* welcome to supply his/her own hash function as that is one of the design
|
||
* features of this package.
|
||
*/
|
||
|
||
unsigned
|
||
hash_HashFunction(string, len)
|
||
unsigned char *string;
|
||
register unsigned len;
|
||
{
|
||
register unsigned accum;
|
||
|
||
accum = 0;
|
||
for (; len > 0; len--) {
|
||
accum <<= 1;
|
||
accum += (unsigned) (*string++ & 0xFF);
|
||
}
|
||
return accum;
|
||
}
|
||
|
||
|
||
|
||
/*
|
||
* Returns TRUE if at least one entry for the given key exists; FALSE
|
||
* otherwise.
|
||
*/
|
||
|
||
int
|
||
hash_Exists(hashtable, hashcode, compare, key)
|
||
hash_tbl *hashtable;
|
||
unsigned hashcode;
|
||
hash_cmpfp compare;
|
||
hash_datum *key;
|
||
{
|
||
register hash_member *memberptr;
|
||
|
||
memberptr = (hashtable->table)[hashcode % (hashtable->size)];
|
||
while (memberptr) {
|
||
if ((*compare) (key, memberptr->data)) {
|
||
return TRUE; /* Entry does exist */
|
||
}
|
||
memberptr = memberptr->next;
|
||
}
|
||
return FALSE; /* Entry does not exist */
|
||
}
|
||
|
||
|
||
|
||
/*
|
||
* Insert the data item "element" into the hash table using "hashcode"
|
||
* to determine the bucket number, and "compare" and "key" to determine
|
||
* its uniqueness.
|
||
*
|
||
* If the insertion is successful 0 is returned. If a matching entry
|
||
* already exists in the given bucket of the hash table, or some other error
|
||
* occurs, -1 is returned and the insertion is not done.
|
||
*/
|
||
|
||
int
|
||
hash_Insert(hashtable, hashcode, compare, key, element)
|
||
hash_tbl *hashtable;
|
||
unsigned hashcode;
|
||
hash_cmpfp compare;
|
||
hash_datum *key, *element;
|
||
{
|
||
hash_member *temp;
|
||
|
||
hashcode %= hashtable->size;
|
||
if (hash_Exists(hashtable, hashcode, compare, key)) {
|
||
return -1; /* At least one entry already exists */
|
||
}
|
||
temp = (hash_member *) malloc(sizeof(hash_member));
|
||
if (!temp)
|
||
return -1; /* malloc failed! */
|
||
|
||
temp->data = element;
|
||
temp->next = (hashtable->table)[hashcode];
|
||
(hashtable->table)[hashcode] = temp;
|
||
return 0; /* Success */
|
||
}
|
||
|
||
|
||
|
||
/*
|
||
* Delete all data elements which match the given key. If at least one
|
||
* element is found and the deletion is successful, 0 is returned.
|
||
* If no matching elements can be found in the hash table, -1 is returned.
|
||
*/
|
||
|
||
int
|
||
hash_Delete(hashtable, hashcode, compare, key, free_data)
|
||
hash_tbl *hashtable;
|
||
unsigned hashcode;
|
||
hash_cmpfp compare;
|
||
hash_datum *key;
|
||
hash_freefp free_data;
|
||
{
|
||
hash_member *memberptr, *tempptr;
|
||
hash_member *previous = NULL;
|
||
int retval;
|
||
|
||
retval = -1;
|
||
hashcode %= hashtable->size;
|
||
|
||
/*
|
||
* Delete the first member of the list if it matches. Since this moves
|
||
* the second member into the first position we have to keep doing this
|
||
* over and over until it no longer matches.
|
||
*/
|
||
memberptr = (hashtable->table)[hashcode];
|
||
while (memberptr && (*compare) (key, memberptr->data)) {
|
||
(hashtable->table)[hashcode] = memberptr->next;
|
||
/*
|
||
* Stop hashi_FreeMembers() from deleting the whole list!
|
||
*/
|
||
memberptr->next = NULL;
|
||
hashi_FreeMembers(memberptr, free_data);
|
||
memberptr = (hashtable->table)[hashcode];
|
||
retval = 0;
|
||
}
|
||
|
||
/*
|
||
* Now traverse the rest of the list
|
||
*/
|
||
if (memberptr) {
|
||
previous = memberptr;
|
||
memberptr = memberptr->next;
|
||
}
|
||
while (memberptr) {
|
||
if ((*compare) (key, memberptr->data)) {
|
||
tempptr = memberptr;
|
||
previous->next = memberptr = memberptr->next;
|
||
/*
|
||
* Put the brakes on hashi_FreeMembers(). . . .
|
||
*/
|
||
tempptr->next = NULL;
|
||
hashi_FreeMembers(tempptr, free_data);
|
||
retval = 0;
|
||
} else {
|
||
previous = memberptr;
|
||
memberptr = memberptr->next;
|
||
}
|
||
}
|
||
return retval;
|
||
}
|
||
|
||
|
||
|
||
/*
|
||
* Locate and return the data entry associated with the given key.
|
||
*
|
||
* If the data entry is found, a pointer to it is returned. Otherwise,
|
||
* NULL is returned.
|
||
*/
|
||
|
||
hash_datum *
|
||
hash_Lookup(hashtable, hashcode, compare, key)
|
||
hash_tbl *hashtable;
|
||
unsigned hashcode;
|
||
hash_cmpfp compare;
|
||
hash_datum *key;
|
||
{
|
||
hash_member *memberptr;
|
||
|
||
memberptr = (hashtable->table)[hashcode % (hashtable->size)];
|
||
while (memberptr) {
|
||
if ((*compare) (key, memberptr->data)) {
|
||
return (memberptr->data);
|
||
}
|
||
memberptr = memberptr->next;
|
||
}
|
||
return NULL;
|
||
}
|
||
|
||
|
||
|
||
/*
|
||
* Return the next available entry in the hashtable for a linear search
|
||
*/
|
||
|
||
hash_datum *
|
||
hash_NextEntry(hashtable)
|
||
hash_tbl *hashtable;
|
||
{
|
||
register unsigned bucket;
|
||
register hash_member *memberptr;
|
||
|
||
/*
|
||
* First try to pick up where we left off.
|
||
*/
|
||
memberptr = hashtable->member;
|
||
if (memberptr) {
|
||
hashtable->member = memberptr->next; /* Set up for next call */
|
||
return memberptr->data; /* Return the data */
|
||
}
|
||
/*
|
||
* We hit the end of a chain, so look through the array of buckets
|
||
* until we find a new chain (non-empty bucket) or run out of buckets.
|
||
*/
|
||
bucket = hashtable->bucketnum + 1;
|
||
while ((bucket < hashtable->size) &&
|
||
!(memberptr = (hashtable->table)[bucket])) {
|
||
bucket++;
|
||
}
|
||
|
||
/*
|
||
* Check to see if we ran out of buckets.
|
||
*/
|
||
if (bucket >= hashtable->size) {
|
||
/*
|
||
* Reset to top of table for next call.
|
||
*/
|
||
hashtable->bucketnum = 0;
|
||
hashtable->member = (hashtable->table)[0];
|
||
/*
|
||
* But return end-of-table indication to the caller this time.
|
||
*/
|
||
return NULL;
|
||
}
|
||
/*
|
||
* Must have found a non-empty bucket.
|
||
*/
|
||
hashtable->bucketnum = bucket;
|
||
hashtable->member = memberptr->next; /* Set up for next call */
|
||
return memberptr->data; /* Return the data */
|
||
}
|
||
|
||
|
||
|
||
/*
|
||
* Return the first entry in a hash table for a linear search
|
||
*/
|
||
|
||
hash_datum *
|
||
hash_FirstEntry(hashtable)
|
||
hash_tbl *hashtable;
|
||
{
|
||
hashtable->bucketnum = 0;
|
||
hashtable->member = (hashtable->table)[0];
|
||
return hash_NextEntry(hashtable);
|
||
}
|
||
|
||
/*
|
||
* Local Variables:
|
||
* tab-width: 4
|
||
* c-indent-level: 4
|
||
* c-argdecl-indent: 4
|
||
* c-continued-statement-offset: 4
|
||
* c-continued-brace-offset: -4
|
||
* c-label-offset: -4
|
||
* c-brace-offset: 0
|
||
* End:
|
||
*/
|