/*
 *  hash.h
 *  SDBM Hash function
 *
 *  Created by Sunrise Telephone Systems Ltd.
 *
 *  This file ("hash.c") is hereby placed into the public domain.
 *
 */

#include <string.h>
#include "globaldefs.h"
#include "hash.h"

// --------------------------------------------------------------------------
// function:  calc_hash(string)
// --------------------------------------------------------------------------
//
// Returns the hash value of the null terminated C string 'string' using the
// SDBM hash algorithm. The number of significant characters for which the
// hash value will be calculated is limited to MAXIMUM_LENGTH_FOR_STRINGS.

unsigned int calc_hash(const char *string) {
	register unsigned int len, index, hash = 0;
	register char ch;
	
	len = strlen(string);
	if (len > MAXIMUM_LENGTH_FOR_STRINGS) {
		len = MAXIMUM_LENGTH_FOR_STRINGS;
	} // end if
	
	for (index = 0; index < len; index++) {
		ch = string[index];
		hash = ch + (hash << 6) + (hash << 16) - hash;
	} // end for
	
	return (hash & 0x7FFFFFFF);
} // end calc_hash

// --------------------------------------------------------------------------
// function:  calc_hash_with_limit(string, limit)
// --------------------------------------------------------------------------
//
// Returns the hash value of the null terminated C string 'string' using the
// SDBM hash algorithm. The number of significant characters for which the
// hash value will be calculated is limited to 'limit'.

unsigned int calc_hash_with_limit(const char *string, unsigned int limit) {
	register unsigned int len, index, hash = 0;
	register char ch;
	
	len = strlen(string);
	if (len > limit) {
		len = limit;
	} // end if
	
	for (index = 0; index < len; index++) {
		ch = string[index];
		hash = ch + (hash << 6) + (hash << 16) - hash;
	} // end for
	
	return (hash & 0x7FFFFFFF);
} // end calc_hash_with_limit

// END OF FILE