scummvm/common/hashmap.cpp

/* ScummVM - Scumm Interpreter
 * Copyright (C) 2006 The ScummVM project
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.

 * This program 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 General Public License for more details.

 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * $URL$
 * $Id$
 *
 */

// The hash map (associative array) implementation in this file is
// based on code by Andrew Y. Ng, 1996:

/* 
 * Copyright (c) 1998-2003 Massachusetts Institute of Technology. 
 * This code was developed as part of the Haystack research project 
 * (http://haystack.lcs.mit.edu/). Permission is hereby granted, 
 * free of charge, to any person obtaining a copy of this software 
 * and associated documentation files (the "Software"), to deal in 
 * the Software without restriction, including without limitation 
 * the rights to use, copy, modify, merge, publish, distribute, 
 * sublicense, and/or sell copies of the Software, and to permit 
 * persons to whom the Software is furnished to do so, subject to 
 * the following conditions: 
 * 
 * The above copyright notice and this permission notice shall be 
 * included in all copies or substantial portions of the Software. 
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES 
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT 
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, 
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR 
 * OTHER DEALINGS IN THE SOFTWARE. 
 */

#include "common/hashmap.h"

namespace Common {

// int:
uint hashit(int x, uint hashsize) {
	return x % hashsize;
}

bool data_eq(int x, int y) {
	return x == y;
}

#if 0
// double:
uint hashit(double d, uint hashsize) {
	TODO
}
#endif

bool data_eq(double d1, double d2) {
	return (d1 == d2);
}

// const char *:
uint hashit(const char *str, uint hashsize) {
	const byte *p = (const byte *)str;
	uint hash;
	char c;

	// my31 algo
	hash = 0;
	while ((c = *p++))
		hash = (hash * 31 + c);

	return hash % hashsize;
}

bool data_eq(const char *str1, const char *str2) {
	return !strcmp(str1, str2);
}

// String:
uint hashit(const Common::String &str, uint hashsize) {
	return hashit(str.c_str(), hashsize);
}

bool data_eq(const Common::String &str1, const String &str2) {
	return (str1 == str2);
}

// The following table is taken from the GNU ISO C++ Library's hashtable.h file.
static const uint primes[] = {
	53ul,         97ul,         193ul,       389ul,       769ul,
	1543ul,       3079ul,       6151ul,      12289ul,     24593ul,
	49157ul,      98317ul,      196613ul,    393241ul,    786433ul,
	1572869ul,    3145739ul,    6291469ul,   12582917ul,  25165843ul,
	50331653ul,   100663319ul,  201326611ul, 402653189ul, 805306457ul,
	1610612741ul, 3221225473ul, 4294967291ul
};

uint nextTableSize(uint x) {
	int i = 0;
	while (x >= primes[i])
		i++;
	return primes[i];
}


}	// End of namespace Common