/*
 * lib/ts_bm.c		Boyer-Moore text search implementation
 *
 *		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.
 *
 * Authors:	Pablo Neira Ayuso <pablo@eurodev.net>
 *
 * ==========================================================================
 * 
 *   Implements Boyer-Moore string matching algorithm:
 *
 *   [1] A Fast String Searching Algorithm, R.S. Boyer and Moore.
 *       Communications of the Association for Computing Machinery, 
 *       20(10), 1977, pp. 762-772.
 *       http://www.cs.utexas.edu/users/moore/publications/fstrpos.pdf
 *
 *   [2] Handbook of Exact String Matching Algorithms, Thierry Lecroq, 2004
 *       http://www-igm.univ-mlv.fr/~lecroq/string/string.pdf
 *
 *   Note: Since Boyer-Moore (BM) performs searches for matchings from right 
 *   to left, it's still possible that a matching could be spread over 
 *   multiple blocks, in that case this algorithm won't find any coincidence.
 *   
 *   If you're willing to ensure that such thing won't ever happen, use the
 *   Knuth-Pratt-Morris (KMP) implementation instead. In conclusion, choose 
 *   the proper string search algorithm depending on your setting. 
 *
 *   Say you're using the textsearch infrastructure for filtering, NIDS or 
 *   any similar security focused purpose, then go KMP. Otherwise, if you 
 *   really care about performance, say you're classifying packets to apply
 *   Quality of Service (QoS) policies, and you don't mind about possible
 *   matchings spread over multiple fragments, then go BM.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/textsearch.h>

/* Alphabet size, use ASCII */
#define ASIZE 256

#if 0
#define DEBUGP printk
#else
#define DEBUGP(args, format...)
#endif

struct ts_bm
{
	u8 *		pattern;
	unsigned int	patlen;
	unsigned int 	bad_shift[ASIZE];
	unsigned int	good_shift[0];
};

static unsigned int bm_find(struct ts_config *conf, struct ts_state *state)