linux-imx

/*

 * 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)

{