linux/lib/ts_fsm.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * lib/ts_fsm.c	   A naive finite state machine text search approach
 *
 * Authors:	Thomas Graf <[email protected]>
 *
 * ==========================================================================
 *
 *   A finite state machine consists of n states (struct ts_fsm_token)
 *   representing the pattern as a finite automaton. The data is read
 *   sequentially on an octet basis. Every state token specifies the number
 *   of recurrences and the type of value accepted which can be either a
 *   specific character or ctype based set of characters. The available
 *   type of recurrences include 1, (0|1), [0 n], and [1 n].
 *
 *   The algorithm differs between strict/non-strict mode specifying
 *   whether the pattern has to start at the first octet. Strict mode
 *   is enabled by default and can be disabled by inserting
 *   TS_FSM_HEAD_IGNORE as the first token in the chain.
 *
 *   The runtime performance of the algorithm should be around O(n),
 *   however while in strict mode the average runtime can be better.
 */

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

struct ts_fsm
{ … };

/* other values derived from ctype.h */
#define _A …
#define _W …

/* Map to _ctype flags and some magic numbers */
static const u16 token_map[TS_FSM_TYPE_MAX+1] = …;

static const u16 token_lookup_tbl[256] = …;		/* 252-255 */

static inline int match_token(struct ts_fsm_token *t, u8 d)
{ … }

static unsigned int fsm_find(struct ts_config *conf, struct ts_state *state)
{ … }

static struct ts_config *fsm_init(const void *pattern, unsigned int len,
				    gfp_t gfp_mask, int flags)
{ … }

static void *fsm_get_pattern(struct ts_config *conf)
{ … }

static unsigned int fsm_get_pattern_len(struct ts_config *conf)
{ … }

static struct ts_ops fsm_ops = …;

static int __init init_fsm(void)
{ … }

static void __exit exit_fsm(void)
{ … }

MODULE_DESCRIPTION(…) …;
MODULE_LICENSE(…) …;

module_init(…) …;
module_exit(exit_fsm);