Commit 6408f79c authored by Thomas Graf's avatar Thomas Graf Committed by David S. Miller

[LIB]: Naive finite state machine based textsearch

A finite state machine consists of n states (struct ts_fsm_token)
representing the pattern as a finite automation. The data is read
sequentially on a 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 specyfing
whether the pattern has to start at the first octect. 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.
Signed-off-by: default avatarThomas Graf <>
Signed-off-by: default avatarDavid S. Miller <>
parent df3fb93a
#include <linux/types.h>
enum {
TS_FSM_SPECIFIC, /* specific character */
TS_FSM_WILDCARD, /* any character */
TS_FSM_DIGIT, /* isdigit() */
TS_FSM_XDIGIT, /* isxdigit() */
TS_FSM_PRINT, /* isprint() */
TS_FSM_ALPHA, /* isalpha() */
TS_FSM_ALNUM, /* isalnum() */
TS_FSM_ASCII, /* isascii() */
TS_FSM_CNTRL, /* iscntrl() */
TS_FSM_GRAPH, /* isgraph() */
TS_FSM_LOWER, /* islower() */
TS_FSM_UPPER, /* isupper() */
TS_FSM_PUNCT, /* ispunct() */
TS_FSM_SPACE, /* isspace() */
enum {
TS_FSM_SINGLE, /* 1 occurrence */
TS_FSM_PERHAPS, /* 1 or 0 occurrence */
TS_FSM_ANY, /* 0..n occurrences */
TS_FSM_MULTI, /* 1..n occurrences */
TS_FSM_HEAD_IGNORE, /* 0..n ignored occurrences at head */
* struct ts_fsm_token - state machine token (state)
* @type: type of token
* @recur: number of recurrences
* @value: character value for TS_FSM_SPECIFIC
struct ts_fsm_token
__u16 type;
__u8 recur;
__u8 value;
......@@ -80,4 +80,15 @@ config TEXTSEARCH_KMP
To compile this code as a module, choose M here: the
module will be called ts_kmp.
depends on TEXTSEARCH
tristate "Finite state machine"
Say Y here if you want to be able to search text using a
naive finite state machine approach implementing a subset
of regular expressions.
To compile this code as a module, choose M here: the
module will be called ts_fsm.
......@@ -38,6 +38,7 @@ obj-$(CONFIG_REED_SOLOMON) += reed_solomon/
lib-$(CONFIG_TEXTSEARCH) += textsearch.o
obj-$(CONFIG_TEXTSEARCH_KMP) += ts_kmp.o
obj-$(CONFIG_TEXTSEARCH_FSM) += ts_fsm.o
hostprogs-y := gen_crc32table
clean-files := crc32table.h
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