[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: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

lib/Kconfig

@@ -80,4 +80,15 @@ config TEXTSEARCH_KMP
 	  To compile this code as a module, choose M here: the
 	  module will be called ts_kmp.
 
+config TEXTSEARCH_FSM
+	depends on TEXTSEARCH
+	tristate "Finite state machine"
+	help
+	  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.
+
 endmenu