[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>
diff --git a/lib/Kconfig b/lib/Kconfig
index 16b8fa2..455833a 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -80,4 +80,15 @@
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
diff --git a/lib/Makefile b/lib/Makefile
index 6cdb10f..7f6eda4 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -38,6 +38,7 @@
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
diff --git a/lib/ts_fsm.c b/lib/ts_fsm.c
new file mode 100644
index 0000000..d27c0a0
--- /dev/null
+++ b/lib/ts_fsm.c
@@ -0,0 +1,338 @@
+/*
+ * lib/ts_fsm.c A naive finite state machine text search approach
+ *
+ * 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: Thomas Graf <tgraf@suug.ch>
+ *
+ * ==========================================================================
+ *
+ * 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.
+ */
+
+#include <linux/config.h>
+#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
+{
+ unsigned int ntokens;
+ struct ts_fsm_token tokens[0];
+};
+
+/* other values derived from ctype.h */
+#define _A 0x100 /* ascii */
+#define _W 0x200 /* wildcard */
+
+/* Map to _ctype flags and some magic numbers */
+static u16 token_map[TS_FSM_TYPE_MAX+1] = {
+ [TS_FSM_SPECIFIC] = 0,
+ [TS_FSM_WILDCARD] = _W,
+ [TS_FSM_CNTRL] = _C,
+ [TS_FSM_LOWER] = _L,
+ [TS_FSM_UPPER] = _U,
+ [TS_FSM_PUNCT] = _P,
+ [TS_FSM_SPACE] = _S,
+ [TS_FSM_DIGIT] = _D,
+ [TS_FSM_XDIGIT] = _D | _X,
+ [TS_FSM_ALPHA] = _U | _L,
+ [TS_FSM_ALNUM] = _U | _L | _D,
+ [TS_FSM_PRINT] = _P | _U | _L | _D | _SP,
+ [TS_FSM_GRAPH] = _P | _U | _L | _D,
+ [TS_FSM_ASCII] = _A,
+};
+
+static u16 token_lookup_tbl[256] = {
+_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 0- 3 */
+_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 4- 7 */
+_W|_A|_C, _W|_A|_C|_S, _W|_A|_C|_S, _W|_A|_C|_S, /* 8- 11 */
+_W|_A|_C|_S, _W|_A|_C|_S, _W|_A|_C, _W|_A|_C, /* 12- 15 */
+_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 16- 19 */
+_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 20- 23 */
+_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 24- 27 */
+_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 28- 31 */
+_W|_A|_S|_SP, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 32- 35 */
+_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 36- 39 */
+_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 40- 43 */
+_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 44- 47 */
+_W|_A|_D, _W|_A|_D, _W|_A|_D, _W|_A|_D, /* 48- 51 */
+_W|_A|_D, _W|_A|_D, _W|_A|_D, _W|_A|_D, /* 52- 55 */
+_W|_A|_D, _W|_A|_D, _W|_A|_P, _W|_A|_P, /* 56- 59 */
+_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 60- 63 */
+_W|_A|_P, _W|_A|_U|_X, _W|_A|_U|_X, _W|_A|_U|_X, /* 64- 67 */
+_W|_A|_U|_X, _W|_A|_U|_X, _W|_A|_U|_X, _W|_A|_U, /* 68- 71 */
+_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 72- 75 */
+_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 76- 79 */
+_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 80- 83 */
+_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 84- 87 */
+_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_P, /* 88- 91 */
+_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 92- 95 */
+_W|_A|_P, _W|_A|_L|_X, _W|_A|_L|_X, _W|_A|_L|_X, /* 96- 99 */
+_W|_A|_L|_X, _W|_A|_L|_X, _W|_A|_L|_X, _W|_A|_L, /* 100-103 */
+_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 104-107 */
+_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 108-111 */
+_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 112-115 */
+_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 116-119 */
+_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_P, /* 120-123 */
+_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_C, /* 124-127 */
+_W, _W, _W, _W, /* 128-131 */
+_W, _W, _W, _W, /* 132-135 */
+_W, _W, _W, _W, /* 136-139 */
+_W, _W, _W, _W, /* 140-143 */
+_W, _W, _W, _W, /* 144-147 */
+_W, _W, _W, _W, /* 148-151 */
+_W, _W, _W, _W, /* 152-155 */
+_W, _W, _W, _W, /* 156-159 */
+_W|_S|_SP, _W|_P, _W|_P, _W|_P, /* 160-163 */
+_W|_P, _W|_P, _W|_P, _W|_P, /* 164-167 */
+_W|_P, _W|_P, _W|_P, _W|_P, /* 168-171 */
+_W|_P, _W|_P, _W|_P, _W|_P, /* 172-175 */
+_W|_P, _W|_P, _W|_P, _W|_P, /* 176-179 */
+_W|_P, _W|_P, _W|_P, _W|_P, /* 180-183 */
+_W|_P, _W|_P, _W|_P, _W|_P, /* 184-187 */
+_W|_P, _W|_P, _W|_P, _W|_P, /* 188-191 */
+_W|_U, _W|_U, _W|_U, _W|_U, /* 192-195 */
+_W|_U, _W|_U, _W|_U, _W|_U, /* 196-199 */
+_W|_U, _W|_U, _W|_U, _W|_U, /* 200-203 */
+_W|_U, _W|_U, _W|_U, _W|_U, /* 204-207 */
+_W|_U, _W|_U, _W|_U, _W|_U, /* 208-211 */
+_W|_U, _W|_U, _W|_U, _W|_P, /* 212-215 */
+_W|_U, _W|_U, _W|_U, _W|_U, /* 216-219 */
+_W|_U, _W|_U, _W|_U, _W|_L, /* 220-223 */
+_W|_L, _W|_L, _W|_L, _W|_L, /* 224-227 */
+_W|_L, _W|_L, _W|_L, _W|_L, /* 228-231 */
+_W|_L, _W|_L, _W|_L, _W|_L, /* 232-235 */
+_W|_L, _W|_L, _W|_L, _W|_L, /* 236-239 */
+_W|_L, _W|_L, _W|_L, _W|_L, /* 240-243 */
+_W|_L, _W|_L, _W|_L, _W|_P, /* 244-247 */
+_W|_L, _W|_L, _W|_L, _W|_L, /* 248-251 */
+_W|_L, _W|_L, _W|_L, _W|_L}; /* 252-255 */
+
+static inline int match_token(struct ts_fsm_token *t, u8 d)
+{
+ if (t->type)
+ return (token_lookup_tbl[d] & t->type) != 0;
+ else
+ return t->value == d;
+}
+
+static unsigned int fsm_find(struct ts_config *conf, struct ts_state *state)
+{
+ struct ts_fsm *fsm = ts_config_priv(conf);
+ struct ts_fsm_token *cur = NULL, *next;
+ unsigned int match_start, block_idx = 0, tok_idx;
+ unsigned block_len = 0, strict, consumed = state->offset;
+ const u8 *data;
+
+#define GET_NEXT_BLOCK() \
+({ consumed += block_idx; \
+ block_idx = 0; \
+ block_len = conf->get_next_block(consumed, &data, conf, state); })
+
+#define TOKEN_MISMATCH() \
+ do { \
+ if (strict) \
+ goto no_match; \
+ block_idx++; \
+ goto startover; \
+ } while(0)
+
+#define end_of_data() unlikely(block_idx >= block_len && !GET_NEXT_BLOCK())
+
+ if (end_of_data())
+ goto no_match;
+
+ strict = fsm->tokens[0].recur != TS_FSM_HEAD_IGNORE;
+
+startover:
+ match_start = consumed + block_idx;
+
+ for (tok_idx = 0; tok_idx < fsm->ntokens; tok_idx++) {
+ cur = &fsm->tokens[tok_idx];
+
+ if (likely(tok_idx < (fsm->ntokens - 1)))
+ next = &fsm->tokens[tok_idx + 1];
+ else
+ next = NULL;
+
+ switch (cur->recur) {
+ case TS_FSM_SINGLE:
+ if (end_of_data())
+ goto no_match;
+
+ if (!match_token(cur, data[block_idx]))
+ TOKEN_MISMATCH();
+ break;
+
+ case TS_FSM_PERHAPS:
+ if (end_of_data() ||
+ !match_token(cur, data[block_idx]))
+ continue;
+ break;
+
+ case TS_FSM_MULTI:
+ if (end_of_data())
+ goto no_match;
+
+ if (!match_token(cur, data[block_idx]))
+ TOKEN_MISMATCH();
+
+ block_idx++;
+ /* fall through */
+
+ case TS_FSM_ANY:
+ if (next == NULL)
+ goto found_match;
+
+ if (end_of_data())
+ continue;
+
+ while (!match_token(next, data[block_idx])) {
+ if (!match_token(cur, data[block_idx]))
+ TOKEN_MISMATCH();
+ block_idx++;
+ if (end_of_data())
+ goto no_match;
+ }
+ continue;
+
+ /*
+ * Optimization: Prefer small local loop over jumping
+ * back and forth until garbage at head is munched.
+ */
+ case TS_FSM_HEAD_IGNORE:
+ if (end_of_data())
+ continue;
+
+ while (!match_token(next, data[block_idx])) {
+ /*
+ * Special case, don't start over upon
+ * a mismatch, give the user the
+ * chance to specify the type of data
+ * allowed to be ignored.
+ */
+ if (!match_token(cur, data[block_idx]))
+ goto no_match;
+
+ block_idx++;
+ if (end_of_data())
+ goto no_match;
+ }
+
+ match_start = consumed + block_idx;
+ continue;
+ }
+
+ block_idx++;
+ }
+
+ if (end_of_data())
+ goto found_match;
+
+no_match:
+ return UINT_MAX;
+
+found_match:
+ state->offset = consumed + block_idx;
+ return match_start;
+}
+
+static struct ts_config *fsm_init(const void *pattern, unsigned int len,
+ int gfp_mask)
+{
+ int i, err = -EINVAL;
+ struct ts_config *conf;
+ struct ts_fsm *fsm;
+ struct ts_fsm_token *tokens = (struct ts_fsm_token *) pattern;
+ unsigned int ntokens = len / sizeof(*tokens);
+ size_t priv_size = sizeof(*fsm) + len;
+
+ if (len % sizeof(struct ts_fsm_token) || ntokens < 1)
+ goto errout;
+
+ for (i = 0; i < ntokens; i++) {
+ struct ts_fsm_token *t = &tokens[i];
+
+ if (t->type > TS_FSM_TYPE_MAX || t->recur > TS_FSM_RECUR_MAX)
+ goto errout;
+
+ if (t->recur == TS_FSM_HEAD_IGNORE &&
+ (i != 0 || i == (ntokens - 1)))
+ goto errout;
+ }
+
+ conf = alloc_ts_config(priv_size, gfp_mask);
+ if (IS_ERR(conf))
+ return conf;
+
+ fsm = ts_config_priv(conf);
+ fsm->ntokens = ntokens;
+ memcpy(fsm->tokens, pattern, len);
+
+ for (i = 0; i < fsm->ntokens; i++) {
+ struct ts_fsm_token *t = &fsm->tokens[i];
+ t->type = token_map[t->type];
+ }
+
+ return conf;
+
+errout:
+ return ERR_PTR(err);
+}
+
+static void *fsm_get_pattern(struct ts_config *conf)
+{
+ struct ts_fsm *fsm = ts_config_priv(conf);
+ return fsm->tokens;
+}
+
+static unsigned int fsm_get_pattern_len(struct ts_config *conf)
+{
+ struct ts_fsm *fsm = ts_config_priv(conf);
+ return fsm->ntokens * sizeof(struct ts_fsm_token);
+}
+
+static struct ts_ops fsm_ops = {
+ .name = "fsm",
+ .find = fsm_find,
+ .init = fsm_init,
+ .get_pattern = fsm_get_pattern,
+ .get_pattern_len = fsm_get_pattern_len,
+ .owner = THIS_MODULE,
+ .list = LIST_HEAD_INIT(fsm_ops.list)
+};
+
+static int __init init_fsm(void)
+{
+ return textsearch_register(&fsm_ops);
+}
+
+static void __exit exit_fsm(void)
+{
+ textsearch_unregister(&fsm_ops);
+}
+
+MODULE_LICENSE("GPL");
+
+module_init(init_fsm);
+module_exit(exit_fsm);