338 lines
10 KiB
C
338 lines
10 KiB
C
/*
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* lib/ts_fsm.c A naive finite state machine text search approach
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* Authors: Thomas Graf <tgraf@suug.ch>
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*
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* ==========================================================================
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*
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* A finite state machine consists of n states (struct ts_fsm_token)
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* representing the pattern as a finite automation. The data is read
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* sequentially on an octet basis. Every state token specifies the number
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* of recurrences and the type of value accepted which can be either a
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* specific character or ctype based set of characters. The available
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* type of recurrences include 1, (0|1), [0 n], and [1 n].
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*
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* The algorithm differs between strict/non-strict mode specifying
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* whether the pattern has to start at the first octet. Strict mode
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* is enabled by default and can be disabled by inserting
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* TS_FSM_HEAD_IGNORE as the first token in the chain.
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*
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* The runtime performance of the algorithm should be around O(n),
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* however while in strict mode the average runtime can be better.
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*/
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/string.h>
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#include <linux/ctype.h>
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#include <linux/textsearch.h>
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#include <linux/textsearch_fsm.h>
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struct ts_fsm
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{
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unsigned int ntokens;
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struct ts_fsm_token tokens[0];
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};
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/* other values derived from ctype.h */
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#define _A 0x100 /* ascii */
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#define _W 0x200 /* wildcard */
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/* Map to _ctype flags and some magic numbers */
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static const u16 token_map[TS_FSM_TYPE_MAX+1] = {
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[TS_FSM_SPECIFIC] = 0,
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[TS_FSM_WILDCARD] = _W,
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[TS_FSM_CNTRL] = _C,
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[TS_FSM_LOWER] = _L,
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[TS_FSM_UPPER] = _U,
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[TS_FSM_PUNCT] = _P,
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[TS_FSM_SPACE] = _S,
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[TS_FSM_DIGIT] = _D,
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[TS_FSM_XDIGIT] = _D | _X,
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[TS_FSM_ALPHA] = _U | _L,
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[TS_FSM_ALNUM] = _U | _L | _D,
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[TS_FSM_PRINT] = _P | _U | _L | _D | _SP,
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[TS_FSM_GRAPH] = _P | _U | _L | _D,
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[TS_FSM_ASCII] = _A,
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};
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static const u16 token_lookup_tbl[256] = {
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_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 0- 3 */
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_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 4- 7 */
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_W|_A|_C, _W|_A|_C|_S, _W|_A|_C|_S, _W|_A|_C|_S, /* 8- 11 */
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_W|_A|_C|_S, _W|_A|_C|_S, _W|_A|_C, _W|_A|_C, /* 12- 15 */
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_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 16- 19 */
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_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 20- 23 */
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_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 24- 27 */
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_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 28- 31 */
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_W|_A|_S|_SP, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 32- 35 */
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_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 36- 39 */
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_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 40- 43 */
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_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 44- 47 */
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_W|_A|_D, _W|_A|_D, _W|_A|_D, _W|_A|_D, /* 48- 51 */
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_W|_A|_D, _W|_A|_D, _W|_A|_D, _W|_A|_D, /* 52- 55 */
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_W|_A|_D, _W|_A|_D, _W|_A|_P, _W|_A|_P, /* 56- 59 */
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_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 60- 63 */
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_W|_A|_P, _W|_A|_U|_X, _W|_A|_U|_X, _W|_A|_U|_X, /* 64- 67 */
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_W|_A|_U|_X, _W|_A|_U|_X, _W|_A|_U|_X, _W|_A|_U, /* 68- 71 */
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_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 72- 75 */
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_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 76- 79 */
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_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 80- 83 */
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_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 84- 87 */
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_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_P, /* 88- 91 */
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_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 92- 95 */
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_W|_A|_P, _W|_A|_L|_X, _W|_A|_L|_X, _W|_A|_L|_X, /* 96- 99 */
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_W|_A|_L|_X, _W|_A|_L|_X, _W|_A|_L|_X, _W|_A|_L, /* 100-103 */
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_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 104-107 */
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_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 108-111 */
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_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 112-115 */
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_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 116-119 */
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_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_P, /* 120-123 */
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_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_C, /* 124-127 */
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_W, _W, _W, _W, /* 128-131 */
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_W, _W, _W, _W, /* 132-135 */
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_W, _W, _W, _W, /* 136-139 */
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_W, _W, _W, _W, /* 140-143 */
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_W, _W, _W, _W, /* 144-147 */
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_W, _W, _W, _W, /* 148-151 */
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_W, _W, _W, _W, /* 152-155 */
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_W, _W, _W, _W, /* 156-159 */
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_W|_S|_SP, _W|_P, _W|_P, _W|_P, /* 160-163 */
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_W|_P, _W|_P, _W|_P, _W|_P, /* 164-167 */
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_W|_P, _W|_P, _W|_P, _W|_P, /* 168-171 */
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_W|_P, _W|_P, _W|_P, _W|_P, /* 172-175 */
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_W|_P, _W|_P, _W|_P, _W|_P, /* 176-179 */
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_W|_P, _W|_P, _W|_P, _W|_P, /* 180-183 */
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_W|_P, _W|_P, _W|_P, _W|_P, /* 184-187 */
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_W|_P, _W|_P, _W|_P, _W|_P, /* 188-191 */
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_W|_U, _W|_U, _W|_U, _W|_U, /* 192-195 */
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_W|_U, _W|_U, _W|_U, _W|_U, /* 196-199 */
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_W|_U, _W|_U, _W|_U, _W|_U, /* 200-203 */
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_W|_U, _W|_U, _W|_U, _W|_U, /* 204-207 */
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_W|_U, _W|_U, _W|_U, _W|_U, /* 208-211 */
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_W|_U, _W|_U, _W|_U, _W|_P, /* 212-215 */
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_W|_U, _W|_U, _W|_U, _W|_U, /* 216-219 */
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_W|_U, _W|_U, _W|_U, _W|_L, /* 220-223 */
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_W|_L, _W|_L, _W|_L, _W|_L, /* 224-227 */
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_W|_L, _W|_L, _W|_L, _W|_L, /* 228-231 */
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_W|_L, _W|_L, _W|_L, _W|_L, /* 232-235 */
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_W|_L, _W|_L, _W|_L, _W|_L, /* 236-239 */
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_W|_L, _W|_L, _W|_L, _W|_L, /* 240-243 */
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_W|_L, _W|_L, _W|_L, _W|_P, /* 244-247 */
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_W|_L, _W|_L, _W|_L, _W|_L, /* 248-251 */
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_W|_L, _W|_L, _W|_L, _W|_L}; /* 252-255 */
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static inline int match_token(struct ts_fsm_token *t, u8 d)
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{
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if (t->type)
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return (token_lookup_tbl[d] & t->type) != 0;
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else
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return t->value == d;
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}
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static unsigned int fsm_find(struct ts_config *conf, struct ts_state *state)
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{
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struct ts_fsm *fsm = ts_config_priv(conf);
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struct ts_fsm_token *cur = NULL, *next;
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unsigned int match_start, block_idx = 0, tok_idx;
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unsigned block_len = 0, strict, consumed = state->offset;
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const u8 *data;
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#define GET_NEXT_BLOCK() \
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({ consumed += block_idx; \
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block_idx = 0; \
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block_len = conf->get_next_block(consumed, &data, conf, state); })
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#define TOKEN_MISMATCH() \
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do { \
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if (strict) \
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goto no_match; \
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block_idx++; \
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goto startover; \
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} while(0)
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#define end_of_data() unlikely(block_idx >= block_len && !GET_NEXT_BLOCK())
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if (end_of_data())
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goto no_match;
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strict = fsm->tokens[0].recur != TS_FSM_HEAD_IGNORE;
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startover:
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match_start = consumed + block_idx;
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for (tok_idx = 0; tok_idx < fsm->ntokens; tok_idx++) {
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cur = &fsm->tokens[tok_idx];
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if (likely(tok_idx < (fsm->ntokens - 1)))
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next = &fsm->tokens[tok_idx + 1];
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else
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next = NULL;
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switch (cur->recur) {
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case TS_FSM_SINGLE:
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if (end_of_data())
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goto no_match;
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if (!match_token(cur, data[block_idx]))
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TOKEN_MISMATCH();
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break;
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case TS_FSM_PERHAPS:
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if (end_of_data() ||
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!match_token(cur, data[block_idx]))
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continue;
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break;
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case TS_FSM_MULTI:
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if (end_of_data())
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goto no_match;
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if (!match_token(cur, data[block_idx]))
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TOKEN_MISMATCH();
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block_idx++;
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/* fall through */
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case TS_FSM_ANY:
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if (next == NULL)
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goto found_match;
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if (end_of_data())
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continue;
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while (!match_token(next, data[block_idx])) {
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if (!match_token(cur, data[block_idx]))
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TOKEN_MISMATCH();
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block_idx++;
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if (end_of_data())
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goto no_match;
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}
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continue;
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/*
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* Optimization: Prefer small local loop over jumping
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* back and forth until garbage at head is munched.
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*/
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case TS_FSM_HEAD_IGNORE:
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if (end_of_data())
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continue;
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while (!match_token(next, data[block_idx])) {
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/*
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* Special case, don't start over upon
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* a mismatch, give the user the
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* chance to specify the type of data
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* allowed to be ignored.
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*/
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if (!match_token(cur, data[block_idx]))
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goto no_match;
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block_idx++;
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if (end_of_data())
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goto no_match;
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}
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match_start = consumed + block_idx;
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continue;
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}
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block_idx++;
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}
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if (end_of_data())
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goto found_match;
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no_match:
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return UINT_MAX;
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found_match:
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state->offset = consumed + block_idx;
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return match_start;
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}
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static struct ts_config *fsm_init(const void *pattern, unsigned int len,
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gfp_t gfp_mask)
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{
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int i, err = -EINVAL;
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struct ts_config *conf;
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struct ts_fsm *fsm;
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struct ts_fsm_token *tokens = (struct ts_fsm_token *) pattern;
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unsigned int ntokens = len / sizeof(*tokens);
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size_t priv_size = sizeof(*fsm) + len;
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if (len % sizeof(struct ts_fsm_token) || ntokens < 1)
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goto errout;
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for (i = 0; i < ntokens; i++) {
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struct ts_fsm_token *t = &tokens[i];
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if (t->type > TS_FSM_TYPE_MAX || t->recur > TS_FSM_RECUR_MAX)
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goto errout;
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if (t->recur == TS_FSM_HEAD_IGNORE &&
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(i != 0 || i == (ntokens - 1)))
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goto errout;
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}
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conf = alloc_ts_config(priv_size, gfp_mask);
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if (IS_ERR(conf))
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return conf;
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fsm = ts_config_priv(conf);
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fsm->ntokens = ntokens;
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memcpy(fsm->tokens, pattern, len);
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for (i = 0; i < fsm->ntokens; i++) {
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struct ts_fsm_token *t = &fsm->tokens[i];
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t->type = token_map[t->type];
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}
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return conf;
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errout:
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return ERR_PTR(err);
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}
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static void *fsm_get_pattern(struct ts_config *conf)
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{
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struct ts_fsm *fsm = ts_config_priv(conf);
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return fsm->tokens;
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}
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static unsigned int fsm_get_pattern_len(struct ts_config *conf)
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{
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struct ts_fsm *fsm = ts_config_priv(conf);
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return fsm->ntokens * sizeof(struct ts_fsm_token);
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}
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static struct ts_ops fsm_ops = {
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.name = "fsm",
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.find = fsm_find,
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.init = fsm_init,
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.get_pattern = fsm_get_pattern,
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.get_pattern_len = fsm_get_pattern_len,
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.owner = THIS_MODULE,
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.list = LIST_HEAD_INIT(fsm_ops.list)
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};
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static int __init init_fsm(void)
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{
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return textsearch_register(&fsm_ops);
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}
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static void __exit exit_fsm(void)
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{
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textsearch_unregister(&fsm_ops);
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}
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MODULE_LICENSE("GPL");
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module_init(init_fsm);
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module_exit(exit_fsm);
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