The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/lib/ts_fsm.c

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    1 /*
    2  * lib/ts_fsm.c    A naive finite state machine text search approach
    3  *
    4  *              This program is free software; you can redistribute it and/or
    5  *              modify it under the terms of the GNU General Public License
    6  *              as published by the Free Software Foundation; either version
    7  *              2 of the License, or (at your option) any later version.
    8  *
    9  * Authors:     Thomas Graf <tgraf@suug.ch>
   10  *
   11  * ==========================================================================
   12  *
   13  *   A finite state machine consists of n states (struct ts_fsm_token)
   14  *   representing the pattern as a finite automation. The data is read
   15  *   sequentially on an octet basis. Every state token specifies the number
   16  *   of recurrences and the type of value accepted which can be either a
   17  *   specific character or ctype based set of characters. The available
   18  *   type of recurrences include 1, (0|1), [0 n], and [1 n].
   19  *
   20  *   The algorithm differs between strict/non-strict mode specifying
   21  *   whether the pattern has to start at the first octet. Strict mode
   22  *   is enabled by default and can be disabled by inserting
   23  *   TS_FSM_HEAD_IGNORE as the first token in the chain.
   24  *
   25  *   The runtime performance of the algorithm should be around O(n),
   26  *   however while in strict mode the average runtime can be better.
   27  */
   28 
   29 #include <linux/module.h>
   30 #include <linux/types.h>
   31 #include <linux/string.h>
   32 #include <linux/ctype.h>
   33 #include <linux/textsearch.h>
   34 #include <linux/textsearch_fsm.h>
   35 
   36 struct ts_fsm
   37 {
   38         unsigned int            ntokens;
   39         struct ts_fsm_token     tokens[0];
   40 };
   41 
   42 /* other values derived from ctype.h */
   43 #define _A              0x100 /* ascii */
   44 #define _W              0x200 /* wildcard */
   45 
   46 /* Map to _ctype flags and some magic numbers */
   47 static const u16 token_map[TS_FSM_TYPE_MAX+1] = {
   48         [TS_FSM_SPECIFIC] = 0,
   49         [TS_FSM_WILDCARD] = _W,
   50         [TS_FSM_CNTRL]    = _C,
   51         [TS_FSM_LOWER]    = _L,
   52         [TS_FSM_UPPER]    = _U,
   53         [TS_FSM_PUNCT]    = _P,
   54         [TS_FSM_SPACE]    = _S,
   55         [TS_FSM_DIGIT]    = _D,
   56         [TS_FSM_XDIGIT]   = _D | _X,
   57         [TS_FSM_ALPHA]    = _U | _L,
   58         [TS_FSM_ALNUM]    = _U | _L | _D,
   59         [TS_FSM_PRINT]    = _P | _U | _L | _D | _SP,
   60         [TS_FSM_GRAPH]    = _P | _U | _L | _D,
   61         [TS_FSM_ASCII]    = _A,
   62 };
   63 
   64 static const u16 token_lookup_tbl[256] = {
   65 _W|_A|_C,      _W|_A|_C,     _W|_A|_C,     _W|_A|_C,            /*   0-  3 */
   66 _W|_A|_C,      _W|_A|_C,     _W|_A|_C,     _W|_A|_C,            /*   4-  7 */
   67 _W|_A|_C,      _W|_A|_C|_S,  _W|_A|_C|_S,  _W|_A|_C|_S,         /*   8- 11 */
   68 _W|_A|_C|_S,   _W|_A|_C|_S,  _W|_A|_C,     _W|_A|_C,            /*  12- 15 */
   69 _W|_A|_C,      _W|_A|_C,     _W|_A|_C,     _W|_A|_C,            /*  16- 19 */
   70 _W|_A|_C,      _W|_A|_C,     _W|_A|_C,     _W|_A|_C,            /*  20- 23 */
   71 _W|_A|_C,      _W|_A|_C,     _W|_A|_C,     _W|_A|_C,            /*  24- 27 */
   72 _W|_A|_C,      _W|_A|_C,     _W|_A|_C,     _W|_A|_C,            /*  28- 31 */
   73 _W|_A|_S|_SP,  _W|_A|_P,     _W|_A|_P,     _W|_A|_P,            /*  32- 35 */
   74 _W|_A|_P,      _W|_A|_P,     _W|_A|_P,     _W|_A|_P,            /*  36- 39 */
   75 _W|_A|_P,      _W|_A|_P,     _W|_A|_P,     _W|_A|_P,            /*  40- 43 */
   76 _W|_A|_P,      _W|_A|_P,     _W|_A|_P,     _W|_A|_P,            /*  44- 47 */
   77 _W|_A|_D,      _W|_A|_D,     _W|_A|_D,     _W|_A|_D,            /*  48- 51 */
   78 _W|_A|_D,      _W|_A|_D,     _W|_A|_D,     _W|_A|_D,            /*  52- 55 */
   79 _W|_A|_D,      _W|_A|_D,     _W|_A|_P,     _W|_A|_P,            /*  56- 59 */
   80 _W|_A|_P,      _W|_A|_P,     _W|_A|_P,     _W|_A|_P,            /*  60- 63 */
   81 _W|_A|_P,      _W|_A|_U|_X,  _W|_A|_U|_X,  _W|_A|_U|_X,         /*  64- 67 */
   82 _W|_A|_U|_X,   _W|_A|_U|_X,  _W|_A|_U|_X,  _W|_A|_U,            /*  68- 71 */
   83 _W|_A|_U,      _W|_A|_U,     _W|_A|_U,     _W|_A|_U,            /*  72- 75 */
   84 _W|_A|_U,      _W|_A|_U,     _W|_A|_U,     _W|_A|_U,            /*  76- 79 */
   85 _W|_A|_U,      _W|_A|_U,     _W|_A|_U,     _W|_A|_U,            /*  80- 83 */
   86 _W|_A|_U,      _W|_A|_U,     _W|_A|_U,     _W|_A|_U,            /*  84- 87 */
   87 _W|_A|_U,      _W|_A|_U,     _W|_A|_U,     _W|_A|_P,            /*  88- 91 */
   88 _W|_A|_P,      _W|_A|_P,     _W|_A|_P,     _W|_A|_P,            /*  92- 95 */
   89 _W|_A|_P,      _W|_A|_L|_X,  _W|_A|_L|_X,  _W|_A|_L|_X,         /*  96- 99 */
   90 _W|_A|_L|_X,   _W|_A|_L|_X,  _W|_A|_L|_X,  _W|_A|_L,            /* 100-103 */
   91 _W|_A|_L,      _W|_A|_L,     _W|_A|_L,     _W|_A|_L,            /* 104-107 */
   92 _W|_A|_L,      _W|_A|_L,     _W|_A|_L,     _W|_A|_L,            /* 108-111 */
   93 _W|_A|_L,      _W|_A|_L,     _W|_A|_L,     _W|_A|_L,            /* 112-115 */
   94 _W|_A|_L,      _W|_A|_L,     _W|_A|_L,     _W|_A|_L,            /* 116-119 */
   95 _W|_A|_L,      _W|_A|_L,     _W|_A|_L,     _W|_A|_P,            /* 120-123 */
   96 _W|_A|_P,      _W|_A|_P,     _W|_A|_P,     _W|_A|_C,            /* 124-127 */
   97 _W,            _W,           _W,           _W,                  /* 128-131 */
   98 _W,            _W,           _W,           _W,                  /* 132-135 */
   99 _W,            _W,           _W,           _W,                  /* 136-139 */
  100 _W,            _W,           _W,           _W,                  /* 140-143 */
  101 _W,            _W,           _W,           _W,                  /* 144-147 */
  102 _W,            _W,           _W,           _W,                  /* 148-151 */
  103 _W,            _W,           _W,           _W,                  /* 152-155 */
  104 _W,            _W,           _W,           _W,                  /* 156-159 */
  105 _W|_S|_SP,     _W|_P,        _W|_P,        _W|_P,               /* 160-163 */
  106 _W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 164-167 */
  107 _W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 168-171 */
  108 _W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 172-175 */
  109 _W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 176-179 */
  110 _W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 180-183 */
  111 _W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 184-187 */
  112 _W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 188-191 */
  113 _W|_U,         _W|_U,        _W|_U,        _W|_U,               /* 192-195 */
  114 _W|_U,         _W|_U,        _W|_U,        _W|_U,               /* 196-199 */
  115 _W|_U,         _W|_U,        _W|_U,        _W|_U,               /* 200-203 */
  116 _W|_U,         _W|_U,        _W|_U,        _W|_U,               /* 204-207 */
  117 _W|_U,         _W|_U,        _W|_U,        _W|_U,               /* 208-211 */
  118 _W|_U,         _W|_U,        _W|_U,        _W|_P,               /* 212-215 */
  119 _W|_U,         _W|_U,        _W|_U,        _W|_U,               /* 216-219 */
  120 _W|_U,         _W|_U,        _W|_U,        _W|_L,               /* 220-223 */
  121 _W|_L,         _W|_L,        _W|_L,        _W|_L,               /* 224-227 */
  122 _W|_L,         _W|_L,        _W|_L,        _W|_L,               /* 228-231 */
  123 _W|_L,         _W|_L,        _W|_L,        _W|_L,               /* 232-235 */
  124 _W|_L,         _W|_L,        _W|_L,        _W|_L,               /* 236-239 */
  125 _W|_L,         _W|_L,        _W|_L,        _W|_L,               /* 240-243 */
  126 _W|_L,         _W|_L,        _W|_L,        _W|_P,               /* 244-247 */
  127 _W|_L,         _W|_L,        _W|_L,        _W|_L,               /* 248-251 */
  128 _W|_L,         _W|_L,        _W|_L,        _W|_L};              /* 252-255 */
  129 
  130 static inline int match_token(struct ts_fsm_token *t, u8 d)
  131 {
  132         if (t->type)
  133                 return (token_lookup_tbl[d] & t->type) != 0;
  134         else
  135                 return t->value == d;
  136 }
  137 
  138 static unsigned int fsm_find(struct ts_config *conf, struct ts_state *state)
  139 {
  140         struct ts_fsm *fsm = ts_config_priv(conf);
  141         struct ts_fsm_token *cur = NULL, *next;
  142         unsigned int match_start, block_idx = 0, tok_idx;
  143         unsigned block_len = 0, strict, consumed = state->offset;
  144         const u8 *data;
  145 
  146 #define GET_NEXT_BLOCK()                \
  147 ({      consumed += block_idx;          \
  148         block_idx = 0;                  \
  149         block_len = conf->get_next_block(consumed, &data, conf, state); })
  150 
  151 #define TOKEN_MISMATCH()                \
  152         do {                            \
  153                 if (strict)             \
  154                         goto no_match;  \
  155                 block_idx++;            \
  156                 goto startover;         \
  157         } while(0)
  158 
  159 #define end_of_data() unlikely(block_idx >= block_len && !GET_NEXT_BLOCK())
  160 
  161         if (end_of_data())
  162                 goto no_match;
  163 
  164         strict = fsm->tokens[0].recur != TS_FSM_HEAD_IGNORE;
  165 
  166 startover:
  167         match_start = consumed + block_idx;
  168 
  169         for (tok_idx = 0; tok_idx < fsm->ntokens; tok_idx++) {
  170                 cur = &fsm->tokens[tok_idx];
  171 
  172                 if (likely(tok_idx < (fsm->ntokens - 1)))
  173                         next = &fsm->tokens[tok_idx + 1];
  174                 else
  175                         next = NULL;
  176 
  177                 switch (cur->recur) {
  178                 case TS_FSM_SINGLE:
  179                         if (end_of_data())
  180                                 goto no_match;
  181 
  182                         if (!match_token(cur, data[block_idx]))
  183                                 TOKEN_MISMATCH();
  184                         break;
  185 
  186                 case TS_FSM_PERHAPS:
  187                         if (end_of_data() ||
  188                             !match_token(cur, data[block_idx]))
  189                                 continue;
  190                         break;
  191 
  192                 case TS_FSM_MULTI:
  193                         if (end_of_data())
  194                                 goto no_match;
  195 
  196                         if (!match_token(cur, data[block_idx]))
  197                                 TOKEN_MISMATCH();
  198 
  199                         block_idx++;
  200                         /* fall through */
  201 
  202                 case TS_FSM_ANY:
  203                         if (next == NULL)
  204                                 goto found_match;
  205 
  206                         if (end_of_data())
  207                                 continue;
  208 
  209                         while (!match_token(next, data[block_idx])) {
  210                                 if (!match_token(cur, data[block_idx]))
  211                                         TOKEN_MISMATCH();
  212                                 block_idx++;
  213                                 if (end_of_data())
  214                                         goto no_match;
  215                         }
  216                         continue;
  217 
  218                 /*
  219                  * Optimization: Prefer small local loop over jumping
  220                  * back and forth until garbage at head is munched.
  221                  */
  222                 case TS_FSM_HEAD_IGNORE:
  223                         if (end_of_data())
  224                                 continue;
  225 
  226                         while (!match_token(next, data[block_idx])) {
  227                                 /*
  228                                  * Special case, don't start over upon
  229                                  * a mismatch, give the user the
  230                                  * chance to specify the type of data
  231                                  * allowed to be ignored.
  232                                  */
  233                                 if (!match_token(cur, data[block_idx]))
  234                                         goto no_match;
  235 
  236                                 block_idx++;
  237                                 if (end_of_data())
  238                                         goto no_match;
  239                         }
  240 
  241                         match_start = consumed + block_idx;
  242                         continue;
  243                 }
  244 
  245                 block_idx++;
  246         }
  247 
  248         if (end_of_data())
  249                 goto found_match;
  250 
  251 no_match:
  252         return UINT_MAX;
  253 
  254 found_match:
  255         state->offset = consumed + block_idx;
  256         return match_start;
  257 }
  258 
  259 static struct ts_config *fsm_init(const void *pattern, unsigned int len,
  260                                     gfp_t gfp_mask, int flags)
  261 {
  262         int i, err = -EINVAL;
  263         struct ts_config *conf;
  264         struct ts_fsm *fsm;
  265         struct ts_fsm_token *tokens = (struct ts_fsm_token *) pattern;
  266         unsigned int ntokens = len / sizeof(*tokens);
  267         size_t priv_size = sizeof(*fsm) + len;
  268 
  269         if (len  % sizeof(struct ts_fsm_token) || ntokens < 1)
  270                 goto errout;
  271 
  272         if (flags & TS_IGNORECASE)
  273                 goto errout;
  274 
  275         for (i = 0; i < ntokens; i++) {
  276                 struct ts_fsm_token *t = &tokens[i];
  277 
  278                 if (t->type > TS_FSM_TYPE_MAX || t->recur > TS_FSM_RECUR_MAX)
  279                         goto errout;
  280 
  281                 if (t->recur == TS_FSM_HEAD_IGNORE &&
  282                     (i != 0 || i == (ntokens - 1)))
  283                         goto errout;
  284         }
  285 
  286         conf = alloc_ts_config(priv_size, gfp_mask);
  287         if (IS_ERR(conf))
  288                 return conf;
  289 
  290         conf->flags = flags;
  291         fsm = ts_config_priv(conf);
  292         fsm->ntokens = ntokens;
  293         memcpy(fsm->tokens, pattern, len);
  294 
  295         for (i = 0; i < fsm->ntokens; i++) {
  296                 struct ts_fsm_token *t = &fsm->tokens[i];
  297                 t->type = token_map[t->type];
  298         }
  299 
  300         return conf;
  301 
  302 errout:
  303         return ERR_PTR(err);
  304 }
  305 
  306 static void *fsm_get_pattern(struct ts_config *conf)
  307 {
  308         struct ts_fsm *fsm = ts_config_priv(conf);
  309         return fsm->tokens;
  310 }
  311 
  312 static unsigned int fsm_get_pattern_len(struct ts_config *conf)
  313 {
  314         struct ts_fsm *fsm = ts_config_priv(conf);
  315         return fsm->ntokens * sizeof(struct ts_fsm_token);
  316 }
  317 
  318 static struct ts_ops fsm_ops = {
  319         .name             = "fsm",
  320         .find             = fsm_find,
  321         .init             = fsm_init,
  322         .get_pattern      = fsm_get_pattern,
  323         .get_pattern_len  = fsm_get_pattern_len,
  324         .owner            = THIS_MODULE,
  325         .list             = LIST_HEAD_INIT(fsm_ops.list)
  326 };
  327 
  328 static int __init init_fsm(void)
  329 {
  330         return textsearch_register(&fsm_ops);
  331 }
  332 
  333 static void __exit exit_fsm(void)
  334 {
  335         textsearch_unregister(&fsm_ops);
  336 }
  337 
  338 MODULE_LICENSE("GPL");
  339 
  340 module_init(init_fsm);
  341 module_exit(exit_fsm);

Cache object: 4edef21d61fa51d5a9dcd8007a4939ee


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