kwset.c

   1 /*
   2  * This file has been copied from commit e7ac713d^ in the GNU grep git
   3  * repository. A few small changes have been made to adapt the code to
   4  * Git.
   5  */
   6
   7 /* kwset.c - search for any of a set of keywords.
   8    Copyright 1989, 1998, 2000, 2005 Free Software Foundation, Inc.
   9
  10    This program is free software; you can redistribute it and/or modify
  11    it under the terms of the GNU General Public License as published by
  12    the Free Software Foundation; either version 2, or (at your option)
  13    any later version.
  14
  15    This program is distributed in the hope that it will be useful,
  16    but WITHOUT ANY WARRANTY; without even the implied warranty of
  17    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18    GNU General Public License for more details.
  19
  20    You should have received a copy of the GNU General Public License
  21    along with this program; if not, write to the Free Software
  22    Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA
  23    02110-1301, USA.  */
  24
  25 /* Written August 1989 by Mike Haertel.
  26    The author may be reached (Email) at the address mike@ai.mit.edu,
  27    or (US mail) as Mike Haertel c/o Free Software Foundation. */
  28
  29 /* The algorithm implemented by these routines bears a startling resemblance
  30    to one discovered by Beate Commentz-Walter, although it is not identical.
  31    See "A String Matching Algorithm Fast on the Average," Technical Report,
  32    IBM-Germany, Scientific Center Heidelberg, Tiergartenstrasse 15, D-6900
  33    Heidelberg, Germany.  See also Aho, A.V., and M. Corasick, "Efficient
  34    String Matching:  An Aid to Bibliographic Search," CACM June 1975,
  35    Vol. 18, No. 6, which describes the failure function used below. */
  36
  37 #include "cache.h"
  38
  39 #include "kwset.h"
  40 #include "compat/obstack.h"
  41
  42 #define NCHAR (UCHAR_MAX + 1)
  43 #define obstack_chunk_alloc xmalloc
  44 #define obstack_chunk_free free
  45
  46 #define U(c) ((unsigned char) (c))
  47
  48 /* Balanced tree of edges and labels leaving a given trie node. */
  49 struct tree
  50 {
  51   struct tree *llink;           /* Left link; MUST be first field. */
  52   struct tree *rlink;           /* Right link (to larger labels). */
  53   struct trie *trie;            /* Trie node pointed to by this edge. */
  54   unsigned char label;          /* Label on this edge. */
  55   char balance;                 /* Difference in depths of subtrees. */
  56 };
  57
  58 /* Node of a trie representing a set of reversed keywords. */
  59 struct trie
  60 {
  61   unsigned int accepting;       /* Word index of accepted word, or zero. */
  62   struct tree *links;           /* Tree of edges leaving this node. */
  63   struct trie *parent;          /* Parent of this node. */
  64   struct trie *next;            /* List of all trie nodes in level order. */
  65   struct trie *fail;            /* Aho-Corasick failure function. */
  66   int depth;                    /* Depth of this node from the root. */
  67   int shift;                    /* Shift function for search failures. */
  68   int maxshift;                 /* Max shift of self and descendants. */
  69 };
  70
  71 /* Structure returned opaquely to the caller, containing everything. */
  72 struct kwset
  73 {
  74   struct obstack obstack;       /* Obstack for node allocation. */
  75   int words;                    /* Number of words in the trie. */
  76   struct trie *trie;            /* The trie itself. */
  77   int mind;                     /* Minimum depth of an accepting node. */
  78   int maxd;                     /* Maximum depth of any node. */
  79   unsigned char delta[NCHAR];   /* Delta table for rapid search. */
  80   struct trie *next[NCHAR];     /* Table of children of the root. */
  81   char *target;                 /* Target string if there's only one. */
  82   int mind2;                    /* Used in Boyer-Moore search for one string. */
  83   unsigned char const *trans;  /* Character translation table. */
  84 };
  85
  86 /* Allocate and initialize a keyword set object, returning an opaque
  87    pointer to it.  Return NULL if memory is not available. */
  88 kwset_t
  89 kwsalloc (unsigned char const *trans)
  90 {
  91   struct kwset *kwset;
  92
  93   kwset = (struct kwset *) xmalloc(sizeof (struct kwset));
  94
  95   obstack_init(&kwset->obstack);
  96   kwset->words = 0;
  97   kwset->trie
  98     = (struct trie *) obstack_alloc(&kwset->obstack, sizeof (struct trie));
  99   if (!kwset->trie)
 100     {
 101       kwsfree((kwset_t) kwset);
 102       return NULL;
 103     }
 104   kwset->trie->accepting = 0;
 105   kwset->trie->links = NULL;
 106   kwset->trie->parent = NULL;
 107   kwset->trie->next = NULL;
 108   kwset->trie->fail = NULL;
 109   kwset->trie->depth = 0;
 110   kwset->trie->shift = 0;
 111   kwset->mind = INT_MAX;
 112   kwset->maxd = -1;
 113   kwset->target = NULL;
 114   kwset->trans = trans;
 115
 116   return (kwset_t) kwset;
 117 }
 118
 119 /* This upper bound is valid for CHAR_BIT >= 4 and
 120    exact for CHAR_BIT in { 4..11, 13, 15, 17, 19 }. */
 121 #define DEPTH_SIZE (CHAR_BIT + CHAR_BIT/2)
 122
 123 /* Add the given string to the contents of the keyword set.  Return NULL
 124    for success, an error message otherwise. */
 125 const char *
 126 kwsincr (kwset_t kws, char const *text, size_t len)
 127 {
 128   struct kwset *kwset;
 129   register struct trie *trie;
 130   register unsigned char label;
 131   register struct tree *link;
 132   register int depth;
 133   struct tree *links[DEPTH_SIZE];
 134   enum { L, R } dirs[DEPTH_SIZE];
 135   struct tree *t, *r, *l, *rl, *lr;
 136
 137   kwset = (struct kwset *) kws;
 138   trie = kwset->trie;
 139   text += len;
 140
 141   /* Descend the trie (built of reversed keywords) character-by-character,
 142      installing new nodes when necessary. */
 143   while (len--)
 144     {
 145       label = kwset->trans ? kwset->trans[U(*--text)] : *--text;
 146
 147       /* Descend the tree of outgoing links for this trie node,
 148          looking for the current character and keeping track
 149          of the path followed. */
 150       link = trie->links;
 151       links[0] = (struct tree *) &trie->links;
 152       dirs[0] = L;
 153       depth = 1;
 154
 155       while (link && label != link->label)
 156         {
 157           links[depth] = link;
 158           if (label < link->label)
 159             dirs[depth++] = L, link = link->llink;
 160           else
 161             dirs[depth++] = R, link = link->rlink;
 162         }
 163
 164       /* The current character doesn't have an outgoing link at
 165          this trie node, so build a new trie node and install
 166          a link in the current trie node's tree. */
 167       if (!link)
 168         {
 169           link = (struct tree *) obstack_alloc(&kwset->obstack,
 170                                                sizeof (struct tree));
 171           if (!link)
 172             return "memory exhausted";
 173           link->llink = NULL;
 174           link->rlink = NULL;
 175           link->trie = (struct trie *) obstack_alloc(&kwset->obstack,
 176                                                      sizeof (struct trie));
 177           if (!link->trie)
 178             {
 179               obstack_free(&kwset->obstack, link);
 180               return "memory exhausted";
 181             }
 182           link->trie->accepting = 0;
 183           link->trie->links = NULL;
 184           link->trie->parent = trie;
 185           link->trie->next = NULL;
 186           link->trie->fail = NULL;
 187           link->trie->depth = trie->depth + 1;
 188           link->trie->shift = 0;
 189           link->label = label;
 190           link->balance = 0;
 191
 192           /* Install the new tree node in its parent. */
 193           if (dirs[--depth] == L)
 194             links[depth]->llink = link;
 195           else
 196             links[depth]->rlink = link;
 197
 198           /* Back up the tree fixing the balance flags. */
 199           while (depth && !links[depth]->balance)
 200             {
 201               if (dirs[depth] == L)
 202                 --links[depth]->balance;
 203               else
 204                 ++links[depth]->balance;
 205               --depth;
 206             }
 207
 208           /* Rebalance the tree by pointer rotations if necessary. */
 209           if (depth && ((dirs[depth] == L && --links[depth]->balance)
 210                         || (dirs[depth] == R && ++links[depth]->balance)))
 211             {
 212               switch (links[depth]->balance)
 213                 {
 214                 case (char) -2:
 215                   switch (dirs[depth + 1])
 216                     {
 217                     case L:
 218                       r = links[depth], t = r->llink, rl = t->rlink;
 219                       t->rlink = r, r->llink = rl;
 220                       t->balance = r->balance = 0;
 221                       break;
 222                     case R:
 223                       r = links[depth], l = r->llink, t = l->rlink;
 224                       rl = t->rlink, lr = t->llink;
 225                       t->llink = l, l->rlink = lr, t->rlink = r, r->llink = rl;
 226                       l->balance = t->balance != 1 ? 0 : -1;
 227                       r->balance = t->balance != (char) -1 ? 0 : 1;
 228                       t->balance = 0;
 229                       break;
 230                     default:
 231                       abort ();
 232                     }
 233                   break;
 234                 case 2:
 235                   switch (dirs[depth + 1])
 236                     {
 237                     case R:
 238                       l = links[depth], t = l->rlink, lr = t->llink;
 239                       t->llink = l, l->rlink = lr;
 240                       t->balance = l->balance = 0;
 241                       break;
 242                     case L:
 243                       l = links[depth], r = l->rlink, t = r->llink;
 244                       lr = t->llink, rl = t->rlink;
 245                       t->llink = l, l->rlink = lr, t->rlink = r, r->llink = rl;
 246                       l->balance = t->balance != 1 ? 0 : -1;
 247                       r->balance = t->balance != (char) -1 ? 0 : 1;
 248                       t->balance = 0;
 249                       break;
 250                     default:
 251                       abort ();
 252                     }
 253                   break;
 254                 default:
 255                   abort ();
 256                 }
 257
 258               if (dirs[depth - 1] == L)
 259                 links[depth - 1]->llink = t;
 260               else
 261                 links[depth - 1]->rlink = t;
 262             }
 263         }
 264
 265       trie = link->trie;
 266     }
 267
 268   /* Mark the node we finally reached as accepting, encoding the
 269      index number of this word in the keyword set so far. */
 270   if (!trie->accepting)
 271     trie->accepting = 1 + 2 * kwset->words;
 272   ++kwset->words;
 273
 274   /* Keep track of the longest and shortest string of the keyword set. */
 275   if (trie->depth < kwset->mind)
 276     kwset->mind = trie->depth;
 277   if (trie->depth > kwset->maxd)
 278     kwset->maxd = trie->depth;
 279
 280   return NULL;
 281 }
 282
 283 /* Enqueue the trie nodes referenced from the given tree in the
 284    given queue. */
 285 static void
 286 enqueue (struct tree *tree, struct trie **last)
 287 {
 288   if (!tree)
 289     return;
 290   enqueue(tree->llink, last);
 291   enqueue(tree->rlink, last);
 292   (*last) = (*last)->next = tree->trie;
 293 }
 294
 295 /* Compute the Aho-Corasick failure function for the trie nodes referenced
 296    from the given tree, given the failure function for their parent as
 297    well as a last resort failure node. */
 298 static void
 299 treefails (register struct tree const *tree, struct trie const *fail,
 300            struct trie *recourse)
 301 {
 302   register struct tree *link;
 303
 304   if (!tree)
 305     return;
 306
 307   treefails(tree->llink, fail, recourse);
 308   treefails(tree->rlink, fail, recourse);
 309
 310   /* Find, in the chain of fails going back to the root, the first
 311      node that has a descendant on the current label. */
 312   while (fail)
 313     {
 314       link = fail->links;
 315       while (link && tree->label != link->label)
 316         if (tree->label < link->label)
 317           link = link->llink;
 318         else
 319           link = link->rlink;
 320       if (link)
 321         {
 322           tree->trie->fail = link->trie;
 323           return;
 324         }
 325       fail = fail->fail;
 326     }
 327
 328   tree->trie->fail = recourse;
 329 }
 330
 331 /* Set delta entries for the links of the given tree such that
 332    the preexisting delta value is larger than the current depth. */
 333 static void
 334 treedelta (register struct tree const *tree,
 335            register unsigned int depth,
 336            unsigned char delta[])
 337 {
 338   if (!tree)
 339     return;
 340   treedelta(tree->llink, depth, delta);
 341   treedelta(tree->rlink, depth, delta);
 342   if (depth < delta[tree->label])
 343     delta[tree->label] = depth;
 344 }
 345
 346 /* Return true if A has every label in B. */
 347 static int
 348 hasevery (register struct tree const *a, register struct tree const *b)
 349 {
 350   if (!b)
 351     return 1;
 352   if (!hasevery(a, b->llink))
 353     return 0;
 354   if (!hasevery(a, b->rlink))
 355     return 0;
 356   while (a && b->label != a->label)
 357     if (b->label < a->label)
 358       a = a->llink;
 359     else
 360       a = a->rlink;
 361   return !!a;
 362 }
 363
 364 /* Compute a vector, indexed by character code, of the trie nodes
 365    referenced from the given tree. */
 366 static void
 367 treenext (struct tree const *tree, struct trie *next[])
 368 {
 369   if (!tree)
 370     return;
 371   treenext(tree->llink, next);
 372   treenext(tree->rlink, next);
 373   next[tree->label] = tree->trie;
 374 }
 375
 376 /* Compute the shift for each trie node, as well as the delta
 377    table and next cache for the given keyword set. */
 378 const char *
 379 kwsprep (kwset_t kws)
 380 {
 381   register struct kwset *kwset;
 382   register int i;
 383   register struct trie *curr;
 384   register unsigned char const *trans;
 385   unsigned char delta[NCHAR];
 386
 387   kwset = (struct kwset *) kws;
 388
 389   /* Initial values for the delta table; will be changed later.  The
 390      delta entry for a given character is the smallest depth of any
 391      node at which an outgoing edge is labeled by that character. */
 392   memset(delta, kwset->mind < UCHAR_MAX ? kwset->mind : UCHAR_MAX, NCHAR);
 393
 394   /* Check if we can use the simple boyer-moore algorithm, instead
 395      of the hairy commentz-walter algorithm. */
 396   if (kwset->words == 1 && kwset->trans == NULL)
 397     {
 398       char c;
 399
 400       /* Looking for just one string.  Extract it from the trie. */
 401       kwset->target = obstack_alloc(&kwset->obstack, kwset->mind);
 402       if (!kwset->target)
 403         return "memory exhausted";
 404       for (i = kwset->mind - 1, curr = kwset->trie; i >= 0; --i)
 405         {
 406           kwset->target[i] = curr->links->label;
 407           curr = curr->links->trie;
 408         }
 409       /* Build the Boyer Moore delta.  Boy that's easy compared to CW. */
 410       for (i = 0; i < kwset->mind; ++i)
 411         delta[U(kwset->target[i])] = kwset->mind - (i + 1);
 412       /* Find the minimal delta2 shift that we might make after
 413          a backwards match has failed. */
 414       c = kwset->target[kwset->mind - 1];
 415       for (i = kwset->mind - 2; i >= 0; --i)
 416         if (kwset->target[i] == c)
 417           break;
 418       kwset->mind2 = kwset->mind - (i + 1);
 419     }
 420   else
 421     {
 422       register struct trie *fail;
 423       struct trie *last, *next[NCHAR];
 424
 425       /* Traverse the nodes of the trie in level order, simultaneously
 426          computing the delta table, failure function, and shift function. */
 427       for (curr = last = kwset->trie; curr; curr = curr->next)
 428         {
 429           /* Enqueue the immediate descendants in the level order queue. */
 430           enqueue(curr->links, &last);
 431
 432           curr->shift = kwset->mind;
 433           curr->maxshift = kwset->mind;
 434
 435           /* Update the delta table for the descendants of this node. */
 436           treedelta(curr->links, curr->depth, delta);
 437
 438           /* Compute the failure function for the descendants of this node. */
 439           treefails(curr->links, curr->fail, kwset->trie);
 440
 441           /* Update the shifts at each node in the current node's chain
 442              of fails back to the root. */
 443           for (fail = curr->fail; fail; fail = fail->fail)
 444             {
 445               /* If the current node has some outgoing edge that the fail
 446                  doesn't, then the shift at the fail should be no larger
 447                  than the difference of their depths. */
 448               if (!hasevery(fail->links, curr->links))
 449                 if (curr->depth - fail->depth < fail->shift)
 450                   fail->shift = curr->depth - fail->depth;
 451
 452               /* If the current node is accepting then the shift at the
 453                  fail and its descendants should be no larger than the
 454                  difference of their depths. */
 455               if (curr->accepting && fail->maxshift > curr->depth - fail->depth)
 456                 fail->maxshift = curr->depth - fail->depth;
 457             }
 458         }
 459
 460       /* Traverse the trie in level order again, fixing up all nodes whose
 461          shift exceeds their inherited maxshift. */
 462       for (curr = kwset->trie->next; curr; curr = curr->next)
 463         {
 464           if (curr->maxshift > curr->parent->maxshift)
 465             curr->maxshift = curr->parent->maxshift;
 466           if (curr->shift > curr->maxshift)
 467             curr->shift = curr->maxshift;
 468         }
 469
 470       /* Create a vector, indexed by character code, of the outgoing links
 471          from the root node. */
 472       for (i = 0; i < NCHAR; ++i)
 473         next[i] = NULL;
 474       treenext(kwset->trie->links, next);
 475
 476       if ((trans = kwset->trans) != NULL)
 477         for (i = 0; i < NCHAR; ++i)
 478           kwset->next[i] = next[U(trans[i])];
 479       else
 480         memcpy(kwset->next, next, NCHAR * sizeof(struct trie *));
 481     }
 482
 483   /* Fix things up for any translation table. */
 484   if ((trans = kwset->trans) != NULL)
 485     for (i = 0; i < NCHAR; ++i)
 486       kwset->delta[i] = delta[U(trans[i])];
 487   else
 488     memcpy(kwset->delta, delta, NCHAR);
 489
 490   return NULL;
 491 }
 492
 493 /* Fast boyer-moore search. */
 494 static size_t
 495 bmexec (kwset_t kws, char const *text, size_t size)
 496 {
 497   struct kwset const *kwset;
 498   register unsigned char const *d1;
 499   register char const *ep, *sp, *tp;
 500   register int d, gc, i, len, md2;
 501
 502   kwset = (struct kwset const *) kws;
 503   len = kwset->mind;
 504
 505   if (len == 0)
 506     return 0;
 507   if (len > size)
 508     return -1;
 509   if (len == 1)
 510     {
 511       tp = memchr (text, kwset->target[0], size);
 512       return tp ? tp - text : -1;
 513     }
 514
 515   d1 = kwset->delta;
 516   sp = kwset->target + len;
 517   gc = U(sp[-2]);
 518   md2 = kwset->mind2;
 519   tp = text + len;
 520
 521   /* Significance of 12: 1 (initial offset) + 10 (skip loop) + 1 (md2). */
 522   if (size > 12 * len)
 523     /* 11 is not a bug, the initial offset happens only once. */
 524     for (ep = text + size - 11 * len;;)
 525       {
 526         while (tp <= ep)
 527           {
 528             d = d1[U(tp[-1])], tp += d;
 529             d = d1[U(tp[-1])], tp += d;
 530             if (d == 0)
 531               goto found;
 532             d = d1[U(tp[-1])], tp += d;
 533             d = d1[U(tp[-1])], tp += d;
 534             d = d1[U(tp[-1])], tp += d;
 535             if (d == 0)
 536               goto found;
 537             d = d1[U(tp[-1])], tp += d;
 538             d = d1[U(tp[-1])], tp += d;
 539             d = d1[U(tp[-1])], tp += d;
 540             if (d == 0)
 541               goto found;
 542             d = d1[U(tp[-1])], tp += d;
 543             d = d1[U(tp[-1])], tp += d;
 544           }
 545         break;
 546       found:
 547         if (U(tp[-2]) == gc)
 548           {
 549             for (i = 3; i <= len && U(tp[-i]) == U(sp[-i]); ++i)
 550               ;
 551             if (i > len)
 552               return tp - len - text;
 553           }
 554         tp += md2;
 555       }
 556
 557   /* Now we have only a few characters left to search.  We
 558      carefully avoid ever producing an out-of-bounds pointer. */
 559   ep = text + size;
 560   d = d1[U(tp[-1])];
 561   while (d <= ep - tp)
 562     {
 563       d = d1[U((tp += d)[-1])];
 564       if (d != 0)
 565         continue;
 566       if (U(tp[-2]) == gc)
 567         {
 568           for (i = 3; i <= len && U(tp[-i]) == U(sp[-i]); ++i)
 569             ;
 570           if (i > len)
 571             return tp - len - text;
 572         }
 573       d = md2;
 574     }
 575
 576   return -1;
 577 }
 578
 579 /* Hairy multiple string search. */
 580 static size_t
 581 cwexec (kwset_t kws, char const *text, size_t len, struct kwsmatch *kwsmatch)
 582 {
 583   struct kwset const *kwset;
 584   struct trie * const *next;
 585   struct trie const *trie;
 586   struct trie const *accept;
 587   char const *beg, *lim, *mch, *lmch;
 588   register unsigned char c;
 589   register unsigned char const *delta;
 590   register int d;
 591   register char const *end, *qlim;
 592   register struct tree const *tree;
 593   register unsigned char const *trans;
 594
 595   accept = NULL;
 596
 597   /* Initialize register copies and look for easy ways out. */
 598   kwset = (struct kwset *) kws;
 599   if (len < kwset->mind)
 600     return -1;
 601   next = kwset->next;
 602   delta = kwset->delta;
 603   trans = kwset->trans;
 604   lim = text + len;
 605   end = text;
 606   if ((d = kwset->mind) != 0)
 607     mch = NULL;
 608   else
 609     {
 610       mch = text, accept = kwset->trie;
 611       goto match;
 612     }
 613
 614   if (len >= 4 * kwset->mind)
 615     qlim = lim - 4 * kwset->mind;
 616   else
 617     qlim = NULL;
 618
 619   while (lim - end >= d)
 620     {
 621       if (qlim && end <= qlim)
 622         {
 623           end += d - 1;
 624           while ((d = delta[c = *end]) && end < qlim)
 625             {
 626               end += d;
 627               end += delta[U(*end)];
 628               end += delta[U(*end)];
 629             }
 630           ++end;
 631         }
 632       else
 633         d = delta[c = (end += d)[-1]];
 634       if (d)
 635         continue;
 636       beg = end - 1;
 637       trie = next[c];
 638       if (trie->accepting)
 639         {
 640           mch = beg;
 641           accept = trie;
 642         }
 643       d = trie->shift;
 644       while (beg > text)
 645         {
 646           c = trans ? trans[U(*--beg)] : *--beg;
 647           tree = trie->links;
 648           while (tree && c != tree->label)
 649             if (c < tree->label)
 650               tree = tree->llink;
 651             else
 652               tree = tree->rlink;
 653           if (tree)
 654             {
 655               trie = tree->trie;
 656               if (trie->accepting)
 657                 {
 658                   mch = beg;
 659                   accept = trie;
 660                 }
 661             }
 662           else
 663             break;
 664           d = trie->shift;
 665         }
 666       if (mch)
 667         goto match;
 668     }
 669   return -1;
 670
 671  match:
 672   /* Given a known match, find the longest possible match anchored
 673      at or before its starting point.  This is nearly a verbatim
 674      copy of the preceding main search loops. */
 675   if (lim - mch > kwset->maxd)
 676     lim = mch + kwset->maxd;
 677   lmch = NULL;
 678   d = 1;
 679   while (lim - end >= d)
 680     {
 681       if ((d = delta[c = (end += d)[-1]]) != 0)
 682         continue;
 683       beg = end - 1;
 684       if (!(trie = next[c]))
 685         {
 686           d = 1;
 687           continue;
 688         }
 689       if (trie->accepting && beg <= mch)
 690         {
 691           lmch = beg;
 692           accept = trie;
 693         }
 694       d = trie->shift;
 695       while (beg > text)
 696         {
 697           c = trans ? trans[U(*--beg)] : *--beg;
 698           tree = trie->links;
 699           while (tree && c != tree->label)
 700             if (c < tree->label)
 701               tree = tree->llink;
 702             else
 703               tree = tree->rlink;
 704           if (tree)
 705             {
 706               trie = tree->trie;
 707               if (trie->accepting && beg <= mch)
 708                 {
 709                   lmch = beg;
 710                   accept = trie;
 711                 }
 712             }
 713           else
 714             break;
 715           d = trie->shift;
 716         }
 717       if (lmch)
 718         {
 719           mch = lmch;
 720           goto match;
 721         }
 722       if (!d)
 723         d = 1;
 724     }
 725
 726   if (kwsmatch)
 727     {
 728       kwsmatch->index = accept->accepting / 2;
 729       kwsmatch->offset[0] = mch - text;
 730       kwsmatch->size[0] = accept->depth;
 731     }
 732   return mch - text;
 733 }
 734
 735 /* Search through the given text for a match of any member of the
 736    given keyword set.  Return a pointer to the first character of
 737    the matching substring, or NULL if no match is found.  If FOUNDLEN
 738    is non-NULL store in the referenced location the length of the
 739    matching substring.  Similarly, if FOUNDIDX is non-NULL, store
 740    in the referenced location the index number of the particular
 741    keyword matched. */
 742 size_t
 743 kwsexec (kwset_t kws, char const *text, size_t size,
 744          struct kwsmatch *kwsmatch)
 745 {
 746   struct kwset const *kwset = (struct kwset *) kws;
 747   if (kwset->words == 1 && kwset->trans == NULL)
 748     {
 749       size_t ret = bmexec (kws, text, size);
 750       if (kwsmatch != NULL && ret != (size_t) -1)
 751         {
 752           kwsmatch->index = 0;
 753           kwsmatch->offset[0] = ret;
 754           kwsmatch->size[0] = kwset->mind;
 755         }
 756       return ret;
 757     }
 758   else
 759     return cwexec(kws, text, size, kwsmatch);
 760 }
 761
 762 /* Free the components of the given keyword set. */
 763 void
 764 kwsfree (kwset_t kws)
 765 {
 766   struct kwset *kwset;
 767
 768   kwset = (struct kwset *) kws;
 769   obstack_free(&kwset->obstack, NULL);
 770   free(kws);
 771 }