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, see <http://www.gnu.org/licenses/>. */
  22
  23 /* Written August 1989 by Mike Haertel.
  24    The author may be reached (Email) at the address mike@ai.mit.edu,
  25    or (US mail) as Mike Haertel c/o Free Software Foundation. */
  26
  27 /* The algorithm implemented by these routines bears a startling resemblance
  28    to one discovered by Beate Commentz-Walter, although it is not identical.
  29    See "A String Matching Algorithm Fast on the Average," Technical Report,
  30    IBM-Germany, Scientific Center Heidelberg, Tiergartenstrasse 15, D-6900
  31    Heidelberg, Germany.  See also Aho, A.V., and M. Corasick, "Efficient
  32    String Matching:  An Aid to Bibliographic Search," CACM June 1975,
  33    Vol. 18, No. 6, which describes the failure function used below. */
  34
  35 #include "cache.h"
  36
  37 #include "kwset.h"
  38 #include "compat/obstack.h"
  39
  40 #define NCHAR (UCHAR_MAX + 1)
  41 /* adapter for `xmalloc()`, which takes `size_t`, not `long` */
  42 static void *obstack_chunk_alloc(long size)
  43 {
  44         if (size < 0)
  45                 BUG("Cannot allocate a negative amount: %ld", size);
  46         return xmalloc(size);
  47 }
  48 #define obstack_chunk_free free
  49
  50 #define U(c) ((unsigned char) (c))
  51
  52 /* Balanced tree of edges and labels leaving a given trie node. */
  53 struct tree
  54 {
  55   struct tree *llink;           /* Left link; MUST be first field. */
  56   struct tree *rlink;           /* Right link (to larger labels). */
  57   struct trie *trie;            /* Trie node pointed to by this edge. */
  58   unsigned char label;          /* Label on this edge. */
  59   char balance;                 /* Difference in depths of subtrees. */
  60 };
  61
  62 /* Node of a trie representing a set of reversed keywords. */
  63 struct trie
  64 {
  65   unsigned int accepting;       /* Word index of accepted word, or zero. */
  66   struct tree *links;           /* Tree of edges leaving this node. */
  67   struct trie *parent;          /* Parent of this node. */
  68   struct trie *next;            /* List of all trie nodes in level order. */
  69   struct trie *fail;            /* Aho-Corasick failure function. */
  70   int depth;                    /* Depth of this node from the root. */
  71   int shift;                    /* Shift function for search failures. */
  72   int maxshift;                 /* Max shift of self and descendants. */
  73 };
  74
  75 /* Structure returned opaquely to the caller, containing everything. */
  76 struct kwset
  77 {
  78   struct obstack obstack;       /* Obstack for node allocation. */
  79   int words;                    /* Number of words in the trie. */
  80   struct trie *trie;            /* The trie itself. */
  81   int mind;                     /* Minimum depth of an accepting node. */
  82   int maxd;                     /* Maximum depth of any node. */
  83   unsigned char delta[NCHAR];   /* Delta table for rapid search. */
  84   struct trie *next[NCHAR];     /* Table of children of the root. */
  85   char *target;                 /* Target string if there's only one. */
  86   int mind2;                    /* Used in Boyer-Moore search for one string. */
  87   unsigned char const *trans;  /* Character translation table. */
  88 };
  89
  90 /* Allocate and initialize a keyword set object, returning an opaque
  91    pointer to it.  Return NULL if memory is not available. */
  92 kwset_t
  93 kwsalloc (unsigned char const *trans)
  94 {
  95   struct kwset *kwset;
  96
  97   kwset = (struct kwset *) xmalloc(sizeof (struct kwset));
  98
  99   obstack_init(&kwset->obstack);
 100   kwset->words = 0;
 101   kwset->trie
 102     = (struct trie *) obstack_alloc(&kwset->obstack, sizeof (struct trie));
 103   if (!kwset->trie)
 104     {
 105       kwsfree((kwset_t) kwset);
 106       return NULL;
 107     }
 108   kwset->trie->accepting = 0;
 109   kwset->trie->links = NULL;
 110   kwset->trie->parent = NULL;
 111   kwset->trie->next = NULL;
 112   kwset->trie->fail = NULL;
 113   kwset->trie->depth = 0;
 114   kwset->trie->shift = 0;
 115   kwset->mind = INT_MAX;
 116   kwset->maxd = -1;
 117   kwset->target = NULL;
 118   kwset->trans = trans;
 119
 120   return (kwset_t) kwset;
 121 }
 122
 123 /* This upper bound is valid for CHAR_BIT >= 4 and
 124    exact for CHAR_BIT in { 4..11, 13, 15, 17, 19 }. */
 125 #define DEPTH_SIZE (CHAR_BIT + CHAR_BIT/2)
 126
 127 /* Add the given string to the contents of the keyword set.  Return NULL
 128    for success, an error message otherwise. */
 129 const char *
 130 kwsincr (kwset_t kws, char const *text, size_t len)
 131 {
 132   struct kwset *kwset;
 133   register struct trie *trie;
 134   register unsigned char label;
 135   register struct tree *link;
 136   register int depth;
 137   struct tree *links[DEPTH_SIZE];
 138   enum { L, R } dirs[DEPTH_SIZE];
 139   struct tree *t, *r, *l, *rl, *lr;
 140
 141   kwset = (struct kwset *) kws;
 142   trie = kwset->trie;
 143   text += len;
 144
 145   /* Descend the trie (built of reversed keywords) character-by-character,
 146      installing new nodes when necessary. */
 147   while (len--)
 148     {
 149       label = kwset->trans ? kwset->trans[U(*--text)] : *--text;
 150
 151       /* Descend the tree of outgoing links for this trie node,
 152          looking for the current character and keeping track
 153          of the path followed. */
 154       link = trie->links;
 155       links[0] = (struct tree *) &trie->links;
 156       dirs[0] = L;
 157       depth = 1;
 158
 159       while (link && label != link->label)
 160         {
 161           links[depth] = link;
 162           if (label < link->label)
 163             dirs[depth++] = L, link = link->llink;
 164           else
 165             dirs[depth++] = R, link = link->rlink;
 166         }
 167
 168       /* The current character doesn't have an outgoing link at
 169          this trie node, so build a new trie node and install
 170          a link in the current trie node's tree. */
 171       if (!link)
 172         {
 173           link = (struct tree *) obstack_alloc(&kwset->obstack,
 174                                                sizeof (struct tree));
 175           if (!link)
 176             return "memory exhausted";
 177           link->llink = NULL;
 178           link->rlink = NULL;
 179           link->trie = (struct trie *) obstack_alloc(&kwset->obstack,
 180                                                      sizeof (struct trie));
 181           if (!link->trie)
 182             {
 183               obstack_free(&kwset->obstack, link);
 184               return "memory exhausted";
 185             }
 186           link->trie->accepting = 0;
 187           link->trie->links = NULL;
 188           link->trie->parent = trie;
 189           link->trie->next = NULL;
 190           link->trie->fail = NULL;
 191           link->trie->depth = trie->depth + 1;
 192           link->trie->shift = 0;
 193           link->label = label;
 194           link->balance = 0;
 195
 196           /* Install the new tree node in its parent. */
 197           if (dirs[--depth] == L)
 198             links[depth]->llink = link;
 199           else
 200             links[depth]->rlink = link;
 201
 202           /* Back up the tree fixing the balance flags. */
 203           while (depth && !links[depth]->balance)
 204             {
 205               if (dirs[depth] == L)
 206                 --links[depth]->balance;
 207               else
 208                 ++links[depth]->balance;
 209               --depth;
 210             }
 211
 212           /* Rebalance the tree by pointer rotations if necessary. */
 213           if (depth && ((dirs[depth] == L && --links[depth]->balance)
 214                         || (dirs[depth] == R && ++links[depth]->balance)))
 215             {
 216               switch (links[depth]->balance)
 217                 {
 218                 case (char) -2:
 219                   switch (dirs[depth + 1])
 220                     {
 221                     case L:
 222                       r = links[depth], t = r->llink, rl = t->rlink;
 223                       t->rlink = r, r->llink = rl;
 224                       t->balance = r->balance = 0;
 225                       break;
 226                     case R:
 227                       r = links[depth], l = r->llink, t = l->rlink;
 228                       rl = t->rlink, lr = t->llink;
 229                       t->llink = l, l->rlink = lr, t->rlink = r, r->llink = rl;
 230                       l->balance = t->balance != 1 ? 0 : -1;
 231                       r->balance = t->balance != (char) -1 ? 0 : 1;
 232                       t->balance = 0;
 233                       break;
 234                     default:
 235                       abort ();
 236                     }
 237                   break;
 238                 case 2:
 239                   switch (dirs[depth + 1])
 240                     {
 241                     case R:
 242                       l = links[depth], t = l->rlink, lr = t->llink;
 243                       t->llink = l, l->rlink = lr;
 244                       t->balance = l->balance = 0;
 245                       break;
 246                     case L:
 247                       l = links[depth], r = l->rlink, t = r->llink;
 248                       lr = t->llink, rl = t->rlink;
 249                       t->llink = l, l->rlink = lr, t->rlink = r, r->llink = rl;
 250                       l->balance = t->balance != 1 ? 0 : -1;
 251                       r->balance = t->balance != (char) -1 ? 0 : 1;
 252                       t->balance = 0;
 253                       break;
 254                     default:
 255                       abort ();
 256                     }
 257                   break;
 258                 default:
 259                   abort ();
 260                 }
 261
 262               if (dirs[depth - 1] == L)
 263                 links[depth - 1]->llink = t;
 264               else
 265                 links[depth - 1]->rlink = t;
 266             }
 267         }
 268
 269       trie = link->trie;
 270     }
 271
 272   /* Mark the node we finally reached as accepting, encoding the
 273      index number of this word in the keyword set so far. */
 274   if (!trie->accepting)
 275     trie->accepting = 1 + 2 * kwset->words;
 276   ++kwset->words;
 277
 278   /* Keep track of the longest and shortest string of the keyword set. */
 279   if (trie->depth < kwset->mind)
 280     kwset->mind = trie->depth;
 281   if (trie->depth > kwset->maxd)
 282     kwset->maxd = trie->depth;
 283
 284   return NULL;
 285 }
 286
 287 /* Enqueue the trie nodes referenced from the given tree in the
 288    given queue. */
 289 static void
 290 enqueue (struct tree *tree, struct trie **last)
 291 {
 292   if (!tree)
 293     return;
 294   enqueue(tree->llink, last);
 295   enqueue(tree->rlink, last);
 296   (*last) = (*last)->next = tree->trie;
 297 }
 298
 299 /* Compute the Aho-Corasick failure function for the trie nodes referenced
 300    from the given tree, given the failure function for their parent as
 301    well as a last resort failure node. */
 302 static void
 303 treefails (register struct tree const *tree, struct trie const *fail,
 304            struct trie *recourse)
 305 {
 306   register struct tree *link;
 307
 308   if (!tree)
 309     return;
 310
 311   treefails(tree->llink, fail, recourse);
 312   treefails(tree->rlink, fail, recourse);
 313
 314   /* Find, in the chain of fails going back to the root, the first
 315      node that has a descendant on the current label. */
 316   while (fail)
 317     {
 318       link = fail->links;
 319       while (link && tree->label != link->label)
 320         if (tree->label < link->label)
 321           link = link->llink;
 322         else
 323           link = link->rlink;
 324       if (link)
 325         {
 326           tree->trie->fail = link->trie;
 327           return;
 328         }
 329       fail = fail->fail;
 330     }
 331
 332   tree->trie->fail = recourse;
 333 }
 334
 335 /* Set delta entries for the links of the given tree such that
 336    the preexisting delta value is larger than the current depth. */
 337 static void
 338 treedelta (register struct tree const *tree,
 339            register unsigned int depth,
 340            unsigned char delta[])
 341 {
 342   if (!tree)
 343     return;
 344   treedelta(tree->llink, depth, delta);
 345   treedelta(tree->rlink, depth, delta);
 346   if (depth < delta[tree->label])
 347     delta[tree->label] = depth;
 348 }
 349
 350 /* Return true if A has every label in B. */
 351 static int
 352 hasevery (register struct tree const *a, register struct tree const *b)
 353 {
 354   if (!b)
 355     return 1;
 356   if (!hasevery(a, b->llink))
 357     return 0;
 358   if (!hasevery(a, b->rlink))
 359     return 0;
 360   while (a && b->label != a->label)
 361     if (b->label < a->label)
 362       a = a->llink;
 363     else
 364       a = a->rlink;
 365   return !!a;
 366 }
 367
 368 /* Compute a vector, indexed by character code, of the trie nodes
 369    referenced from the given tree. */
 370 static void
 371 treenext (struct tree const *tree, struct trie *next[])
 372 {
 373   if (!tree)
 374     return;
 375   treenext(tree->llink, next);
 376   treenext(tree->rlink, next);
 377   next[tree->label] = tree->trie;
 378 }
 379
 380 /* Compute the shift for each trie node, as well as the delta
 381    table and next cache for the given keyword set. */
 382 const char *
 383 kwsprep (kwset_t kws)
 384 {
 385   register struct kwset *kwset;
 386   register int i;
 387   register struct trie *curr;
 388   register unsigned char const *trans;
 389   unsigned char delta[NCHAR];
 390
 391   kwset = (struct kwset *) kws;
 392
 393   /* Initial values for the delta table; will be changed later.  The
 394      delta entry for a given character is the smallest depth of any
 395      node at which an outgoing edge is labeled by that character. */
 396   memset(delta, kwset->mind < UCHAR_MAX ? kwset->mind : UCHAR_MAX, NCHAR);
 397
 398   /* Check if we can use the simple boyer-moore algorithm, instead
 399      of the hairy commentz-walter algorithm. */
 400   if (kwset->words == 1 && kwset->trans == NULL)
 401     {
 402       char c;
 403
 404       /* Looking for just one string.  Extract it from the trie. */
 405       kwset->target = obstack_alloc(&kwset->obstack, kwset->mind);
 406       if (!kwset->target)
 407         return "memory exhausted";
 408       for (i = kwset->mind - 1, curr = kwset->trie; i >= 0; --i)
 409         {
 410           kwset->target[i] = curr->links->label;
 411           curr = curr->links->trie;
 412         }
 413       /* Build the Boyer Moore delta.  Boy that's easy compared to CW. */
 414       for (i = 0; i < kwset->mind; ++i)
 415         delta[U(kwset->target[i])] = kwset->mind - (i + 1);
 416       /* Find the minimal delta2 shift that we might make after
 417          a backwards match has failed. */
 418       c = kwset->target[kwset->mind - 1];
 419       for (i = kwset->mind - 2; i >= 0; --i)
 420         if (kwset->target[i] == c)
 421           break;
 422       kwset->mind2 = kwset->mind - (i + 1);
 423     }
 424   else
 425     {
 426       register struct trie *fail;
 427       struct trie *last, *next[NCHAR];
 428
 429       /* Traverse the nodes of the trie in level order, simultaneously
 430          computing the delta table, failure function, and shift function. */
 431       for (curr = last = kwset->trie; curr; curr = curr->next)
 432         {
 433           /* Enqueue the immediate descendants in the level order queue. */
 434           enqueue(curr->links, &last);
 435
 436           curr->shift = kwset->mind;
 437           curr->maxshift = kwset->mind;
 438
 439           /* Update the delta table for the descendants of this node. */
 440           treedelta(curr->links, curr->depth, delta);
 441
 442           /* Compute the failure function for the descendants of this node. */
 443           treefails(curr->links, curr->fail, kwset->trie);
 444
 445           /* Update the shifts at each node in the current node's chain
 446              of fails back to the root. */
 447           for (fail = curr->fail; fail; fail = fail->fail)
 448             {
 449               /* If the current node has some outgoing edge that the fail
 450                  doesn't, then the shift at the fail should be no larger
 451                  than the difference of their depths. */
 452               if (!hasevery(fail->links, curr->links))
 453                 if (curr->depth - fail->depth < fail->shift)
 454                   fail->shift = curr->depth - fail->depth;
 455
 456               /* If the current node is accepting then the shift at the
 457                  fail and its descendants should be no larger than the
 458                  difference of their depths. */
 459               if (curr->accepting && fail->maxshift > curr->depth - fail->depth)
 460                 fail->maxshift = curr->depth - fail->depth;
 461             }
 462         }
 463
 464       /* Traverse the trie in level order again, fixing up all nodes whose
 465          shift exceeds their inherited maxshift. */
 466       for (curr = kwset->trie->next; curr; curr = curr->next)
 467         {
 468           if (curr->maxshift > curr->parent->maxshift)
 469             curr->maxshift = curr->parent->maxshift;
 470           if (curr->shift > curr->maxshift)
 471             curr->shift = curr->maxshift;
 472         }
 473
 474       /* Create a vector, indexed by character code, of the outgoing links
 475          from the root node. */
 476       for (i = 0; i < NCHAR; ++i)
 477         next[i] = NULL;
 478       treenext(kwset->trie->links, next);
 479
 480       if ((trans = kwset->trans) != NULL)
 481         for (i = 0; i < NCHAR; ++i)
 482           kwset->next[i] = next[U(trans[i])];
 483       else
 484         COPY_ARRAY(kwset->next, next, NCHAR);
 485     }
 486
 487   /* Fix things up for any translation table. */
 488   if ((trans = kwset->trans) != NULL)
 489     for (i = 0; i < NCHAR; ++i)
 490       kwset->delta[i] = delta[U(trans[i])];
 491   else
 492     memcpy(kwset->delta, delta, NCHAR);
 493
 494   return NULL;
 495 }
 496
 497 /* Fast boyer-moore search. */
 498 static size_t
 499 bmexec (kwset_t kws, char const *text, size_t size)
 500 {
 501   struct kwset const *kwset;
 502   register unsigned char const *d1;
 503   register char const *ep, *sp, *tp;
 504   register int d, gc, i, len, md2;
 505
 506   kwset = (struct kwset const *) kws;
 507   len = kwset->mind;
 508
 509   if (len == 0)
 510     return 0;
 511   if (len > size)
 512     return -1;
 513   if (len == 1)
 514     {
 515       tp = memchr (text, kwset->target[0], size);
 516       return tp ? tp - text : -1;
 517     }
 518
 519   d1 = kwset->delta;
 520   sp = kwset->target + len;
 521   gc = U(sp[-2]);
 522   md2 = kwset->mind2;
 523   tp = text + len;
 524
 525   /* Significance of 12: 1 (initial offset) + 10 (skip loop) + 1 (md2). */
 526   if (size > 12 * len)
 527     /* 11 is not a bug, the initial offset happens only once. */
 528     for (ep = text + size - 11 * len;;)
 529       {
 530         while (tp <= ep)
 531           {
 532             d = d1[U(tp[-1])], tp += d;
 533             d = d1[U(tp[-1])], tp += d;
 534             if (d == 0)
 535               goto found;
 536             d = d1[U(tp[-1])], tp += d;
 537             d = d1[U(tp[-1])], tp += d;
 538             d = d1[U(tp[-1])], tp += d;
 539             if (d == 0)
 540               goto found;
 541             d = d1[U(tp[-1])], tp += d;
 542             d = d1[U(tp[-1])], tp += d;
 543             d = d1[U(tp[-1])], tp += d;
 544             if (d == 0)
 545               goto found;
 546             d = d1[U(tp[-1])], tp += d;
 547             d = d1[U(tp[-1])], tp += d;
 548           }
 549         break;
 550       found:
 551         if (U(tp[-2]) == gc)
 552           {
 553             for (i = 3; i <= len && U(tp[-i]) == U(sp[-i]); ++i)
 554               ;
 555             if (i > len)
 556               return tp - len - text;
 557           }
 558         tp += md2;
 559       }
 560
 561   /* Now we have only a few characters left to search.  We
 562      carefully avoid ever producing an out-of-bounds pointer. */
 563   ep = text + size;
 564   d = d1[U(tp[-1])];
 565   while (d <= ep - tp)
 566     {
 567       d = d1[U((tp += d)[-1])];
 568       if (d != 0)
 569         continue;
 570       if (U(tp[-2]) == gc)
 571         {
 572           for (i = 3; i <= len && U(tp[-i]) == U(sp[-i]); ++i)
 573             ;
 574           if (i > len)
 575             return tp - len - text;
 576         }
 577       d = md2;
 578     }
 579
 580   return -1;
 581 }
 582
 583 /* Hairy multiple string search. */
 584 static size_t
 585 cwexec (kwset_t kws, char const *text, size_t len, struct kwsmatch *kwsmatch)
 586 {
 587   struct kwset const *kwset;
 588   struct trie * const *next;
 589   struct trie const *trie;
 590   struct trie const *accept;
 591   char const *beg, *lim, *mch, *lmch;
 592   register unsigned char c;
 593   register unsigned char const *delta;
 594   register int d;
 595   register char const *end, *qlim;
 596   register struct tree const *tree;
 597   register unsigned char const *trans;
 598
 599   accept = NULL;
 600
 601   /* Initialize register copies and look for easy ways out. */
 602   kwset = (struct kwset *) kws;
 603   if (len < kwset->mind)
 604     return -1;
 605   next = kwset->next;
 606   delta = kwset->delta;
 607   trans = kwset->trans;
 608   lim = text + len;
 609   end = text;
 610   if ((d = kwset->mind) != 0)
 611     mch = NULL;
 612   else
 613     {
 614       mch = text, accept = kwset->trie;
 615       goto match;
 616     }
 617
 618   if (len >= 4 * kwset->mind)
 619     qlim = lim - 4 * kwset->mind;
 620   else
 621     qlim = NULL;
 622
 623   while (lim - end >= d)
 624     {
 625       if (qlim && end <= qlim)
 626         {
 627           end += d - 1;
 628           while ((d = delta[c = *end]) && end < qlim)
 629             {
 630               end += d;
 631               end += delta[U(*end)];
 632               end += delta[U(*end)];
 633             }
 634           ++end;
 635         }
 636       else
 637         d = delta[c = (end += d)[-1]];
 638       if (d)
 639         continue;
 640       beg = end - 1;
 641       trie = next[c];
 642       if (trie->accepting)
 643         {
 644           mch = beg;
 645           accept = trie;
 646         }
 647       d = trie->shift;
 648       while (beg > text)
 649         {
 650           c = trans ? trans[U(*--beg)] : *--beg;
 651           tree = trie->links;
 652           while (tree && c != tree->label)
 653             if (c < tree->label)
 654               tree = tree->llink;
 655             else
 656               tree = tree->rlink;
 657           if (tree)
 658             {
 659               trie = tree->trie;
 660               if (trie->accepting)
 661                 {
 662                   mch = beg;
 663                   accept = trie;
 664                 }
 665             }
 666           else
 667             break;
 668           d = trie->shift;
 669         }
 670       if (mch)
 671         goto match;
 672     }
 673   return -1;
 674
 675  match:
 676   /* Given a known match, find the longest possible match anchored
 677      at or before its starting point.  This is nearly a verbatim
 678      copy of the preceding main search loops. */
 679   if (lim - mch > kwset->maxd)
 680     lim = mch + kwset->maxd;
 681   lmch = NULL;
 682   d = 1;
 683   while (lim - end >= d)
 684     {
 685       if ((d = delta[c = (end += d)[-1]]) != 0)
 686         continue;
 687       beg = end - 1;
 688       if (!(trie = next[c]))
 689         {
 690           d = 1;
 691           continue;
 692         }
 693       if (trie->accepting && beg <= mch)
 694         {
 695           lmch = beg;
 696           accept = trie;
 697         }
 698       d = trie->shift;
 699       while (beg > text)
 700         {
 701           c = trans ? trans[U(*--beg)] : *--beg;
 702           tree = trie->links;
 703           while (tree && c != tree->label)
 704             if (c < tree->label)
 705               tree = tree->llink;
 706             else
 707               tree = tree->rlink;
 708           if (tree)
 709             {
 710               trie = tree->trie;
 711               if (trie->accepting && beg <= mch)
 712                 {
 713                   lmch = beg;
 714                   accept = trie;
 715                 }
 716             }
 717           else
 718             break;
 719           d = trie->shift;
 720         }
 721       if (lmch)
 722         {
 723           mch = lmch;
 724           goto match;
 725         }
 726       if (!d)
 727         d = 1;
 728     }
 729
 730   if (kwsmatch)
 731     {
 732       kwsmatch->index = accept->accepting / 2;
 733       kwsmatch->offset[0] = mch - text;
 734       kwsmatch->size[0] = accept->depth;
 735     }
 736   return mch - text;
 737 }
 738
 739 /* Search through the given text for a match of any member of the
 740    given keyword set.  Return a pointer to the first character of
 741    the matching substring, or NULL if no match is found.  If FOUNDLEN
 742    is non-NULL store in the referenced location the length of the
 743    matching substring.  Similarly, if FOUNDIDX is non-NULL, store
 744    in the referenced location the index number of the particular
 745    keyword matched. */
 746 size_t
 747 kwsexec (kwset_t kws, char const *text, size_t size,
 748          struct kwsmatch *kwsmatch)
 749 {
 750   struct kwset const *kwset = (struct kwset *) kws;
 751   if (kwset->words == 1 && kwset->trans == NULL)
 752     {
 753       size_t ret = bmexec (kws, text, size);
 754       if (kwsmatch != NULL && ret != (size_t) -1)
 755         {
 756           kwsmatch->index = 0;
 757           kwsmatch->offset[0] = ret;
 758           kwsmatch->size[0] = kwset->mind;
 759         }
 760       return ret;
 761     }
 762   else
 763     return cwexec(kws, text, size, kwsmatch);
 764 }
 765
 766 /* Free the components of the given keyword set. */
 767 void
 768 kwsfree (kwset_t kws)
 769 {
 770   struct kwset *kwset;
 771
 772   kwset = (struct kwset *) kws;
 773   obstack_free(&kwset->obstack, NULL);
 774   free(kws);
 775 }