Merge branch 'cb/test-lint-cp-a'
[git.git] / kwset.c
blob4fb6455acaf1293c4f47f27eb6e47be4d39633e2
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 */
7 /* kwset.c - search for any of a set of keywords.
8 Copyright 1989, 1998, 2000, 2005 Free Software Foundation, Inc.
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.
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.
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/>. */
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. */
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. */
35 #include "cache.h"
37 #include "kwset.h"
38 #include "compat/obstack.h"
40 #define NCHAR (UCHAR_MAX + 1)
41 #define obstack_chunk_alloc xmalloc
42 #define obstack_chunk_free free
44 #define U(c) ((unsigned char) (c))
46 /* Balanced tree of edges and labels leaving a given trie node. */
47 struct tree
49 struct tree *llink; /* Left link; MUST be first field. */
50 struct tree *rlink; /* Right link (to larger labels). */
51 struct trie *trie; /* Trie node pointed to by this edge. */
52 unsigned char label; /* Label on this edge. */
53 char balance; /* Difference in depths of subtrees. */
56 /* Node of a trie representing a set of reversed keywords. */
57 struct trie
59 unsigned int accepting; /* Word index of accepted word, or zero. */
60 struct tree *links; /* Tree of edges leaving this node. */
61 struct trie *parent; /* Parent of this node. */
62 struct trie *next; /* List of all trie nodes in level order. */
63 struct trie *fail; /* Aho-Corasick failure function. */
64 int depth; /* Depth of this node from the root. */
65 int shift; /* Shift function for search failures. */
66 int maxshift; /* Max shift of self and descendants. */
69 /* Structure returned opaquely to the caller, containing everything. */
70 struct kwset
72 struct obstack obstack; /* Obstack for node allocation. */
73 int words; /* Number of words in the trie. */
74 struct trie *trie; /* The trie itself. */
75 int mind; /* Minimum depth of an accepting node. */
76 int maxd; /* Maximum depth of any node. */
77 unsigned char delta[NCHAR]; /* Delta table for rapid search. */
78 struct trie *next[NCHAR]; /* Table of children of the root. */
79 char *target; /* Target string if there's only one. */
80 int mind2; /* Used in Boyer-Moore search for one string. */
81 unsigned char const *trans; /* Character translation table. */
84 /* Allocate and initialize a keyword set object, returning an opaque
85 pointer to it. Return NULL if memory is not available. */
86 kwset_t
87 kwsalloc (unsigned char const *trans)
89 struct kwset *kwset;
91 kwset = (struct kwset *) xmalloc(sizeof (struct kwset));
93 obstack_init(&kwset->obstack);
94 kwset->words = 0;
95 kwset->trie
96 = (struct trie *) obstack_alloc(&kwset->obstack, sizeof (struct trie));
97 if (!kwset->trie)
99 kwsfree((kwset_t) kwset);
100 return NULL;
102 kwset->trie->accepting = 0;
103 kwset->trie->links = NULL;
104 kwset->trie->parent = NULL;
105 kwset->trie->next = NULL;
106 kwset->trie->fail = NULL;
107 kwset->trie->depth = 0;
108 kwset->trie->shift = 0;
109 kwset->mind = INT_MAX;
110 kwset->maxd = -1;
111 kwset->target = NULL;
112 kwset->trans = trans;
114 return (kwset_t) kwset;
117 /* This upper bound is valid for CHAR_BIT >= 4 and
118 exact for CHAR_BIT in { 4..11, 13, 15, 17, 19 }. */
119 #define DEPTH_SIZE (CHAR_BIT + CHAR_BIT/2)
121 /* Add the given string to the contents of the keyword set. Return NULL
122 for success, an error message otherwise. */
123 const char *
124 kwsincr (kwset_t kws, char const *text, size_t len)
126 struct kwset *kwset;
127 register struct trie *trie;
128 register unsigned char label;
129 register struct tree *link;
130 register int depth;
131 struct tree *links[DEPTH_SIZE];
132 enum { L, R } dirs[DEPTH_SIZE];
133 struct tree *t, *r, *l, *rl, *lr;
135 kwset = (struct kwset *) kws;
136 trie = kwset->trie;
137 text += len;
139 /* Descend the trie (built of reversed keywords) character-by-character,
140 installing new nodes when necessary. */
141 while (len--)
143 label = kwset->trans ? kwset->trans[U(*--text)] : *--text;
145 /* Descend the tree of outgoing links for this trie node,
146 looking for the current character and keeping track
147 of the path followed. */
148 link = trie->links;
149 links[0] = (struct tree *) &trie->links;
150 dirs[0] = L;
151 depth = 1;
153 while (link && label != link->label)
155 links[depth] = link;
156 if (label < link->label)
157 dirs[depth++] = L, link = link->llink;
158 else
159 dirs[depth++] = R, link = link->rlink;
162 /* The current character doesn't have an outgoing link at
163 this trie node, so build a new trie node and install
164 a link in the current trie node's tree. */
165 if (!link)
167 link = (struct tree *) obstack_alloc(&kwset->obstack,
168 sizeof (struct tree));
169 if (!link)
170 return "memory exhausted";
171 link->llink = NULL;
172 link->rlink = NULL;
173 link->trie = (struct trie *) obstack_alloc(&kwset->obstack,
174 sizeof (struct trie));
175 if (!link->trie)
177 obstack_free(&kwset->obstack, link);
178 return "memory exhausted";
180 link->trie->accepting = 0;
181 link->trie->links = NULL;
182 link->trie->parent = trie;
183 link->trie->next = NULL;
184 link->trie->fail = NULL;
185 link->trie->depth = trie->depth + 1;
186 link->trie->shift = 0;
187 link->label = label;
188 link->balance = 0;
190 /* Install the new tree node in its parent. */
191 if (dirs[--depth] == L)
192 links[depth]->llink = link;
193 else
194 links[depth]->rlink = link;
196 /* Back up the tree fixing the balance flags. */
197 while (depth && !links[depth]->balance)
199 if (dirs[depth] == L)
200 --links[depth]->balance;
201 else
202 ++links[depth]->balance;
203 --depth;
206 /* Rebalance the tree by pointer rotations if necessary. */
207 if (depth && ((dirs[depth] == L && --links[depth]->balance)
208 || (dirs[depth] == R && ++links[depth]->balance)))
210 switch (links[depth]->balance)
212 case (char) -2:
213 switch (dirs[depth + 1])
215 case L:
216 r = links[depth], t = r->llink, rl = t->rlink;
217 t->rlink = r, r->llink = rl;
218 t->balance = r->balance = 0;
219 break;
220 case R:
221 r = links[depth], l = r->llink, t = l->rlink;
222 rl = t->rlink, lr = t->llink;
223 t->llink = l, l->rlink = lr, t->rlink = r, r->llink = rl;
224 l->balance = t->balance != 1 ? 0 : -1;
225 r->balance = t->balance != (char) -1 ? 0 : 1;
226 t->balance = 0;
227 break;
228 default:
229 abort ();
231 break;
232 case 2:
233 switch (dirs[depth + 1])
235 case R:
236 l = links[depth], t = l->rlink, lr = t->llink;
237 t->llink = l, l->rlink = lr;
238 t->balance = l->balance = 0;
239 break;
240 case L:
241 l = links[depth], r = l->rlink, t = r->llink;
242 lr = t->llink, rl = t->rlink;
243 t->llink = l, l->rlink = lr, t->rlink = r, r->llink = rl;
244 l->balance = t->balance != 1 ? 0 : -1;
245 r->balance = t->balance != (char) -1 ? 0 : 1;
246 t->balance = 0;
247 break;
248 default:
249 abort ();
251 break;
252 default:
253 abort ();
256 if (dirs[depth - 1] == L)
257 links[depth - 1]->llink = t;
258 else
259 links[depth - 1]->rlink = t;
263 trie = link->trie;
266 /* Mark the node we finally reached as accepting, encoding the
267 index number of this word in the keyword set so far. */
268 if (!trie->accepting)
269 trie->accepting = 1 + 2 * kwset->words;
270 ++kwset->words;
272 /* Keep track of the longest and shortest string of the keyword set. */
273 if (trie->depth < kwset->mind)
274 kwset->mind = trie->depth;
275 if (trie->depth > kwset->maxd)
276 kwset->maxd = trie->depth;
278 return NULL;
281 /* Enqueue the trie nodes referenced from the given tree in the
282 given queue. */
283 static void
284 enqueue (struct tree *tree, struct trie **last)
286 if (!tree)
287 return;
288 enqueue(tree->llink, last);
289 enqueue(tree->rlink, last);
290 (*last) = (*last)->next = tree->trie;
293 /* Compute the Aho-Corasick failure function for the trie nodes referenced
294 from the given tree, given the failure function for their parent as
295 well as a last resort failure node. */
296 static void
297 treefails (register struct tree const *tree, struct trie const *fail,
298 struct trie *recourse)
300 register struct tree *link;
302 if (!tree)
303 return;
305 treefails(tree->llink, fail, recourse);
306 treefails(tree->rlink, fail, recourse);
308 /* Find, in the chain of fails going back to the root, the first
309 node that has a descendant on the current label. */
310 while (fail)
312 link = fail->links;
313 while (link && tree->label != link->label)
314 if (tree->label < link->label)
315 link = link->llink;
316 else
317 link = link->rlink;
318 if (link)
320 tree->trie->fail = link->trie;
321 return;
323 fail = fail->fail;
326 tree->trie->fail = recourse;
329 /* Set delta entries for the links of the given tree such that
330 the preexisting delta value is larger than the current depth. */
331 static void
332 treedelta (register struct tree const *tree,
333 register unsigned int depth,
334 unsigned char delta[])
336 if (!tree)
337 return;
338 treedelta(tree->llink, depth, delta);
339 treedelta(tree->rlink, depth, delta);
340 if (depth < delta[tree->label])
341 delta[tree->label] = depth;
344 /* Return true if A has every label in B. */
345 static int
346 hasevery (register struct tree const *a, register struct tree const *b)
348 if (!b)
349 return 1;
350 if (!hasevery(a, b->llink))
351 return 0;
352 if (!hasevery(a, b->rlink))
353 return 0;
354 while (a && b->label != a->label)
355 if (b->label < a->label)
356 a = a->llink;
357 else
358 a = a->rlink;
359 return !!a;
362 /* Compute a vector, indexed by character code, of the trie nodes
363 referenced from the given tree. */
364 static void
365 treenext (struct tree const *tree, struct trie *next[])
367 if (!tree)
368 return;
369 treenext(tree->llink, next);
370 treenext(tree->rlink, next);
371 next[tree->label] = tree->trie;
374 /* Compute the shift for each trie node, as well as the delta
375 table and next cache for the given keyword set. */
376 const char *
377 kwsprep (kwset_t kws)
379 register struct kwset *kwset;
380 register int i;
381 register struct trie *curr;
382 register unsigned char const *trans;
383 unsigned char delta[NCHAR];
385 kwset = (struct kwset *) kws;
387 /* Initial values for the delta table; will be changed later. The
388 delta entry for a given character is the smallest depth of any
389 node at which an outgoing edge is labeled by that character. */
390 memset(delta, kwset->mind < UCHAR_MAX ? kwset->mind : UCHAR_MAX, NCHAR);
392 /* Check if we can use the simple boyer-moore algorithm, instead
393 of the hairy commentz-walter algorithm. */
394 if (kwset->words == 1 && kwset->trans == NULL)
396 char c;
398 /* Looking for just one string. Extract it from the trie. */
399 kwset->target = obstack_alloc(&kwset->obstack, kwset->mind);
400 if (!kwset->target)
401 return "memory exhausted";
402 for (i = kwset->mind - 1, curr = kwset->trie; i >= 0; --i)
404 kwset->target[i] = curr->links->label;
405 curr = curr->links->trie;
407 /* Build the Boyer Moore delta. Boy that's easy compared to CW. */
408 for (i = 0; i < kwset->mind; ++i)
409 delta[U(kwset->target[i])] = kwset->mind - (i + 1);
410 /* Find the minimal delta2 shift that we might make after
411 a backwards match has failed. */
412 c = kwset->target[kwset->mind - 1];
413 for (i = kwset->mind - 2; i >= 0; --i)
414 if (kwset->target[i] == c)
415 break;
416 kwset->mind2 = kwset->mind - (i + 1);
418 else
420 register struct trie *fail;
421 struct trie *last, *next[NCHAR];
423 /* Traverse the nodes of the trie in level order, simultaneously
424 computing the delta table, failure function, and shift function. */
425 for (curr = last = kwset->trie; curr; curr = curr->next)
427 /* Enqueue the immediate descendants in the level order queue. */
428 enqueue(curr->links, &last);
430 curr->shift = kwset->mind;
431 curr->maxshift = kwset->mind;
433 /* Update the delta table for the descendants of this node. */
434 treedelta(curr->links, curr->depth, delta);
436 /* Compute the failure function for the descendants of this node. */
437 treefails(curr->links, curr->fail, kwset->trie);
439 /* Update the shifts at each node in the current node's chain
440 of fails back to the root. */
441 for (fail = curr->fail; fail; fail = fail->fail)
443 /* If the current node has some outgoing edge that the fail
444 doesn't, then the shift at the fail should be no larger
445 than the difference of their depths. */
446 if (!hasevery(fail->links, curr->links))
447 if (curr->depth - fail->depth < fail->shift)
448 fail->shift = curr->depth - fail->depth;
450 /* If the current node is accepting then the shift at the
451 fail and its descendants should be no larger than the
452 difference of their depths. */
453 if (curr->accepting && fail->maxshift > curr->depth - fail->depth)
454 fail->maxshift = curr->depth - fail->depth;
458 /* Traverse the trie in level order again, fixing up all nodes whose
459 shift exceeds their inherited maxshift. */
460 for (curr = kwset->trie->next; curr; curr = curr->next)
462 if (curr->maxshift > curr->parent->maxshift)
463 curr->maxshift = curr->parent->maxshift;
464 if (curr->shift > curr->maxshift)
465 curr->shift = curr->maxshift;
468 /* Create a vector, indexed by character code, of the outgoing links
469 from the root node. */
470 for (i = 0; i < NCHAR; ++i)
471 next[i] = NULL;
472 treenext(kwset->trie->links, next);
474 if ((trans = kwset->trans) != NULL)
475 for (i = 0; i < NCHAR; ++i)
476 kwset->next[i] = next[U(trans[i])];
477 else
478 memcpy(kwset->next, next, NCHAR * sizeof(struct trie *));
481 /* Fix things up for any translation table. */
482 if ((trans = kwset->trans) != NULL)
483 for (i = 0; i < NCHAR; ++i)
484 kwset->delta[i] = delta[U(trans[i])];
485 else
486 memcpy(kwset->delta, delta, NCHAR);
488 return NULL;
491 /* Fast boyer-moore search. */
492 static size_t
493 bmexec (kwset_t kws, char const *text, size_t size)
495 struct kwset const *kwset;
496 register unsigned char const *d1;
497 register char const *ep, *sp, *tp;
498 register int d, gc, i, len, md2;
500 kwset = (struct kwset const *) kws;
501 len = kwset->mind;
503 if (len == 0)
504 return 0;
505 if (len > size)
506 return -1;
507 if (len == 1)
509 tp = memchr (text, kwset->target[0], size);
510 return tp ? tp - text : -1;
513 d1 = kwset->delta;
514 sp = kwset->target + len;
515 gc = U(sp[-2]);
516 md2 = kwset->mind2;
517 tp = text + len;
519 /* Significance of 12: 1 (initial offset) + 10 (skip loop) + 1 (md2). */
520 if (size > 12 * len)
521 /* 11 is not a bug, the initial offset happens only once. */
522 for (ep = text + size - 11 * len;;)
524 while (tp <= ep)
526 d = d1[U(tp[-1])], tp += d;
527 d = d1[U(tp[-1])], tp += d;
528 if (d == 0)
529 goto found;
530 d = d1[U(tp[-1])], tp += d;
531 d = d1[U(tp[-1])], tp += d;
532 d = d1[U(tp[-1])], tp += d;
533 if (d == 0)
534 goto found;
535 d = d1[U(tp[-1])], tp += d;
536 d = d1[U(tp[-1])], tp += d;
537 d = d1[U(tp[-1])], tp += d;
538 if (d == 0)
539 goto found;
540 d = d1[U(tp[-1])], tp += d;
541 d = d1[U(tp[-1])], tp += d;
543 break;
544 found:
545 if (U(tp[-2]) == gc)
547 for (i = 3; i <= len && U(tp[-i]) == U(sp[-i]); ++i)
549 if (i > len)
550 return tp - len - text;
552 tp += md2;
555 /* Now we have only a few characters left to search. We
556 carefully avoid ever producing an out-of-bounds pointer. */
557 ep = text + size;
558 d = d1[U(tp[-1])];
559 while (d <= ep - tp)
561 d = d1[U((tp += d)[-1])];
562 if (d != 0)
563 continue;
564 if (U(tp[-2]) == gc)
566 for (i = 3; i <= len && U(tp[-i]) == U(sp[-i]); ++i)
568 if (i > len)
569 return tp - len - text;
571 d = md2;
574 return -1;
577 /* Hairy multiple string search. */
578 static size_t
579 cwexec (kwset_t kws, char const *text, size_t len, struct kwsmatch *kwsmatch)
581 struct kwset const *kwset;
582 struct trie * const *next;
583 struct trie const *trie;
584 struct trie const *accept;
585 char const *beg, *lim, *mch, *lmch;
586 register unsigned char c;
587 register unsigned char const *delta;
588 register int d;
589 register char const *end, *qlim;
590 register struct tree const *tree;
591 register unsigned char const *trans;
593 accept = NULL;
595 /* Initialize register copies and look for easy ways out. */
596 kwset = (struct kwset *) kws;
597 if (len < kwset->mind)
598 return -1;
599 next = kwset->next;
600 delta = kwset->delta;
601 trans = kwset->trans;
602 lim = text + len;
603 end = text;
604 if ((d = kwset->mind) != 0)
605 mch = NULL;
606 else
608 mch = text, accept = kwset->trie;
609 goto match;
612 if (len >= 4 * kwset->mind)
613 qlim = lim - 4 * kwset->mind;
614 else
615 qlim = NULL;
617 while (lim - end >= d)
619 if (qlim && end <= qlim)
621 end += d - 1;
622 while ((d = delta[c = *end]) && end < qlim)
624 end += d;
625 end += delta[U(*end)];
626 end += delta[U(*end)];
628 ++end;
630 else
631 d = delta[c = (end += d)[-1]];
632 if (d)
633 continue;
634 beg = end - 1;
635 trie = next[c];
636 if (trie->accepting)
638 mch = beg;
639 accept = trie;
641 d = trie->shift;
642 while (beg > text)
644 c = trans ? trans[U(*--beg)] : *--beg;
645 tree = trie->links;
646 while (tree && c != tree->label)
647 if (c < tree->label)
648 tree = tree->llink;
649 else
650 tree = tree->rlink;
651 if (tree)
653 trie = tree->trie;
654 if (trie->accepting)
656 mch = beg;
657 accept = trie;
660 else
661 break;
662 d = trie->shift;
664 if (mch)
665 goto match;
667 return -1;
669 match:
670 /* Given a known match, find the longest possible match anchored
671 at or before its starting point. This is nearly a verbatim
672 copy of the preceding main search loops. */
673 if (lim - mch > kwset->maxd)
674 lim = mch + kwset->maxd;
675 lmch = NULL;
676 d = 1;
677 while (lim - end >= d)
679 if ((d = delta[c = (end += d)[-1]]) != 0)
680 continue;
681 beg = end - 1;
682 if (!(trie = next[c]))
684 d = 1;
685 continue;
687 if (trie->accepting && beg <= mch)
689 lmch = beg;
690 accept = trie;
692 d = trie->shift;
693 while (beg > text)
695 c = trans ? trans[U(*--beg)] : *--beg;
696 tree = trie->links;
697 while (tree && c != tree->label)
698 if (c < tree->label)
699 tree = tree->llink;
700 else
701 tree = tree->rlink;
702 if (tree)
704 trie = tree->trie;
705 if (trie->accepting && beg <= mch)
707 lmch = beg;
708 accept = trie;
711 else
712 break;
713 d = trie->shift;
715 if (lmch)
717 mch = lmch;
718 goto match;
720 if (!d)
721 d = 1;
724 if (kwsmatch)
726 kwsmatch->index = accept->accepting / 2;
727 kwsmatch->offset[0] = mch - text;
728 kwsmatch->size[0] = accept->depth;
730 return mch - text;
733 /* Search through the given text for a match of any member of the
734 given keyword set. Return a pointer to the first character of
735 the matching substring, or NULL if no match is found. If FOUNDLEN
736 is non-NULL store in the referenced location the length of the
737 matching substring. Similarly, if FOUNDIDX is non-NULL, store
738 in the referenced location the index number of the particular
739 keyword matched. */
740 size_t
741 kwsexec (kwset_t kws, char const *text, size_t size,
742 struct kwsmatch *kwsmatch)
744 struct kwset const *kwset = (struct kwset *) kws;
745 if (kwset->words == 1 && kwset->trans == NULL)
747 size_t ret = bmexec (kws, text, size);
748 if (kwsmatch != NULL && ret != (size_t) -1)
750 kwsmatch->index = 0;
751 kwsmatch->offset[0] = ret;
752 kwsmatch->size[0] = kwset->mind;
754 return ret;
756 else
757 return cwexec(kws, text, size, kwsmatch);
760 /* Free the components of the given keyword set. */
761 void
762 kwsfree (kwset_t kws)
764 struct kwset *kwset;
766 kwset = (struct kwset *) kws;
767 obstack_free(&kwset->obstack, NULL);
768 free(kws);