Merge branch 'esr/maint-doc-fast-import'
[git.git] / kwset.c
blob51b2ab6c7e61413851a958f7a4009a0194744b68
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, write to the Free Software
22 Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA
23 02110-1301, USA. */
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. */
29 /* The algorithm implemented by these routines bears a startling resemblence
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. */
37 #include "cache.h"
39 #include "kwset.h"
40 #include "compat/obstack.h"
42 #define NCHAR (UCHAR_MAX + 1)
43 #define obstack_chunk_alloc xmalloc
44 #define obstack_chunk_free free
46 #define U(c) ((unsigned char) (c))
48 /* Balanced tree of edges and labels leaving a given trie node. */
49 struct tree
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. */
58 /* Node of a trie representing a set of reversed keywords. */
59 struct trie
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 descendents. */
71 /* Structure returned opaquely to the caller, containing everything. */
72 struct kwset
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 char const *trans; /* Character translation table. */
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 (char const *trans)
91 struct kwset *kwset;
93 kwset = (struct kwset *) xmalloc(sizeof (struct kwset));
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)
101 kwsfree((kwset_t) kwset);
102 return NULL;
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;
116 return (kwset_t) kwset;
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)
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)
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;
137 kwset = (struct kwset *) kws;
138 trie = kwset->trie;
139 text += len;
141 /* Descend the trie (built of reversed keywords) character-by-character,
142 installing new nodes when necessary. */
143 while (len--)
145 label = kwset->trans ? kwset->trans[U(*--text)] : *--text;
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;
155 while (link && label != link->label)
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;
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)
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)
179 obstack_free(&kwset->obstack, link);
180 return "memory exhausted";
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;
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;
198 /* Back up the tree fixing the balance flags. */
199 while (depth && !links[depth]->balance)
201 if (dirs[depth] == L)
202 --links[depth]->balance;
203 else
204 ++links[depth]->balance;
205 --depth;
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)))
212 switch (links[depth]->balance)
214 case (char) -2:
215 switch (dirs[depth + 1])
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 ();
233 break;
234 case 2:
235 switch (dirs[depth + 1])
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 ();
253 break;
254 default:
255 abort ();
258 if (dirs[depth - 1] == L)
259 links[depth - 1]->llink = t;
260 else
261 links[depth - 1]->rlink = t;
265 trie = link->trie;
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;
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;
280 return NULL;
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)
288 if (!tree)
289 return;
290 enqueue(tree->llink, last);
291 enqueue(tree->rlink, last);
292 (*last) = (*last)->next = tree->trie;
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)
302 register struct tree *link;
304 if (!tree)
305 return;
307 treefails(tree->llink, fail, recourse);
308 treefails(tree->rlink, fail, recourse);
310 /* Find, in the chain of fails going back to the root, the first
311 node that has a descendent on the current label. */
312 while (fail)
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)
322 tree->trie->fail = link->trie;
323 return;
325 fail = fail->fail;
328 tree->trie->fail = recourse;
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[])
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;
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)
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;
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[])
369 if (!tree)
370 return;
371 treenext(tree->llink, next);
372 treenext(tree->rlink, next);
373 next[tree->label] = tree->trie;
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)
381 register struct kwset *kwset;
382 register int i;
383 register struct trie *curr;
384 register char const *trans;
385 unsigned char delta[NCHAR];
387 kwset = (struct kwset *) kws;
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);
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)
398 char c;
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)
406 kwset->target[i] = curr->links->label;
407 curr = curr->links->trie;
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);
420 else
422 register struct trie *fail;
423 struct trie *last, *next[NCHAR];
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)
429 /* Enqueue the immediate descendents in the level order queue. */
430 enqueue(curr->links, &last);
432 curr->shift = kwset->mind;
433 curr->maxshift = kwset->mind;
435 /* Update the delta table for the descendents of this node. */
436 treedelta(curr->links, curr->depth, delta);
438 /* Compute the failure function for the decendents of this node. */
439 treefails(curr->links, curr->fail, kwset->trie);
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)
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;
452 /* If the current node is accepting then the shift at the
453 fail and its descendents 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;
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)
464 if (curr->maxshift > curr->parent->maxshift)
465 curr->maxshift = curr->parent->maxshift;
466 if (curr->shift > curr->maxshift)
467 curr->shift = curr->maxshift;
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);
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 *));
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);
490 return NULL;
493 /* Fast boyer-moore search. */
494 static size_t
495 bmexec (kwset_t kws, char const *text, size_t size)
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;
502 kwset = (struct kwset const *) kws;
503 len = kwset->mind;
505 if (len == 0)
506 return 0;
507 if (len > size)
508 return -1;
509 if (len == 1)
511 tp = memchr (text, kwset->target[0], size);
512 return tp ? tp - text : -1;
515 d1 = kwset->delta;
516 sp = kwset->target + len;
517 gc = U(sp[-2]);
518 md2 = kwset->mind2;
519 tp = text + len;
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;;)
526 while (tp <= ep)
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;
545 break;
546 found:
547 if (U(tp[-2]) == gc)
549 for (i = 3; i <= len && U(tp[-i]) == U(sp[-i]); ++i)
551 if (i > len)
552 return tp - len - text;
554 tp += md2;
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)
563 d = d1[U((tp += d)[-1])];
564 if (d != 0)
565 continue;
566 if (U(tp[-2]) == gc)
568 for (i = 3; i <= len && U(tp[-i]) == U(sp[-i]); ++i)
570 if (i > len)
571 return tp - len - text;
573 d = md2;
576 return -1;
579 /* Hairy multiple string search. */
580 static size_t
581 cwexec (kwset_t kws, char const *text, size_t len, struct kwsmatch *kwsmatch)
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 char const *trans;
595 accept = NULL;
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
610 mch = text, accept = kwset->trie;
611 goto match;
614 if (len >= 4 * kwset->mind)
615 qlim = lim - 4 * kwset->mind;
616 else
617 qlim = NULL;
619 while (lim - end >= d)
621 if (qlim && end <= qlim)
623 end += d - 1;
624 while ((d = delta[c = *end]) && end < qlim)
626 end += d;
627 end += delta[U(*end)];
628 end += delta[U(*end)];
630 ++end;
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)
640 mch = beg;
641 accept = trie;
643 d = trie->shift;
644 while (beg > text)
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)
655 trie = tree->trie;
656 if (trie->accepting)
658 mch = beg;
659 accept = trie;
662 else
663 break;
664 d = trie->shift;
666 if (mch)
667 goto match;
669 return -1;
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)
681 if ((d = delta[c = (end += d)[-1]]) != 0)
682 continue;
683 beg = end - 1;
684 if (!(trie = next[c]))
686 d = 1;
687 continue;
689 if (trie->accepting && beg <= mch)
691 lmch = beg;
692 accept = trie;
694 d = trie->shift;
695 while (beg > text)
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)
706 trie = tree->trie;
707 if (trie->accepting && beg <= mch)
709 lmch = beg;
710 accept = trie;
713 else
714 break;
715 d = trie->shift;
717 if (lmch)
719 mch = lmch;
720 goto match;
722 if (!d)
723 d = 1;
726 if (kwsmatch)
728 kwsmatch->index = accept->accepting / 2;
729 kwsmatch->offset[0] = mch - text;
730 kwsmatch->size[0] = accept->depth;
732 return mch - text;
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)
746 struct kwset const *kwset = (struct kwset *) kws;
747 if (kwset->words == 1 && kwset->trans == NULL)
749 size_t ret = bmexec (kws, text, size);
750 if (kwsmatch != NULL && ret != (size_t) -1)
752 kwsmatch->index = 0;
753 kwsmatch->offset[0] = ret;
754 kwsmatch->size[0] = kwset->mind;
756 return ret;
758 else
759 return cwexec(kws, text, size, kwsmatch);
762 /* Free the components of the given keyword set. */
763 void
764 kwsfree (kwset_t kws)
766 struct kwset *kwset;
768 kwset = (struct kwset *) kws;
769 obstack_free(&kwset->obstack, NULL);
770 free(kws);