| /* |
| * This file has been copied from commit e7ac713d^ in the GNU grep git |
| * repository. A few small changes have been made to adapt the code to |
| * Git. |
| */ |
| |
| /* kwset.c - search for any of a set of keywords. |
| Copyright 1989, 1998, 2000, 2005 Free Software Foundation, Inc. |
| |
| This program is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| This program is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with this program; if not, write to the Free Software |
| Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA |
| 02110-1301, USA. */ |
| |
| /* Written August 1989 by Mike Haertel. |
| The author may be reached (Email) at the address mike@ai.mit.edu, |
| or (US mail) as Mike Haertel c/o Free Software Foundation. */ |
| |
| /* The algorithm implemented by these routines bears a startling resemblence |
| to one discovered by Beate Commentz-Walter, although it is not identical. |
| See "A String Matching Algorithm Fast on the Average," Technical Report, |
| IBM-Germany, Scientific Center Heidelberg, Tiergartenstrasse 15, D-6900 |
| Heidelberg, Germany. See also Aho, A.V., and M. Corasick, "Efficient |
| String Matching: An Aid to Bibliographic Search," CACM June 1975, |
| Vol. 18, No. 6, which describes the failure function used below. */ |
| |
| #include "cache.h" |
| |
| #include "kwset.h" |
| #include "compat/obstack.h" |
| |
| #define NCHAR (UCHAR_MAX + 1) |
| #define obstack_chunk_alloc xmalloc |
| #define obstack_chunk_free free |
| |
| #define U(c) ((unsigned char) (c)) |
| |
| /* Balanced tree of edges and labels leaving a given trie node. */ |
| struct tree |
| { |
| struct tree *llink; /* Left link; MUST be first field. */ |
| struct tree *rlink; /* Right link (to larger labels). */ |
| struct trie *trie; /* Trie node pointed to by this edge. */ |
| unsigned char label; /* Label on this edge. */ |
| char balance; /* Difference in depths of subtrees. */ |
| }; |
| |
| /* Node of a trie representing a set of reversed keywords. */ |
| struct trie |
| { |
| unsigned int accepting; /* Word index of accepted word, or zero. */ |
| struct tree *links; /* Tree of edges leaving this node. */ |
| struct trie *parent; /* Parent of this node. */ |
| struct trie *next; /* List of all trie nodes in level order. */ |
| struct trie *fail; /* Aho-Corasick failure function. */ |
| int depth; /* Depth of this node from the root. */ |
| int shift; /* Shift function for search failures. */ |
| int maxshift; /* Max shift of self and descendents. */ |
| }; |
| |
| /* Structure returned opaquely to the caller, containing everything. */ |
| struct kwset |
| { |
| struct obstack obstack; /* Obstack for node allocation. */ |
| int words; /* Number of words in the trie. */ |
| struct trie *trie; /* The trie itself. */ |
| int mind; /* Minimum depth of an accepting node. */ |
| int maxd; /* Maximum depth of any node. */ |
| unsigned char delta[NCHAR]; /* Delta table for rapid search. */ |
| struct trie *next[NCHAR]; /* Table of children of the root. */ |
| char *target; /* Target string if there's only one. */ |
| int mind2; /* Used in Boyer-Moore search for one string. */ |
| char const *trans; /* Character translation table. */ |
| }; |
| |
| /* Allocate and initialize a keyword set object, returning an opaque |
| pointer to it. Return NULL if memory is not available. */ |
| kwset_t |
| kwsalloc (char const *trans) |
| { |
| struct kwset *kwset; |
| |
| kwset = (struct kwset *) xmalloc(sizeof (struct kwset)); |
| |
| obstack_init(&kwset->obstack); |
| kwset->words = 0; |
| kwset->trie |
| = (struct trie *) obstack_alloc(&kwset->obstack, sizeof (struct trie)); |
| if (!kwset->trie) |
| { |
| kwsfree((kwset_t) kwset); |
| return NULL; |
| } |
| kwset->trie->accepting = 0; |
| kwset->trie->links = NULL; |
| kwset->trie->parent = NULL; |
| kwset->trie->next = NULL; |
| kwset->trie->fail = NULL; |
| kwset->trie->depth = 0; |
| kwset->trie->shift = 0; |
| kwset->mind = INT_MAX; |
| kwset->maxd = -1; |
| kwset->target = NULL; |
| kwset->trans = trans; |
| |
| return (kwset_t) kwset; |
| } |
| |
| /* This upper bound is valid for CHAR_BIT >= 4 and |
| exact for CHAR_BIT in { 4..11, 13, 15, 17, 19 }. */ |
| #define DEPTH_SIZE (CHAR_BIT + CHAR_BIT/2) |
| |
| /* Add the given string to the contents of the keyword set. Return NULL |
| for success, an error message otherwise. */ |
| const char * |
| kwsincr (kwset_t kws, char const *text, size_t len) |
| { |
| struct kwset *kwset; |
| register struct trie *trie; |
| register unsigned char label; |
| register struct tree *link; |
| register int depth; |
| struct tree *links[DEPTH_SIZE]; |
| enum { L, R } dirs[DEPTH_SIZE]; |
| struct tree *t, *r, *l, *rl, *lr; |
| |
| kwset = (struct kwset *) kws; |
| trie = kwset->trie; |
| text += len; |
| |
| /* Descend the trie (built of reversed keywords) character-by-character, |
| installing new nodes when necessary. */ |
| while (len--) |
| { |
| label = kwset->trans ? kwset->trans[U(*--text)] : *--text; |
| |
| /* Descend the tree of outgoing links for this trie node, |
| looking for the current character and keeping track |
| of the path followed. */ |
| link = trie->links; |
| links[0] = (struct tree *) &trie->links; |
| dirs[0] = L; |
| depth = 1; |
| |
| while (link && label != link->label) |
| { |
| links[depth] = link; |
| if (label < link->label) |
| dirs[depth++] = L, link = link->llink; |
| else |
| dirs[depth++] = R, link = link->rlink; |
| } |
| |
| /* The current character doesn't have an outgoing link at |
| this trie node, so build a new trie node and install |
| a link in the current trie node's tree. */ |
| if (!link) |
| { |
| link = (struct tree *) obstack_alloc(&kwset->obstack, |
| sizeof (struct tree)); |
| if (!link) |
| return "memory exhausted"; |
| link->llink = NULL; |
| link->rlink = NULL; |
| link->trie = (struct trie *) obstack_alloc(&kwset->obstack, |
| sizeof (struct trie)); |
| if (!link->trie) |
| { |
| obstack_free(&kwset->obstack, link); |
| return "memory exhausted"; |
| } |
| link->trie->accepting = 0; |
| link->trie->links = NULL; |
| link->trie->parent = trie; |
| link->trie->next = NULL; |
| link->trie->fail = NULL; |
| link->trie->depth = trie->depth + 1; |
| link->trie->shift = 0; |
| link->label = label; |
| link->balance = 0; |
| |
| /* Install the new tree node in its parent. */ |
| if (dirs[--depth] == L) |
| links[depth]->llink = link; |
| else |
| links[depth]->rlink = link; |
| |
| /* Back up the tree fixing the balance flags. */ |
| while (depth && !links[depth]->balance) |
| { |
| if (dirs[depth] == L) |
| --links[depth]->balance; |
| else |
| ++links[depth]->balance; |
| --depth; |
| } |
| |
| /* Rebalance the tree by pointer rotations if necessary. */ |
| if (depth && ((dirs[depth] == L && --links[depth]->balance) |
| || (dirs[depth] == R && ++links[depth]->balance))) |
| { |
| switch (links[depth]->balance) |
| { |
| case (char) -2: |
| switch (dirs[depth + 1]) |
| { |
| case L: |
| r = links[depth], t = r->llink, rl = t->rlink; |
| t->rlink = r, r->llink = rl; |
| t->balance = r->balance = 0; |
| break; |
| case R: |
| r = links[depth], l = r->llink, t = l->rlink; |
| rl = t->rlink, lr = t->llink; |
| t->llink = l, l->rlink = lr, t->rlink = r, r->llink = rl; |
| l->balance = t->balance != 1 ? 0 : -1; |
| r->balance = t->balance != (char) -1 ? 0 : 1; |
| t->balance = 0; |
| break; |
| default: |
| abort (); |
| } |
| break; |
| case 2: |
| switch (dirs[depth + 1]) |
| { |
| case R: |
| l = links[depth], t = l->rlink, lr = t->llink; |
| t->llink = l, l->rlink = lr; |
| t->balance = l->balance = 0; |
| break; |
| case L: |
| l = links[depth], r = l->rlink, t = r->llink; |
| lr = t->llink, rl = t->rlink; |
| t->llink = l, l->rlink = lr, t->rlink = r, r->llink = rl; |
| l->balance = t->balance != 1 ? 0 : -1; |
| r->balance = t->balance != (char) -1 ? 0 : 1; |
| t->balance = 0; |
| break; |
| default: |
| abort (); |
| } |
| break; |
| default: |
| abort (); |
| } |
| |
| if (dirs[depth - 1] == L) |
| links[depth - 1]->llink = t; |
| else |
| links[depth - 1]->rlink = t; |
| } |
| } |
| |
| trie = link->trie; |
| } |
| |
| /* Mark the node we finally reached as accepting, encoding the |
| index number of this word in the keyword set so far. */ |
| if (!trie->accepting) |
| trie->accepting = 1 + 2 * kwset->words; |
| ++kwset->words; |
| |
| /* Keep track of the longest and shortest string of the keyword set. */ |
| if (trie->depth < kwset->mind) |
| kwset->mind = trie->depth; |
| if (trie->depth > kwset->maxd) |
| kwset->maxd = trie->depth; |
| |
| return NULL; |
| } |
| |
| /* Enqueue the trie nodes referenced from the given tree in the |
| given queue. */ |
| static void |
| enqueue (struct tree *tree, struct trie **last) |
| { |
| if (!tree) |
| return; |
| enqueue(tree->llink, last); |
| enqueue(tree->rlink, last); |
| (*last) = (*last)->next = tree->trie; |
| } |
| |
| /* Compute the Aho-Corasick failure function for the trie nodes referenced |
| from the given tree, given the failure function for their parent as |
| well as a last resort failure node. */ |
| static void |
| treefails (register struct tree const *tree, struct trie const *fail, |
| struct trie *recourse) |
| { |
| register struct tree *link; |
| |
| if (!tree) |
| return; |
| |
| treefails(tree->llink, fail, recourse); |
| treefails(tree->rlink, fail, recourse); |
| |
| /* Find, in the chain of fails going back to the root, the first |
| node that has a descendent on the current label. */ |
| while (fail) |
| { |
| link = fail->links; |
| while (link && tree->label != link->label) |
| if (tree->label < link->label) |
| link = link->llink; |
| else |
| link = link->rlink; |
| if (link) |
| { |
| tree->trie->fail = link->trie; |
| return; |
| } |
| fail = fail->fail; |
| } |
| |
| tree->trie->fail = recourse; |
| } |
| |
| /* Set delta entries for the links of the given tree such that |
| the preexisting delta value is larger than the current depth. */ |
| static void |
| treedelta (register struct tree const *tree, |
| register unsigned int depth, |
| unsigned char delta[]) |
| { |
| if (!tree) |
| return; |
| treedelta(tree->llink, depth, delta); |
| treedelta(tree->rlink, depth, delta); |
| if (depth < delta[tree->label]) |
| delta[tree->label] = depth; |
| } |
| |
| /* Return true if A has every label in B. */ |
| static int |
| hasevery (register struct tree const *a, register struct tree const *b) |
| { |
| if (!b) |
| return 1; |
| if (!hasevery(a, b->llink)) |
| return 0; |
| if (!hasevery(a, b->rlink)) |
| return 0; |
| while (a && b->label != a->label) |
| if (b->label < a->label) |
| a = a->llink; |
| else |
| a = a->rlink; |
| return !!a; |
| } |
| |
| /* Compute a vector, indexed by character code, of the trie nodes |
| referenced from the given tree. */ |
| static void |
| treenext (struct tree const *tree, struct trie *next[]) |
| { |
| if (!tree) |
| return; |
| treenext(tree->llink, next); |
| treenext(tree->rlink, next); |
| next[tree->label] = tree->trie; |
| } |
| |
| /* Compute the shift for each trie node, as well as the delta |
| table and next cache for the given keyword set. */ |
| const char * |
| kwsprep (kwset_t kws) |
| { |
| register struct kwset *kwset; |
| register int i; |
| register struct trie *curr; |
| register char const *trans; |
| unsigned char delta[NCHAR]; |
| |
| kwset = (struct kwset *) kws; |
| |
| /* Initial values for the delta table; will be changed later. The |
| delta entry for a given character is the smallest depth of any |
| node at which an outgoing edge is labeled by that character. */ |
| memset(delta, kwset->mind < UCHAR_MAX ? kwset->mind : UCHAR_MAX, NCHAR); |
| |
| /* Check if we can use the simple boyer-moore algorithm, instead |
| of the hairy commentz-walter algorithm. */ |
| if (kwset->words == 1 && kwset->trans == NULL) |
| { |
| char c; |
| |
| /* Looking for just one string. Extract it from the trie. */ |
| kwset->target = obstack_alloc(&kwset->obstack, kwset->mind); |
| if (!kwset->target) |
| return "memory exhausted"; |
| for (i = kwset->mind - 1, curr = kwset->trie; i >= 0; --i) |
| { |
| kwset->target[i] = curr->links->label; |
| curr = curr->links->trie; |
| } |
| /* Build the Boyer Moore delta. Boy that's easy compared to CW. */ |
| for (i = 0; i < kwset->mind; ++i) |
| delta[U(kwset->target[i])] = kwset->mind - (i + 1); |
| /* Find the minimal delta2 shift that we might make after |
| a backwards match has failed. */ |
| c = kwset->target[kwset->mind - 1]; |
| for (i = kwset->mind - 2; i >= 0; --i) |
| if (kwset->target[i] == c) |
| break; |
| kwset->mind2 = kwset->mind - (i + 1); |
| } |
| else |
| { |
| register struct trie *fail; |
| struct trie *last, *next[NCHAR]; |
| |
| /* Traverse the nodes of the trie in level order, simultaneously |
| computing the delta table, failure function, and shift function. */ |
| for (curr = last = kwset->trie; curr; curr = curr->next) |
| { |
| /* Enqueue the immediate descendents in the level order queue. */ |
| enqueue(curr->links, &last); |
| |
| curr->shift = kwset->mind; |
| curr->maxshift = kwset->mind; |
| |
| /* Update the delta table for the descendents of this node. */ |
| treedelta(curr->links, curr->depth, delta); |
| |
| /* Compute the failure function for the decendents of this node. */ |
| treefails(curr->links, curr->fail, kwset->trie); |
| |
| /* Update the shifts at each node in the current node's chain |
| of fails back to the root. */ |
| for (fail = curr->fail; fail; fail = fail->fail) |
| { |
| /* If the current node has some outgoing edge that the fail |
| doesn't, then the shift at the fail should be no larger |
| than the difference of their depths. */ |
| if (!hasevery(fail->links, curr->links)) |
| if (curr->depth - fail->depth < fail->shift) |
| fail->shift = curr->depth - fail->depth; |
| |
| /* If the current node is accepting then the shift at the |
| fail and its descendents should be no larger than the |
| difference of their depths. */ |
| if (curr->accepting && fail->maxshift > curr->depth - fail->depth) |
| fail->maxshift = curr->depth - fail->depth; |
| } |
| } |
| |
| /* Traverse the trie in level order again, fixing up all nodes whose |
| shift exceeds their inherited maxshift. */ |
| for (curr = kwset->trie->next; curr; curr = curr->next) |
| { |
| if (curr->maxshift > curr->parent->maxshift) |
| curr->maxshift = curr->parent->maxshift; |
| if (curr->shift > curr->maxshift) |
| curr->shift = curr->maxshift; |
| } |
| |
| /* Create a vector, indexed by character code, of the outgoing links |
| from the root node. */ |
| for (i = 0; i < NCHAR; ++i) |
| next[i] = NULL; |
| treenext(kwset->trie->links, next); |
| |
| if ((trans = kwset->trans) != NULL) |
| for (i = 0; i < NCHAR; ++i) |
| kwset->next[i] = next[U(trans[i])]; |
| else |
| memcpy(kwset->next, next, NCHAR * sizeof(struct trie *)); |
| } |
| |
| /* Fix things up for any translation table. */ |
| if ((trans = kwset->trans) != NULL) |
| for (i = 0; i < NCHAR; ++i) |
| kwset->delta[i] = delta[U(trans[i])]; |
| else |
| memcpy(kwset->delta, delta, NCHAR); |
| |
| return NULL; |
| } |
| |
| /* Fast boyer-moore search. */ |
| static size_t |
| bmexec (kwset_t kws, char const *text, size_t size) |
| { |
| struct kwset const *kwset; |
| register unsigned char const *d1; |
| register char const *ep, *sp, *tp; |
| register int d, gc, i, len, md2; |
| |
| kwset = (struct kwset const *) kws; |
| len = kwset->mind; |
| |
| if (len == 0) |
| return 0; |
| if (len > size) |
| return -1; |
| if (len == 1) |
| { |
| tp = memchr (text, kwset->target[0], size); |
| return tp ? tp - text : -1; |
| } |
| |
| d1 = kwset->delta; |
| sp = kwset->target + len; |
| gc = U(sp[-2]); |
| md2 = kwset->mind2; |
| tp = text + len; |
| |
| /* Significance of 12: 1 (initial offset) + 10 (skip loop) + 1 (md2). */ |
| if (size > 12 * len) |
| /* 11 is not a bug, the initial offset happens only once. */ |
| for (ep = text + size - 11 * len;;) |
| { |
| while (tp <= ep) |
| { |
| d = d1[U(tp[-1])], tp += d; |
| d = d1[U(tp[-1])], tp += d; |
| if (d == 0) |
| goto found; |
| d = d1[U(tp[-1])], tp += d; |
| d = d1[U(tp[-1])], tp += d; |
| d = d1[U(tp[-1])], tp += d; |
| if (d == 0) |
| goto found; |
| d = d1[U(tp[-1])], tp += d; |
| d = d1[U(tp[-1])], tp += d; |
| d = d1[U(tp[-1])], tp += d; |
| if (d == 0) |
| goto found; |
| d = d1[U(tp[-1])], tp += d; |
| d = d1[U(tp[-1])], tp += d; |
| } |
| break; |
| found: |
| if (U(tp[-2]) == gc) |
| { |
| for (i = 3; i <= len && U(tp[-i]) == U(sp[-i]); ++i) |
| ; |
| if (i > len) |
| return tp - len - text; |
| } |
| tp += md2; |
| } |
| |
| /* Now we have only a few characters left to search. We |
| carefully avoid ever producing an out-of-bounds pointer. */ |
| ep = text + size; |
| d = d1[U(tp[-1])]; |
| while (d <= ep - tp) |
| { |
| d = d1[U((tp += d)[-1])]; |
| if (d != 0) |
| continue; |
| if (U(tp[-2]) == gc) |
| { |
| for (i = 3; i <= len && U(tp[-i]) == U(sp[-i]); ++i) |
| ; |
| if (i > len) |
| return tp - len - text; |
| } |
| d = md2; |
| } |
| |
| return -1; |
| } |
| |
| /* Hairy multiple string search. */ |
| static size_t |
| cwexec (kwset_t kws, char const *text, size_t len, struct kwsmatch *kwsmatch) |
| { |
| struct kwset const *kwset; |
| struct trie * const *next; |
| struct trie const *trie; |
| struct trie const *accept; |
| char const *beg, *lim, *mch, *lmch; |
| register unsigned char c; |
| register unsigned char const *delta; |
| register int d; |
| register char const *end, *qlim; |
| register struct tree const *tree; |
| register char const *trans; |
| |
| accept = NULL; |
| |
| /* Initialize register copies and look for easy ways out. */ |
| kwset = (struct kwset *) kws; |
| if (len < kwset->mind) |
| return -1; |
| next = kwset->next; |
| delta = kwset->delta; |
| trans = kwset->trans; |
| lim = text + len; |
| end = text; |
| if ((d = kwset->mind) != 0) |
| mch = NULL; |
| else |
| { |
| mch = text, accept = kwset->trie; |
| goto match; |
| } |
| |
| if (len >= 4 * kwset->mind) |
| qlim = lim - 4 * kwset->mind; |
| else |
| qlim = NULL; |
| |
| while (lim - end >= d) |
| { |
| if (qlim && end <= qlim) |
| { |
| end += d - 1; |
| while ((d = delta[c = *end]) && end < qlim) |
| { |
| end += d; |
| end += delta[U(*end)]; |
| end += delta[U(*end)]; |
| } |
| ++end; |
| } |
| else |
| d = delta[c = (end += d)[-1]]; |
| if (d) |
| continue; |
| beg = end - 1; |
| trie = next[c]; |
| if (trie->accepting) |
| { |
| mch = beg; |
| accept = trie; |
| } |
| d = trie->shift; |
| while (beg > text) |
| { |
| c = trans ? trans[U(*--beg)] : *--beg; |
| tree = trie->links; |
| while (tree && c != tree->label) |
| if (c < tree->label) |
| tree = tree->llink; |
| else |
| tree = tree->rlink; |
| if (tree) |
| { |
| trie = tree->trie; |
| if (trie->accepting) |
| { |
| mch = beg; |
| accept = trie; |
| } |
| } |
| else |
| break; |
| d = trie->shift; |
| } |
| if (mch) |
| goto match; |
| } |
| return -1; |
| |
| match: |
| /* Given a known match, find the longest possible match anchored |
| at or before its starting point. This is nearly a verbatim |
| copy of the preceding main search loops. */ |
| if (lim - mch > kwset->maxd) |
| lim = mch + kwset->maxd; |
| lmch = 0; |
| d = 1; |
| while (lim - end >= d) |
| { |
| if ((d = delta[c = (end += d)[-1]]) != 0) |
| continue; |
| beg = end - 1; |
| if (!(trie = next[c])) |
| { |
| d = 1; |
| continue; |
| } |
| if (trie->accepting && beg <= mch) |
| { |
| lmch = beg; |
| accept = trie; |
| } |
| d = trie->shift; |
| while (beg > text) |
| { |
| c = trans ? trans[U(*--beg)] : *--beg; |
| tree = trie->links; |
| while (tree && c != tree->label) |
| if (c < tree->label) |
| tree = tree->llink; |
| else |
| tree = tree->rlink; |
| if (tree) |
| { |
| trie = tree->trie; |
| if (trie->accepting && beg <= mch) |
| { |
| lmch = beg; |
| accept = trie; |
| } |
| } |
| else |
| break; |
| d = trie->shift; |
| } |
| if (lmch) |
| { |
| mch = lmch; |
| goto match; |
| } |
| if (!d) |
| d = 1; |
| } |
| |
| if (kwsmatch) |
| { |
| kwsmatch->index = accept->accepting / 2; |
| kwsmatch->offset[0] = mch - text; |
| kwsmatch->size[0] = accept->depth; |
| } |
| return mch - text; |
| } |
| |
| /* Search through the given text for a match of any member of the |
| given keyword set. Return a pointer to the first character of |
| the matching substring, or NULL if no match is found. If FOUNDLEN |
| is non-NULL store in the referenced location the length of the |
| matching substring. Similarly, if FOUNDIDX is non-NULL, store |
| in the referenced location the index number of the particular |
| keyword matched. */ |
| size_t |
| kwsexec (kwset_t kws, char const *text, size_t size, |
| struct kwsmatch *kwsmatch) |
| { |
| struct kwset const *kwset = (struct kwset *) kws; |
| if (kwset->words == 1 && kwset->trans == NULL) |
| { |
| size_t ret = bmexec (kws, text, size); |
| if (kwsmatch != NULL && ret != (size_t) -1) |
| { |
| kwsmatch->index = 0; |
| kwsmatch->offset[0] = ret; |
| kwsmatch->size[0] = kwset->mind; |
| } |
| return ret; |
| } |
| else |
| return cwexec(kws, text, size, kwsmatch); |
| } |
| |
| /* Free the components of the given keyword set. */ |
| void |
| kwsfree (kwset_t kws) |
| { |
| struct kwset *kwset; |
| |
| kwset = (struct kwset *) kws; |
| obstack_free(&kwset->obstack, NULL); |
| free(kws); |
| } |