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Diffstat (limited to 'kwset.c')
| -rw-r--r-- | kwset.c | 778 |
1 files changed, 778 insertions, 0 deletions
diff --git a/kwset.c b/kwset.c new file mode 100644 index 0000000000..e66193b95f --- /dev/null +++ b/kwset.c @@ -0,0 +1,778 @@ +/* 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. */ + +#ifdef HAVE_CONFIG_H +# include <config.h> +#endif +#include <sys/types.h> +#include "system.h" +#include "kwset.h" +#include "obstack.h" + +#ifdef GREP +extern char *xmalloc(); +# undef malloc +# define malloc xmalloc +#endif + +#define NCHAR (UCHAR_MAX + 1) +#define obstack_chunk_alloc malloc +#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 *) malloc(sizeof (struct kwset)); + if (!kwset) + return NULL; + + 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; + +#ifdef lint + accept = NULL; +#endif + + /* 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); +} |