776 lines
21 KiB
C
776 lines
21 KiB
C
/* kwset.c - search for any of a set of keywords.
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Copyright (C) 1989, 1998 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
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02111-1307, USA. */
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/* Written August 1989 by Mike Haertel.
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The author may be reached (Email) at the address mike@ai.mit.edu,
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or (US mail) as Mike Haertel c/o Free Software Foundation. */
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/* The algorithm implemented by these routines bears a startling resemblence
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to one discovered by Beate Commentz-Walter, although it is not identical.
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See "A String Matching Algorithm Fast on the Average," Technical Report,
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IBM-Germany, Scientific Center Heidelberg, Tiergartenstrasse 15, D-6900
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Heidelberg, Germany. See also Aho, A.V., and M. Corasick, "Efficient
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String Matching: An Aid to Bibliographic Search," CACM June 1975,
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Vol. 18, No. 6, which describes the failure function used below. */
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include <sys/types.h>
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#include "system.h"
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#include "kwset.h"
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#include "obstack.h"
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#ifdef GREP
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extern char *xmalloc();
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# undef malloc
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# define malloc xmalloc
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#endif
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#define NCHAR (UCHAR_MAX + 1)
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#define obstack_chunk_alloc malloc
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#define obstack_chunk_free free
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/* Balanced tree of edges and labels leaving a given trie node. */
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struct tree
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{
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struct tree *llink; /* Left link; MUST be first field. */
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struct tree *rlink; /* Right link (to larger labels). */
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struct trie *trie; /* Trie node pointed to by this edge. */
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unsigned char label; /* Label on this edge. */
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char balance; /* Difference in depths of subtrees. */
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};
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/* Node of a trie representing a set of reversed keywords. */
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struct trie
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{
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unsigned int accepting; /* Word index of accepted word, or zero. */
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struct tree *links; /* Tree of edges leaving this node. */
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struct trie *parent; /* Parent of this node. */
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struct trie *next; /* List of all trie nodes in level order. */
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struct trie *fail; /* Aho-Corasick failure function. */
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int depth; /* Depth of this node from the root. */
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int shift; /* Shift function for search failures. */
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int maxshift; /* Max shift of self and descendents. */
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};
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/* Structure returned opaquely to the caller, containing everything. */
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struct kwset
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{
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struct obstack obstack; /* Obstack for node allocation. */
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int words; /* Number of words in the trie. */
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struct trie *trie; /* The trie itself. */
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int mind; /* Minimum depth of an accepting node. */
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int maxd; /* Maximum depth of any node. */
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unsigned char delta[NCHAR]; /* Delta table for rapid search. */
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struct trie *next[NCHAR]; /* Table of children of the root. */
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char *target; /* Target string if there's only one. */
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int mind2; /* Used in Boyer-Moore search for one string. */
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char *trans; /* Character translation table. */
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};
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/* prototypes */
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static void enqueue PARAMS((struct tree *, struct trie **));
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static void treefails PARAMS((register struct tree *, struct trie *, struct trie *));
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static void treedelta PARAMS((register struct tree *,register unsigned int, unsigned char *));
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static int hasevery PARAMS((register struct tree *, register struct tree *));
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static void treenext PARAMS((struct tree *, struct trie **));
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static char * bmexec PARAMS((kwset_t, char *, size_t));
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static char * cwexec PARAMS((kwset_t, char *, size_t, struct kwsmatch *));
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/* Allocate and initialize a keyword set object, returning an opaque
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pointer to it. Return NULL if memory is not available. */
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kwset_t
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kwsalloc (char *trans)
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{
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struct kwset *kwset;
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kwset = (struct kwset *) malloc(sizeof (struct kwset));
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if (!kwset)
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return 0;
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obstack_init(&kwset->obstack);
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kwset->words = 0;
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kwset->trie
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= (struct trie *) obstack_alloc(&kwset->obstack, sizeof (struct trie));
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if (!kwset->trie)
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{
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kwsfree((kwset_t) kwset);
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return 0;
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}
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kwset->trie->accepting = 0;
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kwset->trie->links = 0;
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kwset->trie->parent = 0;
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kwset->trie->next = 0;
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kwset->trie->fail = 0;
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kwset->trie->depth = 0;
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kwset->trie->shift = 0;
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kwset->mind = INT_MAX;
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kwset->maxd = -1;
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kwset->target = 0;
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kwset->trans = trans;
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return (kwset_t) kwset;
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}
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/* Add the given string to the contents of the keyword set. Return NULL
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for success, an error message otherwise. */
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char *
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kwsincr (kwset_t kws, char *text, size_t len)
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{
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struct kwset *kwset;
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register struct trie *trie;
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register unsigned char label;
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register struct tree *link;
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register int depth;
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struct tree *links[12];
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enum { L, R } dirs[12];
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struct tree *t, *r, *l, *rl, *lr;
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kwset = (struct kwset *) kws;
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trie = kwset->trie;
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text += len;
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/* Descend the trie (built of reversed keywords) character-by-character,
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installing new nodes when necessary. */
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while (len--)
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{
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label = kwset->trans ? kwset->trans[(unsigned char) *--text] : *--text;
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/* Descend the tree of outgoing links for this trie node,
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looking for the current character and keeping track
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of the path followed. */
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link = trie->links;
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links[0] = (struct tree *) &trie->links;
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dirs[0] = L;
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depth = 1;
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while (link && label != link->label)
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{
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links[depth] = link;
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if (label < link->label)
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dirs[depth++] = L, link = link->llink;
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else
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dirs[depth++] = R, link = link->rlink;
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}
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/* The current character doesn't have an outgoing link at
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this trie node, so build a new trie node and install
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a link in the current trie node's tree. */
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if (!link)
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{
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link = (struct tree *) obstack_alloc(&kwset->obstack,
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sizeof (struct tree));
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if (!link)
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return _("memory exhausted");
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link->llink = 0;
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link->rlink = 0;
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link->trie = (struct trie *) obstack_alloc(&kwset->obstack,
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sizeof (struct trie));
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if (!link->trie)
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return _("memory exhausted");
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link->trie->accepting = 0;
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link->trie->links = 0;
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link->trie->parent = trie;
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link->trie->next = 0;
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link->trie->fail = 0;
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link->trie->depth = trie->depth + 1;
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link->trie->shift = 0;
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link->label = label;
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link->balance = 0;
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/* Install the new tree node in its parent. */
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if (dirs[--depth] == L)
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links[depth]->llink = link;
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else
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links[depth]->rlink = link;
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/* Back up the tree fixing the balance flags. */
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while (depth && !links[depth]->balance)
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{
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if (dirs[depth] == L)
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--links[depth]->balance;
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else
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++links[depth]->balance;
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--depth;
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}
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/* Rebalance the tree by pointer rotations if necessary. */
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if (depth && ((dirs[depth] == L && --links[depth]->balance)
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|| (dirs[depth] == R && ++links[depth]->balance)))
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{
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switch (links[depth]->balance)
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{
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case (char) -2:
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switch (dirs[depth + 1])
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{
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case L:
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r = links[depth], t = r->llink, rl = t->rlink;
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t->rlink = r, r->llink = rl;
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t->balance = r->balance = 0;
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break;
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case R:
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r = links[depth], l = r->llink, t = l->rlink;
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rl = t->rlink, lr = t->llink;
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t->llink = l, l->rlink = lr, t->rlink = r, r->llink = rl;
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l->balance = t->balance != 1 ? 0 : -1;
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r->balance = t->balance != (char) -1 ? 0 : 1;
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t->balance = 0;
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break;
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default:
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abort ();
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}
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break;
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case 2:
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switch (dirs[depth + 1])
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{
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case R:
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l = links[depth], t = l->rlink, lr = t->llink;
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t->llink = l, l->rlink = lr;
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t->balance = l->balance = 0;
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break;
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case L:
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l = links[depth], r = l->rlink, t = r->llink;
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lr = t->llink, rl = t->rlink;
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t->llink = l, l->rlink = lr, t->rlink = r, r->llink = rl;
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l->balance = t->balance != 1 ? 0 : -1;
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r->balance = t->balance != (char) -1 ? 0 : 1;
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t->balance = 0;
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break;
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default:
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abort ();
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}
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break;
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default:
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abort ();
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}
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if (dirs[depth - 1] == L)
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links[depth - 1]->llink = t;
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else
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links[depth - 1]->rlink = t;
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}
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}
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trie = link->trie;
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}
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/* Mark the node we finally reached as accepting, encoding the
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index number of this word in the keyword set so far. */
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if (!trie->accepting)
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trie->accepting = 1 + 2 * kwset->words;
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++kwset->words;
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/* Keep track of the longest and shortest string of the keyword set. */
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if (trie->depth < kwset->mind)
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kwset->mind = trie->depth;
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if (trie->depth > kwset->maxd)
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kwset->maxd = trie->depth;
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return 0;
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}
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/* Enqueue the trie nodes referenced from the given tree in the
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given queue. */
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static void
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enqueue (struct tree *tree, struct trie **last)
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{
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if (!tree)
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return;
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enqueue(tree->llink, last);
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enqueue(tree->rlink, last);
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(*last) = (*last)->next = tree->trie;
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}
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/* Compute the Aho-Corasick failure function for the trie nodes referenced
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from the given tree, given the failure function for their parent as
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well as a last resort failure node. */
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static void
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treefails (register struct tree *tree, struct trie *fail, struct trie *recourse)
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{
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register struct tree *link;
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if (!tree)
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return;
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treefails(tree->llink, fail, recourse);
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treefails(tree->rlink, fail, recourse);
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/* Find, in the chain of fails going back to the root, the first
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node that has a descendent on the current label. */
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while (fail)
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{
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link = fail->links;
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while (link && tree->label != link->label)
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if (tree->label < link->label)
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link = link->llink;
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else
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link = link->rlink;
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if (link)
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{
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tree->trie->fail = link->trie;
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return;
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}
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fail = fail->fail;
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}
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tree->trie->fail = recourse;
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}
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/* Set delta entries for the links of the given tree such that
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the preexisting delta value is larger than the current depth. */
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static void
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treedelta (register struct tree *tree,
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register unsigned int depth,
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unsigned char delta[])
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{
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if (!tree)
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return;
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treedelta(tree->llink, depth, delta);
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treedelta(tree->rlink, depth, delta);
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if (depth < delta[tree->label])
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delta[tree->label] = depth;
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}
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/* Return true if A has every label in B. */
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static int
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hasevery (register struct tree *a, register struct tree *b)
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{
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if (!b)
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return 1;
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if (!hasevery(a, b->llink))
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return 0;
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if (!hasevery(a, b->rlink))
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return 0;
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while (a && b->label != a->label)
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if (b->label < a->label)
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a = a->llink;
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else
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a = a->rlink;
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return !!a;
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}
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/* Compute a vector, indexed by character code, of the trie nodes
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referenced from the given tree. */
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static void
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treenext (struct tree *tree, struct trie *next[])
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{
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if (!tree)
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return;
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treenext(tree->llink, next);
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treenext(tree->rlink, next);
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next[tree->label] = tree->trie;
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}
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/* Compute the shift for each trie node, as well as the delta
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table and next cache for the given keyword set. */
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char *
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kwsprep (kwset_t kws)
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{
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register struct kwset *kwset;
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register int i;
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register struct trie *curr, *fail;
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register char *trans;
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unsigned char delta[NCHAR];
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struct trie *last, *next[NCHAR];
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kwset = (struct kwset *) kws;
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/* Initial values for the delta table; will be changed later. The
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delta entry for a given character is the smallest depth of any
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node at which an outgoing edge is labeled by that character. */
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if (kwset->mind < 256)
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for (i = 0; i < NCHAR; ++i)
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delta[i] = kwset->mind;
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else
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for (i = 0; i < NCHAR; ++i)
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delta[i] = 255;
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/* Check if we can use the simple boyer-moore algorithm, instead
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of the hairy commentz-walter algorithm. */
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if (kwset->words == 1 && kwset->trans == 0)
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{
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/* Looking for just one string. Extract it from the trie. */
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kwset->target = obstack_alloc(&kwset->obstack, kwset->mind);
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for (i = kwset->mind - 1, curr = kwset->trie; i >= 0; --i)
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{
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kwset->target[i] = curr->links->label;
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curr = curr->links->trie;
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}
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/* Build the Boyer Moore delta. Boy that's easy compared to CW. */
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for (i = 0; i < kwset->mind; ++i)
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delta[(unsigned char) kwset->target[i]] = kwset->mind - (i + 1);
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kwset->mind2 = kwset->mind;
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/* Find the minimal delta2 shift that we might make after
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a backwards match has failed. */
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for (i = 0; i < kwset->mind - 1; ++i)
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if (kwset->target[i] == kwset->target[kwset->mind - 1])
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kwset->mind2 = kwset->mind - (i + 1);
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}
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else
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{
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/* Traverse the nodes of the trie in level order, simultaneously
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computing the delta table, failure function, and shift function. */
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for (curr = last = kwset->trie; curr; curr = curr->next)
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{
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/* Enqueue the immediate descendents in the level order queue. */
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enqueue(curr->links, &last);
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curr->shift = kwset->mind;
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curr->maxshift = kwset->mind;
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/* Update the delta table for the descendents of this node. */
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treedelta(curr->links, curr->depth, delta);
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/* Compute the failure function for the decendents of this node. */
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treefails(curr->links, curr->fail, kwset->trie);
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/* Update the shifts at each node in the current node's chain
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of fails back to the root. */
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for (fail = curr->fail; fail; fail = fail->fail)
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{
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/* If the current node has some outgoing edge that the fail
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doesn't, then the shift at the fail should be no larger
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than the difference of their depths. */
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if (!hasevery(fail->links, curr->links))
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if (curr->depth - fail->depth < fail->shift)
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fail->shift = curr->depth - fail->depth;
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/* If the current node is accepting then the shift at the
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fail and its descendents should be no larger than the
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difference of their depths. */
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if (curr->accepting && fail->maxshift > curr->depth - fail->depth)
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fail->maxshift = curr->depth - fail->depth;
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}
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}
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/* Traverse the trie in level order again, fixing up all nodes whose
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shift exceeds their inherited maxshift. */
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for (curr = kwset->trie->next; curr; curr = curr->next)
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{
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if (curr->maxshift > curr->parent->maxshift)
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curr->maxshift = curr->parent->maxshift;
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if (curr->shift > curr->maxshift)
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curr->shift = curr->maxshift;
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}
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/* Create a vector, indexed by character code, of the outgoing links
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from the root node. */
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for (i = 0; i < NCHAR; ++i)
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next[i] = 0;
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treenext(kwset->trie->links, next);
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if ((trans = kwset->trans) != 0)
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for (i = 0; i < NCHAR; ++i)
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kwset->next[i] = next[(unsigned char) trans[i]];
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else
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for (i = 0; i < NCHAR; ++i)
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kwset->next[i] = next[i];
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}
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/* Fix things up for any translation table. */
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if ((trans = kwset->trans) != 0)
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for (i = 0; i < NCHAR; ++i)
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kwset->delta[i] = delta[(unsigned char) trans[i]];
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else
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for (i = 0; i < NCHAR; ++i)
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kwset->delta[i] = delta[i];
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return 0;
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}
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#define U(C) ((unsigned char) (C))
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/* Fast boyer-moore search. */
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static char *
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bmexec (kwset_t kws, char *text, size_t size)
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{
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struct kwset *kwset;
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register unsigned char *d1;
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register char *ep, *sp, *tp;
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register int d, gc, i, len, md2;
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|
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kwset = (struct kwset *) kws;
|
|
len = kwset->mind;
|
|
|
|
if (len == 0)
|
|
return text;
|
|
if (len > size)
|
|
return 0;
|
|
if (len == 1)
|
|
return memchr(text, kwset->target[0], size);
|
|
|
|
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;
|
|
}
|
|
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;
|
|
}
|
|
d = md2;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* Hairy multiple string search. */
|
|
static char *
|
|
cwexec (kwset_t kws, char *text, size_t len, struct kwsmatch *kwsmatch)
|
|
{
|
|
struct kwset *kwset;
|
|
struct trie **next, *trie, *accept;
|
|
char *beg, *lim, *mch, *lmch;
|
|
register unsigned char c, *delta;
|
|
register int d;
|
|
register char *end, *qlim;
|
|
register struct tree *tree;
|
|
register char *trans;
|
|
|
|
#ifdef lint
|
|
accept = NULL;
|
|
#endif
|
|
|
|
/* Initialize register copies and look for easy ways out. */
|
|
kwset = (struct kwset *) kws;
|
|
if (len < kwset->mind)
|
|
return 0;
|
|
next = kwset->next;
|
|
delta = kwset->delta;
|
|
trans = kwset->trans;
|
|
lim = text + len;
|
|
end = text;
|
|
if ((d = kwset->mind) != 0)
|
|
mch = 0;
|
|
else
|
|
{
|
|
mch = text, accept = kwset->trie;
|
|
goto match;
|
|
}
|
|
|
|
if (len >= 4 * kwset->mind)
|
|
qlim = lim - 4 * kwset->mind;
|
|
else
|
|
qlim = 0;
|
|
|
|
while (lim - end >= d)
|
|
{
|
|
if (qlim && end <= qlim)
|
|
{
|
|
end += d - 1;
|
|
while ((d = delta[c = *end]) && end < qlim)
|
|
{
|
|
end += d;
|
|
end += delta[(unsigned char) *end];
|
|
end += delta[(unsigned char) *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[(unsigned char) *--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 0;
|
|
|
|
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[(unsigned char) *--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->beg[0] = mch;
|
|
kwsmatch->size[0] = accept->depth;
|
|
}
|
|
return mch;
|
|
}
|
|
|
|
/* 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. */
|
|
char *
|
|
kwsexec (kwset_t kws, char *text, size_t size, struct kwsmatch *kwsmatch)
|
|
{
|
|
struct kwset *kwset;
|
|
char *ret;
|
|
|
|
kwset = (struct kwset *) kws;
|
|
if (kwset->words == 1 && kwset->trans == 0)
|
|
{
|
|
ret = bmexec(kws, text, size);
|
|
if (kwsmatch != 0 && ret != 0)
|
|
{
|
|
kwsmatch->index = 0;
|
|
kwsmatch->beg[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, 0);
|
|
free(kws);
|
|
}
|