/* kwset.c - search for any of a set of keywords. Copyright (C) 1989, 1998, 2000, 2005, 2007, 2009-2016 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 3, 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 resemblance to one discovered by Beate Commentz-Walter, although it is not identical. See: Commentz-Walter B. A string matching algorithm fast on the average. Lecture Notes in Computer Science 71 (1979), 118-32 . See also: Aho AV, Corasick MJ. Efficient string matching: an aid to bibliographic search. CACM 18, 6 (1975), 333-40 , which describes the failure function used below. */ #include #include "kwset.h" #include #include #include #include "system.h" #include "memchr2.h" #include "obstack.h" #include "xalloc.h" #define link kwset_link #ifdef GREP # include "xalloc.h" # undef malloc # define malloc xmalloc #endif #define NCHAR (UCHAR_MAX + 1) #define obstack_chunk_alloc malloc #define obstack_chunk_free free #define U(c) (to_uchar (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 { size_t 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 descendants. */ }; /* Structure returned opaquely to the caller, containing everything. */ struct kwset { struct obstack obstack; /* Obstack for node allocation. */ ptrdiff_t 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 *shift; /* Used in Boyer-Moore search for one string. */ char const *trans; /* Character translation table. */ /* If there's only one string, this is the string's last byte, translated via TRANS if TRANS is nonnull. */ char gc1; /* Likewise for the string's penultimate byte, if it has two or more bytes. */ char gc2; /* If there's only one string, this helps to match the string's last byte. If GC1HELP is negative, only GC1 matches the string's last byte; otherwise at least two bytes match, and B matches if TRANS[B] == GC1. If GC1HELP is in the range 0..(NCHAR - 1), there are exactly two such matches, and GC1HELP is the other match after conversion to unsigned char. If GC1HELP is at least NCHAR, there are three or more such matches; e.g., Greek has three sigma characters that all match when case-folding. */ int gc1help; }; /* Use TRANS to transliterate C. A null TRANS does no transliteration. */ static inline char tr (char const *trans, char c) { return trans ? trans[U(c)] : c; } /* Allocate and initialize a keyword set object, returning an opaque pointer to it. */ kwset_t kwsalloc (char const *trans) { struct kwset *kwset = xmalloc (sizeof *kwset); obstack_init (&kwset->obstack); kwset->words = 0; kwset->trie = obstack_alloc (&kwset->obstack, sizeof *kwset->trie); 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; } /* 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. */ void kwsincr (kwset_t kwset, char const *text, size_t len) { struct trie *trie = kwset->trie; char const *trans = kwset->trans; text += len; /* Descend the trie (built of reversed keywords) character-by-character, installing new nodes when necessary. */ while (len--) { unsigned char uc = *--text; unsigned char label = trans ? trans[uc] : uc; /* Descend the tree of outgoing links for this trie node, looking for the current character and keeping track of the path followed. */ struct tree *link = trie->links; struct tree *links[DEPTH_SIZE]; enum { L, R } dirs[DEPTH_SIZE]; links[0] = (struct tree *) &trie->links; dirs[0] = L; int 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 = obstack_alloc (&kwset->obstack, sizeof *link); link->llink = NULL; link->rlink = NULL; link->trie = obstack_alloc (&kwset->obstack, sizeof *link->trie); 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))) { struct tree *t, *r, *l, *rl, *lr; 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; } /* 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 (struct tree const *tree, struct trie const *fail, struct trie *recourse) { 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 descendant 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 (struct tree const *tree, 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 _GL_ATTRIBUTE_PURE hasevery (struct tree const *a, 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. */ void kwsprep (kwset_t kwset) { char const *trans = kwset->trans; int i; unsigned char deltabuf[NCHAR]; unsigned char *delta = trans ? deltabuf : kwset->delta; /* 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, MIN (kwset->mind, UCHAR_MAX), sizeof deltabuf); /* Traverse the nodes of the trie in level order, simultaneously computing the delta table, failure function, and shift function. */ struct trie *curr, *last; for (curr = last = kwset->trie; curr; curr = curr->next) { /* Enqueue the immediate descendants in the level order queue. */ enqueue (curr->links, &last); curr->shift = kwset->mind; curr->maxshift = kwset->mind; /* Update the delta table for the descendants of this node. */ treedelta (curr->links, curr->depth, delta); /* Compute the failure function for the descendants 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. */ struct trie *fail; 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 descendants 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. */ struct trie *nextbuf[NCHAR]; struct trie **next = trans ? nextbuf : kwset->next; memset (next, 0, sizeof nextbuf); treenext (kwset->trie->links, next); if (trans) for (i = 0; i < NCHAR; ++i) kwset->next[i] = next[U(trans[i])]; /* Check if we can use the simple boyer-moore algorithm, instead of the hairy commentz-walter algorithm. */ if (kwset->words == 1) { /* Looking for just one string. Extract it from the trie. */ kwset->target = obstack_alloc (&kwset->obstack, kwset->mind); for (i = kwset->mind - 1, curr = kwset->trie; i >= 0; --i) { kwset->target[i] = curr->links->label; curr = curr->next; } /* Looking for the delta2 shift that we might make after a backwards match has failed. Extract it from the trie. */ if (kwset->mind > 1) { kwset->shift = obstack_alloc (&kwset->obstack, sizeof *kwset->shift * (kwset->mind - 1)); for (i = 0, curr = kwset->trie->next; i < kwset->mind - 1; ++i) { kwset->shift[i] = curr->shift; curr = curr->next; } } char gc1 = tr (trans, kwset->target[kwset->mind - 1]); /* Set GC1HELP according to whether exactly one, exactly two, or three-or-more characters match GC1. */ int gc1help = -1; if (trans) { char const *equiv1 = memchr (trans, gc1, NCHAR); char const *equiv2 = memchr (equiv1 + 1, gc1, trans + NCHAR - (equiv1 + 1)); if (equiv2) gc1help = (memchr (equiv2 + 1, gc1, trans + NCHAR - (equiv2 + 1)) ? NCHAR : U(gc1) ^ (equiv1 - trans) ^ (equiv2 - trans)); } kwset->gc1 = gc1; kwset->gc1help = gc1help; if (kwset->mind > 1) kwset->gc2 = tr (trans, kwset->target[kwset->mind - 2]); } /* Fix things up for any translation table. */ if (trans) for (i = 0; i < NCHAR; ++i) kwset->delta[i] = delta[U(trans[i])]; } /* Delta2 portion of a Boyer-Moore search. *TP is the string text pointer; it is updated in place. EP is the end of the string text, and SP the end of the pattern. LEN is the pattern length; it must be at least 2. TRANS, if nonnull, is the input translation table. GC1 and GC2 are the last and second-from last bytes of the pattern, transliterated by TRANS; the caller precomputes them for efficiency. If D1 is nonnull, it is a delta1 table for shifting *TP when failing. KWSET->shift says how much to shift. */ static inline bool bm_delta2_search (char const **tpp, char const *ep, char const *sp, int len, char const *trans, char gc1, char gc2, unsigned char const *d1, kwset_t kwset) { char const *tp = *tpp; int d = len, skip = 0; while (true) { int i = 2; if (tr (trans, tp[-2]) == gc2) { while (++i <= d) if (tr (trans, tp[-i]) != tr (trans, sp[-i])) break; if (i > d) { for (i = d + skip + 1; i <= len; ++i) if (tr (trans, tp[-i]) != tr (trans, sp[-i])) break; if (i > len) { *tpp = tp - len; return true; } } } tp += d = kwset->shift[i - 2]; if (tp > ep) break; if (tr (trans, tp[-1]) != gc1) { if (d1) tp += d1[U(tp[-1])]; break; } skip = i - 1; } *tpp = tp; return false; } /* Return the address of the first byte in the buffer S (of size N) that matches the last byte specified by KWSET, a singleton. */ static char const * memchr_kwset (char const *s, size_t n, kwset_t kwset) { if (kwset->gc1help < 0) return memchr (s, kwset->gc1, n); int small_heuristic = 2; int small = (- (uintptr_t) s % sizeof (long) + small_heuristic * sizeof (long)); size_t ntrans = kwset->gc1help < NCHAR && small < n ? small : n; char const *slim = s + ntrans; for (; s < slim; s++) if (kwset->trans[U(*s)] == kwset->gc1) return s; n -= ntrans; return n == 0 ? NULL : memchr2 (s, kwset->gc1, kwset->gc1help, n); } /* Fast Boyer-Moore search (inlinable version). */ static inline size_t _GL_ATTRIBUTE_PURE bmexec_trans (kwset_t kwset, char const *text, size_t size) { unsigned char const *d1; char const *ep, *sp, *tp; int d; int len = kwset->mind; char const *trans = kwset->trans; if (len == 0) return 0; if (len > size) return -1; if (len == 1) { tp = memchr_kwset (text, size, kwset); return tp ? tp - text : -1; } d1 = kwset->delta; sp = kwset->target + len; tp = text + len; char gc1 = kwset->gc1; char gc2 = kwset->gc2; /* 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; tp <= ep; ) { char const *tp0 = tp; d = d1[U(tp[-1])], tp += d; d = d1[U(tp[-1])], tp += d; if (d != 0) { d = d1[U(tp[-1])], tp += d; d = d1[U(tp[-1])], tp += d; d = d1[U(tp[-1])], tp += d; if (d != 0) { d = d1[U(tp[-1])], tp += d; d = d1[U(tp[-1])], tp += d; d = d1[U(tp[-1])], tp += d; if (d != 0) { d = d1[U(tp[-1])], tp += d; d = d1[U(tp[-1])], tp += d; /* As a heuristic, prefer memchr to seeking by delta1 when the latter doesn't advance much. */ int advance_heuristic = 16 * sizeof (long); if (advance_heuristic <= tp - tp0) continue; tp--; tp = memchr_kwset (tp, text + size - tp, kwset); if (! tp) return -1; tp++; if (ep <= tp) break; } } } if (bm_delta2_search (&tp, ep, sp, len, trans, gc1, gc2, d1, kwset)) return tp - text; } /* 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 (bm_delta2_search (&tp, ep, sp, len, trans, gc1, gc2, NULL, kwset)) return tp - text; } return -1; } /* Fast Boyer-Moore search. */ static size_t bmexec (kwset_t kwset, char const *text, size_t size) { /* Help the compiler inline bmexec_trans in two ways, depending on whether kwset->trans is null. */ return (kwset->trans ? bmexec_trans (kwset, text, size) : bmexec_trans (kwset, text, size)); } /* Hairy multiple string search. */ static size_t _GL_ARG_NONNULL ((4)) cwexec (kwset_t kwset, char const *text, size_t len, struct kwsmatch *kwsmatch) { struct trie * const *next; struct trie const *trie; struct trie const *accept; char const *beg, *lim, *mch, *lmch; unsigned char c; unsigned char const *delta; int d; char const *end, *qlim; struct tree const *tree; char const *trans; #ifdef lint accept = NULL; #endif /* Initialize register copies and look for easy ways out. */ 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) { unsigned char uc = *--beg; c = trans ? trans[uc] : uc; 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) { unsigned char uc = *--beg; c = trans ? trans[uc] : uc; 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; } kwsmatch->index = accept->accepting / 2; kwsmatch->offset[0] = mch - text; kwsmatch->size[0] = accept->depth; return mch - text; } /* Search TEXT for a match of any member of KWSET. Return the offset (into TEXT) of the first byte of the matching substring, or (size_t) -1 if no match is found. Upon a match, store details in *KWSMATCH: index of matched keyword, start offset (same as the return value), and length. */ size_t kwsexec (kwset_t kwset, char const *text, size_t size, struct kwsmatch *kwsmatch) { if (kwset->words == 1) { size_t ret = bmexec (kwset, text, size); if (ret != (size_t) -1) { kwsmatch->index = 0; kwsmatch->offset[0] = ret; kwsmatch->size[0] = kwset->mind; } return ret; } else return cwexec (kwset, text, size, kwsmatch); } /* Free the components of the given keyword set. */ void kwsfree (kwset_t kwset) { obstack_free (&kwset->obstack, NULL); free (kwset); }