kwset.c

linux平台中

     delta entry for a given character is the smallest depth of any
     node at which an outgoing edge is labeled by that character. */
  if (kwset->mind < 256)
    for (i = 0; i < NCHAR; ++i)
      delta[i] = kwset->mind;
  else
    for (i = 0; i < NCHAR; ++i)
      delta[i] = 255;

  /* Check if we can use the simple boyer-moore algorithm, instead
     of the hairy commentz-walter algorithm. */
  if (kwset->words == 1 && kwset->trans == 0)
    {
      /* 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->links->trie;
	}
      /* Build the Boyer Moore delta.  Boy that's easy compared to CW. */
      for (i = 0; i < kwset->mind; ++i)
	delta[(unsigned char) kwset->target[i]] = kwset->mind - (i + 1);
      kwset->mind2 = kwset->mind;
      /* Find the minimal delta2 shift that we might make after
	 a backwards match has failed. */
      for (i = 0; i < kwset->mind - 1; ++i)
	if (kwset->target[i] == kwset->target[kwset->mind - 1])
	  kwset->mind2 = kwset->mind - (i + 1);
    }
  else
    {
      /* 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] = 0;
      treenext(kwset->trie->links, next);

      if ((trans = kwset->trans) != 0)
	for (i = 0; i < NCHAR; ++i)
	  kwset->next[i] = next[(unsigned char) trans[i]];
      else
	for (i = 0; i < NCHAR; ++i)
	  kwset->next[i] = next[i];
    }

  /* Fix things up for any translation table. */
  if ((trans = kwset->trans) != 0)
    for (i = 0; i < NCHAR; ++i)
      kwset->delta[i] = delta[(unsigned char) trans[i]];
  else
    for (i = 0; i < NCHAR; ++i)
      kwset->delta[i] = delta[i];

  return 0;
}

#define U(C) ((unsigned char) (C))

/* 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 = 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 -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[(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->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 == 0)
    {
      size_t ret = bmexec (kws, text, size);
      if (kwsmatch != 0 && 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, 0);
  free(kws);
}