syntaxtree.java

java正这表达式,简单.好用.

package org.apache.oro.text.awk;

/* ====================================================================
 * The Apache Software License, Version 1.1
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 * Copyright (c) 2000 The Apache Software Foundation.  All rights
 * reserved.
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 * modification, are permitted provided that the following conditions
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 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
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 *    distribution.
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 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
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 * 4. The names "Apache" and "Apache Software Foundation", "Jakarta-Oro" 
 *    must not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact [e-mail].
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 * 5. Products derived from this software may not be called "Apache" 
 *    or "Jakarta-Oro", nor may "Apache" or "Jakarta-Oro" appear in their 
 *    name, without prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
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 *
 * Portions of this software are based upon software originally written 
 * by Daniel F. Savarese. We appreciate his contributions.
 */

import java.util.*;

 /**
 IMPORTANT!!!!!!!!!!!!!
 Don't forget to optimize this module.  The calculation of follow can
 be accelerated by calculating first and last only once for each node and
 saving instead of doing dynamic calculation every time.

 @author <a href="mailto:[e-mail]">Daniel F. Savarese</a>
 @version $Id: SyntaxTree.java,v 1.2 2000/07/23 23:25:20 jon Exp $
 */
final class SyntaxTree {
  int _positions;
  SyntaxNode _root;
  LeafNode[] _nodes;
  BitSet[] _followSet;
  
  SyntaxTree(SyntaxNode root, int positions) {
    _root      = root;
    _positions = positions;
  }

  void _computeFollowPositions() {
    int index;

    _followSet = new BitSet[_positions];
    _nodes     = new LeafNode[_positions];
    index =    _positions;

    while(0 < index--)
      _followSet[index] = new BitSet(_positions);

    _root._followPosition(_followSet, _nodes);
  }

  private void __addToFastMap(BitSet pos, boolean[] fastMap, boolean[] done){
    int token, node;

    for(node = 0; node < _positions; node++){
      if(pos.get(node) && !done[node]){
	done[node] = true;

	for(token=0; token < LeafNode._NUM_TOKENS; token++){
	  if(!fastMap[token])
	    fastMap[token] = _nodes[node]._matches((char)token);
	}
      }
    }
  }

  boolean[] createFastMap(){
    boolean[] fastMap, done;
    int token;

    fastMap  = new boolean[LeafNode._NUM_TOKENS]; 
    done     = new boolean[_positions];
    __addToFastMap(_root._firstPosition(), fastMap, done);

    return fastMap;
  }
}