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/*
 * $Id: NameTree.java,v 1.3 2009-01-16 16:26:09 tomoke Exp $
 *
 * Copyright 2004 Sun Microsystems, Inc., 4150 Network Circle,
 * Santa Clara, California 95054, U.S.A. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library 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
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
package com.sun.pdfview;

import java.io.IOException;

/**
 * A PDF name tree consists of three kinds of nodes:
 * 
    *
  • The root node contains only a kids entry, pointing to many * other objects *
  • An intermediate node contains the limits of all the children in * its subtree, and a kids entry for each child *
  • A leaf node contains a set of name-to-object mappings in a dictionary, * as well as the limits of the data contained in that child. *
* A PDF name tree is sorted in accordance with the String.compareTo() method. */ public class NameTree { /** the root object */ private PDFObject root; /** Creates a new instance of NameTree */ public NameTree(PDFObject root) { this.root = root; } /** * Find the PDF object corresponding to the given String in a name tree * * @param key the key we are looking for in the name tree * @return the object associated with str, if found, or null if not */ public PDFObject find(String key) throws IOException { return find(root, key); } /** * Recursively walk the name tree looking for a given value */ private PDFObject find(PDFObject root, String key) throws IOException { // first, look for a Names entry, meaning this is a leaf PDFObject names = root.getDictRef("Names"); if (names != null) { return findInArray(names.getArray(), key); } // no names given, look for kids PDFObject kidsObj = root.getDictRef("Kids"); if (kidsObj != null) { PDFObject[] kids = kidsObj.getArray(); for (int i = 0; i < kids.length; i++) { // find the limits of this kid PDFObject limitsObj = kids[i].getDictRef("Limits"); if (limitsObj != null) { String lowerLimit = limitsObj.getAt(0).getStringValue(); String upperLimit = limitsObj.getAt(1).getStringValue(); // are we in range? if ((key.compareTo(lowerLimit) >= 0) && (key.compareTo(upperLimit) <= 0)) { // we are, so find in this child return find(kids[i], key); } } } } // no luck return null; } /** * Find an object in a (key,value) array. Do this by splitting in half * repeatedly. */ private PDFObject findInArray(PDFObject[] array, String key) throws IOException { int start = 0; int end = array.length / 2; while (end >= start && start >= 0 && end < array.length) { // find the key at the midpoint int pos = start + ((end - start) / 2); String posKey = array[pos * 2].getStringValue(); // compare the key to the key we are looking for int comp = key.compareTo(posKey); if (comp == 0) { // they match. Return the value return array[(pos * 2) + 1]; } else if (comp > 0) { // too big, search the top half of the tree start = pos + 1; } else if (comp < 0) { // too small, search the bottom half of the tree end = pos - 1; } } // not found return null; } }




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