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1 /* HashTree -- Tree in a Hashtable
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3 Digital Image Library servlet components
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5 Copyright (C) 2001, 2002 Robert Casties (robcast@mail.berlios.de)
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6
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7 This program is free software; you can redistribute it and/or modify it
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8 under the terms of the GNU General Public License as published by the
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9 Free Software Foundation; either version 2 of the License, or (at your
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10 option) any later version.
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11
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12 Please read license.txt for the full details. A copy of the GPL
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13 may be found at http://www.gnu.org/copyleft/lgpl.html
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14
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15 You should have received a copy of the GNU General Public License
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16 along with this program; if not, write to the Free Software
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17 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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18
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19 */
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20
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21 package digilib.util;
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22
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23 import java.util.LinkedList;
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24 import java.util.List;
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25 import java.util.Map;
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26 import java.util.StringTokenizer;
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27
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28 /**
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29 * Tree representation wrapper for a HashMap.
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30 *
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31 * The HashTree is constructed from a HashMap filled with 'branches' with
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32 * 'leaves'. The branches are stored as String keys in the HashMap. The String
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33 * values are leaves.
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34 *
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35 * Branches are matched in 'twigs' separated by 'twig separator' Strings. The
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36 * return values for a match are leaf values separated by 'leaf separator'
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37 * Strings.
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38 *
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39 * @author casties
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40 */
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41 public class HashTree {
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42
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43 private Map<String, String> table;
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44
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45 private String twigSep = "/";
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46
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47 private String leafSep = ",";
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48
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49 /**
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50 * Constructor of a HashTree.
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51 *
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52 * Creates a HashTree wrapper around a given HashMap, using the given twig
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53 * separator and leaf separator.
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54 *
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55 * @param t
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56 * @param twig_separator
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57 * @param leaf_separator
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58 */
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59 public HashTree(Map<String, String> t, String twig_separator, String leaf_separator) {
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60 table = t;
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61 twigSep = twig_separator;
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62 leafSep = leaf_separator;
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63 optimizeTable();
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64 }
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65
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66 private void optimizeTable() {
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67 }
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68
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69 /**
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70 * Matches the given branch against the HashTree.
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71 *
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72 * Returns a LinkedList of all leaves on all matching branches in the tree.
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73 * Branches in the tree match if they are substrings starting at the same
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74 * root.
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75 *
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76 * @param branch
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77 * @return
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78 */
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79 public List<String> match(String branch) {
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80 String b = "";
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81 String m;
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82 LinkedList<String> matches = new LinkedList<String>();
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83
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84 // split branch
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85 StringTokenizer twig = new StringTokenizer(branch, twigSep);
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86 // walk branch and check with tree
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87 while (twig.hasMoreTokens()) {
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88 if (b.length() == 0) {
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89 b = twig.nextToken();
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90 } else {
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91 b += twigSep + twig.nextToken();
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92 }
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93 m = table.get(b);
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94 if (m != null) {
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95 if (m.indexOf(leafSep) < 0) {
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96 // single leaf
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97 matches.add(m);
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98 } else {
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99 // split leaves
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100 StringTokenizer leaf = new StringTokenizer(m, leafSep);
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101 while (leaf.hasMoreTokens()) {
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102 matches.add(leaf.nextToken());
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103 }
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104 }
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105 }
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106 }
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107 if (matches.size() > 0) {
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108 return matches;
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109 } else {
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110 return null;
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111 }
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112 }
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113 }
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