1 | /*
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2 | * Copyright 2003-2004 The Apache Software Foundation
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3 | *
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4 | * Licensed under the Apache License, Version 2.0 (the "License");
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5 | * you may not use this file except in compliance with the License.
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6 | * You may obtain a copy of the License at
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7 | *
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8 | * http://www.apache.org/licenses/LICENSE-2.0
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9 | *
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10 | * Unless required by applicable law or agreed to in writing, software
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11 | * distributed under the License is distributed on an "AS IS" BASIS,
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12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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13 | * See the License for the specific language governing permissions and
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14 | * limitations under the License.
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15 | *
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16 | */
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17 |
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18 | package org.apache.tools.ant.types.selectors.modifiedselector;
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19 |
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20 |
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21 | import java.io.File;
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22 |
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23 |
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24 | /**
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25 | * Computes a 'hashvalue' for the content of file using String.hashValue().
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26 | * Use of this algorithm doesn't require any additional nested <param>s and
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27 | * doesn't support any.
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28 | *
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29 | * @version 2003-09-13
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30 | * @since Ant 1.6
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31 | */
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32 | public class HashvalueAlgorithm implements Algorithm {
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33 |
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34 | /**
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35 | * This algorithm doesn't need any configuration.
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36 | * Therefore it's always valid.
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37 | * @return always true
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38 | */
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39 | public boolean isValid() {
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40 | return true;
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41 | }
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42 |
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43 | /**
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44 | * Computes a 'hashvalue' for a file content.
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45 | * It reads the content of a file, convert that to String and use the
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46 | * String.hashCode() method.
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47 | * @param file The file for which the value should be computed
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48 | * @return the hashvalue or <i>null</i> if the file couldn't be read
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49 | */
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50 | // Because the content is only read the file will not be damaged. I tested
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51 | // with JPG, ZIP and PDF as binary files.
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52 | public String getValue(File file) {
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53 | try {
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54 | if (!file.canRead()) {
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55 | return null;
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56 | }
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57 | java.io.FileInputStream fis = new java.io.FileInputStream(file);
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58 | byte[] content = new byte[fis.available()];
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59 | fis.read(content);
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60 | fis.close();
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61 | String s = new String(content);
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62 | int hash = s.hashCode();
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63 | return Integer.toString(hash);
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64 | } catch (Exception e) {
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65 | return null;
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66 | }
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67 | }
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68 |
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69 |
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70 | /**
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71 | * Override Object.toString().
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72 | * @return information about this comparator
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73 | */
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74 | public String toString() {
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75 | return "HashvalueAlgorithm";
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76 | }
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77 |
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78 | }
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