CSUtil.java revision 56ed4167b942ec265f9cee70ac4d71d10b3835ce 
1/*
2 * Copyright (C) 2010 Google Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package org.clearsilver;
18
19import java.io.File;
20import java.util.LinkedList;
21import java.util.List;
22
23/**
24 * Utility class containing helper methods
25 */
26public final class CSUtil {
27
28  private CSUtil() { }
29
30  public static final String HDF_LOADPATHS = "hdf.loadpaths";
31
32  /**
33   * Helper function that returns a concatenation of the loadpaths in the
34   * provided HDF.
35   * @param hdf an HDF structure containing load paths.
36   * @return A list of loadpaths in order in which to search.
37   * @throws NullPointerException if no loadpaths are found.
38   */
39  public static List<String> getLoadPaths(HDF hdf) {
40    return getLoadPaths(hdf, false);
41  }
42
43  /**
44   * Helper function that returns a concatenation of the loadpaths in the
45   * provided HDF.
46   * @param hdf an HDF structure containing load paths.
47   * @param allowEmpty if {@code true} then this will return an empty list when
48   *     no loadpaths are found in the HDF object, otherwise a
49   *     {@link NullPointerException} is thrown. Loadpaths are not needed if
50   *     no files are read in or are all specified by absolute paths.
51   * @return A list of loadpaths in order in which to search.
52   * @throws NullPointerException if no loadpaths are found and allowEmpty is
53   *     {@code false}.
54   */
55  public static List<String> getLoadPaths(HDF hdf, boolean allowEmpty) {
56    List<String> list = new LinkedList<String>();
57    HDF loadpathsHdf = hdf.getObj(HDF_LOADPATHS);
58    if (loadpathsHdf == null) {
59      if (allowEmpty) {
60        return list;
61      } else {
62        throw new NullPointerException("No HDF loadpaths located in the "
63            + "specified HDF structure");
64      }
65    }
66    for (HDF lpHdf = loadpathsHdf.objChild(); lpHdf != null;
67        lpHdf = lpHdf.objNext()) {
68      list.add(lpHdf.objValue());
69    }
70    return list;
71  }
72
73  /**
74   * Given an ordered list of directories to look in, locate the specified file.
75   * Returns <code>null</code> if file not found.
76   * @param loadpaths the ordered list of paths to search.
77   * @param filename the name of the file.
78   * @return a File object corresponding to the file. <code>null</code> if
79   *     file not found.
80   */
81  public static File locateFile(List<String> loadpaths, String filename) {
82    if (filename == null) {
83      throw new NullPointerException("No filename provided");
84    }
85    if (loadpaths == null) {
86      throw new NullPointerException("No loadpaths provided.");
87    }
88    for (String path : loadpaths) {
89      File file = new File(path, filename);
90      if (file.exists()) {
91        return file;
92      }
93    }
94    return null;
95  }
96}
97