IOHelper.java

   1 /*
   2  * Svjatoslav Commons - shared library of common functionality.
   3  * Copyright ©2012-2013, Svjatoslav Agejenko, svjatoslav@svjatoslav.eu
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of version 2 of the GNU General Public License
   7  * as published by the Free Software Foundation.
   8  */
   9
  10 package eu.svjatoslav.commons.file;
  11
  12 import java.io.File;
  13 import java.io.FileInputStream;
  14 import java.io.FileNotFoundException;
  15 import java.io.FileOutputStream;
  16 import java.io.IOException;
  17
  18 public class IOHelper {
  19
  20         /**
  21          * Deletes files and directories recursively. WARNING!!! Follows symlinks!!!
  22          */
  23         public static void deleteRecursively(final File file) throws IOException {
  24                 if (file.isDirectory()) {
  25
  26                         for (final File subFile : file.listFiles())
  27                                 deleteRecursively(subFile);
  28
  29                         if (!file.delete())
  30                                 throw new FileNotFoundException("Failed to delete directory: "
  31                                                 + file);
  32
  33                         return;
  34                 }
  35
  36                 if (file.isFile())
  37                         if (!file.delete())
  38                                 throw new FileNotFoundException("Failed to delete file: "
  39                                                 + file);
  40         }
  41
  42         public static byte[] getFileContents(final File file)
  43                         throws FileNotFoundException, IOException {
  44
  45                 final byte[] result = new byte[(int) file.length()];
  46                 final FileInputStream fileInputStream = new FileInputStream(file);
  47                 fileInputStream.read(result);
  48                 fileInputStream.close();
  49                 return result;
  50         }
  51
  52         /**
  53          * Compares new file content with old file content. If content in equal,
  54          * then leaves file as-is. If content differs, then overrides file with the
  55          * new content.
  56          *
  57          * @return <code>true</code> if file was overwritten.
  58          */
  59         public static boolean overwriteFileIfContentDiffers(final File file,
  60                         final byte[] newContent) throws FileNotFoundException, IOException {
  61
  62                 checkForEquality: {
  63                         if (file.length() == newContent.length) {
  64
  65                                 final byte[] oldContent = getFileContents(file);
  66
  67                                 for (int i = 0; i < newContent.length; i++)
  68                                         if (newContent[i] != oldContent[i])
  69                                                 break checkForEquality;
  70
  71                                 // new file content in identical to old content
  72                                 return false;
  73                         }
  74                 }
  75
  76                 // New content differs from existing. Overwrite file.
  77                 saveToFile(file, newContent);
  78                 return true;
  79         }
  80
  81         public static void saveToFile(final File file, final byte[] content)
  82                         throws IOException {
  83                 final FileOutputStream fos = new FileOutputStream(file);
  84                 fos.write(content);
  85                 fos.close();
  86         }
  87
  88 }