src/main/java/eu/svjatoslav/commons/file/IOHelper.java

   1 /*
   2  * Svjatoslav Commons - shared library of common functionality.
   3  * Copyright (C) 2012, 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         public static byte[] getFileContents(final File file)
  21                         throws FileNotFoundException, IOException {
  22
  23                 final byte[] result = new byte[(int) file.length()];
  24                 final FileInputStream fileInputStream = new FileInputStream(file);
  25                 fileInputStream.read(result);
  26                 fileInputStream.close();
  27                 return result;
  28         }
  29
  30         /**
  31          * Compares new file content with old file content. If content in equal,
  32          * then leaves file as-is. If content differs, then overrides file with the
  33          * new content.
  34          *
  35          * @return <code>true</code> if file was overwritten.
  36          */
  37         public static boolean overwriteFileIfContentDiffers(final File file,
  38                         final byte[] newContent) throws FileNotFoundException, IOException {
  39
  40                 checkForEquality: {
  41                         if (file.length() == newContent.length) {
  42
  43                                 final byte[] oldContent = getFileContents(file);
  44
  45                                 for (int i = 0; i < newContent.length; i++)
  46                                         if (newContent[i] != oldContent[i])
  47                                                 break checkForEquality;
  48
  49                                 // new file content in identical to old content
  50                                 return false;
  51                         }
  52                 }
  53
  54                 // New content differs from existing. Overwrite file.
  55                 saveToFile(file, newContent);
  56                 return true;
  57         }
  58
  59         public static void saveToFile(final File file, final byte[] content)
  60                         throws IOException {
  61                 final FileOutputStream fos = new FileOutputStream(file);
  62                 fos.write(content);
  63                 fos.close();
  64         }
  65
  66 }