inflater不会解压缩所有压缩字节

3 回答

• 0

  虽然不清楚，但我发现以下内容，

  它不是有缺陷的，而是放气的 .

  压缩数据时的Deflater令人惊讶地注意到字节数比原始未压缩数据增加 . 例如，上面的压缩数据数组有100个元素，因为数组的大小为100 .

  但是，如果我增加压缩数组大小（任意说200），然后使用该数组，则deflate方法将返回值108（这里比原始100多8个字节） . 这让我感到困惑，因为让我明白我需要知道什么是deflate压缩以及算法是如何工作的，我正在经历它 .

  所以这是更新的代码，

  byte orig[] = new byte[100];
  
          IntStream.range(0, 100).forEach(i -> orig[i] = (byte) i);
  
          System.out.println("OrigLength: " + orig.length);
  
          byte[] compressed = new byte[orig.length * 2]; // double it arbitrarily chosen 
  
  
          Deflater deflater = new Deflater();
          deflater.setInput(orig);
          deflater.finish();
          int compressedLength = 0;
          compressedLength = deflater.deflate(compressed);
          deflater.end();
          System.out.println("--------------------------------------------------------------------");
          System.out.println("CompressedLength::" + compressedLength); //now this will be 108
          for (int i = 0; i < compressedLength; i++) {
              System.out.print(compressed[i] + " ");
          }
  
  
          Inflater decompresser = new Inflater();
          byte[] result = new byte[orig.length];
          decompresser.setInput(compressed, 0, compressedLength);
          int resultLength  = decompresser.inflate(result);
          decompresser.end();
  
          System.out.println("\n--------------------------------------------------------------------");
          System.out.println("DecompressedLength::" + resultLength);
          for (int i = 0; i < resultLength; i++) {
              System.out.print(result[i] + " ");
          }
  
          System.out.println("\n--------------------------------------------------------------------");
  

  输出：

  OrigLength：100

  ---

  CompressedLength::108 //这是关注点8字节额外

  120 -100 99 96 100 98 102 97 101 99 -25 -32 -28 -30 -26 -31 -27 -29 23 16 20 18 22 17 21 19 -105 -112 -108 -110 -106 -111 -107 -109 87 80 84 82 86 81 85 83 -41 -48 -44 -46 -42 -47 -43 -45 55 48 52 50 54 49 53 51 -73 -80 -76 -78 -74 -79 -75 -77 119 112 116 114 118 113 117 115 -9 -16 -12 -14 -10 -15 -11 -13 15 8 12 10 14 9 13 11 -113 -120 -116 -118 -114 -119 -115 -117 79 72 76 74 6 0 -117 124 19 87

  DecompressedLength :: 100

  0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99

  回复于 2024-05-17T14:12:29+08:00
• 1

  你必须看看这个例子：

  https://github.com/DawnScience/dawn-common/blob/master/org.dawb.common.util/src/org/dawb/common/util/list/PrimitiveArrayEncoder.java#L95

  public static String compress(final String expanded) {
  
      try {
          byte[] input = expanded.getBytes("US-ASCII");
  
          // Compress the bytes
          byte[] output = new byte[input.length];
          Deflater compresser = new Deflater();
          compresser.setInput(input);
          compresser.finish();
          final int size  = compresser.deflate(output);
  
          return new String(output, 0, size, "US-ASCII");
      } catch (Exception ne) {
          ne.printStackTrace();
          return null;
      }
  }
  
  /**
   * Inflate a string
   * @param compressed
   * @return Inflated string.
   */
  public static String expand(final String compressed) {
  
      try {
          final byte[] output = compressed.getBytes("US-ASCII");
  
          // Decompress the bytes
          Inflater decompresser = new Inflater();
          decompresser.setInput(output, 0, output.length);
  
          byte[] result = new byte[output.length*2];
          int resultLength = decompresser.inflate(result);
          decompresser.end();
  
          // Decode the bytes into a String
          return new String(result, 0, resultLength, "US-ASCII");
  
      } catch (Exception ne) {
          ne.printStackTrace();
          return null;
      }
  
  }
  

  回复于 2024-05-17T14:12:29+08:00
• 0

  你可能会在这里找到一些想法：

  private static byte[] readCompressed(final Repository db,
          final AnyObjectId id) throws FileNotFoundException, IOException {
      final FileInputStream objStream = new FileInputStream(db.toFile(id));
      final byte[] compressed;
      try {
          compressed = new byte[objStream.available()];
          int off = 0;
          while (off < compressed.length)
              off += objStream.read(compressed, off, compressed.length - off);
      } finally {
          objStream.close();
      }
      return compressed;
  }
  

  完整代码：http://code.openhub.net/file?fid=50oAEc5CLFonr_2GPq0IoqxVPw8&cid=6SVb15jezXE&s=inflater%20does%20not%20decompress%20all%20the%20compressed%20bytes&pp=0&fl=Java&ff=1&projSelected=false&filterChecked,=true&mp,=1&filterChecked=true&mp=1&ml=1&me=1&md=1#L26

  回复于 2024-05-17T14:12:29+08:00