Android Open Source - sodf Gzip

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License

The source code is released under:

Copyright (c) 2013 Lorenz Lehmann Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Sof...

Java Source Code

package lal.sodf.framework.compressor;
/* www .j  ava  2 s  .co  m*/
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.ByteBuffer;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;

import android.util.Log;

/**
 * A compression algorithm based on the Android implementation of GZIP.
 * The code used in the compression and decompression method was written by StackOverflow user "scessor".
 * The original example can be found here: http://stackoverflow.com/questions/6717165/how-can-i-zip-and-unzip-a-string-using-gzipoutputstream-that-is-compatible-with
 * The code has been slightly modified to be used 
 * @author scessor, Lorenz Lehmann
 *
 */
public class Gzip implements CompressionAlgorithm{

  @Override
  public byte[] compress(String string) {
    try {
      if (string == null || string.length() <= 0) return new byte[0];
      byte[] blockcopy = ByteBuffer
          .allocate(4)
          .order(java.nio.ByteOrder.LITTLE_ENDIAN)
          .putInt(string.length())
          .array();
      ByteArrayOutputStream os = new ByteArrayOutputStream(string.length());
      GZIPOutputStream gos = new GZIPOutputStream(os);
      gos.write(string.getBytes("UTF-8"));
      gos.close();
      os.close();
      byte[] compressed = new byte[4 + os.toByteArray().length];
      System.arraycopy(blockcopy, 0, compressed, 0, 4);
      System.arraycopy(os.toByteArray(), 0, compressed, 4, os.toByteArray().length);
      return compressed;
    } catch (IOException e){
      Log.e(getClass().getSimpleName(), "Error on compression "+e);
      return new String("ERROR").getBytes();
    }
  }

  @Override
  public String decompress(byte[] compressed) {
    try {
      final int BUFFER_SIZE = 32;
      ByteArrayInputStream is = new ByteArrayInputStream(compressed, 4, compressed.length - 4);
      GZIPInputStream gis = new GZIPInputStream(is, BUFFER_SIZE);      
      InputStreamReader reader = new InputStreamReader(gis, "UTF-8");
      BufferedReader in = new BufferedReader(reader);
      StringBuilder sb = new StringBuilder();
      String read;
      while ((read = in.readLine()) != null) {
        sb.append(read);
      }
      in.close();
      reader.close();
      gis.close();
      is.close();
      return sb.toString();
    } catch (IOException e){
      Log.e(getClass().getSimpleName(), "Error on decompression "+e);
      return new String("ERROR");
    }
  }

  @Override
  public String getIdentifier() {
    return "gzip";
  }

}

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