How can I Zip and Unzip a string using GZIPOutputStream that is compatible with .Net?

Question

I need an example for compressing a string using GZip in android. I want to send a string like "hello" to the method and get the following zipped string:

BQAAAB+LCAAAAAAABADtvQdgHEmWJSYvbcp7f0r1StfgdKEIgGATJNiQQBDswYjN5pLsHWlHIymrKoHKZVZlXWYWQMztnbz33nvvvffee++997o7nU4n99//P1xmZAFs9s5K2smeIYCqyB8/fnwfPyLmeVlW/w+GphA2BQAAAA==

Then I need to decompress it. Can anybody give me an example and complete the following methods?

private String compressString(String input) {     //... }  private String decompressString(String input) {     //... } 

Thanks,

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update

According to scessor's answer, Now I have the following 4 methods. Android and .net compress and decompress methods. These methods are compatible with each other except in one case. I mean they are compatible in the first 3 states but incompatible in the 4th state:

• state 1) Android.compress <-> Android.decompress: (OK)
• state 2) Net.compress <-> Net.decompress: (OK)
• state 3) Net.compress -> Android.decompress: (OK)
• state 4) Android.compress -> .Net.decompress: (NOT OK)

can anybody solve it?

Android methods:

public static String compress(String str) throws IOException {      byte[] blockcopy = ByteBuffer             .allocate(4)             .order(java.nio.ByteOrder.LITTLE_ENDIAN)             .putInt(str.length())             .array();     ByteArrayOutputStream os = new ByteArrayOutputStream(str.length());     GZIPOutputStream gos = new GZIPOutputStream(os);     gos.write(str.getBytes());     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 Base64.encode(compressed);  }  public static String decompress(String zipText) throws IOException {     byte[] compressed = Base64.decode(zipText);     if (compressed.length > 4)     {         GZIPInputStream gzipInputStream = new GZIPInputStream(                 new ByteArrayInputStream(compressed, 4,                         compressed.length - 4));          ByteArrayOutputStream baos = new ByteArrayOutputStream();         for (int value = 0; value != -1;) {             value = gzipInputStream.read();             if (value != -1) {                 baos.write(value);             }         }         gzipInputStream.close();         baos.close();         String sReturn = new String(baos.toByteArray(), "UTF-8");         return sReturn;     }     else     {         return "";     } } 

.Net methods:

public static string compress(string text) {     byte[] buffer = Encoding.UTF8.GetBytes(text);     MemoryStream ms = new MemoryStream();     using (GZipStream zip = new GZipStream(ms, CompressionMode.Compress, true))     {         zip.Write(buffer, 0, buffer.Length);     }      ms.Position = 0;     MemoryStream outStream = new MemoryStream();      byte[] compressed = new byte[ms.Length];     ms.Read(compressed, 0, compressed.Length);      byte[] gzBuffer = new byte[compressed.Length + 4];     System.Buffer.BlockCopy(compressed, 0, gzBuffer, 4, compressed.Length);     System.Buffer.BlockCopy(BitConverter.GetBytes(buffer.Length), 0, gzBuffer, 0, 4);     return Convert.ToBase64String(gzBuffer); }  public static string decompress(string compressedText) {     byte[] gzBuffer = Convert.FromBase64String(compressedText);     using (MemoryStream ms = new MemoryStream())     {         int msgLength = BitConverter.ToInt32(gzBuffer, 0);         ms.Write(gzBuffer, 4, gzBuffer.Length - 4);          byte[] buffer = new byte[msgLength];          ms.Position = 0;         using (GZipStream zip = new GZipStream(ms, CompressionMode.Decompress))         {             zip.Read(buffer, 0, buffer.Length);         }          return Encoding.UTF8.GetString(buffer);     } } 

Answer 1

The GZIP methods:

public static byte[] compress(String string) throws IOException {     ByteArrayOutputStream os = new ByteArrayOutputStream(string.length());     GZIPOutputStream gos = new GZIPOutputStream(os);     gos.write(string.getBytes());     gos.close();     byte[] compressed = os.toByteArray();     os.close();     return compressed; }  public static String decompress(byte[] compressed) throws IOException {     final int BUFFER_SIZE = 32;     ByteArrayInputStream is = new ByteArrayInputStream(compressed);     GZIPInputStream gis = new GZIPInputStream(is, BUFFER_SIZE);     StringBuilder string = new StringBuilder();     byte[] data = new byte[BUFFER_SIZE];     int bytesRead;     while ((bytesRead = gis.read(data)) != -1) {         string.append(new String(data, 0, bytesRead));     }     gis.close();     is.close();     return string.toString(); } 

And a test:

final String text = "hello"; try {     byte[] compressed = compress(text);     for (byte character : compressed) {         Log.d("test", String.valueOf(character));     }     String decompressed = decompress(compressed);     Log.d("test", decompressed); } catch (IOException e) {     e.printStackTrace(); } 

=== Update ===

If you need .Net compability my code has to be changed a little:

public static byte[] compress(String string) throws IOException {     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());     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; }  public static String decompress(byte[] compressed) throws IOException {     final int BUFFER_SIZE = 32;     ByteArrayInputStream is = new ByteArrayInputStream(compressed, 4, compressed.length - 4);     GZIPInputStream gis = new GZIPInputStream(is, BUFFER_SIZE);     StringBuilder string = new StringBuilder();     byte[] data = new byte[BUFFER_SIZE];     int bytesRead;     while ((bytesRead = gis.read(data)) != -1) {         string.append(new String(data, 0, bytesRead));     }     gis.close();     is.close();     return string.toString(); } 

You can use the same test script.