Question

So I have a input stream from which I read a smaller fixed-size buffer which I’m trying to Deflate inside a Runnable class.

randomClass implements Runnable {
    public void run() {
        ...
        byte[] output = new Byte[FIXED];
        Deflater deflater = new Deflater();
        deflater.setInput(uncompressed);
        deflater.setLevel(Deflater.DEFLATED);
        int length = deflater.deflate(output);
        ...
    } 
}

The issue I’m running into is that length is always returning 0 which means I need more input according to the doc? However, I’ve checked that the uncompressed is not null. How can I get the bytes out of the output?

Also I believe I should be calling deflater.finish() only at the last block. Is this correct?

Answer 1

I think compresser.finish(); should be called right after deflater.setInput(uncompressed);. Then proceed with the next steps, it should be fine.

Same is mentioned in the documentation as below:

 byte[] output = new byte[100];
 Deflater compresser = new Deflater();
 compresser.setInput(input);
 compresser.finish();  //<-- finished is called here
 int compressedDataLength = compresser.deflate(output);

Also, please set the level at the time of initialization e.g.

 Deflater compresser = new Deflater(Deflater.DEFLATED, false); //<-set the level
 byte[] output = new byte[100];
 compresser.setInput(input);
 compresser.finish();  //<-- finished is called here
 int compressedDataLength = compresser.deflate(output);

Hope this helps.