stream - Java 1.8: Use DeflaterInputStream get size of comressed while compressing

Question

I am trying to fill a compressed buffer gradually with a lot of calls to an append-function. After each call of the function, I want to know how big the compressed stream is currently. This way, I can stop putting in new data once a certain compressed size has been reached. If I just append the input data and compress all of the accumulated data at every append(), I will get performance problems, because I will always have to compress the whole data from the start each time.

I cannot find out how to do it. I tried using PipedInputStream and PipedOutputStream, but the problem is that a call to DeflaterInputStream.read() will block and I don't see a way of predicting if I will read a byte or not. This is, because DeflaterInputStream.available() seems to always return 1, regardless if I can read a byte or not. As the compressed stream is, well, compressed, not every time I put a byte in I will get a byte out. That's the point of it, after all.

Do you people have an idea what I could do? Example pseudo code:

    protected DeflaterInputStream m_dis;
    protected PipedInputStream m_is;
    protected PipedOutputStream m_os;
    protected ByteArrayOutputStream m_out;

     protected void Init(int s32BufSize) {
        try
        {
            m_os = new PipedOutputStream();
            m_is = new PipedInputStream(m_os);
            m_dis = new DeflaterInputStream(m_is);
            m_out = new ByteArrayOutputStream();
        }
        catch (Exception ex)
        {

        }
    }

    public long append(byte[] appBytes) 
    {
        try
        {
            m_os.write(appBytes);
            m_os.flush();

            while (m_dis.available() > 0) // will always return 1
            {
                m_out.write(m_dis.read()); // read() may block, preventing next call to append()
                m_out.flush();
            }
        } catch (Exception ex) {
            System.out.println(ex.toString());
        }
        return m_out.size();
    }

I also tried to offload the reading from m_dis to another thread. But, the read then blocks until I call m_os.close(). But after such a call I cannot reconnect the streams anymore so I could go on.

Does anyone have an idea? Thanks for any help!

Best regards,

Peer

question from:https://stackoverflow.com/questions/65844896/java-1-8-use-deflaterinputstream-get-size-of-comressed-while-compressing

Answer 1

Waitting for answers