package ucar.nc2.stream;

import java.io.*;
import java.util.zip.Deflater;
import java.util.zip.DeflaterOutputStream;

/**
 * Created by rmay on 8/13/15.
 */
public class NcStreamCompressedOutputStream extends DataOutputStream {
    private OutputStream writer;
    private DeflaterOutputStream dout;
    private ByteArrayOutputStream buffer;

    public NcStreamCompressedOutputStream(OutputStream out, int bufferSize,
                                          int level) {
        super(out);

        // Save the original out for use when we flush
        writer = out;

        // write to an internal buffer, so we can find out the size when
        // compressed
        buffer = new ByteArrayOutputStream(bufferSize);
        dout = new DeflaterOutputStream(buffer, new Deflater(level), 4 * 1024);

        // Override out to point to our compressed stream
        this.out = new BufferedOutputStream(dout, 1024 * 1024);
    }

    @Override
    public void flush() throws IOException {
        // Make sure we flush out our stream
        out.flush();

        // Have to finish the deflater in order to get proper block.
        dout.finish();

        // Grab size of compressed data, write this out and then the block
        // of compressed data. Set number of bytes written to this value.
        int compressedSize = buffer.size();
        written = compressedSize;
        written += NcStream.writeVInt(writer, compressedSize);
        buffer.writeTo(writer);

        // Reset buffer so that in theory we could continue to write to this
        // stream.
        buffer.reset();
    }
}