// Copyright 2001, FreeHEP.
package org.freehep.util.io;

import java.io.IOException;
import java.io.InputStream;
import java.util.zip.InflaterInputStream;

/**
 * Special stream that can be used to read uncompressed first and compressed
 * from a certain byte.
 * 
 * IMPORTANT: inherits from InputStream rather than FilterInputStream so that
 * the correct read(byte[], int, int) method is used.
 * 
 * @author Mark Donszelmann
 * @version $Id: DecompressableInputStream.java 8584 2006-08-10 23:06:37Z duns $
 */
public class DecompressableInputStream extends InputStream {

    private boolean decompress;

    private InflaterInputStream iis;

    private InputStream in;

    /**
     * Creates a Decompressable input stream from given stream.
     * 
     * @param input stream to read from.
     */
    public DecompressableInputStream(InputStream input) {
        super();
        in = input;
        decompress = false;
    }

    public int read() throws IOException {
        return (decompress) ? iis.read() : in.read();
    }

    public long skip(long n) throws IOException {
        return (decompress) ? iis.skip(n) : in.skip(n);
    }

    /**
     * Start reading in compressed mode from the next byte.
     * 
     * @throws IOException if read fails.
     */
    public void startDecompressing() throws IOException {
        decompress = true;
        iis = new InflaterInputStream(in);
    }
}