BitStreamCODEC.java

/* 
 * Copyright (C) 2015 RankSys http://ranksys.org
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */
package org.ranksys.compression.codecs.dsi;

import it.unimi.dsi.io.OutputBitStream;
import it.unimi.dsi.io.InputBitStream;
import java.io.IOException;
import java.util.Arrays;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.ranksys.compression.codecs.AbstractCODEC;

/**
 * Wrapper of dsiutils' BitStreams.
 * 
 * Check http://dsiutils.di.unimi.it/
 *
 * @author Saúl Vargas (Saul.Vargas@glasgow.ac.uk)
 */
public abstract class BitStreamCODEC extends AbstractCODEC<byte[]> {

    private static final Logger LOG = Logger.getLogger(BitStreamCODEC.class.getName());

    @Override
    public byte[] co(int[] in, int offset, int len) {

        byte[] out = new byte[len * 4 + 1024];
        int writtenBits = 0;
        try (OutputBitStream obs = new OutputBitStream(out)) {
            write(obs, in, offset, len);
            writtenBits = (int) obs.writtenBits();
        } catch (IOException ex) {
            LOG.log(Level.SEVERE, null, ex);
        }

        out = Arrays.copyOf(out, (writtenBits + 7) / 8);

        add(len * Integer.BYTES, out.length * Byte.BYTES);

        return out;
    }

    /**
     * Write integer array to BitStream.
     *
     * @param obs output bit stream
     * @param in input array
     * @param offset offset of array
     * @param len number of bytes to write
     * @throws IOException when IO error
     */
    protected abstract void write(OutputBitStream obs, int[] in, int offset, int len) throws IOException;

    @Override
    public int dec(final byte[] in, final int[] out, final int outOffset, final int len) {
        try (InputBitStream ibs = new InputBitStream(in)) {
            read(ibs, out, outOffset, len);
        } catch (IOException ex) {
            LOG.log(Level.SEVERE, null, ex);
        }

        return 0;
    }

    /**
     * Reads a BitStream to an array.
     *
     * @param ibs input bit stream
     * @param out output array
     * @param offset array offset
     * @param len number of integers to read
     * @throws IOException when IO error
     */
    protected abstract void read(final InputBitStream ibs, final int[] out, final int offset, final int len) throws IOException;

    @Override
    public boolean isIntegrated() {
        return false;
    }

}