/*

 * Copyright (c) 2005, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package com.sun.imageio.plugins.common;

import java.io.IOException;

import java.io.PrintStream;

import javax.imageio.stream.ImageOutputStream;

/*

 * Modified from original LZWCompressor to change interface to passing a

 * buffer of data to be compressed.

 */

public class LZWCompressor {

    /** base underlying code size of data being compressed 8 for TIFF, 1 to 8 for GIF **/

    int codeSize;

    /** reserved clear code based on code size **/

    int clearCode;

    /** reserved end of data code based on code size **/

    int endOfInfo;

    /** current number bits output for each code **/

    int numBits;

    /** limit at which current number of bits code size has to be increased **/

    int limit;

    /** the prefix code which represents the predecessor string to current input point **/

    short prefix;

    /** output destination for bit codes **/

    BitFile bf;

    /** general purpose LZW string table **/

    LZWStringTable lzss;

    /** modify the limits of the code values in LZW encoding due to TIFF bug / feature **/

    boolean tiffFudge;

    /**

     * @param out destination for compressed data

     * @param codeSize the initial code size for the LZW compressor

     * @param TIFF flag indicating that TIFF lzw fudge needs to be applied

     * @exception IOException if underlying output stream error

     **/

    public LZWCompressor(ImageOutputStream out, int codeSize, boolean TIFF)

        throws IOException

    {

        bf = new BitFile(out, !TIFF); // set flag for GIF as NOT tiff

        this.codeSize = codeSize;

        tiffFudge = TIFF;

        clearCode = 1 << codeSize;

        endOfInfo = clearCode + 1;

        numBits = codeSize + 1;

        limit = (1 << numBits) - 1;

        if (tiffFudge) {

            --limit;

        }

        prefix = (short)0xFFFF;

        lzss = new LZWStringTable();

        lzss.clearTable(codeSize);

        bf.writeBits(clearCode, numBits);

    }

    /**

     * @param buf data to be compressed to output stream

     * @exception IOException if underlying output stream error

     **/

    public void compress(byte[] buf, int offset, int length)

        throws IOException

    {

        int idx;

        byte c;

        short index;

        int maxOffset = offset + length;

        for (idx = offset; idx < maxOffset; ++idx) {

            c = buf[idx];

            if ((index = lzss.findCharString(prefix, c)) != -1) {

                prefix = index;

            } else {

                bf.writeBits(prefix, numBits);

                if (lzss.addCharString(prefix, c) > limit) {

                    if (numBits == 12) {

                        bf.writeBits(clearCode, numBits);

                        lzss.clearTable(codeSize);

                        numBits = codeSize + 1;

                    } else {

                        ++numBits;

                    }

                    limit = (1 << numBits) - 1;

                    if (tiffFudge) {

                        --limit;

                    }

                }

                prefix = (short)((short)c & 0xFF);

            }

        }

    }

    /*

     * Indicate to compressor that no more data to go so write out

     * any remaining buffered data.

     *

     * @exception IOException if underlying output stream error

     */

    public void flush() throws IOException {

        if (prefix != -1) {

            bf.writeBits(prefix, numBits);

        }

        bf.writeBits(endOfInfo, numBits);

        bf.flush();

    }

    public void dump(PrintStream out) {

        lzss.dump(out);

    }

}