com.lowagie.text.pdf.LZWDecoder Maven / Gradle / Ivy

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/*
 * Copyright 2002-2008 by Paulo Soares.
 *
 * This code was originally released in 2001 by SUN (see class
 * com.sun.media.imageioimpl.plugins.tiff.TIFFLZWDecompressor.java)
 * using the BSD license in a specific wording. In a mail dating from
 * January 23, 2008, Brian Burkhalter (@sun.com) gave us permission
 * to use the code under the following version of the BSD license:
 *
 * Copyright (c) 2005 Sun Microsystems, Inc. All  Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistribution of source code must retain the above copyright
 *   notice, this  list of conditions and the following disclaimer.
 *
 * - Redistribution in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in
 *   the documentation and/or other materials provided with the
 *   distribution.
 *
 * Neither the name of Sun Microsystems, Inc. or the names of
 * contributors may be used to endorse or promote products derived
 * from this software without specific prior written permission.
 *
 * This software is provided "AS IS," without a warranty of any
 * kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND
 * WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY
 * EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN") AND ITS LICENSORS SHALL
 * NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF
 * USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR
 * ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL,
 * CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND
 * REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF THE USE OF OR
 * INABILITY TO USE THIS SOFTWARE, EVEN IF SUN HAS BEEN ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGES.
 *
 * You acknowledge that this software is not designed or intended for
 * use in the design, construction, operation or maintenance of any
 * nuclear facility.
 */
package com.lowagie.text.pdf;

import java.io.IOException;
import java.io.OutputStream;

import com.lowagie.text.ExceptionConverter;

/**
 * A class for performing LZW decoding.
 *
 *
 */
public class LZWDecoder {

    byte stringTable[][];
    byte data[] = null;
    OutputStream uncompData;
    int tableIndex, bitsToGet = 9;
    int bytePointer, bitPointer;
    int nextData = 0;
    int nextBits = 0;

    int andTable[] = {
            511,
            1023,
            2047,
            4095
    };

    public LZWDecoder() {
    }

    /**
     * Method to decode LZW compressed data.
     *
     * @param data The compressed data.
     * @param uncompData Array to return the uncompressed data in.
     */
    public void decode(byte data[], OutputStream uncompData) {

        if (data[0] == (byte) 0x00 && data[1] == (byte) 0x01) {
            throw new RuntimeException("LZW flavour not supported.");
        }

        initializeStringTable();

        this.data = data;
        this.uncompData = uncompData;

        // Initialize pointers
        bytePointer = 0;
        bitPointer = 0;

        nextData = 0;
        nextBits = 0;

        int code, oldCode = 0;
        byte string[];

        while ((code = getNextCode()) != 257) {

            if (code == 256) {

                initializeStringTable();
                code = getNextCode();

                if (code == 257) {
                    break;
                }

                writeString(stringTable[code]);
                oldCode = code;

            } else {

                if (code < tableIndex) {

                    string = stringTable[code];

                    writeString(string);
                    addStringToTable(stringTable[oldCode], string[0]);
                    oldCode = code;

                } else {

                    string = stringTable[oldCode];
                    string = composeString(string, string[0]);
                    writeString(string);
                    addStringToTable(string);
                    oldCode = code;
                }
            }
        }
    }

    /**
     * Initialize the string table.
     */
    public void initializeStringTable() {

        stringTable = new byte[8192][];

        for (int i = 0; i < 256; i++) {
            stringTable[i] = new byte[1];
            stringTable[i][0] = (byte) i;
        }

        tableIndex = 258;
        bitsToGet = 9;
    }

    /**
     * Write out the string just uncompressed.
     */
    public void writeString(byte string[]) {
        try {
            uncompData.write(string);
        } catch (IOException e) {
            throw new ExceptionConverter(e);
        }
    }

    /**
     * Add a new string to the string table.
     */
    public void addStringToTable(byte oldString[], byte newString) {
        int length = oldString.length;
        byte string[] = new byte[length + 1];
        System.arraycopy(oldString, 0, string, 0, length);
        string[length] = newString;

        // Add this new String to the table
        stringTable[tableIndex++] = string;

        if (tableIndex == 511) {
            bitsToGet = 10;
        } else if (tableIndex == 1023) {
            bitsToGet = 11;
        } else if (tableIndex == 2047) {
            bitsToGet = 12;
        }
    }

    /**
     * Add a new string to the string table.
     */
    public void addStringToTable(byte string[]) {

        // Add this new String to the table
        stringTable[tableIndex++] = string;

        if (tableIndex == 511) {
            bitsToGet = 10;
        } else if (tableIndex == 1023) {
            bitsToGet = 11;
        } else if (tableIndex == 2047) {
            bitsToGet = 12;
        }
    }

    /**
     * Append newString to the end of oldString.
     */
    public byte[] composeString(byte oldString[], byte newString) {
        int length = oldString.length;
        byte string[] = new byte[length + 1];
        System.arraycopy(oldString, 0, string, 0, length);
        string[length] = newString;

        return string;
    }

    // Returns the next 9, 10, 11 or 12 bits
    public int getNextCode() {
        // Attempt to get the next code. The exception is caught to make
        // this robust to cases wherein the EndOfInformation code has been
        // omitted from a strip. Examples of such cases have been observed
        // in practice.
        try {
            nextData = (nextData << 8) | (data[bytePointer++] & 0xff);
            nextBits += 8;

            if (nextBits < bitsToGet) {
                nextData = (nextData << 8) | (data[bytePointer++] & 0xff);
                nextBits += 8;
            }

            int code = (nextData >> (nextBits - bitsToGet)) & andTable[bitsToGet - 9];
            nextBits -= bitsToGet;

            return code;
        } catch (ArrayIndexOutOfBoundsException e) {
            // Strip not terminated as expected: return EndOfInformation code.
            return 257;
        }
    }
}