/*
 * Copyright (c) 2005, 2018, 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.tiff;

import java.io.IOException;
import javax.imageio.IIOException;

class TIFFLZWUtil {
    public TIFFLZWUtil() {
    }

    byte[] srcData;
    int srcIndex;

    byte[] dstData;
    int dstIndex = 0;

    byte[][] stringTable;
    int tableIndex, bitsToGet = 9;

    int nextData = 0;
    int nextBits = 0;

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

    public byte[] decode(byte[] data, int predictor, int samplesPerPixel,
                         int width, int height) throws IOException {
        if (data[0] == (byte)0x00 && data[1] == (byte)0x01) {
            throw new IIOException("TIFF 5.0-style LZW compression is not supported!");
        }

        this.srcData = data;
        this.srcIndex = 0;
        this.nextData = 0;
        this.nextBits = 0;

        this.dstData = new byte[8192];
        this.dstIndex = 0;

        initializeStringTable();

        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;
                }
            }
        }

        if (predictor == 2) {

            int count;
            for (int j = 0; j < height; j++) {

                count = samplesPerPixel * (j * width + 1);

                for (int i = samplesPerPixel; i < width * samplesPerPixel; i++) {

                    dstData[count] += dstData[count - samplesPerPixel];
                    count++;
                }
            }
        }

        byte[] newDstData = new byte[dstIndex];
        System.arraycopy(dstData, 0, newDstData, 0, dstIndex);
        return newDstData;
    }

    
Initialize the string table.
/** * Initialize the string table. */
public void initializeStringTable() { stringTable = new byte[4096][]; for (int i = 0; i < 256; i++) { stringTable[i] = new byte[1]; stringTable[i][0] = (byte)i; } tableIndex = 258; bitsToGet = 9; } private void ensureCapacity(int bytesToAdd) { if (dstIndex + bytesToAdd > dstData.length) { byte[] newDstData = new byte[Math.max((int)(dstData.length*1.2f), dstIndex + bytesToAdd)]; System.arraycopy(dstData, 0, newDstData, 0, dstData.length); dstData = newDstData; } }
Write out the string just uncompressed.
/** * Write out the string just uncompressed. */
public void writeString(byte[] string) { ensureCapacity(string.length); for (int i = 0; i < string.length; i++) { dstData[dstIndex++] = string[i]; } }
Add a new string to the string table.
/** * 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.
/** * 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.
/** * Append {@code newString} to the end of {@code 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) | (srcData[srcIndex++] & 0xff); nextBits += 8; if (nextBits < bitsToGet) { nextData = (nextData << 8) | (srcData[srcIndex++] & 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; } } }