/*

 * Copyright (c) 2005, 2015, 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.

     */

    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.

     */

    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.

     */

    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 <code>newString</code> to the end of <code>oldString</code>.

     */

    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;

        }

    }

}