src/main/java/org/apache/pdfbox/jbig2/decoder/huffman/EncodedTable.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.pdfbox.jbig2.decoder.huffman;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.apache.pdfbox.jbig2.JBIG2ImageReader;

import org.apache.pdfbox.jbig2.io.SubInputStream;
import org.apache.pdfbox.jbig2.segments.Table;

/**
 * This class represents a encoded huffman table.
 */
public class EncodedTable extends HuffmanTable
{

    private Table table;

    public EncodedTable(Table table) throws IOException
    {
        this.table = table;
        parseTable();
    }

    public void parseTable() throws IOException
    {

        SubInputStream sis = table.getSubInputStream();

        List<Code> codeTable = new ArrayList<Code>();

        int prefLen, rangeLen, rangeLow;
        int curRangeLow = table.getHtLow();

        /* Annex B.2 5) - decode table lines */
        while (curRangeLow < table.getHtHigh())
        {
            prefLen = (int) sis.readBits(table.getHtPS());
            rangeLen = (int) sis.readBits(table.getHtRS());
            rangeLow = curRangeLow;

            codeTable.add(new Code(prefLen, rangeLen, rangeLow, false));

            curRangeLow += 1 << rangeLen;
        }

        /* Annex B.2 6) */
        prefLen = (int) sis.readBits(table.getHtPS());

        /*
         * Annex B.2 7) - lower range table line
         * 
         * Made some correction. Spec specifies an incorrect variable -> Replaced highPrefLen with lowPrefLen
         */
        rangeLen = 32;
        rangeLow = table.getHtHigh() - 1;
        codeTable.add(new Code(prefLen, rangeLen, rangeLow, true));

        /* Annex B.2 8) */
        prefLen = (int) sis.readBits(table.getHtPS());

        /* Annex B.2 9) - upper range table line */
        rangeLen = 32;
        rangeLow = table.getHtHigh();
        codeTable.add(new Code(prefLen, rangeLen, rangeLow, false));

        /* Annex B.2 10) - out-of-band table line */
        if (table.getHtOOB() == 1)
        {
            prefLen = (int) sis.readBits(table.getHtPS());
            codeTable.add(new Code(prefLen, -1, -1, false));
        }

        if (JBIG2ImageReader.DEBUG)
        {
            System.out.println(codeTableToString(codeTable));
        }

        initTree(codeTable);
    }
}