src/main/java/org/apache/pdfbox/jbig2/decoder/huffman/InternalNode.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 javax.imageio.stream.ImageInputStream;

import org.apache.pdfbox.jbig2.JBIG2ImageReader;
import org.apache.pdfbox.jbig2.decoder.huffman.HuffmanTable.Code;

/**
 * This class represents an internal node of a huffman tree. It contains two child nodes.
 */
class InternalNode extends Node
{
    private final int depth;

    private Node zero;
    private Node one;

    protected InternalNode()
    {
        depth = 0;
    }

    protected InternalNode(int depth)
    {
        this.depth = depth;
    }

    protected void append(Code c)
    {
        if (JBIG2ImageReader.DEBUG)
            System.out.println("I'm working on " + c.toString());

        // ignore unused codes
        if (c.prefixLength == 0)
            return;

        int shift = c.prefixLength - 1 - depth;

        if (shift < 0)
            throw new IllegalArgumentException("Negative shifting is not possible.");

        int bit = (c.code >> shift) & 1;
        if (shift == 0)
        {
            if (c.rangeLength == -1)
            {
                // the child will be a OutOfBand
                if (bit == 1)
                {
                    if (one != null)
                        throw new IllegalStateException("already have a OOB for " + c);
                    one = new OutOfBandNode(c);
                }
                else
                {
                    if (zero != null)
                        throw new IllegalStateException("already have a OOB for " + c);
                    zero = new OutOfBandNode(c);
                }
            }
            else
            {
                // the child will be a ValueNode
                if (bit == 1)
                {
                    if (one != null)
                        throw new IllegalStateException("already have a ValueNode for " + c);
                    one = new ValueNode(c);
                }
                else
                {
                    if (zero != null)
                        throw new IllegalStateException("already have a ValueNode for " + c);
                    zero = new ValueNode(c);
                }
            }
        }
        else
        {
            // the child will be an InternalNode
            if (bit == 1)
            {
                if (one == null)
                    one = new InternalNode(depth + 1);
                ((InternalNode) one).append(c);
            }
            else
            {
                if (zero == null)
                    zero = new InternalNode(depth + 1);
                ((InternalNode) zero).append(c);
            }
        }
    }

    @Override
    protected long decode(ImageInputStream iis) throws IOException
    {
        int b = iis.readBit();
        Node n = b == 0 ? zero : one;
        return n.decode(iis);
    }

    @Override
    public String toString()
    {
        StringBuilder sb = new StringBuilder("\n");

        pad(sb);
        sb.append("0: ").append(zero).append("\n");
        pad(sb);
        sb.append("1: ").append(one).append("\n");

        return sb.toString();
    }

    private void pad(StringBuilder sb)
    {
        for (int i = 0; i < depth; i++)
            sb.append("   ");
    }
}