src/main/java/org/apache/pdfbox/jbig2/decoder/arithmetic/CX.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.arithmetic;

/**
 * CX represents the context used by arithmetic decoding and arithmetic integer decoding. It selects the probability
 * estimate and statistics used during decoding procedure.
 */
public final class CX
{
    private int index;

    private final byte cx[];
    private final byte mps[];

    /**
     * @param size - Amount of context values.
     * @param index - Start index.
     */
    public CX(int size, int index)
    {
        this.index = index;
        cx = new byte[size];
        mps = new byte[size];
    }

    protected int cx()
    {
        return cx[index] & 0x7f;
    }

    protected void setCx(int value)
    {
        cx[index] = (byte) (value & 0x7f);
    }

    /**
     * @return The decision. Possible values are {@code 0} or {@code 1}.
     */
    protected byte mps()
    {
        return mps[index];
    }

    /**
     * Flips the bit in actual "more predictable symbol" array element.
     */
    protected void toggleMps()
    {
        mps[index] ^= 1;
    }

    protected int getIndex()
    {
        return index;
    }

    public void setIndex(int index)
    {
        this.index = index;
    }
}