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rar decompression library in plain java
There is a newer version: 7.5.5
/*
 * Copyright (c) 2007 innoSysTec (R) GmbH, Germany. All rights reserved.
 * Original author: Edmund Wagner
 * Creation date: 31.05.2007
 *
 * Source: $HeadURL$
 * Last changed: $LastChangedDate$
 *
 * the unrar licence applies to all junrar source and binary distributions
 * you are not allowed to use this source to re-create the RAR compression algorithm
 *
 * Here some html entities which can be used for escaping javadoc tags:
 * "&":  "&" or "&"
 * "<":  "<" or "<"
 * ">":  ">" or ">"
 * "@":  "@"
 */
package com.github.junrar.unpack.ppm;

import java.io.IOException;

import com.github.junrar.exception.RarException;
import com.github.junrar.unpack.Unpack;


/**
 * DOCUMENT ME
 *
 * @author $LastChangedBy$
 * @version $LastChangedRevision$
 */
public class RangeCoder {
    public static final int TOP = 1 << 24;

    public static final int BOT = 1 << 15;

    private static final long uintMask = 0xFFFFffffL;

    // uint low, code, range;
    private long low, code, range;

    private final SubRange subRange = new SubRange();

    private Unpack unpackRead;

    public SubRange getSubRange() {
        return subRange;
    }

    public void initDecoder(Unpack unpackRead) throws IOException, RarException {
        this.unpackRead = unpackRead;

        low = code = 0L;
        range = 0xFFFFffffL;
        for (int i = 0; i < 4; i++) {
            code = ((code << 8) | getChar()) & uintMask;
        }
    }

    public int getCurrentCount() {
        range = (range / subRange.getScale()) & uintMask;
        return (int) ((code - low) / (range));
    }

    public long getCurrentShiftCount(int SHIFT) {
        range = range >>> SHIFT;
        return ((code - low) / (range)) & uintMask;
    }

    public void decode() {
        low = (low + (range * subRange.getLowCount())) & uintMask;
        range = (range * (subRange.getHighCount() - subRange.getLowCount())) & uintMask;
    }

    private int getChar() throws IOException, RarException {
        return (unpackRead.getChar());
    }

    public void ariDecNormalize() throws IOException, RarException {
//        while ((low ^ (low + range)) < TOP || range < BOT && ((range = -low & (BOT - 1)) != 0 ? true : true))
//        {
//            code = ((code << 8) | unpackRead.getChar()&0xff)&uintMask;
//            range = (range << 8)&uintMask;
//            low = (low << 8)&uintMask;
//        }

        // Rewrote for clarity
        boolean c2 = false;
        while ((low ^ (low + range)) < TOP || (c2 = range < BOT)) {
            if (c2) {
                range = (-low & (BOT - 1)) & uintMask;
                c2 = false;
            }
            code = ((code << 8) | getChar()) & uintMask;
            range = (range << 8) & uintMask;
            low = (low << 8) & uintMask;
        }
    }

    // Debug
    public String toString() {
        StringBuilder buffer = new StringBuilder();
        buffer.append("RangeCoder[");
        buffer.append("\n  low=");
        buffer.append(low);
        buffer.append("\n  code=");
        buffer.append(code);
        buffer.append("\n  range=");
        buffer.append(range);
        buffer.append("\n  subrange=");
        buffer.append(subRange);
        buffer.append("]");
        return buffer.toString();
    }

    public static class SubRange {
        // uint LowCount, HighCount, scale;
        private long lowCount, highCount, scale;

        public long getHighCount() {
            return highCount;
        }

        public void setHighCount(long highCount) {
            this.highCount = highCount & uintMask;
        }

        public long getLowCount() {
            return lowCount & uintMask;
        }

        public void setLowCount(long lowCount) {
            this.lowCount = lowCount & uintMask;
        }

        public long getScale() {
            return scale;
        }

        public void setScale(long scale) {
            this.scale = scale & uintMask;
        }

        public void incScale(int dScale) {
            setScale(getScale() + dScale);
        }

        // Debug
        public String toString() {
            StringBuilder buffer = new StringBuilder();
            buffer.append("SubRange[");
            buffer.append("\n  lowCount=");
            buffer.append(lowCount);
            buffer.append("\n  highCount=");
            buffer.append(highCount);
            buffer.append("\n  scale=");
            buffer.append(scale);
            buffer.append("]");
            return buffer.toString();
        }
    }
}