/*
 * Copyright (c) 2011, 2017 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package org.glassfish.grizzly.compression.lzma.impl.rangecoder;

import org.glassfish.grizzly.compression.lzma.LZMADecoder;

BitTreeDecoder
Author:
Igor Pavlov/**
 * BitTreeDecoder
 *
 * @author Igor Pavlov
 */
public class BitTreeDecoder {

    final short[] Models;
    final int NumBitLevels;

    // decode state
    int decodeMethodState;
    int m;
    int bitIndex;

    // reverseDecode state
    int reverseDecodeMethodState;
    int symbol;

    public BitTreeDecoder(int numBitLevels) {
        NumBitLevels = numBitLevels;
        Models = new short[1 << numBitLevels];
    }

    public void init() {
        decodeMethodState = 0;
        reverseDecodeMethodState = 0;

        RangeDecoder.initBitModels(Models);
    }

    public boolean decode(LZMADecoder.LZMAInputState decodeState,
            RangeDecoder rangeDecoder) throws java.io.IOException {

        do {
            switch(decodeMethodState) {
                case 0:
                {
                    m = 1;
                    bitIndex = NumBitLevels;
                    decodeMethodState = 1;
                }
                case 1:
                {
                    if (bitIndex == 0) {
                        decodeMethodState = 3;
                        continue;
                    }

                    decodeMethodState = 2;
                }
                case 2:
                {
                    if (!rangeDecoder.decodeBit(decodeState, Models, m)) {
                        return false;
                    }
                    
                    m = (m << 1) + decodeState.lastMethodResult;
                    bitIndex--;

                    decodeMethodState = 1;
                    continue;
                }
                case 3:
                {
                    decodeState.lastMethodResult = m - (1 << NumBitLevels);
                    decodeMethodState = 0;
                    return true;
                }

            }
        } while (true);
    }

    public boolean reverseDecode(LZMADecoder.LZMAInputState decodeState,
            RangeDecoder rangeDecoder) throws java.io.IOException {
        
        do {
            switch(reverseDecodeMethodState) {
                case 0:
                {
                    m = 1;
                    symbol = 0;
                    bitIndex = 0;
                    reverseDecodeMethodState = 1;
                }
                case 1:
                {
                    if (bitIndex >= NumBitLevels) {
                        reverseDecodeMethodState = 3;
                        continue;
                    }

                    reverseDecodeMethodState = 2;
                }
                case 2:
                {
                    if (!rangeDecoder.decodeBit(decodeState, Models, m)) {
                        return false;
                    }

                    final int bit = decodeState.lastMethodResult;
                    m <<= 1;
                    m += bit;
                    symbol |= (bit << bitIndex);

                    bitIndex++;
                    reverseDecodeMethodState = 1;
                    continue;
                }
                case 3:
                {
                    decodeState.lastMethodResult = symbol;
                    reverseDecodeMethodState = 0;
                    return true;
                }

            }
        } while (true);
    }

    public static boolean reverseDecode(LZMADecoder.LZMAInputState decodeState,
            short[] Models, int startIndex, RangeDecoder rangeDecoder,
            int NumBitLevels) throws java.io.IOException {

        do {
            switch(decodeState.staticReverseDecodeMethodState) {
                case 0:
                {
                    decodeState.staticM = 1;
                    decodeState.staticSymbol = 0;
                    decodeState.staticBitIndex = 0;
                    decodeState.staticReverseDecodeMethodState = 1;
                }
                case 1:
                {
                    if (decodeState.staticBitIndex >= NumBitLevels) {
                        decodeState.staticReverseDecodeMethodState = 3;
                        continue;
                    }

                    decodeState.staticReverseDecodeMethodState = 2;
                }
                case 2:
                {
                    if (!rangeDecoder.decodeBit(decodeState, Models,
                            startIndex + decodeState.staticM)) {
                        return false;
                    }

                    final int bit = decodeState.lastMethodResult;
                    decodeState.staticM <<= 1;
                    decodeState.staticM += bit;
                    decodeState.staticSymbol |= (bit << decodeState.staticBitIndex);

                    decodeState.staticBitIndex++;
                    decodeState.staticReverseDecodeMethodState = 1;
                    continue;
                }
                case 3:
                {
                    decodeState.lastMethodResult = decodeState.staticSymbol;
                    decodeState.staticReverseDecodeMethodState = 0;
                    return true;
                }

            }
        } while (true);
    }
}