Bzip2MTFAndRLE2StageEncoder.java — netty Source File

Source Code

/*
 * Copyright 2014 The Netty Project
 *
 * The Netty Project 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:
 *
 *   https://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 io.netty.handler.codec.compression;

import static io.netty.handler.codec.compression.Bzip2Constants.HUFFMAN_MAX_ALPHABET_SIZE;
import static io.netty.handler.codec.compression.Bzip2Constants.HUFFMAN_SYMBOL_RUNA;
import static io.netty.handler.codec.compression.Bzip2Constants.HUFFMAN_SYMBOL_RUNB;

/**
 * An encoder for the Bzip2 Move To Front Transform and Run-Length Encoding[2] stages.<br>
 * Although conceptually these two stages are separate, it is computationally efficient to perform
 * them in one pass.
 */
final class Bzip2MTFAndRLE2StageEncoder {
    /**
     * The Burrows-Wheeler transformed block.
     */
    private final int[] bwtBlock;

    /**
     * Actual length of the data in the {@link #bwtBlock} array.
     */
    private final int bwtLength;

    /**
     * At each position, {@code true} if the byte value with that index is present within the block,
     * otherwise {@code false}.
     */
    private final boolean[] bwtValuesPresent;

    /**
     * The output of the Move To Front Transform and Run-Length Encoding[2] stages.
     */
    private final char[] mtfBlock;

    /**
     * The actual number of values contained in the {@link #mtfBlock} array.
     */
    private int mtfLength;

    /**
     * The global frequencies of values within the {@link #mtfBlock} array.
     */
    private final int[] mtfSymbolFrequencies = new int[HUFFMAN_MAX_ALPHABET_SIZE];

    /**
     * The encoded alphabet size.
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