Bzip2HuffmanStageEncoder.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 io.netty.buffer.ByteBuf;

import java.util.Arrays;

import static io.netty.handler.codec.compression.Bzip2Constants.HUFFMAN_ENCODE_MAX_CODE_LENGTH;
import static io.netty.handler.codec.compression.Bzip2Constants.HUFFMAN_GROUP_RUN_LENGTH;

/**
 * An encoder for the Bzip2 Huffman encoding stage.
 */
final class Bzip2HuffmanStageEncoder {
    /**
     * Used in initial Huffman table generation.
     */
    private static final int HUFFMAN_HIGH_SYMBOL_COST = 15;

    /**
     * The {@link Bzip2BitWriter} to which the Huffman tables and data is written.
     */
    private final Bzip2BitWriter writer;

    /**
     * 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 final int mtfLength;

    /**
     * The number of unique values in the {@link #mtfBlock} array.
     */
    private final int mtfAlphabetSize;

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

    /**
     * The Canonical Huffman code lengths for each table.
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