Bzip2HuffmanStageDecoder Class — netty Architecture

Source Code

codec-compression/src/main/java/io/netty/handler/codec/compression/Bzip2HuffmanStageDecoder.java lines 25–203

final class Bzip2HuffmanStageDecoder {
    /**
     * A reader that provides bit-level reads.
     */
    private final Bzip2BitReader reader;

    /**
     * The Huffman table number to use for each group of 50 symbols.
     */
    byte[] selectors;

    /**
     * The minimum code length for each Huffman table.
     */
    private final int[] minimumLengths;

    /**
     * An array of values for each Huffman table that must be subtracted from the numerical value of
     * a Huffman code of a given bit length to give its canonical code index.
     */
    private final int[][] codeBases;

    /**
     * An array of values for each Huffman table that gives the highest numerical value of a Huffman
     * code of a given bit length.
     */
    private final int[][] codeLimits;

    /**
     * A mapping for each Huffman table from canonical code index to output symbol.
     */
    private final int[][] codeSymbols;

    /**
     * The Huffman table for the current group.
     */
    private int currentTable;

    /**
     * The index of the current group within the selectors array.
     */
    private int groupIndex = -1;

    /**
     * The byte position within the current group. A new group is selected every 50 decoded bytes.
     */
    private int groupPosition = -1;

    /**
     * Total number of used Huffman tables in range 2..6.
     */
    final int totalTables;

    /**
     * The total number of codes (uniform for each table).
     */
    final int alphabetSize;

    /**
     * Table for Move To Front transformations.
     */
    final Bzip2MoveToFrontTable tableMTF = new Bzip2MoveToFrontTable();

    // For saving state if end of current ByteBuf was reached
    int currentSelector;

    /**
     * The Canonical Huffman code lengths for each table.
     */
    final byte[][] tableCodeLengths;

    // For saving state if end of current ByteBuf was reached
    int currentGroup;
    int currentLength = -1;
    int currentAlpha;
    boolean modifyLength;

    Bzip2HuffmanStageDecoder(final Bzip2BitReader reader, final int totalTables, final int alphabetSize) {
        this.reader = reader;
        this.totalTables = totalTables;
        this.alphabetSize = alphabetSize;