QpackHuffmanDecoder.java — netty Source File

Source Code

/*
 * Copyright 2020 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.http3;

import io.netty.buffer.ByteBuf;
import io.netty.util.AsciiString;
import io.netty.util.ByteProcessor;

final class QpackHuffmanDecoder implements ByteProcessor {

    /* Scroll to the bottom! */

    private static final byte HUFFMAN_COMPLETE = 1;
    private static final byte HUFFMAN_EMIT_SYMBOL = 1 << 1;
    private static final byte HUFFMAN_FAIL = 1 << 2;

    private static final int HUFFMAN_COMPLETE_SHIFT = HUFFMAN_COMPLETE << 8;
    private static final int HUFFMAN_EMIT_SYMBOL_SHIFT = HUFFMAN_EMIT_SYMBOL << 8;
    private static final int HUFFMAN_FAIL_SHIFT = HUFFMAN_FAIL << 8;

    /**
     * A table of byte tuples (state, flags, output).   They are packed together as:
     * <p>
     * state<<16 + flags<<8 + output
     */
    private static final int[] HUFFS = new int[] {
            // Node 0 (Root Node, never emits symbols.)
            4 << 16,
            5 << 16,
            7 << 16,
            8 << 16,
            11 << 16,
            12 << 16,
            16 << 16,
            19 << 16,
            25 << 16,
            28 << 16,
            32 << 16,
            35 << 16,
            42 << 16,
            49 << 16,
            57 << 16,
            (64 << 16) + (HUFFMAN_COMPLETE << 8),

            // Node 1
            ((HUFFMAN_COMPLETE | HUFFMAN_EMIT_SYMBOL) << 8) + 48,
            ((HUFFMAN_COMPLETE | HUFFMAN_EMIT_SYMBOL) << 8) + 49,
// ... (4658 more lines)