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This artifact provides a single jar that contains all classes required to use remote Jakarta Enterprise Beans and Jakarta Messaging, including all dependencies. It is intended for use by those not using maven, maven users should just import the Jakarta Enterprise Beans and Jakarta Messaging BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up with different versions on classes on the class path).

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/*
 * Copyright 2015 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:
 *
 *   http://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.
 */

/*
 * Copyright 2014 Twitter, Inc.
 *
 * Licensed 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
 *
 *     http://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.http2;

import io.netty.buffer.ByteBuf;
import io.netty.util.AsciiString;
import io.netty.util.ByteProcessor;
import io.netty.util.internal.ObjectUtil;
import io.netty.util.internal.ThrowableUtil;

import static io.netty.handler.codec.http2.Http2Error.COMPRESSION_ERROR;
import static io.netty.handler.codec.http2.Http2Exception.connectionError;

final class HpackHuffmanDecoder {

    private static final Http2Exception EOS_DECODED = ThrowableUtil.unknownStackTrace(
            connectionError(COMPRESSION_ERROR, "HPACK - EOS Decoded"), HpackHuffmanDecoder.class, "decode(..)");
    private static final Http2Exception INVALID_PADDING = ThrowableUtil.unknownStackTrace(
            connectionError(COMPRESSION_ERROR, "HPACK - Invalid Padding"), HpackHuffmanDecoder.class, "decode(..)");

    private static final Node ROOT = buildTree(HpackUtil.HUFFMAN_CODES, HpackUtil.HUFFMAN_CODE_LENGTHS);

    private final DecoderProcessor processor;

    HpackHuffmanDecoder(int initialCapacity) {
        processor = new DecoderProcessor(initialCapacity);
    }

    /**
     * Decompresses the given Huffman coded string literal.
     *
     * @param buf the string literal to be decoded
     * @return the output stream for the compressed data
     * @throws Http2Exception EOS Decoded
     */
    public AsciiString decode(ByteBuf buf, int length) throws Http2Exception {
        processor.reset();
        buf.forEachByte(buf.readerIndex(), length, processor);
        buf.skipBytes(length);
        return processor.end();
    }

    private static final class Node {

        private final int symbol;      // terminal nodes have a symbol
        private final int bits;        // number of bits matched by the node
        private final Node[] children; // internal nodes have children

        /**
         * Construct an internal node
         */
        Node() {
            symbol = 0;
            bits = 8;
            children = new Node[256];
        }

        /**
         * Construct a terminal node
         *
         * @param symbol the symbol the node represents
         * @param bits the number of bits matched by this node
         */
        Node(int symbol, int bits) {
            assert bits > 0 && bits <= 8;
            this.symbol = symbol;
            this.bits = bits;
            children = null;
        }

        private boolean isTerminal() {
            return children == null;
        }
    }

    private static Node buildTree(int[] codes, byte[] lengths) {
        Node root = new Node();
        for (int i = 0; i < codes.length; i++) {
            insert(root, i, codes[i], lengths[i]);
        }
        return root;
    }

    private static void insert(Node root, int symbol, int code, byte length) {
        // traverse tree using the most significant bytes of code
        Node current = root;
        while (length > 8) {
            if (current.isTerminal()) {
                throw new IllegalStateException("invalid Huffman code: prefix not unique");
            }
            length -= 8;
            int i = (code >>> length) & 0xFF;
            if (current.children[i] == null) {
                current.children[i] = new Node();
            }
            current = current.children[i];
        }

        Node terminal = new Node(symbol, length);
        int shift = 8 - length;
        int start = (code << shift) & 0xFF;
        int end = 1 << shift;
        for (int i = start; i < start + end; i++) {
            current.children[i] = terminal;
        }
    }

    private static final class DecoderProcessor implements ByteProcessor {
        private final int initialCapacity;
        private byte[] bytes;
        private int index;
        private Node node;
        private int current;
        private int currentBits;
        private int symbolBits;

        DecoderProcessor(int initialCapacity) {
            this.initialCapacity = ObjectUtil.checkPositive(initialCapacity, "initialCapacity");
        }

        void reset() {
            node = ROOT;
            current = 0;
            currentBits = 0;
            symbolBits = 0;
            bytes = new byte[initialCapacity];
            index = 0;
        }

        /*
         * The idea here is to consume whole bytes at a time rather than individual bits. node
         * represents the Huffman tree, with all bit patterns denormalized as 256 children. Each
         * child represents the last 8 bits of the huffman code. The parents of each child each
         * represent the successive 8 bit chunks that lead up to the last most part. 8 bit bytes
         * from buf are used to traverse these tree until a terminal node is found.
         *
         * current is a bit buffer. The low order bits represent how much of the huffman code has
         * not been used to traverse the tree. Thus, the high order bits are just garbage.
         * currentBits represents how many of the low order bits of current are actually valid.
         * currentBits will vary between 0 and 15.
         *
         * symbolBits is the number of bits of the symbol being decoded, *including* all those of
         * the parent nodes. symbolBits tells how far down the tree we are. For example, when
         * decoding the invalid sequence {0xff, 0xff}, currentBits will be 0, but symbolBits will be
         * 16. This is used to know if buf ended early (before consuming a whole symbol) or if
         * there is too much padding.
         */
        @Override
        public boolean process(byte value) throws Http2Exception {
            current = (current << 8) | (value & 0xFF);
            currentBits += 8;
            symbolBits += 8;
            // While there are unconsumed bits in current, keep consuming symbols.
            do {
                node = node.children[(current >>> (currentBits - 8)) & 0xFF];
                currentBits -= node.bits;
                if (node.isTerminal()) {
                    if (node.symbol == HpackUtil.HUFFMAN_EOS) {
                        throw EOS_DECODED;
                    }
                    append(node.symbol);
                    node = ROOT;
                    // Upon consuming a whole symbol, reset the symbol bits to the number of bits
                    // left over in the byte.
                    symbolBits = currentBits;
                }
            } while (currentBits >= 8);
            return true;
        }

        AsciiString end() throws Http2Exception {
            /*
             * We have consumed all the bytes in buf, but haven't consumed all the symbols. We may be on
             * a partial symbol, so consume until there is nothing left. This will loop at most 2 times.
             */
            while (currentBits > 0) {
                node = node.children[(current << (8 - currentBits)) & 0xFF];
                if (node.isTerminal() && node.bits <= currentBits) {
                    if (node.symbol == HpackUtil.HUFFMAN_EOS) {
                        throw EOS_DECODED;
                    }
                    currentBits -= node.bits;
                    append(node.symbol);
                    node = ROOT;
                    symbolBits = currentBits;
                } else {
                    break;
                }
            }

            // Section 5.2. String Literal Representation
            // A padding strictly longer than 7 bits MUST be treated as a decoding error.
            // Padding not corresponding to the most significant bits of the code
            // for the EOS symbol (0xFF) MUST be treated as a decoding error.
            int mask = (1 << symbolBits) - 1;
            if (symbolBits > 7 || (current & mask) != mask) {
                throw INVALID_PADDING;
            }

            return new AsciiString(bytes, 0, index, false);
        }

        private void append(int i) {
            if (bytes.length == index) {
                // Choose an expanding strategy depending on how big the buffer already is.
                // 1024 was choosen as a good guess and we may be able to investigate more if there are better choices.
                // See also https://github.com/netty/netty/issues/6846
                final int newLength = bytes.length >= 1024 ? bytes.length + initialCapacity : bytes.length << 1;
                byte[] newBytes = new byte[newLength];
                System.arraycopy(bytes, 0, newBytes, 0, bytes.length);
                bytes = newBytes;
            }
            bytes[index++] = (byte) i;
        }
    }
}




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