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Access to the Neo4j graph database through Java

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/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * 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 org.neo4j.driver.internal.async.inbound;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufUtil;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.LengthFieldBasedFrameDecoder;

import org.neo4j.driver.internal.logging.ChannelActivityLogger;
import org.neo4j.driver.Logger;
import org.neo4j.driver.Logging;

public class ChunkDecoder extends LengthFieldBasedFrameDecoder
{
    private static final int MAX_FRAME_BODY_LENGTH = 0xFFFF;
    private static final int LENGTH_FIELD_OFFSET = 0;
    private static final int LENGTH_FIELD_LENGTH = 2;
    private static final int LENGTH_ADJUSTMENT = 0;
    private static final int INITIAL_BYTES_TO_STRIP = LENGTH_FIELD_LENGTH;
    private static final int MAX_FRAME_LENGTH = LENGTH_FIELD_LENGTH + MAX_FRAME_BODY_LENGTH;

    private final Logging logging;
    private Logger log;

    public ChunkDecoder( Logging logging )
    {
        super( MAX_FRAME_LENGTH, LENGTH_FIELD_OFFSET, LENGTH_FIELD_LENGTH, LENGTH_ADJUSTMENT, INITIAL_BYTES_TO_STRIP );
        this.logging = logging;
    }

    @Override
    public void handlerAdded( ChannelHandlerContext ctx )
    {
        log = new ChannelActivityLogger( ctx.channel(), logging, getClass() );
    }

    @Override
    protected void handlerRemoved0( ChannelHandlerContext ctx )
    {
        log = null;
    }

    @Override
    protected ByteBuf extractFrame( ChannelHandlerContext ctx, ByteBuf buffer, int index, int length )
    {
        if ( log.isTraceEnabled() )
        {
            int originalReaderIndex = buffer.readerIndex();
            int readerIndexWithChunkHeader = originalReaderIndex - INITIAL_BYTES_TO_STRIP;
            int lengthWithChunkHeader = INITIAL_BYTES_TO_STRIP + length;
            String hexDump = ByteBufUtil.hexDump( buffer, readerIndexWithChunkHeader, lengthWithChunkHeader );
            log.trace( "S: %s", hexDump );
        }
        return super.extractFrame( ctx, buffer, index, length );
    }
}