ByteToMessageDecoder.java — netty Source File

Source Code

/*
 * Copyright 2012 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;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufAllocator;
import io.netty.buffer.CompositeByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelConfig;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.socket.ChannelInputShutdownEvent;
import io.netty.util.IllegalReferenceCountException;
import io.netty.util.internal.ObjectUtil;
import io.netty.util.internal.StringUtil;

import java.util.ArrayDeque;
import java.util.List;
import java.util.Queue;

import static io.netty.buffer.Unpooled.EMPTY_BUFFER;
import static io.netty.util.internal.ObjectUtil.checkPositive;

/**
 * {@link ChannelInboundHandlerAdapter} which decodes bytes in a stream-like fashion from one {@link ByteBuf} to
 * another Message type.
 * <p>
 * For example here is an implementation which reads all readable bytes from
 * the input {@link ByteBuf} and create a new {@link ByteBuf}.
 *
 * <pre>
 *     public class SquareDecoder extends {@link ByteToMessageDecoder} {
 *         {@code @Override}
 *         public void decode({@link ChannelHandlerContext} ctx, {@link ByteBuf} in, List&lt;Object&gt; out)
 *                 throws {@link Exception} {
 *             out.add(in.readBytes(in.readableBytes()));
 *         }
 *     }
 * </pre>
 *
 * <h3>Frame detection</h3>
 * <p>
 * Generally frame detection should be handled earlier in the pipeline by adding a
 * {@link DelimiterBasedFrameDecoder}, {@link FixedLengthFrameDecoder}, {@link LengthFieldBasedFrameDecoder},
 * or {@link LineBasedFrameDecoder}.
 * <p>
 * If a custom frame decoder is required, then one needs to be careful when implementing
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