ReplayingDecoder.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.Unpooled;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelPipeline;
import io.netty.util.Signal;
import io.netty.util.internal.StringUtil;

import java.util.List;

/**
 * A specialized variation of {@link ByteToMessageDecoder} which enables implementation
 * of a non-blocking decoder in the blocking I/O paradigm.
 * <p>
 * The biggest difference between {@link ReplayingDecoder} and
 * {@link ByteToMessageDecoder} is that {@link ReplayingDecoder} allows you to
 * implement the {@code decode()} and {@code decodeLast()} methods just like
 * all required bytes were received already, rather than checking the
 * availability of the required bytes.  For example, the following
 * {@link ByteToMessageDecoder} implementation:
 * <pre>
 * public class IntegerHeaderFrameDecoder extends {@link ByteToMessageDecoder} {
 *
 *   {@code @Override}
 *   protected void decode({@link ChannelHandlerContext} ctx,
 *                           {@link ByteBuf} buf, List&lt;Object&gt; out) throws Exception {
 *
 *     if (buf.readableBytes() &lt; 4) {
 *        return;
 *     }
 *
 *     buf.markReaderIndex();
 *     int length = buf.readInt();
 *
 *     if (buf.readableBytes() &lt; length) {
 *        buf.resetReaderIndex();
 *        return;
 *     }
 *
 *     out.add(buf.readBytes(length));
 *   }
 * }
 * </pre>
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