ChunkedWriteHandler.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.stream;

import static io.netty.util.internal.ObjectUtil.checkPositive;

import io.netty.buffer.ByteBufAllocator;
import io.netty.buffer.Unpooled;
import io.netty.channel.Channel;
import io.netty.channel.ChannelDuplexHandler;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.ChannelProgressivePromise;
import io.netty.channel.ChannelPromise;
import io.netty.util.ReferenceCountUtil;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;

import java.nio.channels.ClosedChannelException;
import java.util.ArrayDeque;
import java.util.Queue;

/**
 * A {@link ChannelHandler} that adds support for writing a large data stream
 * asynchronously neither spending a lot of memory nor getting
 * {@link OutOfMemoryError}.  Large data streaming such as file
 * transfer requires complicated state management in a {@link ChannelHandler}
 * implementation.  {@link ChunkedWriteHandler} manages such complicated states
 * so that you can send a large data stream without difficulties.
 * <p>
 * To use {@link ChunkedWriteHandler} in your application, you have to insert
 * a new {@link ChunkedWriteHandler} instance:
 * <pre>
 * {@link ChannelPipeline} p = ...;
 * p.addLast("streamer", <b>new {@link ChunkedWriteHandler}()</b>);
 * p.addLast("handler", new MyHandler());
 * </pre>
 * Once inserted, you can write a {@link ChunkedInput} so that the
 * {@link ChunkedWriteHandler} can pick it up and fetch the content of the
 * stream chunk by chunk and write the fetched chunk downstream:
 * <pre>
 * {@link Channel} ch = ...;
 * ch.write(new {@link ChunkedFile}(new File("video.mkv"));
 * </pre>
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