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Java example source code file (DeflateDecoder.java)

This example Java source code file (DeflateDecoder.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

binarywebsocketframe, bytebuf, codecexception, compositebytebuf, continuationwebsocketframe, deflatedecoder, embeddedchannel, exception, frame_tail, list, override, textwebsocketframe, util, websocketextensiondecoder, websocketframe

The DeflateDecoder.java Java example source code

/*
 * Copyright 2014 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.
 */
package io.netty.handler.codec.http.websocketx.extensions.compression;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.CompositeByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.embedded.EmbeddedChannel;
import io.netty.handler.codec.CodecException;
import io.netty.handler.codec.compression.ZlibCodecFactory;
import io.netty.handler.codec.compression.ZlibWrapper;
import io.netty.handler.codec.http.websocketx.BinaryWebSocketFrame;
import io.netty.handler.codec.http.websocketx.ContinuationWebSocketFrame;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import io.netty.handler.codec.http.websocketx.WebSocketFrame;
import io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionDecoder;

import java.util.List;

/**
 * Deflate implementation of a payload decompressor for
 * <tt>io.netty.handler.codec.http.websocketx.WebSocketFrame.
 */
abstract class DeflateDecoder extends WebSocketExtensionDecoder {

    static final byte[] FRAME_TAIL = new byte[] {0x00, 0x00, (byte) 0xff, (byte) 0xff};

    private final boolean noContext;

    private EmbeddedChannel decoder;

    /**
     * Constructor
     * @param noContext true to disable context takeover.
     */
    public DeflateDecoder(boolean noContext) {
        this.noContext = noContext;
    }

    protected abstract boolean appendFrameTail(WebSocketFrame msg);

    protected abstract int newRsv(WebSocketFrame msg);

    @Override
    protected void decode(ChannelHandlerContext ctx, WebSocketFrame msg, List<Object> out) throws Exception {
        if (decoder == null) {
            if (!(msg instanceof TextWebSocketFrame) && !(msg instanceof BinaryWebSocketFrame)) {
                throw new CodecException("unexpected initial frame type: " + msg.getClass().getName());
            }
            decoder = new EmbeddedChannel(ZlibCodecFactory.newZlibDecoder(ZlibWrapper.NONE));
        }

        boolean readable = msg.content().isReadable();
        decoder.writeInbound(msg.content().retain());
        if (appendFrameTail(msg)) {
            decoder.writeInbound(Unpooled.wrappedBuffer(FRAME_TAIL));
        }

        CompositeByteBuf compositeUncompressedContent = ctx.alloc().compositeBuffer();
        for (;;) {
            ByteBuf partUncompressedContent = decoder.readInbound();
            if (partUncompressedContent == null) {
                break;
            }
            if (!partUncompressedContent.isReadable()) {
                partUncompressedContent.release();
                continue;
            }
            compositeUncompressedContent.addComponent(true, partUncompressedContent);
        }
        // Correctly handle empty frames
        // See https://github.com/netty/netty/issues/4348
        if (readable && compositeUncompressedContent.numComponents() <= 0) {
            compositeUncompressedContent.release();
            throw new CodecException("cannot read uncompressed buffer");
        }

        if (msg.isFinalFragment() && noContext) {
            cleanup();
        }

        WebSocketFrame outMsg;
        if (msg instanceof TextWebSocketFrame) {
            outMsg = new TextWebSocketFrame(msg.isFinalFragment(), newRsv(msg), compositeUncompressedContent);
        } else if (msg instanceof BinaryWebSocketFrame) {
            outMsg = new BinaryWebSocketFrame(msg.isFinalFragment(), newRsv(msg), compositeUncompressedContent);
        } else if (msg instanceof ContinuationWebSocketFrame) {
            outMsg = new ContinuationWebSocketFrame(msg.isFinalFragment(), newRsv(msg),
                    compositeUncompressedContent);
        } else {
            throw new CodecException("unexpected frame type: " + msg.getClass().getName());
        }
        out.add(outMsg);
    }

    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        cleanup();
        super.handlerRemoved(ctx);
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        cleanup();
        super.channelInactive(ctx);
    }

    private void cleanup() {
        if (decoder != null) {
            // Clean-up the previous encoder if not cleaned up correctly.
            if (decoder.finish()) {
                for (;;) {
                    ByteBuf buf = decoder.readOutbound();
                    if (buf == null) {
                        break;
                    }
                    // Release the buffer
                    buf.release();
                }
            }
            decoder = null;
        }
    }
}

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