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Java example source code file (PerMessageDeflateDecoder.java)

This example Java source code file (PerMessageDeflateDecoder.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, continuationwebsocketframe, exception, list, override, permessagedeflatedecoder, textwebsocketframe, util, websocketframe

The PerMessageDeflateDecoder.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.channel.ChannelHandlerContext;
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.WebSocketExtension;

import java.util.List;

/**
 * Per-message implementation of deflate decompressor.
 */
class PerMessageDeflateDecoder extends DeflateDecoder {

    private boolean compressing;

    /**
     * Constructor
     * @param noContext true to disable context takeover.
     */
    public PerMessageDeflateDecoder(boolean noContext) {
        super(noContext);
    }

    @Override
    public boolean acceptInboundMessage(Object msg) throws Exception {
        return ((msg instanceof TextWebSocketFrame ||
                 msg instanceof BinaryWebSocketFrame) &&
                    (((WebSocketFrame) msg).rsv() & WebSocketExtension.RSV1) > 0) ||
                (msg instanceof ContinuationWebSocketFrame && compressing);
    }

    @Override
    protected int newRsv(WebSocketFrame msg) {
        return (((WebSocketFrame) msg).rsv() & WebSocketExtension.RSV1) > 0 ?
                msg.rsv() ^ WebSocketExtension.RSV1 : msg.rsv();
    }

    @Override
    protected boolean appendFrameTail(WebSocketFrame msg) {
        return msg.isFinalFragment();
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, WebSocketFrame msg,
        List<Object> out) throws Exception {
        super.decode(ctx, msg, out);

        if (msg.isFinalFragment()) {
            compressing = false;
        } else if (msg instanceof TextWebSocketFrame || msg instanceof BinaryWebSocketFrame) {
            compressing = true;
        }
    }
}

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