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/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) 2007-2010 Oracle and/or its affiliates. All rights reserved.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
 * obtain a copy of the License at
 * https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
 * or packager/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 *
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at packager/legal/LICENSE.txt.
 *
 * GPL Classpath Exception:
 * Oracle designates this particular file as subject to the "Classpath"
 * exception as provided by Oracle in the GPL Version 2 section of the License
 * file that accompanied this code.
 *
 * Modifications:
 * If applicable, add the following below the License Header, with the fields
 * enclosed by brackets [] replaced by your own identifying information:
 * "Portions Copyright [year] [name of copyright owner]"
 *
 * Contributor(s):
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 */

package com.sun.grizzly.comet;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.SocketChannel;

/**
 * Non blocking IO reader. This class can be used from a 
 * {@link CometHandler} to execute non blocking read. This is
 * usefull when the client is pipelining data. The CometHandler
 * will be notified as soon as bytes are arriving. CometHandler
 * who wants to be notified just need to register themself
 * by calling CometContext.registerAsyncRead()
 *
 * @author Jeanfrancois Arcand
 */
public class CometReader {

    private static final IllegalStateException ISEnotusable = 
            new IllegalStateException("This CometReader is no longer usable");

    /**
     * The non blocking channel.
     */
    private SocketChannel socketChannel;
    
    
    /**
     * The ByteBuffer used to execute the first read in CometTask.
     */
    private ByteBuffer byteBuffer;
    
    
    /**
     * How many bytes have we read.
     */
    private int nRead = 0;
    
    
    /**
     * Is this CometReader ready
     */
    private boolean ready = true;
            
    
    public CometReader() {
    }


    /**
     * Set the underlying SocketChannel.
     */
    protected void setChannel(SocketChannel socketChannel){      
        this.socketChannel = socketChannel;
    }    
    
    
    /**
     *  Read bytes without blocking.
     */ 
    public int read(byte[] buf) throws IOException {
        return read(buf,0,buf.length);
    }

    
    /**
     * Read bytes without blocking.
     */
    public int read(byte[] buf, int off, int len) throws IOException {
        if (!ready){
            throw ISEnotusable;
        }
        // The CometTask has already read the first bytes for us.
        if (byteBuffer != null){           
            byteBuffer.get(buf,off,len);
            return nRead > len ? len : nRead;
        }
        return socketChannel.read(ByteBuffer.wrap(buf,off,len));
    }
   
    
    /**
     * Recycle this object.
     */
    public void recycle(){
        nRead = 0;
        byteBuffer = null;
        socketChannel = null;
    }    


    void setByteBuffer(ByteBuffer byteBuffer) {
        this.byteBuffer = byteBuffer;
    }

    
    void setNRead(int nRead) {
        this.nRead = nRead;
    }

    
    /**
     * Return true if this instance is ready to read.
     */
    public boolean isReady() {
        return ready;
    }

    
    /**
     * false if this instance is no longer ready to read.
     */
    void setReady(boolean ready) {
        this.ready = ready;
    }
}