ObjectEncoder.java

/*
 * JBoss, Home of Professional Open Source
 *
 * Copyright 2008, Red Hat Middleware LLC, and individual contributors
 * by the @author tags. See the COPYRIGHT.txt in the distribution for a
 * full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.teiid.transport;


import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufOutputStream;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelOutboundHandlerAdapter;
import io.netty.channel.ChannelPromise;
import io.netty.handler.stream.ChunkedStream;

import java.io.BufferedInputStream;
import java.io.InputStream;
import java.io.ObjectInputStream;

import org.teiid.core.util.ExternalizeUtil;
import org.teiid.netty.handler.codec.serialization.CompactObjectOutputStream;
import org.teiid.netty.handler.codec.serialization.ObjectDecoderInputStream;


/**
 * An encoder which serializes a Java object into a {@link ChannelBuffer}.
 * <p>
 * Please note that the serialized form this encoder produces is not
 * compatible with the standard {@link ObjectInputStream}.  Please use
 * {@link ObjectDecoder} or {@link ObjectDecoderInputStream} to ensure the
 * interoperability with this encoder.
 *
 * @author The Netty Project (netty-dev@lists.jboss.org)
 * @author Trustin Lee (tlee@redhat.com)
 *
 * @version $Rev:231 $, $Date:2008-06-12 16:44:50 +0900 (목, 12 6월 2008) $
 *
 * @apiviz.landmark
 * @apiviz.has org.jboss.netty.handler.codec.serialization.ObjectEncoderOutputStream - - - compatible with
 */
public class ObjectEncoder extends ChannelOutboundHandlerAdapter {
	
	public static class FailedWriteException extends Exception {
		private static final long serialVersionUID = -998903582526732966L;
		private Object object;
		
		FailedWriteException(Object object, Throwable t) {
			super(t);
			this.object = object;
		}
		
		public Object getObject() {
			return object;
		}
	}
	
    private static final byte[] LENGTH_PLACEHOLDER = new byte[4];
	private static final int CHUNK_SIZE = (1 << 16) - 1;

    private final int estimatedLength;
    private final boolean preferDirect;
    
    /**
     * Creates a new encoder with the estimated length of 512 bytes.
     */
    public ObjectEncoder() {
        this(512, true);
    }

    /**
     * Creates a new encoder.
     *
     * @param estimatedLength
     *        the estimated byte length of the serialized form of an object.
     *        If the length of the serialized form exceeds this value, the
     *        internal buffer will be expanded automatically at the cost of
     *        memory bandwidth.  If this value is too big, it will also waste
     *        memory bandwidth.  To avoid unnecessary memory copy or allocation
     *        cost, please specify the properly estimated value.
     */
    public ObjectEncoder(int estimatedLength, boolean preferDirect) {
        if (estimatedLength < 0) {
            throw new IllegalArgumentException(
                    "estimatedLength: " + estimatedLength);
        }
        this.estimatedLength = estimatedLength;
        this.preferDirect = preferDirect;
    }
    
    @Override
    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
        ByteBuf out = allocateBuffer(ctx, this.estimatedLength, this.preferDirect);
        int startIdx = out.writerIndex();
        ByteBufOutputStream bout = new ByteBufOutputStream(out);
        bout.write(LENGTH_PLACEHOLDER);
        final CompactObjectOutputStream oout = new CompactObjectOutputStream(bout);
        try {
	        oout.writeObject(msg);
	        ExternalizeUtil.writeCollection(oout, oout.getReferences());
	        oout.flush();
	        oout.close();
	        
	        int endIdx = out.writerIndex();
	        out.setInt(startIdx, endIdx - startIdx - 4);
	        
	        if (out.isReadable()) {
	            ctx.write(out, promise);
	            for (InputStream is : oout.getStreams()) {
	                ctx.write(new AnonymousChunkedStream(new BufferedInputStream(is, CHUNK_SIZE)), promise);
	            }
	        } else {
	            out.release();
	            ctx.write(Unpooled.EMPTY_BUFFER, promise);
	        }
	        ctx.flush();
	        out = null;
        } catch (Throwable t) {
        	throw new FailedWriteException(msg, t);
        } finally {
            if (out != null) {
                out.release();
            }
        }
    }
    
    protected ByteBuf allocateBuffer(ChannelHandlerContext ctx,
            int estimatedSize, boolean preferDirect)
            throws Exception {
        if (preferDirect) {
            return ctx.alloc().ioBuffer(estimatedSize);
        } else {
            return ctx.alloc().heapBuffer(estimatedSize);
        }
    }    
    
    static class AnonymousChunkedStream extends ChunkedStream {

		public AnonymousChunkedStream(InputStream in) {
			super(in, CHUNK_SIZE);
		}
    	
		@Override
		public ByteBuf readChunk(ChannelHandlerContext ctx) throws Exception {
		    ByteBuf cb = (ByteBuf)super.readChunk(ctx);
			int length = cb.capacity();
			ByteBuf prefix = Unpooled.wrappedBuffer(new byte[2]);
			prefix.setShort(0, (short)length);
			if (isEndOfInput()) {
				//append a 0 short
				return Unpooled.wrappedBuffer(prefix, cb, Unpooled.wrappedBuffer(new byte[2]));
			}
			return Unpooled.wrappedBuffer(prefix, cb);
		}
		
    }

}