/*
* 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:
*
* 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 com.facebook.presto.jdbc.internal.netty.handler.codec.marshalling;
import org.jboss.marshalling.Marshaller;
import com.facebook.presto.jdbc.internal.netty.buffer.ChannelBuffer;
import com.facebook.presto.jdbc.internal.netty.channel.Channel;
import com.facebook.presto.jdbc.internal.netty.channel.ChannelHandler.Sharable;
import com.facebook.presto.jdbc.internal.netty.channel.ChannelHandlerContext;
import com.facebook.presto.jdbc.internal.netty.handler.codec.oneone.OneToOneEncoder;
/**
* {@link OneToOneEncoder} implementation which uses JBoss Marshalling to marshal
* an Object. Be aware that this {@link OneToOneEncoder} is not compatible with
* an other client that just use JBoss Marshalling as it includes the size of every
* {@link Object} that gets serialized in front of the {@link Object} itself.
*
* Use this with {@link MarshallingDecoder}
*
* See <a href="http://www.jboss.org/jbossmarshalling">JBoss Marshalling website</a>
* for more informations
*
*/
@Sharable
public class MarshallingEncoder extends OneToOneEncoder {
private static final byte[] LENGTH_PLACEHOLDER = new byte[4];
private final MarshallerProvider provider;
private final int estimatedLength;
/**
* Creates a new encoder with the estimated length of 512 bytes.
*
* @param provider the {@link MarshallerProvider} to use
*/
public MarshallingEncoder(MarshallerProvider provider) {
this(provider, 512);
}
/**
* Creates a new encoder.
*
* @param provider
* the {@link MarshallerProvider} to use
* @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 MarshallingEncoder(MarshallerProvider provider, int estimatedLength) {
if (estimatedLength < 0) {
throw new IllegalArgumentException(
"estimatedLength: " + estimatedLength);
}
this.estimatedLength = estimatedLength;
this.provider = provider;
}
@Override
protected Object encode(ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
Marshaller marshaller = provider.getMarshaller(ctx);
ChannelBufferByteOutput output = new ChannelBufferByteOutput(
ctx.getChannel().getConfig().getBufferFactory(), estimatedLength);
output.getBuffer().writeBytes(LENGTH_PLACEHOLDER);
marshaller.start(output);
marshaller.writeObject(msg);
marshaller.finish();
marshaller.close();
ChannelBuffer encoded = output.getBuffer();
encoded.setInt(0, encoded.writerIndex() - 4);
return encoded;
}
}