/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF 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 org.apache.hadoop.oncrpc;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.frame.FrameDecoder;
/**
* {@link FrameDecoder} for RPC messages.
*/
public class RpcFrameDecoder extends FrameDecoder {
public static final Log LOG = LogFactory.getLog(RpcFrameDecoder.class);
private ChannelBuffer frame;
/**
* Decode an RPC message received on the socket.
* @return mpnull if incomplete message is received.
*/
@Override
protected Object decode(ChannelHandlerContext ctx, Channel channel,
ChannelBuffer buf) {
// Make sure if the length field was received.
if (buf.readableBytes() < 4) {
if (LOG.isTraceEnabled()) {
LOG.trace("Length field is not received yet");
}
return null;
}
// Note the index and go back to it when an incomplete message is received
buf.markReaderIndex();
// Read the record marking.
ChannelBuffer fragmentHeader = buf.readBytes(4);
int length = XDR.fragmentSize(fragmentHeader.array());
boolean isLast = XDR.isLastFragment(fragmentHeader.array());
// Make sure if there's enough bytes in the buffer.
if (buf.readableBytes() < length) {
if (LOG.isTraceEnabled()) {
LOG.trace(length + " bytes are not received yet");
}
buf.resetReaderIndex(); // Go back to the right reader index
return null;
}
if (frame == null) {
frame = buf.readBytes(length);
} else {
ChannelBuffer tmp = ChannelBuffers.copiedBuffer(frame.array(), buf
.readBytes(length).array());
frame = tmp;
}
// Successfully decoded a frame. Return the decoded frame if the frame is
// the last one. Otherwise, wait for the next frame.
if (isLast) {
ChannelBuffer completeFrame = frame;
frame = null;
return completeFrame;
} else {
LOG.info("Wait for the next frame. This rarely happens.");
return null;
}
}
}