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/*
* Copyright 2013 Anton Tananaev (anton@traccar.org)
*
* Licensed 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.traccar.protocol;
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.frame.FrameDecoder;
public class MeiligaoFrameDecoder extends FrameDecoder {
private static final int MESSAGE_HEADER = 4;
@Override
protected Object decode(
ChannelHandlerContext ctx, Channel channel, ChannelBuffer buf) throws Exception {
// Strip not '$' (0x24) bytes from the beginning
while (buf.readable() && buf.getUnsignedByte(buf.readerIndex()) != 0x24) {
buf.readByte();
}
// Check length and return buffer
if (buf.readableBytes() >= MESSAGE_HEADER) {
int length = buf.getUnsignedShort(buf.readerIndex() + 2);
if (buf.readableBytes() >= length) {
return buf.readBytes(length);
}
}
return null;
}
}
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