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/*
* Copyright 2017 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.buffer.ChannelBufferIndexFinder;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.frame.FrameDecoder;
public class TmgFrameDecoder extends FrameDecoder {
private boolean isLetter(byte c) {
return c >= 'a' && c <= 'z';
}
@Override
protected Object decode(
ChannelHandlerContext ctx, Channel channel, ChannelBuffer buf) throws Exception {
int beginIndex = buf.indexOf(buf.readerIndex(), buf.writerIndex(), new ChannelBufferIndexFinder() {
@Override
public boolean find(ChannelBuffer buffer, int guessedIndex) {
if (buffer.getByte(guessedIndex) != (byte) '$' || buffer.writerIndex() - guessedIndex < 5) {
return false;
}
return buffer.getByte(guessedIndex + 4) == ','
&& isLetter(buffer.getByte(guessedIndex + 1))
&& isLetter(buffer.getByte(guessedIndex + 2))
&& isLetter(buffer.getByte(guessedIndex + 3));
}
});
if (beginIndex >= 0) {
buf.readerIndex(beginIndex);
int endIndex = buf.indexOf(beginIndex, buf.writerIndex(), (byte) '\n');
if (endIndex >= 0) {
ChannelBuffer frame = buf.readBytes(endIndex - beginIndex);
buf.readByte(); // delimiter
return frame;
}
}
return null;
}
}
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