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/*
* Copyright 2017 - 2020 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.traccar.BaseFrameDecoder;
import io.netty.buffer.ByteBuf;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
public class TmgFrameDecoder extends BaseFrameDecoder {
private boolean isLetter(byte c) {
return c >= 'a' && c <= 'z';
}
private int findHeader(ByteBuf buffer) {
int guessedIndex = buffer.indexOf(buffer.readerIndex(), buffer.writerIndex(), (byte) '$');
while (guessedIndex != -1 && buffer.writerIndex() - guessedIndex >= 5) {
if (buffer.getByte(guessedIndex + 4) == ','
&& isLetter(buffer.getByte(guessedIndex + 1))
&& isLetter(buffer.getByte(guessedIndex + 2))
&& isLetter(buffer.getByte(guessedIndex + 3))) {
return guessedIndex;
}
guessedIndex = buffer.indexOf(guessedIndex + 1, buffer.writerIndex(), (byte) '$');
}
return -1;
}
@Override
protected Object decode(
ChannelHandlerContext ctx, Channel channel, ByteBuf buf) throws Exception {
int beginIndex = findHeader(buf);
if (beginIndex >= 0) {
buf.readerIndex(beginIndex);
int endIndex = buf.indexOf(beginIndex, buf.writerIndex(), (byte) '\n');
if (endIndex >= 0) {
ByteBuf frame = buf.readRetainedSlice(endIndex - beginIndex);
buf.readByte(); // delimiter
return frame;
}
}
return null;
}
}
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