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/*
* Copyright 2016 Anton Tananaev (anton.tananaev@gmail.com)
*
* 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 java.nio.charset.StandardCharsets;
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;
import org.traccar.helper.StringFinder;
public class GranitFrameDecoder extends FrameDecoder {
private static final int HEADER_LENGTH = 6;
private static final int CHECKSUM_LENGTH = 3;
private static final int SHORT_LENGTH = 2;
@Override
protected Object decode(
ChannelHandlerContext ctx, Channel channel, ChannelBuffer buf) throws Exception {
if (buf.readableBytes() > HEADER_LENGTH + SHORT_LENGTH) {
ChannelBuffer frame = ChannelBuffers.dynamicBuffer();
buf.getBytes(buf.readerIndex(), frame, HEADER_LENGTH);
String headerString = frame.toString(StandardCharsets.US_ASCII);
if (headerString.equals("+RRCB~") || headerString.equals("+DDAT~")) {
int length = buf.getUnsignedShort(buf.readerIndex() + HEADER_LENGTH);
if (buf.readableBytes() >= HEADER_LENGTH + SHORT_LENGTH + length + CHECKSUM_LENGTH) {
frame = buf.readBytes(HEADER_LENGTH + SHORT_LENGTH + length + CHECKSUM_LENGTH);
if (buf.readableBytes() > 2) {
buf.skipBytes(2); //skip \r\n
}
return frame;
} else {
return null; //damaged packet
}
}
}
int index = buf.indexOf(buf.readerIndex(), buf.writerIndex(), new StringFinder("\r\n"));
if (index != -1) {
ChannelBuffer frame = buf.readBytes(index - buf.readerIndex());
buf.skipBytes(2);
return frame;
}
return null;
}
}
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