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/*
* Copyright 2015 - 2018 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 io.netty.buffer.ByteBuf;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import org.traccar.BaseFrameDecoder;
public class BceFrameDecoder extends BaseFrameDecoder {
private static final int HANDSHAKE_LENGTH = 7; // "#BCE#\r\n"
private boolean header = true;
private static byte checksum(ByteBuf buf, int end) {
byte result = 0;
for (int i = 0; i < end; i++) {
result += buf.getByte(buf.readerIndex() + i);
}
return result;
}
@Override
protected Object decode(
ChannelHandlerContext ctx, Channel channel, ByteBuf buf) throws Exception {
if (header && buf.readableBytes() >= HANDSHAKE_LENGTH) {
buf.skipBytes(HANDSHAKE_LENGTH);
header = false;
}
int end = 8; // IMEI
while (buf.readableBytes() >= end + 2 + 1 + 1 + 1) {
end += buf.getUnsignedShortLE(buf.readerIndex() + end) + 2;
if (buf.readableBytes() > end && checksum(buf, end) == buf.getByte(buf.readerIndex() + end)) {
return buf.readRetainedSlice(end + 1);
}
}
return null;
}
}
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