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/*
* Copyright 2013 - 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 NavigilFrameDecoder extends BaseFrameDecoder {
private static final int MESSAGE_HEADER = 20;
private static final long PREAMBLE = 0x2477F5F6;
@Override
protected Object decode(
ChannelHandlerContext ctx, Channel channel, ByteBuf buf) throws Exception {
// Check minimum length
if (buf.readableBytes() < MESSAGE_HEADER) {
return null;
}
// Check for preamble
boolean hasPreamble = false;
if (buf.getUnsignedIntLE(buf.readerIndex()) == PREAMBLE) {
hasPreamble = true;
}
// Check length and return buffer
int length = buf.getUnsignedShortLE(buf.readerIndex() + 6);
if (buf.readableBytes() >= length) {
if (hasPreamble) {
buf.readUnsignedIntLE();
length -= 4;
}
return buf.readRetainedSlice(length);
}
return null;
}
}
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