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/*
* Copyright 2019 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;
import org.traccar.helper.BufferUtil;
public class ItsFrameDecoder extends BaseFrameDecoder {
private static final int MINIMUM_LENGTH = 20;
private ByteBuf readFrame(ByteBuf buf, int delimiterIndex, int skip) {
int headerIndex = buf.indexOf(buf.readerIndex() + 1, buf.writerIndex(), (byte) '$');
if (headerIndex > 0 && headerIndex < delimiterIndex) {
return buf.readRetainedSlice(headerIndex - buf.readerIndex());
} else {
ByteBuf frame = buf.readRetainedSlice(delimiterIndex - buf.readerIndex());
buf.skipBytes(skip);
return frame;
}
}
@Override
protected Object decode(
ChannelHandlerContext ctx, Channel channel, ByteBuf buf) throws Exception {
while (buf.isReadable() && buf.getByte(buf.readerIndex()) != '$') {
buf.skipBytes(1);
}
int delimiterIndex = BufferUtil.indexOf("\r\n", buf);
if (delimiterIndex > MINIMUM_LENGTH) {
return readFrame(buf, delimiterIndex, 2);
} else {
delimiterIndex = buf.indexOf(buf.readerIndex(), buf.writerIndex(), (byte) '*');
if (delimiterIndex > MINIMUM_LENGTH) {
if (buf.writerIndex() > delimiterIndex + 1 && buf.getByte(delimiterIndex + 1) == '*') {
delimiterIndex += 1;
}
if (buf.getByte(delimiterIndex - 2) == ',') {
return readFrame(buf, delimiterIndex - 1, 2); // skip binary checksum
} else {
return readFrame(buf, delimiterIndex, 1);
}
}
}
return null;
}
}
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