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/*
* Copyright 2017 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.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.frame.FrameDecoder;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
public class Gl200FrameDecoder extends FrameDecoder {
private static final int MINIMUM_LENGTH = 11;
private static final Set<String> BINARY_HEADERS = new HashSet<>(
Arrays.asList("+RSP", "+BSP", "+EVT", "+BVT", "+INF", "+BNF", "+HBD", "+CRD", "+BRD"));
public static boolean isBinary(ChannelBuffer buf) {
String header = buf.toString(buf.readerIndex(), 4, StandardCharsets.US_ASCII);
if (header.equals("+ACK")) {
return buf.getByte(buf.readerIndex() + header.length()) != (byte) ':';
} else {
return BINARY_HEADERS.contains(header);
}
}
@Override
protected Object decode(
ChannelHandlerContext ctx, Channel channel, ChannelBuffer buf) throws Exception {
if (buf.readableBytes() < MINIMUM_LENGTH) {
return null;
}
if (isBinary(buf)) {
int length;
switch (buf.toString(buf.readerIndex(), 4, StandardCharsets.US_ASCII)) {
case "+ACK":
length = buf.getUnsignedByte(buf.readerIndex() + 6);
break;
case "+INF":
case "+BNF":
length = buf.getUnsignedShort(buf.readerIndex() + 7);
break;
case "+HBD":
length = buf.getUnsignedByte(buf.readerIndex() + 5);
break;
case "+CRD":
case "+BRD":
length = buf.getUnsignedShort(buf.readerIndex() + 6);
break;
default:
length = buf.getUnsignedShort(buf.readerIndex() + 9);
break;
}
if (buf.readableBytes() >= length) {
return buf.readBytes(length);
}
} else {
int endIndex = buf.indexOf(buf.readerIndex(), buf.writerIndex(), (byte) '$');
if (endIndex < 0) {
endIndex = buf.indexOf(buf.readerIndex(), buf.writerIndex(), (byte) 0);
}
if (endIndex > 0) {
ChannelBuffer frame = buf.readBytes(endIndex - buf.readerIndex());
buf.readByte(); // delimiter
return frame;
}
}
return null;
}
}
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