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/*
* Copyright 2010 Anton Tananaev (anton@tananaev.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.xexun;
import org.jboss.netty.handler.codec.frame.FrameDecoder;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.buffer.ChannelBuffer;
public class XexunFrameDecoder extends FrameDecoder {
/**
* Find string in network buffer
*/
private static Integer find(
ChannelBuffer buf,
Integer start,
Integer length,
String subString) {
int index = start;
boolean match;
for (; index < length; index++) {
match = true;
for (int i = 0; i < subString.length(); i++) {
char c = (char) buf.getByte(index + i);
if (c != subString.charAt(i)) {
match = false;
break;
}
}
if (match) {
return index;
}
}
return null;
}
protected Object decode(
ChannelHandlerContext ctx,
Channel channel,
ChannelBuffer buf) throws Exception {
// Check minimum length
int length = buf.readableBytes();
if (length < 100) {
return null;
}
// Find start
Integer beginIndex = find(buf, 0, length, "GPRMC");
if (beginIndex == null) {
return null;
}
// Find identifier
Integer idIndex = find(buf, beginIndex, length, "imei:");
if (idIndex == null) {
return null;
}
// Find end
Integer endIndex = find(buf, idIndex, length, ",");
if (endIndex == null) {
return null;
}
// Read buffer
buf.skipBytes(beginIndex);
ChannelBuffer frame = buf.readBytes(endIndex - beginIndex + 1);
return frame;
}
}
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