/* * 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 net.sourceforge.opentracking.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; } }