/* * Copyright 2015 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; public class BceFrameDecoder extends FrameDecoder { private static final int HANDSHAKE_LENGTH = 7; // "#BCE#\r\n" private boolean header = true; private static byte checksum(ChannelBuffer buf, int end) { byte result = 0; for (int i = 0; i < end; i++) { result += buf.getByte(buf.readerIndex() + i); } return result; } @Override protected Object decode( ChannelHandlerContext ctx, Channel channel, ChannelBuffer buf) throws Exception { if (header && buf.readableBytes() >= HANDSHAKE_LENGTH) { buf.skipBytes(HANDSHAKE_LENGTH); header = false; } int end = 8; // IMEI while (buf.readableBytes() >= end + 2 + 1 + 1 + 1) { end += buf.getUnsignedShort(buf.readerIndex() + end) + 2; if (buf.readableBytes() > end && checksum(buf, end) == buf.getByte(buf.readerIndex() + end)) { return buf.readBytes(end + 1); } } return null; } }