Java tutorial
/* * Copyright 2017 - 2018 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 java.nio.charset.StandardCharsets; public class T57FrameDecoder extends BaseFrameDecoder { @Override protected Object decode(ChannelHandlerContext ctx, Channel channel, ByteBuf buf) throws Exception { if (buf.readableBytes() < 10) { return null; } String type = buf.toString(buf.readerIndex() + 5, 2, StandardCharsets.US_ASCII); int count = type.equals("F3") ? 12 : 14; int index = 0; while (index >= 0 && count > 0) { index = buf.indexOf(index + 1, buf.writerIndex(), (byte) '#'); if (index > 0) { count -= 1; } } return index > 0 ? buf.readRetainedSlice(index + 1 - buf.readerIndex()) : null; } }