package com.genersoft.iot.vmp.jt1078.codec.decode;
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import com.genersoft.iot.vmp.jt1078.proc.Header;
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import com.genersoft.iot.vmp.jt1078.proc.factory.CodecFactory;
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import com.genersoft.iot.vmp.jt1078.proc.request.Re;
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import com.genersoft.iot.vmp.jt1078.proc.response.Rs;
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import com.genersoft.iot.vmp.jt1078.session.Session;
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import io.netty.buffer.ByteBuf;
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import io.netty.buffer.ByteBufUtil;
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import io.netty.buffer.CompositeByteBuf;
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import io.netty.buffer.UnpooledByteBufAllocator;
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import io.netty.channel.ChannelHandlerContext;
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import io.netty.handler.codec.ByteToMessageDecoder;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* @author QingtaiJiang
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* @date 2023/4/27 18:10
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* @email qingtaij@163.com
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*/
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public class Jt808Decoder extends ByteToMessageDecoder {
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private final static Logger log = LoggerFactory.getLogger(Jt808Decoder.class);
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@Override
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protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
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Session session = ctx.channel().attr(Session.KEY).get();
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log.info("> {} hex:{}", session, ByteBufUtil.hexDump(in));
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try {
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ByteBuf buf = unEscapeAndCheck(in);
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Header header = new Header();
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header.setMsgId(ByteBufUtil.hexDump(buf.readSlice(2)));
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header.setMsgPro(buf.readUnsignedShort());
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if (header.is2019Version()) {
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header.setVersion(buf.readUnsignedByte());
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String devId = ByteBufUtil.hexDump(buf.readSlice(10));
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header.setDevId(devId.replaceFirst("^0*", ""));
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} else {
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header.setDevId(ByteBufUtil.hexDump(buf.readSlice(6)).replaceFirst("^0*", ""));
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}
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header.setSn(buf.readUnsignedShort());
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Re handler = CodecFactory.getHandler(header.getMsgId());
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if (handler == null) {
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log.error("get msgId is null {}", header.getMsgId());
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return;
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}
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Rs decode = handler.decode(buf, header, session);
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if (decode != null) {
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out.add(decode);
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}
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} finally {
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in.skipBytes(in.readableBytes());
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}
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}
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/**
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* 转义与验证校验码
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*
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* @param byteBuf 转义Buf
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* @return 转义好的数据
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*/
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public ByteBuf unEscapeAndCheck(ByteBuf byteBuf) throws Exception {
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int low = byteBuf.readerIndex();
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int high = byteBuf.writerIndex();
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byte checkSum = 0;
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int calculationCheckSum = 0;
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byte aByte = byteBuf.getByte(high - 2);
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byte protocolEscapeFlag7d = 0x7d;
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//0x7d转义
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byte protocolEscapeFlag01 = 0x01;
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//0x7e转义
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byte protocolEscapeFlag02 = 0x02;
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if (aByte == protocolEscapeFlag7d) {
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byte b2 = byteBuf.getByte(high - 1);
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if (b2 == protocolEscapeFlag01) {
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checkSum = protocolEscapeFlag7d;
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} else if (b2 == protocolEscapeFlag02) {
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checkSum = 0x7e;
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} else {
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log.error("转义1异常:{}", ByteBufUtil.hexDump(byteBuf));
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throw new Exception("转义错误");
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}
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high = high - 2;
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} else {
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high = high - 1;
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checkSum = byteBuf.getByte(high);
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}
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List<ByteBuf> bufList = new ArrayList<>();
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int index = low;
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while (index < high) {
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byte b = byteBuf.getByte(index);
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if (b == protocolEscapeFlag7d) {
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byte c = byteBuf.getByte(index + 1);
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if (c == protocolEscapeFlag01) {
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ByteBuf slice = slice0x01(byteBuf, low, index);
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bufList.add(slice);
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b = protocolEscapeFlag7d;
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} else if (c == protocolEscapeFlag02) {
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ByteBuf slice = slice0x02(byteBuf, low, index);
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bufList.add(slice);
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b = 0x7e;
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} else {
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log.error("转义2异常:{}", ByteBufUtil.hexDump(byteBuf));
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throw new Exception("转义错误");
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}
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index += 2;
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low = index;
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} else {
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index += 1;
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}
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calculationCheckSum = calculationCheckSum ^ b;
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}
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if (calculationCheckSum == checkSum) {
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if (bufList.size() == 0) {
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return byteBuf.slice(low, high);
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} else {
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bufList.add(byteBuf.slice(low, high - low));
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return new CompositeByteBuf(UnpooledByteBufAllocator.DEFAULT, false, bufList.size(), bufList);
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}
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} else {
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log.info("{} 解析校验码:{}--计算校验码:{}", ByteBufUtil.hexDump(byteBuf), checkSum, calculationCheckSum);
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throw new Exception("校验码错误!");
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}
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}
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private ByteBuf slice0x01(ByteBuf buf, int low, int sign) {
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return buf.slice(low, sign - low + 1);
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}
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private ByteBuf slice0x02(ByteBuf buf, int low, int sign) {
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buf.setByte(sign, 0x7e);
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return buf.slice(low, sign - low + 1);
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}
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}
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