package cn.org.hentai.jtt1078.server.backup;
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import cn.org.hentai.jtt1078.entity.Jt1078Message;
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import io.netty.buffer.ByteBuf;
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import io.netty.channel.ChannelHandlerContext;
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import io.netty.handler.codec.ByteToMessageDecoder;
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import lombok.extern.slf4j.Slf4j;
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import java.util.List;
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@Slf4j
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public class Jt1078MessageDecoder extends ByteToMessageDecoder {
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private static final int HEADER_MIN_LEN = 34;
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private static final int MAX_SKIP_BYTES = 4096; // 防错机制
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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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int skippedBytes = 0;
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while (true) {
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if (in.readableBytes() < 4) return;
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in.markReaderIndex();
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int header = in.readInt();
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if ((header & 0x7FFFFFFF) != 0x30316364) {
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in.resetReaderIndex();
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in.readByte(); // 滑动窗口继续查找包头
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skippedBytes++;
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if (skippedBytes >= MAX_SKIP_BYTES) {
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log.error("Too many invalid bytes ({}), close connection", skippedBytes);
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ctx.close();
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return;
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}
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continue;
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}
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// mark 包头对齐位置
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in.markReaderIndex();
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// 保证至少读完基本字段
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if (in.readableBytes() < 1 + 1 + 2) {
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in.resetReaderIndex();
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return;
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}
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byte vpxcc = in.readByte();
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byte mpt = in.readByte();
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short seq = in.readShort();
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// 先判断协议版本
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boolean isV2019 = detectProtocolVersion(in);
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int simLength = isV2019 ? 10 : 6;
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// 判断总剩余数据是否足够（SIM 卡 + 通道 + 数据类型 + 时间戳 + iframe/frame interval + 长度字段）
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if (in.readableBytes() < simLength + 1 + 1 + 8 + 2 + 2 + 2) {
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in.resetReaderIndex();
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return;
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}
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byte[] simBytes = new byte[simLength];
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in.readBytes(simBytes);
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String sim = bcdToString(simBytes);
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byte channel = in.readByte();
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byte dataTypeByte = in.readByte();
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byte[] timestampBytes = new byte[8];
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in.readBytes(timestampBytes);
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short lastIframeInterval = in.readShort();
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short lastFrameInterval = in.readShort();
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short dataLength = in.readShort();
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if (dataLength < 0) {
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log.warn("Invalid dataLength: {}", dataLength);
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in.resetReaderIndex();
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in.readByte(); // 跳1字节再重新查找包头
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skippedBytes++;
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continue;
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}
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if (in.readableBytes() < dataLength) {
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in.resetReaderIndex();
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return; // 等待更多数据
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}
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byte[] data = new byte[dataLength];
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in.readBytes(data);
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Jt1078Message message = new Jt1078Message();
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message.setHeader(header);
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message.setVpxcc(vpxcc);
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message.setMpt(mpt);
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message.setSequence(seq);
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message.setSim(sim);
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message.setChannel(channel);
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message.setDataTypeAndSpm(dataTypeByte);
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message.setTimestamp(timestampBytes);
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message.setLastIframeInterval(lastIframeInterval);
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message.setLastFrameInterval(lastFrameInterval);
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message.setLength(dataLength);
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message.parseExtendedFields();
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out.add(message);
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log.warn("Parsed packet: {}", message.toString());
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}
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}
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private boolean detectProtocolVersion(ByteBuf in) {
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// 保存原始读取位置
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in.markReaderIndex();
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try {
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// 2016协议SIM卡号位置：包头4 + VPXCC1 + MPT1 + SEQ2 = 8字节
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// 所以SIM卡号在8-13字节（6字节）
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// 2019协议SIM卡号在8-17字节（10字节）
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// 跳到SIM卡号起始位置
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in.skipBytes(8);
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// 检查第14-17字节（2016协议这部分是通道号/数据类型，2019协议是SIM卡继续）
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byte[] probeBytes = new byte[4];
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in.readBytes(probeBytes);
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// BCD码有效性检查：每半个字节应在0-9之间
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for (byte b : probeBytes) {
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if (((b & 0xF0) >>> 4) > 9 || ((b & 0x0F) > 9)) {
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return true; // 发现非BCD码，可能是2019协议
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}
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}
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return false;
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} finally {
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// 无论检测成功与否，都重置读取位置
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in.resetReaderIndex();
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}
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}
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private String bcdToString(byte[] bcd) {
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StringBuilder sb = new StringBuilder();
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for (byte b : bcd) {
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sb.append(String.format("%02x", b));
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}
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return sb.toString();
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}
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}
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