update 电单车协议

jsowell-netty/src/main/java/com/jsowell/netty/decoder/ChargingPileDecoder.java

@@ -0,0 +1,77 @@
+package com.jsowell.netty.decoder;
+
+import com.jsowell.netty.domain.ChargingPileMessage;
+import io.netty.buffer.ByteBuf;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.handler.codec.ByteToMessageDecoder;
+
+import java.util.List;
+
+public class ChargingPileDecoder extends ByteToMessageDecoder {
+
+    private static final byte[] FRAME_HEADER = {'D', 'N', 'Y'}; // 包头为"DNY"
+    private static final int MIN_FRAME_LENGTH = 14; // 最小帧长度:包头(3)+长度(2)+物理ID(4)+消息ID(2)+命令(1)+校验(2)
+
+    @Override
+    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
+        while (in.readableBytes() >= MIN_FRAME_LENGTH) {
+            in.markReaderIndex();
+
+            // 检查包头
+            byte[] header = new byte[3];
+            in.readBytes(header);
+            if (!isValidHeader(header)) {
+                in.resetReaderIndex();
+                return;
+            }
+
+            // 读取长度
+            short length = in.readShort();
+            if (in.readableBytes() < length - 5) { // 5 = 包头(3) + 长度(2)
+                in.resetReaderIndex();
+                return;
+            }
+
+            // 读取物理ID
+            int physicalId = in.readInt();
+
+            // 读取消息ID
+            short messageId = in.readShort();
+
+            // 读取命令
+            byte command = in.readByte();
+
+            // 读取数据
+            int dataLength = length - 13; // 13 = 包头(3) + 长度(2) + 物理ID(4) + 消息ID(2) + 命令(1) + 校验(2)
+            byte[] data = new byte[dataLength];
+            in.readBytes(data);
+
+            // 读取校验和
+            short checksum = in.readShort();
+
+            // 验证校验和
+            short calculatedChecksum = calculateChecksum(in, length);
+            if (checksum != calculatedChecksum) {
+                System.out.println("校验和错误，丢弃此帧");
+                continue;
+            }
+
+            // 创建消息对象并添加到输出列表
+            ChargingPileMessage message = new ChargingPileMessage(physicalId, messageId, command, data);
+            out.add(message);
+        }
+    }
+
+    private boolean isValidHeader(byte[] header) {
+        return header[0] == FRAME_HEADER[0] && header[1] == FRAME_HEADER[1] && header[2] == FRAME_HEADER[2];
+    }
+
+    private short calculateChecksum(ByteBuf buf, int length) {
+        short sum = 0;
+        for (int i = 0; i < length - 2; i++) {
+            sum += buf.getByte(buf.readerIndex() - length + i) & 0xFF;
+        }
+        return sum;
+    }
+}
+