C# CRC16 modbus

1using System;
2using System.Collections.Generic;
3using System.Linq;
4using System.Text;
5using System.Threading.Tasks;
6
7namespace WaterBubbleCheck
8{
9    public class Crc
10    {
11            
12        /// <summary>
13        /// 判断数据中crc是否正确
14        /// </summary>
15        /// <param name="datas">传入的数据后两位是crc</param>
16        /// <returns></returns>
17        public static bool IsCrcOK(byte[] datas)
18        {
19            int length = datas.Length-2;
20
21            byte[] bytes = new byte[length];
22            Array.Copy(datas, 0, bytes, 0, length);
23            byte[] getCrc = GetModbusCrc16(bytes);
24
25            if(getCrc[0]== datas[length]&&getCrc[1]==datas[length+1])
26            {
27                return true;
28            }
29            else
30            {
31                return false;
32            }           
33        }
34        /// <summary>
35        /// 传入数据添加两位crc
36        /// </summary>
37        /// <param name="datas"></param>
38        /// <returns></returns>
39        public static byte[] GetCRCDatas(byte[] datas)
40        {
41            int length = datas.Length;
42            byte[] crc16 = GetModbusCrc16(datas);
43            byte[] crcDatas = new byte[length + 2];
44            Array.Copy(datas, crcDatas, length);
45            Array.Copy(crc16, 0, crcDatas, length,2);         
46            return crcDatas;
47        }
48         private static byte[] GetModbusCrc16(byte[] bytes)
49        {
50            byte crcRegister_H = 0xFF, crcRegister_L = 0xFF;// 预置一个值为 0xFFFF 的 16 位寄存器
51
52            byte polynomialCode_H = 0xA0, polynomialCode_L = 0x01;// 多项式码 0xA001
53
54            for (int i = 0; i < bytes.Length; i++)
55            {
56                crcRegister_L = (byte)(crcRegister_L ^ bytes[i]);
57
58                for (int j = 0; j < 8; j++)
59                {
60                    byte tempCRC_H = crcRegister_H;
61                    byte tempCRC_L = crcRegister_L;
62
63                    crcRegister_H = (byte)(crcRegister_H >> 1);
64                    crcRegister_L = (byte)(crcRegister_L >> 1);
65                    // 高位右移前最后 1 位应该是低位右移后的第 1 位：如果高位最后一位为 1 则低位右移后前面补 1
66                    if ((tempCRC_H & 0x01) == 0x01)
67                    {
68                        crcRegister_L = (byte)(crcRegister_L | 0x80);
69                    }
70
71                    if ((tempCRC_L & 0x01) == 0x01)
72                    {
73                        crcRegister_H = (byte)(crcRegister_H ^ polynomialCode_H);
74                        crcRegister_L = (byte)(crcRegister_L ^ polynomialCode_L);
75                    }
76                }
77            }
78
79            return new byte[] { crcRegister_L, crcRegister_H };
80        }
81
82    }
83}