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| 1 | +//--------------------------------------------------------------------------- |
| 2 | +// |
| 3 | +// Name: Crc16.cs |
| 4 | +// Author: Vita Tucek |
| 5 | +// Created: 23.5.2024 |
| 6 | +// License: MIT |
| 7 | +// Description: CRC16 (Modbus) calculation |
| 8 | +// |
| 9 | +//--------------------------------------------------------------------------- |
| 10 | + |
| 11 | +namespace SerialMonitor.Functions |
| 12 | +{ |
| 13 | + public class Crc16 : FunctionBase |
| 14 | + { |
| 15 | + private static readonly ushort[] crc_table = { |
| 16 | + 0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241, |
| 17 | + 0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440, |
| 18 | + 0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40, |
| 19 | + 0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841, |
| 20 | + 0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40, |
| 21 | + 0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41, |
| 22 | + 0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641, |
| 23 | + 0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040, |
| 24 | + 0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240, |
| 25 | + 0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441, |
| 26 | + 0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41, |
| 27 | + 0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840, |
| 28 | + 0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41, |
| 29 | + 0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40, |
| 30 | + 0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640, |
| 31 | + 0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041, |
| 32 | + 0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240, |
| 33 | + 0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441, |
| 34 | + 0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41, |
| 35 | + 0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840, |
| 36 | + 0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41, |
| 37 | + 0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40, |
| 38 | + 0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640, |
| 39 | + 0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041, |
| 40 | + 0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241, |
| 41 | + 0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440, |
| 42 | + 0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40, |
| 43 | + 0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841, |
| 44 | + 0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40, |
| 45 | + 0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41, |
| 46 | + 0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641, |
| 47 | + 0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040 |
| 48 | + }; |
| 49 | + |
| 50 | + public Crc16(int position) : base(position) |
| 51 | + { |
| 52 | + } |
| 53 | + |
| 54 | + public Crc16(int position, int start, int end) : base(position, start, end) |
| 55 | + { |
| 56 | + } |
| 57 | + |
| 58 | + public override int Size => 2; |
| 59 | + |
| 60 | + /// <summary> |
| 61 | + /// Compute over specified length |
| 62 | + /// </summary> |
| 63 | + /// <param name="data"></param> |
| 64 | + /// <param name="length"></param> |
| 65 | + /// <returns></returns> |
| 66 | + public static ushort ComputeCrc(byte[] data, int position, int start, int end) |
| 67 | + { |
| 68 | + int dataend = end < position ? end : position - 1; |
| 69 | + ushort temp; |
| 70 | + ushort crc = 0xFFFF; |
| 71 | + |
| 72 | + for (int i = start; i <= dataend; i++) |
| 73 | + { |
| 74 | + temp = (ushort)((data[i] ^ crc) & 0x00FF); |
| 75 | + crc >>= 8; |
| 76 | + crc ^= crc_table[temp]; |
| 77 | + } |
| 78 | + |
| 79 | + return crc; |
| 80 | + } |
| 81 | + |
| 82 | + public override void Compute(byte[] data) |
| 83 | + { |
| 84 | + var crc = Crc16.ComputeCrc(data, Position, Start, End); |
| 85 | + data[Position] = (byte)(crc & 0xFF); |
| 86 | + data[Position + 1] = (byte)(crc >> 8 & 0xFF); |
| 87 | + } |
| 88 | + |
| 89 | + /// <summary> |
| 90 | + /// Verify data with CRC included |
| 91 | + /// </summary> |
| 92 | + /// <param name="data"></param> |
| 93 | + /// <param name="length"></param> |
| 94 | + /// <returns></returns> |
| 95 | + public static bool Verify(byte[] data) |
| 96 | + { |
| 97 | + return Verify(data, data.Length); |
| 98 | + } |
| 99 | + |
| 100 | + /// <summary> |
| 101 | + /// Verify data with CRC included |
| 102 | + /// </summary> |
| 103 | + /// <param name="data"></param> |
| 104 | + /// <param name="length"></param> |
| 105 | + /// <returns></returns> |
| 106 | + public static bool Verify(byte[] data, int length) |
| 107 | + { |
| 108 | + if (length < 3) |
| 109 | + return false; |
| 110 | + ushort computed = ComputeCrc(data, length - 2, 0, length - 2); |
| 111 | + ushort received = (ushort)((ushort)(data[length - 1] << 8) + data[length - 2]); |
| 112 | + |
| 113 | + return computed == received; |
| 114 | + } |
| 115 | + } |
| 116 | +} |
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