如何使用基于表格的CRC-16代码

Question

我希望有人能够阐明为什么我的CRC-16实现似乎不能在Visual Studio上正确运行?我从特定设备的手册中获得了算法，并自己编写了int main()。当我试图将参数传递给函数时，总是会出现"类型"错误，所以我怀疑格式有问题?这是代码附带的信息:

• CRC名称:CRC-16
• 宽度:16位
使用的多项式:1189(十六进制)
• 种子值:FFFF (hex)
• 反射输入/输出:No
• 独占或输出:No

• 测试字符串"123456789":5502(十六进制)

  #include <stdio.h>
  unsigned int crctable[256] =
  {
  0x0000, 0x1189, 0x2312, 0x329B, 0x4624, 0x57AD, 0x6536, 0x74BF,
  0x8C48, 0x9DC1, 0xAF5A, 0xBED3, 0xCA6C, 0xDBE5, 0xE97E, 0xF8F7,
  0x0919, 0x1890, 0x2A0B, 0x3B82, 0x4F3D, 0x5EB4, 0x6C2F, 0x7DA6,
  0x8551, 0x94D8, 0xA643, 0xB7CA, 0xC375, 0xD2FC, 0xE067, 0xF1EE,
  0x1232, 0x03BB, 0x3120, 0x20A9, 0x5416, 0x459F, 0x7704, 0x668D,
  0x9E7A, 0x8FF3, 0xBD68, 0xACE1, 0xD85E, 0xC9D7, 0xFB4C, 0xEAC5,
  0x1B2B, 0x0AA2, 0x3839, 0x29B0, 0x5D0F, 0x4C86, 0x7E1D, 0x6F94,
  0x9763, 0x86EA, 0xB471, 0xA5F8, 0xD147, 0xC0CE, 0xF255, 0xE3DC,
  0x2464, 0x35ED, 0x0776, 0x16FF, 0x6240, 0x73C9, 0x4152, 0x50DB,
  0xA82C, 0xB9A5, 0x8B3E, 0x9AB7, 0xEE08, 0xFF81, 0xCD1A, 0xDC93,
  0x2D7D, 0x3CF4, 0x0E6F, 0x1FE6, 0x6B59, 0x7AD0, 0x484B, 0x59C2,
  0xA135, 0xB0BC, 0x8227, 0x93AE, 0xE711, 0xF698, 0xC403, 0xD58A,
  0x3656, 0x27DF, 0x1544, 0x04CD, 0x7072, 0x61FB, 0x5360, 0x42E9,
  0xBA1E, 0xAB97, 0x990C, 0x8885, 0xFC3A, 0xEDB3, 0xDF28, 0xCEA1,
  0x3F4F, 0x2EC6, 0x1C5D, 0x0DD4, 0x796B, 0x68E2, 0x5A79, 0x4BF0,
  0xB307, 0xA28E, 0x9015, 0x819C, 0xF523, 0xE4AA, 0xD631, 0xC7B8,
  0x48C8, 0x5941, 0x6BDA, 0x7A53, 0x0EEC, 0x1F65, 0x2DFE, 0x3C77,
  0xC480, 0xD509, 0xE792, 0xF61B, 0x82A4, 0x932D, 0xA1B6, 0xB03F,
  0x41D1, 0x5058, 0x62C3, 0x734A, 0x07F5, 0x167C, 0x24E7, 0x356E,
  0xCD99, 0xDC10, 0xEE8B, 0xFF02, 0x8BBD, 0x9A34, 0xA8AF, 0xB926,
  0x5AFA, 0x4B73, 0x79E8, 0x6861, 0x1CDE, 0x0D57, 0x3FCC, 0x2E45,
  0xD6B2, 0xC73B, 0xF5A0, 0xE429, 0x9096, 0x811F, 0xB384, 0xA20D,
  0x53E3, 0x426A, 0x70F1, 0x6178, 0x15C7, 0x044E, 0x36D5, 0x275C,
  0xDFAB, 0xCE22, 0xFCB9, 0xED30, 0x998F, 0x8806, 0xBA9D, 0xAB14,
  0x6CAC, 0x7D25, 0x4FBE, 0x5E37, 0x2A88, 0x3B01, 0x099A, 0x1813,
  0xE0E4, 0xF16D, 0xC3F6, 0xD27F, 0xA6C0, 0xB749, 0x85D2, 0x945B,
  0x65B5, 0x743C, 0x46A7, 0x572E, 0x2391, 0x3218, 0x0083, 0x110A,
  0xE9FD, 0xF874, 0xCAEF, 0xDB66, 0xAFD9, 0xBE50, 0x8CCB, 0x9D42,
  0x7E9E, 0x6F17, 0x5D8C, 0x4C05, 0x38BA, 0x2933, 0x1BA8, 0x0A21,
  0xF2D6, 0xE35F, 0xD1C4, 0xC04D, 0xB4F2, 0xA57B, 0x97E0, 0x8669,
  0x7787, 0x660E, 0x5495, 0x451C, 0x31A3, 0x202A, 0x12B1, 0x0338,
  0xFBCF, 0xEA46, 0xD8DD, 0xC954, 0xBDEB, 0xAC62, 0x9EF9, 0x8F70
  };
  unsigned int // Returns Calculated CRC value
  CalculateCRC16(
  unsigned int crc_seed, // Seed for CRC calculation
  void *c_ptr, // Pointer to byte array to perform CRC on
  unsigned int len) // Number of bytes to CRC
  {
  unsigned char *c = c_ptr;
  unsigned int crc = crc_seed;
  while (len--){
  crc = (crc << 8) ^ crctable[((crc >> 8) ^ *c++)];
  printf("%d", crc);
  }
  return (crc);
  }
  int main(){
      printf("%d", CalculateCRC16(0xFFFF, "123456789", 2));
   return 0;  
  }
  

Answer 1

清理完毕，准备出发:

#include <stdio.h>
#include <stdint.h>
static const uint16_t crctable[256] =
{
    0x0000, 0x1189, 0x2312, 0x329B, 0x4624, 0x57AD, 0x6536, 0x74BF,
    0x8C48, 0x9DC1, 0xAF5A, 0xBED3, 0xCA6C, 0xDBE5, 0xE97E, 0xF8F7,
    0x0919, 0x1890, 0x2A0B, 0x3B82, 0x4F3D, 0x5EB4, 0x6C2F, 0x7DA6,
    0x8551, 0x94D8, 0xA643, 0xB7CA, 0xC375, 0xD2FC, 0xE067, 0xF1EE,
    0x1232, 0x03BB, 0x3120, 0x20A9, 0x5416, 0x459F, 0x7704, 0x668D,
    0x9E7A, 0x8FF3, 0xBD68, 0xACE1, 0xD85E, 0xC9D7, 0xFB4C, 0xEAC5,
    0x1B2B, 0x0AA2, 0x3839, 0x29B0, 0x5D0F, 0x4C86, 0x7E1D, 0x6F94,
    0x9763, 0x86EA, 0xB471, 0xA5F8, 0xD147, 0xC0CE, 0xF255, 0xE3DC,
    0x2464, 0x35ED, 0x0776, 0x16FF, 0x6240, 0x73C9, 0x4152, 0x50DB,
    0xA82C, 0xB9A5, 0x8B3E, 0x9AB7, 0xEE08, 0xFF81, 0xCD1A, 0xDC93,
    0x2D7D, 0x3CF4, 0x0E6F, 0x1FE6, 0x6B59, 0x7AD0, 0x484B, 0x59C2,
    0xA135, 0xB0BC, 0x8227, 0x93AE, 0xE711, 0xF698, 0xC403, 0xD58A,
    0x3656, 0x27DF, 0x1544, 0x04CD, 0x7072, 0x61FB, 0x5360, 0x42E9,
    0xBA1E, 0xAB97, 0x990C, 0x8885, 0xFC3A, 0xEDB3, 0xDF28, 0xCEA1,
    0x3F4F, 0x2EC6, 0x1C5D, 0x0DD4, 0x796B, 0x68E2, 0x5A79, 0x4BF0,
    0xB307, 0xA28E, 0x9015, 0x819C, 0xF523, 0xE4AA, 0xD631, 0xC7B8,
    0x48C8, 0x5941, 0x6BDA, 0x7A53, 0x0EEC, 0x1F65, 0x2DFE, 0x3C77,
    0xC480, 0xD509, 0xE792, 0xF61B, 0x82A4, 0x932D, 0xA1B6, 0xB03F,
    0x41D1, 0x5058, 0x62C3, 0x734A, 0x07F5, 0x167C, 0x24E7, 0x356E,
    0xCD99, 0xDC10, 0xEE8B, 0xFF02, 0x8BBD, 0x9A34, 0xA8AF, 0xB926,
    0x5AFA, 0x4B73, 0x79E8, 0x6861, 0x1CDE, 0x0D57, 0x3FCC, 0x2E45,
    0xD6B2, 0xC73B, 0xF5A0, 0xE429, 0x9096, 0x811F, 0xB384, 0xA20D,
    0x53E3, 0x426A, 0x70F1, 0x6178, 0x15C7, 0x044E, 0x36D5, 0x275C,
    0xDFAB, 0xCE22, 0xFCB9, 0xED30, 0x998F, 0x8806, 0xBA9D, 0xAB14,
    0x6CAC, 0x7D25, 0x4FBE, 0x5E37, 0x2A88, 0x3B01, 0x099A, 0x1813,
    0xE0E4, 0xF16D, 0xC3F6, 0xD27F, 0xA6C0, 0xB749, 0x85D2, 0x945B,
    0x65B5, 0x743C, 0x46A7, 0x572E, 0x2391, 0x3218, 0x0083, 0x110A,
    0xE9FD, 0xF874, 0xCAEF, 0xDB66, 0xAFD9, 0xBE50, 0x8CCB, 0x9D42,
    0x7E9E, 0x6F17, 0x5D8C, 0x4C05, 0x38BA, 0x2933, 0x1BA8, 0x0A21,
    0xF2D6, 0xE35F, 0xD1C4, 0xC04D, 0xB4F2, 0xA57B, 0x97E0, 0x8669,
    0x7787, 0x660E, 0x5495, 0x451C, 0x31A3, 0x202A, 0x12B1, 0x0338,
    0xFBCF, 0xEA46, 0xD8DD, 0xC954, 0xBDEB, 0xAC62, 0x9EF9, 0x8F70
};
uint16_t // Returns Calculated CRC value
CalculateCRC16(
    uint16_t crc,      // Seed for CRC calculation
    const void *c_ptr, // Pointer to byte array to perform CRC on
    size_t len)        // Number of bytes to CRC
{
    const uint8_t *c = c_ptr;
    while (len--)
        crc = (crc << 8) ^ crctable[((crc >> 8) ^ *c++)];
    return crc;
}
int main()
{
    printf("%04xn", CalculateCRC16(0xFFFF, "123456789", 9));
    return 0;
}

Answer 2

现在我附近没有电脑。试一试:

crc = (crc <<8) ^ crctable [(unsigned char) (crc>> 8) ^ * c++];

Answer 3

这一行

crc = (crc << 8) ^ crctable[((crc >> 8) ^ *c++)];

((crc >> 8) ^ *c++)的

结果可能变成> 255，导致访问冲突。通过将索引屏蔽为可创建的

，确保结果总是0.255。

crc = (crc << 8) ^ crctable[((crc >> 8) ^ *c++) & 0x00FF];
// but you will need to clean up the result as its upper 16 bits
// are not guaranteed to be all 0
return crc & 0xffff;

或更好，结果CRC值，因为它确保CRC永远不会包含值> 0x0000ffff

crc = ( (crc << 8) ^ crctable[((crc >> 8) ^ *c++)] ) & 0xffff;

，你就会一切就绪。问题的基础是原始代码似乎是16位代码(其中int是16位)，而您正在使用32位编译器。

Answer 4

您正在使用的表似乎没有正确生成。前16项是正确的，但之后就发散了。我不认为你会有太多的运气解码CCITT CRC-16用它。

请参阅跨平台应用的CRC，以获得正确生成表的示例。

Answer 5

我使用了相同的CRC检查，在你的代码中，你只需要改变以下行:crc = (crc>> 8) ^ crctable [(crc ^ (* c++)), 0 xff];

Answer 6

该表列出了多项式的幂，为了避免在计算时在表中计算幂的错误，将多项式作为一个条目，同时作为初始值。使用Dartpad进行模拟:https://dartpad.dev/?null_safety=true

void main() {
  final int polynomial = 0x1189;
  final int initialValue = 0xFFFF;
  String crc16(String expression, int polynomial, int initialValue) {
    int checkSum = initialValue;
    for (int i = 0; i < expression.length; i++) {
      checkSum ^= (expression.codeUnitAt(i) << 8);
      for (int j = 0; j < 8; j++) {
        if (((checkSum <<= 1) & 0x10000) == 0x10000) checkSum ^= polynomial;
        checkSum &= 0xFFFF;
      }
    }
    return checkSum.toRadixString(16).toUpperCase();
  }
  print(crc16('123456789', polynomial, initialValue));
}

为了符合CRC16 CCITT，您应该使用多项式=0x1021和初始值= 0xFFFF。

https://www.gatevidyalay.com/cyclic-redundancy-check-crc-error-detection/对CRC有很好的解释