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  1. #include <iostream>
  2.  
  3. unsigned char get_crc(unsigned char *packet) {
  4.  
  5.   unsigned short POLY  = 0x125;
  6.   unsigned short CARRY = 0x100;
  7.   unsigned char  mask  = 0x80;
  8.   unsigned short reg   = 0;
  9.  
  10.   for (int byte = 0; byte < 7; byte++) {
  11.     mask = 0x80;
  12.     for(int bit = 0; bit < 8; bit++) {
  13.       reg <<= 1;
  14.       if(packet[byte] & mask) reg |= 1;
  15.       mask >>=1;
  16.       if(reg & CARRY) reg^=POLY;
  17.     }
  18.   }
  19.   return reg & 0xFF; 
  20. }
  21.  
  22. int main() {
  23. 	unsigned char packet[7] = {'1', 'h', 'e', 'l', 'l', 'o','0'};
  24. 	unsigned char crc = get_crc(packet);
  25. 	packet[6] = crc;
  26. 	std::cout << "CRC: " << (int)crc << std::endl;
  27. 	std::cout << (int)get_crc(packet) << std::endl;
  28. }
Success #stdin #stdout 0s 16064KB
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Standard input is empty
stdout
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CRC: 106
48
https://ideone.com/7byrpM
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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