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  1. #include <stdio.h>
  2. #include <stdint.h>
  3. #include <stdbool.h>
  4.  
  5. uint16_t MyCrc16(const unsigned char *data, int length, uint16_t poly, uint16_t crc)
  6. {
  7.         for(int byte=0; byte<length; ++byte)
  8.         {
  9.                 for(int bit=7; bit>=0; --bit)
  10.                 {
  11.                         bool doXor = false;
  12.                         if(crc & 0x8000)
  13.                         {
  14.                                 doXor = true;
  15.                         }
  16.                         crc <<= 1;
  17.                         if(data[byte] & (1 << bit))
  18.                         {
  19.                                 crc += 1;
  20.                         }
  21.                         if(doXor)
  22.                         {
  23.                                 crc ^= poly;
  24.                         }
  25.                 }
  26.         }
  27.  
  28.         //augument the crc with 0s
  29.         for(int i=0; i<16; i++)
  30.         {
  31.                 bool doXor = false;
  32.                 if(crc & 0x8000)
  33.                 {
  34.                         doXor = true;
  35.                 }
  36.  
  37.                 crc = crc << 1;
  38.                 if(doXor)
  39.                 {
  40.                         crc ^= poly;
  41.                 }
  42.         }
  43.  
  44.         return crc;
  45. }
  46.  
  47. uint16_t OtherCrc16(const unsigned char *data, int length, uint16_t poly, uint16_t crc)
  48. {
  49.         for(int i=0; i<length; i++)
  50.         {
  51.                 crc = crc ^ (data[i] << 8);
  52.                 for (int bit = 0; bit< 8; bit++)
  53.                 {
  54.                         bool doXor = false;
  55.                         if(crc & 0x8000)
  56.                         {
  57.                                 doXor = true;
  58.                         }
  59.                         crc <<=1;
  60.  
  61.                         if(doXor)
  62.                         {
  63.                                 crc ^= poly;
  64.                         }
  65.                 }
  66.         }
  67.         return crc;
  68. }
  69.  
  70.  
  71. int main(void) {
  72. 	// your code goes here
  73. 	uint16_t poly = 0x1021;
  74.  
  75. 	unsigned char c[] = "123456789";
  76. 	printf("My CRC = %04x\n", MyCrc16(c, 9, poly, 0xffff));
  77. 	printf("Other CRC = %04x\n", OtherCrc16(c, 9, poly, 0xffff));
  78. 	return 0;
  79. }
  80.  
Success #stdin #stdout 0s 2168KB
comments ()
stdin 
Standard input is empty
stdout 
My CRC = e5cc
Other CRC = 29b1
https://ideone.com/mKuQqQ
language:
C (gcc 8.3)
created:
8 years ago
visibility:
public

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