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lele
CRC.h
- Committer:
- krishanprajapat
- Date:
- 2015-07-31
- Revision:
- 1:90fd52655154
- Parent:
- 0:984643af7d81
File content as of revision 1:90fd52655154:
//EDITS //changed the initial remainder from 0x0000 to 0xffff according to the standards //made two seperate functions crc16_gen and crc8_gen #define TOPBIT16 (1 << 15) #define TOPBIT8 (1 << 7) #define POLYNOMIAL16 0x1021 #define POLYNOMIAL8 0xEA namespace CRC{ typedef unsigned short int crctype16; crctype16 crc16_gen(const unsigned char message[], unsigned int nBytes){ crctype16 remainder = 0xffff; int byte; char bit; for( byte = 0 ; byte < nBytes ; byte++ ){ /* Bring the data byte by byte each time only one byte is brought 0 xor x = x */ remainder = remainder ^ ( message[byte] << 8 ); for( bit = 8 ; bit > 0 ; bit--){ /* for each bit, xor the remainder with polynomial if the MSB is 1 */ if(remainder & TOPBIT16){ remainder = (remainder << 1) ^ POLYNOMIAL16; /* each time the remainder is xor-ed with polynomial, the MSB is made zero hence the first digit of the remainder is ignored in the loop */ } else{ remainder = (remainder << 1); } } } return remainder; } typedef unsigned char crctype8; crctype8 crc8_gen(const unsigned char message[], unsigned int nBytes){ crctype8 remainder = 0xff; for(int byte = 0 ; byte < nBytes ; byte++ ){ /* Bring the data byte by byte each time only one byte is brought 0 xor x = x */ remainder = remainder ^ ( message[byte] ); for(int bit = 8 ; bit > 0 ; bit--){ /* for each bit, xor the remainder with polynomial if the MSB is 1 */ if(remainder & TOPBIT8){ remainder = (remainder << 1) ^ POLYNOMIAL8; /* each time the remainder is xor-ed with polynomial, the MSB is made zero hence the first digit of the remainder is ignored in the loop */ } else{ remainder = (remainder << 1); } } } return remainder; } }