File content as of revision 4:560716ec8414:

//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 uint16_t 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 uint8_t 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;
    }
}