CRC-CCITT Lufft 校驗算法 c 代碼是原版本， java 與 c# 是依據c 版本翻譯而來

 

原版c 

 

/************************************************************************* Function: 16 bit CRC-CCITT calculation -------------------------------------------------------------------------- Call: calc_crc(unsigned short crc_buff, unsigned char input) -------------------------------------------------------------------------- Response: Newly calculated 16 bit CRC checksum -------------------------------------------------------------------------- Description: Calculates the checksum for 'input' in accordance with the CRC polynomial x^16 + x^12 + x^5 + 1. 'crc_buff' is the previously calculated checksum. This must be set to 0xFFFF at the beginning of a test sequence. *************************************************************************/

 unsigned short calc_crc(unsigned short crc_buff, unsigned char input) {
  unsigned char i; 
 unsigned short x16; // we’ll use this to hold the XOR mask 
 for (i=0; i<8; i++)  {   // XOR current D0 and next input bit to determine x16 value  
 if( (crc_buff & 0x0001) ^ (input & 0x01) )   
 x16 = 0x8408;  
 else   
 x16 = 0x0000;  
 // shift crc buffer  
 crc_buff = crc_buff >> 1;   
// XOR in the x16 value  
 crc_buff ^= x16;   
// shift input for next iteration  
 input = input >> 1;  
}  
return(crc_buff); 
} 

// ******************* MAIN ************************************ 
void main(void) {  
// example: CRC for 8 Bytes 
 unsigned char values[8] = {0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37}; 
 // initialise startvalue FFFFh 
 unsigned short crc = 0xFFFF; 
 // calculation 
 for(int n = 0; n < 8; n++)  
{  
 crc = calc_crc(crc, values[n]); 
 }  
// output  
printf("\ndata:  30h, 31h, 32h, 33h, 34h, 35h, 36h, 37h");  
printf("\nCRC:   %04Xh\n", crc);
 } 
 
java  版本

 

public static int calc_crc(int crc_buff, char input) {
        char i;
        int x16; 
        for (i=0; i<8; i++)    {
            if(( (crc_buff & 0x0001) ^ (input & 0x01))>0 )
                x16 = 0x8408;
            else
                x16 = 0x0000;
            crc_buff = crc_buff >> 1;
            crc_buff ^= x16;
            input = (char) (input >> 1);
        }
        return crc_buff;
    }
    
    public static void main(String[] args) {

 

        char values[] =    {0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37};
        int crc = 0xFFFF;
        for(int n = 0; n < values.length; n++){
            crc = calc_crc(crc, values[n]);
        }
        System.out.println(String.format("%04Xh", crc));
    }

 

c# 版本

  static void Main(string[] args)
        {

 byte[] values = new byte[] { 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37};
       
            int crc = 0xFFFF;
            for (int n = 0; n < values.Length; n++)
            {
                crc = calc_crc(crc, values[n]);
            }
            Console.WriteLine("\ndata: 30h, 31h, 32h, 33h, 34h, 35h, 36h, 37h");
            Console.WriteLine(string.Format("{0:X4}h", crc));
            Console.ReadKey();

        }

          
        public static int calc_crc(int crc_buff, byte input)
        {
            int i;
            int x16;
            for (i = 0; i <8; i++)
            {
                if (((crc_buff & 0x0001) ^ (input & 0x01)) > 0)
                    x16 = 0x8408;
                else
                    x16 = 0x0000;
                crc_buff = crc_buff >> 1;
                crc_buff ^= x16;
                input = (byte)(input >> 1);
            }
            return (crc_buff);
        }