Introduction to Microservice Architecture Using SpringBoot - Part 1

Cyclic redundancy check (CRC)

• Unlike checksum scheme, which is based on addition, CRC is based on binary division.
• In CRC, a sequence of redundant bits, called cyclic redundancy check bits, are appended to the end of data unit so that the resulting data unit becomes exactly divisible by a second, predetermined binary number.
• At the destination, the incoming data unit is divided by the same number. If at this step there is no remainder, the data unit is assumed to be correct and is therefore accepted.
• A remainder indicates that the data unit has been damaged in transit and therefore must be rejected.

CODE 

 import java.util.*;  
 public class CRC  
 {  
   public static void main(String[] args)  
   {  
     Scanner sc= new Scanner(System.in);  
     System.out.println("Enter the data size:");  
     int n=sc.nextInt();  
     System.out.println("Enter the data :");  
     int[] data= new int[n];  
     for(int i=0;i<n;i++)  
     {  
       data[i]=sc.nextInt();  
     }  
     System.out.println("Enter the divisor size:");   
     int m=sc.nextInt();  
     int[] div= new int[m];  
     System.out.println("Enter the divisor:"); 
     for(int i=0;i<m;i++)  
     {  
       div[i]=sc.nextInt();  
     }  
     int[] crc=senddata(data,div,n,m);  
     System.out.println("CRC DATA : "+Arrays.toString(crc));  
     int[] rem =receivedata(crc,div);  
     System.out.print("receiver remainder : "+Arrays.toString(rem));  
   }  
   public static int[] senddata(int[]data,int[]div,int n,int m)  
   {  
     int[] d= new int[m+n-1];  
     int[] temp= new int[m+n-1];  
     for(int i=0;i<n;i++)  
     {  
       d[i]=data[i];  
       temp[i]=data[i];  
     }  
     int[] rem=divide(temp,div);  
     int[] crc=new int[m+n-1];  
     for(int i=0;i<n+m-1;i++)  
     {  
       crc[i]=d[i]|rem[i];  
     }  
     return crc;  
   }  
   public static int[] receivedata(int[] crc,int[]div)  
   {  
     return divide(crc,div);  
   }  
   public static int[] divide(int[]temp,int[]div)  
   {  
     int cur=0;  
     while(true)  
     {  
       for(int i=0;i<div.length;i++)  
       {    
         temp[cur+i]=temp[cur+i]^div[i];  
       }  
       while(temp[cur]==0 && cur<temp.length-1)  
         cur++;  
       if(temp.length-cur<div.length)  
         break;  
     }  
     return temp;  
   }  
 }  

OUTPUT :

Enter the data size:

6

Enter the data :

1

1

1

1

0

1

Enter the divisor size:

4

Enter the divisor:

1

1

0

1

CRC DATA : [1, 1, 1, 1, 0, 1, 0, 1, 1]

receiver remainder : [0, 0, 0, 0, 0, 0, 0, 0, 0]