Implementing CRC16 parity code with Java

1. Design

2. Code

import java.io.IOException;


public class Crc16checker {


private static int[] index = new int[] {16, 15, 2, 0};


private static int[] Getbinary (String text) {


StringBuffer num = new StringBuffer ();


String S; Char ch;


for (int i = 0; i < text.length (); i++) {//change per char to binary code.


s = integer.tobinarystring (Text.charat (i));


//If The code is less than 8 bit and make it as 8 bit.


for (int j = 8-s.length (); j > 0; j--) num.append (0);


Num.append (s);


　　　　　　　　　　　　 }


int len = Num.length ();


Int[] Code = new Int[len];


for (int i = 0; i < len; i++)//change per 0/1 char to int.


Code[i] = Character.getnumericvalue (Num.charat (i));


return code;


　　　　　　 }


private static String Tohex (int[] num) {


stringbuffer hex = new StringBuffer (NUM.LENGTH/4);


char[] ch = new CHAR[4];


for (int i = 0; i < num.length;) {


//change all 0/1 int to char.


ch[0] = Character.fordigit (num[i++], 2);


ch[1] = Character.fordigit (num[i++], 2);


ch[2] = Character.fordigit (num[i++], 2);


ch[3] = Character.fordigit (num[i++], 2);


//change per 4-bit-code to hex number.


hex.append (integer.tohexstring (Integer.parseint (string.valueof (CH), 2));


　　　　　　　　　　　　 }


return hex.tostring ();


　　　　　　 }


//CRC codes main process


public static int[] Makecrccodes (int[] sourcecodes, int[] multinomial) {


//The lenght of CRC code is N bits longer than source code. The Codes


//From 0 to Sourcelength are same as the source. N bits after source


//are the CRC codes. N is decided by the multinomial.


//CRC code array length of the original code length plus check code length. The front of the array stores the original code. Check code stored in array


//last n bit. The length of the checksum code is determined by the generation of elements on the 0 position of the polynomial array.


int sourcelength = sourcecodes.length;


int codeslength = sourcelength + multinomial[0];


int[] crccodes = new Int[codeslength];


Copy source code from 0 to Sourcelength. Copy the original code.


system.arraycopy (sourcecodes, 0, crccodes, 0, sourcelength);


int temp, POS;


//Division system. Divider.


for (int i = 0; i < sourcelength; i++) {


//Count value of the input adding.


//With the first and second register value modulo two plus.


temp = (Crccodes[sourcelength] + sourcecodes[i])% 2;


//Move registers forwards from (1, length) to (0, length-1).

The
//second register and all subsequent register values move forward 1 digits.


System.arraycopy (


Crccodes, Sourcelength + 1, crccodes, Sourcelength, multinomial[0]-1);


//Set The last register with counted value.


The last register value holds the calculated input value.


crccodes[codeslength-1] = temp;


//Count other registers. The position is calculated by the value of the generated polynomial, and modulo two adds the value of the register.


for (int j = Index.length-2 J > 0; j--) {


pos = codeslength-multinomial[j]-1;


Crccodes[pos] = (Crccodes[pos] + temp)% 2;


　　　　　　　　　　　　　　　　　　 }


　　　　　　　　　　　　 }


return crccodes;


　　　　　　 }


public static void Main (string[] args) throws IOException {


System.out.print ("Input hex Data:");


StringBuffer buf = new StringBuffer ();


char ch = (char) System.in.read ();


while (ch!= ' \ R ' && ch!= ' \ n ') {


buf.append (CH);


ch = (char) System.in.read ();


　　　　　　　　　　　　 }


//Get binary codes.


int[] B = crc16checker.getbinary (buf.tostring ());


//Make CRC codes.


B = crc16checker.makecrccodes (b, Crc16checker.index);


//Output code as binary number.


for (int i = 0; i < b.length;) {


for (int j = 0; J < 4; J + +, i++) System.out.print (b[i));


System.out.print (");


　　　　　　　　　　　　 }


System.out.println ();


//Output code as hex number.


System.out.println ("The CRC16 Code is:" + Crc16checker.tohex (b));


　　　　　　 }


}

3. Test:

Case : A （ASCII = 41）
Result : 410186
CRC bits : 0168 （0000 0001 1000 0110）
Run program :
Input hex data :A
0100 0001 0000 0001 1000 0110
The CRC16 code is :410186
Case : CRC16TEST （ASCII = 43 52 43 31 36 54 45 53 54）
Result : 455243313654455354fb66
CRC bits : fb66 （1111 1011 0110 0110）
Run program :
Input hex data :CRC16TEST
0100 0011 0101 0010 0100 0011 0011 0001 0011 0110 0101 0100 0100 0101 0101 0011 0101 0100 1111 1011 0110 0110
The CRC16 code is :435243313654455354fb66
Case : 5k （ASCII = 35 6b）
Result : 356b3f79
CRC bits : 3f79 （0011 1111 0111 1001）
Run program :
Input hex data :5k
0011 0101 0110 1011 0011 1111 0111 1001
The CRC16 code is :356b3f79