Information Theory - Introduction to Cryptography with Java Applets - page 362

TABLE A2.4

Bit 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7

Unused D O G

0 0 0 1 1 0 1 1 1 0 0 0 1 1 0

0

else if (incoming.length()%3==2) incoming+=”[”;

byte[] original=incoming.getBytes();

BigInteger origNum=new BigInteger(1,original);
System.out.println(“Original string in binary:\n”+origNum.toString(2));

byte[] compressed=new byte[2*incoming.length()/3];

compress(original,compressed);

BigInteger compNum=new BigInteger(1,compressed);
System.out.println(“Compressed string in binary:\n”+compNum.toString(2));

}

public static void compress(byte[] o,byte[] c) {
for (int i=0,j=0;i<o.length-2;i+=3,j+=2) {
int c1=o[i]-posA;
int c2=o[i+1]-posA;
int c3=o[i+2]-posA;

int res1=0,res2=0;

//Do the first compressed byte
//Put 1st value shifted 2 bits up
res1=res1|(c1<<2);
//Put first 2 bits of 2nd value in lo position
res1=res1|(c2>>>3);

//Do the second compressed byte
//Put last 3 bits of 2nd value in high position-mask out first 5 bits
res2=res2|((c2&7)<<5);
//Put 3rd value in lo position
res2=res2|c3;