Hi everybody, would you like to help me please ?
i am very confuse about Exercise 4.2 at Lab-1022, what is the Checksum and
Adler32, what is that function?
and what is this following codes mean ?
public class Adler32 implements Checksum {
private int value = 1;
/*
* BASE is the largest prime number smaller than 65536
* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1
*/
private static final int BASE = 65521;
private static final int NMAX = 5552;
/**
* Update current Adler-32 checksum given the specified byte.
*/
public void update(int b) {
int s1 = value & 0xffff;
int s2 = (value >> 16) & 0xffff;
s1 += b & 0xff;
s2 += s1;
value = ((s2 % BASE) << 16) | (s1 % BASE);
}
/**
* Update current Adler-32 checksum given the specified byte array.
*/
public void update(byte[] b, int off, int len) {
int s1 = value & 0xffff;
int s2 = (value >> 16) & 0xffff;
while (len > 0) {
int k = len < NMAX ? len : NMAX;
len -= k;
while (k-- > 0) {
s1 += b[off++] & 0xff;
s2 += s1;
}
s1 %= BASE;
s2 %= BASE;
}
value = (s2 << 16) | s1;
}
/**
* Reset Adler-32 checksum to initial value.
*/
public void reset() {
value = 1;
}
/**
* Returns current checksum value.
*/
public long getValue() {
return (long)value & 0xffffffff;
}
}
=-=-===================--==-=-===========-==-=-==-==================
After exercise 4.2, i have few questions again about the homework,
how did you do to convert the characters to upper case?
Did you use any java methods or use a *bit operation* (bitwise) to convert
characters to uppercase ?
May we use the arithmetic operator like this code, to convert it ?
ex :
*int x = 'a';
int y = x-32; //minus
//so the value of y is 65
System.out.printf("%c",y);
--> output = A
*
because the x decimal value is 97 and a hexadecimal value is 61,
and i know the decimal value of *'A' =65*, so i substract the value of x
with 32 and give to y.
Please help me, i have got few problems are difficult to understand in this
Lab-1022
*I am sorry if i my english is not good. Thanks*
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to [EMAIL PROTECTED]
For more options, visit this group at
http://groups.google.com/group/javaprogrammingwithpassion?hl=en
-~----------~----~----~----~------~----~------~--~---
