/* -*-mode:java; c-basic-offset:2; -*- */
/*
Copyright (c) 2000-2011 ymnk, JCraft,Inc. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
1. Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the distribution.
3. The names of the authors may not be used to endorse or promote products
derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JCRAFT,
INC. OR ANY CONTRIBUTORS TO THIS SOFTWARE BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* This program is based on zlib-1.1.3, so all credit should go authors
* Jean-loup Gailly(jloup@gzip.org) and Mark Adler(madler@alumni.caltech.edu)
* and contributors of zlib.
*/
package com.jcraft.jzlib;
final public class
Adler32 implements
Checksum {
// largest prime smaller than 65536
static final private int
BASE=65521;
// NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1
static final private int
NMAX=5552;
private long
s1=1L;
private long
s2=0L;
public void
reset(long
init){
s1=
init&0xffff;
s2=(
init>>16)&0xffff;
}
public void
reset(){
s1=1L;
s2=0L;
}
public long
getValue(){
return ((
s2<<16)|
s1);
}
public void
update(byte[]
buf, int
index, int
len){
if(
len==1){
s1+=
buf[
index++]&0xff;
s2+=
s1;
s1%=
BASE;
s2%=
BASE;
return;
}
int
len1 =
len/
NMAX;
int
len2 =
len%
NMAX;
while(
len1-->0) {
int
k=
NMAX;
len-=
k;
while(
k-->0){
s1+=
buf[
index++]&0xff;
s2+=
s1;
}
s1%=
BASE;
s2%=
BASE;
}
int
k=
len2;
len-=
k;
while(
k-->0){
s1+=
buf[
index++]&0xff;
s2+=
s1;
}
s1%=
BASE;
s2%=
BASE;
}
public
Adler32 copy(){
Adler32 foo = new
Adler32();
foo.
s1 = this.
s1;
foo.
s2 = this.
s2;
return
foo;
}
// The following logic has come from zlib.1.2.
static long
combine(long
adler1, long
adler2, long
len2){
long
BASEL = (long)
BASE;
long
sum1;
long
sum2;
long
rem; // unsigned int
rem =
len2 %
BASEL;
sum1 =
adler1 & 0xffffL;
sum2 =
rem *
sum1;
sum2 %=
BASEL; // MOD(sum2);
sum1 += (
adler2 & 0xffffL) +
BASEL - 1;
sum2 += ((
adler1 >> 16) & 0xffffL) + ((
adler2 >> 16) & 0xffffL) +
BASEL -
rem;
if (
sum1 >=
BASEL)
sum1 -=
BASEL;
if (
sum1 >=
BASEL)
sum1 -=
BASEL;
if (
sum2 >= (
BASEL << 1))
sum2 -= (
BASEL << 1);
if (
sum2 >=
BASEL)
sum2 -=
BASEL;
return
sum1 | (
sum2 << 16);
}
/*
private java.util.zip.Adler32 adler=new java.util.zip.Adler32();
public void update(byte[] buf, int index, int len){
if(buf==null) {adler.reset();}
else{adler.update(buf, index, len);}
}
public void reset(){
adler.reset();
}
public void reset(long init){
if(init==1L){
adler.reset();
}
else{
System.err.println("unsupported operation");
}
}
public long getValue(){
return adler.getValue();
}
*/
}