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/* -*-mode:java; c-basic-offset:2; -*- */
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/*
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Copyright (c) 2000-2011 ymnk, JCraft,Inc. All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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1. Redistributions of source code must retain the above copyright notice,
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this list of conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the distribution.
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3. The names of the authors may not be used to endorse or promote products
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derived from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
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INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JCRAFT,
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INC. OR ANY CONTRIBUTORS TO THIS SOFTWARE BE LIABLE FOR ANY DIRECT, INDIRECT,
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INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
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OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
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EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* This program is based on zlib-1.1.3, so all credit should go authors
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* Jean-loup Gailly(jloup@gzip.org) and Mark Adler(madler@alumni.caltech.edu)
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* and contributors of zlib.
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*/
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package org.apidesign.bck2brwsr.emul.zip;
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final class Adler32 implements Checksum {
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// largest prime smaller than 65536
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static final private int BASE=65521;
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// NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1
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static final private int NMAX=5552;
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private long s1=1L;
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private long s2=0L;
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public void reset(long init){
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s1=init&0xffff;
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s2=(init>>16)&0xffff;
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}
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public void reset(){
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s1=1L;
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s2=0L;
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}
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public long getValue(){
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return ((s2<<16)|s1);
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}
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public void update(byte[] buf, int index, int len){
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if(len==1){
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s1+=buf[index++]&0xff; s2+=s1;
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s1%=BASE;
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s2%=BASE;
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return;
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}
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int len1 = len/NMAX;
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int len2 = len%NMAX;
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while(len1-->0) {
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int k=NMAX;
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len-=k;
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while(k-->0){
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s1+=buf[index++]&0xff; s2+=s1;
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}
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s1%=BASE;
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s2%=BASE;
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}
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int k=len2;
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len-=k;
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while(k-->0){
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s1+=buf[index++]&0xff; s2+=s1;
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}
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s1%=BASE;
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s2%=BASE;
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}
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public Adler32 copy(){
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Adler32 foo = new Adler32();
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foo.s1 = this.s1;
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foo.s2 = this.s2;
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return foo;
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}
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// The following logic has come from zlib.1.2.
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static long combine(long adler1, long adler2, long len2){
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long BASEL = (long)BASE;
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long sum1;
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long sum2;
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long rem; // unsigned int
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rem = len2 % BASEL;
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sum1 = adler1 & 0xffffL;
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sum2 = rem * sum1;
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sum2 %= BASEL; // MOD(sum2);
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sum1 += (adler2 & 0xffffL) + BASEL - 1;
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sum2 += ((adler1 >> 16) & 0xffffL) + ((adler2 >> 16) & 0xffffL) + BASEL - rem;
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if (sum1 >= BASEL) sum1 -= BASEL;
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if (sum1 >= BASEL) sum1 -= BASEL;
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if (sum2 >= (BASEL << 1)) sum2 -= (BASEL << 1);
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if (sum2 >= BASEL) sum2 -= BASEL;
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return sum1 | (sum2 << 16);
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}
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/*
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private java.util.zip.Adler32 adler=new java.util.zip.Adler32();
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public void update(byte[] buf, int index, int len){
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if(buf==null) {adler.reset();}
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else{adler.update(buf, index, len);}
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}
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public void reset(){
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adler.reset();
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}
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public void reset(long init){
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if(init==1L){
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adler.reset();
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}
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else{
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System.err.println("unsupported operation");
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}
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}
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public long getValue(){
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return adler.getValue();
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}
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*/
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}
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