jaroslav@694: /* -*-mode:java; c-basic-offset:2; -*- */
jaroslav@694: /*
jaroslav@694: Copyright (c) 2000-2011 ymnk, JCraft,Inc. All rights reserved.
jaroslav@694: 
jaroslav@694: Redistribution and use in source and binary forms, with or without
jaroslav@694: modification, are permitted provided that the following conditions are met:
jaroslav@694: 
jaroslav@694:   1. Redistributions of source code must retain the above copyright notice,
jaroslav@694:      this list of conditions and the following disclaimer.
jaroslav@694: 
jaroslav@694:   2. Redistributions in binary form must reproduce the above copyright 
jaroslav@694:      notice, this list of conditions and the following disclaimer in 
jaroslav@694:      the documentation and/or other materials provided with the distribution.
jaroslav@694: 
jaroslav@694:   3. The names of the authors may not be used to endorse or promote products
jaroslav@694:      derived from this software without specific prior written permission.
jaroslav@694: 
jaroslav@694: THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
jaroslav@694: INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
jaroslav@694: FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JCRAFT,
jaroslav@694: INC. OR ANY CONTRIBUTORS TO THIS SOFTWARE BE LIABLE FOR ANY DIRECT, INDIRECT,
jaroslav@694: INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
jaroslav@694: LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
jaroslav@694: OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
jaroslav@694: LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
jaroslav@694: NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
jaroslav@694: EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
jaroslav@694:  */
jaroslav@694: /*
jaroslav@694:  * This program is based on zlib-1.1.3, so all credit should go authors
jaroslav@694:  * Jean-loup Gailly(jloup@gzip.org) and Mark Adler(madler@alumni.caltech.edu)
jaroslav@694:  * and contributors of zlib.
jaroslav@694:  */
jaroslav@694: 
jaroslav@694: package org.apidesign.bck2brwsr.emul.zip;
jaroslav@694: 
jaroslav@694: final class Adler32 implements Checksum {
jaroslav@694: 
jaroslav@694:   // largest prime smaller than 65536
jaroslav@694:   static final private int BASE=65521; 
jaroslav@694:   // NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1
jaroslav@694:   static final private int NMAX=5552;
jaroslav@694: 
jaroslav@694:   private long s1=1L;
jaroslav@694:   private long s2=0L;
jaroslav@694: 
jaroslav@694:   public void reset(long init){
jaroslav@694:     s1=init&0xffff;
jaroslav@694:     s2=(init>>16)&0xffff;
jaroslav@694:   }
jaroslav@694: 
jaroslav@694:   public void reset(){
jaroslav@694:     s1=1L;
jaroslav@694:     s2=0L;
jaroslav@694:   }
jaroslav@694: 
jaroslav@694:   public long getValue(){
jaroslav@694:     return ((s2<<16)|s1);
jaroslav@694:   }
jaroslav@694: 
jaroslav@694:   public void update(byte[] buf, int index, int len){
jaroslav@694: 
jaroslav@694:     if(len==1){
jaroslav@694:       s1+=buf[index++]&0xff; s2+=s1;
jaroslav@694:       s1%=BASE;
jaroslav@694:       s2%=BASE;
jaroslav@694:       return;
jaroslav@694:     }
jaroslav@694: 
jaroslav@694:     int len1 = len/NMAX;
jaroslav@694:     int len2 = len%NMAX;
jaroslav@694:     while(len1-->0) {
jaroslav@694:       int k=NMAX;
jaroslav@694:       len-=k;
jaroslav@694:       while(k-->0){
jaroslav@694: 	s1+=buf[index++]&0xff; s2+=s1;
jaroslav@694:       }
jaroslav@694:       s1%=BASE;
jaroslav@694:       s2%=BASE;
jaroslav@694:     }
jaroslav@694: 
jaroslav@694:     int k=len2;
jaroslav@694:     len-=k;
jaroslav@694:     while(k-->0){
jaroslav@694:       s1+=buf[index++]&0xff; s2+=s1;
jaroslav@694:     }
jaroslav@694:     s1%=BASE;
jaroslav@694:     s2%=BASE;
jaroslav@694:   }
jaroslav@694: 
jaroslav@694:   public Adler32 copy(){
jaroslav@694:     Adler32 foo = new Adler32();
jaroslav@694:     foo.s1 = this.s1;
jaroslav@694:     foo.s2 = this.s2;
jaroslav@694:     return foo;
jaroslav@694:   }
jaroslav@694: 
jaroslav@694:   // The following logic has come from zlib.1.2.
jaroslav@694:   static long combine(long adler1, long adler2, long len2){
jaroslav@694:     long BASEL = (long)BASE;
jaroslav@694:     long sum1;
jaroslav@694:     long sum2;
jaroslav@694:     long rem;  // unsigned int
jaroslav@694: 
jaroslav@694:     rem = len2 % BASEL;
jaroslav@694:     sum1 = adler1 & 0xffffL;
jaroslav@694:     sum2 = rem * sum1;
jaroslav@694:     sum2 %= BASEL; // MOD(sum2);
jaroslav@694:     sum1 += (adler2 & 0xffffL) + BASEL - 1;
jaroslav@694:     sum2 += ((adler1 >> 16) & 0xffffL) + ((adler2 >> 16) & 0xffffL) + BASEL - rem;
jaroslav@694:     if (sum1 >= BASEL) sum1 -= BASEL;
jaroslav@694:     if (sum1 >= BASEL) sum1 -= BASEL;
jaroslav@694:     if (sum2 >= (BASEL << 1)) sum2 -= (BASEL << 1);
jaroslav@694:     if (sum2 >= BASEL) sum2 -= BASEL;
jaroslav@694:     return sum1 | (sum2 << 16);
jaroslav@694:   }
jaroslav@694: 
jaroslav@694: /*
jaroslav@694:   private java.util.zip.Adler32 adler=new java.util.zip.Adler32();
jaroslav@694:   public void update(byte[] buf, int index, int len){
jaroslav@694:     if(buf==null) {adler.reset();}
jaroslav@694:     else{adler.update(buf, index, len);}
jaroslav@694:   }
jaroslav@694:   public void reset(){
jaroslav@694:     adler.reset();
jaroslav@694:   }
jaroslav@694:   public void reset(long init){
jaroslav@694:     if(init==1L){
jaroslav@694:       adler.reset();
jaroslav@694:     }
jaroslav@694:     else{
jaroslav@694:       System.err.println("unsupported operation");
jaroslav@694:     }
jaroslav@694:   }
jaroslav@694:   public long getValue(){
jaroslav@694:     return adler.getValue();
jaroslav@694:   }
jaroslav@694: */
jaroslav@694: }