diff -r 0d277415ed02 -r d382dacfd73f rt/emul/mini/src/main/java/org/apidesign/bck2brwsr/emul/zip/Adler32.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rt/emul/mini/src/main/java/org/apidesign/bck2brwsr/emul/zip/Adler32.java	Tue Feb 26 16:54:16 2013 +0100
@@ -0,0 +1,139 @@
+/* -*-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 org.apidesign.bck2brwsr.emul.zip;
+
+final 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();
+  }
+*/
+}