jaroslav@694: /* -*-mode:java; c-basic-offset:2; -*- */
jaroslav@694: /*
jaroslav@694: Copyright (c) 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: import org.apidesign.bck2brwsr.emul.lang.System;
jaroslav@694: 
jaroslav@694: final class CRC32 implements Checksum {
jaroslav@694: 
jaroslav@694:   /*
jaroslav@694:    *  The following logic has come from RFC1952.
jaroslav@694:    */
jaroslav@694:   private int v = 0;
jaroslav@694:   private static int[] crc_table = null;
jaroslav@694:   static {
jaroslav@694:     crc_table = new int[256];
jaroslav@694:     for (int n = 0; n < 256; n++) {
jaroslav@694:       int c = n;
jaroslav@694:       for (int k = 8;  --k >= 0; ) {
jaroslav@694:         if ((c & 1) != 0)
jaroslav@694: 	  c = 0xedb88320 ^ (c >>> 1);
jaroslav@694:         else
jaroslav@694:           c = c >>> 1;
jaroslav@694:       }
jaroslav@694:       crc_table[n] = c;
jaroslav@694:     }
jaroslav@694:   }
jaroslav@694: 
jaroslav@694:   public void update (byte[] buf, int index, int len) {
jaroslav@694:     int c = ~v;
jaroslav@694:     while (--len >= 0)
jaroslav@694:       c = crc_table[(c^buf[index++])&0xff]^(c >>> 8);
jaroslav@694:     v = ~c;
jaroslav@694:   }
jaroslav@694: 
jaroslav@694:   public void reset(){
jaroslav@694:     v = 0;
jaroslav@694:   }
jaroslav@694: 
jaroslav@694:   public void reset(long vv){
jaroslav@694:     v = (int)(vv&0xffffffffL);
jaroslav@694:   }
jaroslav@694: 
jaroslav@694:   public long getValue(){
jaroslav@694:     return (long)(v&0xffffffffL);
jaroslav@694:   }
jaroslav@694: 
jaroslav@694:   // The following logic has come from zlib.1.2.
jaroslav@694:   private static final int GF2_DIM = 32;
jaroslav@694:   static long combine(long crc1, long crc2, long len2){
jaroslav@694:     long row;
jaroslav@694:     long[] even = new long[GF2_DIM];
jaroslav@694:     long[] odd = new long[GF2_DIM];
jaroslav@694: 
jaroslav@694:     // degenerate case (also disallow negative lengths)
jaroslav@694:     if (len2 <= 0)
jaroslav@694:       return crc1;
jaroslav@694: 
jaroslav@694:     // put operator for one zero bit in odd
jaroslav@694:     odd[0] = 0xedb88320L;          // CRC-32 polynomial
jaroslav@694:     row = 1;
jaroslav@694:     for (int n = 1; n < GF2_DIM; n++) {
jaroslav@694:         odd[n] = row;
jaroslav@694:         row <<= 1;
jaroslav@694:     }
jaroslav@694: 
jaroslav@694:     // put operator for two zero bits in even
jaroslav@694:     gf2_matrix_square(even, odd);
jaroslav@694: 
jaroslav@694:     // put operator for four zero bits in odd
jaroslav@694:     gf2_matrix_square(odd, even);
jaroslav@694: 
jaroslav@694:     // apply len2 zeros to crc1 (first square will put the operator for one
jaroslav@694:     // zero byte, eight zero bits, in even)
jaroslav@694:     do {
jaroslav@694:       // apply zeros operator for this bit of len2
jaroslav@694:       gf2_matrix_square(even, odd);
jaroslav@694:       if ((len2 & 1)!=0)
jaroslav@694:         crc1 = gf2_matrix_times(even, crc1);
jaroslav@694:       len2 >>= 1;
jaroslav@694: 
jaroslav@694:       // if no more bits set, then done
jaroslav@694:       if (len2 == 0)
jaroslav@694:         break;
jaroslav@694: 
jaroslav@694:       // another iteration of the loop with odd and even swapped
jaroslav@694:       gf2_matrix_square(odd, even);
jaroslav@694:       if ((len2 & 1)!=0)
jaroslav@694:         crc1 = gf2_matrix_times(odd, crc1);
jaroslav@694:       len2 >>= 1;
jaroslav@694: 
jaroslav@694:       // if no more bits set, then done
jaroslav@694:     } while (len2 != 0);
jaroslav@694: 
jaroslav@694:     /* return combined crc */
jaroslav@694:     crc1 ^= crc2;
jaroslav@694:     return crc1;
jaroslav@694:   }
jaroslav@694: 
jaroslav@694:   private static long gf2_matrix_times(long[] mat, long vec){
jaroslav@694:     long sum = 0;
jaroslav@694:     int index = 0;
jaroslav@694:     while (vec!=0) {
jaroslav@694:       if ((vec & 1)!=0)
jaroslav@694:         sum ^= mat[index];
jaroslav@694:       vec >>= 1;
jaroslav@694:       index++;
jaroslav@694:     }
jaroslav@694:     return sum;
jaroslav@694:   }
jaroslav@694: 
jaroslav@694:   static final void gf2_matrix_square(long[] square, long[] mat) {
jaroslav@694:     for (int n = 0; n < GF2_DIM; n++)
jaroslav@694:       square[n] = gf2_matrix_times(mat, mat[n]);
jaroslav@694:   }
jaroslav@694: 
jaroslav@694:   /*
jaroslav@694:   private java.util.zip.CRC32 crc32 = new java.util.zip.CRC32();
jaroslav@694: 
jaroslav@694:   public void update(byte[] buf, int index, int len){
jaroslav@694:     if(buf==null) {crc32.reset();}
jaroslav@694:     else{crc32.update(buf, index, len);}
jaroslav@694:   }
jaroslav@694:   public void reset(){
jaroslav@694:     crc32.reset();
jaroslav@694:   }
jaroslav@694:   public void reset(long init){
jaroslav@694:     if(init==0L){
jaroslav@694:       crc32.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 crc32.getValue();
jaroslav@694:   }
jaroslav@694: */
jaroslav@694:   public CRC32 copy(){
jaroslav@694:     CRC32 foo = new CRC32();
jaroslav@694:     foo.v = this.v;
jaroslav@694:     return foo;
jaroslav@694:   }
jaroslav@694: 
jaroslav@694:   public static int[] getCRC32Table(){
jaroslav@694:     int[] tmp = new int[crc_table.length];
jaroslav@694:     System.arraycopy(crc_table, 0, tmp, 0, tmp.length);
jaroslav@694:     return tmp;
jaroslav@694:   }
jaroslav@694: }