text: /* adler32.c -- compute the Adler-32 checksum of a data stream
   * Copyright (C) 1995-1998 Mark Adler
   * For conditions of distribution and use, see copyright notice in zlib.h
   */
  
  /* @(#) $Id$ */
  
  #if defined( INC_ALL ) || defined( INC_CHILD )
    #include "zlib.h"
  #else
    #include "zlib/zlib.h"
  #endif /* Compiler-specific includes */
  
  #define BASE 65521L /* largest prime smaller than 65536 */
  #define NMAX 5552
  /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
  
  #define DO1(buf,i)  {s1 += buf[i]; s2 += s1;}
  #define DO2(buf,i)  DO1(buf,i); DO1(buf,i+1);
  #define DO4(buf,i)  DO2(buf,i); DO2(buf,i+2);
  #define DO8(buf,i)  DO4(buf,i); DO4(buf,i+4);
  #define DO16(buf)   DO8(buf,0); DO8(buf,8);
  
  /* ========================================================================= */
  uLong ZEXPORT adler32(adler, buf, len)
      uLong adler;
      const Bytef *buf;
      uInt len;
  {
      unsigned long s1 = adler & 0xffff;
      unsigned long s2 = (adler >> 16) & 0xffff;
      int k;
  
      if (buf == Z_NULL) return 1L;
  
      while (len > 0) {
          k = len < NMAX ? len : NMAX;
          len -= k;
          while (k >= 16) {
              DO16(buf);
  	    buf += 16;
              k -= 16;
          }
          if (k != 0) do {
              s1 += *buf++;
  	    s2 += s1;
          } while (--k);
          s1 %= BASE;
          s2 %= BASE;
      }
      return (s2 << 16) | s1;
  }
  