Watt-32 tcp/ip  2.2 dev-rel.10
zadler32.c
1 /* adler32.c -- compute the Adler-32 checksum of a data stream
2  * Copyright (C) 1995-2003 Mark Adler
3  * For conditions of distribution and use, see copyright notice in zlib.h
4  */
5 
6 /* @(#) $Id$ */
7 
8 #define ZLIB_INTERNAL
9 #include "wattcp.h"
10 #include "zlib.h"
11 
12 #if defined(USE_GZIP)
13 
14 #define BASE 65521UL /* largest prime smaller than 65536 */
15 #define NMAX 5552
16 /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
17 
18 #define DO1(buf,i) {s1 += buf[i]; s2 += s1;}
19 #define DO2(buf,i) DO1(buf,i); DO1(buf,i+1);
20 #define DO4(buf,i) DO2(buf,i); DO2(buf,i+2);
21 #define DO8(buf,i) DO4(buf,i); DO4(buf,i+4);
22 #define DO16(buf) DO8(buf,0); DO8(buf,8);
23 
24 #ifdef NO_DIVIDE
25 # define MOD(a) \
26  do { \
27  if (a >= (BASE << 16)) a -= (BASE << 16); \
28  if (a >= (BASE << 15)) a -= (BASE << 15); \
29  if (a >= (BASE << 14)) a -= (BASE << 14); \
30  if (a >= (BASE << 13)) a -= (BASE << 13); \
31  if (a >= (BASE << 12)) a -= (BASE << 12); \
32  if (a >= (BASE << 11)) a -= (BASE << 11); \
33  if (a >= (BASE << 10)) a -= (BASE << 10); \
34  if (a >= (BASE << 9)) a -= (BASE << 9); \
35  if (a >= (BASE << 8)) a -= (BASE << 8); \
36  if (a >= (BASE << 7)) a -= (BASE << 7); \
37  if (a >= (BASE << 6)) a -= (BASE << 6); \
38  if (a >= (BASE << 5)) a -= (BASE << 5); \
39  if (a >= (BASE << 4)) a -= (BASE << 4); \
40  if (a >= (BASE << 3)) a -= (BASE << 3); \
41  if (a >= (BASE << 2)) a -= (BASE << 2); \
42  if (a >= (BASE << 1)) a -= (BASE << 1); \
43  if (a >= BASE) a -= BASE; \
44  } while (0)
45 #else
46 # define MOD(a) a %= BASE
47 #endif
48 
49 /* ========================================================================= */
50 uLong ZEXPORT adler32(adler, buf, len)
51  uLong adler;
52  const Bytef *buf;
53  uInt len;
54 {
55  unsigned long s1 = adler & 0xffff;
56  unsigned long s2 = (adler >> 16) & 0xffff;
57 
58  if (buf == Z_NULL) return 1L;
59 
60  while (len > 0) {
61  int k = len < NMAX ? (int)len : NMAX;
62  len -= k;
63  while (k >= 16) {
64  DO16(buf);
65  buf += 16;
66  k -= 16;
67  }
68  if (k != 0) do {
69  s1 += *buf++;
70  s2 += s1;
71  } while (--k);
72  MOD(s1);
73  MOD(s2);
74  }
75  return (s2 << 16) | s1;
76 }
77 #endif /* USE_GZIP */
78 
Core definitions.