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adler32.c
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1 /* adler32.c -- compute the Adler-32 checksum of a data stream
2  * Copyright (C) 1995-2002 Mark Adler
3  * For conditions of distribution and use, see copyright notice in zlib.h
4  */
5 
6 /* @(#) $Id$ */
7 
8 #include "zlib.h"
9 
10 #define BASE 65521L /* largest prime smaller than 65536 */
11 #define NMAX 5552
12 /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
13 
14 #define DO1(buf,i) {s1 += buf[i]; s2 += s1;}
15 #define DO2(buf,i) DO1(buf,i); DO1(buf,i+1);
16 #define DO4(buf,i) DO2(buf,i); DO2(buf,i+2);
17 #define DO8(buf,i) DO4(buf,i); DO4(buf,i+4);
18 #define DO16(buf) DO8(buf,0); DO8(buf,8);
19 
20 /* ========================================================================= */
21 ZEXPORT(uLong) adler32( /* adler, buf, len) */
22  uLong adler,
23  const Bytef *buf,
24  uInt len )
25 {
26  unsigned long s1 = adler & 0xffff;
27  unsigned long s2 = (adler >> 16) & 0xffff;
28  int k;
29 
30  if (buf == Z_NULL) return 1L;
31 
32  while (len > 0) {
33  k = len < NMAX ? len : NMAX;
34  len -= k;
35  while (k >= 16) {
36  DO16(buf);
37  buf += 16;
38  k -= 16;
39  }
40  if (k != 0) do {
41  s1 += *buf++;
42  s2 += s1;
43  } while (--k);
44  s1 %= BASE;
45  s2 %= BASE;
46  }
47  return (s2 << 16) | s1;
48 }
struct S2 s2
GLenum GLuint GLenum GLsizei const GLchar * buf
Definition: glext.h:7751
#define DO16(buf)
Definition: adler32.c:18
Byte FAR Bytef
Definition: zconf.h:400
#define NMAX
Definition: adler32.c:11
unsigned long uLong
Definition: zconf.h:394
struct S1 s1
#define BASE
Definition: adler32.c:10
ZEXPORT(uLong)
Definition: adler32.c:21
static const WCHAR L[]
Definition: oid.c:1250
GLenum GLsizei len
Definition: glext.h:6722
#define Z_NULL
Definition: zlib.h:212
uLong ZEXPORT adler32(uLong adler, const Bytef *buf, uInt len)
Definition: adler32.c:134
int k
Definition: mpi.c:3369
unsigned int uInt
Definition: zconf.h:393