1  /* zutil.h -- internal interface and configuration of the compression library
2   * Copyright (C) 1995-1998 Jean-loup Gailly.
3   * For conditions of distribution and use, see copyright notice in zlib.h
4   */
5  
6  /* WARNING: this file should *not* be used by applications. It is
7     part of the implementation of the compression library and is
8     subject to change. Applications should only use zlib.h.
9   */
10  
11  /* @(#) $Id: zutil.h,v 1.1 2000/01/01 03:32:23 davem Exp $ */
12  
13  #ifndef _Z_UTIL_H
14  #define _Z_UTIL_H
15  
16  #include <linux/zlib.h>
17  #include <linux/string.h>
18  #include <linux/kernel.h>
19  
20  typedef unsigned char  uch;
21  typedef unsigned short ush;
22  typedef unsigned long  ulg;
23  
24          /* common constants */
25  
26  #define STORED_BLOCK 0
27  #define STATIC_TREES 1
28  #define DYN_TREES    2
29  /* The three kinds of block type */
30  
31  #define MIN_MATCH  3
32  #define MAX_MATCH  258
33  /* The minimum and maximum match lengths */
34  
35  #define PRESET_DICT 0x20 /* preset dictionary flag in zlib header */
36  
37          /* target dependencies */
38  
39          /* Common defaults */
40  
41  #ifndef OS_CODE
42  #  define OS_CODE  0x03  /* assume Unix */
43  #endif
44  
45           /* functions */
46  
47  typedef uLong (*check_func) (uLong check, const Byte *buf,
48  				       uInt len);
49  
50  
51                          /* checksum functions */
52  
53  #define BASE 65521L /* largest prime smaller than 65536 */
54  #define NMAX 5552
55  /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
56  
57  #define DO1(buf,i)  {s1 += buf[i]; s2 += s1;}
58  #define DO2(buf,i)  DO1(buf,i); DO1(buf,i+1);
59  #define DO4(buf,i)  DO2(buf,i); DO2(buf,i+2);
60  #define DO8(buf,i)  DO4(buf,i); DO4(buf,i+4);
61  #define DO16(buf)   DO8(buf,0); DO8(buf,8);
62  
63  /* ========================================================================= */
64  /*
65       Update a running Adler-32 checksum with the bytes buf[0..len-1] and
66     return the updated checksum. If buf is NULL, this function returns
67     the required initial value for the checksum.
68     An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
69     much faster. Usage example:
70  
71       uLong adler = zlib_adler32(0L, NULL, 0);
72  
73       while (read_buffer(buffer, length) != EOF) {
74         adler = zlib_adler32(adler, buffer, length);
75       }
76       if (adler != original_adler) error();
77  */
zlib_adler32(uLong adler,const Byte * buf,uInt len)78  static inline uLong zlib_adler32(uLong adler,
79  				 const Byte *buf,
80  				 uInt len)
81  {
82      unsigned long s1 = adler & 0xffff;
83      unsigned long s2 = (adler >> 16) & 0xffff;
84      int k;
85  
86      if (buf == NULL) return 1L;
87  
88      while (len > 0) {
89          k = len < NMAX ? len : NMAX;
90          len -= k;
91          while (k >= 16) {
92              DO16(buf);
93  	    buf += 16;
94              k -= 16;
95          }
96          if (k != 0) do {
97              s1 += *buf++;
98  	    s2 += s1;
99          } while (--k);
100          s1 %= BASE;
101          s2 %= BASE;
102      }
103      return (s2 << 16) | s1;
104  }
105  
106  #endif /* _Z_UTIL_H */
107