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 */
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
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