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 | |