xref: /openbmc/linux/include/linux/zutil.h (revision cb7ae262)
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