include/linux/zutil.h

   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 #ifndef DEF_WBITS
  27 #  define DEF_WBITS MAX_WBITS
  28 #endif
  29 /* default windowBits for decompression. MAX_WBITS is for compression only */
  30
  31 #if MAX_MEM_LEVEL >= 8
  32 #  define DEF_MEM_LEVEL 8
  33 #else
  34 #  define DEF_MEM_LEVEL  MAX_MEM_LEVEL
  35 #endif
  36 /* default memLevel */
  37
  38 #define STORED_BLOCK 0
  39 #define STATIC_TREES 1
  40 #define DYN_TREES    2
  41 /* The three kinds of block type */
  42
  43 #define MIN_MATCH  3
  44 #define MAX_MATCH  258
  45 /* The minimum and maximum match lengths */
  46
  47 #define PRESET_DICT 0x20 /* preset dictionary flag in zlib header */
  48
  49         /* target dependencies */
  50
  51         /* Common defaults */
  52
  53 #ifndef OS_CODE
  54 #  define OS_CODE  0x03  /* assume Unix */
  55 #endif
  56
  57          /* functions */
  58
  59 typedef uLong (*check_func) (uLong check, const Byte *buf,
  60                                        uInt len);
  61
  62
  63                         /* checksum functions */
  64
  65 #define BASE 65521L /* largest prime smaller than 65536 */
  66 #define NMAX 5552
  67 /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
  68
  69 #define DO1(buf,i)  {s1 += buf[i]; s2 += s1;}
  70 #define DO2(buf,i)  DO1(buf,i); DO1(buf,i+1);
  71 #define DO4(buf,i)  DO2(buf,i); DO2(buf,i+2);
  72 #define DO8(buf,i)  DO4(buf,i); DO4(buf,i+4);
  73 #define DO16(buf)   DO8(buf,0); DO8(buf,8);
  74
  75 /* ========================================================================= */
  76 /*
  77      Update a running Adler-32 checksum with the bytes buf[0..len-1] and
  78    return the updated checksum. If buf is NULL, this function returns
  79    the required initial value for the checksum.
  80    An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
  81    much faster. Usage example:
  82
  83      uLong adler = adler32(0L, NULL, 0);
  84
  85      while (read_buffer(buffer, length) != EOF) {
  86        adler = adler32(adler, buffer, length);
  87      }
  88      if (adler != original_adler) error();
  89 */
  90 static inline uLong zlib_adler32(uLong adler,
  91                                  const Byte *buf,
  92                                  uInt len)
  93 {
  94     unsigned long s1 = adler & 0xffff;
  95     unsigned long s2 = (adler >> 16) & 0xffff;
  96     int k;
  97
  98     if (buf == NULL) return 1L;
  99
 100     while (len > 0) {
 101         k = len < NMAX ? len : NMAX;
 102         len -= k;
 103         while (k >= 16) {
 104             DO16(buf);
 105             buf += 16;
 106             k -= 16;
 107         }
 108         if (k != 0) do {
 109             s1 += *buf++;
 110             s2 += s1;
 111         } while (--k);
 112         s1 %= BASE;
 113         s2 %= BASE;
 114     }
 115     return (s2 << 16) | s1;
 116 }
 117
 118 #endif /* _Z_UTIL_H */