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 #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 = adler32(0L, NULL, 0);
  72
  73      while (read_buffer(buffer, length) != EOF) {
  74        adler = 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 */