linux/include/linux/zutil.h
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   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
  20typedef unsigned char  uch;
  21typedef unsigned short ush;
  22typedef 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
  47typedef 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*/
  78static 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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