Current File : //usr/src/linux-headers-5.15.0-125-generic/include/linux/zutil.h
/* zutil.h -- internal interface and configuration of the compression library
* Copyright (C) 1995-1998 Jean-loup Gailly.
* For conditions of distribution and use, see copyright notice in zlib.h
*/
/* WARNING: this file should *not* be used by applications. It is
part of the implementation of the compression library and is
subject to change. Applications should only use zlib.h.
*/
/* @(#) $Id: zutil.h,v 1.1 2000/01/01 03:32:23 davem Exp $ */
#ifndef _Z_UTIL_H
#define _Z_UTIL_H
#include <linux/zlib.h>
#include <linux/string.h>
#include <linux/kernel.h>
typedef unsigned char uch;
typedef unsigned short ush;
typedef unsigned long ulg;
/* common constants */
#define STORED_BLOCK 0
#define STATIC_TREES 1
#define DYN_TREES 2
/* The three kinds of block type */
#define MIN_MATCH 3
#define MAX_MATCH 258
/* The minimum and maximum match lengths */
#define PRESET_DICT 0x20 /* preset dictionary flag in zlib header */
/* target dependencies */
/* Common defaults */
#ifndef OS_CODE
# define OS_CODE 0x03 /* assume Unix */
#endif
/* functions */
typedef uLong (*check_func) (uLong check, const Byte *buf,
uInt len);
/* checksum functions */
#define BASE 65521L /* largest prime smaller than 65536 */
#define NMAX 5552
/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
#define DO1(buf,i) {s1 += buf[i]; s2 += s1;}
#define DO2(buf,i) DO1(buf,i); DO1(buf,i+1);
#define DO4(buf,i) DO2(buf,i); DO2(buf,i+2);
#define DO8(buf,i) DO4(buf,i); DO4(buf,i+4);
#define DO16(buf) DO8(buf,0); DO8(buf,8);
/* ========================================================================= */
/*
Update a running Adler-32 checksum with the bytes buf[0..len-1] and
return the updated checksum. If buf is NULL, this function returns
the required initial value for the checksum.
An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
much faster. Usage example:
uLong adler = zlib_adler32(0L, NULL, 0);
while (read_buffer(buffer, length) != EOF) {
adler = zlib_adler32(adler, buffer, length);
}
if (adler != original_adler) error();
*/
static inline uLong zlib_adler32(uLong adler,
const Byte *buf,
uInt len)
{
unsigned long s1 = adler & 0xffff;
unsigned long s2 = (adler >> 16) & 0xffff;
int k;
if (buf == NULL) return 1L;
while (len > 0) {
k = len < NMAX ? len : NMAX;
len -= k;
while (k >= 16) {
DO16(buf);
buf += 16;
k -= 16;
}
if (k != 0) do {
s1 += *buf++;
s2 += s1;
} while (--k);
s1 %= BASE;
s2 %= BASE;
}
return (s2 << 16) | s1;
}
#endif /* _Z_UTIL_H */
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