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107 lines
2.7 KiB
C
107 lines
2.7 KiB
C
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/* zutil.h -- internal interface and configuration of the compression library
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* Copyright (C) 1995-1998 Jean-loup Gailly.
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* For conditions of distribution and use, see copyright notice in zlib.h
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*/
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/* WARNING: this file should *not* be used by applications. It is
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part of the implementation of the compression library and is
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subject to change. Applications should only use zlib.h.
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*/
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/* @(#) $Id: zutil.h,v 1.1 2000/01/01 03:32:23 davem Exp $ */
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#ifndef _Z_UTIL_H
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#define _Z_UTIL_H
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#include <linux/zlib.h>
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#include <linux/string.h>
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#include <linux/kernel.h>
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typedef unsigned char uch;
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typedef unsigned short ush;
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typedef unsigned long ulg;
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/* common constants */
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#define STORED_BLOCK 0
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#define STATIC_TREES 1
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#define DYN_TREES 2
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/* The three kinds of block type */
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#define MIN_MATCH 3
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#define MAX_MATCH 258
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/* The minimum and maximum match lengths */
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#define PRESET_DICT 0x20 /* preset dictionary flag in zlib header */
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/* target dependencies */
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/* Common defaults */
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#ifndef OS_CODE
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# define OS_CODE 0x03 /* assume Unix */
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#endif
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/* functions */
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typedef uLong (*check_func) (uLong check, const Byte *buf,
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uInt len);
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/* checksum functions */
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#define BASE 65521L /* largest prime smaller than 65536 */
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#define NMAX 5552
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/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
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#define DO1(buf,i) {s1 += buf[i]; s2 += s1;}
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#define DO2(buf,i) DO1(buf,i); DO1(buf,i+1);
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#define DO4(buf,i) DO2(buf,i); DO2(buf,i+2);
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#define DO8(buf,i) DO4(buf,i); DO4(buf,i+4);
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#define DO16(buf) DO8(buf,0); DO8(buf,8);
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/* ========================================================================= */
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/*
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Update a running Adler-32 checksum with the bytes buf[0..len-1] and
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return the updated checksum. If buf is NULL, this function returns
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the required initial value for the checksum.
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An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
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much faster. Usage example:
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uLong adler = adler32(0L, NULL, 0);
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while (read_buffer(buffer, length) != EOF) {
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adler = adler32(adler, buffer, length);
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}
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if (adler != original_adler) error();
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*/
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static inline uLong zlib_adler32(uLong adler,
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const Byte *buf,
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uInt len)
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{
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unsigned long s1 = adler & 0xffff;
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unsigned long s2 = (adler >> 16) & 0xffff;
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int k;
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if (buf == NULL) return 1L;
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while (len > 0) {
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k = len < NMAX ? len : NMAX;
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len -= k;
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while (k >= 16) {
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DO16(buf);
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buf += 16;
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k -= 16;
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}
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if (k != 0) do {
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s1 += *buf++;
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s2 += s1;
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} while (--k);
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s1 %= BASE;
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s2 %= BASE;
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}
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return (s2 << 16) | s1;
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}
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#endif /* _Z_UTIL_H */
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