mirror of
https://github.com/kevinbentley/Descent3.git
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90 lines
3.2 KiB
C
90 lines
3.2 KiB
C
/*
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* Descent 3
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* Copyright (C) 2024 Parallax Software
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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/*
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* $Logfile: $
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* $Revision: $
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* $Date: $
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* $Author: $
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*
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* <insert description of file here>
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*
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* $Log: $
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*
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* $NoKeywords: $
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*/
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/* adler32.c -- compute the Adler-32 checksum of a data stream
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* Copyright (C) 1995-1998 Mark Adler
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* For conditions of distribution and use, see copyright notice in zlib.h
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*/
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/* @(#) $Id$ */
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#include "zlib.h"
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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) \
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{ \
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s1 += buf[i]; \
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s2 += s1; \
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}
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#define DO2(buf, i) \
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DO1(buf, i); \
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DO1(buf, i + 1);
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#define DO4(buf, i) \
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DO2(buf, i); \
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DO2(buf, i + 2);
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#define DO8(buf, i) \
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DO4(buf, i); \
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DO4(buf, i + 4);
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#define DO16(buf) \
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DO8(buf, 0); \
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DO8(buf, 8);
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/* ========================================================================= */
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uLong ZEXPORT adler32(uLong adler, const Bytef *buf, uInt len) {
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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 == Z_NULL)
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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)
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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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