752d7d239a
Compiler output is identical before & after this step git-svn-id: https://svn.code.sf.net/p/nsis/code/NSIS/branches/wizou@6036 212acab6-be3b-0410-9dea-997c60f758d6
94 lines
3.2 KiB
C++
94 lines
3.2 KiB
C++
/* adler32.c -- compute the Adler-32 checksum of a data stream
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* Copyright (C) 1995-2003 Mark Adler
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THIS IS A MODIFIED VERSION OF THE ORIGINAL ZLIB adler32.c!
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The following was copied from zlib.h:
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be
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misrepresented as being the original software.
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3. This notice may not be removed or altered from any source distribution.
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Reviewed for Unicode support by Jim Park -- 08/29/2007
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(nothing changed.)
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*/
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#include "adler32.h"
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#define Z_NULL 0 /* for initializing zalloc, zfree, opaque */
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#define BASE 65521UL /* 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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#ifdef NO_DIVIDE
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# define MOD(a) \
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do { \
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if (a >= (BASE << 16)) a -= (BASE << 16); \
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if (a >= (BASE << 15)) a -= (BASE << 15); \
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if (a >= (BASE << 14)) a -= (BASE << 14); \
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if (a >= (BASE << 13)) a -= (BASE << 13); \
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if (a >= (BASE << 12)) a -= (BASE << 12); \
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if (a >= (BASE << 11)) a -= (BASE << 11); \
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if (a >= (BASE << 10)) a -= (BASE << 10); \
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if (a >= (BASE << 9)) a -= (BASE << 9); \
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if (a >= (BASE << 8)) a -= (BASE << 8); \
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if (a >= (BASE << 7)) a -= (BASE << 7); \
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if (a >= (BASE << 6)) a -= (BASE << 6); \
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if (a >= (BASE << 5)) a -= (BASE << 5); \
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if (a >= (BASE << 4)) a -= (BASE << 4); \
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if (a >= (BASE << 3)) a -= (BASE << 3); \
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if (a >= (BASE << 2)) a -= (BASE << 2); \
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if (a >= (BASE << 1)) a -= (BASE << 1); \
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if (a >= BASE) a -= BASE; \
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} while (0)
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#else
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# define MOD(a) a %= BASE
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#endif
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namespace Checksum {
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/* ========================================================================= */
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uLong adler32(uLong adler, const Byte *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) return 1L;
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while (len > 0) {
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k = len < NMAX ? (int)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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MOD(s1);
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MOD(s2);
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}
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return (s2 << 16) | s1;
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}
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}
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