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/*
* Adler-32 checksum
*
* Copyright (c) 2003 by Joergen Ibsen / Jibz
* All Rights Reserved
*
* http://www.ibsensoftware.com/
*
* This software is provided 'as-is', without any express
* or implied warranty. In no event will the authors be
* held liable for any damages arising from the use of
* this software.
*
* Permission is granted to anyone to use this software
* for any purpose, including commercial applications,
* and to alter it and redistribute it freely, subject to
* the following restrictions:
*
* 1. The origin of this software must not be
* misrepresented; you must not claim that you
* wrote the original software. If you use this
* software in a product, an acknowledgment in
* the product documentation would be appreciated
* but is not required.
*
* 2. Altered source versions must be plainly marked
* as such, and must not be misrepresented as
* being the original software.
*
* 3. This notice may not be removed or altered from
* any source distribution.
*/
/*
* Adler-32 algorithm taken from the zlib source, which is
* Copyright (C) 1995-1998 Jean-loup Gailly and Mark Adler
*/
#include "uzlib.h"
#define A32_BASE 65521
#define A32_NMAX 5552
uint32_t uzlib_adler32(const void *data, unsigned int length, uint32_t prev_sum /* 1 */)
{
const unsigned char *buf = (const unsigned char *)data;
unsigned int s1 = prev_sum & 0xffff;
unsigned int s2 = prev_sum >> 16;
while (length > 0)
{
int k = length < A32_NMAX ? length : A32_NMAX;
int i;
for (i = k / 16; i; --i, buf += 16)
{
s1 += buf[0]; s2 += s1; s1 += buf[1]; s2 += s1;
s1 += buf[2]; s2 += s1; s1 += buf[3]; s2 += s1;
s1 += buf[4]; s2 += s1; s1 += buf[5]; s2 += s1;
s1 += buf[6]; s2 += s1; s1 += buf[7]; s2 += s1;
s1 += buf[8]; s2 += s1; s1 += buf[9]; s2 += s1;
s1 += buf[10]; s2 += s1; s1 += buf[11]; s2 += s1;
s1 += buf[12]; s2 += s1; s1 += buf[13]; s2 += s1;
s1 += buf[14]; s2 += s1; s1 += buf[15]; s2 += s1;
}
for (i = k % 16; i; --i) { s1 += *buf++; s2 += s1; }
s1 %= A32_BASE;
s2 %= A32_BASE;
length -= k;
}
return (s2 << 16) | s1;
}
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