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/*
* Adler-32 checksum
*
* Copyright (c) 2003-2019 Joergen Ibsen
*
* 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 "tinf.h"
#define A32_BASE 65521
#define A32_NMAX 5552
unsigned int tinf_adler32(const void *data, unsigned int length)
{
const unsigned char *buf = (const unsigned char *) data;
unsigned int s1 = 1;
unsigned int s2 = 0;
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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