rockbox/firmware/common/adler32.c

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/***************************************************************************
* __________ __ ___.
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
* \/ \/ \/ \/ \/
* $Id$
*
* Copyright (C) 2021 James Buren (adaptations from tinf/zlib)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
****************************************************************************/
/* 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.
*/
#include "adler32.h"
#include "system.h"
/* adler_32 (derived from tinf adler32 which was taken from zlib)
* Adler-32 algorithm taken from the zlib source, which is
* Copyright (C) 1995-1998 Jean-loup Gailly and Mark Adler
*/
uint32_t adler_32(const void *src, uint32_t len, uint32_t adler32)
{
const unsigned char *buf = (const unsigned char *)src;
uint32_t s1 = (adler32 & 0xffff);
uint32_t s2 = (adler32 >> 16);
enum {
A32_BASE = 65521,
A32_NMAX = 5552,
};
while (len > 0) {
uint32_t k = MIN(len, A32_NMAX);
uint32_t i;
for (i = k / 16; i; --i, buf += 16) {
s2 += s1 += buf[0];
s2 += s1 += buf[1];
s2 += s1 += buf[2];
s2 += s1 += buf[3];
s2 += s1 += buf[4];
s2 += s1 += buf[5];
s2 += s1 += buf[6];
s2 += s1 += buf[7];
s2 += s1 += buf[8];
s2 += s1 += buf[9];
s2 += s1 += buf[10];
s2 += s1 += buf[11];
s2 += s1 += buf[12];
s2 += s1 += buf[13];
s2 += s1 += buf[14];
s2 += s1 += buf[15];
}
for (i = k % 16; i; --i) {
s1 += *buf++;
s2 += s1;
}
s1 %= A32_BASE;
s2 %= A32_BASE;
len -= k;
}
return (s1 | (s2 << 16));
}