84 lines
2.4 KiB
C
84 lines
2.4 KiB
C
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/**
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* \file
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* <!--
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* This file is part of BeRTOS.
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*
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* Bertos 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 2 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, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*
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* As a special exception, you may use this file as part of a free software
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* library without restriction. Specifically, if other files instantiate
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* templates or use macros or inline functions from this file, or you compile
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* this file and link it with other files to produce an executable, this
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* file does not by itself cause the resulting executable to be covered by
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* the GNU General Public License. This exception does not however
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* invalidate any other reasons why the executable file might be covered by
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* the GNU General Public License.
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*
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* Copyright 2007 Develer S.r.l. (http://www.develer.com/)
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* All Rights Reserved.
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* -->
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*
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* \brief Rotating Hash algorithm.
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*
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* This is a simple yet powerfull checksum algorithm.
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* Instead of just xor-ing the data, rotating hash
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* circular shift the checksum 4 place left before xoring.
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* This is a bit more stronger than simply sum the data.
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*
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*
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* \author Francesco Sacchi <batt@develer.com>
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*
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* $WIZ$ module_name = "rotating_hash"
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*/
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#ifndef ALGO_ROTATING_H
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#define ALGO_ROTATING_H
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#include <cfg/compiler.h>
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typedef uint16_t rotating_t;
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/**
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* Init rotating checksum.
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*/
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INLINE void rotating_init(rotating_t *rot)
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{
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*rot = 0;
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}
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/**
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* Update checksum pointed by \c rot with \c c data.
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*/
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INLINE void rotating_update1(uint8_t c, rotating_t *rot)
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{
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*rot = (*rot << 4) ^ (*rot >> 12) ^ c;
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}
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/**
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* Update checksum pointed by \c rot with data supplied in \c buf.
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*/
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INLINE void rotating_update(const void *_buf, size_t len, rotating_t *rot)
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{
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const uint8_t *buf = (const uint8_t *)_buf;
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while (len--)
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rotating_update1(*buf++, rot);
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}
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#endif // ALGO_ROTATING_H
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