libcruft-util/fletcher.hpp

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/*
* This file is part of libgim.
*
2012-04-11 15:18:26 +10:00
* libgim 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 3 of the License, or (at your option) any later
* version.
*
2012-04-11 15:18:26 +10:00
* libgim is distributed in the hope that it will be useful, but WITHOUT ANY
* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License
* along with libgim. If not, see <http://www.gnu.org/licenses/>.
*
* Copyright 2010 Danny Robson <danny@blubinc.net>
*/
#ifndef __UTIL_FLETCHER_HPP
#define __UTIL_FLETCHER_HPP
#include "types.hpp"
#include <cstdint>
#include <cstdlib>
template <unsigned BITS, unsigned MODULUS, unsigned INITIAL_A, unsigned INITIAL_B>
typename bits_type<BITS>::uint
fletcher (const void *restrict _data, size_t size) {
const uint8_t *restrict data = static_cast<const uint8_t*> (_data);
typename bits_type<BITS>::uint A = INITIAL_A,
B = INITIAL_B;
for (size_t i = 0; i < size; ++i) {
A = (A + data[i]) % MODULUS;
B = (A + B) % MODULUS;
}
return (B << (BITS / 2)) | A;
}
#endif