libcruft-util/bsdsum.cpp

36 lines
1.0 KiB
C++

/*
* This file is part of libgim.
*
* 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.
*
* 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@nerdcruft.net>
*/
#include "bsdsum.hpp"
uint16_t
bsdsum (const void *restrict _data, size_t size) {
const uint8_t *restrict data = static_cast<const uint8_t*> (_data);
uint16_t accum = 0;
for (size_t i = 0; i < size; ++i) {
accum = (accum >> 1) | ((accum & 0x1) << 15);
accum += data[i];
}
return accum;
}