TCPIPchecksum.cc

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//
// Copyright (C) 2005 Christian Dankbar, Irene Ruengeler, Michael Tuexen, Andras Varga
//               2009 Zoltan Bojthe
//
// 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 program 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 this program; if not, see <http://www.gnu.org/licenses/>.
//

#include "TCPIPchecksum.h"

#if !defined(_WIN32) && !defined(__WIN32__) && !defined(WIN32) && !defined(__CYGWIN__) && !defined(_WIN64)
#include <netinet/in.h>  // htonl, ntohl, ...
#endif

uint16_t TCPIPchecksum::_checksum(const void *addr, unsigned int count)
{
    uint32_t sum = 0;

    while (count > 1)
    {
        sum += *((const uint16_t *&)addr)++;
        if (sum & 0x80000000)
            sum = (sum & 0xFFFF) + (sum >> 16);
        count -= 2;
    }

    if (count)
        sum += *(const uint8_t *)addr;

    while (sum >> 16)
        sum = (sum & 0xFFFF) + (sum >> 16);

    return (uint16_t)sum;
}