badvpn/misc/modadd.h

/**
 * @file modadd.h
 * @author Ambroz Bizjak <ambrop7@gmail.com>
 * 
 * @section LICENSE
 * 
 * This file is part of BadVPN.
 * 
 * BadVPN is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation.
 * 
 * BadVPN 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, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 * 
 * @section DESCRIPTION
 * 
 * Modular addition macro.
 * 
 * Calculates (x + y) mod m, assuming
 * 0 <= x < m and 0 <= y < m.
 */

#ifndef BADVPN_MISC_MODADD_H
#define BADVPN_MISC_MODADD_H

#include <misc/debug.h>

#define DECLARE_BMODADD(type, name) \
static type bmodadd_##name (type x, type y, type m) \
{ \
    ASSERT(x >= 0) \
    ASSERT(x < m) \
    ASSERT(y >= 0) \
    ASSERT(y < m) \
     \
    if (y >= m - x) { \
        return (y - (m - x)); \
    } else { \
        return (x + y); \
    } \
} \

DECLARE_BMODADD(int, int)

#endif