/**
 * srexpmod.c
 *   An implementation of the expmod function for SamR's simple math library.
 *
 *   Copyright (c) 2022 Samuel A. Rebelsky.  All rights reserved.
 *
 *   This file is part of SRMath, SamR's simple math library.
 *
 *   SRMath 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.
 *
 *   SRMath 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 SRMath.  If not, see <http://www.gnu.org/licenses/>.
 */


// +---------+---------------------------------------------------------
// | Headers |
// +---------+

#include <stdlib.h>

#include "srmath.h"
#include "srtest.h"


// +--------------------+----------------------------------------------
// | Exported Functions |
// +--------------------+

long
expmod (long x, long n, long m)
{
  if (0 == n)
    {
      return 1;
    } 
  else if (1 == (n % 2))
    {
      return (x * expmod (x, n-1, m)) % m;
    }
  else
    {
      return expmod (x*x % m, n/2, m);
    }
} // expmod