/* gf_inverse.c
* James S. Plank
Galois.tar - Fast Galois Field Arithmetic Library in C/C++
Copright (C) 2007 James S. Plank
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
James S. Plank
Department of Computer Science
University of Tennessee
Knoxville, TN 37996
plank@cs.utk.edu
*/
#include
#include "galois.h"
main(int argc, char **argv)
{
unsigned int x, w;
if (argc != 3) {
fprintf(stderr, "usage: gf_inverse x w - returns 1/x in GF(2^w).\n");
exit(1);
}
if (sscanf(argv[1], "%u", &x) != 1) {
fprintf(stderr, "usage: gf_inverse x w - returns 1/x in GF(2^w).\n");
exit(1);
}
if (sscanf(argv[2], "%u", &w) != 1) {
fprintf(stderr, "usage: gf_inverse x w - returns 1/x in GF(2^w).\n");
exit(1);
}
if (w < 1 || w > 32) { fprintf(stderr, "Bad w\n"); exit(1); }
if (w < 32 && x >= (1 << w)) { fprintf(stderr, "x must be in [0,%d]\n", (1 << w)-1); exit(1); }
printf("%u\n", galois_inverse(x, w));
exit(0);
}