69 lines
1.7 KiB
C
69 lines
1.7 KiB
C
/*
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* GF-Complete: A Comprehensive Open Source Library for Galois Field Arithmetic
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* James S. Plank, Ethan L. Miller, Kevin M. Greenan,
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* Benjamin A. Arnold, John A. Burnum, Adam W. Disney, Allen C. McBride.
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*
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* gf_mult.c
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*
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* Multiplies two numbers in gf_2^w
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*/
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#include <stdio.h>
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#include <getopt.h>
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#include <stdint.h>
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#include <string.h>
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#include <stdlib.h>
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#include "gf_complete.h"
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#include "gf_method.h"
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#include "gf_general.h"
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void usage(int why)
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{
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fprintf(stderr, "usage: gf_mult a b w [method] - does multiplication of a and b in GF(2^w)\n");
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if (why == 'W') {
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fprintf(stderr, "Bad w.\n");
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fprintf(stderr, "Legal w are: 1 - 32, 64 and 128.\n");
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fprintf(stderr, "Append 'h' to w to treat a, b and the product as hexadecimal.\n");
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fprintf(stderr, "w=128 is hex only (i.e. '128' will be an error - do '128h')\n");
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}
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if (why == 'A') fprintf(stderr, "Bad a\n");
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if (why == 'B') fprintf(stderr, "Bad b\n");
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if (why == 'M') {
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fprintf(stderr, "Bad Method Specification: ");
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gf_error();
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}
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exit(1);
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}
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int main(int argc, char **argv)
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{
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int hex, w;
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gf_t gf;
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gf_general_t a, b, c;
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char output[50];
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if (argc < 4) usage(' ');
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if (sscanf(argv[3], "%d", &w) == 0) usage('W');
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if (w <= 0 || (w > 32 && w != 64 && w != 128)) usage('W');
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hex = (strchr(argv[3], 'h') != NULL);
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if (!hex && w == 128) usage('W');
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if (argc == 4) {
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if (gf_init_easy(&gf, w) == 0) usage('M');
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} else {
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if (create_gf_from_argv(&gf, w, argc, argv, 4) == 0) usage('M');
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}
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if (!gf_general_s_to_val(&a, w, argv[1], hex)) usage('A');
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if (!gf_general_s_to_val(&b, w, argv[2], hex)) usage('B');
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gf_general_multiply(&gf, &a, &b, &c);
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gf_general_val_to_s(&c, w, output, hex);
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printf("%s\n", output);
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exit(0);
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}
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