`123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114` ``````/* * GF-Complete: A Comprehensive Open Source Library for Galois Field Arithmetic * James S. Plank, Ethan L. Miller, Kevin M. Greenan, * Benjamin A. Arnold, John A. Burnum, Adam W. Disney, Allen C. McBride. * * gf_add.c * * Adds two numbers in gf_2^w */ #include #include #include #include #include void usage(char *s) { fprintf(stderr, "usage: gf_add a b w - does addition of a and b in GF(2^w)\n"); fprintf(stderr, " If w has an h on the end, treat a, b and the sum as hexadecimal (no 0x required)\n"); fprintf(stderr, "\n"); fprintf(stderr, " legal w are: 1-32, 64 and 128\n"); fprintf(stderr, " 128 is hex only (i.e. '128' will be an error - do '128h')\n"); if (s != NULL) fprintf(stderr, "%s", s); exit(1); } int read_128(char *s, uint64_t *v) { int l, t; char save; l = strlen(s); if (l > 32) return 0; if (l > 16) { if (sscanf(s + (l-16), "%llx", (long long unsigned int *) &(v[1])) == 0) return 0; save = s[l-16]; s[l-16] = '\0'; t = sscanf(s, "%llx", (long long unsigned int *) &(v[0])); s[l-16] = save; return t; } else { v[0] = 0; return sscanf(s, "%llx", (long long unsigned int *)&(v[1])); } return 1; } void print_128(uint64_t *v) { if (v[0] > 0) { printf("%llx", (long long unsigned int) v[0]); printf("%016llx", (long long unsigned int) v[1]); } else { printf("%llx", (long long unsigned int) v[1]); } printf("\n"); } int main(int argc, char **argv) { int hex, w; uint32_t a, b, c, top; uint64_t a64, b64, c64; uint64_t a128[2], b128[2], c128[2]; char *format; if (argc != 4) usage(NULL); if (sscanf(argv[3], "%d", &w) == 0) usage("Bad w\n"); if (w <= 0 || (w > 32 && w != 64 && w != 128)) usage("Bad w"); hex = (strchr(argv[3], 'h') != NULL); if (!hex && w == 128) usage(NULL); if (w <= 32) { format = (hex) ? "%x" : "%u"; if (sscanf(argv[1], format, &a) == 0) usage("Bad a\n"); if (sscanf(argv[2], format, &b) == 0) usage("Bad b\n"); if (w < 32) { top = (w == 31) ? 0x80000000 : (1 << w); if (w != 32 && a >= top) usage("a is too large\n"); if (w != 32 && b >= top) usage("b is too large\n"); } c = a ^ b; printf(format, c); printf("\n"); } else if (w == 64) { format = (hex) ? "%llx" : "%llu"; if (sscanf(argv[1], format, &a64) == 0) usage("Bad a\n"); if (sscanf(argv[2], format, &b64) == 0) usage("Bad b\n"); c64 = a64 ^ b64; printf(format, c64); printf("\n"); } else if (w == 128) { if (read_128(argv[1], a128) == 0) usage("Bad a\n"); if (read_128(argv[2], b128) == 0) usage("Bad b\n"); c128[0] = a128[0] ^ b128[0]; c128[1] = a128[1] ^ b128[1]; print_128(c128); } exit(0); } ``````