Function gf128_genmultable

freebsd/opencrypto/gfmult.c:61–81

* Generate a table for 0-16 * h. Store the results in the table w/ indexes * bit reversed, and the words striped across the values. */

 * bit reversed, and the words striped across the values.
 */
void
gf128_genmultable(struct gf128 h, struct gf128table *t)
{
	struct gf128 tbl[16];
	int i;

	tbl[0] = MAKE_GF128(0, 0);
	tbl[1] = h;

	for (i = 2; i < 16; i += 2) {
		tbl[i] = gf128_mulalpha(tbl[i / 2]);
		tbl[i + 1] = gf128_add(tbl[i], h);
	}

	for (i = 0; i < 16; i++) {
		t->a[nib_rev[i]] = tbl[i].v[0] >> 32;
		t->b[nib_rev[i]] = tbl[i].v[0];
		t->c[nib_rev[i]] = tbl[i].v[1] >> 32;
		t->d[nib_rev[i]] = tbl[i].v[1];
	}
}

/*
 * Generate tables containing h, h^2, h^3 and h^4, starting at 0.