/* See LICENSE file for copyright and license details. */
#include "internals.h"

#define tb  libzahl_tmp_pow_b
#define td  libzahl_tmp_pow_d


void
zmodpowu(z_t a, z_t b, unsigned long long int c, z_t d)
{
	if (unlikely(!c)) {
		if (zzero(b))
			libzahl_failure(-ZERROR_0_POW_0);
		else if (zzero(d))
			libzahl_failure(-ZERROR_DIV_0);
		else
			zsetu(a, 1);
		return;
	} else if (unlikely(zzero(d))) {
		libzahl_failure(-ZERROR_DIV_0);
	} else if (unlikely(zzero(b))) {
		SET_SIGNUM(a, 0);
		return;
	}

	zmod(tb, b, d);
	zset(td, d);
	zsetu(a, 1);

	for (; c; c >>= 1) {
		if (c & 1)
			zmodmul(a, a, tb, td);
		zmodsqr(tb, tb, td);
	}
}