#include "sec_osal_light.h"
#include "sec_cust_struct.h"
#include "bgn_internal.h"

#define MOD "BGN"

/**************************************************************************
 *  FUNCTIONS
 **************************************************************************/
void montg_init(ulong *mm, const bgn *P_N)
{
	ulong x, m0 = P_N->p[0];

	x = m0;
	x += ((m0 + 2) & 4) << 1;
	x *= (2 - (m0 * x));

	if (biL >= 16)
		x *= (2 - (m0 * x));

	if (biL >= 32)
		x *= (2 - (m0 * x));

	if (biL >= 64)
		x *= (2 - (m0 * x));

	*mm = ~x + 1;
}

void montg_mul(bgn *P_A, const bgn *P_B, const bgn *P_N, ulong mm, const bgn *P_T)
{
	int i, n, m;
	ulong u0, u1, *d;

	memset(P_T->p, 0, P_T->n * ciL);

	d = P_T->p;
	n = P_N->n;
	m = (P_B->n < n) ? P_B->n : n;

	for (i = 0; i < n; i++) {
		u0 = P_A->p[i];
		u1 = (d[0] + u0 * P_B->p[0]) * mm;

		bgn_mul_hlp(m, P_B->p, d, u0);
		bgn_mul_hlp(n, P_N->p, d, u1);

		*d++ = u0;
		d[n + 1] = 0;
	}

	memcpy(P_A->p, d, (n + 1) * ciL);

	if (bgn_cmp_abs(P_A, P_N) >= 0)
		bgn_sub_hlp(n, P_N->p, P_A->p);
	else
		bgn_sub_hlp(n, P_A->p, P_T->p);
}

void montg_red(bgn *P_A, const bgn *P_N, ulong mm, const bgn *P_T)
{
	ulong z = 1;
	bgn U;

	U.n = U.s = z;
	U.p = &z;

	montg_mul(P_A, &U, P_N, mm, P_T);
}