/*=============================================================================

    This file is part of FLINT.

    FLINT is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    FLINT is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with FLINT; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA

=============================================================================*/
/******************************************************************************

    Copyright (C) 2009 William Hart
    Copyright (C) 2012 Fredrik Johansson

******************************************************************************/

#include <gmp.h>
#include "flint.h"
#include "ulong_extras.h"
#include "fmpz.h"

void
fmpz_mul_tdiv_q_2exp(fmpz_t f, const fmpz_t g, const fmpz_t h, ulong exp)
{
    fmpz c1, c2;
    __mpz_struct *mpz_ptr;

    c1 = *g;

    if (!COEFF_IS_MPZ(c1))      /* g is small */
    {
        fmpz_mul_si_tdiv_q_2exp(f, h, c1, exp);
        return;
    }

    c2 = *h;                    /* save h in case it is aliased with f */

    if (c2 == WORD(0))               /* special case, h = 0  */
    {
        fmpz_zero(f);
        return;
    }

    mpz_ptr = _fmpz_promote(f); /* h is saved, g is already large */

    if (!COEFF_IS_MPZ(c2))      /* g is large, h is small */
        flint_mpz_mul_si(mpz_ptr, COEFF_TO_PTR(c1), c2);
    else                        /* c1 and c2 are large */
        mpz_mul(mpz_ptr, COEFF_TO_PTR(c1), COEFF_TO_PTR(c2));

    mpz_tdiv_q_2exp(mpz_ptr, mpz_ptr, exp);
    _fmpz_demote_val(f);  /* division may make value small */
}
