pqc/external/flint-2.4.3/fmpz/pow_ui.c
2014-05-24 23:16:06 +02:00

71 lines
2.1 KiB
C

/*=============================================================================
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
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "ulong_extras.h"
#include "fmpz.h"
void
fmpz_pow_ui(fmpz_t f, const fmpz_t g, ulong exp)
{
fmpz c1;
if (exp == WORD(0))
{
fmpz_one(f);
return;
}
c1 = *g;
if (!COEFF_IS_MPZ(c1)) /* g is small */
{
ulong u1 = FLINT_ABS(c1);
ulong bits = FLINT_BIT_COUNT(u1);
if ((bits <= 1) || (exp * bits <= FLINT_BITS - 2))
{
fmpz_set_ui(f, n_pow(u1, exp));
}
else
{
__mpz_struct *mpz_ptr = _fmpz_promote_val(f);
flint_mpz_set_ui(mpz_ptr, u1);
flint_mpz_pow_ui(mpz_ptr, mpz_ptr, exp);
_fmpz_demote_val(f); /* may actually fit into a small after all */
}
if ((c1 < WORD(0)) && (exp & 1)) /* sign is -ve if exp odd and g -ve */
fmpz_neg(f, f);
}
else
{
__mpz_struct *mpz_ptr = _fmpz_promote_val(f);
flint_mpz_pow_ui(mpz_ptr, COEFF_TO_PTR(c1), exp);
/* no need to demote as it can't get smaller */
}
}