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/* mpfr_odd_p -- check for odd integers
Copyright 2001-2020 Free Software Foundation, Inc.
Contributed by the AriC and Caramba projects, INRIA.
This file is part of the GNU MPFR Library.
The GNU MPFR Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 3 of the License, or (at your
option) any later version.
The GNU MPFR Library 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 Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with the GNU MPFR Library; see the file COPYING.LESSER. If not, see
https://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
#define MPFR_NEED_LONGLONG_H
#include "mpfr-impl.h"
/* Return 1 if y is an odd integer, 0 otherwise.
Assumes y is not singular. */
int
mpfr_odd_p (mpfr_srcptr y)
{
mpfr_exp_t expo;
mpfr_prec_t prec;
mp_size_t yn;
mp_limb_t *yp;
/* NAN, INF or ZERO are not allowed */
MPFR_ASSERTD (!MPFR_IS_SINGULAR (y));
expo = MPFR_GET_EXP (y);
if (expo <= 0)
return 0; /* |y| < 1 and not 0 */
prec = MPFR_PREC(y);
if ((mpfr_prec_t) expo > prec)
return 0; /* y is a multiple of 2^(expo-prec), thus not odd */
/* 0 < expo <= prec:
y = 1xxxxxxxxxt.zzzzzzzzzzzzzzzzzz[000]
expo bits (prec-expo) bits
We have to check that:
(a) the bit 't' is set
(b) all the 'z' bits are zero
*/
prec = MPFR_PREC2LIMBS (prec) * GMP_NUMB_BITS - expo;
/* number of z+0 bits */
yn = prec / GMP_NUMB_BITS;
MPFR_ASSERTN(yn >= 0);
/* yn is the index of limb containing the 't' bit */
yp = MPFR_MANT(y);
/* if expo is a multiple of GMP_NUMB_BITS, t is bit 0 */
if (expo % GMP_NUMB_BITS == 0 ? (yp[yn] & 1) == 0
: MPFR_LIMB_LSHIFT(yp[yn], (expo % GMP_NUMB_BITS) - 1) != MPFR_LIMB_HIGHBIT)
return 0;
while (--yn >= 0)
if (yp[yn] != 0)
return 0;
return 1;
}
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