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/* mpfr_add_one_ulp -- add one unit in last place
Copyright 1999, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
This file is part of the MPFR Library.
The 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 2.1 of the License, or (at your
option) any later version.
The 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 MPFR Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */
#include "mpfr-impl.h"
/* sets x to x+sign(x)*ulp(x) */
int
mpfr_add_one_ulp (mpfr_ptr x, mp_rnd_t rnd_mode)
{
mp_size_t xn;
int sh;
mp_limb_t *xp;
if (MPFR_UNLIKELY( MPFR_IS_SINGULAR(x) ))
{
if (MPFR_IS_NAN(x))
MPFR_RET_NAN;
MPFR_ASSERTD (MPFR_IS_INF(x) || MPFR_IS_ZERO(x));
MPFR_RET(0);
}
xn = MPFR_LIMB_SIZE(x);
MPFR_UNSIGNED_MINUS_MODULO(sh, MPFR_PREC(x) );
xp = MPFR_MANT(x);
if (mpn_add_1 (xp, xp, xn, MPFR_LIMB_ONE << sh)) /* got 1.0000... */
{
mp_exp_t exp = MPFR_EXP (x);
if (MPFR_UNLIKELY(exp == __gmpfr_emax))
return mpfr_set_overflow(x, rnd_mode, MPFR_SIGN(x));
else
{
MPFR_ASSERTD (exp < __gmpfr_emax);
MPFR_SET_EXP (x, exp + 1);
/* The mantissa is already filled with 0 */
xp[xn-1] = MPFR_LIMB_HIGHBIT;
}
}
MPFR_RET(0);
}
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