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/* mpfr_rint -- Round to an integer.
Copyright 1999, 2000, 2001, 2002 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 "gmp.h"
#include "gmp-impl.h"
#include "mpfr.h"
#include "mpfr-impl.h"
int
mpfr_rint (mpfr_ptr r, mpfr_srcptr u, mp_rnd_t rnd_mode)
{
int sign;
mp_exp_t exp;
if (MPFR_IS_NAN(u))
{
MPFR_SET_NAN(r);
MPFR_RET_NAN;
}
MPFR_CLEAR_NAN(r);
MPFR_SET_SAME_SIGN(r, u);
if (MPFR_IS_INF(u))
{
MPFR_SET_INF(r);
MPFR_RET(0); /* infinity is exact */
}
MPFR_CLEAR_INF(r);
if (MPFR_IS_ZERO(u))
{
MPFR_SET_ZERO(r);
MPFR_RET(0); /* zero is exact */
}
sign = MPFR_SIGN(u);
exp = MPFR_EXP(u);
/* Single out the case where |u| < 1. */
if (exp <= 0) /* 0 < |u| < 1 */
{
if ((rnd_mode == GMP_RNDD && sign < 0) ||
(rnd_mode == GMP_RNDU && sign > 0) ||
(rnd_mode == GMP_RNDN && exp == 0))
{
mp_limb_t *rp;
mp_size_t rm;
rp = MPFR_MANT(r);
rm = (MPFR_PREC(r) - 1) / BITS_PER_MP_LIMB;
rp[rm] = GMP_LIMB_HIGHBIT;
MPN_ZERO(rp, rm);
MPFR_EXP(r) = 1; /* |r| = 1 */
MPFR_RET(sign > 0 ? 2 : -2);
}
else
{
MPFR_SET_ZERO(r); /* r = 0 */
MPFR_RET(sign > 0 ? -2 : 2);
}
}
else /* exp > 0, |u| >= 1 */
{
mp_limb_t *up, *rp;
mp_size_t un, rn, ui;
int sh, idiff;
int uflags;
/*
* uflags will contain:
* _ 0 if u is an integer representable in r,
* _ 1 if u is an integer not representable in r,
* _ 2 if u is not an integer.
*/
up = MPFR_MANT(u);
rp = MPFR_MANT(r);
un = MPFR_ESIZE(u);
rn = MPFR_ESIZE(r);
sh = rn * BITS_PER_MP_LIMB - MPFR_PREC(r);
MPFR_EXP(r) = exp;
if ((exp - 1) / BITS_PER_MP_LIMB >= un)
{
ui = un;
idiff = 0;
uflags = 0; /* u is an integer */
}
else
{
mp_size_t uj;
ui = (exp - 1) / BITS_PER_MP_LIMB + 1; /* #limbs of the int part */
uj = un - ui; /* lowest limb of the integer part */
idiff = exp % BITS_PER_MP_LIMB; /* #int-part bits in up[uj] or 0 */
uflags = idiff == 0 || (up[uj] << idiff) == 0 ? 0 : 2;
if (uflags == 0)
while (uj > 0)
if (up[--uj] != 0)
{
uflags = 2;
break;
}
}
if (ui > rn)
{
MPFR_ASSERTN(rp != up && un > rn);
MPN_COPY(rp, up + (un - rn), rn);
/* In the rounding to the nearest mode, if the rounding bit
is 0, change the rounding mode to GMP_RNDZ. */
if (rnd_mode == GMP_RNDN &&
((sh != 0 && (rp[0] & (MP_LIMB_T_ONE << (sh - 1))) == 0) ||
(sh == 0 && (up[un - rn - 1] & GMP_LIMB_HIGHBIT) == 0)))
rnd_mode = GMP_RNDZ;
if (uflags == 0)
{ /* u is an integer; determine if it is representable */
if (sh != 0 && rp[0] << (BITS_PER_MP_LIMB - sh) != 0)
uflags = 1; /* u is not representable in r */
else
{
mp_size_t i;
for (i = un - rn - 1; i >= 0; i--)
if (up[i] != 0)
{
uflags = 1; /* u is not representable in r */
break;
}
}
}
if (sh != 0)
rp[0] &= MP_LIMB_T_MAX << sh;
}
else
{
mp_size_t uj, rj;
int ush;
uj = un - ui; /* lowest limb of the integer part in u */
rj = rn - ui; /* lowest limb of the integer part in r */
MPN_ZERO(rp, rj);
if (rp != up)
MPN_COPY(rp + rj, up + uj, ui);
rp += rj;
rn = ui;
ush = idiff == 0 ? 0 : BITS_PER_MP_LIMB - idiff;
if (rj == 0 && ush < sh)
{
/* In the rounding to the nearest mode, if the rounding bit
is 0, change the rounding mode to GMP_RNDZ. */
if (rnd_mode == GMP_RNDN &&
(rp[0] & (MP_LIMB_T_ONE << (sh - 1))) == 0)
rnd_mode = GMP_RNDZ; /* rounding bit is 0 */
if (uflags == 0)
{ /* u is an integer; determine if it is representable */
mp_limb_t mask;
mask = (MP_LIMB_T_ONE << sh) - (MP_LIMB_T_ONE << ush);
if ((rp[0] & mask) != 0)
uflags = 1; /* u is not representable in r */
}
}
else
{
sh = ush;
if (rnd_mode == GMP_RNDN &&
((ush != 0 &&
(up[uj] & (MP_LIMB_T_ONE << (ush - 1))) == 0) ||
(ush == 0 &&
(uj == 0 || (up[uj - 1] & GMP_LIMB_HIGHBIT) == 0))))
rnd_mode = GMP_RNDZ; /* rounding bit is 0 */
}
if (sh != 0)
rp[0] &= MP_LIMB_T_MAX << sh;
}
if (uflags == 0)
MPFR_RET(0);
/* Note: if rnd_mode == GMP_RNDN, then round away from 0 (if
the rounding bit was 0 and rnd_mode == GMP_RNDN, rnd_mode
has been changed to GMP_RNDZ). */
if ((rnd_mode == GMP_RNDN ||
(rnd_mode == GMP_RNDD && sign < 0) ||
(rnd_mode == GMP_RNDU && sign > 0))
&& mpn_add_1(rp, rp, rn, MP_LIMB_T_ONE << sh))
{
if (exp == __mpfr_emax)
return mpfr_set_overflow(r, rnd_mode, MPFR_SIGN(r)) >= 0 ?
uflags : -uflags;
else
{
MPFR_EXP(r)++;
rp[rn-1] = GMP_LIMB_HIGHBIT;
}
}
MPFR_RET(rnd_mode == GMP_RNDU ||
(rnd_mode == GMP_RNDZ && sign < 0) ||
(rnd_mode == GMP_RNDN && sign > 0) ? uflags : -uflags);
} /* exp > 0, |u| >= 1 */
}
#undef mpfr_round
int
mpfr_round (mpfr_ptr r, mpfr_srcptr u)
{
return mpfr_rint(r, u, GMP_RNDN);
}
#undef mpfr_trunc
int
mpfr_trunc (mpfr_ptr r, mpfr_srcptr u)
{
return mpfr_rint(r, u, GMP_RNDZ);
}
#undef mpfr_ceil
int
mpfr_ceil (mpfr_ptr r, mpfr_srcptr u)
{
return mpfr_rint(r, u, GMP_RNDU);
}
#undef mpfr_floor
int
mpfr_floor (mpfr_ptr r, mpfr_srcptr u)
{
return mpfr_rint(r, u, GMP_RNDD);
}
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