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/* mpfr_set_z -- set a floating-point number from a multiple-precision 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 "longlong.h"
#include "mpfr.h"
#include "mpfr-impl.h"
/* set f to the integer z */
int
mpfr_set_z (mpfr_ptr f, mpz_srcptr z, mp_rnd_t rnd_mode)
{
mp_size_t fn, zn, dif;
int k, sign_z, inex;
mp_limb_t *fp, *zp;
mp_exp_t exp;
MPFR_CLEAR_FLAGS (f); /* z cannot be NaN nor Inf */
sign_z = mpz_cmp_ui (z, 0);
if (sign_z == 0)
{
MPFR_SET_ZERO(f);
MPFR_SET_POS(f);
MPFR_RET(0);
}
fp = MPFR_MANT(f);
fn = 1 + (MPFR_PREC(f) - 1) / BITS_PER_MP_LIMB;
zn = ABS(SIZ(z));
MPFR_ASSERTN(zn >= 1);
dif = zn - fn;
zp = PTR(z);
count_leading_zeros(k, zp[zn-1]);
if (zn > MPFR_EMAX_MAX / BITS_PER_MP_LIMB + 1)
return mpfr_set_overflow(f, rnd_mode, sign_z);
/* because zn >= __mpfr_emax / BITS_PER_MP_LIMB + 2
and zn * BITS_PER_MP_LIMB >= __mpfr_emax + BITS_PER_MP_LIMB + 1
and exp = zn * BITS_PER_MP_LIMB - k > __mpfr_emax */
/* now zn <= MPFR_EMAX_MAX / BITS_PER_MP_LIMB + 1
thus zn * BITS_PER_MP_LIMB <= MPFR_EMAX_MAX + BITS_PER_MP_LIMB
and exp = zn * BITS_PER_MP_LIMB - k
<= MPFR_EMAX_MAX + BITS_PER_MP_LIMB */
exp = (mp_prec_t) zn * BITS_PER_MP_LIMB - k;
/* The exponent will be exp or exp + 1 (due to rounding) */
if (exp > __mpfr_emax)
return mpfr_set_overflow(f, rnd_mode, sign_z);
if (exp + 1 < __mpfr_emin)
return mpfr_set_underflow(f, rnd_mode == GMP_RNDN ? GMP_RNDZ : rnd_mode,
sign_z);
if (MPFR_SIGN(f) * sign_z < 0)
MPFR_CHANGE_SIGN(f);
if (dif >= 0)
{
mp_limb_t cc;
int sh, to0;
/* number has to be truncated */
if (k != 0)
{
mpn_lshift(fp, zp + dif, fn, k);
if (dif != 0)
fp[0] += zp[dif - 1] >> (BITS_PER_MP_LIMB - k);
}
else
MPN_COPY(fp, zp + dif, fn);
sh = (mp_prec_t) fn * BITS_PER_MP_LIMB - MPFR_PREC(f);
cc = fp[0] & ((MP_LIMB_T_ONE << sh) - 1);
fp[0] &= ~cc;
to0 = rnd_mode == GMP_RNDZ
|| (rnd_mode == GMP_RNDU && sign_z < 0)
|| (rnd_mode == GMP_RNDD && sign_z > 0);
/* remaining bits... */
if (rnd_mode == GMP_RNDN)
{
/* 1) If rounding bit is 0, behave like rounding to 0.
2) Determine the sticky bit (cc != 0). */
if (sh != 0)
{
mp_limb_t rb;
rb = MP_LIMB_T_ONE << (sh - 1);
if ((cc & rb) == 0)
to0 = 1; /* rounding bit is 0 */
else
cc &= ~rb;
if (cc == 0 && dif > 0)
cc = zp[--dif] << k;
}
else /* sh == 0 */
{
MPFR_ASSERTN(cc == 0);
if (dif > 0)
cc = zp[--dif] << k;
if ((cc & MPFR_LIMB_HIGHBIT) == 0)
to0 = 1; /* rounding bit is 0 */
else
cc <<= 1;
}
while (cc == 0 && dif > 0)
cc = zp[--dif];
if (!to0 && cc == 0) /* even rounding */
{
cc = 1;
if ((fp[0] & (MP_LIMB_T_ONE << sh)) == 0)
to0 = 1;
}
} /* rnd_mode == GMP_RNDN */
else if (cc == 0 && dif > 0)
{
cc = zp[--dif] << k;
while (cc == 0 && dif > 0)
cc = zp[--dif];
}
if (cc == 0)
inex = 0;
else if (to0)
inex = -sign_z;
else
{
if (mpn_add_1(fp, fp, fn, MP_LIMB_T_ONE << sh))
{
if (exp == __mpfr_emax)
return mpfr_set_overflow(f, rnd_mode, sign_z);
else
{
exp++;
fp[fn-1] = MPFR_LIMB_HIGHBIT;
}
}
inex = sign_z;
}
} /* dif >= 0 */
else /* dif < 0 */
{
if (k != 0)
mpn_lshift(fp - dif, zp, zn, k);
else
MPN_COPY(fp - dif, zp, zn);
/* fill with zeroes */
MPN_ZERO(fp, -dif);
inex = 0; /* result is exact */
}
if (exp < __mpfr_emin)
{
if (rnd_mode == GMP_RNDN && inex == 0 && mpfr_powerof2_raw (f))
rnd_mode = GMP_RNDZ;
return mpfr_set_underflow(f, rnd_mode, sign_z);
}
MPFR_EXP(f) = exp;
MPFR_RET(inex);
}
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