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/* mpfr_mul_ui -- multiply a floating-point number by a machine integer
Copyright (C) 1999, 2001 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 Library General Public License as published by
the Free Software Foundation; either version 2 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 Library General Public
License for more details.
You should have received a copy of the GNU Library 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 <stdio.h>
#include "gmp.h"
#include "gmp-impl.h"
#include "longlong.h"
#include "mpfr.h"
#include "mpfr-impl.h"
int
mpfr_mul_ui (mpfr_ptr y, mpfr_srcptr x, unsigned long int u, mp_rnd_t rnd_mode)
{
mp_limb_t *my, *old_my;
unsigned long xn, yn, cnt, c;
int inexact;
TMP_DECL(marker);
if (MPFR_IS_NAN(x))
{
MPFR_CLEAR_FLAGS(y);
MPFR_SET_NAN(y);
return 1; /* a NaN is always inexact */
}
if (MPFR_IS_INF(x))
{
MPFR_CLEAR_FLAGS(y);
if (u)
{
MPFR_SET_INF(y);
if (MPFR_SIGN(y) != MPFR_SIGN(x))
MPFR_CHANGE_SIGN(y);
return 0; /* infinity is exact */
}
else /* 0 * infinity */
{
MPFR_SET_NAN(y);
return 1; /* NaN is inexact */
}
}
if (MPFR_IS_ZERO(x) || !u)
{
MPFR_CLEAR_FLAGS(y);
MPFR_SET_ZERO(y);
return 0; /* zero is exact */
}
MPFR_CLEAR_FLAGS(y);
if (u == 1)
return mpfr_set (y, x, rnd_mode);
TMP_MARK(marker);
my = MPFR_MANT(y);
yn = (MPFR_PREC(y) - 1) / BITS_PER_MP_LIMB + 1;
xn = (MPFR_PREC(x) - 1) / BITS_PER_MP_LIMB + 1;
old_my = my;
if (yn < xn + 1)
my = (mp_ptr) TMP_ALLOC ((xn + 1) * BYTES_PER_MP_LIMB);
my[xn] = mpn_mul_1 (my, MPFR_MANT(x), xn, u);
/* x * u is stored in my[xn], ..., my[0] */
/* since the case u=1 was treated above, we have u >= 2, thus
my[xn] >= 1 since x was msb-normalized */
ASSERT_ALWAYS(my[xn] != 0);
count_leading_zeros(cnt, my[xn]);
mpn_lshift (my, my, xn + 1, cnt);
/* now my[xn], ..., my[0] is msb-normalized too, and has at most
PREC(x) + (BITS_PER_MP_LIMB - cnt) non-zero bits */
c = mpfr_round_raw (old_my, my, (xn + 1) * BITS_PER_MP_LIMB,
(MPFR_SIGN(x) < 0), MPFR_PREC(y), rnd_mode, &inexact);
MPFR_EXP(y) = MPFR_EXP(x) + BITS_PER_MP_LIMB - cnt;
if (c) /* rounded result is 1.0000000000000000... */
{
old_my[yn-1] = MP_LIMB_T_HIGHBIT;
MPFR_EXP(y) ++;
}
/* set sign */
if (MPFR_SIGN(y) * MPFR_SIGN(x) < 0)
MPFR_CHANGE_SIGN(y);
TMP_FREE(marker);
return inexact;
}
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