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/* mpfr_random -- generate a random floating-point number
Copyright 1999, 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"
/* Computes a random mpfr in [0, 1[ with precision MPFR_PREC */
void
mpfr_random (mpfr_ptr x)
{
mp_limb_t *xp;
mp_prec_t prec;
mp_size_t xn;
int cnt;
MPFR_CLEAR_FLAGS(x);
xp = MPFR_MANT(x);
prec = MPFR_PREC(x);
xn = (prec - 1) / BITS_PER_MP_LIMB + 1;
mpn_random (xp, xn);
if (xp[xn - 1] == 0)
xp[xn - 1] = 1;
/* since count_leading_zeros doesn't like zeroes, but xp[xn - 1] = 1
will appear twice often. */
count_leading_zeros (cnt, xp[xn - 1]);
if (cnt != 0)
mpn_lshift (xp, xp, xn, cnt);
MPFR_EXP(x) = -cnt;
MPFR_SET_POS(x);
cnt = (mp_prec_t) xn * BITS_PER_MP_LIMB - prec;
/* cnt is the number of non significant bits in the low limb */
xp[0] &= ~((MP_LIMB_T_ONE << cnt) - MP_LIMB_T_ONE);
}
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