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/* mpfr_urandomb (rop, state, nbits) -- Generate a uniform pseudorandom
real number between 0 (inclusive) and 1 (exclusive) of size NBITS,
using STATE as the random state previously initialized by a call to
gmp_randinit().
Copyright 2000, 2001, 2002, 2003 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"
int
mpfr_urandomb (mpfr_ptr rop, gmp_randstate_t rstate)
{
mp_ptr rp;
mp_prec_t nbits;
mp_size_t nlimbs;
mp_size_t k; /* number of high zero limbs */
mp_exp_t exp;
int cnt;
MPFR_CLEAR_FLAGS(rop);
rp = MPFR_MANT(rop);
nbits = MPFR_PREC(rop);
nlimbs = MPFR_LIMB_SIZE(rop);
/*(nbits + BITS_PER_MP_LIMB - 1) / BITS_PER_MP_LIMB;*/
_gmp_rand (rp, rstate, nlimbs * BITS_PER_MP_LIMB);
/* If nbits isn't a multiple of BITS_PER_MP_LIMB, mask the low bits */
cnt = nlimbs * BITS_PER_MP_LIMB - nbits;
if (cnt != 0)
rp[0] &= ~((MP_LIMB_T_ONE << cnt) - MP_LIMB_T_ONE);
exp = 0;
k = 0;
while (nlimbs != 0 && rp[nlimbs - 1] == 0)
{
k ++;
nlimbs --;
exp -= BITS_PER_MP_LIMB;
}
if (nlimbs != 0) /* otherwise value is zero */
{
count_leading_zeros (cnt, rp[nlimbs - 1]);
if (mpfr_set_exp (rop, exp - cnt))
{
MPFR_SET_NAN (rop);
__gmpfr_flags |= MPFR_FLAGS_NAN;
return 1;
}
if (cnt != 0)
mpn_lshift (rp + k, rp, nlimbs, cnt);
if (k)
MPN_ZERO (rp, k);
}
else
MPFR_SET_ZERO(rop);
MPFR_SET_POS (rop);
return 0;
}
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