/* 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 (C) 1999, 2000  Free Software Foundation, Inc.

This file is part of the GNU MP Library.

The GNU MP 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 GNU MP 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 GNU MP 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"

void
#if __STDC__
mpfr_urandomb (mpfr_t rop, gmp_randstate_t rstate)
#else
mpfr_urandomb (rop, rstate)
     mpfr_t rop;
     gmp_randstate_t rstate;
#endif
{
  mp_ptr rp;
  mp_size_t nlimbs;
  mp_exp_t exp;
  unsigned long cnt, nbits; 

  rp = MANT(rop);
  nbits = PREC(rop);
  nlimbs = (nbits + BITS_PER_MP_LIMB - 1) / BITS_PER_MP_LIMB;

  _gmp_rand (rp, rstate, nbits);

  /* If nbits isn't a multiple of BITS_PER_MP_LIMB, shift up.  */
  if (nlimbs != 0)
    {
      if (nbits % BITS_PER_MP_LIMB != 0)
	mpn_lshift (rp, rp, nlimbs,
		    BITS_PER_MP_LIMB - nbits % BITS_PER_MP_LIMB);
    }

  exp = 0;
  while (nlimbs != 0 && rp[nlimbs - 1] == 0)
    {
      nlimbs--;
      exp--;
    }

  count_leading_zeros(cnt, rp[nlimbs - 1]); 
  if (cnt) mpn_lshift(rp, rp, nlimbs, cnt); 
  exp -= cnt; 

  cnt = nlimbs*BITS_PER_MP_LIMB - nbits; 
  /* cnt is the number of non significant bits in the low limb */
  rp[0] &= ~((((mp_limb_t)1)<<cnt) - 1);

  EXP (rop) = exp;
}