gcc/gmp/mpf/urandomb.c

/* mpf_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 1999, 2000, 2001, 2002  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 Lesser General Public License as published by
the Free Software Foundation; either version 3 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 Lesser General Public
License for more details.

You should have received a copy of the GNU Lesser General Public License
along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */

#include "gmp.h"
#include "gmp-impl.h"

void
mpf_urandomb (mpf_t rop, gmp_randstate_t rstate, unsigned long int nbits)
{
  mp_ptr rp;
  mp_size_t nlimbs;
  mp_exp_t exp;
  mp_size_t prec;

  rp = PTR (rop);
  nlimbs = BITS_TO_LIMBS (nbits);
  prec = PREC (rop);

  if (nlimbs > prec + 1 || nlimbs == 0)
    {
      nlimbs = prec + 1;
      nbits = nlimbs * GMP_NUMB_BITS;
    }

  _gmp_rand (rp, rstate, nbits);

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

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