mpir/mpn/generic/urandomm.c

/*
Copyright 2009 Jason Moxham

This file is part of the MPIR Library.

The MPIR 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 MPIR 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 MPIR Library; see the file COPYING.LIB.  If not, write
to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA.
*/

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

void mpn_urandomm(mp_ptr rp, gmp_randstate_t rnd, mp_srcptr mp, mp_size_t n)
{
   mp_size_t c, b;

   ASSERT(n > 0);
   ASSERT_MPN(mp, n);
   ASSERT(mp[n - 1] != 0);

   count_leading_zeros(c, mp[n - 1]); /* compute number of bits of n */
   c = GMP_LIMB_BITS - c;
   b = GMP_NUMB_BITS*(n - 1) + c;

   do
   {
      _gmp_rand(rp, rnd, b);
   } while(mpn_cmp(rp, mp, n) >= 0);
return;}