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/* __gmpfr_int_ceil_log2 -- Integer ceil of log2(x)

Copyright 2004, 2005, 2006 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., 51 Franklin St, Fifth Floor, Boston,
MA 02110-1301, USA. */

#define MPFR_NEED_LONGLONG_H /* for count_leading_zeros */
#include "mpfr-impl.h"

int
__gmpfr_int_ceil_log2 (unsigned long n)
{
  if (MPFR_UNLIKELY (n == 1))
    return 0;
  else
    {
      int b;
      mp_limb_t limb;

      MPFR_ASSERTN (n > 1);
      limb = n - 1;
      MPFR_ASSERTN (limb == n - 1);
      count_leading_zeros (b, limb);
      return BITS_PER_MP_LIMB - b;
    }
}