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/* __gmpfr_int_ceil_log2 -- Integer ceil of log2(x)
Copyright 2004-2020 Free Software Foundation, Inc.
Contributed by the AriC and Caramba projects, INRIA.
This file is part of the GNU MPFR Library.
The GNU 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 3 of the License, or (at your
option) any later version.
The GNU 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 GNU MPFR Library; see the file COPYING.LESSER. If not, see
https://www.gnu.org/licenses/ or 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
#ifdef MPFR_LONG_WITHIN_LIMB
{
int b;
mp_limb_t limb;
MPFR_ASSERTN (n > 1);
limb = n - 1;
MPFR_ASSERTN (limb == n - 1);
count_leading_zeros (b, limb);
b = GMP_NUMB_BITS - b;
MPFR_ASSERTD (b >= 0);
return b;
}
#else
return mpfr_nbits_ulong (n - 1);
#endif
}
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