| /* __gmpfr_int_ceil_log2 -- Integer ceil of log2(x) |
| |
| Copyright 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc. |
| Contributed by the Arenaire and Cacao 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 2.1 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.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; |
| } |
| } |