1/* __gmpfr_int_ceil_log2 -- Integer ceil of log2(x) 2 3Copyright 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc. 4Contributed by the AriC and Caramel projects, INRIA. 5 6This file is part of the GNU MPFR Library. 7 8The GNU MPFR Library is free software; you can redistribute it and/or modify 9it under the terms of the GNU Lesser General Public License as published by 10the Free Software Foundation; either version 3 of the License, or (at your 11option) any later version. 12 13The GNU MPFR Library is distributed in the hope that it will be useful, but 14WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 15or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 16License for more details. 17 18You should have received a copy of the GNU Lesser General Public License 19along with the GNU MPFR Library; see the file COPYING.LESSER. If not, see 20http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc., 2151 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */ 22 23#define MPFR_NEED_LONGLONG_H /* for count_leading_zeros */ 24#include "mpfr-impl.h" 25 26int 27__gmpfr_int_ceil_log2 (unsigned long n) 28{ 29 if (MPFR_UNLIKELY (n == 1)) 30 return 0; 31 else 32 { 33 int b; 34 mp_limb_t limb; 35 36 MPFR_ASSERTN (n > 1); 37 limb = n - 1; 38 MPFR_ASSERTN (limb == n - 1); 39 count_leading_zeros (b, limb); 40 return GMP_NUMB_BITS - b; 41 } 42} 43