contrib/mpc/src/uceil_log2.c

   1 /* mpc_ceil_log2 - returns ceil(log(d)/log(2))
   2
   3 Copyright (C) 2004, 2009, 2010 INRIA
   4
   5 This file is part of GNU MPC.
   6
   7 GNU MPC is free software; you can redistribute it and/or modify it under
   8 the terms of the GNU Lesser General Public License as published by the
   9 Free Software Foundation; either version 3 of the License, or (at your
  10 option) any later version.
  11
  12 GNU MPC is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  14 FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
  15 more details.
  16
  17 You should have received a copy of the GNU Lesser General Public License
  18 along with this program. If not, see http://www.gnu.org/licenses/ .
  19 */
  20
  21 #include "mpc-impl.h"
  22
  23 /* returns ceil(log(d)/log(2)) if d > 0 */
  24 /* Don't use count_leading_zeros since it is in longlong.h */
  25 mpfr_prec_t
  26 mpc_ceil_log2 (mpfr_prec_t d)
  27 {
  28   mpfr_prec_t exp;
  29
  30   for (exp = 0; d > 1; d = (d + 1) / 2)
  31     exp++;
  32   return exp;
  33 }