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Annotation of OpenXM_contrib/gmp/mpfr/uceil_log2.c, Revision 1.1.1.1

1.1       ohara       1: /* _mpfr_ceil_log2 - returns ceil(log(d)/log(2))
                      2:
                      3: Copyright 1999, 2000, 2001, 2002 Free Software Foundation.
                      4:
                      5: This file is part of the MPFR Library.
                      6:
                      7: The MPFR Library is free software; you can redistribute it and/or modify
                      8: it under the terms of the GNU Lesser General Public License as published by
                      9: the Free Software Foundation; either version 2.1 of the License, or (at your
                     10: option) any later version.
                     11:
                     12: The MPFR Library is distributed in the hope that it will be useful, but
                     13: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
                     14: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
                     15: License for more details.
                     16:
                     17: You should have received a copy of the GNU Lesser General Public License
                     18: along with the MPFR Library; see the file COPYING.LIB.  If not, write to
                     19: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
                     20: MA 02111-1307, USA. */
                     21:
                     22: #include "gmp.h"
                     23: #include "gmp-impl.h"
                     24: #include "mpfr.h"
                     25: #include "mpfr-impl.h"
                     26:
                     27: /* returns ceil(log(d)/log(2)) */
                     28: long
                     29: _mpfr_ceil_log2 (double d)
                     30: {
                     31:   long exp;
                     32:   union ieee_double_extract x;
                     33:
                     34:   x.d = d;
                     35:   exp = x.s.exp - 1023;
                     36:   x.s.exp = 1023; /* value for 1 <= d < 2 */
                     37:   if (x.d != 1.0) /* d: not a power of two? */
                     38:     exp++;
                     39:   return exp;
                     40: }