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Annotation of OpenXM_contrib/gmp/mpfr/uceil_log2.c, Revision 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: }