blob: bae86087222f356d3021c294c9682be013ffad15 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
|
/* __gmpfr_floor_log2 - returns floor(log(d)/log(2))
Copyright 1999-2004, 2006-2017 Free Software Foundation, Inc.
Contributed by the AriC and Caramba 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 3 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.LESSER. If not, see
http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
#include "mpfr-impl.h"
/* returns floor(log2(d)) */
long
__gmpfr_floor_log2 (double d)
{
#if _GMP_IEEE_FLOATS
union ieee_double_extract x;
x.d = d;
return (long) x.s.exp - 1023;
#else
long exp;
double m;
MPFR_ASSERTD (d >= 0);
if (d >= 1.0)
{
exp = -1;
for( m= 1.0 ; m <= d ; m *=2.0 )
exp++;
}
else
{
exp = 0;
for( m= 1.0 ; m > d ; m *= (1.0/2.0) )
exp--;
}
return exp;
#endif
}
|
