blob: 1800df29361532dad6ad12be03d1b35b938fc5e1 (
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
|
/* __gmpfr_int_ceil_log2 -- Integer ceil of log2(x)
Copyright 2004, 2005, 2006 Free Software Foundation, Inc.
This file is part of the MPFR Library.
The 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 2.1 of the License, or (at your
option) any later version.
The 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 MPFR Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
MA 02110-1301, USA. */
#define MPFR_NEED_LONGLONG_H /* for count_leading_zeros */
#include "mpfr-impl.h"
int
__gmpfr_int_ceil_log2 (unsigned long n)
{
if (MPFR_UNLIKELY (n == 1))
return 0;
else
{
int b;
mp_limb_t limb;
MPFR_ASSERTN (n > 1);
limb = n - 1;
MPFR_ASSERTN (limb == n - 1);
count_leading_zeros (b, limb);
return BITS_PER_MP_LIMB - b;
}
}
|
