1 /* mpfr_nbits_ulong -- number of significant bits in an unsigned long
2 mpfr_nbits_uj -- number of significant bits in an uintmax_t
3
4 Copyright 2018-2023 Free Software Foundation, Inc.
5 Contributed by the AriC and Caramba projects, INRIA.
6
7 This file is part of the GNU MPFR Library.
8
9 The GNU MPFR Library is free software; you can redistribute it and/or modify
10 it under the terms of the GNU Lesser General Public License as published by
11 the Free Software Foundation; either version 3 of the License, or (at your
12 option) any later version.
13
14 The GNU MPFR Library is distributed in the hope that it will be useful, but
15 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
16 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
17 License for more details.
18
19 You should have received a copy of the GNU Lesser General Public License
20 along with the GNU MPFR Library; see the file COPYING.LESSER. If not, see
21 https://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
22 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
23
24 #define MPFR_NEED_LONGLONG_H /* for count_leading_zeros */
25 #define MPFR_NEED_INTMAX_H
26 #include "mpfr-impl.h"
27
28 /* count the number of significant bits of n, i.e.,
29 nbits(unsigned long) - count_leading_zeros (n) */
30 int
mpfr_nbits_ulong(unsigned long n)31 mpfr_nbits_ulong (unsigned long n)
32 {
33 int cnt;
34
35 MPFR_ASSERTD (n > 0);
36
37 #ifdef MPFR_LONG_WITHIN_LIMB
38
39 count_leading_zeros (cnt, (mp_limb_t) n);
40 cnt = GMP_NUMB_BITS - cnt;
41
42 #else
43
44 cnt = 0;
45
46 while (n >= 0x10000)
47 {
48 n >>= 16;
49 cnt += 16;
50 }
51
52 MPFR_ASSERTD (n <= 0xffff);
53
54 if (n >= 0x100)
55 {
56 n >>= 8;
57 cnt += 8;
58 }
59
60 MPFR_ASSERTD (n <= 0xff);
61
62 if (n >= 0x10)
63 {
64 n >>= 4;
65 cnt += 4;
66 }
67
68 MPFR_ASSERTD (n <= 0xf);
69
70 if (n >= 4)
71 {
72 n >>= 2;
73 cnt += 2;
74 }
75
76 MPFR_ASSERTD (n <= 3);
77
78 /* now n = 1, 2, or 3 */
79 cnt += 1 + (n >= 2);
80
81 #endif
82
83 MPFR_ASSERTD (cnt >= 0);
84 return cnt;
85 }
86
87 #ifdef _MPFR_H_HAVE_INTMAX_T
88 /* count the number of significant bits of n, i.e.,
89 nbits(uintmax_t) - count_leading_zeros (n) */
90 int
mpfr_nbits_uj(uintmax_t n)91 mpfr_nbits_uj (uintmax_t n)
92 {
93 int cnt;
94
95 MPFR_ASSERTD (n > 0);
96
97 cnt = 0;
98
99 while (n >= 0x10000)
100 {
101 n >>= 16;
102 cnt += 16;
103 }
104
105 MPFR_ASSERTD (n <= 0xffff);
106
107 if (n >= 0x100)
108 {
109 n >>= 8;
110 cnt += 8;
111 }
112
113 MPFR_ASSERTD (n <= 0xff);
114
115 if (n >= 0x10)
116 {
117 n >>= 4;
118 cnt += 4;
119 }
120
121 MPFR_ASSERTD (n <= 0xf);
122
123 if (n >= 4)
124 {
125 n >>= 2;
126 cnt += 2;
127 }
128
129 MPFR_ASSERTD (n <= 3);
130
131 /* now n = 1, 2, or 3 */
132 cnt += 1 + (n >= 2);
133
134 MPFR_ASSERTD (cnt >= 0);
135 return cnt;
136 }
137 #endif
138