Seastar
High performance C++ framework for concurrent servers
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bitops.hh
1/*
2 * This file is open source software, licensed to you under the terms
3 * of the Apache License, Version 2.0 (the "License"). See the NOTICE file
4 * distributed with this work for additional information regarding copyright
5 * ownership. You may not use this file except in compliance with the License.
6 *
7 * You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing,
12 * software distributed under the License is distributed on an
13 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
14 * KIND, either express or implied. See the License for the
15 * specific language governing permissions and limitations
16 * under the License.
17 */
18/*
19 * Copyright (C) 2014 Cloudius Systems, Ltd.
20 */
21
22#pragma once
23
24#include <seastar/util/modules.hh>
25#ifndef SEASTAR_MODULE
26#include <concepts>
27#include <limits>
28#endif
29
30namespace seastar {
31
32SEASTAR_MODULE_EXPORT_BEGIN
33
34inline
35constexpr unsigned count_leading_zeros(unsigned x) {
36 return __builtin_clz(x);
37}
38
39inline
40constexpr unsigned count_leading_zeros(unsigned long x) {
41 return __builtin_clzl(x);
42}
43
44inline
45constexpr unsigned count_leading_zeros(unsigned long long x) {
46 return __builtin_clzll(x);
47}
48
49inline
50constexpr unsigned count_trailing_zeros(unsigned x) {
51 return __builtin_ctz(x);
52}
53
54inline
55constexpr unsigned count_trailing_zeros(unsigned long x) {
56 return __builtin_ctzl(x);
57}
58
59inline
60constexpr unsigned count_trailing_zeros(unsigned long long x) {
61 return __builtin_ctzll(x);
62}
63
64template<std::integral T>
65inline constexpr unsigned log2ceil(T n) {
66 if (n == 1) {
67 return 0;
68 }
69 return std::numeric_limits<T>::digits - count_leading_zeros(n - 1);
70}
71
72template<std::integral T>
73inline constexpr unsigned log2floor(T n) {
74 return std::numeric_limits<T>::digits - count_leading_zeros(n) - 1;
75}
76
77SEASTAR_MODULE_EXPORT_END
78
79}
Seastar API namespace.
Definition: abort_on_ebadf.hh:26