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
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
|
/**
* Copyright (C) 2016 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <type_traits>
#include "mongo/config.h"
#if defined(MONGO_CONFIG_HAVE_STD_ENABLE_IF_T)
namespace mongo {
namespace stdx {
using ::std::enable_if_t;
} // namespace stdx
} // namespace mongo
#else
namespace mongo {
namespace stdx {
template <bool B, class T = void>
using enable_if_t = typename std::enable_if<B, T>::type;
} // namespace stdx
} // namespace mongo
#endif
// TODO: Deal with importing this from C++20, when the time comes.
namespace mongo {
namespace stdx {
template <typename T>
struct type_identity {
using type = T;
};
template <typename T>
using type_identity_t = stdx::type_identity<T>;
} // namespace stdx
} // namespace mongo
// TODO: Re-evaluate which of these we need when making the cutover to C++17.
namespace mongo {
namespace stdx {
namespace detail {
template <typename...>
struct make_void {
using type = void;
};
} // namespace detail
template <typename... Args>
using void_t = typename detail::make_void<Args...>::type;
template <bool b>
using bool_constant = std::integral_constant<bool, b>;
template <typename T>
struct negation : stdx::bool_constant<!bool(T::value)> {};
template <typename... B>
struct disjunction : std::false_type {};
template <typename B>
struct disjunction<B> : B {};
template <typename B1, typename... B>
struct disjunction<B1, B...> : std::conditional_t<bool(B1::value), B1, stdx::disjunction<B...>> {};
template <typename...>
struct conjunction : std::true_type {};
template <typename B>
struct conjunction<B> : B {};
template <typename B1, typename... B>
struct conjunction<B1, B...> : std::conditional_t<bool(B1::value), stdx::conjunction<B...>, B1> {};
namespace detail {
template <typename Func,
typename... Args,
typename = typename std::result_of<Func && (Args && ...)>::type>
auto is_invocable_impl(Func&& func, Args&&... args) -> std::true_type;
auto is_invocable_impl(...) -> std::false_type;
} // namespace detail
template <typename Func, typename... Args>
struct is_invocable
: decltype(detail::is_invocable_impl(std::declval<Func>(), std::declval<Args>()...)) {};
namespace detail {
// This helps solve the lack of regular void problem, when passing a 'conversion target' as a
// parameter.
template <typename R,
typename Func,
typename... Args,
typename ComputedResult = typename std::result_of<Func && (Args && ...)>::type>
auto is_invocable_r_impl(stdx::type_identity<R>, Func&& func, Args&&... args) ->
typename stdx::disjunction<std::is_void<R>,
std::is_same<ComputedResult, R>,
std::is_convertible<ComputedResult, R>>::type;
auto is_invocable_r_impl(...) -> std::false_type;
} // namespace detail
template <typename R, typename Func, typename... Args>
struct is_invocable_r
: decltype(detail::is_invocable_r_impl(
stdx::type_identity<R>(), std::declval<Func>(), std::declval<Args>()...)) {};
} // namespace stdx
} // namespace mongo
|