blob: aed2269db1b11a0d6e321c696f6fc4f3381c0b01 (
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
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
|
//===-- Standalone implementation of std::optional --------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_LIBC_SRC___SUPPORT_CPP_OPTIONAL_H
#define LLVM_LIBC_SRC___SUPPORT_CPP_OPTIONAL_H
#include "src/__support/CPP/type_traits.h"
#include "src/__support/CPP/utility.h"
#include "src/__support/macros/attributes.h"
#include "src/__support/macros/config.h"
namespace LIBC_NAMESPACE_DECL {
namespace cpp {
// Trivial nullopt_t struct.
struct nullopt_t {
LIBC_INLINE constexpr explicit nullopt_t() = default;
};
// nullopt that can be used and returned.
LIBC_INLINE_VAR constexpr nullopt_t nullopt{};
// This is very simple implementation of the std::optional class. It makes
// several assumptions that the underlying type is trivially constructible,
// copyable, or movable.
template <typename T> class optional {
template <typename U, bool = !is_trivially_destructible<U>::value>
struct OptionalStorage {
union {
char empty;
U stored_value;
};
bool in_use = false;
LIBC_INLINE ~OptionalStorage() { reset(); }
LIBC_INLINE constexpr OptionalStorage() : empty() {}
template <typename... Args>
LIBC_INLINE constexpr explicit OptionalStorage(in_place_t, Args &&...args)
: stored_value(forward<Args>(args)...) {}
LIBC_INLINE constexpr void reset() {
if (in_use)
stored_value.~U();
in_use = false;
}
};
// The only difference is that this type U doesn't have a nontrivial
// destructor.
template <typename U> struct OptionalStorage<U, false> {
union {
char empty;
U stored_value;
};
bool in_use = false;
LIBC_INLINE constexpr OptionalStorage() : empty() {}
template <typename... Args>
LIBC_INLINE constexpr explicit OptionalStorage(in_place_t, Args &&...args)
: stored_value(forward<Args>(args)...) {}
LIBC_INLINE constexpr void reset() { in_use = false; }
};
OptionalStorage<T> storage;
public:
LIBC_INLINE constexpr optional() = default;
LIBC_INLINE constexpr optional(nullopt_t) {}
LIBC_INLINE constexpr optional(const T &t) : storage(in_place, t) {
storage.in_use = true;
}
LIBC_INLINE constexpr optional(const optional &) = default;
LIBC_INLINE constexpr optional(T &&t) : storage(in_place, move(t)) {
storage.in_use = true;
}
LIBC_INLINE constexpr optional(optional &&O) = default;
template <typename... ArgTypes>
LIBC_INLINE constexpr optional(in_place_t, ArgTypes &&...Args)
: storage(in_place, forward<ArgTypes>(Args)...) {
storage.in_use = true;
}
LIBC_INLINE constexpr optional &operator=(T &&t) {
storage = move(t);
return *this;
}
LIBC_INLINE constexpr optional &operator=(optional &&) = default;
LIBC_INLINE constexpr optional &operator=(const T &t) {
storage = t;
return *this;
}
LIBC_INLINE constexpr optional &operator=(const optional &) = default;
LIBC_INLINE constexpr void reset() { storage.reset(); }
LIBC_INLINE constexpr const T &value() const & {
return storage.stored_value;
}
LIBC_INLINE constexpr T &value() & { return storage.stored_value; }
LIBC_INLINE constexpr explicit operator bool() const {
return storage.in_use;
}
LIBC_INLINE constexpr bool has_value() const { return storage.in_use; }
LIBC_INLINE constexpr const T *operator->() const {
return &storage.stored_value;
}
LIBC_INLINE constexpr T *operator->() { return &storage.stored_value; }
LIBC_INLINE constexpr const T &operator*() const & {
return storage.stored_value;
}
LIBC_INLINE constexpr T &operator*() & { return storage.stored_value; }
LIBC_INLINE constexpr T &&value() && { return move(storage.stored_value); }
LIBC_INLINE constexpr T &&operator*() && {
return move(storage.stored_value);
}
};
} // namespace cpp
} // namespace LIBC_NAMESPACE_DECL
#endif // LLVM_LIBC_SRC___SUPPORT_CPP_OPTIONAL_H
|
